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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC5578' is defined on line 3112, but no explicit reference was found in the text ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) -- Obsolete informational reference (is this intentional?): RFC 7525 (Obsoleted by RFC 9325) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Mobile Ad hoc Networks Working Group S. Ratliff 3 Internet-Draft VT iDirect 4 Intended status: Standards Track S. Jury 5 Expires: July 28, 2017 Cisco Systems 6 D. Satterwhite 7 Broadcom 8 R. Taylor 9 Airbus Defence & Space 10 B. Berry 11 January 24, 2017 13 Dynamic Link Exchange Protocol (DLEP) 14 draft-ietf-manet-dlep-27 16 Abstract 18 When routing devices rely on modems to effect communications over 19 wireless links, they need timely and accurate knowledge of the 20 characteristics of the link (speed, state, etc.) in order to make 21 routing decisions. In mobile or other environments where these 22 characteristics change frequently, manual configurations or the 23 inference of state through routing or transport protocols does not 24 allow the router to make the best decisions. DLEP describes a new 25 protocol for a bidirectional, event-driven communication channel 26 between the router and the modem to facilitate communication of 27 changing link characteristics. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on July 28, 2017. 46 Copyright Notice 48 Copyright (c) 2017 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 64 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 65 2.1. Destinations . . . . . . . . . . . . . . . . . . . . . . 8 66 2.2. Conventions and Terminology . . . . . . . . . . . . . . . 9 67 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9 68 4. Implementation Scenarios . . . . . . . . . . . . . . . . . . 9 69 5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 10 70 6. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 7. DLEP Session Flow . . . . . . . . . . . . . . . . . . . . . . 12 72 7.1. Peer Discovery State . . . . . . . . . . . . . . . . . . 12 73 7.2. Session Initialization State . . . . . . . . . . . . . . 13 74 7.3. In-Session State . . . . . . . . . . . . . . . . . . . . 14 75 7.3.1. Heartbeats . . . . . . . . . . . . . . . . . . . . . 14 76 7.4. Session Termination State . . . . . . . . . . . . . . . . 15 77 7.5. Session Reset state . . . . . . . . . . . . . . . . . . . 15 78 7.5.1. Unexpected TCP connection termination . . . . . . . . 16 79 8. Transaction Model . . . . . . . . . . . . . . . . . . . . . . 16 80 9. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . 17 81 9.1. Experiments . . . . . . . . . . . . . . . . . . . . . . . 17 82 10. Scalability . . . . . . . . . . . . . . . . . . . . . . . . . 18 83 11. DLEP Signal and Message Structure . . . . . . . . . . . . . . 18 84 11.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 18 85 11.2. DLEP Message Header . . . . . . . . . . . . . . . . . . 19 86 11.3. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 20 87 12. DLEP Signals and Messages . . . . . . . . . . . . . . . . . . 20 88 12.1. General Processing Rules . . . . . . . . . . . . . . . . 20 89 12.2. Status code processing . . . . . . . . . . . . . . . . . 21 90 12.3. Peer Discovery Signal . . . . . . . . . . . . . . . . . 22 91 12.4. Peer Offer Signal . . . . . . . . . . . . . . . . . . . 22 92 12.5. Session Initialization Message . . . . . . . . . . . . . 23 93 12.6. Session Initialization Response Message . . . . . . . . 24 94 12.7. Session Update Message . . . . . . . . . . . . . . . . . 25 95 12.8. Session Update Response Message . . . . . . . . . . . . 27 96 12.9. Session Termination Message . . . . . . . . . . . . . . 27 97 12.10. Session Termination Response Message . . . . . . . . . . 27 98 12.11. Destination Up Message . . . . . . . . . . . . . . . . . 28 99 12.12. Destination Up Response Message . . . . . . . . . . . . 29 100 12.13. Destination Announce Message . . . . . . . . . . . . . . 30 101 12.14. Destination Announce Response Message . . . . . . . . . 30 102 12.15. Destination Down Message . . . . . . . . . . . . . . . . 32 103 12.16. Destination Down Response Message . . . . . . . . . . . 32 104 12.17. Destination Update Message . . . . . . . . . . . . . . . 32 105 12.18. Link Characteristics Request Message . . . . . . . . . . 34 106 12.19. Link Characteristics Response Message . . . . . . . . . 34 107 12.20. Heartbeat Message . . . . . . . . . . . . . . . . . . . 35 108 13. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 36 109 13.1. Status . . . . . . . . . . . . . . . . . . . . . . . . . 37 110 13.2. IPv4 Connection Point . . . . . . . . . . . . . . . . . 40 111 13.3. IPv6 Connection Point . . . . . . . . . . . . . . . . . 41 112 13.4. Peer Type . . . . . . . . . . . . . . . . . . . . . . . 42 113 13.5. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 43 114 13.6. Extensions Supported . . . . . . . . . . . . . . . . . . 44 115 13.7. MAC Address . . . . . . . . . . . . . . . . . . . . . . 44 116 13.8. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 45 117 13.8.1. IPv4 Address Processing . . . . . . . . . . . . . . 46 118 13.9. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 47 119 13.9.1. IPv6 Address Processing . . . . . . . . . . . . . . 48 120 13.10. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 49 121 13.10.1. IPv4 Attached Subnet Processing . . . . . . . . . . 50 122 13.11. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 51 123 13.11.1. IPv6 Attached Subnet Processing . . . . . . . . . . 52 124 13.12. Maximum Data Rate (Receive) . . . . . . . . . . . . . . 53 125 13.13. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 53 126 13.14. Current Data Rate (Receive) . . . . . . . . . . . . . . 54 127 13.15. Current Data Rate (Transmit) . . . . . . . . . . . . . . 55 128 13.16. Latency . . . . . . . . . . . . . . . . . . . . . . . . 55 129 13.17. Resources . . . . . . . . . . . . . . . . . . . . . . . 56 130 13.18. Relative Link Quality (Receive) . . . . . . . . . . . . 57 131 13.19. Relative Link Quality (Transmit) . . . . . . . . . . . . 58 132 13.20. Maximum Transmission Unit (MTU) . . . . . . . . . . . . 59 133 14. Security Considerations . . . . . . . . . . . . . . . . . . . 59 134 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 61 135 15.1. Registrations . . . . . . . . . . . . . . . . . . . . . 61 136 15.2. Signal Type Registration . . . . . . . . . . . . . . . . 61 137 15.3. Message Type Registration . . . . . . . . . . . . . . . 61 138 15.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 62 139 15.5. DLEP Status Code Registrations . . . . . . . . . . . . . 63 140 15.6. DLEP Extensions Registrations . . . . . . . . . . . . . 64 141 15.7. DLEP IPv4 Connection Point Flags . . . . . . . . . . . . 64 142 15.8. DLEP IPv6 Connection Point Flags . . . . . . . . . . . . 65 143 15.9. DLEP Peer Type Flag . . . . . . . . . . . . . . . . . . 65 144 15.10. DLEP IPv4 Address Flag . . . . . . . . . . . . . . . . . 65 145 15.11. DLEP IPv6 Address Flag . . . . . . . . . . . . . . . . . 66 146 15.12. DLEP IPv4 Attached Subnet Flag . . . . . . . . . . . . . 66 147 15.13. DLEP IPv6 Attached Subnet Flag . . . . . . . . . . . . . 66 148 15.14. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 67 149 15.15. DLEP IPv4 Link-local Multicast Address . . . . . . . . . 67 150 15.16. DLEP IPv6 Link-local Multicast Address . . . . . . . . . 67 151 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 67 152 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 67 153 17.1. Normative References . . . . . . . . . . . . . . . . . . 67 154 17.2. Informative References . . . . . . . . . . . . . . . . . 68 155 Appendix A. Discovery Signal Flows . . . . . . . . . . . . . . . 69 156 Appendix B. Peer Level Message Flows . . . . . . . . . . . . . . 69 157 B.1. Session Initialization . . . . . . . . . . . . . . . . . 69 158 B.2. Session Initialization - Refused . . . . . . . . . . . . 70 159 B.3. Router Changes IP Addresses . . . . . . . . . . . . . . . 70 160 B.4. Modem Changes Session-wide Metrics . . . . . . . . . . . 70 161 B.5. Router Terminates Session . . . . . . . . . . . . . . . . 71 162 B.6. Modem Terminates Session . . . . . . . . . . . . . . . . 71 163 B.7. Session Heartbeats . . . . . . . . . . . . . . . . . . . 72 164 B.8. Router Detects a Heartbeat timeout . . . . . . . . . . . 73 165 B.9. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 74 166 Appendix C. Destination Specific Message Flows . . . . . . . . . 74 167 C.1. Common Destination Notification . . . . . . . . . . . . . 74 168 C.2. Multicast Destination Notification . . . . . . . . . . . 75 169 C.3. Link Characteristics Request . . . . . . . . . . . . . . 76 170 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77 172 1. Introduction 174 There exist today a collection of modem devices that control links of 175 variable datarate and quality. Examples of these types of links 176 include line-of-sight (LOS) terrestrial radios, satellite terminals, 177 and broadband modems. Fluctuations in speed and quality of these 178 links can occur due to configuration, or on a moment-to-moment basis, 179 due to physical phenomena like multipath interference, obstructions, 180 rain fade, etc. It is also quite possible that link quality and 181 datarate vary with respect to individual destinations on a link, and 182 with the type of traffic being sent. As an example, consider the 183 case of an IEEE 802.11 access point, serving two associated laptop 184 computers. In this environment, the answer to the question "What is 185 the datarate on the 802.11 link?" is "It depends on which associated 186 laptop we're talking about, and on what kind of traffic is being 187 sent." While the first laptop, being physically close to the access 188 point, may have a datarate of 54Mbps for unicast traffic, the other 189 laptop, being relatively far away, or obstructed by some object, can 190 simultaneously have a datarate of only 32Mbps for unicast. However, 191 for multicast traffic sent from the access point, all traffic is sent 192 at the base transmission rate (which is configurable, but depending 193 on the model of the access point, is usually 24Mbps or less). 195 In addition to utilizing variable datarate links, mobile networks are 196 challenged by the notion that link connectivity will come and go over 197 time, without an effect on a router's interface state (Up or Down). 198 Effectively utilizing a relatively short-lived connection is 199 problematic in IP routed networks, as IP routing protocols tend to 200 rely on interface state and independent timers to maintain network 201 convergence (e.g., HELLO messages and/or recognition of DEAD routing 202 adjacencies). These dynamic connections can be better utilized with 203 an event-driven paradigm, where acquisition of a new neighbor (or 204 loss of an existing one) is signaled, as opposed to a paradigm driven 205 by timers and/or interface state. DLEP not only implements such an 206 event-driven paradigm, but does so over a local (1 hop) TCP session, 207 which guarantees delivery of the event messages. 209 Another complicating factor for mobile networks are the different 210 methods of physically connecting the modem devices to the router. 211 Modems can be deployed as an interface card in a router's chassis, or 212 as a standalone device connected to the router via Ethernet or serial 213 link. In the case of Ethernet attachment, with existing protocols 214 and techniques, routing software cannot be aware of convergence 215 events occurring on the radio link (e.g., acquisition or loss of a 216 potential routing neighbor), nor can the router be aware of the 217 actual capacity of the link. This lack of awareness, along with the 218 variability in datarate, leads to a situation where finding the 219 (current) best route through the network to a given node is difficult 220 to establish and properly maintain. This is especially true of 221 demand-based access schemes such as Demand Assigned Multiple Access 222 (DAMA) implementations used on some satellite systems. With a DAMA- 223 based system, additional datarate may be available, but will not be 224 used unless the network devices emit traffic at a rate higher than 225 the currently established rate. Increasing the traffic rate does not 226 guarantee additional datarate will be allocated; rather, it may 227 result in data loss and additional retransmissions on the link. 229 Addressing the challenges listed above, the Dynamic Link Exchange 230 Protocol, or DLEP, has been developed. The DLEP protocol runs 231 between a router and its attached modem devices, allowing the modem 232 to communicate link characteristics as they change, and convergence 233 events (acquisition and loss of potential routing next-hops). The 234 following diagrams are used to illustrate the scope of DLEP packets. 236 |-------Local Node-------| |-------Remote Node------| 237 | | | | 238 +--------+ +-------+ +-------+ +--------+ 239 | Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router | 240 | | | Device| | Device| | | 241 +--------+ +-------+ +-------+ +--------+ 242 | | | Link | | | 243 |-DLEP--| | Protocol | |-DLEP--| 244 | | | (e.g. | | | 245 | | | 802.11) | | | 247 Figure 1: DLEP Network 249 In Figure 1, when the local modem detects the presence of a remote 250 node, it (the local modem) sends a message to its router via the DLEP 251 protocol. The message consists of an indication of what change has 252 occurred on the link (e.g., presence of a remote node detected), 253 along with a collection of DLEP-defined data items that further 254 describe the change. Upon receipt of the message, the local router 255 may take whatever action it deems appropriate, such as initiating 256 discovery protocols, and/or issuing HELLO messages to converge the 257 network. On a continuing, as-needed basis, the modem devices use 258 DLEP to report any characteristics of the link (datarate, latency, 259 etc.) that have changed. DLEP is independent of the link type and 260 topology supported by the modem. Note that the DLEP protocol is 261 specified to run only on the local link between router and modem. 262 Some over the air signaling may be necessary between the local and 263 remote modem in order to provide some parameters in DLEP messages 264 between the local modem and local router, but DLEP does not specify 265 how such over the air signaling is carried out. Over the air 266 signaling is purely a matter for the modem implementer. 268 Figure 2 shows how DLEP can support a configuration where routers are 269 connected with different link types. In this example, Modem A 270 implements a point-to-point link, and Modem B is connected via a 271 shared medium. In both cases, the DLEP protocol is used to report 272 the characteristics of the link (datarate, latency, etc.) to routers. 273 The modem is also able to use the DLEP session to notify the router 274 when the remote node is lost, shortening the time required to re- 275 converge the network. 277 +--------+ +--------+ 278 +----+ Modem | | Modem +---+ 279 | | Device | | Device | 280 | | Type A | <===== // ======> | Type A | | 281 | +--------+ P-2-P Link +--------+ | 282 +---+----+ +---+----+ 283 | Router | | Router | 284 | | | | 285 +---+----+ +---+----+ 286 | +--------+ +--------+ | 287 +-----+ Modem | | Modem | | 288 | Device | o o o o o o o o | Device +--+ 289 | Type B | o Shared o | Type B | 290 +--------+ o Medium o +--------+ 291 o o 292 o o 293 o o 294 o 295 +--------+ 296 | Modem | 297 | Device | 298 | Type B | 299 +---+----+ 300 | 301 | 302 +---+----+ 303 | Router | 304 | | 305 +--------+ 307 Figure 2: DLEP Network with Multiple Modem Devices 309 2. Protocol Overview 311 DLEP defines a set of Messages used by modems and their attached 312 routers to communicate events that occur on the physical link(s) 313 managed by the modem: for example, a remote node entering or leaving 314 the network, or that the link has changed. Associated with these 315 Messages are a set of Data Items - information that describes the 316 remote node (e.g., address information), and/or the characteristics 317 of the link to the remote node. Throughout this document, we refer 318 to a modems/routers participating in a DLEP session as 'DLEP 319 Participants', unless a specific distinction (e.g. modem or router) 320 is required. 322 DLEP uses a session-oriented paradigm between the modem device and 323 its associated router. If multiple modem devices are attached to a 324 router (as in Figure 2), or the modem supports multiple connections 325 (via multiple logical or physical interfaces), then separate DLEP 326 sessions exist for each modem or connection. A router and modem form 327 a session by completing the discovery and initialization process. 328 This router-modem session persists unless or until it either (1) 329 times out, based on the absence of DLEP traffic (including 330 heartbeats), or (2) is explicitly torn down by one of the DLEP 331 participants. 333 While this document represents the best efforts of the working group 334 to be functionally complete, it is recognized that extensions to DLEP 335 will in all likelihood be necessary as more link types are used. 336 Such extensions are defined as additional Messages, Data Items and/or 337 status codes, and associated rules of behavior, that are not defined 338 in this document. DLEP contains a standard mechanism for router and 339 modem implementations to negotiate the available extensions to use on 340 a per-session basis. 342 2.1. Destinations 344 The router/modem session provides a carrier for information exchange 345 concerning 'destinations' that are available via the modem device. 346 Destinations can be identified by either the router or the modem, and 347 represent a specific, addressable location that can be reached via 348 the link(s) managed by the modem. 350 The DLEP Messages concerning destinations thus become the way for 351 routers and modems to maintain, and notify each other about, an 352 information base representing the physical and logical destinations 353 accessible via the modem device, as well as the link characteristics 354 to those destinations. 356 A destination can be either physical or logical. The example of a 357 physical destination would be that of a remote, far-end router 358 attached via the variable-quality network. It should be noted that 359 for physical destinations the MAC address is the address of the far- 360 end router, not the modem. 362 The example of a logical destination is Multicast. Multicast traffic 363 destined for the variable-quality network (the network accessed via 364 the modem) is handled in IP networks by deriving a Layer 2 MAC 365 address based on the Layer 3 address. Leveraging on this scheme, 366 multicast traffic is supported in DLEP simply by treating the derived 367 MAC address as any other destination in the network. 369 To support these logical destinations, one of the DLEP participants 370 (typically, the router) informs the other as to the existence of the 371 logical destination. The modem, once it is aware of the existence of 372 this logical destination, reports link characteristics just as it 373 would for any other destination in the network. The specific 374 algorithms a modem would use to derive metrics on logical 375 destinations are outside the scope of this specification, and is left 376 to specific implementations to decide. 378 In all cases, when this specification uses the term destination, it 379 refers to the addressable locations, either logical or physical, that 380 are accessible by the radio link(s). 382 2.2. Conventions and Terminology 384 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 385 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 386 "OPTIONAL" in this document are to be interpreted as described in BCP 387 14, RFC 2119 [RFC2119]. 389 3. Requirements 391 DLEP MUST be implemented on a single Layer 2 domain. The protocol 392 identifies next-hop destinations by using the MAC address for 393 delivering data traffic. No manipulation or substitution is 394 performed; the MAC address supplied in all DLEP Messages is used as 395 the Destination MAC address for frames emitted by the participating 396 router. MAC addresses MUST be unique within the context of router- 397 modem session. 399 To enforce the single Layer 2 domain, implementations MUST support 400 The Generalized TTL Security Mechanism [RFC5082], and implementations 401 MUST adhere to this specification for all DLEP Messages. 403 DLEP specifies UDP multicast for single-hop discovery signaling, and 404 TCP for transport of the Messages. Modems and routers participating 405 in DLEP sessions MUST have topologically consistent IP addresses 406 assigned. It is RECOMMENDED that DLEP implementations utilize IPv6 407 link-local addresses to reduce the administrative burden of address 408 assignment. 410 DLEP relies on the guaranteed delivery of its Messages between router 411 and modem, once the 1 hop discovery process is complete, hence, the 412 specification of TCP to carry the Messages. Other reliable 413 transports for the protocol are possible, but are outside the scope 414 of this document. 416 4. Implementation Scenarios 418 During development of this specification, two types of deployments 419 were discussed. 421 The first can be viewed as a "dedicated deployment". In this mode, 422 DLEP routers and modems are either directly connected (e.g., using 423 cross-over cables to connect interfaces), or are connected to a 424 dedicated switch. An example of this type of deployment would be a 425 router with a line-of- sight radio connected into one interface, with 426 a satellite modem connected into another interface. In mobile 427 environments, the router and the connected modem(s) are placed into a 428 mobile platform (e.g., a vehicle, boat, or airplane). In this mode, 429 when a switch is used, it is possible that a small number of 430 ancillary devices (e.g., a laptop) are also plugged into the switch. 431 But in either event, the resulting network segment is constrained to 432 a small number of devices, and is not generally accessible from 433 anywhere else in the network. 435 The other type of deployment envisioned can be viewed as a "networked 436 deployment". In this type of scenario, the DLEP router and modem(s) 437 are placed on a segment that is accessible from other points in the 438 network. In this scenario, not only are the DLEP router and modem(s) 439 accessible from other points in the network; the router and a given 440 modem could be multiple physical hops away from each other. As 441 mentioned, this scenario necessitates the use of Layer 2 tunneling 442 technology to enforce the single-hop requirement of DLEP. 444 5. Assumptions 446 DLEP assumes that a signaling protocol exists between modems 447 participating in a network. The specification does not define the 448 character or behavior of this over-the-air signaling, but does expect 449 some information to be carried (or derived) by the signaling, such as 450 the arrival and departure of modems from this network, and the 451 variation of the link characteristics between modems. This 452 information is then assumed to be used by the modem to implement the 453 DLEP protocol. 455 The specification assumes that the link between router and modem is 456 static with respect to datarate and latency, and that this link is 457 not likely to be the cause of a performance bottleneck. In 458 deployments where the router and modem are physically separated by 459 multiple network hops, served by Layer 2 tunneling technology, DLEP 460 statistics on the RF links could be insufficient for routing 461 protocols to make appropriate routing decisions. This would 462 especially become an issue in cases where the Layer 2 tunnel between 463 router and modem is itself served in part (or in total) with a 464 wireless back-haul link. 466 6. Metrics 468 DLEP includes the ability for the router and modem to communicate 469 metrics that reflect the characteristics (e.g., datarate, latency) of 470 the variable-quality link in use. DLEP does not specify how a given 471 metric value is to be calculated, rather, the protocol assumes that 472 metrics have been calculated by a 'best effort', incorporating all 473 pertinent data that is available to the modem device. Metrics based 474 on large enough sample sizes will preclude short traffic bursts from 475 adversely skewing reported values. 477 DLEP allows for metrics to be sent within two contexts - metrics for 478 a specific destination within the network (e.g., a specific router), 479 and per-session (those that apply to all destinations accessed via 480 the modem). Most metrics can be further subdivided into transmit and 481 receive metrics. In cases where metrics are provided at session 482 level, the router propagates the metrics to all entries in its 483 information base for destinations that are accessed via the modem. 485 DLEP modems announce all metric Data Items that will be reported 486 during the session, and provide default values for those metrics, in 487 the Session Initialization Response Message (Section 12.6). In order 488 to use a metric type that was not included in the Session 489 Initialization Response Message, modem implementations terminate the 490 session with the router (via the Session Terminate Message 491 (Section 12.9)), and establish a new session. 493 A DLEP modem can send metrics both in a session context, via the 494 Session Update Message (Section 12.7), and a specific destination 495 context, via the Destination Update Message (Section 12.17), at any 496 time. The most recently received metric value takes precedence over 497 any earlier value, regardless of context - that is: 499 1. If the router receives metrics in a specific destination context 500 (via the Destination Update Message), then the specific 501 destination is updated with the new metric. 503 2. If the router receives metrics in a session-wide context (via the 504 Session Update Message), then the metrics for all destinations 505 accessed via the modem are updated with the new metric. 507 It is left to implementations to choose sensible default values based 508 on their specific characteristics. Modems having static (non- 509 changing) link metric characteristics can report metrics only once 510 for a given destination (or once on a session-wide basis, if all 511 connections via the modem are of this static nature). 513 In addition to communicating existing metrics about the link, DLEP 514 provides a Message allowing a router to request a different datarate 515 or latency from the modem. This Message is the Link Characteristics 516 Request Message (Section 12.18), and gives the router the ability to 517 deal with requisite increases (or decreases) of allocated datarate/ 518 latency in demand-based schemes in a more deterministic manner. 520 7. DLEP Session Flow 522 All DLEP participants of a session transition through a number of 523 distinct states during the lifetime of a DLEP session: 525 o Peer Discovery 527 o Session Initialization 529 o In-Session 531 o Session Termination 533 o Session Reset 535 Modems, and routers supporting DLEP discovery, transition through all 536 five (5) of the above states. Routers that rely on preconfigured TCP 537 address/port information start in the Session Initialization state. 539 Modems MUST support the Peer Discovery state. 541 7.1. Peer Discovery State 543 Modems MUST support DLEP Peer Discovery; routers MAY support the 544 discovery signals, or rely on a priori configuration to locate 545 modems. If a router chooses to support DLEP discovery, all signals 546 MUST be supported. 548 In the Peer Discovery state, routers that support DLEP discovery MUST 549 send Peer Discovery Signals (Section 12.3) to initiate modem 550 discovery. 552 The router implementation then waits for a Peer Offer Signal 553 (Section 12.4) response from a potential DLEP modem. While in the 554 Peer Discovery state, Peer Discovery Signals MUST be sent repeatedly 555 by a DLEP router, at regular intervals. It is RECOMMENDED that this 556 interval be set to 60 seconds. The interval MUST be a minimum of one 557 second; it SHOULD be a configurable parameter. Note that this 558 operation (sending Peer Discovery and waiting for Peer Offer) is 559 outside the DLEP Transaction Model (Section 8), as the Transaction 560 Model only describes Messages on a TCP session. 562 Routers receiving a Peer Offer Signal MUST use one of the modem 563 address/port combinations from the Peer Offer Signal to establish a 564 TCP connection to the modem, even if a priori configuration exists. 565 If multiple connection point Data Items exist in the received Peer 566 Offer Signal, routers SHOULD prioritize IPv6 connection points over 567 IPv4 connection points. Routers supporting TLS [RFC5246] MUST 568 prioritize connection points using TLS over those that do not. If 569 multiple connection points exist with the same transport (e.g. IPv6 570 or IPv4), implementations MAY use their own heuristics to determine 571 the order in which they are tried. If a TCP connection cannot be 572 achieved using any of the address/port combinations and the Discovery 573 mechanism is in use, then the router SHOULD resume issuing Peer 574 Discovery Signals. If no Connection Point Data Items are included in 575 the Peer Offer Signal, the router MUST use the source address of the 576 UDP packet containing the Peer Offer Signal as the IP address, and 577 the DLEP well-known port number. 579 In the Peer Discovery state, the modem implementation MUST listen for 580 incoming Peer Discovery Signals on the DLEP well-known IPv6 and/or 581 IPv4 link-local multicast address and port. On receipt of a valid 582 Peer Discovery Signal, it MUST reply with a Peer Offer Signal. 584 Modems MUST be prepared to accept a TCP connection from a router that 585 is not using the Discovery mechanism, i.e. a connection attempt that 586 occurs without a preceding Peer Discovery Signal. 588 Upon establishment of a TCP connection, both modem and router enter 589 the Session Initialization state. It is up to the router 590 implementation if Peer Discovery Signals continue to be sent after 591 the device has transitioned to the Session Initialization state. 592 Modem implementations MUST silently ignore Peer Discovery Signals 593 from a router with which it already has a TCP connection. 595 7.2. Session Initialization State 597 On entering the Session Initialization state, the router MUST send a 598 Session Initialization Message (Section 12.5) to the modem. The 599 router MUST then wait for receipt of a Session Initialization 600 Response Message (Section 12.6) from the modem. Receipt of the 601 Session Initialization Response Message containing a Status Data Item 602 (Section 13.1) with status code set to 0 'Success', see Table 2, 603 indicates that the modem has received and processed the Session 604 Initialization Message, and the router MUST transition to the In- 605 Session state. 607 On entering the Session Initialization state, the modem MUST wait for 608 receipt of a Session Initialization Message from the router. Upon 609 receipt of a Session Initialization Message, the modem MUST send a 610 Session Initialization Response Message, and the session MUST 611 transition to the In-Session state. If the modem receives any 612 Message other than Session Initialization, or it fails to parse the 613 received Message, it MUST NOT send any Message, and MUST terminate 614 the TCP connection and transition to the Session Reset state. 616 DLEP provides an extension negotiation capability to be used in the 617 Session Initialization state, see Section 9. Extensions supported by 618 an implementation MUST be declared to potential DLEP participants 619 using the Extensions Supported Data Item (Section 13.6). Once both 620 DLEP participants have exchanged initialization Messages, an 621 implementation MUST NOT emit any Message, Signal, Data Item or status 622 code associated with an extension that was not specified in the 623 received initialization Message from its peer. 625 7.3. In-Session State 627 In the In-Session state, Messages can flow in both directions between 628 DLEP participants, indicating changes to the session state, the 629 arrival or departure of reachable destinations, or changes of the 630 state of the links to the destinations. 632 The In-Session state is maintained until one of the following 633 conditions occur: 635 o The implementation terminates the session by sending a Session 636 Termination Message (Section 12.9), or, 638 o Its peer terminates the session, indicated by receiving a Session 639 Termination Message. 641 The implementation MUST then transition to the Session Termination 642 state. 644 7.3.1. Heartbeats 646 In order to maintain the In-Session state, periodic Heartbeat 647 Messages (Section 12.20) MUST be exchanged between router and modem. 648 These Messages are intended to keep the session alive, and to verify 649 bidirectional connectivity between the two DLEP participants. It is 650 RECOMMENDED that the interval timer between heartbeat messages be set 651 to 60 seconds. The interval MUST be a minimum of one second; it 652 SHOULD be a configurable parameter. 654 Each DLEP participant is responsible for the creation of Heartbeat 655 Messages. 657 Receipt of any valid DLEP Message MUST reset the heartbeat interval 658 timer (i.e., valid DLEP Messages take the place of, and obviate the 659 need for, additional Heartbeat Messages). 661 Implementations MUST allow a minimum of two (2) heartbeat intervals 662 to expire with no Messages from its peer before terminating the 663 session. When terminating the session, a Session Termination Message 664 containing a Status Data Item (Section 13.1) with status code set to 665 132 'Timed Out', see Table 2, MUST be sent, and then the 666 implementation MUST transition to the Session Termination state. 668 7.4. Session Termination State 670 When an implementation enters the Session Termination state after 671 sending a Session Termination Message (Section 12.9) as the result of 672 an invalid Message or error, it MUST wait for a Session Termination 673 Response Message (Section 12.10) from its peer. Senders SHOULD allow 674 four (4) heartbeat intervals to expire before assuming that its peer 675 is unresponsive, and continuing with session termination. Any other 676 Message received while waiting MUST be silently ignored. 678 When the sender of the Session Termination Message receives a Session 679 Termination Response Message from its peer, or times out, it MUST 680 transition to the Session Reset state. 682 When an implementation receives a Session Termination Message from 683 its peer, it enters the Session Termination state and then it MUST 684 immediately send a Session Termination Response and transition to the 685 Session Reset state. 687 7.5. Session Reset state 689 In the Session Reset state the implementation MUST perform the 690 following actions: 692 o Release all resources allocated for the session. 694 o Eliminate all destinations in the information base represented by 695 the session. Destination Down Messages (Section 12.15) MUST NOT 696 be sent. 698 o Terminate the TCP connection. 700 Having completed these actions the implementation SHOULD return to 701 the relevant initial state: Peer Discovery for modems; either Peer 702 Discovery or Session Initialization for routers, depending on 703 configuration. 705 7.5.1. Unexpected TCP connection termination 707 If the TCP connection between DLEP participants is terminated when an 708 implementation is not in the Session Reset state, the implementation 709 MUST immediately transition to the Session Reset state. 711 8. Transaction Model 713 DLEP defines a simple Message transaction model: Only one request per 714 destination may be in progress at a time per session. A Message 715 transaction is considered complete when a response matching a 716 previously issued request is received. If a DLEP participant 717 receives a request for a destination for which there is already an 718 outstanding request, the implementation MUST terminate the session by 719 issuing a Session Termination Message (Section 12.9) containing a 720 Status Data Item (Section 13.1) with status code set to 129 721 'Unexpected Message', see Table 2, and transition to the Session 722 Termination state. There is no restriction to the total number of 723 Message transactions in progress at a time, as long as each 724 transaction refers to a different destination. 726 It should be noted that some requests may take a considerable amount 727 of time for some DLEP participants to complete, for example, a modem 728 handling a multicast destination up request may have to perform a 729 complex network reconfiguration. A sending implementation MUST be 730 able to handle such long running transactions gracefully. 732 Additionally, only one session request, e.g. a Session Initialization 733 Message (Section 12.5), may be in progress at a time per session. As 734 above, a session transaction is considered complete when a response 735 matching a previously issued request is received. If a DLEP 736 participant receives a session request while there is already a 737 session request in progress, it MUST terminate the session by issuing 738 a Session Termination Message containing a Status Data Item with 739 status code set to 129 'Unexpected Message', and transition to the 740 Session Termination state. Only the Session Termination Message may 741 be issued when a session transaction is in progress. Heartbeat 742 Messages (Section 12.20) MUST NOT be considered part of a session 743 transaction. 745 DLEP transactions do not time out and are not cancellable, except for 746 transactions in-flight when the DLEP session is reset. If the 747 session is terminated, canceling transactions in progress MUST be 748 performed as part of resetting the state machine. An implementation 749 can detect if its peer has failed in some way by use of the session 750 heartbeat mechanism during the In-Session state, see Section 7.3. 752 9. Extensions 754 Extensions MUST be negotiated on a per-session basis during session 755 initialization via the Extensions Supported mechanism. 756 Implementations are not required to support any extension in order to 757 be considered DLEP compliant. 759 If interoperable protocol extensions are required, they will need to 760 be standardized either as an update to this document, or as an 761 additional stand-alone specification. The requests for IANA- 762 controlled registries in this document contain sufficient Reserved 763 space for DLEP Signals, Messages, Data Items and status codes to 764 accommodate future extensions to the protocol. 766 As multiple protocol extensions MAY be announced during session 767 initialization, authors of protocol extensions need to consider the 768 interaction of their extension with other published extensions, and 769 specify any incompatibilities. 771 9.1. Experiments 773 This document requests Private Use numbering space in the DLEP 774 Signal, Message, Data Item and status code registries for 775 experimental extensions. The intent is to allow for experimentation 776 with new Signals, Messages, Data Items, and/or status codes, while 777 still retaining the documented DLEP behavior. 779 Use of the Private Use Signals, Messages, Data Items, status codes, 780 or behaviors MUST be announced as DLEP Extensions, during session 781 initialization, using extension identifiers from the Private Use 782 space in the Extensions Supported registry (Table 3), with a value 783 agreed upon (a priori) between the participants. DLEP extensions 784 using the Private Use numbering space are commonly referred to as 785 Experiments. 787 Multiple experiments MAY be announced in the Session Initialization 788 Messages. However, use of multiple experiments in a single session 789 could lead to interoperability issues or unexpected results (e.g., 790 clashes of experimental Signals, Messages, Data Items and/or status 791 code types), and is therefore discouraged. It is left to 792 implementations to determine the correct processing path (e.g., a 793 decision on whether to terminate the session, or to establish a 794 precedence of the conflicting definitions) if such conflicts arise. 796 10. Scalability 798 The protocol is intended to support thousands of destinations on a 799 given modem/router pair. At large scale, implementations should 800 consider employing techniques to prevent flooding its peer with a 801 large number of Messages in a short time. For example, a dampening 802 algorithm could be employed to prevent a flapping device from 803 generating a large number of Destination Up/Destination Down 804 Messages. 806 Also, use of techniques such as a hysteresis can lessen the impact of 807 rapid, minor fluctuations in link quality. The specific algorithms 808 for handling flapping destinations and minor changes in link quality 809 are outside the scope of this specification. 811 11. DLEP Signal and Message Structure 813 DLEP defines two protocol units used in two different ways: Signals 814 and Messages. Signals are only used in the Discovery mechanism and 815 are carried in UDP datagrams. Messages are used bidirectionally over 816 a TCP connection between the participants, in the Session 817 Initialization, In-Session and Session Termination states. 819 Both Signals and Messages consist of a Header followed by an 820 unordered list of Data Items. Headers consist of Type and Length 821 information, while Data Items are encoded as TLV (Type-Length-Value) 822 structures. In this document, the Data Items following a Signal or 823 Message Header are described as being 'contained in' the Signal or 824 Message. 826 There is no restriction on the order of Data Items following a 827 Header, and the acceptability of duplicate Data Items is defined by 828 the definition of the Signal or Message declared by the type in the 829 Header. 831 All integers in Header fields and values MUST be in network byte- 832 order. 834 11.1. DLEP Signal Header 836 The DLEP Signal Header contains the following fields: 838 0 1 2 3 839 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 840 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 841 | 'D' | 'L' | 'E' | 'P' | 842 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 843 | Signal Type | Length | 844 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 846 Figure 3: DLEP Signal Header 848 "DLEP": Every Signal MUST start with the characters: U+0044, U+004C, 849 U+0045, U+0050. 851 Signal Type: A 16-bit unsigned integer containing one of the DLEP 852 Signal Type values defined in this document. 854 Length: The length in octets, expressed as a 16-bit unsigned 855 integer, of all of the DLEP Data Items contained in this Signal. 856 This length MUST NOT include the length of the Signal Header 857 itself. 859 The DLEP Signal Header is immediately followed by zero or more DLEP 860 Data Items, encoded in TLVs, as defined in this document. 862 11.2. DLEP Message Header 864 The DLEP Message Header contains the following fields: 866 0 1 2 3 867 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 868 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 869 | Message Type | Length | 870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 872 Figure 4: DLEP Message Header 874 Message Type: A 16-bit unsigned integer containing one of the DLEP 875 Message Type values defined in this document. 877 Length: The length in octets, expressed as a 16-bit unsigned 878 integer, of all of the DLEP Data Items contained in this Message. 879 This length MUST NOT include the length of the Message Header 880 itself. 882 The DLEP Message Header is immediately followed by zero or more DLEP 883 Data Items, encoded in TLVs, as defined in this document. 885 11.3. DLEP Generic Data Item 887 All DLEP Data Items contain the following fields: 889 0 1 2 3 890 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 891 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 892 | Data Item Type | Length | 893 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 894 | Value... : 895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 897 Figure 5: DLEP Generic Data Item 899 Data Item Type: A 16-bit unsigned integer field specifying the type 900 of Data Item being sent. 902 Length: The length in octets, expressed as a 16-bit unsigned 903 integer, of the Value field of the Data Item. This length MUST 904 NOT include the length of the Data Item Type and Length fields. 906 Value: A field of octets, which contains data specific to a 907 particular Data Item. 909 12. DLEP Signals and Messages 911 12.1. General Processing Rules 913 If an unrecognized, or unexpected Signal is received, or a received 914 Signal contains unrecognized, invalid, or disallowed duplicate Data 915 Items, the receiving implementation MUST ignore the Signal. 917 If a Signal is received with a TTL value that is NOT equal to 255, 918 the receiving implementation MUST ignore the Signal. 920 If an unrecognized Message is received, the receiving implementation 921 MUST issue a Session Termination Message (Section 12.9) containing a 922 Status Data Item (Section 13.1) with status code set to 128 'Unknown 923 Message', see Table 2, and transition to the Session Termination 924 state. 926 If an unexpected Message is received, the receiving implementation 927 MUST issue a Session Termination Message containing a Status Data 928 Item with status code set to 129 'Unexpected Message', and transition 929 to the Session Termination state. 931 If a received Message contains unrecognized, invalid, or disallowed 932 duplicate Data Items, the receiving implementation MUST issue a 933 Session Termination Message containing a Status Data Item with status 934 code set to 130 'Invalid Data', and transition to the Session 935 Termination state. 937 If a packet in the TCP stream is received with a TTL value other than 938 255, the receiving implementation MUST immediately transition to the 939 Session Reset state. 941 Prior to the exchange of Destination Up (Section 12.11) and 942 Destination Up Response (Section 12.12) Messages, or Destination 943 Announce (Section 12.13) and Destination Announce Response 944 (Section 12.14) Messages, no Messages concerning a destination may be 945 sent. An implementation receiving any Message with such an 946 unannounced destination MUST terminate the session by issuing a 947 Session Termination Message containing a Status Data Item with status 948 code set to 131 'Invalid Destination', and transition to the Session 949 Termination state. 951 After exchanging Destination Down (Section 12.15) and Destination 952 Down Response (Section 12.16) Messages, no Messages concerning a 953 destination may be a sent until a new Destination Up or Destination 954 Announce Message is sent. An implementation receiving a Message 955 about a destination previously announced as 'down' MUST terminate the 956 session by issuing a Session Termination Message containing a Status 957 Data Item with status code set to 131 'Invalid Destination', and 958 transition to the Session Termination state. 960 12.2. Status code processing 962 The behavior of a DLEP participant receiving a Message containing a 963 Status Data Item (Section 13.1) is defined by the failure mode 964 associated with the value of the status code field, see Table 2. All 965 status code values less than 100 have a failure mode of 'Continue', 966 all other status codes have a failure mode of 'Terminate'. 968 A DLEP participant receiving any Message apart from Session 969 Termination Message (Section 12.9) containing a Status Data Item with 970 a status code value with failure mode 'Terminate' MUST immediately 971 issue a Session Termination Message echoing the received Status Data 972 Item, and then transition to the Session Termination state. 974 A DLEP participant receiving a Message containing a Status Data Item 975 with a status code value with failure mode 'Continue' can continue 976 normal operation of the session. 978 12.3. Peer Discovery Signal 980 A Peer Discovery Signal SHOULD be sent by a DLEP router to discover 981 DLEP modems in the network, see Section 7.1. 983 A Peer Discovery Signal MUST be encoded within a UDP packet. The 984 destination MUST be set to the DLEP well-known address and port 985 number. For routers supporting both IPv4 and IPv6 DLEP operation, it 986 is RECOMMENDED that IPv6 be selected as the transport. The source IP 987 address MUST be set to the router IP address associated with the DLEP 988 interface. There is no DLEP-specific restriction on source port. 990 To construct a Peer Discovery Signal, the Signal Type value in the 991 Signal Header is set to 1 (see Signal Type Registration 992 (Section 15.2)). 994 The Peer Discovery Signal MAY contain a Peer Type Data Item 995 (Section 13.4). 997 12.4. Peer Offer Signal 999 A Peer Offer Signal MUST be sent by a DLEP modem in response to a 1000 properly formatted and addressed Peer Discovery Signal 1001 (Section 12.3). 1003 A Peer Offer Signal MUST be encoded within a UDP packet. The IP 1004 source and destination fields in the packet MUST be set by swapping 1005 the values received in the Peer Discovery Signal. The Peer Offer 1006 Signal completes the discovery process, see Section 7.1. 1008 To construct a Peer Offer Signal, the Signal Type value in the Signal 1009 Header is set to 2 (see Signal Type Registration (Section 15.2)). 1011 The Peer Offer Signal MAY contain a Peer Type Data Item 1012 (Section 13.4). 1014 The Peer Offer Signal MAY contain one or more of any of the following 1015 Data Items, with different values: 1017 o IPv4 Connection Point (Section 13.2) 1019 o IPv6 Connection Point (Section 13.3) 1021 The IP Connection Point Data Items indicate the unicast address the 1022 router MUST use when connecting the DLEP TCP session. 1024 12.5. Session Initialization Message 1026 A Session Initialization Message MUST be sent by a DLEP router as the 1027 first Message of the DLEP TCP session. It is sent by the router 1028 after a TCP connect to an address/port combination that was obtained 1029 either via receipt of a Peer Offer, or from a priori configuration. 1031 To construct a Session Initialization Message, the Message Type value 1032 in the Message Header is set to 1 (see Message Type Registration 1033 (Section 15.3)). 1035 The Session Initialization Message MUST contain one of each of the 1036 following Data Items: 1038 o Heartbeat Interval Data Item (Section 13.5) 1040 o Peer Type (Section 13.4) 1042 The Session Initialization Message MUST contain an Extensions 1043 Supported Data Item (Section 13.6), if DLEP extensions are supported. 1045 The Session Initialization Message MAY contain one or more of each of 1046 the following Data Items, with different values, and the data item 1047 Add flag set to 1: 1049 o IPv4 Address (Section 13.8) 1051 o IPv6 Address (Section 13.9) 1053 o IPv4 Attached Subnet (Section 13.10) 1055 o IPv6 Attached Subnet (Section 13.11) 1057 If any optional extensions are supported by the implementation, they 1058 MUST be enumerated in the Extensions Supported Data Item. If an 1059 Extensions Supported Data Item does not exist in a Session 1060 Initialization Message, the modem MUST conclude that there is no 1061 support for extensions in the router. 1063 DLEP Heartbeats are not started until receipt of the Session 1064 Initialization Response Message (Section 12.6), and therefore 1065 implementations MUST use their own timeout heuristics for this 1066 Message. 1068 As an exception to the general rule governing an implementation 1069 receiving an unrecognized Data Item in a Message, see Section 12.1, 1070 if a Session Initialization Message contains one or more Extension 1071 Supported Data Items announcing support for extensions that the 1072 implementation does not recognize, then the implementation MAY ignore 1073 Data Items it does not recognize. 1075 12.6. Session Initialization Response Message 1077 A Session Initialization Response Message MUST be sent by a DLEP 1078 modem in response to a received Session Initialization Message 1079 (Section 12.5). 1081 To construct a Session Initialization Response Message, the Message 1082 Type value in the Message Header is set to 2 (see Message Type 1083 Registration (Section 15.3)). 1085 The Session Initialization Response Message MUST contain one of each 1086 of the following Data Items: 1088 o Status (Section 13.1) 1090 o Peer Type (Section 13.4) 1092 o Heartbeat Interval (Section 13.5) 1094 o Maximum Data Rate (Receive) (Section 13.12) 1096 o Maximum Data Rate (Transmit) (Section 13.13) 1098 o Current Data Rate (Receive) (Section 13.14) 1100 o Current Data Rate (Transmit) (Section 13.15) 1102 o Latency (Section 13.16) 1104 The Session Initialization Response Message MUST contain one of each 1105 of the following Data Items, if the Data Item will be used during the 1106 lifetime of the session: 1108 o Resources (Section 13.17) 1110 o Relative Link Quality (Receive) (Section 13.18) 1112 o Relative Link Quality (Transmit) (Section 13.19) 1114 o Maximum Transmission Unit (MTU) (Section 13.20) 1116 The Session Initialization Response Message MUST contain an 1117 Extensions Supported Data Item (Section 13.6), if DLEP extensions are 1118 supported. 1120 The Session Initialization Response Message MAY contain one or more 1121 of each of the following Data Items, with different values, and the 1122 data item Add flag set to 1: 1124 o IPv4 Address (Section 13.8) 1126 o IPv6 Address (Section 13.9) 1128 o IPv4 Attached Subnet (Section 13.10) 1130 o IPv6 Attached Subnet (Section 13.11) 1132 The Session Initialization Response Message completes the DLEP 1133 session establishment; the modem should transition to the In-Session 1134 state when the Message is sent, and the router should transition to 1135 the In-Session state upon receipt of an acceptable Session 1136 Initialization Response Message. 1138 All supported metric Data Items MUST be included in the Session 1139 Initialization Response Message, with default values to be used on a 1140 session-wide basis. This can be viewed as the modem 'declaring' all 1141 supported metrics at DLEP session initialization. Receipt of any 1142 further DLEP Message containing a metric Data Item not included in 1143 the Session Initialization Response Message MUST be treated as an 1144 error, resulting in the termination of the DLEP session between 1145 router and modem. 1147 If any optional extensions are supported by the modem, they MUST be 1148 enumerated in the Extensions Supported Data Item. If an Extensions 1149 Supported Data Item does not exist in a Session Initialization 1150 Response Message, the router MUST conclude that there is no support 1151 for extensions in the modem. 1153 After the Session Initialization/Session Initialization Response 1154 Messages have been successfully exchanged, implementations MUST only 1155 use extensions that are supported by both DLEP participants, see 1156 Section 7.2. 1158 12.7. Session Update Message 1160 A Session Update Message MAY be sent by a DLEP participant to 1161 indicate local Layer 3 address changes, or metric changes on a 1162 session-wide basis. 1164 To construct a Session Update Message, the Message Type value in the 1165 Message Header is set to 3 (see Message Type Registration 1166 (Section 15.3)). 1168 The Session Update Message MAY contain one or more of each of the 1169 following Data Items, with different values: 1171 o IPv4 Address (Section 13.8) 1173 o IPv6 Address (Section 13.9) 1175 o IPv4 Attached Subnet (Section 13.10) 1177 o IPv6 Attached Subnet (Section 13.11) 1179 When sent by a modem, the Session Update Message MAY contain one of 1180 each of the following Data Items: 1182 o Maximum Data Rate (Receive) (Section 13.12) 1184 o Maximum Data Rate (Transmit) (Section 13.13) 1186 o Current Data Rate (Receive) (Section 13.14) 1188 o Current Data Rate (Transmit) (Section 13.15) 1190 o Latency (Section 13.16) 1192 When sent by a modem, the Session Update Message MAY contain one of 1193 each of the following Data Items, if the Data Item is in use by the 1194 session: 1196 o Resources (Section 13.17) 1198 o Relative Link Quality (Receive) (Section 13.18) 1200 o Relative Link Quality (Transmit) (Section 13.19) 1202 o Maximum Transmission Unit (MTU) (Section 13.20) 1204 If metrics are supplied with the Session Update Message (e.g., 1205 Maximum Data Rate), these metrics are considered to be session-wide, 1206 and therefore MUST be applied to all destinations in the information 1207 base associated with the DLEP session. This includes destinations 1208 for which metrics may have been stored based on received Destination 1209 Update messages. 1211 It should be noted that Session Update Messages can be sent by both 1212 routers and modems. For example, addition of an IPv4 address on the 1213 router MAY prompt a Session Update Message to its attached modems. 1214 Also, for example, a modem that changes its Maximum Data Rate 1215 (Receive) for all destinations MAY reflect that change via a Session 1216 Update Message to its attached router(s). 1218 Concerning Layer 3 addresses and subnets: If the modem is capable of 1219 understanding and forwarding this information (via mechanisms not 1220 defined by DLEP), the update would prompt any remote DLEP-enabled 1221 modems to issue a Destination Update Message (Section 12.17) to their 1222 local routers with the new (or deleted) addresses and subnets. 1224 12.8. Session Update Response Message 1226 A Session Update Response Message MUST be sent by a DLEP participant 1227 when a Session Update Message (Section 12.7) is received. 1229 To construct a Session Update Response Message, the Message Type 1230 value in the Message Header is set to 4 (see Message Type 1231 Registration (Section 15.3)). 1233 The Session Update Response Message MUST contain a Status Data Item 1234 (Section 13.1). 1236 12.9. Session Termination Message 1238 When a DLEP participant determines the DLEP session needs to be 1239 terminated, the participant MUST send (or attempt to send) a Session 1240 Termination Message. 1242 To construct a Session Termination Message, the Message Type value in 1243 the Message Header is set to 5 (see Message Type Registration 1244 (Section 15.3)). 1246 The Session Termination Message MUST contain Status Data Item 1247 (Section 13.1). 1249 It should be noted that Session Termination Messages can be sent by 1250 both routers and modems. 1252 12.10. Session Termination Response Message 1254 A Session Termination Response Message MUST be sent by a DLEP 1255 participant when a Session Termination Message (Section 12.9) is 1256 received. 1258 To construct a Session Termination Response Message, the Message Type 1259 value in the Message Header is set to 6 (see Message Type 1260 Registration (Section 15.3)). 1262 There are no valid Data Items for the Session Termination Response 1263 Message. 1265 Receipt of a Session Termination Response Message completes the tear- 1266 down of the DLEP session, see Section 7.4. 1268 12.11. Destination Up Message 1270 Destination Up Messages MAY be sent by a modem to inform its attached 1271 router of the presence of a new reachable destination. 1273 To construct a Destination Up Message, the Message Type value in the 1274 Message Header is set to 7 (see Message Type Registration 1275 (Section 15.3)). 1277 The Destination Up Message MUST contain a MAC Address Data Item 1278 (Section 13.7). 1280 The Destination Up Message SHOULD contain one or more of each of the 1281 following Data Items, with different values: 1283 o IPv4 Address (Section 13.8) 1285 o IPv6 Address (Section 13.9) 1287 The Destination Up Message MAY contain one of each of the following 1288 Data Items: 1290 o Maximum Data Rate (Receive) (Section 13.12) 1292 o Maximum Data Rate (Transmit) (Section 13.13) 1294 o Current Data Rate (Receive) (Section 13.14) 1296 o Current Data Rate (Transmit) (Section 13.15) 1298 o Latency (Section 13.16) 1300 The Destination Up Message MAY contain one of each of the following 1301 Data Items, if the Data Item is in use by the session: 1303 o Resources (Section 13.17) 1305 o Relative Link Quality (Receive) (Section 13.18) 1307 o Relative Link Quality (Transmit) (Section 13.19) 1309 o Maximum Transmission Unit (MTU) (Section 13.20) 1310 The Destination Up Message MAY contain one or more of each of the 1311 following Data Items, with different values: 1313 o IPv4 Attached Subnet (Section 13.10) 1315 o IPv6 Attached Subnet (Section 13.11) 1317 A router receiving a Destination Up Message allocates the necessary 1318 resources, creating an entry in the information base with the 1319 specifics (MAC Address, Latency, Data Rate, etc.) of the destination. 1320 The information about this destination will persist in the router's 1321 information base until a Destination Down Message (Section 12.15) is 1322 received, indicating that the modem has lost contact with the remote 1323 node, or the implementation transitions to the Session Termination 1324 state. 1326 12.12. Destination Up Response Message 1328 A router MUST send a Destination Up Response Message when a 1329 Destination Up Message (Section 12.11) is received. 1331 To construct a Destination Up Response Message, the Message Type 1332 value in the Message Header is set to 8 (see Message Type 1333 Registration (Section 15.3)). 1335 The Destination Up Response Message MUST contain one of each of the 1336 following Data Items: 1338 o MAC Address (Section 13.7) 1340 o Status (Section 13.1) 1342 A router that wishes to receive further information concerning the 1343 destination identified in the corresponding Destination Up Message 1344 MUST set the status code of the included Status Data Item to 0 1345 'Success', see Table 2. 1347 If the router has no interest in the destination identified in the 1348 corresponding Destination Up Message, then it MAY set the status code 1349 of the included Status Data Item to 1 'Not Interested'. 1351 A modem receiving a Destination Up Response Message containing a 1352 Status Data Item with status code of any value other than 0 'Success' 1353 MUST NOT send further Destination messages about the destination, 1354 e.g. Destination Down (Section 12.15) or Destination Update 1355 (Section 12.17) with the same MAC address. 1357 12.13. Destination Announce Message 1359 Usually a modem will discover the presence of one or more remote 1360 router/modem pairs and announce each destination's arrival by sending 1361 a corresponding Destination Up Message (Section 12.11) to the router. 1362 However, there may be times when a router wishes to express an 1363 interest in a destination that has yet to be announced, typically a 1364 multicast destination. Destination Announce Messages MAY be sent by 1365 a router to announce such an interest. 1367 A Destination Announce Message MAY also be sent by a router to 1368 request information concerning a destination in which it has 1369 previously declined interest, via the 1 'Not Interested' status code 1370 in a Destination Up Response Message (Section 12.12), see Table 2, or 1371 declared as 'down', via the Destination Down Message (Section 12.15). 1373 To construct a Destination Announce Message, the Message Type value 1374 in the Message Header is set to 9 (see Message Type Registration 1375 (Section 15.3)). 1377 The Destination Announce Message MUST contain a MAC Address Data Item 1378 (Section 13.7). 1380 The Destination Announce Message MAY contain zero or more of the 1381 following Data Items, with different values: 1383 o IPv4 Address (Section 13.8) 1385 o IPv6 Address (Section 13.9) 1387 One of the advantages of implementing DLEP is to leverage the modem's 1388 knowledge of the links between remote destinations allowing routers 1389 to avoid using probed neighbor discovery techniques, therefore modem 1390 implementations SHOULD announce available destinations via the 1391 Destination Up Message, rather than relying on Destination Announce 1392 Messages. 1394 12.14. Destination Announce Response Message 1396 A modem MUST send a Destination Announce Response Message when a 1397 Destination Announce Message (Section 12.13) is received. 1399 To construct a Destination Announce Response Message, the Message 1400 Type value in the Message Header is set to 10 (see Message Type 1401 Registration (Section 15.3)). 1403 The Destination Announce Response Message MUST contain one of each of 1404 the following Data Items: 1406 o MAC Address (Section 13.7) 1408 o Status (Section 13.1) 1410 The Destination Announce Response Message MAY contain one or more of 1411 each of the following Data Items, with different values: 1413 o IPv4 Address (Section 13.8) 1415 o IPv6 Address (Section 13.9) 1417 o IPv4 Attached Subnet (Section 13.10) 1419 o IPv6 Attached Subnet (Section 13.11) 1421 The Destination Announce Response Message MAY contain one of each of 1422 the following Data Items: 1424 o Maximum Data Rate (Receive) (Section 13.12) 1426 o Maximum Data Rate (Transmit) (Section 13.13) 1428 o Current Data Rate (Receive) (Section 13.14) 1430 o Current Data Rate (Transmit) (Section 13.15) 1432 o Latency (Section 13.16) 1434 The Destination Announce Response Message MAY contain one of each of 1435 the following Data Items, if the Data Item is in use by the session: 1437 o Resources (Section 13.17) 1439 o Relative Link Quality (Receive) (Section 13.18) 1441 o Relative Link Quality (Transmit) (Section 13.19) 1443 o Maximum Transmission Unit (MTU) (Section 13.20) 1445 If a modem is unable to report information immediately about the 1446 requested information, if the destination is not currently reachable, 1447 for example, the status code in the Status Data Item MUST be set to 2 1448 'Request Denied', see Table 2. 1450 After sending a Destination Announce Response Message containing a 1451 Status Data Item with status code of 0 'Success', a modem then 1452 announces changes to the link to the destination via Destination 1453 Update Messages. 1455 When a successful Destination Announce Response Message is received, 1456 the router should add knowledge of the available destination to its 1457 information base. 1459 12.15. Destination Down Message 1461 A modem MUST send a Destination Down Message to report when a 1462 destination (a remote node or a multicast group) is no longer 1463 reachable. 1465 A router MAY send a Destination Down Message to report when it no 1466 longer requires information concerning a destination. 1468 To construct a Destination Down Message, the Message Type value in 1469 the Message Header is set to 11 (see Message Type Registration 1470 (Section 15.3)). 1472 The Destination Down Message MUST contain a MAC Address Data Item 1473 (Section 13.7). 1475 It should be noted that both modem and router may send a Destination 1476 Down Message to their peer, regardless of which participant initially 1477 indicated the destination to be 'up'. 1479 12.16. Destination Down Response Message 1481 A Destination Down Response MUST be sent by the recipient of a 1482 Destination Down Message (Section 12.15) to confirm that the relevant 1483 data concerning the destination has been removed from the information 1484 base. 1486 To construct a Destination Down Response Message, the Message Type 1487 value in the Message Header is set to 12 (see Message Type 1488 Registration (Section 15.3)). 1490 The Destination Down Response Message MUST contain one of each of the 1491 following Data Items: 1493 o MAC Address (Section 13.7) 1495 o Status (Section 13.1) 1497 12.17. Destination Update Message 1499 A modem SHOULD send the Destination Update Message when it detects 1500 some change in the information base for a given destination (remote 1501 node or multicast group). Some examples of changes that would prompt 1502 a Destination Update Message are: 1504 o Change in link metrics (e.g., Data Rates) 1506 o Layer 3 addressing change 1508 To construct a Destination Update Message, the Message Type value in 1509 the Message Header is set to 13 (see Message Type Registration 1510 (Section 15.3)). 1512 The Destination Update Message MUST contain a MAC Address Data Item 1513 (Section 13.7). 1515 The Destination Update Message MAY contain one of each of the 1516 following Data Items: 1518 o Maximum Data Rate (Receive) (Section 13.12) 1520 o Maximum Data Rate (Transmit) (Section 13.13) 1522 o Current Data Rate (Receive) (Section 13.14) 1524 o Current Data Rate (Transmit) (Section 13.15) 1526 o Latency (Section 13.16) 1528 The Destination Update Message MAY contain one of each of the 1529 following Data Items, if the Data Item is in use by the session: 1531 o Resources (Section 13.17) 1533 o Relative Link Quality (Receive) (Section 13.18) 1535 o Relative Link Quality (Transmit) (Section 13.19) 1537 o Maximum Transmission Unit (MTU) (Section 13.20) 1539 The Destination Update Message MAY contain one or more of each of the 1540 following Data Items, with different values: 1542 o IPv4 Address (Section 13.8) 1544 o IPv6 Address (Section 13.9) 1546 o IPv4 Attached Subnet (Section 13.10) 1548 o IPv6 Attached Subnet (Section 13.11) 1550 Metrics supplied in this message overwrite metrics provided in a 1551 previously received Session or Destination Up Messages. 1553 It should be noted that this Message has no corresponding response. 1555 12.18. Link Characteristics Request Message 1557 The Link Characteristics Request Message MAY be sent by a router to 1558 request that the modem initiate changes for specific characteristics 1559 of the link. The request can reference either a real destination 1560 (e.g., a remote node), or a logical destination (e.g., a multicast 1561 group) within the network. 1563 To construct a Link Characteristics Request Message, the Message Type 1564 value in the Message Header is set to 14 (see Message Type 1565 Registration (Section 15.3)). 1567 The Link Characteristics Request Message MUST contain one of the 1568 following Data Items: 1570 o MAC Address (Section 13.7) 1572 The Link Characteristics Request Message MUST contain at least one of 1573 each of the following Data Items: 1575 o Current Data Rate (Receive) (Section 13.14) 1577 o Current Data Rate (Transmit) (Section 13.15) 1579 o Latency (Section 13.16) 1581 The Link Characteristics Request Message MAY contain either a Current 1582 Data Rate (CDRR or CDRT) Data Item to request a different datarate 1583 than is currently allocated, a Latency Data Item to request that 1584 traffic delay on the link not exceed the specified value, or both. 1586 The router sending a Link Characteristics Request Message should be 1587 aware that a request may take an extended period of time to complete. 1589 12.19. Link Characteristics Response Message 1591 A modem MUST send a Link Characteristics Response Message when a Link 1592 Characteristics Request Message (Section 12.18) is received. 1594 To construct a Link Characteristics Response Message, the Message 1595 Type value in the Message Header is set to 15 (see Message Type 1596 Registration (Section 15.3)). 1598 The Link Characteristics Response Message MUST contain one of each of 1599 the following Data Items: 1601 o MAC Address (Section 13.7) 1603 o Status (Section 13.1) 1605 The Link Characteristics Response Message SHOULD contain one of each 1606 of the following Data Items: 1608 o Maximum Data Rate (Receive) (Section 13.12) 1610 o Maximum Data Rate (Transmit) (Section 13.13) 1612 o Current Data Rate (Receive) (Section 13.14) 1614 o Current Data Rate (Transmit) (Section 13.15) 1616 o Latency (Section 13.16) 1618 The Link Characteristics Response Message MAY contain one of each of 1619 the following Data Items, if the Data Item is in use by the session: 1621 o Resources (Section 13.17) 1623 o Relative Link Quality (Receive) (Section 13.18) 1625 o Relative Link Quality (Transmit) (Section 13.19) 1627 o Maximum Transmission Unit (MTU) (Section 13.20) 1629 The Link Characteristics Response Message MUST contain a complete set 1630 of metric Data Items, referencing all metrics declared in the Session 1631 Initialization Response Message (Section 12.6). The values in the 1632 metric Data Items in the Link Characteristics Response Message MUST 1633 reflect the link characteristics after the request has been 1634 processed. 1636 If an implementation is not able to alter the characteristics of the 1637 link in the manner requested, then the status code of the Status Data 1638 Item MUST be set to 2 'Request Denied', see Table 2. 1640 12.20. Heartbeat Message 1642 A Heartbeat Message MUST be sent by a DLEP participant every N 1643 milliseconds, where N is defined in the Heartbeat Interval Data Item 1644 (Section 13.5) of the Session Initialization Message (Section 12.5) 1645 or Session Initialization Response Message (Section 12.6). 1647 To construct a Heartbeat Message, the Message Type value in the 1648 Message Header is set to 16 (see Message Type Registration 1649 (Section 15.3)). 1651 There are no valid Data Items for the Heartbeat Message. 1653 The Message is used by DLEP participants to detect when a DLEP 1654 session peer (either the modem or the router) is no longer 1655 communicating, see Section 7.3.1. 1657 13. DLEP Data Items 1659 Following is the list of core Data Items that MUST be recognized by a 1660 DLEP compliant implementation. As mentioned before, not all Data 1661 Items need be used during a session, but an implementation MUST 1662 correctly process these Data Items when correctly associated with a 1663 Signal or Message. 1665 The core DLEP Data Items are: 1667 +-------------+-----------------------------------------------------+ 1668 | Type Code | Description | 1669 +-------------+-----------------------------------------------------+ 1670 | 0 | Reserved | 1671 | 1 | Status (Section 13.1) | 1672 | 2 | IPv4 Connection Point (Section 13.2) | 1673 | 3 | IPv6 Connection Point (Section 13.3) | 1674 | 4 | Peer Type (Section 13.4) | 1675 | 5 | Heartbeat Interval (Section 13.5) | 1676 | 6 | Extensions Supported (Section 13.6) | 1677 | 7 | MAC Address (Section 13.7) | 1678 | 8 | IPv4 Address (Section 13.8) | 1679 | 9 | IPv6 Address (Section 13.9) | 1680 | 10 | IPv4 Attached Subnet (Section 13.10) | 1681 | 11 | IPv6 Attached Subnet (Section 13.11) | 1682 | 12 | Maximum Data Rate (Receive) (MDRR) (Section 13.12) | 1683 | 13 | Maximum Data Rate (Transmit) (MDRT) (Section 13.13) | 1684 | 14 | Current Data Rate (Receive) (CDRR) (Section 13.14) | 1685 | 15 | Current Data Rate (Transmit) (CDRT) (Section 13.15) | 1686 | 16 | Latency (Section 13.16) | 1687 | 17 | Resources (RES) (Section 13.17) | 1688 | 18 | Relative Link Quality (Receive) (RLQR) (Section | 1689 | | 13.18) | 1690 | 19 | Relative Link Quality (Transmit) (RLQT) (Section | 1691 | | 13.19) | 1692 | 20 | Maximum Transmission Unit (MTU) (Section 13.20) | 1693 | 21-65407 | Reserved for future extensions | 1694 | 65408-65534 | Private Use. Available for experiments | 1695 | 65535 | Reserved | 1696 +-------------+-----------------------------------------------------+ 1698 Table 1: DLEP Data Item types 1700 13.1. Status 1702 For the Session Termination Message (Section 12.9), the Status Data 1703 Item indicates a reason for the termination. For all response 1704 Messages, the Status Data Item is used to indicate the success or 1705 failure of the previously received Message. 1707 The Status Data Item includes an optional Text field that can be used 1708 to provide a textual description of the status. The use of the Text 1709 field is entirely up to the receiving implementation, e.g., it could 1710 be output to a log file or discarded. If no Text field is supplied 1711 with the Status Data Item, the Length field MUST be set to 1. 1713 The Status Data Item contains the following fields: 1715 0 1 2 3 1716 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1717 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1718 | Data Item Type | Length | 1719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1720 | Code | Text... : 1721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1723 Data Item Type: 1 1725 Length: 1 + Length of text, in octets 1727 Status Code: One of the codes defined in Table 2 below. 1729 Text: UTF-8 encoded string of UNICODE [RFC3629] characters, 1730 describing the cause, used for implementation defined purposes. 1731 Since this field is used for description, implementations SHOULD 1732 limit characters in this field to printable characters. 1734 An implementation MUST NOT assume the Text field is a NUL-terminated 1735 string of printable characters. 1737 +----------+-------------+------------------+-----------------------+ 1738 | Status | Failure | Description | Reason | 1739 | Code | Mode | | | 1740 +----------+-------------+------------------+-----------------------+ 1741 | 0 | Continue | Success | The Message was | 1742 | | | | processed | 1743 | | | | successfully. | 1744 | 1 | Continue | Not Interested | The receiver is not | 1745 | | | | interested in this | 1746 | | | | Message subject, e.g. | 1747 | | | | in a Destination Up | 1748 | | | | Response Message | 1749 | | | | (Section 12.12) to | 1750 | | | | indicate no further | 1751 | | | | Messages about the | 1752 | | | | destination. | 1753 | 2 | Continue | Request Denied | The receiver refuses | 1754 | | | | to complete the | 1755 | | | | request. | 1756 | 3 | Continue | Inconsistent | One or more Data | 1757 | | | Data | Items in the Message | 1758 | | | | describe a logically | 1759 | | | | inconsistent state in | 1760 | | | | the network. For | 1761 | | | | example, in the | 1762 | | | | Destination Up | 1763 | | | | Message (Section | 1764 | | | | 12.11) when an | 1765 | | | | announced subnet | 1766 | | | | clashes with an | 1767 | | | | existing destination | 1768 | | | | subnet. | 1769 | 4-111 | Continue | | Reserved for future | 1770 | | | | extensions. | 1771 | 112-127 | Continue | | Available for | 1772 | | | | experiments. | 1773 | 128 | Terminate | Unknown Message | The Message was not | 1774 | | | | recognized by the | 1775 | | | | implementation. | 1776 | 129 | Terminate | Unexpected | The Message was not | 1777 | | | Message | expected while the | 1778 | | | | device was in the | 1779 | | | | current state, e.g., | 1780 | | | | a Session | 1781 | | | | Initialization | 1782 | | | | Message (Section | 1783 | | | | 12.5) in the In- | 1784 | | | | Session state. | 1785 | 130 | Terminate | Invalid Data | One or more Data | 1786 | | | | Items in the Message | 1787 | | | | are invalid, | 1788 | | | | unexpected or | 1789 | | | | incorrectly | 1790 | | | | duplicated. | 1791 | 131 | Terminate | Invalid | The destination | 1792 | | | Destination | included in the | 1793 | | | | Message does not | 1794 | | | | match a previously | 1795 | | | | announced | 1796 | | | | destination. For | 1797 | | | | example, in the Link | 1798 | | | | Characteristic | 1799 | | | | Response Message | 1800 | | | | (Section 12.19). | 1801 | 132 | Terminate | Timed Out | The session has timed | 1802 | | | | out. | 1803 | 133-239 | Terminate | | Reserved for future | 1804 | | | | extensions. | 1805 | 240-254 | Terminate | | Available for | 1806 | | | | experiments. | 1807 | 255 | Terminate | | Reserved. | 1808 +----------+-------------+------------------+-----------------------+ 1810 Table 2: DLEP Status Codes 1812 13.2. IPv4 Connection Point 1814 The IPv4 Connection Point Data Item indicates the IPv4 address and, 1815 optionally, the TCP port number on the modem available for 1816 connections. If provided, the router MUST use this information to 1817 initiate the TCP connection to the modem. 1819 The IPv4 Connection Point Data Item contains the following fields: 1821 0 1 2 3 1822 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1823 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1824 | Data Item Type | Length | 1825 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1826 | Flags | IPv4 Address... : 1827 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1828 : ...cont. | TCP Port Number (optional) | 1829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1831 Data Item Type: 2 1833 Length: 5 (or 7 if TCP Port included) 1835 Flags: Flags field, defined below. 1837 IPv4 Address: The IPv4 address listening on the modem. 1839 TCP Port Number: TCP Port number on the modem. 1841 If the Length field is 7, the port number specified MUST be used to 1842 establish the TCP session. If the TCP Port Number is omitted, i.e. 1843 the Length field is 5, the router MUST use the DLEP well-known port 1844 number (Section 15.14) to establish the TCP connection. 1846 The Flags field is defined as: 1848 0 1 2 3 4 5 6 7 1849 +-+-+-+-+-+-+-+-+ 1850 | Reserved |T| 1851 +-+-+-+-+-+-+-+-+ 1853 T: Use TLS flag, indicating whether the TCP connection to the given 1854 address and port requires the use of TLS [RFC5246] (1), or not 1855 (0). 1857 Reserved: MUST be zero. Left for future assignment. 1859 13.3. IPv6 Connection Point 1861 The IPv6 Connection Point Data Item indicates the IPv6 address and, 1862 optionally, the TCP port number on the modem available for 1863 connections. If provided, the router MUST use this information to 1864 initiate the TCP connection to the modem. 1866 The IPv6 Connection Point Data Item contains the following fields: 1868 0 1 2 3 1869 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1871 | Data Item Type | Length | 1872 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1873 | Flags | IPv6 Address : 1874 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1875 : IPv6 Address : 1876 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1877 : IPv6 Address : 1878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1879 : IPv6 Address : 1880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1881 : ...cont. | TCP Port Number (optional) | 1882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1884 Data Item Type: 3 1886 Length: 17 (or 19 if TCP Port included) 1888 Flags: Flags field, defined below. 1890 IPv6 Address: The IPv6 address listening on the modem. 1892 TCP Port Number: TCP Port number on the modem. 1894 If the Length field is 19, the port number specified MUST be used to 1895 establish the TCP session. If the TCP Port Number is omitted, i.e. 1896 the Length field is 17, the router MUST use the DLEP well-known port 1897 number (Section 15.14) to establish the TCP connection. 1899 The Flags field is defined as: 1901 0 1 2 3 4 5 6 7 1902 +-+-+-+-+-+-+-+-+ 1903 | Reserved |T| 1904 +-+-+-+-+-+-+-+-+ 1905 T: Use TLS flag, indicating whether the TCP connection to the given 1906 address and port requires the use of TLS [RFC5246] (1), or not 1907 (0). 1909 Reserved: MUST be zero. Left for future assignment. 1911 13.4. Peer Type 1913 The Peer Type Data Item is used by the router and modem to give 1914 additional information as to its type and the properties of the over- 1915 the-air control-plane. 1917 With some devices, access to the shared RF medium is strongly 1918 controlled. One example of this would be satellite modems - where 1919 protocols, proprietary in nature, have been developed to insure a 1920 given modem has authorization to connect to the shared medium. 1921 Another example of this class of modems is governmental/military 1922 devices, where elaborate mechanisms have been developed to ensure 1923 that only authorized devices can connect to the shared medium. 1924 Contrasting with the above, there are modems where no such access 1925 control is used. An example of this class of modem would be one that 1926 supports the 802.11 ad-hoc mode of operation. The Secured Medium 1927 flag is used to indicate if access control is in place. 1929 The Peer Type Data Item includes a textual description of the peer 1930 that is envisioned to be used for informational purposes (e.g., as 1931 output in a display command). 1933 The Peer Type Data Item contains the following fields: 1935 0 1 2 3 1936 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1937 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1938 | Data Item Type | Length | 1939 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1940 | Flags | Description... : 1941 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1943 Data Item Type: 4 1945 Length: 1 + Length of Peer Type string, in octets. 1947 Flags: Flags field, defined below. 1949 Description: UTF-8 encoded string of UNICODE [RFC3629] characters. 1950 For example, a satellite modem might set this variable to 1951 "Satellite terminal". Since this Data Item is intended to provide 1952 additional information for display commands, sending 1953 implementations SHOULD limit the data to printable characters. 1955 An implementation MUST NOT assume the Description field is a NUL- 1956 terminated string of printable characters. 1958 The Flags field is defined as: 1960 0 1 2 3 4 5 6 7 1961 +-+-+-+-+-+-+-+-+ 1962 | Reserved |S| 1963 +-+-+-+-+-+-+-+-+ 1965 S: Secured Medium flag, used by a modem to indicate if the shared RF 1966 medium implements access control (1), or not (0). The Secured 1967 Medium flag only has meaning in Signals and Messages sent by a 1968 modem. 1970 Reserved: MUST be zero. Left for future assignment. 1972 13.5. Heartbeat Interval 1974 The Heartbeat Interval Data Item is used to specify a period in 1975 milliseconds for Heartbeat Messages (Section 12.20). 1977 The Heartbeat Interval Data Item contains the following fields: 1979 0 1 2 3 1980 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1981 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1982 | Data Item Type | Length | 1983 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1984 | Heartbeat Interval | 1985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1987 Data Item Type: 5 1989 Length: 4 1991 Heartbeat Interval: The interval in milliseconds, expressed as a 1992 32-bit unsigned integer, for Heartbeat Messages. This value MUST 1993 NOT be 0. 1995 As mentioned before, receipt of any valid DLEP Message MUST reset the 1996 heartbeat interval timer (e.g., valid DLEP Messages take the place 1997 of, and obviate the need for, additional Heartbeat Messages). 1999 13.6. Extensions Supported 2001 The Extensions Supported Data Item is used by the router and modem to 2002 negotiate additional optional functionality they are willing to 2003 support. The Extensions List is a concatenation of the types of each 2004 supported extension, found in the IANA DLEP Extensions repository. 2005 Each Extension Type definition includes which additional Signals and 2006 Data Items are supported. 2008 The Extensions Supported Data Item contains the following fields: 2010 0 1 2 3 2011 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2013 | Data Item Type | Length | 2014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2015 | Extensions List... : 2016 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2018 Data Item Type: 6 2020 Length: Length of the extensions list in octets. This is twice (2x) 2021 the number of extensions. 2023 Extension List: A list of extensions supported, identified by their 2024 2-octet value as listed in the extensions registry. 2026 13.7. MAC Address 2028 The MAC Address Data Item contains the address of the destination on 2029 the remote node. 2031 DLEP can support MAC addresses in either EUI-48 or EUI-64 format, 2032 with the restriction that all MAC addresses for a given DLEP session 2033 MUST be in the same format, and MUST be consistent with the MAC 2034 address format of the connected modem (e.g., if the modem is 2035 connected to the router with an EUI-48 MAC, all destination addresses 2036 via that modem MUST be expressed in EUI-48 format). 2038 Examples of a virtual destination would be a multicast MAC address, 2039 or the broadcast MAC (FF:FF:FF:FF:FF:FF). 2041 0 1 2 3 2042 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2044 | Data Item Type | Length | 2045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2046 | MAC Address : 2047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2048 : MAC Address : (if EUI-64 used) | 2049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2051 Data Item Type: 7 2053 Length: 6 for EUI-48 format, or 8 for EUI-64 format 2055 MAC Address: MAC Address of the destination. 2057 13.8. IPv4 Address 2059 When included in the Session Update Message, this Data Item contains 2060 the IPv4 address of the peer. When included in Destination Messages, 2061 this Data Item contains the IPv4 address of the destination. In 2062 either case, the Data Item also contains an indication of whether 2063 this is a new or existing address, or is a deletion of a previously 2064 known address. 2066 The IPv4 Address Data Item contains the following fields: 2068 0 1 2 3 2069 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2070 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2071 | Data Item Type | Length | 2072 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2073 | Flags | IPv4 Address : 2074 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2075 : ...cont. | 2076 +-+-+-+-+-+-+-+-+ 2078 Data Item Type: 8 2080 Length: 5 2082 Flags: Flags field, defined below. 2084 IPv4 Address: The IPv4 address of the destination or peer. 2086 The Flags field is defined as: 2088 0 1 2 3 4 5 6 7 2089 +-+-+-+-+-+-+-+-+ 2090 | Reserved |A| 2091 +-+-+-+-+-+-+-+-+ 2093 A: Add/Drop flag, indicating whether this is a new or existing 2094 address (1), or a withdrawal of an address (0). 2096 Reserved: MUST be zero. Reserved for future use. 2098 13.8.1. IPv4 Address Processing 2100 Processing of the IPv4 Address Data Item MUST be done within the 2101 context of the DLEP Peer session on which it is presented. 2103 The handling of erroneous or logically inconsistent conditions 2104 depends upon the type of the message that contains the data item: 2106 If the containing message is a Session Message, e.g., Session 2107 Initialization Message (Section 12.5), or Session Update Message 2108 (Section 12.7), the receiver of inconsistent information MUST issue a 2109 Session Termination Message (Section 12.9) containing a Status Data 2110 Item (Section 13.1) with status code set to 130 'Invalid Data', and 2111 transition to the Session Termination state. Examples of such 2112 conditions are: 2114 o An address Drop operation referencing an address that is not 2115 associated with the peer in the current session. 2117 o An address Add operation referencing an address that has already 2118 been added to the peer in the current session. 2120 If the containing message is a Destination Message, e.g., Destination 2121 Up Message (Section 12.11), or Destination Update Message 2122 (Section 12.17), the receiver of inconsistent information MAY issue 2123 the appropriate response message containing a Status Data Item, with 2124 status code set to 3 'Inconsistent Data', but MUST continue with 2125 session processing. Examples of such conditions are: 2127 o An address Add operation referencing an address that has already 2128 been added to the destination in the current session. 2130 o An address Add operation referencing an address that is associated 2131 with a different destination or the peer in the current session. 2133 o An address Add operation referencing an address that makes no 2134 sense, for example defined as not forwardable in [RFC6890]. 2136 o An address Drop operation referencing an address that is not 2137 associated with the destination in the current session. 2139 If no response message is appropriate, for example, the Destination 2140 Update Message, then the implementation MUST continue with session 2141 processing. 2143 Modems that do not track IPv4 addresses MUST silently ignore IPv4 2144 Address Data Items. 2146 13.9. IPv6 Address 2148 When included in the Session Update Message, this Data Item contains 2149 the IPv6 address of the peer. When included in Destination Messages, 2150 this Data Item contains the IPv6 address of the destination. In 2151 either case, the Data Item also contains an indication of whether 2152 this is a new or existing address, or is a deletion of a previously 2153 known address. 2155 The IPv6 Address Data Item contains the following fields: 2157 0 1 2 3 2158 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2160 | Data Item Type | Length | 2161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2162 | Flags | IPv6 Address : 2163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2164 : IPv6 Address : 2165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2166 : IPv6 Address : 2167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2168 : IPv6 Address : 2169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2170 : IPv6 Address | 2171 +-+-+-+-+-+-+-+-+ 2173 Data Item Type: 9 2175 Length: 17 2177 Flags: Flags field, defined below. 2179 IPv6 Address: IPv6 Address of the destination or peer. 2181 The Flags field is defined as: 2183 0 1 2 3 4 5 6 7 2184 +-+-+-+-+-+-+-+-+ 2185 | Reserved |A| 2186 +-+-+-+-+-+-+-+-+ 2188 A: Add/Drop flag, indicating whether this is a new or existing 2189 address (1), or a withdrawal of an address (0). 2191 Reserved: MUST be zero. Reserved for future use. 2193 13.9.1. IPv6 Address Processing 2195 Processing of the IPv6 Address Data Item MUST be done within the 2196 context of the DLEP Peer session on which it is presented. 2198 The handling of erroneous or logically inconsistent conditions 2199 depends upon the type of the message that contains the data item: 2201 If the containing message is a Session Message, e.g., Session 2202 Initialization Message (Section 12.5), or Session Update Message 2203 (Section 12.7), the receiver of inconsistent information MUST issue a 2204 Session Termination Message (Section 12.9) containing a Status Data 2205 Item (Section 13.1) with status code set to 130 'Invalid Data', and 2206 transition to the Session Termination state. Examples of such 2207 conditions are: 2209 o An address Drop operation referencing an address that is not 2210 associated with the peer in the current session. 2212 o An address Add operation referencing an address that has already 2213 been added to the peer in the current session. 2215 If the containing message is a Destination Message, e.g., Destination 2216 Up Message (Section 12.11), or Destination Update Message 2217 (Section 12.17), the receiver of inconsistent information MAY issue 2218 the appropriate response message containing a Status Data Item, with 2219 status code set to 3 'Inconsistent Data', but MUST continue with 2220 session processing. Examples of such conditions are: 2222 o An address Add operation referencing an address that has already 2223 been added to the destination in the current session. 2225 o An address Add operation referencing an address that is associated 2226 with a different destination or the peer in the current session. 2228 o An address Add operation referencing an address that makes no 2229 sense, for example defined as not forwardable in [RFC6890]. 2231 o An address Drop operation referencing an address that is not 2232 associated with the destination in the current session. 2234 If no response message is appropriate, for example, the Destination 2235 Update Message, then the implementation MUST continue with session 2236 processing. 2238 Modems that do not track IPv6 addresses MUST silently ignore IPv6 2239 Address Data Items. 2241 13.10. IPv4 Attached Subnet 2243 The DLEP IPv4 Attached Subnet allows a device to declare that it has 2244 an IPv4 subnet (e.g., a stub network) attached, that it has become 2245 aware of an IPv4 subnet being present at a remote destination, or 2246 that it has become aware of the loss of a subnet at the remote 2247 destination. 2249 The DLEP IPv4 Attached Subnet Data Item contains the following 2250 fields: 2252 0 1 2 3 2253 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2255 | Data Item Type | Length | 2256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2257 | Flags | IPv4 Attached Subnet : 2258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2259 : ...cont. |Prefix Length | 2260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2262 Data Item Type: 10 2264 Length: 6 2266 Flags: Flags field, defined below. 2268 IPv4 Subnet: The IPv4 subnet reachable at the destination. 2270 Prefix Length: Length of the prefix (0-32) for the IPv4 subnet. A 2271 prefix length outside the specified range MUST be considered as 2272 invalid. 2274 The Flags field is defined as: 2276 0 1 2 3 4 5 6 7 2277 +-+-+-+-+-+-+-+-+ 2278 | Reserved |A| 2279 +-+-+-+-+-+-+-+-+ 2281 A: Add/Drop flag, indicating whether this is a new or existing subnet 2282 address (1), or a withdrawal of a subnet address (0). 2284 Reserved: MUST be zero. Reserved for future use. 2286 13.10.1. IPv4 Attached Subnet Processing 2288 Processing of the IPv4 Attached Subnet Data Item MUST be done within 2289 the context of the DLEP Peer session on which it is presented. 2291 If the containing message is a Session Message, e.g., Session 2292 Initialization Message (Section 12.5), or Session Update Message 2293 (Section 12.7), the receiver of inconsistent information MUST issue a 2294 Session Termination Message (Section 12.9) containing a Status Data 2295 Item (Section 13.1) with status code set to 130 'Invalid Data', and 2296 transition to the Session Termination state. Examples of such 2297 conditions are: 2299 o A subnet Drop operation referencing a subnet that is not 2300 associated with the peer in the current session. 2302 o A subnet Add operation referencing a subnet that has already been 2303 added to the peer in the current session. 2305 If the containing message is a Destination Message, e.g., Destination 2306 Up Message (Section 12.11), or Destination Update Message 2307 (Section 12.17), the receiver of inconsistent information MAY issue 2308 the appropriate response message containing a Status Data Item, with 2309 status code set to 3 'Inconsistent Data', but MUST continue with 2310 session processing. Examples of such conditions are: 2312 o A subnet Add operation referencing a subnet that has already been 2313 added to the destination in the current session. 2315 o A subnet Add operation referencing a subnet that is associated 2316 with a different destination in the current session. 2318 o An subnet Add operation referencing an subnet that makes no sense, 2319 for example defined as not forwardable in [RFC6890]. 2321 o A subnet Drop operation referencing a subnet that is not 2322 associated with the destination in the current session. 2324 If no response message is appropriate, for example, the Destination 2325 Update Message, then the implementation MUST continue with session 2326 processing. 2328 Modems that do not track IPv4 subnets MUST silently ignore IPv4 2329 Attached Subnet Data Items. 2331 13.11. IPv6 Attached Subnet 2333 The DLEP IPv6 Attached Subnet allows a device to declare that it has 2334 an IPv6 subnet (e.g., a stub network) attached, that it has become 2335 aware of an IPv6 subnet being present at a remote destination, or 2336 that it has become aware of the loss of a subnet at the remote 2337 destination. 2339 The DLEP IPv6 Attached Subnet Data Item contains the following 2340 fields: 2342 0 1 2 3 2343 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2345 | Data Item Type | Length | 2346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2347 | Flags | IPv6 Attached Subnet : 2348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2349 : IPv6 Attached Subnet : 2350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2351 : IPv6 Attached Subnet : 2352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2353 : IPv6 Attached Subnet : 2354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2355 : ...cont. | Prefix Len. | 2356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2358 Data Item Type: 11 2360 Length: 18 2362 Flags: Flags field, defined below. 2364 IPv6 Attached Subnet: The IPv6 subnet reachable at the destination. 2366 Prefix Length: Length of the prefix (0-128) for the IPv6 subnet. A 2367 prefix length outside the specified range MUST be considered as 2368 invalid. 2370 The Flags field is defined as: 2372 0 1 2 3 4 5 6 7 2373 +-+-+-+-+-+-+-+-+ 2374 | Reserved |A| 2375 +-+-+-+-+-+-+-+-+ 2377 A: Add/Drop flag, indicating whether this is a new or existing subnet 2378 address (1), or a withdrawal of a subnet address (0). 2380 Reserved: MUST be zero. Reserved for future use. 2382 13.11.1. IPv6 Attached Subnet Processing 2384 Processing of the IPv6 Attached Subnet Data Item MUST be done within 2385 the context of the DLEP Peer session on which it is presented. 2387 If the containing message is a Session Message, e.g., Session 2388 Initialization Message (Section 12.5), or Session Update Message 2389 (Section 12.7), the receiver of inconsistent information MUST issue a 2390 Session Termination Message (Section 12.9) containing a Status Data 2391 Item (Section 13.1) with status code set to 130 'Invalid Data', and 2392 transition to the Session Termination state. Examples of such 2393 conditions are: 2395 o A subnet Drop operation referencing a subnet that is not 2396 associated with the peer in the current session. 2398 o A subnet Add operation referencing a subnet that has already been 2399 added to the peer in the current session. 2401 If the containing message is a Destination Message, e.g., Destination 2402 Up Message (Section 12.11), or Destination Update Message 2403 (Section 12.17), the receiver of inconsistent information MAY issue 2404 the appropriate response message containing a Status Data Item, with 2405 status code set to 3 'Inconsistent Data', but MUST continue with 2406 session processing. Examples of such conditions are: 2408 o A subnet Add operation referencing a subnet that has already been 2409 added to the destination in the current session. 2411 o A subnet Add operation referencing a subnet that is associated 2412 with a different destination in the current session. 2414 o An subnet Add operation referencing an subnet that makes no sense, 2415 for example defined as not forwardable in [RFC6890]. 2417 o A subnet Drop operation referencing a subnet that is not 2418 associated with the destination in the current session. 2420 If no response message is appropriate, for example, the Destination 2421 Update Message, then the implementation MUST continue with session 2422 processing. 2424 Modems that do not track IPv6 subnets MUST silently ignore IPv6 2425 Attached Subnet Data Items. 2427 13.12. Maximum Data Rate (Receive) 2429 The Maximum Data Rate (Receive) (MDRR) Data Item is used to indicate 2430 the maximum theoretical data rate, in bits per second, that can be 2431 achieved while receiving data on the link. 2433 The Maximum Data Rate (Receive) Data Item contains the following 2434 fields: 2436 0 1 2 3 2437 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2439 | Data Item Type | Length | 2440 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2441 | MDRR (bps) : 2442 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2443 : MDRR (bps) | 2444 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2446 Data Item Type: 12 2448 Length: 8 2450 Maximum Data Rate (Receive): A 64-bit unsigned integer, representing 2451 the maximum theoretical data rate, in bits per second (bps), that 2452 can be achieved while receiving on the link. 2454 13.13. Maximum Data Rate (Transmit) 2456 The Maximum Data Rate (Transmit) (MDRT) Data Item is used to indicate 2457 the maximum theoretical data rate, in bits per second, that can be 2458 achieved while transmitting data on the link. 2460 The Maximum Data Rate (Transmit) Data Item contains the following 2461 fields: 2463 0 1 2 3 2464 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2466 | Data Item Type | Length | 2467 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2468 | MDRT (bps) : 2469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2470 : MDRT (bps) | 2471 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2473 Data Item Type: 13 2475 Length: 8 2477 Maximum Data Rate (Transmit): A 64-bit unsigned integer, 2478 representing the maximum theoretical data rate, in bits per second 2479 (bps), that can be achieved while transmitting on the link. 2481 13.14. Current Data Rate (Receive) 2483 The Current Data Rate (Receive) (CDRR) Data Item is used to indicate 2484 the rate at which the link is currently operating for receiving 2485 traffic. 2487 When used in the Link Characteristics Request Message 2488 (Section 12.18), Current Data Rate (Receive) represents the desired 2489 receive rate, in bits per second, on the link. 2491 The Current Data Rate (Receive) Data Item contains the following 2492 fields: 2494 0 1 2 3 2495 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2497 | Data Item Type | Length | 2498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2499 | CDRR (bps) : 2500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2501 : CDRR (bps) | 2502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2504 Data Item Type: 14 2506 Length: 8 2508 Current Data Rate (Receive): A 64-bit unsigned integer, representing 2509 the current data rate, in bits per second, that can currently be 2510 achieved while receiving traffic on the link. 2512 If there is no distinction between Current Data Rate (Receive) and 2513 Maximum Data Rate (Receive) (Section 13.12), Current Data Rate 2514 (Receive) MUST be set equal to the Maximum Data Rate (Receive). The 2515 Current Data Rate (Receive) MUST NOT exceed the Maximum Data Rate 2516 (Receive). 2518 13.15. Current Data Rate (Transmit) 2520 The Current Data Rate (Transmit) (CDRT) Data Item is used to indicate 2521 the rate at which the link is currently operating for transmitting 2522 traffic. 2524 When used in the Link Characteristics Request Message 2525 (Section 12.18), Current Data Rate (Transmit) represents the desired 2526 transmit rate, in bits per second, on the link. 2528 The Current Data Rate (Transmit) Data Item contains the following 2529 fields: 2531 0 1 2 3 2532 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2534 | Data Item Type | Length | 2535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2536 | CDRT (bps) : 2537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2538 : CDRT (bps) | 2539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2541 Data Item Type: 15 2543 Length: 8 2545 Current Data Rate (Transmit): A 64-bit unsigned integer, 2546 representing the current data rate, in bits per second, that can 2547 currently be achieved while transmitting traffic on the link. 2549 If there is no distinction between Current Data Rate (Transmit) and 2550 Maximum Data Rate (Transmit) (Section 13.13), Current Data Rate 2551 (Transmit) MUST be set equal to the Maximum Data Rate (Transmit). 2552 The Current Data Rate (Transmit) MUST NOT exceed the Maximum Data 2553 Rate (Transmit). 2555 13.16. Latency 2557 The Latency Data Item is used to indicate the amount of latency, in 2558 microseconds, on the link. 2560 The Latency value is reported as transmission delay. The calculation 2561 of latency is implementation dependent. For example, the latency may 2562 be a running average calculated from the internal queuing. 2564 The Latency Data Item contains the following fields: 2566 0 1 2 3 2567 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2569 | Data Item Type | Length | 2570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2571 | Latency : 2572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2573 : Latency | 2574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2576 Data Item Type: 16 2578 Length: 8 2580 Latency: A 64-bit unsigned integer, representing the transmission 2581 delay, in microseconds, that a packet encounters as it is 2582 transmitted over the link. 2584 13.17. Resources 2586 The Resources (RES) Data Item is used to indicate the amount of 2587 finite resources available for data transmission and reception at the 2588 destination as a percentage, with 0 meaning 'no resources remaining', 2589 and 100 meaning 'a full supply', assuming that when Resources reaches 2590 0 data transmission and/or reception will cease. 2592 An example of such resources might be battery life, but could equally 2593 be magic beans. The list of resources that might be considered is 2594 beyond the scope of this document, and is left to implementations to 2595 decide. 2597 This Data Item is designed to be used as an indication of some 2598 capability of the modem and/or router at the destination. 2600 The Resources Data Item contains the following fields: 2602 0 1 2 3 2603 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2604 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2605 | Data Item Type | Length | 2606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2607 | RES | 2608 +-+-+-+-+-+-+-+-+ 2610 Data Item Type: 17 2612 Length: 1 2614 Resources: An 8-bit unsigned integer percentage, 0-100, representing 2615 the amount of resources available. Any value greater than 100 2616 MUST be considered as invalid. 2618 If a device cannot calculate Resources, this Data Item MUST NOT be 2619 issued. 2621 13.18. Relative Link Quality (Receive) 2623 The Relative Link Quality (Receive) (RLQR) Data Item is used to 2624 indicate the quality of the link to a destination for receiving 2625 traffic, with 0 meaning 'worst quality', and 100 meaning 'best 2626 quality'. 2628 Quality in this context is defined as an indication of the stability 2629 of a link for reception; a destination with high Relative Link 2630 Quality (Receive) is expected to have generally stable DLEP metrics, 2631 and the metrics of a destination with low Relative Link Quality 2632 (Receive) can be expected to rapidly fluctuate over a wide range. 2634 The Relative Link Quality (Receive) Data Item contains the following 2635 fields: 2637 0 1 2 3 2638 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2640 | Data Item Type | Length | 2641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2642 | RLQR | 2643 +-+-+-+-+-+-+-+-+ 2645 Data Item Type: 18 2647 Length: 1 2648 Relative Link Quality (Receive): A non-dimensional unsigned 8-bit 2649 integer, 0-100, representing relative quality of the link for 2650 receiving traffic. Any value greater than 100 MUST be considered 2651 as invalid. 2653 If a device cannot calculate the Relative Link Quality (Receive), 2654 this Data Item MUST NOT be issued. 2656 13.19. Relative Link Quality (Transmit) 2658 The Relative Link Quality (Transmit) (RLQT) Data Item is used to 2659 indicate the quality of the link to a destination for transmitting 2660 traffic, with 0 meaning 'worst quality', and 100 meaning 'best 2661 quality'. 2663 Quality in this context is defined as an indication of the stability 2664 of a link for transmission; a destination with high Relative Link 2665 Quality (Transmit) is expected to have generally stable DLEP metrics, 2666 and the metrics of a destination with low Relative Link Quality 2667 (Transmit) can be expected to rapidly fluctuate over a wide range. 2669 The Relative Link Quality (Transmit) Data Item contains the following 2670 fields: 2672 0 1 2 3 2673 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2675 | Data Item Type | Length | 2676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2677 | RLQT | 2678 +-+-+-+-+-+-+-+-+ 2680 Data Item Type: 19 2682 Length: 1 2684 Relative Link Quality (Transmit): A non-dimensional unsigned 8-bit 2685 integer, 0-100, representing relative quality of the link for 2686 transmitting traffic. Any value greater than 100 MUST be 2687 considered as invalid. 2689 If a device cannot calculate the Relative Link Quality (Transmit), 2690 this Data Item MUST NOT be issued. 2692 13.20. Maximum Transmission Unit (MTU) 2694 The Maximum Transmission Unit (MTU) Data Item is used to indicate the 2695 maximum size, in octets, of an IP packet that can be transmitted 2696 without fragmentation, including headers, but excluding any lower 2697 layer headers. 2699 The Maximum Transmission Unit Data Item contains the following 2700 fields: 2702 0 1 2 3 2703 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2705 | Data Item Type | Length | 2706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2707 | MTU | 2708 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2710 Data Item Type: 20 2712 Length: 2 2714 Maximum Transmission Unit: The maximum size, in octets, of an IP 2715 packet that can be transmitted without fragmentation, including 2716 headers, but excluding any lower layer headers. 2718 If a device cannot calculate the Maximum Transmission Unit, this Data 2719 Item MUST NOT be issued. 2721 14. Security Considerations 2723 The potential security concerns when using DLEP are: 2725 1. An attacker might pretend to be a DLEP participant, either at 2726 DLEP session initialization, or by injection of DLEP Messages 2727 once a session has been established. 2729 2. DLEP Data Items could be altered by an attacker, causing the 2730 receiving implementation to inappropriately alter its information 2731 base concerning network status. 2733 3. An attacker could join an unsecured radio network and inject 2734 over-the-air signals that maliciously influence the information 2735 reported by a DLEP modem, causing a router to forward traffic to 2736 an inappropriate destination. 2738 The implications of attacks on DLEP peers are directly proportional 2739 to the extent to which DLEP data is used within the control plane. 2741 While the use of DLEP data in other control plane components is out 2742 of scope for this document, as an example, if DLEP statistics are 2743 incorporated into route cost calculations, adversaries masquerading 2744 as a DLEP peer, and injecting malicious data via DLEP, could cause 2745 suboptimal route selection, adversely impacting network performance. 2746 Similar issues can arise if DLEP data is used as an input to policing 2747 algorithms - injection of malicious data via DLEP can cause those 2748 policing algorithms to make incorrect decisions, degrading network 2749 throughput. 2751 For these reasons, security of the DLEP transport must be considered 2752 at both the transport layer, and at Layer 2. 2754 At the transport layer, implementations of DLEP SHOULD implement, and 2755 use, TLS [RFC5246] to protect the TCP session. The "dedicated 2756 deployments" discussed in Implementation Scenarios (Section 4) MAY 2757 consider use of DLEP without TLS. For all "networked deployments" 2758 (again, discussed in Implementation Scenarios), implementation and 2759 use of TLS is STRONGLY RECOMMENDED. 2761 When TLS is in use, each peer SHOULD check the validity of 2762 credentials presented by the other peer during TLS session 2763 establishment. Mobile implementations MAY need to consider use of 2764 pre-shared keys for credentials; implementations following the 2765 "networked deployment" model described in Implementation Scenarios 2766 SHOULD refer to [RFC7525] for additional details. 2768 At layer 2 - since DLEP is restricted to operation over a single 2769 (possibly logical) hop, implementations SHOULD also secure the Layer 2770 2 link. Examples of technologies that can be deployed to secure the 2771 Layer 2 link include [IEEE-802.1AE] and [IEEE-802.1X]. 2773 By examining the Secured Medium flag in the Peer Type Data Item 2774 (Section 13.4), a router can decide if it is able to trust the 2775 information supplied via a DLEP modem. If this is not the case, then 2776 the router SHOULD consider restricting the size of attached subnets, 2777 announced in IPv4 Attached Subnet Data Items (Section 13.10) and/or 2778 IPv6 Attached Subnet Data Items (Section 13.11), that are considered 2779 for route selection. 2781 To avoid potential denial of service attack, it is RECOMMENDED that 2782 implementations using the Peer Discovery mechanism maintain an 2783 information base of hosts that persistently fail Session 2784 Initialization having provided an acceptable Peer Discovery Signal, 2785 and ignore subsequent Peer Discovery Signals from such hosts. 2787 This specification does not address security of the data plane, as it 2788 (the data plane) is not affected, and standard security procedures 2789 can be employed. 2791 15. IANA Considerations 2793 15.1. Registrations 2795 Upon approval of this document, IANA is requested to create a new 2796 protocol registry for Dynamic Link Exchange Protocol (DLEP). The 2797 remainder of this section requests the creation of new DLEP specific 2798 registries. 2800 15.2. Signal Type Registration 2802 Upon approval of this document, IANA is requested to create a new 2803 DLEP registry, named "Signal Type Values". 2805 The following table provides initial registry values and the 2806 [RFC5226] defined policies that should apply to the registry: 2808 +--------------+-------------------------+ 2809 | Type Code | Description/Policy | 2810 +--------------+-------------------------+ 2811 | 0 | Reserved | 2812 | 1 | Peer Discovery Signal | 2813 | 2 | Peer Offer Signal | 2814 | 3-65519 | Specification Required | 2815 | 65520-65534 | Private Use | 2816 | 65535 | Reserved | 2817 +--------------+-------------------------+ 2819 15.3. Message Type Registration 2821 Upon approval of this document, IANA is requested to create a new 2822 DLEP registry, named "Message Type Values". 2824 The following table provides initial registry values and the 2825 [RFC5226] defined policies that should apply to the registry: 2827 +--------------+------------------------------------------+ 2828 | Type Code | Description/Policy | 2829 +--------------+------------------------------------------+ 2830 | 0 | Reserved | 2831 | 1 | Session Initialization Message | 2832 | 2 | Session Initialization Response Message | 2833 | 3 | Session Update Message | 2834 | 4 | Session Update Response Message | 2835 | 5 | Session Termination Message | 2836 | 6 | Session Termination Response Message | 2837 | 7 | Destination Up Message | 2838 | 8 | Destination Up Response Message | 2839 | 9 | Destination Announce Message | 2840 | 10 | Destination Announce Response Message | 2841 | 11 | Destination Down Message | 2842 | 12 | Destination Down Response Message | 2843 | 13 | Destination Update Message | 2844 | 14 | Link Characteristics Request Message | 2845 | 15 | Link Characteristics Response Message | 2846 | 16 | Heartbeat Message | 2847 | 17-65519 | Specification Required | 2848 | 65520-65534 | Private Use | 2849 | 65535 | Reserved | 2850 +--------------+------------------------------------------+ 2852 15.4. DLEP Data Item Registrations 2854 Upon approval of this document, IANA is requested to create a new 2855 DLEP registry, named "Data Item Type Values". 2857 The following table provides initial registry values and the 2858 [RFC5226] defined policies that should apply to the registry: 2860 +-------------------+------------------------------------------+ 2861 | Type Code | Description/Policy | 2862 +-------------------+------------------------------------------+ 2863 | 0 | Reserved | 2864 | 1 | Status | 2865 | 2 | IPv4 Connection Point | 2866 | 3 | IPv6 Connection Point | 2867 | 4 | Peer Type | 2868 | 5 | Heartbeat Interval | 2869 | 6 | Extensions Supported | 2870 | 7 | MAC Address | 2871 | 8 | IPv4 Address | 2872 | 9 | IPv6 Address | 2873 | 10 | IPv4 Attached Subnet | 2874 | 11 | IPv6 Attached Subnet | 2875 | 12 | Maximum Data Rate (Receive) (MDRR) | 2876 | 13 | Maximum Data Rate (Transmit) (MDRT) | 2877 | 14 | Current Data Rate (Receive) (CDRR) | 2878 | 15 | Current Data Rate (Transmit) (CDRT) | 2879 | 16 | Latency | 2880 | 17 | Resources (RES) | 2881 | 18 | Relative Link Quality (Receive) (RLQR) | 2882 | 19 | Relative Link Quality (Transmit) (RLQT) | 2883 | 20 | Maximum Transmission Unit (MTU) | 2884 | 21-65407 | Specification Required | 2885 | 65408-65534 | Private Use | 2886 | 65535 | Reserved | 2887 +-------------------+------------------------------------------+ 2889 15.5. DLEP Status Code Registrations 2891 Upon approval of this document, IANA is requested to create a new 2892 DLEP registry, named "Status Code Values". 2894 The following table provides initial registry values and the 2895 [RFC5226] defined policies that should apply to the registry: 2897 +--------------+---------------+-------------------------+ 2898 | Status Code | Failure Mode | Description/Policy | 2899 +--------------+---------------+-------------------------+ 2900 | 0 | Continue | Success | 2901 | 1 | Continue | Not Interested | 2902 | 2 | Continue | Request Denied | 2903 | 3 | Continue | Inconsistent Data | 2904 | 4-111 | Continue | Specification Required | 2905 | 112-127 | Continue | Private Use | 2906 | 128 | Terminate | Unknown Message | 2907 | 129 | Terminate | Unexpected Message | 2908 | 130 | Terminate | Invalid Data | 2909 | 131 | Terminate | Invalid Destination | 2910 | 132 | Terminate | Timed Out | 2911 | 133-239 | Terminate | Specification Required | 2912 | 240-254 | Terminate | Private Use | 2913 | 255 | Terminate | Reserved | 2914 +--------------+---------------+-------------------------+ 2916 15.6. DLEP Extensions Registrations 2918 Upon approval of this document, IANA is requested to create a new 2919 DLEP registry, named "Extension Type Values". 2921 The following table provides initial registry values and the 2922 [RFC5226] defined policies that should apply to the registry: 2924 +--------------+---------------------------+ 2925 | Code | Description/Policy | 2926 +--------------+---------------------------+ 2927 | 0 | Reserved | 2928 | 1-65519 | Specification Required | 2929 | 65520-65534 | Private Use | 2930 | 65535 | Reserved | 2931 +--------------+---------------------------+ 2933 Table 3: DLEP Extension types 2935 15.7. DLEP IPv4 Connection Point Flags 2937 Upon approval of this document, IANA is requested to create a new 2938 DLEP registry, named "IPv4 Connection Point Flags". 2940 The following table provides initial registry values and the 2941 [RFC5226] defined policies that should apply to the registry: 2943 +------------+------------------------------------+ 2944 | Bit | Description/Policy | 2945 +------------+------------------------------------+ 2946 | 0-6 | Unassigned/Specification Required | 2947 | 7 | Use TLS [RFC5246] indicator | 2948 +------------+------------------------------------+ 2950 15.8. DLEP IPv6 Connection Point Flags 2952 Upon approval of this document, IANA is requested to create a new 2953 DLEP registry, named "IPv6 Connection Point Flags". 2955 The following table provides initial registry values and the 2956 [RFC5226] defined policies that should apply to the registry: 2958 +------------+------------------------------------+ 2959 | Bit | Description/Policy | 2960 +------------+------------------------------------+ 2961 | 0-6 | Unassigned/Specification Required | 2962 | 7 | Use TLS [RFC5246] indicator | 2963 +------------+------------------------------------+ 2965 15.9. DLEP Peer Type Flag 2967 Upon approval of this document, IANA is requested to create a new 2968 DLEP registry, named "Peer Type Flags". 2970 The following table provides initial registry values and the 2971 [RFC5226] defined policies that should apply to the registry: 2973 +------------+------------------------------------+ 2974 | Bit | Description/Policy | 2975 +------------+------------------------------------+ 2976 | 0-6 | Unassigned/Specification Required | 2977 | 7 | Secured Medium indicator | 2978 +------------+------------------------------------+ 2980 15.10. DLEP IPv4 Address Flag 2982 Upon approval of this document, IANA is requested to create a new 2983 DLEP registry, named "IPv4 Address Flags". 2985 The following table provides initial registry values and the 2986 [RFC5226] defined policies that should apply to the registry: 2988 +------------+------------------------------------+ 2989 | Bit | Description/Policy | 2990 +------------+------------------------------------+ 2991 | 0-6 | Unassigned/Specification Required | 2992 | 7 | Add/Drop indicator | 2993 +------------+------------------------------------+ 2995 15.11. DLEP IPv6 Address Flag 2997 Upon approval of this document, IANA is requested to create a new 2998 DLEP registry, named "IPv6 Address Flags". 3000 The following table provides initial registry values and the 3001 [RFC5226] defined policies that should apply to the registry: 3003 +------------+------------------------------------+ 3004 | Bit | Description/Policy | 3005 +------------+------------------------------------+ 3006 | 0-6 | Unassigned/Specification Required | 3007 | 7 | Add/Drop indicator | 3008 +------------+------------------------------------+ 3010 15.12. DLEP IPv4 Attached Subnet Flag 3012 Upon approval of this document, IANA is requested to create a new 3013 DLEP registry, named "IPv4 Attached Subnet Flags". 3015 The following table provides initial registry values and the 3016 [RFC5226] defined policies that should apply to the registry: 3018 +------------+------------------------------------+ 3019 | Bit | Description/Policy | 3020 +------------+------------------------------------+ 3021 | 0-6 | Unassigned/Specification Required | 3022 | 7 | Add/Drop indicator | 3023 +------------+------------------------------------+ 3025 15.13. DLEP IPv6 Attached Subnet Flag 3027 Upon approval of this document, IANA is requested to create a new 3028 DLEP registry, named "IPv6 Attached Subnet Flags". 3030 The following table provides initial registry values and the 3031 [RFC5226] defined policies that should apply to the registry: 3033 +------------+------------------------------------+ 3034 | Bit | Description/Policy | 3035 +------------+------------------------------------+ 3036 | 0-6 | Unassigned/Specification Required | 3037 | 7 | Add/Drop indicator | 3038 +------------+------------------------------------+ 3040 15.14. DLEP Well-known Port 3042 Upon approval of this document, IANA is requested to assign a single 3043 value in the "Service Name and Transport Protocol Port Number 3044 Registry" found at https://www.iana.org/assignments/service-names- 3045 port-numbers/service-names-port-numbers.xhtml for use by "DLEP", as 3046 defined in this document. This assignment should be valid for TCP 3047 and UDP. 3049 15.15. DLEP IPv4 Link-local Multicast Address 3051 Upon approval of this document, IANA is requested to assign an IPv4 3052 multicast address registry found at http://www.iana.org/assignments/ 3053 multicast-addresses for use as the "IPv4 DLEP Discovery Address". 3055 15.16. DLEP IPv6 Link-local Multicast Address 3057 Upon approval of this document, IANA is requested to assign an IPv6 3058 multicast address registry found at http://www.iana.org/assignments/ 3059 multicast-addresses for use as the "IPv6 DLEP Discovery Address". 3061 16. Acknowledgments 3063 We would like to acknowledge and thank the members of the DLEP design 3064 team, who have provided invaluable insight. The members of the 3065 design team are: Teco Boot, Bow-Nan Cheng, John Dowdell, and Henning 3066 Rogge. 3068 We would also like to acknowledge the influence and contributions of 3069 Greg Harrison, Chris Olsen, Martin Duke, Subir Das, Jaewon Kang, 3070 Vikram Kaul, Nelson Powell, Lou Berger, and Victoria Pritchard. 3072 17. References 3074 17.1. Normative References 3076 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3077 Requirement Levels", BCP 14, RFC 2119, 3078 DOI 10.17487/RFC2119, March 1997, 3079 . 3081 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 3082 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 3083 2003, . 3085 [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C. 3086 Pignataro, "The Generalized TTL Security Mechanism 3087 (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007, 3088 . 3090 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 3091 (TLS) Protocol Version 1.2", RFC 5246, 3092 DOI 10.17487/RFC5246, August 2008, 3093 . 3095 17.2. Informative References 3097 [IEEE-802.1AE] 3098 "IEEE Standards for Local and Metropolitan Area Networks: 3099 Media Access Control (MAC) Security", 3100 DOI 10.1109/IEEESTD.2006.245590, August 2006. 3102 [IEEE-802.1X] 3103 "IEEE Standards for Local and Metropolitan Area Networks: 3104 Port based Network Access Control", 3105 DOI 10.1109/IEEESTD.2010.5409813, February 2010. 3107 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3108 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 3109 DOI 10.17487/RFC5226, May 2008, 3110 . 3112 [RFC5578] Berry, B., Ed., Ratliff, S., Paradise, E., Kaiser, T., and 3113 M. Adams, "PPP over Ethernet (PPPoE) Extensions for Credit 3114 Flow and Link Metrics", RFC 5578, DOI 10.17487/RFC5578, 3115 February 2010, . 3117 [RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman, 3118 "Special-Purpose IP Address Registries", BCP 153, 3119 RFC 6890, DOI 10.17487/RFC6890, April 2013, 3120 . 3122 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 3123 "Recommendations for Secure Use of Transport Layer 3124 Security (TLS) and Datagram Transport Layer Security 3125 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 3126 2015, . 3128 Appendix A. Discovery Signal Flows 3130 Router Modem Signal Description 3131 ======================================================================== 3133 | Router initiates discovery, starts 3134 | a timer, send Peer Discovery 3135 |-------Peer Discovery---->X Signal. 3137 ~ ~ ~ ~ ~ ~ ~ Router discovery timer expires 3138 without receiving Peer Offer. 3140 | Router sends another Peer 3141 |-------Peer Discovery---------->| Discovery Signal. 3142 | 3143 | Modem receives Peer Discovery 3144 | Signal. 3145 | 3146 | Modem sends Peer Offer with 3147 |<--------Peer Offer-------------| Connection Point information. 3148 : 3149 : Router MAY cancel discovery timer 3150 : and stop sending Peer Discovery 3151 : Signals. 3153 Appendix B. Peer Level Message Flows 3155 B.1. Session Initialization 3157 Router Modem Message Description 3158 ======================================================================== 3160 | Router connects to discovered or 3161 | pre-configured Modem Connection 3162 |--TCP connection established---> Point. 3163 | 3164 | Router sends Session 3165 |----Session Initialization----->| Initialization Message. 3166 | 3167 | Modem receives Session 3168 | Initialization Message. 3169 | 3170 | Modem sends Session Initialization 3171 |<--Session Initialization Resp.-| Response, with Success Status Data 3172 | | Item. 3173 | | 3174 |<<============================>>| Session established. Heartbeats 3175 : : begin. 3177 B.2. Session Initialization - Refused 3179 Router Modem Message Description 3180 ======================================================================== 3182 | Router connects to discovered or 3183 | pre-configured Modem Connection 3184 |--TCP connection established---> Point. 3185 | 3186 | Router sends Session 3187 |-----Session Initialization---->| Initialization Message. 3188 | 3189 | Modem receives Session 3190 | Initialization Message, and will 3191 | not support the advertised 3192 | extensions. 3193 | 3194 | Modem sends Session Initialization 3195 | Response, with 'Request Denied' 3196 |<-Session Initialization Resp.--| Status Data Item. 3197 | 3198 | 3199 | Router receives negative Session 3200 | Initialization Response, closes 3201 ||---------TCP close------------|| TCP connection. 3203 B.3. Router Changes IP Addresses 3205 Router Modem Message Description 3206 ======================================================================== 3208 | Router sends Session Update 3209 |-------Session Update---------->| Message to announce change of IP 3210 | address 3211 | 3212 | Modem receives Session Update 3213 | Message and updates internal 3214 | state. 3215 | 3216 |<----Session Update Response----| Modem sends Session Update 3217 | Response. 3219 B.4. Modem Changes Session-wide Metrics 3220 Router Modem Message Description 3221 ======================================================================== 3223 | Modem sends Session Update Message 3224 | to announce change of modem-wide 3225 |<--------Session Update---------| metrics 3226 | 3227 | Router receives Session Update 3228 | Message and updates internal 3229 | state. 3230 | 3231 |----Session Update Response---->| Router sends Session Update 3232 | Response. 3234 B.5. Router Terminates Session 3236 Router Modem Message Description 3237 ======================================================================== 3239 | Router sends Session Termination 3240 |------Session Termination------>| Message with Status Data Item. 3241 | | 3242 |-------TCP shutdown (send)---> | Router stops sending Messages. 3243 | 3244 | Modem receives Session 3245 | Termination, stops counting 3246 | received heartbeats and stops 3247 | sending heartbeats. 3248 | 3249 | Modem sends Session Termination 3250 |<---Session Termination Resp.---| Response with Status 'Success'. 3251 | 3252 | Modem stops sending Messages. 3253 | 3254 ||---------TCP close------------|| Session terminated. 3256 B.6. Modem Terminates Session 3257 Router Modem Message Description 3258 ======================================================================== 3260 | Modem sends Session Termination 3261 |<----Session Termination--------| Message with Status Data Item. 3262 | 3263 | Modem stops sending Messages. 3264 | 3265 | Router receives Session 3266 | Termination, stops counting 3267 | received heartbeats and stops 3268 | sending heartbeats. 3269 | 3270 | Router sends Session Termination 3271 |---Session Termination Resp.--->| Response with Status 'Success'. 3272 | 3273 | Router stops sending Messages. 3274 | 3275 ||---------TCP close------------|| Session terminated. 3277 B.7. Session Heartbeats 3278 Router Modem Message Description 3279 ======================================================================== 3281 |----------Heartbeat------------>| Router sends heartbeat Message 3282 | 3283 | Modem resets heartbeats missed 3284 | counter. 3286 ~ ~ ~ ~ ~ ~ ~ 3288 |---------[Any Message]--------->| When the Modem receives any 3289 | Message from the Router. 3290 | 3291 | Modem resets heartbeats missed 3292 | counter. 3294 ~ ~ ~ ~ ~ ~ ~ 3296 |<---------Heartbeat-------------| Modem sends heartbeat Message 3297 | 3298 | Router resets heartbeats missed 3299 | counter. 3301 ~ ~ ~ ~ ~ ~ ~ 3303 |<--------[Any Message]----------| When the Router receives any 3304 | Message from the Modem. 3305 | 3306 | Modem resets heartbeats missed 3307 | counter. 3309 B.8. Router Detects a Heartbeat timeout 3311 Router Modem Message Description 3312 ======================================================================== 3314 X<----------------------| Router misses a heartbeat 3316 | X<----------------------| Router misses too many heartbeats 3317 | 3318 | 3319 |------Session Termination------>| Router sends Session Termination 3320 | Message with 'Timeout' Status 3321 | Data Item. 3322 : 3323 : Termination proceeds... 3325 B.9. Modem Detects a Heartbeat timeout 3327 Router Modem Message Description 3328 ======================================================================== 3330 |---------------------->X Modem misses a heartbeat 3332 |---------------------->X | Modem misses too many heartbeats 3333 | 3334 | 3335 |<-----Session Termination-------| Modem sends Session Termination 3336 | Message with 'Timeout' Status 3337 | Data Item. 3338 : 3339 : Termination proceeds... 3341 Appendix C. Destination Specific Message Flows 3343 C.1. Common Destination Notification 3344 Router Modem Message Description 3345 ======================================================================== 3347 | Modem detects a new logical 3348 | destination is reachable, and 3349 |<-------Destination Up----------| sends Destination Up Message. 3350 | 3351 |------Destination Up Resp.----->| Router sends Destination Up 3352 | Response. 3354 ~ ~ ~ ~ ~ ~ ~ 3355 | Modem detects change in logical 3356 | destination metrics, and sends 3357 |<-------Destination Update------| Destination Update Message. 3359 ~ ~ ~ ~ ~ ~ ~ 3360 | Modem detects change in logical 3361 | destination metrics, and sends 3362 |<-------Destination Update------| Destination Update Message. 3364 ~ ~ ~ ~ ~ ~ ~ 3365 | Modem detects logical destination 3366 | is no longer reachable, and sends 3367 |<-------Destination Down--------| Destination Down Message. 3368 | 3369 | Router receives Destination Down, 3370 | updates internal state, and sends 3371 |------Destination Down Resp.--->| Destination Down Response Message. 3373 C.2. Multicast Destination Notification 3374 Router Modem Message Description 3375 ======================================================================== 3377 | Router detects a new multicast 3378 | destination is in use, and sends 3379 |-----Destination Announce------>| Destination Announce Message. 3380 | 3381 | Modem updates internal state to 3382 | monitor multicast destination, and 3383 |<-----Dest. Announce Resp.------| sends Destination Announce 3384 Response. 3386 ~ ~ ~ ~ ~ ~ ~ 3387 | Modem detects change in multicast 3388 | destination metrics, and sends 3389 |<-------Destination Update------| Destination Update Message. 3391 ~ ~ ~ ~ ~ ~ ~ 3392 | Modem detects change in multicast 3393 | destination metrics, and sends 3394 |<-------Destination Update------| Destination Update Message. 3396 ~ ~ ~ ~ ~ ~ ~ 3397 | Router detects multicast 3398 | destination is no longer in use, 3399 |--------Destination Down------->| and sends Destination Down 3400 | Message. 3401 | 3402 | Modem receives Destination Down, 3403 | updates internal state, and sends 3404 |<-----Destination Down Resp.----| Destination Down Response Message. 3406 C.3. Link Characteristics Request 3407 Router Modem Message Description 3408 ======================================================================== 3410 Destination has already been 3411 ~ ~ ~ ~ ~ ~ ~ announced by either peer. 3413 | Router requires different 3414 | Characteristics for the 3415 | destination, and sends Link 3416 |--Link Characteristics Request->| Characteristics Request Message. 3417 | 3418 | Modem attempts to adjust link 3419 | properties to meet the received 3420 | request, and sends a Link 3421 | Characteristics Response 3422 |<---Link Characteristics Resp.--| Message with the new values. 3424 Authors' Addresses 3426 Stan Ratliff 3427 VT iDirect 3428 13861 Sunrise Valley Drive, Suite 300 3429 Herndon, VA 20171 3430 USA 3432 Email: sratliff@idirect.net 3434 Shawn Jury 3435 Cisco Systems 3436 170 West Tasman Drive 3437 San Jose, CA 95134 3438 USA 3440 Email: sjury@cisco.com 3442 Darryl Satterwhite 3443 Broadcom 3445 Email: dsatterw@broadcom.com 3446 Rick Taylor 3447 Airbus Defence & Space 3448 Quadrant House 3449 Celtic Springs 3450 Coedkernew 3451 Newport NP10 8FZ 3452 UK 3454 Email: rick.taylor@airbus.com 3456 Bo Berry