idnits 2.17.1 draft-ietf-manet-dlep-16.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** There are 19 instances of too long lines in the document, the longest one being 7 characters in excess of 72. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 274 has weird spacing: '... Shared o ...' == Line 275 has weird spacing: '... Medium o...' -- The document date (July 20, 2015) is 3175 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'TLS' is mentioned on line 2550, but not defined -- Obsolete informational reference (is this intentional?): RFC 5246 (Obsoleted by RFC 8446) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 2 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 B. Berry 5 Expires: January 21, 2016 6 S. Jury 7 Cisco Systems 8 D. Satterwhite 9 Broadcom 10 R. Taylor 11 Airbus Defence & Space 12 July 20, 2015 14 Dynamic Link Exchange Protocol (DLEP) 15 draft-ietf-manet-dlep-16 17 Abstract 19 When routing devices rely on modems to effect communications over 20 wireless links, they need timely and accurate knowledge of the 21 characteristics of the link (speed, state, etc.) in order to make 22 routing decisions. In mobile or other environments where these 23 characteristics change frequently, manual configurations or the 24 inference of state through routing or transport protocols does not 25 allow the router to make the best decisions. A bidirectional, event- 26 driven communication channel between the router and the modem is 27 necessary. 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 January 21, 2016. 46 Copyright Notice 48 Copyright (c) 2015 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 1.1. Protocol Overview . . . . . . . . . . . . . . . . . . . . 7 65 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 8 66 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 3. Core Features and Extensions . . . . . . . . . . . . . . . . 10 68 3.1. Experiments . . . . . . . . . . . . . . . . . . . . . . . 10 69 4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 70 4.1. Mandatory Metrics . . . . . . . . . . . . . . . . . . . . 12 71 5. DLEP Session Flow . . . . . . . . . . . . . . . . . . . . . . 12 72 5.1. Peer Discovery State . . . . . . . . . . . . . . . . . . 12 73 5.2. Session Initialization State . . . . . . . . . . . . . . 13 74 5.3. In-Session State . . . . . . . . . . . . . . . . . . . . 14 75 5.4. Session Termination State . . . . . . . . . . . . . . . . 16 76 6. DLEP Signal and Message Processing . . . . . . . . . . . . . 16 77 7. DLEP Signal and Message Structure . . . . . . . . . . . . . . 17 78 7.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 18 79 7.2. DLEP Message Header . . . . . . . . . . . . . . . . . . . 18 80 7.3. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 19 81 8. DLEP Signals and Messages . . . . . . . . . . . . . . . . . . 19 82 8.1. Peer Discovery Signal . . . . . . . . . . . . . . . . . . 20 83 8.2. Peer Offer Signal . . . . . . . . . . . . . . . . . . . . 21 84 8.3. Session Initialization Message . . . . . . . . . . . . . 21 85 8.4. Session Initialization Response Message . . . . . . . . . 22 86 8.5. Session Update Message . . . . . . . . . . . . . . . . . 24 87 8.6. Session Update Response Message . . . . . . . . . . . . . 25 88 8.7. Session Termination Message . . . . . . . . . . . . . . . 25 89 8.8. Session Termination Response Message . . . . . . . . . . 26 90 8.9. Destination Up Message . . . . . . . . . . . . . . . . . 26 91 8.10. Destination Up Response Message . . . . . . . . . . . . . 27 92 8.11. Destination Down Message . . . . . . . . . . . . . . . . 28 93 8.12. Destination Down Response Message . . . . . . . . . . . . 28 94 8.13. Destination Update Message . . . . . . . . . . . . . . . 29 95 8.14. Heartbeat Message . . . . . . . . . . . . . . . . . . . . 30 96 8.15. Link Characteristics Request Message . . . . . . . . . . 30 97 8.16. Link Characteristics Response Message . . . . . . . . . . 31 98 9. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 32 99 9.1. Status . . . . . . . . . . . . . . . . . . . . . . . . . 33 100 9.2. IPv4 Connection Point . . . . . . . . . . . . . . . . . . 35 101 9.3. IPv6 Connection Point . . . . . . . . . . . . . . . . . . 36 102 9.4. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 37 103 9.5. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 38 104 9.6. Extensions Supported . . . . . . . . . . . . . . . . . . 39 105 9.7. MAC Address . . . . . . . . . . . . . . . . . . . . . . . 39 106 9.8. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 40 107 9.9. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 41 108 9.10. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 42 109 9.11. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 42 110 9.12. Maximum Data Rate (Receive) . . . . . . . . . . . . . . . 43 111 9.13. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 44 112 9.14. Current Data Rate (Receive) . . . . . . . . . . . . . . . 44 113 9.15. Current Data Rate (Transmit) . . . . . . . . . . . . . . 45 114 9.16. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 46 115 9.17. Resources (Receive) . . . . . . . . . . . . . . . . . . . 47 116 9.18. Resources (Transmit) . . . . . . . . . . . . . . . . . . 47 117 9.19. Relative Link Quality (Receive) . . . . . . . . . . . . . 48 118 9.20. Relative Link Quality (Transmit) . . . . . . . . . . . . 49 119 9.21. Link Characteristics Response Timer . . . . . . . . . . . 49 120 10. Credit-Windowing . . . . . . . . . . . . . . . . . . . . . . 50 121 10.1. Credit-Windowing Messages . . . . . . . . . . . . . . . 51 122 10.1.1. Destination Up Message . . . . . . . . . . . . . . . 51 123 10.1.2. Destination Up Response Message . . . . . . . . . . 51 124 10.1.3. Destination Update Message . . . . . . . . . . . . . 51 125 10.2. Credit-Windowing Data Items . . . . . . . . . . . . . . 52 126 10.2.1. Credit Grant . . . . . . . . . . . . . . . . . . . . 52 127 10.2.2. Credit Window Status . . . . . . . . . . . . . . . . 53 128 10.2.3. Credit Request . . . . . . . . . . . . . . . . . . . 54 129 11. Security Considerations . . . . . . . . . . . . . . . . . . . 55 130 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 55 131 12.1. Registrations . . . . . . . . . . . . . . . . . . . . . 55 132 12.2. Expert Review: Evaluation Guidelines . . . . . . . . . . 56 133 12.3. Signal/Message Type Registration . . . . . . . . . . . . 56 134 12.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 56 135 12.5. DLEP Status Code Registrations . . . . . . . . . . . . . 56 136 12.6. DLEP Extensions Registrations . . . . . . . . . . . . . 56 137 12.7. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 57 138 12.8. DLEP Multicast Address . . . . . . . . . . . . . . . . . 57 139 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 57 140 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 57 141 14.1. Normative References . . . . . . . . . . . . . . . . . . 57 142 14.2. Informative References . . . . . . . . . . . . . . . . . 57 143 Appendix A. Discovery Signal Flows . . . . . . . . . . . . . . . 58 144 Appendix B. Peer Level Message Flows . . . . . . . . . . . . . . 58 145 B.1. Session Initialization . . . . . . . . . . . . . . . . . 58 146 B.2. Session Initialization - Refused . . . . . . . . . . . . 59 147 B.3. Router Changes IP Addresses . . . . . . . . . . . . . . . 60 148 B.4. Modem Changes Session-wide Metrics . . . . . . . . . . . 60 149 B.5. Router Terminates Session . . . . . . . . . . . . . . . . 60 150 B.6. Modem Terminates Session . . . . . . . . . . . . . . . . 61 151 B.7. Session Heartbeats . . . . . . . . . . . . . . . . . . . 61 152 B.8. Router Detects a Heartbeat timeout . . . . . . . . . . . 62 153 B.9. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 63 154 Appendix C. Destination Specific Signal Flows . . . . . . . . . 63 155 C.1. Common Destination Signaling . . . . . . . . . . . . . . 63 156 C.2. Multicast Destination Signaling . . . . . . . . . . . . . 64 157 C.3. Link Characteristics Request . . . . . . . . . . . . . . 64 158 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 65 160 1. Introduction 162 There exist today a collection of modem devices that control links of 163 variable datarate and quality. Examples of these types of links 164 include line-of-sight (LOS) terrestrial radios, satellite terminals, 165 and broadband modems. Fluctuations in speed and quality of these 166 links can occur due to configuration, or on a moment-to-moment basis, 167 due to physical phenomena like multipath interference, obstructions, 168 rain fade, etc. It is also quite possible that link quality and 169 datarate vary with respect to individual destinations on a link, and 170 with the type of traffic being sent. As an example, consider the 171 case of an 802.11 access point, serving two associated laptop 172 computers. In this environment, the answer to the question "What is 173 the datarate on the 802.11 link?" is "It depends on which associated 174 laptop we're talking about, and on what kind of traffic is being 175 sent." While the first laptop, being physically close to the access 176 point, may have a datarate of 54Mbps for unicast traffic, the other 177 laptop, being relatively far away, or obstructed by some object, can 178 simultaneously have a datarate of only 32Mbps for unicast. However, 179 for multicast traffic sent from the access point, all traffic is sent 180 at the base transmission rate (which is configurable, but depending 181 on the model of the access point, is usually 24Mbps or less). 183 In addition to utilizing variable datarate links, mobile networks are 184 challenged by the notion that link connectivity will come and go over 185 time, without an effect on a router's interface state (Up or Down). 186 Effectively utilizing a relatively short-lived connection is 187 problematic in IP routed networks, as routing protocols tend to rely 188 on interface state and independent timers at OSI Layer 3 to maintain 189 network convergence (e.g., HELLO messages and/or recognition of DEAD 190 routing adjacencies). These dynamic connections can be better 191 utilized with an event-driven paradigm, where acquisition of a new 192 neighbor (or loss of an existing one) is signaled, as opposed to a 193 paradigm driven by timers and/or interface state. 195 Another complicating factor for mobile networks are the different 196 methods of physically connecting the modem devices to the router. 197 Modems can be deployed as an interface card in a router's chassis, or 198 as a standalone device connected to the router via Ethernet or serial 199 link. In the case of Ethernet attachment, with existing protocols 200 and techniques, routing software cannot be aware of convergence 201 events occurring on the radio link (e.g., acquisition or loss of a 202 potential routing neighbor), nor can the router be aware of the 203 actual capacity of the link. This lack of awareness, along with the 204 variability in datarate, leads to a situation where finding the 205 (current) best route through the network to a given destination is 206 difficult to establish and properly maintain. This is especially 207 true of demand-based access schemes such as Demand Assigned Multiple 208 Access (DAMA) implementations used on some satellite systems. With a 209 DAMA-based system, additional datarate may be available, but will not 210 be used unless the network devices emit traffic at a rate higher than 211 the currently established rate. Increasing the traffic rate does not 212 guarantee additional datarate will be allocated; rather, it may 213 result in data loss and additional retransmissions on the link. 215 Addressing the challenges listed above, the co-authors have developed 216 the Dynamic Link Exchange Protocol, or DLEP. The DLEP protocol runs 217 between a router and its attached modem devices, allowing the modem 218 to communicate link characteristics as they change, and convergence 219 events (acquisition and loss of potential routing destinations). The 220 following diagrams are used to illustrate the scope of DLEP packets. 222 |-------Local Node-------| |-------Remote Node------| 223 | | | | 224 +--------+ +-------+ +-------+ +--------+ 225 | Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router | 226 | | | Device| | Device| | | 227 +--------+ +-------+ +-------+ +--------+ 228 | | | Link | | | 229 |-DLEP--| | Protocol | |-DLEP--| 230 | | | (e.g. | | | 231 | | | 802.11) | | | 233 Figure 1: DLEP Network 235 In Figure 1, when the local modem detects the presence of a remote 236 node, it (the local modem) sends a message to its router via the DLEP 237 protocol. The message consists of an indication of what change has 238 occurred on the link (e.g., presence of a remote node detected), 239 along with a collection of DLEP-defined Data Items that further 240 describe the change. Upon receipt of the message, the local router 241 may take whatever action it deems appropriate, such as initiating 242 discovery protocols, and/or issuing HELLO messages to converge the 243 network. On a continuing, as-needed basis, the modem devices use 244 DLEP to report any characteristics of the link (datarate, latency, 245 etc.) that have changed. DLEP is independent of the link type and 246 topology supported by the modem. Note that the DLEP protocol is 247 specified to run only on the local link between router and modem. 248 Some over the air signaling may be necessary between the local and 249 remote modem in order to provide some parameters in DLEP messages 250 between the local modem and local router, but DLEP does not specify 251 how such over the air signaling is carried out. Over the air 252 signaling is purely a matter for the modem implementer. 254 Figure 2 shows how DLEP can support a configuration where routers are 255 connected with different link types. In this example, Modem A 256 implements a point-to-point link, and Modem B is connected via a 257 shared medium. In both cases, the DLEP protocol is used to report 258 the characteristics of the link (datarate, latency, etc.) to routers. 259 The modem is also able to use the DLEP session to notify the router 260 when the remote node is lost, shortening the time required to re- 261 converge the network. 263 +--------+ +--------+ 264 +----+ Modem A| | Modem A+---+ 265 | | Device | <===== // ======> | Device | | 266 | +--------+ P-2-P Link +--------+ | 267 +---+----+ +---+----+ 268 | Router | | Router | 269 | | | | 270 +---+----+ +---+----+ 271 | +--------+ +--------+ | 272 +-----+ Modem B| | Modem B| | 273 | Device | o o o o o o o o | Device +--+ 274 +--------+ o Shared o +--------+ 275 o Medium o 276 o o 277 o o 278 o o 279 o 280 +--------+ 281 | Modem B| 282 | Device | 283 +---+----+ 284 | 285 | 286 +---+----+ 287 | Router | 288 | | 289 +--------+ 291 Figure 2: DLEP Network with Multiple Modem Devices 293 1.1. Protocol Overview 295 As mentioned earlier, DLEP defines a set of messages used by modems 296 and their attached routers. The messages are used to communicate 297 events that occur on the physical link(s) managed by the modem: for 298 example, a remote node entering or leaving the network, or that the 299 link has changed. Associated with these messages are a set of data 300 items - information that describes the remote node (e.g., address 301 information), and/or the characteristics of the link to the remote 302 node. 304 The protocol is defined as a collection of type-length-value (TLV) 305 based formats, specifying the messages that are exchanged between a 306 router and a modem, and the data items associated with the message. 307 This document specifies transport of DLEP messages and data items via 308 the TCP transport, with a UDP-based discovery mechanism. Other 309 transports for the protocol are possible, but are outside the scope 310 of this document. 312 DLEP uses a session-oriented paradigm between the modem device and 313 its associated router. If multiple modem devices are attached to a 314 router (as in Figure 2), or the modem supports multiple connections 315 (via multiple logical or physical interfaces), then separate DLEP 316 sessions exist for each modem or connection. This router/modem 317 session provides a carrier for information exchange concerning 318 'destinations' that are available via the modem device. A 319 'destination' can be either physical (as in the case of a specific 320 far-end router), or a logical destination (as in a Multicast group). 321 As such, all of the destination-level exchanges in DLEP can be 322 envisioned as building an information base concerning the remote 323 nodes, and the link characteristics to those nodes. 325 Multicast traffic destined for the variable-quality network (the 326 network accessed via the DLEP modem) is handled in IP networks by 327 deriving a Layer 2 MAC address based on the Layer 3 address. 328 Leveraging on this scheme, multicast traffic is supported in DLEP 329 simply by treating the derived MAC address as any other 'destination' 330 (albeit a logical one) in the network. To support these logical 331 destinations, one of the DLEP participants (typically, the router) 332 informs the other as to the existence of the logical destination. 333 The modem, once it is aware of the existence of this logical 334 destination, reports link characteristics just as it would for any 335 other destination in the network. The specific algorithms a modem 336 would use to derive metrics on multicast (or logical) destinations 337 are outside the scope of this specification, and is left to specific 338 implementations to decide. 340 1.2. Requirements 342 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 343 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 344 "OPTIONAL" in this document are to be interpreted as described in BCP 345 14, RFC 2119 [RFC2119]. 347 2. Assumptions 349 Routers and modems that exist as part of the same node (e.g., that 350 are locally connected) can use a discovery technique to locate each 351 other, thus avoiding a priori configuration. The router is 352 responsible for initializing the discovery process, using the Peer 353 Discovery signal (Section 8.1). 355 DLEP uses a session-oriented paradigm. A router and modem form a 356 session by completing the discovery and initialization process. This 357 router-modem session persists unless or until it either (1) times 358 out, based on the timeout values supplied, or (2) is explicitly torn 359 down by one of the participants. Note that while use of timers in 360 DLEP is optional, it is strongly RECOMMENDED that implementations 361 choose to run with timers enabled. 363 DLEP assumes that the MAC address for delivering data traffic is the 364 MAC specified in the Destination Up message (Section 8.9). No 365 manipulation or substitution is performed; the MAC address supplied 366 in Destination Up is used as the OSI Layer 2 Destination MAC address. 367 DLEP also assumes that MAC addresses MUST be unique within the 368 context of a router-modem session. Additionally, DLEP can support 369 MAC addresses in either EUI-48 or EUI-64 format, with the restriction 370 that ALL MAC addresses for a given DLEP session MUST be in the same 371 format, and MUST be consistent with the MAC address format of the 372 connected modem (e.g., if the modem is connected to the router with 373 an EUI-48 MAC, all destination addresses via that modem MUST be 374 expressed in EUI-48 format). 376 DLEP uses UDP multicast for single-hop discovery signalling, and TCP 377 for transport of the control messages. Therefore, DLEP assumes that 378 the modem and router have topologically consistent IP addresses 379 assigned. It is RECOMMENDED that DLEP implementations utilize IPv6 380 link-local addresses to reduce the administrative burden of address 381 assignment. 383 Destinations can be identified by either the router or the modem, and 384 represent a specific destination (e.g., an address) that exists on 385 the link(s) managed by the modem. A destination MUST contain a MAC 386 address, it MAY optionally include a Layer 3 address (or addresses). 387 Note that since a destination is a MAC address, the MAC could 388 reference a logical destination, as in a derived multicast MAC 389 address, as well as a physical device. As destinations are 390 discovered, DLEP routers and modems build an information base on 391 destinations accessible via the modem. 393 The DLEP messages concerning destinations thus become the way for 394 routers and modems to maintain, and notify each other about, an 395 information base representing the physical and logical (e.g., 396 multicast) destinations accessible via the modem device. The 397 information base would contain addressing information (i.e. MAC 398 address, and OPTIONALLY, Layer 3 addresses), link characteristics 399 (metrics), and OPTIONALLY, flow control information (credits). 401 DLEP assumes that any message not understood by a receiver MUST 402 result in an error indication being sent to the originator, and also 403 MUST result in termination of the session between the DLEP peers. 404 Any DLEP data item not understood by a receiver MUST also result in 405 termination of the session. 407 DLEP assumes that security on the session (e.g., authentication of 408 session partners, encryption of traffic, or both) is dealt with by 409 the underlying transport mechanism (e.g., by using a transport such 410 as TLS [RFC5246]). 412 This document specifies an implementation of the DLEP messages 413 running over the TCP transport. It is assumed that DLEP running over 414 other transport mechanisms would be documented separately. 416 3. Core Features and Extensions 418 DLEP has a core set of signals, messages and data items that MUST be 419 parsed without error by an implementation in order to guarantee 420 interoperability and therefore make the implementation DLEP 421 compliant. This document defines this set of signals, messages and 422 data items, listing them as 'core'. It should be noted that some 423 core signals, messages and data items might not be used during the 424 lifetime of a single DLEP session, but a compliant implementation 425 MUST support them. 427 While this document represents the best efforts of the working group 428 to be functionally complete, it is recognized that extensions to DLEP 429 will in all likelihood be necessary as more link types are used. 431 If interoperable protocol extensions are required, they MUST be 432 standardized either as an update to this document, or as an 433 additional stand-alone specification. The requests for IANA- 434 controlled registries in this document contain sufficient Reserved 435 space, in terms of DLEP signals, messages, data items and status 436 codes, to accommodate future extensions to the protocol and the data 437 transferred. 439 All extensions are considered OPTIONAL. Extensions may be negotiated 440 on a per-session basis during session initialization via the 441 Extensions Supported mechanism. Only the DLEP functionality listed 442 as 'core' is required by an implementation in order to be DLEP 443 compliant. 445 This specification defines one extension, Credit Windowing, that 446 devices MAY choose to implement. 448 3.1. Experiments 450 This document requests Private Use numbering space in the DLEP 451 signal/message, data item and status code registries for experimental 452 items. The intent is to allow for experimentation with new signals, 453 messages, data items, and/or status codes, while still retaining the 454 documented DLEP behavior. 456 Use of the experimental signals, messages, data items, status codes, 457 or behaviors MUST be announced as Extensions, using extension 458 identifiers from the Private Use space in the Extensions Supported 459 registry (Table 4), during session initialization with a value agreed 460 upon (a priori) between the participating peers. 462 Multiple experiments MAY be announced in the Session Initialization 463 messages. However, use of multiple experiments in a single session 464 could lead to interoperability issues or unexpected results (e.g., 465 clashes of experimental signals, messages, data items and/or status 466 code types), and is therefore discouraged. It is left to 467 implementations to determine the correct processing path (e.g., a 468 decision on whether to terminate the session, or to establish a 469 precedence of the conflicting definitions) if such conflicts arise. 471 4. Metrics 473 DLEP includes the ability for the router and modem to communicate 474 metrics that reflect the characteristics (e.g., datarate, latency) of 475 the variable-quality link in use. DLEP does not specify how a given 476 metric value is to be calculated, rather, the protocol assumes that 477 metrics have been calculated with a 'best effort', incorporating all 478 pertinent data that is available to the modem device. 480 DLEP allows for metrics to be sent within two contexts - metrics for 481 a specific destination within the network (e.g., a specific router), 482 and per-session (those that apply to all destinations accessed via 483 the modem). Most metrics can be further subdivided into transmit and 484 receive metrics. In cases where metrics are provided at session 485 level, the receiver MUST propagate the metrics to all entries in its 486 information base for destinations that are accessed via the 487 originator. 489 DLEP modem implementations MUST announce all metric items that will 490 be reported during the session, and provide default values for those 491 metrics, in the Session Initialization Response message 492 (Section 8.4). In order to use a metric type that was not included 493 in the Session Initialization Response message, modem implementations 494 MUST terminate the session with the router (via the Session Terminate 495 message (Section 8.7)), and establish a new session. 497 It is left to implementations to choose sensible default values based 498 on their specific characteristics. Modems having static (non- 499 changing) link metric characteristics MAY report metrics only once 500 for a given destination (or once on a modem-wide basis, if all 501 connections via the modem are of this static nature). 503 A DLEP participant MAY send metrics both in a session context (via 504 the Session Update message) and a specific destination context (via 505 Destination Update) at any time. The heuristics for applying 506 received metrics is left to implementations. 508 4.1. Mandatory Metrics 510 As mentioned above, DLEP modem implementations MUST announce all 511 supported metric items during the Session Initialization state. 512 However, a modem MUST include the following list of metrics in the 513 Session Initialization Response message (Section 8.4): 515 o Maximum Data Rate (Receive) (Section 9.12) 517 o Maximum Data Rate (Transmit) (Section 9.13) 519 o Current Data Rate (Receive) (Section 9.14) 521 o Current Data Rate (Transmit) (Section 9.15) 523 o Latency (Section 9.16) 525 5. DLEP Session Flow 527 All DLEP peers transition through four (4) distinct states during the 528 lifetime of a DLEP session: 530 o Peer Discovery 532 o Session Initialization 534 o In-Session 536 o Session Termination 538 The Peer Discovery state is OPTIONAL to implement for routers. If it 539 is used, this state is the initial state. If it is not used, then 540 one or more preconfigured address/port combinations SHOULD be 541 provided to the router, and the device starts in the Session 542 Initialization state. 544 Modems MUST support the Peer Discovery state. 546 5.1. Peer Discovery State 548 In the Peer Discovery state, routers send UDP packets containing a 549 Peer Discovery signal (Section 8.1) to the DLEP well-known multicast 550 address (Section 12.8) and port number (Section 12.7) then await a 551 unicast UDP packet containing a Peer Offer signal (Section 8.2) from 552 a modem. While in the Peer Discovery state, Peer Discovery signals 553 MUST be sent repeatedly by a router, at regular intervals; every 554 three (3) seconds is RECOMMENDED. 556 In the Peer Discovery state, the modem waits for incoming Peer 557 Discovery signals on the DLEP well-known multicast address and port. 558 On receipt of a valid signal, it MUST unicast a Peer Offer signal to 559 the source address of the received UDP packet. Peer Offer signals 560 MAY contain the unicast address and port for TCP-based communication 561 with a modem, via the IPv4 Connection Point data item (Section 9.2) 562 or the IPv6 Connection Point data item (Section 9.3), on which it is 563 prepared to accept an incoming TCP connection. The modem then begins 564 listening for incoming TCP connections, and, having accepted one, 565 enters the Session Initialization state. Anything other than Peer 566 Discovery signals received on the UDP socket MUST be silently 567 dropped. 569 Modems SHOULD be prepared to accept a TCP connection from a router 570 that is not using the Discovery mechanism, i.e. a connection attempt 571 that occurs without a preceeding Peer Discovery signal. The modem 572 MUST accept a TCP connection on only one (1) address/port combination 573 per session. 575 Routers MUST use one or more of the modem address/port combinations 576 from the Peer Offer signal or from a priori configuration to 577 establish a new TCP connection to the modem. If more than one modem 578 address/port combinations is available, router implementations MAY 579 use their own heuristics to determine the order in which they are 580 tried. If a TCP connection cannot be achieved using any of the 581 address/port combinations and the Discovery mechanism is in use, then 582 the router SHOULD resume issuing Peer Discovery signals. If no IP 583 Connection Point data items are included in the Peer Offer signal, 584 the router MUST use the origin address of the signal as the IP 585 address, and the DLEP well-known port number. 587 Once a TCP connection has been established with the modem, the router 588 begins a new session and enters the Session Initialization state. It 589 is up to the router implementation if Peer Discovery signals continue 590 to be sent after the device has transitioned to the Session 591 Initialization state. 593 5.2. Session Initialization State 595 On entering the Session Initialization state, the router MUST send a 596 Session Initialization message (Section 8.3) to the modem. The 597 router MUST then wait for receipt of a Session Initialization 598 Response message (Section 8.4) from the modem. Receipt of the 599 Session Initialization Response message containing a Status data item 600 (Section 9.1) with value 'Success', see Table 3, indicates that the 601 modem has received and processed the Session Initialization message, 602 and the router MUST transition to the In-Session state. 604 On entering the Session Initialization state, the modem MUST wait for 605 receipt of a Session Initialization message from the router. Upon 606 receipt and successful parsing of a Session Initialization message, 607 the modem MUST send a Session Initialization Response message, and 608 the session MUST transition to the In-Session state. 610 As mentioned before, DLEP provides an extension negotiation 611 capability to be used in the Session Initialization state. 612 Extensions supported by an implementation MUST be declared to 613 potential DLEP peers using the Extensions Supported data item 614 (Section 9.6). 616 Once both peers have exchanged initialization messages, an 617 implementation MUST NOT emit any message, signal, data item or status 618 code associated with an extension that was not specified in the 619 received initialization message from its peer. 621 If the router receives any message other than a valid Session 622 Initialization Response, it MUST send a Session Termination message 623 (Section 8.7) with a relevant status code, e.g. 'Unexpected 624 Message', see Table 3, and transition to the Session Termination 625 state. 627 If the modem receives any message other than Session Initialization, 628 or it fails to parse the received message, it MUST NOT send any 629 message, and MUST terminate the TCP connection, then restart at the 630 Peer Discovery state. 632 As mentioned before, the Session Initialization Response message MUST 633 contain metric data items for ALL metrics that will be used during 634 the session. If an additional metric is to be introduced after the 635 session has started, the session between router and modem MUST be 636 terminated and restarted, and the new metric described in the next 637 Session Initialization Response message. 639 5.3. In-Session State 641 In the In-Session state, messages can flow in both directions between 642 peers, indicating changes to the session state, the arrival or 643 departure of reachable destinations, or changes of the state of the 644 links to the destinations. 646 In order to maintain the In-Session state, periodic Heartbeat 647 messages (Section 8.14) MAY 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 participants. Each DLEP 650 peer is responsible for the creation of heartbeat messages. Receipt 651 of any valid DLEP message MUST reset the heartbeat interval timer 652 (i.e., valid DLEP messages take the place of, and obviate the need 653 for, Heartbeat messages). 655 DLEP provides a Session Update message (Section 8.5), intended to 656 communicate some change in status (e.g., a change of layer 3 address 657 parameters, or a modem-wide link change). 659 In addition to the session messages, the participants will transmit 660 messages concerning destinations in the network. These messages 661 trigger creation/maintenance/deletion of destinations in the 662 information base of the recipient. For example, a modem will inform 663 its attached router of the presence of a new destination via the 664 Destination Up message (Section 8.9). Receipt of a Destination Up 665 causes the router to allocate the necessary resources, creating an 666 entry in the information base with the specifics (i.e. MAC Address, 667 Latency, Data Rate, etc.) of the destination. The loss of a 668 destination is communicated via the Destination Down message 669 (Section 8.11), and changes in status to the destination (e.g., 670 varying link quality, or addressing changes) are communicated via the 671 Destination Update message (Section 8.13). The information on a 672 given destination will persist in the router's information base until 673 (1) a Destination Down message is received, indicating that the modem 674 has lost contact with the remote node, or (2) the router/modem 675 transitions to the Session Termination state. 677 In addition to receiving metrics about the link, DLEP provides a 678 message allowing a router to request a different datarate, or 679 latency, from the modem. This message is referred to as the Link 680 Characteristics Request message (Section 8.15), and gives the router 681 the ability to deal with requisite increases (or decreases) of 682 allocated datarate/latency in demand-based schemes in a more 683 deterministic manner. 685 The In-Session state is maintained until one of the following 686 conditions occur: 688 o The implementation terminates the session by sending a Session 689 Termination message (Section 8.7)), or 691 o The DLEP peer terminates the session, indicated by receiving a 692 Session termination message. 694 The implementation MUST then transition to the Session Termination 695 state. 697 5.4. Session Termination State 699 When a DLEP implementation enters the Session Termination state after 700 sending a Session Termination message (Section 8.7) as the result of 701 an invalid message or error, it MUST wait for a Session Termination 702 Response message (Section 8.8) from its peer. If Heartbeat messages 703 (Section 8.14) are in use, senders SHOULD allow four (4) heartbeat 704 intervals to expire before assuming that the peer is unresponsive, 705 and continuing with session termination. If Heartbeat messages are 706 not in use, then if is RECOMMENDED that an interval of eight (8) 707 seconds be used. 709 When a DLEP implementation enters the Session Termination state 710 having received a Session Termination message from its peer, it MUST 711 immediately send a Session Termination Response. 713 The sender and receiver of a Session Termination message MUST release 714 all resources allocated for the session, and MUST eliminate all 715 destinations in the information base accessible via the peer 716 represented by the session. No Destination Down messages 717 (Section 8.11) are sent. 719 Any messages received after either sending or receiving a Session 720 Termination message MUST be silently ignored. 722 Once Session Termination messages have been exchanged, or timed out, 723 the device MUST terminate the TCP connection to the peer, and return 724 to the relevant initial state. 726 6. DLEP Signal and Message Processing 728 Most messages in DLEP are members of a request/response pair, e.g. 729 Destination Up message (Section 8.9), and Destination Up Response 730 message (Section 8.10). These pairs of messages define an implicit 731 transaction model for both session messages and destination messages. 733 As mentioned before, session message pairs control the flow of the 734 session through the various states, e.g. an implementation MUST NOT 735 leave the Session Initialization state until a Session Initialization 736 message (Section 8.3) and Session Initialization Response message 737 (Section 8.4) have been exchanged. 739 Destination message pairs describe the arrival and departure of 740 logical destinations, and control the flow of information about the 741 destinations in the several ways. 743 Prior to the exchange of a pair of Destination Up and Destination Up 744 Response messages, no messages concerning the logical destination 745 identified by the MAC Address data item (Section 9.7) may be sent. 746 An implementation receiving a message with such an unannounced 747 destination MUST terminate the session by issuing a Session 748 Termination message (Section 8.7) with a status code of 'Invalid 749 Destination', see Table 3, and transition to the Session Termination 750 state. 752 The receiver of a Destination Up message MAY decline further messages 753 concerning a given destination by sending a Destination Up Response 754 with a status code of 'Not Interested', see Table 3. Receivers of 755 such responses MUST NOT send further messages concerning that 756 destination to the peer. 758 After exchanging a pair of Destination Down (Section 8.11) and 759 Destination Down Response (Section 8.12) messages, no messages 760 concerning the logical destination identified by the MAC Address data 761 item may be a sent without a previously sending a new Destination Up 762 message. An implementation receiving a message about a down 763 destination MUST terminate the session by issuing a Session 764 Termination message with a status code of 'Invalid Destination' and 765 transition to the Session Termination state. 767 7. DLEP Signal and Message Structure 769 DLEP defines two protocol units used in two different ways: Signals 770 and Messages. Signals are only used in the Discovery mechanism and 771 are carried in UDP datagrams. Messages are used bi-directionally 772 over a TCP connection between two peers, in the Session 773 Initialization, In-Session and Session Termination states. 775 Both signals and messages consist of a header followed by an 776 unordered list of data items. Headers consist of Type and Length 777 information, while data items are encoded as TLV (Type-Length-Value) 778 structures. In this document, the data items following a signal or 779 message header are described as being 'contained in' the signal or 780 message. 782 There is no restriction on the order of data items following a 783 header, and the multiplicity of duplicate data items is defined by 784 the definition of the signal or message declared by the type in the 785 header. 787 All integers in header fields and values MUST be in network byte- 788 order. 790 7.1. DLEP Signal Header 792 The DLEP signal header contains the following fields: 794 0 1 2 3 795 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 1 796 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 797 | 'D' | 'L' | 'E' | 'P' | 798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 799 | Signal Type | Length | 800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 802 Figure 3: DLEP Signal Header 804 "DLEP": Every signal MUST start with the characters: U+44, U+4C, 805 U+45, U+50. 807 Signal Type: An 16-bit unsigned integer containing one of the DLEP 808 Signal/Message Type values defined in this document. 810 Length: The length in octets, expressed as a 16-bit unsigned 811 integer, of all of the DLEP data items associated with this 812 signal. This length SHALL NOT include the length of the header 813 itself. 815 The DLEP signal header is immediately followed by one or more DLEP 816 data items, encoded in TLVs, as defined in this document. 818 If an unrecognized, or unexpected signal is received, or a received 819 signal contains unrecognized, invalid, or disallowed duplicate data 820 items, the receiving peer MUST ignore the signal. 822 7.2. DLEP Message Header 824 The DLEP message header contains the following fields: 826 0 1 2 3 827 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 1 828 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 829 | Message Type | Length | 830 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 832 Figure 4: DLEP Message Header 834 Message Type: An 16-bit unsigned integer containing one of the DLEP 835 Signal/Message Type values defined in this document. 837 Length: The length in octets, expressed as a 16-bit unsigned 838 integer, of all of the DLEP data items associated with this 839 message. This length SHALL NOT include the length of the header 840 itself. 842 The DLEP message header is immediately followed by one or more DLEP 843 data items, encoded in TLVs, as defined in this document. 845 If an unrecognized, or unexpected message is received, or a received 846 message contains unrecognized, invalid, or disallowed duplicate data 847 items, the receiving peer MUST issue a Session Termination message 848 (Section 8.7) with a Status data item (Section 9.1) containing the 849 most relevant status code, and transition to the Session Termination 850 state. 852 7.3. DLEP Generic Data Item 854 All DLEP data items contain the following fields: 856 0 1 2 3 857 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 1 858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 859 | Data Item Type | Length | 860 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 861 | Value... : 862 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 864 Figure 5: DLEP Generic Data Item 866 Data Item Type: An 16-bit unsigned integer field specifying the type 867 of data item being sent. 869 Length: The length in octets, expressed as an 16-bit unsigned 870 integer, of the value field of the data item. This length SHALL 871 NOT include the length of the header itself. 873 Value: A field of octets, which contains data specific to a 874 particular data item. 876 8. DLEP Signals and Messages 878 As mentioned above, all DLEP signals begin with the DLEP signal 879 header, and all DLEP messages begin with the DLEP message header. 880 Therefore, in the following descriptions of specific signals and 881 messages, this header is assumed, and will not be replicated. 883 Following is the set of core signals and messages that MUST be 884 recognized by a DLEP compliant implementation. As mentioned before, 885 not all messages may be used during a session, but an implementation 886 MUST correctly process these messages when received. 888 The core DLEP signals and messages are: 890 +-------------+-----------------------------------------------------+ 891 | Type Code | Description | 892 +-------------+-----------------------------------------------------+ 893 | 0 | Reserved | 894 | 1 | Peer Discovery signal (Section 8.1) | 895 | 2 | Peer Offer signal (Section 8.2) | 896 | 3 | Session Initialization message (Section 8.3) | 897 | 4 | Session Initialization Response message (Section | 898 | | 8.4) | 899 | 5 | Session Update message (Section 8.5) | 900 | 6 | Session Update Response message (Section 8.6) | 901 | 7 | Session Termination message (Section 8.7) | 902 | 8 | Session Termination Response message (Section 8.8) | 903 | 9 | Destination Up message (Section 8.9) | 904 | 10 | Destination Up Response message (Section 8.10) | 905 | 11 | Destination Down message (Section 8.11) | 906 | 12 | Destination Down Response message (Section 8.12) | 907 | 13 | Destination Update message (Section 8.13) | 908 | 14 | Heartbeat message (Section 8.14) | 909 | 15 | Link Characteristics Request message (Section 8.15) | 910 | 16 | Link Characteristics Response message (Section | 911 | | 8.16) | 912 | 17-65519 | Reserved for future extensions | 913 | 65520-65534 | Private Use. Available for experiments | 914 | 65535 | Reserved | 915 +-------------+-----------------------------------------------------+ 917 Table 1: DLEP Signal/Message types 919 8.1. Peer Discovery Signal 921 A Peer Discovery signal SHOULD be sent by a router to discover DLEP 922 modems in the network. The Peer Offer signal (Section 8.2) is 923 required to complete the discovery process. Implementations MAY 924 implement their own retry heuristics in cases where it is determined 925 the Peer Discovery signal has timed out. 927 To construct a Peer Discovery signal, the Signal Type value in the 928 signal header is set to 1, from Table 1. 930 The Peer Discovery signal MAY contain the following data item: 932 o Peer Type (Section 9.4) 934 8.2. Peer Offer Signal 936 A Peer Offer signal MUST be sent by a DLEP modem in response to a 937 valid Peer Discovery signal (Section 8.1). 939 The Peer Offer signal MUST be sent to the unicast address of the 940 originator of the Peer Discovery signal. 942 To construct a Peer Offer signal, the Signal Type value in the signal 943 header is set to 2, from Table 1. 945 The Peer Offer signal MAY contain the following data item: 947 o Peer Type (Section 9.4) 949 The Peer Offer signal MAY contain one or more of any of the following 950 data items, with different values: 952 o IPv4 Connection Point (Section 9.2) 954 o IPv6 Connection Point (Section 9.3) 956 The IP Connection Point data items indicate the unicast address the 957 receiver of Peer Offer MUST use when connecting the DLEP TCP session. 958 If multiple IP Connection Point data items are present in the Peer 959 Offer signal, implementations MAY use their own heuristics to select 960 the address to connect to. If no IP Connection Point data items are 961 included in the Peer Offer signal, the receiver MUST use the origin 962 address of the signal as the IP address, and the DLEP well-known port 963 number (Section 12.7) to establish the TCP connection. 965 8.3. Session Initialization Message 967 A Session Initialization message MUST be sent by a router as the 968 first message of the DLEP TCP session. It is sent by the router 969 after a TCP connect to an address/port combination that was obtained 970 either via receipt of a Peer Offer, or from a priori configuration. 972 If any optional extensions are supported by the implementation, they 973 MUST be enumerated in the Extensions Supported data item. If an 974 Extensions Supported data item does not exist in a Session 975 Initialization message, the receiver of the message MUST conclude 976 that there is no support for extensions in the sender. 978 Implementations supporting the Heartbeat Interval (Section 9.5) 979 should understand that heartbeats are not fully established until 980 receipt of Session Initialization Response message (Section 8.4), and 981 should therefore implement their own timeout and retry heuristics for 982 this message. 984 To construct a Session Initialization message, the Message Type value 985 in the message header is set to 3, from Table 1. 987 The Session Initialization message MUST contain one of each of the 988 following data items: 990 o Heartbeat Interval (Section 9.5) 992 The Session Initialization message MAY contain one of each of the 993 following data items: 995 o Peer Type (Section 9.4) 997 o Extensions Supported (Section 9.6) 999 A Session Initialization message MUST be acknowledged by the receiver 1000 issuing a Session Initialization Response message (Section 8.4). 1002 8.4. Session Initialization Response Message 1004 A Session Initialization Response message MUST be sent in response to 1005 a received Session Initialization message (Section 8.3). The Session 1006 Initialization Response message completes the DLEP session 1007 establishment; the sender of the message should transition to the In- 1008 Session state when the message is sent, and the receiver should 1009 transition to the In-Session state upon receipt (and successful 1010 parsing) of an acceptable Session Initialization Response message. 1012 All supported metric data items MUST be included in the Session 1013 Initialization Response message, with default values to be used on a 1014 'modem-wide' basis. This can be viewed as the modem 'declaring' all 1015 supported metrics at DLEP session initialization. Receipt of any 1016 DLEP message containing a metric data item not included in the 1017 Session Initialization Response message MUST be treated as an error, 1018 resulting in the termination of the DLEP session between router and 1019 modem. 1021 If any optional extensions are supported by the modem, they MUST be 1022 enumerated in the Extensions Supported data item. If an Extensions 1023 Supported data item does not exist in a Session Initialization 1024 Response message, the receiver of the message MUST conclude that 1025 there is no support for extensions in the sender. 1027 After the Session Initialization/Session Initialization Response 1028 messages have been successfully exchanged, implementations MUST only 1029 use extensions that are supported by BOTH peers. 1031 To construct a Session Initialization Response message, the Message 1032 Type value in the message header is set to 4, from Table 1. 1034 The Session Initialization Response message MUST contain one of each 1035 of the following data items: 1037 o Heartbeat Interval (Section 9.5) 1039 o Maximum Data Rate (Receive) (Section 9.12) 1041 o Maximum Data Rate (Transmit) (Section 9.13) 1043 o Current Data Rate (Receive) (Section 9.14) 1045 o Current Data Rate (Transmit) (Section 9.15) 1047 o Latency (Section 9.16) 1049 The Session Initialization Response message MUST contain one of each 1050 of the following data items, if the data item will be used during the 1051 lifetime of the session: 1053 o Resources (Receive) (Section 9.17) 1055 o Resources (Transmit) (Section 9.18) 1057 o Relative Link Quality (Receive) (Section 9.19) 1059 o Relative Link Quality (Transmit) (Section 9.20) 1061 The Session Initialization Response message MAY contain one of each 1062 of the following data items: 1064 o Status (Section 9.1) 1066 o Peer Type (Section 9.4) 1068 o Extensions Supported (Section 9.6) 1070 A receiver of a Session Initialization Response message without a 1071 Status data item MUST behave as if a Status data item with code 1072 'Success' had been received. 1074 8.5. Session Update Message 1076 A Session Update message MAY be sent by a DLEP peer to indicate local 1077 Layer 3 address changes, or metric changes on a modem-wide basis. 1078 For example, addition of an IPv4 address to the router MAY prompt a 1079 Session Update message to its attached DLEP modems. Also, for 1080 example, a modem that changes its Maximum Data Rate (Receive) for all 1081 destinations MAY reflect that change via a Session Update message to 1082 its attached router(s). 1084 Concerning Layer 3 addresses, if the modem is capable of 1085 understanding and forwarding this information (via proprietary 1086 mechanisms), the address update would prompt any remote DLEP modems 1087 (DLEP-enabled modems in a remote node) to issue a Destination Update 1088 message (Section 8.13) to their local routers with the new (or 1089 deleted) addresses. Modems that do not track Layer 3 addresses 1090 SHOULD silently parse and ignore Layer 3 data items. The Session 1091 Update message MUST be acknowledged with a Session Update Response 1092 message (Section 8.6). 1094 If metrics are supplied with the Session Update message (e.g., 1095 Maximum Data Rate), these metrics are considered to be modem-wide, 1096 and therefore MUST be applied to all destinations in the information 1097 base associated with the router/modem session. 1099 Supporting implementations are free to employ heuristics to 1100 retransmit Session Update messages. The sending of Session Update 1101 messages for Layer 3 address changes SHOULD cease when either 1102 participant (router or modem) determines that the other 1103 implementation does not support Layer 3 address tracking. 1105 To construct a Session Update message, the Message Type value in the 1106 message header is set to 5, from Table 1. 1108 The Session Update message MAY contain one of each of the following 1109 data items: 1111 o Maximum Data Rate (Receive) (Section 9.12) 1113 o Maximum Data Rate (Transmit) (Section 9.13) 1115 o Current Data Rate (Receive) (Section 9.14) 1117 o Current Data Rate (Transmit) (Section 9.15) 1119 o Latency (Section 9.16) 1121 o Resources (Receive) (Section 9.17) 1122 o Resources (Transmit) (Section 9.18) 1124 o Relative Link Quality (Receive) (Section 9.19) 1126 o Relative Link Quality (Transmit) (Section 9.20) 1128 The Session Update message MAY contain one or more of the following 1129 data items, with different values: 1131 o IPv4 Address (Section 9.8) 1133 o IPv6 Address (Section 9.9) 1135 A Session Update message MUST be acknowledged by the receiver issuing 1136 a Session Update Response message (Section 8.6). 1138 8.6. Session Update Response Message 1140 A Session Update Response message MUST be sent by implementations to 1141 indicate whether a Session Update message (Section 8.5) was 1142 successfully received. 1144 To construct a Session Update Response message, the Message Type 1145 value in the message header is set to 6, from Table 1. 1147 The Session Update Response message MAY contain one of each of the 1148 following data items: 1150 o Status (Section 9.1) 1152 A receiver of a Session Update Response message without a Status data 1153 item MUST behave as if a Status data item with code 'Success' had 1154 been received. 1156 8.7. Session Termination Message 1158 A Session Termination message MUST be sent by a DLEP participant when 1159 the router/modem session needs to be terminated. 1161 To construct a Session Termination message, the Message Type value in 1162 the message header is set to 7, from Table 1. 1164 The Session Termination message MAY contain one of each of the 1165 following data items: 1167 o Status (Section 9.1) 1168 A receiver of a Session Termination message without a Status data 1169 item MUST behave as if a Status of 'Unknown reason for Session 1170 Termination' has been received. 1172 A Session Termination message MUST be acknowledged by the receiver 1173 issuing a Session Termination Response message (Section 8.8). 1175 8.8. Session Termination Response Message 1177 A Session Termination Response message MUST be sent by a DLEP peer in 1178 response to a received Session Termination message (Section 8.7). 1180 Receipt of a Session Termination Response message completes the 1181 teardown of the router/modem session. 1183 To construct a Session Termination Response message, the Message Type 1184 value in the message header is set to 8, from Table 1. 1186 The Session Termination Response message MAY contain one of each of 1187 the following data items: 1189 o Status (Section 9.1) 1191 A receiver of a Session Termination Response message without a Status 1192 data item MUST behave as if a Status data item with status code 1193 'Success', implying graceful termination, had been received. 1195 8.9. Destination Up Message 1197 A Destination Up message can be sent either by the modem, to indicate 1198 that a new remote node has been detected, or by the router, to 1199 indicate the presence of a new logical destination (e.g., a Multicast 1200 group) in the network. 1202 A Destination Up message MUST be acknowledged by the receiver issuing 1203 a Destination Up Response message (Section 8.10). The sender of the 1204 Destination Up message is free to define its retry heuristics in 1205 event of a timeout. When a Destination Up message is received and 1206 successfully processed, the receiver should add knowledge of the new 1207 destination to its information base, indicating that the destination 1208 is accessible via the modem/router pair. 1210 To construct a Destination Up message, the Message Type value in the 1211 message header is set to 9, from Table 1. 1213 The Destination Up message MUST contain one of each of the following 1214 data items: 1216 o MAC Address (Section 9.7) 1218 The Destination Up message MAY contain one of each of the following 1219 data items: 1221 o Maximum Data Rate (Receive) (Section 9.12) 1223 o Maximum Data Rate (Transmit) (Section 9.13) 1225 o Current Data Rate (Receive) (Section 9.14) 1227 o Current Data Rate (Transmit) (Section 9.15) 1229 o Latency (Section 9.16) 1231 o Resources (Receive) (Section 9.17) 1233 o Resources (Transmit) (Section 9.18) 1235 o Relative Link Quality (Receive) (Section 9.19) 1237 o Relative Link Quality (Transmit) (Section 9.20) 1239 The Destination Up message MAY contain one or more of the following 1240 data items, with different values: 1242 o IPv4 Address (Section 9.8) 1244 o IPv6 Address (Section 9.9) 1246 o IPv4 Attached Subnet (Section 9.10) 1248 o IPv6 Attached Subnet (Section 9.11) 1250 If the sender has IPv4 and/or IPv6 address information for a 1251 destination it SHOULD include the relevant data items in the 1252 Destination Up message, reducing the need for the receiver to probe 1253 for any address. 1255 8.10. Destination Up Response Message 1257 A DLEP participant MUST send a Destination Up Response message to 1258 indicate whether a Destination Up message (Section 8.9) was 1259 successfully processed. 1261 To construct a Destination Up Response message, the Message Type 1262 value in the message header is set to 10, from Table 1. 1264 The Destination Up Response message MUST contain one of each of the 1265 following data items: 1267 o MAC Address (Section 9.7) 1269 The Destination Up Response message MAY contain one of each of the 1270 following data items: 1272 o Status (Section 9.1) 1274 A receiver of a Destination Up Response message without a Status data 1275 item MUST behave as if a Status data item with status code 'Success' 1276 had been received. 1278 8.11. Destination Down Message 1280 A DLEP peer MUST send a Destination Down message to report when a 1281 destination (a remote node or a multicast group) is no longer 1282 reachable. A Destination Down Response message (Section 8.12) MUST 1283 be sent by the recipient of a Destination Down message to confirm 1284 that the relevant data has been removed from the information base. 1285 The sender of the Destination Down message is free to define its 1286 retry heuristics in event of a timeout. 1288 To construct a Destination Down message, the Message Type value in 1289 the message header is set to 11, from Table 1. 1291 The Destination Down message MUST contain one of each of the 1292 following data items: 1294 o MAC Address (Section 9.7) 1296 8.12. Destination Down Response Message 1298 A DLEP participant MUST send a Destination Down Response message to 1299 indicate whether a received Destination Down message (Section 8.11) 1300 was successfully processed. If successfully processed, the sender of 1301 the Response MUST have removed all entries in the information base 1302 that pertain to the referenced destination. 1304 To construct a Destination Down Response message, the Message Type 1305 value in the message header is set to 12, from Table 1. 1307 The Destination Down Response message MUST contain one of each of the 1308 following data items: 1310 o MAC Address (Section 9.7) 1311 The Destination Down Response message MAY contain one of each of the 1312 following data items: 1314 o Status (Section 9.1) 1316 A receiver of a Destination Down Response message without a Status 1317 data item MUST behave as if a Status data item with status code 1318 'Success' had been received. 1320 8.13. Destination Update Message 1322 A DLEP participant SHOULD send the Destination Update message when it 1323 detects some change in the information base for a given destination 1324 (remote node or multicast group). Some examples of changes that 1325 would prompt a Destination Update message are: 1327 o Change in link metrics (e.g., Data Rates) 1329 o Layer 3 addressing change 1331 To construct a Destination Update message, the Message Type value in 1332 the message header is set to 13, from Table 1. 1334 The Destination Update message MUST contain one of each of the 1335 following data items: 1337 o MAC Address (Section 9.7) 1339 The Destination Update message MAY contain one of each of the 1340 following data items: 1342 o Maximum Data Rate (Receive) (Section 9.12) 1344 o Maximum Data Rate (Transmit) (Section 9.13) 1346 o Current Data Rate (Receive) (Section 9.14) 1348 o Current Data Rate (Transmit) (Section 9.15) 1350 o Latency (Section 9.16) 1352 o Resources (Receive) (Section 9.17) 1354 o Resources (Transmit) (Section 9.18) 1356 o Relative Link Quality (Receive) (Section 9.19) 1358 o Relative Link Quality (Transmit) (Section 9.20) 1359 The Destination Update message MAY contain one or more of the 1360 following data items, with different values: 1362 o IPv4 Address (Section 9.8) 1364 o IPv6 Address (Section 9.9) 1366 8.14. Heartbeat Message 1368 A Heartbeat message SHOULD be sent by a DLEP participant every N 1369 seconds, where N is defined in the Heartbeat Interval data item of 1370 the Session Initialization message (Section 8.3) or Session 1371 Initialization Response message (Section 8.4). 1373 Note that implementations setting the Heartbeat Interval to 0 1374 effectively sets the interval to an infinite value, therefore this 1375 message SHOULD NOT be sent. 1377 The message is used by participants to detect when a DLEP session 1378 partner (either the modem or the router) is no longer communicating. 1379 Participants SHOULD allow two (2) heartbeat intervals to expire with 1380 no traffic on the router/modem session before initiating DLEP session 1381 termination procedures. 1383 To construct a Heartbeat message, the Message Type value in the 1384 message header is set to 14, from Table 1. 1386 There are no valid data items for the Heartbeat message. 1388 8.15. Link Characteristics Request Message 1390 The Link Characteristics Request message MAY be sent by the router to 1391 request that the modem initiate changes for specific characteristics 1392 of the link. The request can reference either a real destination 1393 (e.g., a remote node), or a logical destination (e.g., a multicast 1394 group) within the network. 1396 The Link Characteristics Request message MAY contain either a Current 1397 Data Rate (CDRR or CDRT) data item to request a different datarate 1398 than what is currently allocated, a Latency data item to request that 1399 traffic delay on the link not exceed the specified value, or both. A 1400 Link Characteristics Response message (Section 8.16) is required to 1401 complete the request. Issuing a Link Characteristics Request with 1402 ONLY the MAC Address data item is a mechanism a peer MAY use to 1403 request metrics (via the Link Characteristics Response) from its 1404 partner. 1406 The sender of a Link Characteristics Request message MAY attach a 1407 timer to the request using the Link Characteristics Response Timer 1408 data item. If a Link Characteristics Response message is received 1409 after the timer expires, the sender MUST NOT assume that the request 1410 succeeded. Implementations are free to define their retry heuristics 1411 in event of a timeout. 1413 To construct a Link Characteristics Request message, the Message Type 1414 value in the message header is set to 15, from Table 1. 1416 The Link Characteristics Request message MUST contain one of each of 1417 the following data items: 1419 o MAC Address (Section 9.7) 1421 The Link Characteristics Request message MAY contain one of each of 1422 the following data items: 1424 o Link Characteristics Response Timer (Section 9.21) 1426 o Current Data Rate (Receive) (Section 9.14) 1428 o Current Data Rate (Transmit) (Section 9.15) 1430 o Latency (Section 9.16) 1432 8.16. Link Characteristics Response Message 1434 A DLEP participant MUST send a Link Characteristics Response message 1435 to indicate whether a received Link Characteristics Request message 1436 (Section 8.15) was successfully processed. The Link Characteristics 1437 Response message SHOULD contain a complete set of metric data items, 1438 and MUST contain a full set (i.e. those declared in the Session 1439 Initialization Response message (Section 8.4)), if metrics were 1440 requested by only including a MAC address data item. It MUST contain 1441 the same metric types as the request. The values in the metric data 1442 items in the Link Characteristics Response message MUST reflect the 1443 link characteristics after the request has been processed. 1445 If an implementation is not able to alter the characteristics of the 1446 link in the manner requested, then a Status data item with status 1447 code 'Request Denied', see Table 3, MUST be added to the message. 1449 To construct a Link Characteristics Response message, the Message 1450 Type value in the message header is set to 16, from Table 1. 1452 The Link Characteristics Response message MUST contain one of each of 1453 the following data items: 1455 o MAC Address (Section 9.7) 1457 The Link Characteristics Response message SHOULD contain one of each 1458 of the following data items: 1460 o Maximum Data Rate (Receive) (Section 9.12) 1462 o Maximum Data Rate (Transmit) (Section 9.13) 1464 o Current Data Rate (Receive) (Section 9.14) 1466 o Current Data Rate (Transmit) (Section 9.15) 1468 o Latency (Section 9.16) 1470 The Link Characteristics Response message MAY contain one of each of 1471 the following data items: 1473 o Resources (Receive) (Section 9.17) 1475 o Resources (Transmit) (Section 9.18) 1477 o Relative Link Quality (Receive) (Section 9.19) 1479 o Relative Link Quality (Transmit) (Section 9.20) 1481 o Status (Section 9.1) 1483 A receiver of a Link Characteristics Response message without a 1484 Status data item MUST behave as if a Status data item with status 1485 code 'Success' had been received. 1487 9. DLEP Data Items 1489 Following is the list of core data items that MUST be recognized by a 1490 DLEP compliant implementation. As mentioned before, not all data 1491 items need be used during a session, but an implementation MUST 1492 correctly process these data items when correctly associated with a 1493 signal or message. 1495 The core DLEP data items are: 1497 +-------------+-----------------------------------------------------+ 1498 | Type Code | Description | 1499 +-------------+-----------------------------------------------------+ 1500 | 0 | Reserved | 1501 | 1 | Status (Section 9.1) | 1502 | 2 | IPv4 Connection Point (Section 9.2) | 1503 | 3 | IPv6 Connection Point (Section 9.3) | 1504 | 4 | Peer Type (Section 9.4) | 1505 | 5 | Heartbeat Interval (Section 9.5) | 1506 | 6 | Extensions Supported (Section 9.6) | 1507 | 7 | MAC Address (Section 9.7) | 1508 | 8 | IPv4 Address (Section 9.8) | 1509 | 9 | IPv6 Address (Section 9.9) | 1510 | 10 | IPv4 Attached Subnet (Section 9.10) | 1511 | 11 | IPv6 Attached Subnet (Section 9.11) | 1512 | 12 | Maximum Data Rate (Receive) MDRR) (Section 9.12) | 1513 | 13 | Maximum Data Rate (Transmit) (MDRT) (Section 9.13) | 1514 | 14 | Current Data Rate (Receive) (CDRR) (Section 9.14) | 1515 | 15 | Current Data Rate (Transmit) (CDRT) (Section 9.15) | 1516 | 16 | Latency (Section 9.16) | 1517 | 17 | Resources (Receive) (RESR) (Section 9.17) | 1518 | 18 | Resources (Transmit) (REST) (Section 9.18) | 1519 | 19 | Relative Link Quality (Receive) (RLQR) (Section | 1520 | | 9.19) | 1521 | 20 | Relative Link Quality (Transmit) (RLQT) (Section | 1522 | | 9.20) | 1523 | 21 | Link Characteristics Response Timer (Section 9.21) | 1524 | 22-24 | Credit Windowing (Section 10) extension data items | 1525 | 25-65407 | Reserved for future extensions | 1526 | 65408-65534 | Private Use. Available for experiments | 1527 | 65535 | Reserved | 1528 +-------------+-----------------------------------------------------+ 1530 Table 2: DLEP Data Item types 1532 9.1. Status 1534 The Status data item MAY appear in the Session Initialization 1535 Response (Section 8.4), Session Termination (Section 8.7), Session 1536 Termination Response (Section 8.8), Session Update Response 1537 (Section 8.6), Destination Up Response (Section 8.10), Destination 1538 Down Response (Section 8.12) and Link Characteristics Response 1539 (Section 8.16) messages. 1541 For the Session Termination message (Section 8.7), the Status data 1542 item indicates a reason for the termination. For all acknowledgement 1543 messages, the Status data item is used to indicate the success or 1544 failure of the previously received message. 1546 The status data item includes an optional Text field that can be used 1547 to provide a textual description of the status. The use of the Text 1548 field is entirely up to the receiving implementation, i.e., it could 1549 be output to a log file or discarded. If no Text field is supplied 1550 with the Status data item, the Length field MUST be set to 1. 1552 The Status data item contains the following fields: 1554 0 1 2 3 1555 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 1556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1557 | Data Item Type | Length | 1558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1559 | Code | Text... : 1560 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1562 Data Item Type: 1 1564 Length: 1 + Length of text, in octets 1566 Status Code: One of the codes defined in Table 3 below. 1568 Text: UTF-8 encoded string, describing the cause, used for 1569 implementation defined purposes. Since this field is used for 1570 description, implementations SHOULD limit characters in this field 1571 to printable characters. Implementations receiving this data item 1572 SHOULD check for printable characters in the field. 1574 An implementation MUST NOT assume the Text field is NUL-terminated. 1576 +-------------+---------+-----------+-------------------------------+ 1577 | Status Code | Value | Failure | Reason | 1578 | | | Mode | | 1579 +-------------+---------+-----------+-------------------------------+ 1580 | Success | 0 | Success | The message was processed | 1581 | | | | successfully. | 1582 | Unknown | 1 | Terminate | The message was not | 1583 | Message | | | recognized by the | 1584 | | | | implementation. | 1585 | Unexpected | 2 | Terminate | The message was not expected | 1586 | Message | | | while the device was in the | 1587 | | | | current state, e.g., a | 1588 | | | | Session Initialization | 1589 | | | | message (Section 8.3) in the | 1590 | | | | In-Session state. | 1591 | Invalid | 3 | Terminate | One or more data items in the | 1592 | Data | | | message are invalid, | 1593 | | | | unexpected or incorrectly | 1594 | | | | duplicated. | 1595 | Invalid | 4 | Terminate | The destination provided in | 1596 | Destination | | | the message does not match a | 1597 | | | | previously announced | 1598 | | | | destination. For example, in | 1599 | | | | the Link Characteristic | 1600 | | | | Response message (Section | 1601 | | | | 8.16). | 1602 | | 5-90 | Terminate | Reserved for future | 1603 | | | | extensions. | 1604 | | | | | 1606 | Not | 100 | Continue | The receiver is not | 1607 | Interested | | | interested in this message | 1608 | | | | subject, e.g. a Destination | 1609 | | | | Up Response message (Section | 1610 | | | | 8.10) to indicate no further | 1611 | | | | messages about the | 1612 | | | | destination. | 1613 | Request | 101 | Continue | The receiver refuses to | 1614 | Denied | | | complete the request. | 1615 | Timed Out | 102 | Continue | The operation could not be | 1616 | | | | completed in the time | 1617 | | | | allowed. | 1618 | | 103-243 | Continue | Reserved for future | 1619 | | | | extensions. | 1620 | | | | | 1622 | | 255 | Terminate | Reserved. | 1623 +-------------+---------+-----------+-------------------------------+ 1625 Table 3: DLEP Status Codes 1627 A failure mode of 'Terminate' indicates that the session MUST be 1628 terminated after sending a response containing the status code. A 1629 failure mode of 'Continue' indicates that the session SHOULD continue 1630 as normal. 1632 9.2. IPv4 Connection Point 1634 The IPv4 Connection Point data item MAY appear in the Peer Offer 1635 signal (Section 8.2). 1637 The IPv4 Connection Point data item indicates the IPv4 address and, 1638 optionally, the TCP port number on the DLEP modem available for 1639 connections. If provided, the receiver MUST use this information to 1640 perform the TCP connect to the DLEP server. 1642 The IPv4 Connection Point data item contains the following fields: 1644 0 1 2 3 1645 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 1646 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1647 | Data Item Type | Length | 1648 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1649 | Use TLS | IPv4 Address... : 1650 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1651 : ...cont. | TCP Port Number (optional) | 1652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1654 Data Item Type: 2 1656 Length: 5 (or 7 if TCP Port included) 1658 Use TLS: Value indicating whether the TCP connection should use TLS 1659 (1), or not (0). Values other than 0 or 1 MUST be considered as 1660 invalid. 1662 IPv4 Address: The IPv4 address listening on the DLEP modem. 1664 TCP Port Number: TCP Port number on the DLEP modem. 1666 If the Length field is 7, the port number specified MUST be used to 1667 establish the TCP session. If the TCP Port Number is omitted, i.e. 1668 the Length field is 5, the receiver MUST use the DLEP well-known port 1669 number (Section 12.7) to establish the TCP connection. 1671 9.3. IPv6 Connection Point 1673 The IPv6 Connection Point data item MAY appear in the Peer Offer 1674 signal (Section 8.2). 1676 The IPv6 Connection Point data item indicates the IPv6 address and, 1677 optionally, the TCP port number on the DLEP modem available for 1678 connections. If provided, the receiver MUST use this information to 1679 perform the TCP connect to the DLEP server. 1681 The IPv6 Connection Point data item contains the following fields: 1683 0 1 2 3 1684 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 1685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1686 | Data Item Type | Length | 1687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1688 | Use TLS | IPv6 Address : 1689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1690 : IPv6 Address : 1691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1692 : IPv6 Address : 1693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1694 : IPv6 Address : 1695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1696 : ...cont. | TCP Port Number (optional) | 1697 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 Data Item Type: 3 1701 Length: 17 (or 19 if TCP Port included) 1703 Use TLS: Value indicating whether the TCP connection should use TLS 1704 (1), or not (0). Values other than 0 or 1 MUST be considered as 1705 invalid. 1707 IPv6 Address: The IPv6 address listening on the DLEP modem. 1709 TCP Port Number: TCP Port number on the DLEP modem. 1711 If the Length field is 19, the port number specified MUST be used to 1712 establish the TCP session. If the TCP Port Number is omitted, i.e. 1713 the Length field is 17, the receiver MUST use the DLEP well-known 1714 port number (Section 12.7) to establish the TCP connection. 1716 9.4. Peer Type 1718 The Peer Type data item MAY appear in the Peer Discovery 1719 (Section 8.1) and Peer Offer (Section 8.2) signals, and the Session 1720 Initialization (Section 8.3) and Session Initialization Response 1721 (Section 8.4) messages. 1723 The Peer Type data item is used by the router and modem to give 1724 additional information as to its type. The peer type is a string and 1725 is envisioned to be used for informational purposes (e.g., as output 1726 in a display command). 1728 The Peer Type data item contains the following fields: 1730 0 1 2 3 1731 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 1732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1733 | Data Item Type | Length | 1734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1735 | Peer Type... : 1736 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1738 Data Item Type: 4 1740 Length: Length of peer type string, in octets. 1742 Peer Type: UTF-8 encoded string. For example, a satellite modem 1743 might set this variable to "Satellite terminal". Since this data 1744 item is intended to provide additional information for display 1745 commands, sending implementations SHOULD limit the data to 1746 printable characters, and receiving implmentations SHOULD check 1747 the data for printable characters. 1749 An implementation MUST NOT assume the Peer Type field is NUL- 1750 terminated. 1752 9.5. Heartbeat Interval 1754 The Heartbeat Interval data item MUST appear in both the Session 1755 Initialization (Section 8.3) and Session Initialization Response 1756 (Section 8.4) messages to indicate the Heartbeat timeout window to be 1757 used by the sender. 1759 The Interval is used to specify a period (in seconds) for Heartbeat 1760 messages (Section 8.14). By specifying an Interval value of 0, 1761 implementations MAY indicate the desire to disable Heartbeat messages 1762 entirely (i.e., the Interval is set to an infinite value). However, 1763 it is RECOMMENDED that implementations use non-0 timer values. 1765 The Heartbeat Interval data item contains the following fields: 1767 0 1 2 3 1768 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 1769 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1770 | Data Item Type | Length | 1771 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1772 | Interval | 1773 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1775 Data Item Type: 5 1777 Length: 2 1778 Interval: 0 = Do not use heartbeats on this DLEP session. Non-zero 1779 = Interval, in seconds, for heartbeat messages. 1781 9.6. Extensions Supported 1783 The Extensions Supported data item MAY be used in both the Session 1784 Initialization (Section 8.3) and Session Initialization Response 1785 (Section 8.4) messages. 1787 The Extensions Supported data item is used by the router and modem to 1788 negotiate additional optional functionality they are willing to 1789 support. The Extensions List is a concatenation of the types of each 1790 supported extension, found in the IANA DLEP Extensions repository. 1791 Each Extension Type definition includes which additional signals and 1792 data-items are supported. 1794 The Extensions Supported data item contains the following fields: 1796 0 1 2 3 1797 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 1798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1799 | Data Item Type | Length | 1800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1801 | Extensions List... 1802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1804 Data Item Type: 6 1806 Length: Length of the extensions list in octets. This is twice (2x) 1807 the number of extensions. 1809 Extension List: A list of extensions supported, identified by their 1810 2-octet value as listed in the extensions registry. 1812 9.7. MAC Address 1814 The MAC address data item MUST appear in all destination-oriented 1815 messages (i.e., Destination Up (Section 8.9), Destination Up Response 1816 (Section 8.10), Destination Down (Section 8.11), Destination Down 1817 Response (Section 8.12), Destination Update (Section 8.13), Link 1818 Characteristics Request (Section 8.15), and Link Characteristics 1819 Response (Section 8.16)). 1821 The MAC Address data item contains the address of the destination on 1822 the remote node. The MAC address MAY be either a physical or a 1823 virtual destination, and MAY be expressed in EUI-48 or EUI-64 format. 1824 Examples of a virtual destination would be a multicast MAC address, 1825 or the broadcast MAC (FF:FF:FF:FF:FF:FF). 1827 0 1 2 3 1828 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 1829 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1830 | Data Item Type | Length | 1831 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1832 | MAC Address : 1833 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1834 : MAC Address : 1835 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1836 : MAC Address : (if EUI-64 used) | 1837 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1839 Data Item Type: 7 1841 Length: 6 for EUI-48 format, or 8 for EUI-64 format 1843 MAC Address: MAC Address of the destination. 1845 9.8. IPv4 Address 1847 The IPv4 Address data item MAY appear in the Session Update 1848 (Section 8.5), Destination Up (Section 8.9) and Destination Update 1849 (Section 8.13) messages. 1851 When included in Destination messages, this data item contains the 1852 IPv4 address of the destination. When included in the Session Update 1853 message, this data item contains the IPv4 address of the peer. In 1854 either case, the data item also contains an indication of whether 1855 this is a new or existing address, or is a deletion of a previously 1856 known address. 1858 The IPv4 Address data item contains the following fields: 1860 0 1 2 3 1861 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 1862 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1863 | Data Item Type | Length | 1864 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1865 | Add/Drop | IPv4 Address : 1866 | Indicator | : 1867 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1868 : IPv4 | 1869 : Address | 1870 +-+-+-+-+-+-+-+-+ 1872 Data Item Type: 8 1874 Length: 5 1875 Add/Drop: Value indicating whether this is a new or existing address 1876 (1), or a withdrawal of an address (0). Values other than 0 or 1 1877 MUST be considered as invalid. 1879 IPv4 Address: The IPv4 address of the destination or peer. 1881 9.9. IPv6 Address 1883 The IPv6 Address data item MAY appear in the Session Update 1884 (Section 8.5), Destination Up (Section 8.9) and Destination Update 1885 (Section 8.13) messages. When included in Destination messages, this 1886 data item contains the IPv6 address of the destination. When 1887 included in the Session Update message, this data item contains the 1888 IPv6 address of the peer. In either case, the data item also 1889 contains an indication of whether this is a new or existing address, 1890 or is a deletion of a previously known address. 1892 The IPv6 Address data item contains the following fields: 1894 0 1 2 3 1895 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 1896 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1897 | Data Item Type | Length | 1898 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1899 | Add/Drop | IPv6 Address : 1900 | Indicator | : 1901 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1902 : IPv6 Address : 1903 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1904 : IPv6 Address : 1905 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1906 : IPv6 Address : 1907 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1908 : IPv6 Address | 1909 +-+-+-+-+-+-+-+-+ 1911 Data Item Type: 9 1913 Length: 17 1915 Add/Drop: Value indicating whether this is a new or existing address 1916 (1), or a withdrawal of an address (0). Values other than 0 or 1 1917 MUST be considered as invalid. 1919 IPv6 Address: IPv6 Address of the destination or peer. 1921 9.10. IPv4 Attached Subnet 1923 The DLEP IPv4 Attached Subnet allows a device to declare that it has 1924 an IPv4 subnet (e.g., a stub network) attached, or that it has become 1925 aware of an IPv4 subnet being present at a remote destination. The 1926 IPv4 Attached Subnet data item MAY appear in the Destination Up 1927 (Section 8.9) message. Once an IPv4 Subnet has been declared on a 1928 device, the declaration SHALL NOT be withdrawn without withdrawing 1929 the destination (via the Destination Down message (Section 8.11)) and 1930 re-issuing the Destination Up message. 1932 The DLEP IPv4 Attached Subnet data item contains the following 1933 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 | IPv4 Attached Subnet | 1941 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1942 | Prefix Len. | 1943 +-+-+-+-+-+-+-+-+ 1945 Data Item Type: 10 1947 Length: 5 1949 IPv4 Subnet: The IPv4 subnet reachable at the destination. 1951 Prefix Length: Length of the prefix (1-32) for the IPv4 subnet. A 1952 prefix length outside the speficied range MUST be considered as 1953 invalid. 1955 9.11. IPv6 Attached Subnet 1957 The DLEP IPv6 Attached Subnet allows a device to declare that it has 1958 an IPv6 subnet (e.g., a stub network) attached, or that it has become 1959 aware of an IPv6 subnet being present at a remote destination. The 1960 IPv6 Attached Subnet data item MAY appear in the Destination Up 1961 (Section 8.9) message. As in the case of the IPv4 attached Subnet 1962 data item above, once an IPv6 attached subnet has been declared, it 1963 SHALL NOT be withdrawn without withdrawing the destination (via the 1964 Destination Down message (Section 8.11)) and re-issuing the 1965 Destination Up message. 1967 The DLEP IPv6 Attached Subnet data item contains the following 1968 fields: 1970 0 1 2 3 1971 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 1972 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1973 | Data Item Type | Length | 1974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1975 | IPv6 Attached Subnet : 1976 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1977 : IPv6 Attached Subnet : 1978 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1979 : IPv6 Attached Subnet : 1980 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1981 : IPv6 Attached Subnet | 1982 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1983 | Prefix Len. | 1984 +-+-+-+-+-+-+-+-+ 1986 Data Item Type: 11 1988 Length: 17 1990 IPv4 Subnet: The IPv6 subnet reachable at the destination. 1992 Prefix Length: Length of the prefix (1-128) for the IPv6 subnet. A 1993 prefix length outside the specified range MUST be considered as 1994 invalid. 1996 9.12. Maximum Data Rate (Receive) 1998 The Maximum Data Rate (Receive) (MDRR) data item MUST appear in the 1999 Session Initialization Response message (Section 8.4), and MAY appear 2000 in the Session Update (Section 8.5), Destination Up (Section 8.9), 2001 Destination Update (Section 8.13) and Link Characteristics Response 2002 (Section 8.16) messages to indicate the maximum theoretical data 2003 rate, in bits per second, that can be achieved while receiving data 2004 on the link. 2006 The Maximum Data Rate (Receive) data item contains the following 2007 fields: 2009 0 1 2 3 2010 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 2011 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2012 | Data Item Type | Length | 2013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2014 | MDRR (bps) : 2015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2016 : MDRR (bps) | 2017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2018 Data Item Type: 12 2020 Length: 8 2022 Maximum Data Rate (Receive): A 64-bit unsigned integer, representing 2023 the maximum theoretical data rate, in bits per second (bps), that 2024 can be achieved while receiving on the link. 2026 9.13. Maximum Data Rate (Transmit) 2028 The Maximum Data Rate (Transmit) (MDRT) data item MUST appear in the 2029 Session Initialization Response message (Section 8.4), and MAY appear 2030 in the Session Update (Section 8.5), Destination Up (Section 8.9), 2031 Destination Update (Section 8.13) and Link Characteristics Response 2032 (Section 8.16) messages to indicate the maximum theoretical data 2033 rate, in bits per second, that can be achieved while transmitting 2034 data on the link. 2036 The Maximum Data Rate (Transmit) data item contains the following 2037 fields: 2039 0 1 2 3 2040 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 2041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2042 | Data Item Type | Length | 2043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2044 | MDRT (bps) : 2045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2046 : MDRT (bps) | 2047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2049 Data Item Type: 13 2051 Length: 8 2053 Maximum Data Rate (Transmit): A 64-bit unsigned integer, 2054 representing the maximum theoretical data rate, in bits per second 2055 (bps), that can be achieved while transmitting on the link. 2057 9.14. Current Data Rate (Receive) 2059 The Current Data Rate (Receive) (CDRR) data item MUST appear in the 2060 Session Initialization Response message (Section 8.4), and MAY appear 2061 in the Session Update (Section 8.5), Destination Up (Section 8.9), 2062 Destination Update (Section 8.13) and Link Characteristics Response 2063 (Section 8.16) messages to indicate the rate at which the link is 2064 currently operating for receiving traffic. 2066 When used in the Link Characteristics Request message (Section 8.15), 2067 CDRR represents the desired receive rate, in bits per second, on the 2068 link. 2070 The Current Data Rate (Receive) data item contains the following 2071 fields: 2073 0 1 2 3 2074 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 2075 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2076 | Data Item Type | Length | 2077 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2078 | CDRR (bps) : 2079 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2080 : CDRR (bps) | 2081 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2083 Data Item Type: 14 2085 Length: 8 2087 Current Data Rate (Receive): A 64-bit unsigned integer, representing 2088 the current data rate, in bits per second, that can currently be 2089 achieved while receiving traffic on the link. 2091 If there is no distinction between current and maximum receive data 2092 rates, current data rate receive MUST be set equal to the maximum 2093 data rate receive. 2095 9.15. Current Data Rate (Transmit) 2097 The Current Data Rate Transmit (CDRT) data item MUST appear in the 2098 Session Initialization Response message (Section 8.4), and MAY appear 2099 in the Session Update (Section 8.5), Destination Up (Section 8.9), 2100 Destination Update (Section 8.13), and Link Characteristics Response 2101 (Section 8.16) messages to indicate the rate at which the link is 2102 currently operating for transmitting traffic. 2104 When used in the Link Characteristics Request message (Section 8.15), 2105 CDRT represents the desired transmit rate, in bits per second, on the 2106 link. 2108 The Current Data Rate (Transmit) data item contains the following 2109 fields: 2111 0 1 2 3 2112 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 2113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2114 | Data Item Type | Length | 2115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2116 | CDRT (bps) : 2117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2118 : CDRT (bps) | 2119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2121 Data Item Type: 15 2123 Length: 8 2125 Current Data Rate (Transmit): A 64-bit unsigned integer, 2126 representing the current data rate, in bits per second, that can 2127 currently be achieved while transmitting traffic on the link. 2129 If there is no distinction between current and maximum transmit data 2130 rates, current data rate transmit MUST be set equal to the maximum 2131 data rate transmit. 2133 9.16. Latency 2135 The Latency data item MUST appear in the Session Initialization 2136 Response message (Section 8.4), and MAY appear in the Session Update 2137 (Section 8.5), Destination Up (Section 8.9), Destination Update 2138 (Section 8.13), and Link Characteristics Response (Section 8.16) 2139 messages to indicate the amount of latency, in microseconds, on the 2140 link. 2142 When used in the Link Characteristics Request message (Section 8.15), 2143 Latency represents the maximum latency desired on the link. 2145 The Latency value is reported as delay. The calculation of latency 2146 is implementation dependent. For example, the latency may be a 2147 running average calculated from the internal queuing. 2149 0 1 2 3 2150 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 2151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2152 | Data Item Type | Length | 2153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2154 | Latency : 2155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2156 : Latency | 2157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2158 Data Item Type: 16 2160 Length: 8 2162 Latency: A 64-bit unsigned integer, representing the transmission 2163 delay, in microseconds, that a packet encounters as it is 2164 transmitted over the link. 2166 9.17. Resources (Receive) 2168 The Resources (Receive) (RESR) data item MAY appear in the Session 2169 Initialization Response message (Section 8.4), Session Update 2170 (Section 8.5), Destination Up (Section 8.9), Destination Update 2171 (Section 8.13) and Link Characteristics Response (Section 8.16) 2172 messages to indicate the amount of resources for reception (with 0 2173 meaning 'no resources available', and 100 meaning 'all resources 2174 available') at the destination. The list of resources that might be 2175 considered is beyond the scope of this document, and is left to 2176 implementations to decide. 2178 The Resources (Receive) data item contains the following fields: 2180 0 1 2 3 2181 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 2182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2183 | Data Item Type | Length | 2184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2185 | RESR | 2186 +-+-+-+-+-+-+-+-+ 2188 Data Item Type: 17 2190 Length: 1 2192 Resources (Receive): An 8-bit integer percentage, 0-100, 2193 representing the amount of resources allocated to receiving data. 2194 Any value greater than 100 MUST be considered as invalid. 2196 If a device cannot calculate RESR, this data item SHOULD NOT be 2197 issued. 2199 9.18. Resources (Transmit) 2201 The Resources (Transmit) (REST) data item MAY appear in the Session 2202 Initialization Response message (Section 8.4), Session Update 2203 (Section 8.5), Destination Up (Section 8.9), Destination Update 2204 (Section 8.13) and Link Characteristics Response (Section 8.16) 2205 messages to indicate the amount of resources for transmission (with 0 2206 meaning 'no resources available', and 100 meaning 'all resources 2207 available') at the destination. The list of resources that might be 2208 considered is beyond the scope of this document, and is left to 2209 implementations to decide. 2211 The Resources (Transmit) data item contains the following fields: 2213 0 1 2 3 2214 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 2215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2216 | Data Item Type | Length | 2217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2218 | REST | 2219 +-+-+-+-+-+-+-+-+ 2221 Data Item Type: 18 2223 Length: 1 2225 Resources (Transmit): An 8-bit integer percentage, 0-100, 2226 representing the amount of resources allocated to transmitting 2227 data. Any value greater than 100 MUST be considered as invalid. 2229 If a device cannot calculate REST, this data item SHOULD NOT be 2230 issued. 2232 9.19. Relative Link Quality (Receive) 2234 The Relative Link Quality (Receive) (RLQR) data item MAY appear in 2235 the Session Initialization Response message (Section 8.4), Session 2236 Update (Section 8.5), Destination Up (Section 8.9), Destination 2237 Update (Section 8.13) and Link Characteristics Response 2238 (Section 8.16) messages to indicate the quality of the link for 2239 receiving data. 2241 The Relative Link Quality (Receive) data item contains the following 2242 fields: 2244 0 1 2 3 2245 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 2246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2247 | Data Item Type | Length | 2248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2249 | RLQR | 2250 +-+-+-+-+-+-+-+-+ 2252 Data Item Type: 19 2253 Length: 1 2255 Relative Link Quality (Receive): A non-dimensional 8-bit integer, 2256 0-100, representing relative link quality. A value of 100 2257 represents a link of the highest quality. Any value greater than 2258 100 MUST be considered as invalid. 2260 If a device cannot calculate the RLQR, this data item SHOULD NOT be 2261 issued. 2263 9.20. Relative Link Quality (Transmit) 2265 The Relative Link Quality (Transmit) (RLQT) data item MAY appear in 2266 the Session Initialization Response message (Section 8.4), Session 2267 Update (Section 8.5), Destination Up (Section 8.9), Destination 2268 Update (Section 8.13) and Link Characteristics Response 2269 (Section 8.16) messages to indicate the quality of the link for 2270 transmitting data. 2272 The Relative Link Quality (Transmit) data item contains the following 2273 fields: 2275 0 1 2 3 2276 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 2277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2278 | Data Item Type | Length | 2279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2280 | RLQT | 2281 +-+-+-+-+-+-+-+-+ 2283 Data Item Type: 20 2285 Length: 1 2287 Relative Link Quality (Transmit): A non-dimensional 8-bit integer, 2288 0-100, representing relative link quality. A value of 100 2289 represents a link of the highest quality. Any value greater than 2290 100 MUST be considered as invalid. 2292 If a device cannot calculate the RLQT, this data item SHOULD NOT be 2293 issued. 2295 9.21. Link Characteristics Response Timer 2297 The Link Characteristics Response Timer data item MAY appear in the 2298 Link Characteristics Request message (Section 8.15) to indicate the 2299 desired number of seconds the sender will wait for a response to the 2300 request. If this data item is omitted, implementations supporting 2301 the Link Characteristics Request SHOULD choose a default value. 2303 The Link Characteristics Response Timer data item contains the 2304 following fields: 2306 0 1 2 3 2307 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 2308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2309 | Data Item Type | Length | 2310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2311 | Interval | 2312 +-+-+-+-+-+-+-+-+ 2314 Data Item Type: 21 2316 Length: 1 2318 Interval: 0 = Do not use timeouts for this Link Characteristics 2319 request. Non-zero = Interval, in seconds, to wait before 2320 considering this Link Characteristics Request lost. 2322 10. Credit-Windowing 2324 DLEP includes an optional Protocol Extension for a credit-windowing 2325 scheme analogous to the one documented in [RFC5578]. In this scheme, 2326 data plane traffic flowing between the router and modem is controlled 2327 by the availability of credits. Credits are expressed as if two 2328 unidirectional windows exist between the modem and router. This 2329 document identifies these windows as the 'Modem Receive Window' 2330 (MRW), and the 'Router Receive Window' (RRW). 2332 If the credit-windowing extension is used, credits MUST be granted by 2333 the receiver on a given window - that is, on the 'Modem Receive 2334 Window' (MRW), the modem is responsible for granting credits to the 2335 router, allowing it (the router) to send data plane traffic to the 2336 modem. Likewise, the router is responsible for granting credits on 2337 the RRW, which allows the modem to send data plane traffic to the 2338 router. 2340 Credits are managed on a destination-specific basis; that is, 2341 separate credit counts are maintained for each destination requiring 2342 the service. Credits do not apply to the DLEP session that exists 2343 between routers and modems; they are applied only to the data plane 2344 traffic. 2346 Credits represent the number of octets, or an increment in the number 2347 of octets, that MAY be sent on the given window. When sending data 2348 plane traffic to a credit-enabled peer, the sender MUST decrement the 2349 appropriate window by the size of the data being sent. For example, 2350 when sending data plane traffic via the modem, the router MUST 2351 decriment the 'Modem Receive Window' (MRW) for the corresponding 2352 destination. When the number of available credits to the destination 2353 reaches 0, a sender MUST stop sending data plane traffic to the 2354 destination, until additional credits are supplied. 2356 If a peer is able to support the optional credit-windowing extension 2357 then it MUST include an Extensions Supported data item (Section 9.6) 2358 including the value 1, from Table 4, in the appropriate Session 2359 Initialization (Section 8.3) and Session Initialization Response 2360 (Section 8.4) message. 2362 10.1. Credit-Windowing Messages 2364 The credit-windowing extension introduces no additional DLEP signals 2365 or messages. However, if a peer has advertised during session 2366 initialization that it supports the credit-windowing extension then 2367 the following DLEP messages MAY contain additional credit-windowing 2368 data items: 2370 10.1.1. Destination Up Message 2372 The Destination Up message MAY contain one of each of the following 2373 data items: 2375 o Credit Grant (Section 10.2.1) 2377 If the Destination Up message does not contain the Credit Grant data 2378 item, credits MUST NOT be used for that destination. 2380 10.1.2. Destination Up Response Message 2382 If the corresponding Destination Up message contained the Credit 2383 Grant data item, the Destination Up Response message MUST contain one 2384 of each of the following data items: 2386 o Credit Window Status (Section 10.2.2) 2388 10.1.3. Destination Update Message 2390 If the corresponding Destination Up message contained the Credit 2391 Grant data item, the Destination Update message MUST contain one of 2392 each of the following data items: 2394 o Credit Window Status (Section 10.2.2) 2395 If the corresponding Destination Up message contained the Credit 2396 Grant data item, the Destination Update message MAY contain one of 2397 each of the following data items: 2399 o Credit Grant (Section 10.2.1) 2401 o Credit Request (Section 10.2.3) 2403 10.2. Credit-Windowing Data Items 2405 The credit-windowing extension introduces 3 additional data items. 2406 If a peer has advertised during session initialization that it 2407 supports the credit-windowing extension then it MUST correctly 2408 process the following data items: 2410 +------------+------------------------------------------------------+ 2411 | Type Code | Description | 2412 +------------+------------------------------------------------------+ 2413 | 22 | Credit Grant (Section 10.2.1) | 2414 | 23 | Credit Window Status (Section 10.2.2) | 2415 | 24 | Credit Request (Section 10.2.3) | 2416 +------------+------------------------------------------------------+ 2418 10.2.1. Credit Grant 2420 The Credit Grant data item is sent from a DLEP participant to grant 2421 an increment to credits on a window. The Credit Grant data item MAY 2422 appear in the Destination Up (Section 8.9) and Destination Update 2423 (Section 8.13) messages. The value in a Credit Grant data item 2424 represents an increment to be added to any existing credits available 2425 on the window. Upon successful receipt and processing of a Credit 2426 Grant data item, the receiver MUST respond with a message containing 2427 a Credit Window Status data item to report the updated aggregate 2428 values for synchronization purposes, and if initializing a new credit 2429 window, granting initial credits. 2431 When DLEP peers desire to employ the credit-windowing extension, the 2432 peer originating the Destination Up message MUST supply an initial, 2433 non-zero value as the credit increment of the receive window it 2434 controls (i.e., the Modem Receive Window, or Router Receive Window). 2435 When receiving a Credit Grant data item on a Destination Up message, 2436 the receiver MUST take one of the following actions: 2438 1. Reject the use of credits for this destination, via the 2439 Destination Up Response message containing a Status data item 2440 (Section 9.1) with a status code of 'Request Denied'. (See 2441 Table 3), or 2443 2. Initialize the appropriate window value of zero, then apply the 2444 increment specified in the Credit Grant data item. 2446 If the initialization completes successfully, the receiver MUST 2447 respond to the Destination Up message with a Destination Up Response 2448 message that contains a Credit Window Status data item, initializing 2449 its receive window. 2451 The Credit Grant data item contains the following fields: 2453 0 1 2 3 2454 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 2455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2456 | Data Item Type | Length | 2457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2458 | Credit Increment : 2459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2460 : Credit Increment | 2461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2463 Data Item Type: 22 2465 Length: 8 2467 Reserved: A 64-bit unsigned integer representing the additional 2468 credits to be assigned to the credit window. 2470 Since credits can only be granted by the receiver on a window, the 2471 applicable credit window (either the MRW or the RRW) is derived from 2472 the sender of the grant. The Credit Increment MUST NOT cause the 2473 window to overflow; if this condition occurs, implementations MUST 2474 set the credit window to the maximum value contained in a 64-bit 2475 quantity. 2477 10.2.2. Credit Window Status 2479 If the credit-window extension is supported by the DLEP participants 2480 (both the router and the modem), the Credit Window Status data item 2481 MUST be sent by the participant receiving a Credit Grant for a given 2482 destination. 2484 The Credit Window Status data item contains the following fields: 2486 0 1 2 3 2487 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 2488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2489 | Data Item Type | Length | 2490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2491 | Modem Receive Window Value : 2492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2493 : Modem Receive Window Value | 2494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2495 | Router Receive Window Value : 2496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2497 : Router Receive Window Value | 2498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2500 Data Item Type: 23 2502 Length: 16 2504 Modem Receive Window Value: A 64-bit unsigned integer, indicating 2505 the current number of credits available on the Modem Receive 2506 Window, for the destination referred to by the message. 2508 Router Receive Window Value: A 64-bit unsigned integer, indicating 2509 the current number of credits available on the Router Receive 2510 Window, for the destination referred to by the message. 2512 10.2.3. Credit Request 2514 The Credit Request data item MAY be sent from either DLEP 2515 participant, via the Destination Update message (Section 8.13), to 2516 indicate the desire for the partner to grant additional credits in 2517 order for data transfer to proceed on the session. If the 2518 corresponding Destination Up message (Section 8.9) for this session 2519 did not contain a Credit Window Status data item, indicating that 2520 credits are to be used on the session, then the Credit Request data 2521 item MUST be silently dropped by the receiver. 2523 The Credit Request data item contains the following fields: 2525 0 1 2 3 2526 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 2527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2528 | Data Item Type | Length | 2529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2531 Data Item Type: 24 2533 Length: 0 2535 11. Security Considerations 2537 The potential security concerns when using DLEP are: 2539 1. DLEP peers may be 'spoofed' by an attacker, either at DLEP 2540 session initialization, or by injection of messages once a 2541 session has been established, and/or 2543 2. DLEP data items could be altered by an attacker, causing the 2544 receiving peer to inappropriately alter its information base 2545 concerning network status. 2547 If the modem and router are separated by more than a single hop, 2548 session messages could be altered in order to subvert the behaviour 2549 of either or both DLEP participants. Under these circumstances, the 2550 use of [TLS] is strongly RECOMMENDED. However, if both devices are 2551 directly physically connected, or exist within an externally secured 2552 private network then an implementation MAY choose not to use TLS. 2554 To avoid potential denial of service attack, it is RECOMMENDED that 2555 implementations using the Peer Discovery mechanism maintain an 2556 information base of peers that persistently fail Session 2557 initialization having provided an acceptable Discovery signal, and 2558 ignore discovery signals from such peers. 2560 This specification does not address security of the data plane, as it 2561 (the data plane) is not affected, and standard security procedures 2562 can be employed. 2564 12. IANA Considerations 2566 This section specifies requests to IANA. 2568 12.1. Registrations 2570 This specification defines: 2572 o A new repository for DLEP signals and messages, with sixteen (16) 2573 values currently assigned. 2575 o Reservation of a Private Use numbering space for experimental DLEP 2576 signals and messages. 2578 o A new repository for DLEP data items, with twenty-four (24) values 2579 currently assigned. 2581 o Reservation of a Private Use numbering space in the data items 2582 repository for experimental data items. 2584 o A new repository for DLEP status codes, with eight (8) currently 2585 assigned. 2587 o Reservation of a Private Use numbering space in the status codes 2588 repository for experimental status codes. 2590 o A new repository for DLEP extensions, with one (1) value currently 2591 assigned. 2593 o Reservation of a Private Use numbering space in the extension 2594 repository for experimental extensions. 2596 o A request for allocation of a well-known port for DLEP TCP and UDP 2597 communication. 2599 o A request for allocation of a multicast IP address for DLEP 2600 discovery. 2602 12.2. Expert Review: Evaluation Guidelines 2604 No additional guidelines for expert review are anticipated. 2606 12.3. Signal/Message Type Registration 2608 A new repository must be created with the values of the DLEP signals 2609 and messages. 2611 All signal and message values are in the range [0..65535], defined in 2612 Table 1. 2614 12.4. DLEP Data Item Registrations 2616 A new repository for DLEP data items must be created. 2618 All data item values are in the range [0..65535], defined in Table 2. 2620 12.5. DLEP Status Code Registrations 2622 A new repository for DLEP status codes must be created. 2624 All status codes are in the range [0..255], defined in Table 3. 2626 12.6. DLEP Extensions Registrations 2628 A new repository for DLEP extensions must be created. 2630 All extension values are in the range [0..65535]. Current 2631 allocations are: 2633 +-------------+-----------------------------------------------------+ 2634 | Code | Description | 2635 +-------------+-----------------------------------------------------+ 2636 | 0 | Reserved | 2637 | 1 | Credit Windowing (Section 10) | 2638 | 2-65519 | Reserved for future extensions | 2639 | 65520-65534 | Private Use. Available for experiments | 2640 | 65535 | Reserved | 2641 +-------------+-----------------------------------------------------+ 2643 Table 4: DLEP Extension types 2645 12.7. DLEP Well-known Port 2647 It is requested that IANA allocate a well-known port number for DLEP 2648 communication. 2650 12.8. DLEP Multicast Address 2652 It is requested that IANA allocate a multicast address for DLEP 2653 discovery signals. 2655 13. Acknowledgements 2657 We would like to acknowledge and thank the members of the DLEP design 2658 team, who have provided invaluable insight. The members of the 2659 design team are: Teco Boot, Bow-Nan Cheng, John Dowdell, and Henning 2660 Rogge. 2662 We would also like to acknowledge the influence and contributions of 2663 Greg Harrison, Chris Olsen, Martin Duke, Subir Das, Jaewon Kang, 2664 Vikram Kaul, Nelson Powell and Victoria Mercieca. 2666 14. References 2668 14.1. Normative References 2670 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2671 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 2672 RFC2119, March 1997, 2673 . 2675 14.2. Informative References 2677 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 2678 (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/ 2679 RFC5246, August 2008, 2680 . 2682 [RFC5578] Berry, B., Ed., Ratliff, S., Paradise, E., Kaiser, T., and 2683 M. Adams, "PPP over Ethernet (PPPoE) Extensions for Credit 2684 Flow and Link Metrics", RFC 5578, DOI 10.17487/RFC5578, 2685 February 2010, . 2687 Appendix A. Discovery Signal Flows 2689 Router Modem Signal Description 2690 ======================================================================== 2692 | Router initiates discovery, starts 2693 | a timer, send Peer Discovery 2694 |-------Peer Discovery---->|| signal. 2696 ~ ~ ~ ~ ~ ~ ~ Router discovery timer expires 2697 without receiving Peer Offer. 2699 | Router sends another Peer 2700 |-------Peer Discovery---------->| Discovery signal. 2701 | 2702 | Modem receives Peer Discovery 2703 | signal. 2704 | 2705 | Modem sends Peer Offer with 2706 |<--------Peer Offer-------------| Connection Point information. 2707 : 2708 : Router MAY cancel discovery timer 2709 : and stop sending Peer Discovery 2710 : signals. 2712 Appendix B. Peer Level Message Flows 2714 B.1. Session Initialization 2715 Router Modem Signal Description 2716 ======================================================================== 2718 | Router connects to discovered or 2719 | pre-configured Modem Connection 2720 |---------TCP connect----------> Point. 2721 | 2722 | Router sends Session Initialization 2723 |----Session Initialization----->| message. 2724 | 2725 | Modem receives Session Initialization 2726 | message. 2727 | 2728 | Modem sends Session Initialization 2729 |<--Session Initialization Resp.-| Response, with Success status data item. 2730 | | 2731 |<<============================>>| Session established. Heartbeats 2732 : : begin. 2734 B.2. Session Initialization - Refused 2736 Router Modem Signal Description 2737 ======================================================================== 2739 | Router connects to discovered or 2740 | pre-configured Modem Connection 2741 |---------TCP connect----------> Point. 2742 | 2743 | Router sends Session Initialization 2744 |-----Session Initialization---->| message. 2745 | 2746 | Modem receives Session Initialization 2747 | message, and will not support the 2748 | advertised extensions. 2749 | 2750 | Modem sends Session Initialization 2751 | Response, with 'Request Denied' status 2752 |<-Session Initialization Resp.--| data item. 2753 | 2754 | 2755 | Router receives negative Session 2756 | Initialization Response, closes 2757 ||---------TCP close------------|| TCP connection. 2759 B.3. Router Changes IP Addresses 2761 Router Modem Signal Description 2762 ======================================================================== 2764 | Router sends Session Update message to 2765 |-------Session Update---------->| announce change of IP address 2766 | 2767 | Modem receives Session Update message 2768 | and updates internal state. 2769 | 2770 |<----Session Update Response----| Modem sends Session Update Response. 2772 B.4. Modem Changes Session-wide Metrics 2774 Router Modem Signal Description 2775 ======================================================================== 2777 | Modem sends Session Update message to 2778 | announce change of modem-wide 2779 |<--------Session Update---------| metrics 2780 | 2781 | Router receives Session Update message 2782 | and updates internal state. 2783 | 2784 |----Session Update Response---->| Router sends Session Update Response. 2786 B.5. Router Terminates Session 2788 Router Modem Signal Description 2789 ======================================================================== 2791 | Router sends Session Termination 2792 |------Session Termination------>| message with Status data item. 2793 | | 2794 |-------TCP shutdown (send)---> | Router stops sending messages. 2795 | 2796 | Modem receives Session Termination, 2797 | stops counting received heartbeats 2798 | and stops sending heartbeats. 2799 | 2800 | Modem sends Session Termination Response 2801 |<---Session Termination Resp.---| with Status 'Success'. 2802 | 2803 | Modem stops sending messages. 2804 | 2805 ||---------TCP close------------|| Session terminated. 2807 B.6. Modem Terminates Session 2809 Router Modem Signal Description 2810 ======================================================================== 2812 | Modem sends Session Termination 2813 |<----Session Termination--------| message with Status data item. 2814 | 2815 | Modem stops sending messages. 2816 | 2817 | Router receives Session Termination, 2818 | stops counting received heartbeats 2819 | and stops sending heartbeats. 2820 | 2821 | Router sends Session Termination Response 2822 |---Session Termination Resp.--->| with Status 'Success'. 2823 | 2824 | Router stops sending messages. 2825 | 2826 ||---------TCP close------------|| Session terminated. 2828 B.7. Session Heartbeats 2829 Router Modem Signal Description 2830 ======================================================================== 2832 |----------Heartbeat------------>| Router sends heartbeat message 2833 | 2834 | Modem resets heartbeats missed 2835 | counter. 2837 ~ ~ ~ ~ ~ ~ ~ 2839 |---------[Any message]--------->| When the Modem receives any message 2840 | from the Router. 2841 | 2842 | Modem resets heartbeats missed 2843 | counter. 2845 ~ ~ ~ ~ ~ ~ ~ 2847 |<---------Heartbeat-------------| Modem sends heartbeat message 2848 | 2849 | Router resets heartbeats missed 2850 | counter. 2852 ~ ~ ~ ~ ~ ~ ~ 2854 |<--------[Any message]----------| When the Router receives any 2855 | message from the Modem. 2856 | 2857 | Modem resets heartbeats missed 2858 | counter. 2860 B.8. Router Detects a Heartbeat timeout 2862 Router Modem Signal Description 2863 ======================================================================== 2865 ||<----------------------| Router misses a heartbeat 2867 | ||<----------------------| Router misses too many heartbeats 2868 | 2869 | 2870 |------Session Termination------>| Router sends Session Termination 2871 | message with 'Timeout' Status 2872 | data item. 2873 : 2874 : Termination proceeds as above. 2876 B.9. Modem Detects a Heartbeat timeout 2878 Router Modem Signal Description 2879 ======================================================================== 2881 |---------------------->|| Modem misses a heartbeat 2883 |---------------------->|| | Modem misses too many heartbeats 2884 | 2885 | 2886 |<-----Session Termination-------| Modem sends Session Termination 2887 | message with 'Timeout' Status 2888 | data item. 2889 : 2890 : Termination proceeds as above. 2892 Appendix C. Destination Specific Signal Flows 2894 C.1. Common Destination Signaling 2896 Router Modem Signal Description 2897 ======================================================================== 2899 | Modem detects a new logical 2900 | destination is reachable, and 2901 |<-------Destination Up----------| sends Destination Up message. 2902 | 2903 |------Destination Up Resp.----->| Router sends Destination Up Response. 2905 ~ ~ ~ ~ ~ ~ ~ 2906 | Modem detects change in logical 2907 | destination metrics, and sends 2908 |<-------Destination Update------| Destination Update message. 2910 ~ ~ ~ ~ ~ ~ ~ 2911 | Modem detects change in logical 2912 | destination metrics, and sends 2913 |<-------Destination Update------| Destination Update message. 2915 ~ ~ ~ ~ ~ ~ ~ 2916 | Modem detects logical destination 2917 | is no longer reachable, and sends 2918 |<-------Destination Down--------| Destination Down message. 2919 | 2920 | Router receives Destination Down, 2921 | updates internal state, and sends 2922 |------Destination Down Resp.--->| Destination Down Response message. 2924 C.2. Multicast Destination Signaling 2926 Router Modem Signal Description 2927 ======================================================================== 2929 | Router detects a new multicast 2930 | destination is in use, and sends 2931 |--------Destination Up--------->| Destination Up message. 2932 | 2933 | Modem updates internal state to 2934 | monitor multicast destination, and 2935 |<-----Destination Up Resp.------| sends Destination Up Response. 2937 ~ ~ ~ ~ ~ ~ ~ 2938 | Modem detects change in multicast 2939 | destination metrics, and sends 2940 |<-------Destination Update------| Destination Update message. 2942 ~ ~ ~ ~ ~ ~ ~ 2943 | Modem detects change in multicast 2944 | destination metrics, and sends 2945 |<-------Destination Update------| Destination Update message. 2947 ~ ~ ~ ~ ~ ~ ~ 2948 | Router detects multicast 2949 | destination is no longer in use, 2950 |--------Destination Down------->| and sends Destination Down message. 2951 | 2952 | Modem receives Destination Down, 2953 | updates internal state, and sends 2954 |<-----Destination Down Resp.----| Destination Down Response message. 2956 C.3. Link Characteristics Request 2957 Router Modem Signal Description 2958 ======================================================================== 2960 Destination has already been 2961 ~ ~ ~ ~ ~ ~ ~ announced by either peer. 2963 | Router requires different 2964 | Characteristics for the 2965 | destination, and sends Link 2966 |--Link Characteristics Request->| Characteristics Request message. 2967 | 2968 | Modem attempts to adjust link 2969 | status to meet the received 2970 | request, and sends a Link 2971 | Characteristics Response 2972 |<---Link Characteristics Resp.--| message with the new values. 2974 Authors' Addresses 2976 Stan Ratliff 2977 VT iDirect 2978 13861 Sunrise Valley Drive, Suite 300 2979 Herndon, VA 20171 2980 USA 2982 Email: sratliff@idirect.net 2984 Bo Berry 2986 Shawn Jury 2987 Cisco Systems 2988 170 West Tasman Drive 2989 San Jose, CA 95134 2990 USA 2992 Email: sjury@cisco.com 2994 Darryl Satterwhite 2995 Broadcom 2997 Email: dsatterw@broadcom.com 2998 Rick Taylor 2999 Airbus Defence & Space 3000 Quadrant House 3001 Celtic Springs 3002 Coedkernew 3003 Newport NP10 8FZ 3004 UK 3006 Email: rick.taylor@airbus.com