idnits 2.17.1 draft-ietf-manet-dlep-08.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 : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 273 has weird spacing: '... Shared o ...' == Line 274 has weird spacing: '... Medium o...' -- The document date (February 27, 2015) is 3336 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) ** Downref: Normative reference to an Informational RFC: RFC 5578 -- Obsolete informational reference (is this intentional?): RFC 5246 (Obsoleted by RFC 8446) Summary: 1 error (**), 0 flaws (~~), 3 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: August 31, 2015 6 S. Jury 7 Cisco Systems 8 D. Satterwhite 9 Broadcom 10 R. Taylor 11 Airbus Defence & Space 12 February 27, 2015 14 Dynamic Link Exchange Protocol (DLEP) 15 draft-ietf-manet-dlep-08 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 forwarding 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 August 31, 2015. 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. Requirements . . . . . . . . . . . . . . . . . . . . . . 8 65 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 8 66 3. Core Features and Optional Extensions . . . . . . . . . . . . 10 67 3.1. Negotiation of Optional Extensions . . . . . . . . . . . 10 68 3.2. Protocol Extensions . . . . . . . . . . . . . . . . . . . 10 69 3.3. Experimental Signals and Data Items . . . . . . . . . . . 11 70 4. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 4.1. Mandatory Metrics . . . . . . . . . . . . . . . . . . . . 12 72 5. Normal Session Flow . . . . . . . . . . . . . . . . . . . . . 12 73 5.1. DLEP Router session flow - Discovery case . . . . . . . . 13 74 5.2. DLEP Router session flow - Configured case . . . . . . . 13 75 5.3. DLEP Modem session flow . . . . . . . . . . . . . . . . . 14 76 5.4. Common Session Flow . . . . . . . . . . . . . . . . . . . 14 77 6. DLEP Message Processing . . . . . . . . . . . . . . . . . . . 15 78 6.1. DLEP Signal Header . . . . . . . . . . . . . . . . . . . 16 79 6.2. DLEP Generic Data Item . . . . . . . . . . . . . . . . . 16 80 7. DLEP Signals . . . . . . . . . . . . . . . . . . . . . . . . 17 81 7.1. Peer Discovery Signal . . . . . . . . . . . . . . . . . . 17 82 7.2. Peer Offer Signal . . . . . . . . . . . . . . . . . . . . 18 83 7.3. Peer Initialization Signal . . . . . . . . . . . . . . . 19 84 7.4. Peer Initialization ACK Signal . . . . . . . . . . . . . 20 85 7.5. Peer Update Signal . . . . . . . . . . . . . . . . . . . 21 86 7.6. Peer Update ACK Signal . . . . . . . . . . . . . . . . . 22 87 7.7. Peer Termination Signal . . . . . . . . . . . . . . . . . 23 88 7.8. Peer Termination ACK Signal . . . . . . . . . . . . . . . 23 89 7.9. Destination Up Signal . . . . . . . . . . . . . . . . . . 24 90 7.10. Destination Up ACK Signal . . . . . . . . . . . . . . . . 25 91 7.11. Destination Down Signal . . . . . . . . . . . . . . . . . 26 92 7.12. Destination Down ACK Signal . . . . . . . . . . . . . . . 26 93 7.13. Destination Update Signal . . . . . . . . . . . . . . . . 26 94 7.14. Heartbeat Signal . . . . . . . . . . . . . . . . . . . . 28 95 7.15. Link Characteristics Request Signal . . . . . . . . . . . 28 96 7.16. Link Characteristics ACK Signal . . . . . . . . . . . . . 29 97 8. DLEP Data Items . . . . . . . . . . . . . . . . . . . . . . . 30 98 8.1. DLEP Version . . . . . . . . . . . . . . . . . . . . . . 31 99 8.2. Status . . . . . . . . . . . . . . . . . . . . . . . . . 32 100 8.3. DLEP Port . . . . . . . . . . . . . . . . . . . . . . . . 33 101 8.4. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 33 102 8.5. Heartbeat Interval . . . . . . . . . . . . . . . . . . . 34 103 8.6. Extensions Supported . . . . . . . . . . . . . . . . . . 35 104 8.7. Experimental Definition . . . . . . . . . . . . . . . . . 35 105 8.8. MAC Address . . . . . . . . . . . . . . . . . . . . . . . 36 106 8.9. IPv4 Address . . . . . . . . . . . . . . . . . . . . . . 37 107 8.10. IPv6 Address . . . . . . . . . . . . . . . . . . . . . . 37 108 8.11. IPv4 Attached Subnet . . . . . . . . . . . . . . . . . . 38 109 8.12. IPv6 Attached Subnet . . . . . . . . . . . . . . . . . . 39 110 8.13. Maximum Data Rate (Receive) . . . . . . . . . . . . . . . 39 111 8.14. Maximum Data Rate (Transmit) . . . . . . . . . . . . . . 40 112 8.15. Current Data Rate (Receive) . . . . . . . . . . . . . . . 41 113 8.16. Current Data Rate (Transmit) . . . . . . . . . . . . . . 41 114 8.17. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 42 115 8.18. Resources (Receive) . . . . . . . . . . . . . . . . . . . 43 116 8.19. Resources (Transmit) . . . . . . . . . . . . . . . . . . 43 117 8.20. Relative Link Quality (Receive) . . . . . . . . . . . . . 44 118 8.21. Relative Link Quality (Transmit) . . . . . . . . . . . . 45 119 8.22. Link Characteristics ACK Timer . . . . . . . . . . . . . 45 120 9. Credit-Windowing . . . . . . . . . . . . . . . . . . . . . . 46 121 9.1. Credit-Windowing Signals . . . . . . . . . . . . . . . . 46 122 9.1.1. Destination Up Signal . . . . . . . . . . . . . . . . 46 123 9.1.2. Destination Up ACK Signal . . . . . . . . . . . . . . 47 124 9.1.3. Destination Update Signal . . . . . . . . . . . . . . 47 125 9.2. Credit-Windowing Data Items . . . . . . . . . . . . . . . 47 126 9.2.1. Credit Window Status . . . . . . . . . . . . . . . . 47 127 9.2.2. Credit Grant . . . . . . . . . . . . . . . . . . . . 48 128 9.2.3. Credit Request . . . . . . . . . . . . . . . . . . . 49 129 10. Security Considerations . . . . . . . . . . . . . . . . . . . 50 130 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 131 11.1. Registrations . . . . . . . . . . . . . . . . . . . . . 50 132 11.2. Expert Review: Evaluation Guidelines . . . . . . . . . . 51 133 11.3. Signal Type Registration . . . . . . . . . . . . . . . . 51 134 11.4. DLEP Data Item Registrations . . . . . . . . . . . . . . 52 135 11.5. DLEP Status Code Registrations . . . . . . . . . . . . . 53 136 11.6. DLEP Extensions Registrations . . . . . . . . . . . . . 53 137 11.7. DLEP Well-known Port . . . . . . . . . . . . . . . . . . 54 138 11.8. DLEP Multicast Address . . . . . . . . . . . . . . . . . 54 139 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 54 140 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 54 141 13.1. Normative References . . . . . . . . . . . . . . . . . . 54 142 13.2. Informative References . . . . . . . . . . . . . . . . . 54 143 Appendix A. Peer Level Signal Flows . . . . . . . . . . . . . . 54 144 A.1. Router Device Restarts Discovery . . . . . . . . . . . . 54 145 A.2. Router Device Detects Peer Offer Timeout . . . . . . . . 55 146 A.3. Router Peer Offer Lost . . . . . . . . . . . . . . . . . 55 147 A.4. Discovery Success . . . . . . . . . . . . . . . . . . . . 56 148 A.5. Router Detects a Heartbeat timeout . . . . . . . . . . . 57 149 A.6. Modem Detects a Heartbeat timeout . . . . . . . . . . . . 57 150 A.7. Peer Terminate (from Modem) Lost . . . . . . . . . . . . 58 151 A.8. Peer Terminate (from Router) Lost . . . . . . . . . . . . 58 152 Appendix B. Destination Specific Signal Flows . . . . . . . . . 59 153 B.1. Modem Destination Up Lost . . . . . . . . . . . . . . . . 59 154 B.2. Router Detects Duplicate Destination Ups . . . . . . . . 59 155 B.3. Destination Up, No Layer 3 Addresses . . . . . . . . . . 60 156 B.4. Destination Up with IPv4, No IPv6 . . . . . . . . . . . . 60 157 B.5. Destination Up with IPv4 and IPv6 . . . . . . . . . . . . 61 158 B.6. Destination Session Success . . . . . . . . . . . . . . . 61 159 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 62 161 1. Introduction 163 There exist today a collection of modem devices that control links of 164 variable datarate and quality. Examples of these types of links 165 include line-of-sight (LOS) terrestrial radios, satellite terminals, 166 and cable/DSL modems. Fluctuations in speed and quality of these 167 links can occur due to configuration (in the case of cable/DSL 168 modems), or on a moment-to-moment basis, due to physical phenomena 169 like multipath interference, obstructions, rain fade, etc. It is 170 also quite possible that link quality and datarate varies with 171 respect to individual destinations on a link, and with the type of 172 traffic being sent. As an example, consider the case of an 802.11g 173 access point, serving 2 associated laptop computers. In this 174 environment, the answer to the question "What is the datarate on the 175 802.11g link?" is "It depends on which associated laptop we're 176 talking about, and on what kind of traffic is being sent." While the 177 first laptop, being physically close to the access point, may have a 178 datarate of 54Mbps for unicast traffic, the other laptop, being 179 relatively far away, or obstructed by some object, can simultaneously 180 have a datarate of only 32Mbps for unicast. However, for multicast 181 traffic sent from the access point, all traffic is sent at the base 182 transmission rate (which is configurable, but depending on the model 183 of the access point, is usually 24Mbps or less). 185 In addition to utilizing variable datarate links, mobile networks are 186 challenged by the notion that link connectivity will come and go over 187 time, without an effect on a router's interface state (Up or Down). 188 Effectively utilizing a relatively short-lived connection is 189 problematic in IP routed networks, as routing protocols tend to rely 190 on interface state and independent timers at OSI Layer 3 to maintain 191 network convergence (e.g., HELLO messages and/or recognition of DEAD 192 routing adjacencies). These dynamic connections can be better 193 utilized with an event-driven paradigm, where acquisition of a new 194 neighbor (or loss of an existing one) is signaled, as opposed to a 195 paradigm driven by timers and/or interface state. 197 Another complicating factor for mobile networks are the different 198 methods of physically connecting the modem devices to the router. 199 Modems can be deployed as an interface card in a router's chassis, or 200 as a standalone device connected to the router via Ethernet or serial 201 link. In the case of Ethernet or serial attachment, with existing 202 protocols and techniques, routing software cannot be aware of 203 convergence events occurring on the radio link (e.g., acquisition or 204 loss of a potential routing neighbor), nor can the router be aware of 205 the actual capacity of the link. This lack of awareness, along with 206 the variability in datarate, leads to a situation where finding the 207 (current) best route through the network to a given destination is 208 difficult to establish and properly maintain. This is especially 209 true of demand-based access schemes such as Demand Assigned Multiple 210 Access (DAMA) implementations used on some satellite systems. With a 211 DAMA-based system, additional datarate may be available, but will not 212 be used unless the network devices emit traffic at a rate higher than 213 the currently established rate. Increasing the traffic rate does not 214 guarantee additional datarate will be allocated; rather, it may 215 result in data loss and additional retransmissions on the link. 217 Addressing the challenges listed above, the authors have developed 218 the Data Link Exchange Protocol, or DLEP. The DLEP protocol runs 219 between a router and its attached modem devices, allowing the modem 220 to communicate link characteristics as they change, and convergence 221 events (acquisition and loss of potential routing destinations). The 222 following diagrams are used to illustrate the scope of DLEP packets. 224 |-------Local Node-------| |-------Remote Node------| 225 | | | | 226 +--------+ +-------+ +-------+ +--------+ 227 | Router |=======| Modem |{~~~~~~~~}| Modem |=======| Router | 228 | | | Device| | Device| | | 229 +--------+ +-------+ +-------+ +--------+ 230 | | | Link | | | 231 |-DLEP--| | Protocol | |-DLEP--| 232 | | | (e.g. | | | 233 | | | 802.11) | | | 235 Figure 1: DLEP Network 237 In Figure 1, when the local modem detects the presence of a remote 238 node, it (the local modem) sends a signal to its router via the DLEP 239 protocol. Upon receipt of the signal, the local router may take 240 whatever action it deems appropriate, such as initiating discovery 241 protocols, and/or issuing HELLO messages to converge the network. On 242 a continuing, as-needed basis, the modem devices utilize DLEP to 243 report any characteristics of the link (datarate, latency, etc) that 244 have changed. DLEP is independent of the link type and topology 245 supported by the modem. Note that the DLEP protocol is specified to 246 run only on the local link between router and modem. Some over the 247 air signaling may be necessary between the local and remote modem in 248 order to provide some parameters in DLEP signals between the local 249 modem and local router, but DLEP does not specify how such over the 250 air signaling is carried out. Over the air signaling is purely a 251 matter for the modem implementer. 253 Figure 2 shows how DLEP can support a configuration where routers are 254 connected with different link types. In this example, Modem A 255 implements a point-to-point link, and Modem B is connected via a 256 shared medium. In both cases, the DLEP protocol is used to report 257 the characteristics of the link (datarate, latency, etc.) to routers. 258 The modem is also able to use the DLEP session to notify the router 259 when the remote node is lost, shortening the time required to re- 260 converge the network. 262 +--------+ +--------+ 263 +----+ Modem A| | Modem A+---+ 264 | | Device | <===== // ======> | Device | | 265 | +--------+ P-2-P Link +--------+ | 266 +---+----+ +---+----+ 267 | Router | | Router | 268 | | | | 269 +---+----+ +---+----+ 270 | +--------+ +--------+ | 271 +-----+ Modem B| | Modem B| | 272 | Device | o o o o o o o o | Device +--+ 273 +--------+ o Shared o +--------+ 274 o Medium o 275 o o 276 o o 277 o o 278 o 279 +--------+ 280 | Modem B| 281 | Device | 282 +---+----+ 283 | 284 | 285 +---+----+ 286 | Router | 287 | | 288 +--------+ 290 Figure 2: DLEP Network with Multiple Modem Devices 292 DLEP defines a set of signals used by modems and their attached 293 routers. The signals are used to communicate events that occur on 294 the physical link(s) managed by the modem: for example, a remote node 295 entering or leaving the network, or that the link has changed. 296 Associated with these signals are a set of data items - information 297 that describes the remote node (e.g., address information), and/or 298 the characteristics of the link to the remote node. 300 The protocol is defined as a collection of type-length-value (TLV) 301 based formats, specifying the signals that are exchanged between a 302 router and a modem, and the data items associated with the signal. 303 This document specifies transport of DLEP signals and data items via 304 the TCP transport, with a UDP-based discovery mechanism. Other 305 transports for the protocol are possible, but are outside the scope 306 of this document. 308 DLEP uses a session-oriented paradigm between the modem device and 309 its associated router. If multiple modem devices are attached to a 310 router (as in Figure 2), a separate DLEP session MUST exist for each 311 modem. If a modem device supports multiple connections to a router 312 (via multiple logical or physical interfaces), or supports 313 connections to multiple routers, a separate DLEP session MUST exist 314 for each connection. This router/modem session provides a carrier 315 for information exchange concerning 'destinations' that are available 316 via the modem device. A 'destination' can be either physical (as in 317 the case of a specific far-end router), or a logical destination (as 318 in a Multicast group). As such, all of the destination-level 319 exchanges in DLEP can be envisioned as building an information base 320 concerning the remote nodes, and the link characteristics to those 321 nodes. 323 Any DLEP signal that is NOT understood by a receiver MUST result in 324 an error indication being sent to the originator, and also MUST 325 result in termination of the session between the DLEP peers. Any 326 data item that is NOT understood by a receiver MUST be ignored. 328 Multicast traffic destined for the variable-quality network (the 329 network accessed via the DLEP modem) is handled in IP networks by 330 deriving a Layer 2 MAC address based on the Layer 3 address. 331 Leveraging on this scheme, Multicast traffic is supported in DLEP 332 simply by treating the derived MAC address as any other 'destination' 333 (albeit a logical one) in the network. To support these logical 334 destinations, one of the DLEP participants (typically, the router) 335 informs the other as to the existence of the logical neighbor. The 336 modem, once it is aware of the existence of this logical neighbor, 337 reports link characteristics just as it would for any other 338 destination in the network. The specific algorithms a modem would 339 use to report metrics on multicast (or logical) destinations is 340 outside the scope of this specification, and is left to specific 341 implementations to decide. 343 1.1. Requirements 345 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 346 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 347 document are to be interpreted as described in BCP 14, RFC 2119 348 [RFC2119]. 350 2. Assumptions 352 Routers and modems that exist as part of the same node (e.g., that 353 are locally connected) can utilize a discovery technique to locate 354 each other, thus avoiding a-priori configuration. The router is 355 responsible for initializing the discovery process, using the Peer 356 Discovery signal (Section 7.1). 358 DLEP utilizes a session-oriented paradigm. A router and modem form a 359 session by completing the discovery process. This router-modem 360 session persists unless or until it either (1) times out, based on 361 the timeout values supplied, or (2) is explicitly torn down by one of 362 the participants. Note that while use of timers in DLEP is OPTIONAL, 363 it is strongly recommended that implementations choose to run with 364 timers enabled. 366 DLEP assumes that the MAC address for delivering data traffic is the 367 MAC specified in the Destination Up signal (Section 7.9). No 368 manipulation or or substitution is performed; the MAC address 369 supplied in Destination Up is used as the OSI Layer 2 Destination MAC 370 address. DLEP also assumes that MAC addresses MUST be unique within 371 the context of a router-modem session. 373 DLEP utilizes UDP multicast for single-hop discovery, and TCP for 374 transport of the control signals. Therefore, DLEP assumes that the 375 modem and router have topologically consistent IP addresses assigned. 376 It is recommended that DLEP implementations utilize IPv6 link-local 377 addresses to reduce the administrative burden of address assignment. 379 This document refers to a remote node as a 'Destination'. 380 Destinations can be identified by either the router or the modem, and 381 represent a specific destination (e.g., an address) that exists on 382 the link(s) managed by the modem. A destination MUST contain a MAC 383 address, it MAY optionally include a Layer 3 address (or addresses). 384 Note that since a destination is a MAC address, the MAC could 385 reference a logical destination, as in a derived multicast MAC 386 address, as well as to a physical device. As destinations are 387 discovered, DLEP routers and modems build an information base on 388 destinations accessible via the modem. Changes in link 389 characteristics are then reported as being 'modem-wide' (effecting 390 ALL destinations accessed via the modem, reported via the Peer Update 391 signal, Section 7.5) or reported for a specific neighbor (via the 392 Destination Update signal, Section 7.13). 394 The DLEP signals concerning destinations thus become the way for 395 routers and modems to maintain, and notify each other about, an 396 information base representing the physical and logical (e.g., 397 multicast) destinations accessible via the modem device. The 398 information base would contain addressing information (i.e., MAC 399 address, and OPTIONALLY, Layer 3 addresses), link characteristics 400 (metrics), and OPTIONALLY, flow control information (credits). 402 DLEP assumes that security on the session (e.g., authentication of 403 session partners, encryption of traffic, or both) is dealt with by 404 the underlying transport mechanism (e.g., by using a transport such 405 as TLS [RFC5246]). 407 This document specifies an implementation of the DLEP signals and 408 data items running over the TCP transport. It is assumed that DLEP 409 running over other transport mechanisms would be documented 410 separately. 412 3. Core Features and Optional Extensions 414 DLEP has a core set of signals and data items that MUST be processed 415 without error by an implementation in order to guarantee 416 interoperability and therefore make the implementation DLEP 417 compliant. This document defines the core set of signals and data 418 items, listing them as 'mandatory'. It should be noted that some 419 core signals and data items might not be used during the lifetime of 420 a single DLEP session, but a compliant implementation MUST support 421 them. 423 While this document represents the best efforts of the co-authors, 424 and the working group, to be functionally complete, it is recognized 425 that extensions to DLEP will in all likelihood be necessary as more 426 link types are utilized. To support future extension of DLEP, this 427 document describes an extension negotiation capability to be used 428 during session initialization via the Extensions Supported data item, 429 documented in Section 8.6 of this document. 431 All extensions are considered OPTIONAL. Only the DLEP functionality 432 listed as 'mandatory' is required by implementation in order to be 433 DLEP compliant. 435 This specification defines one extension, Credit processing, exposed 436 via the Extensions Supported mechanism that implementations MAY chose 437 to implement, or to omit. 439 3.1. Negotiation of Optional Extensions 441 Optional extensions supported by an implementation MUST be declared 442 to potential DLEP peers using the Extensions Supported data item 443 (Section 8.6) during the session initialization sequence. Once both 444 peers have exchanged initialization signals, an implementation MUST 445 NOT emit any signal or data item associated with an optional 446 extension that was not specified in the received initialization 447 signal from its peer. 449 3.2. Protocol Extensions 451 If/when protocol extensions are required, they should be standardized 452 either as an update to this document, or as an additional stand-alone 453 specification. The requests for IANA-controlled registries in this 454 document contain sufficient reserved space, both in terms of DLEP 455 signals and DLEP data items, to accomodate future extensions to the 456 protocol and the data transferred. 458 3.3. Experimental Signals and Data Items 460 This document requests numbering space in both the DLEP signal and 461 data item registries for experimental items. The intent is to allow 462 for experimentation with new signals and/or data items, while still 463 retaining the documented DLEP behavior. If a given experiment proves 464 successful, it SHOULD be documented as an update to this document, or 465 as a stand-alone specification. 467 Use of the experimental signals or data items MUST be announced by 468 inclusion of an Experimental Definition data item (Section 8.7) with 469 a value agreed upon (a-priori) between the participating peers. The 470 exact mechanism for a-priori communication of the experimental 471 definition formats is beyond the scope of this document. 473 Multiple Experimental Definition data items MAY appear in the Peer 474 Initialization/Peer Initialization ACK sequence. However, use of 475 multiple experiments in a single peer session could lead to 476 interoperability issues or unexpected results (e.g., redefinition of 477 experimental signals and/or data items), and is therefore 478 discouraged. It is left to implementations to determine the correct 479 processing path (e.g., a decision on whether to terminate the peer 480 session, or to establish a precedence of the conflicting definitions) 481 if such conflicts arise. 483 4. Metrics 485 DLEP includes the ability for the router and modem to communicate 486 metrics that reflect the characteristics (e.g., datarate, latency) of 487 the variable-quality link in use. DLEP does NOT specify how a given 488 metric value is to be calculated, rather, the protocol assumes that 489 metrics have been calculated with a 'best effort', incorporating all 490 pertinent data that is available to the modem device. 492 As mentioned in the introduction section of this document, metrics 493 have to be used within a context - for example, metrics to a unicast 494 address in the network. DLEP allows for metrics to be sent within 495 two contexts - metrics for a specific destination within the network 496 (e.g., a specific router), and 'modem-wide' (those that apply to all 497 destinations accessed via the modem). Metrics can be further 498 subdivided into transmit and receive metrics. Metrics supplied on 499 DLEP Peer signals are, by definition, modem-wide; metrics supplied on 500 Destination signals are, by definition, used for the specific 501 neighbor only. 503 DLEP modem implementations MUST announce all supported metric items, 504 and provide default values for those metrics, in the Peer 505 Initialization signal (Section 7.3). In order to introduce a new 506 metric type, DLEP modem implementations MUST terminate the session 507 with the router (via the Peer Terminate signal, Section 7.7), and re- 508 establish the session. 510 It is left to implementations to choose sensible default values based 511 on their specific characteristics. Modems having static (non- 512 changing) link metric characteristics MAY report metrics only once 513 for a given neighbor (or once on a modem-wide basis, if all 514 connections via the modem are of this static nature). 516 The approach of allowing for different contexts for metric data 517 increases both the flexibility and the complexity of using metric 518 data. This document details the mechanism whereby the data is 519 transmitted, however, the specific algorithms (precedence, etc) for 520 utilizing the dual-context metrics is out of scope and not addressed 521 by this document. 523 4.1. Mandatory Metrics 525 As mentioned above, DLEP modem implementations MUST announce all 526 supported metric items during session initialization. However, an 527 implementation MUST include the following list of metrics: 529 o Maximum Data Rate (Receive) (Section 8.13) 531 o Maximum Data Rate (Transmit) (Section 8.14) 533 o Current Data Rate (Receive) (Section 8.15) 535 o Current Data Rate (Transmit) (Section 8.16) 537 o Latency (Section 8.17) 539 5. Normal Session Flow 541 Normal session flow for a DLEP router has two sub-cases, depending on 542 whether the implementation supports the discovery process. Modem 543 implementations MUST support the Discovery case; router 544 implementations MAY support discovery, or rely on a-priori 545 configuration to define the address(es) of attached modems. 547 5.1. DLEP Router session flow - Discovery case 549 If the DLEP router implementation is utilizing the optional discovery 550 mechanism, then the implementation will initialize a UDP socket, 551 binding it to an arbitrary port. This UDP socket is used to send the 552 Peer Discovery signal (Section 7.1) to the DLEP link-local multicast 553 address and port (TBD). The implementation then waits on receipt of 554 a Peer Offer signal (Section 7.2), which MUST contain the unicast 555 address and port for TCP-based communication with a DLEP modem. The 556 Peer Offer signal MAY contain multiple address/port combinations. If 557 more than one address/port combination is in the Peer Offer, the DLEP 558 router implementation SHOULD consider the list to be in priority 559 sequence, with the 'most desired' address/port combination listed 560 first. However, router implementations MAY use their own heuristics 561 to determine the best address/port combination. At this point, the 562 router implementation MAY either destroy the UDP socket, or continue 563 to issue Peer Discovery signals to the link-local address/port 564 combination. In either case, the TCP session initialization occurs 565 as in the configured case. 567 5.2. DLEP Router session flow - Configured case 569 When a DLEP router implementation has the address and port 570 information for a TCP connection to a modem (obtained either via 571 configuration or via the discovery process described above), the 572 router will initialize and bind a TCP socket. This socket is used to 573 connect to the DLEP modem software. After a successful TCP connect, 574 the modem implementation MUST issue a Peer Initialization signal 575 (Section 7.3) to the DLEP router. The Peer Initialization signal 576 MUST contain data items for ALL supported metrics from this modem, 577 along with the default values of those metrics. After sending the 578 Peer Initialization, the modem implementation MUST wait for receipt 579 of a Peer Initialization ACK signal (Section 7.4) from the router. 580 Receipt of the Peer Initialization ACK signal indicates that the 581 router has received and processed the Peer Initialization, and the 582 session MUST transition to the 'in session' state. At this point, 583 signals regarding destinations in the network, and/or Peer Update 584 signals (Section 7.5), can flow on the DLEP session between modem and 585 router. The 'in session' state is maintained until one of the 586 following conditions occur: 588 o The session is explicitly terminated (using Peer Termination), or 590 o The session times out, based on supplied timeout values. 592 5.3. DLEP Modem session flow 594 DLEP modem implementations MUST support the discovery mechanism. 595 Therefore, the normal flow is as follows: 597 The implementation will initialize a UDP socket, binding that socket 598 to the DLEP link-local multicast address (TBD) and the DLEP well- 599 known port number (also TBD). The implementation will then 600 initialize a TCP socket, on a unicast address and port. This socket 601 is used to listen for incoming TCP connection requests. 603 When the modem implementation receives a Peer Discovery signal 604 (Section 7.1) on the UDP socket, it responds by issuing a Peer Offer 605 signal (Section 7.2) to the sender of the Peer Discovery signal. The 606 Peer Offer signal MUST contain the unicast address and port of the 607 TCP listen socket, described above. A DLEP modem implementation MAY 608 respond with ALL address/port combinations that have an active TCP 609 listen posted. If multiple address/port combinations are listed, the 610 receiver of the Peer Offer signal MAY connect on any available 611 address/port pair. Anything other than Peer Discovery signals 612 received on the UDP socket MUST be silently dropped. 614 When the DLEP modem implementation accepts a connection via TCP, it 615 MUST send a Peer Initialization signal (Section 7.3). The Peer 616 Initialization signal MUST contain metric data items for ALL 617 supported metrics. If an additional metric is to be introduced, the 618 DLEP session between router and modem MUST be terminated and 619 restarted, and the new metric described in a Peer Initialization 620 signal. 622 5.4. Common Session Flow 624 In order to maintain the session between router and modem, periodic 625 Heartbeat signals (Section 7.14) MAY be exchanged. These signals are 626 intended to keep the session alive, and to verify bidirectional 627 connectivity between the two participants. DLEP also provides a Peer 628 Update signal (Section 7.5), intended to communicate some change in 629 status (e.g., a change of layer 3 address parameters, or a modem-wide 630 link change). 632 In addition to the local (Peer level) signals above, the participants 633 will transmit DLEP signals concerning destinations in the network. 634 These signals trigger creation/maintenance/deletion of destinations 635 in the information base of the recipient. For example, a modem will 636 inform its attached router of the presence of a new destination via 637 the Destination Up signal (Section 7.9). Receipt of a Destination Up 638 causes the router to allocate the necessary resources, creating an 639 entry in the information base with the specifics (i.e., MAC Address, 640 Latency, Data Rate, etc) of the neighbor. The loss of a destination 641 is communicated via the Destination Down signal (Section 7.11), and 642 changes in status to the destination (e.g., varying link quality, or 643 addressing changes) are communicated via the Destination Update 644 signal (Section 7.13). The information on a given neighbor will 645 persist in the router's information base until (1) a Destination Down 646 signal is received, indicating that the modem has lost contact with 647 the remote node, or (2) the router/modem session terminates, 648 indicating that the router has lost contact with its own local modem. 650 Metrics can be expressed within the context of a specific neighbor 651 via the Destination Update signal, or on a modem-wide basis via the 652 Peer Update signal. In cases where metrics are provided on the 653 router/modem session, the receiver MUST propagate the metrics to all 654 destinations in its information base that are accessed via the 655 originator. A DLEP participant MAY send metrics both in a router/ 656 modem session context (via the Peer Update signal) and a specific 657 neighbor context (via Destination Update) at any time. The 658 heuristics for applying received metrics is left to implementations. 660 In addition to receiving metrics about the link, DLEP provides a 661 signal allowing a router to request a different datarate, or latency, 662 from the modem. This signal is referred to as the Link 663 Characteristics Request signal (Section 7.15), and gives the router 664 the ability to deal with requisite increases (or decreases) of 665 allocated datarate/latency in demand-based schemes in a more 666 deterministic manner. 668 6. DLEP Message Processing 670 Communication between DLEP peers consists of a bidirectional stream 671 of signals, each signal consisting of a signal header and an 672 unordered list of data items. Both signal headers and data items are 673 encoded as TLV (Type-Length-Value) structures. In this document, the 674 data items following the signal header are described as being 675 'contained in' the signal. 677 All integer values in all TLV structures MUST be in network byte- 678 order. 680 There is no restriction on the order of data items following a 681 signal, and the multiplicity of duplicate data items is defined by 682 the definition of the signal declared by the type in the signal 683 header. 685 If an unrecognized, or unexpected signal is received, or a received 686 signal contains unrecognized, invalid or disallowed duplicate data 687 items, the receiving peer MUST terminate the session by issuing a 688 Peer Termination signal (Section 7.7) with a Status data item 689 (Section 8.2) containing the most relevant status code, and then 690 close the TCP connection: 692 6.1. DLEP Signal Header 694 The DLEP signal header contains the following fields: 696 0 1 2 3 697 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 1 698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 699 | Signal Type | Length | Data Items... 700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 702 Figure 3: DLEP Signal Header 704 Signal Type: One of the DLEP Signal Type values defined in this 705 document. 707 Length: The length, expressed as a 16-bit unsigned integer, of all 708 of the DLEP data items associated with this signal. This length 709 does not include the length of the header itself 711 Data Items: One or more DLEP data items, encoded in TLVs, as defined 712 in this document. 714 6.2. DLEP Generic Data Item 716 All DLEP data items contain the following fields: 718 0 1 2 3 719 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 1 720 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 721 | Data Item Type| Length | Value... | 722 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 724 Figure 4: DLEP Generic Data Item 726 Data Item Type: An 8-bit unsigned integer field specifying the data 727 item being sent. 729 Length: An 8-bit length of the value field of the data item. 731 Value: A field of length which contains data specific to a 732 particular data item. 734 7. DLEP Signals 736 As mentioned above, all DLEP signals begin with the DLEP signal 737 header structure. Therefore, in the following descriptions of 738 specific signals, this header structure is assumed, and will not be 739 replicated. 741 Following is the set of MANDATORY signals that must be recognized by 742 a DLEP compliant implementation. As mentioned before, not all 743 signals may be used during a session, but an implementation MUST 744 correctly process these signals when received. 746 The mandatory DLEP signals are: 748 +---------+-------------------------------+---------------+ 749 | Signal | Description | Section | 750 +---------+-------------------------------+---------------+ 751 | TBD | Peer Discovery | Section 7.1 | 752 | TBD | Peer Offer | Section 7.2 | 753 | TBD | Peer Initialization | Section 7.3 | 754 | TBD | Peer Initialization ACK | Section 7.4 | 755 | TBD | Peer Update | Section 7.5 | 756 | TBD | Peer Update ACK | Section 7.6 | 757 | TBD | Peer Termination | Section 7.7 | 758 | TBD | Peer Termination ACK | Section 7.8 | 759 | TBD | Destination Up | Section 7.9 | 760 | TBD | Destination Up ACK | Section 7.10 | 761 | TBD | Destination Down | Section 7.11 | 762 | TBD | Destination Down ACK | Section 7.12 | 763 | TBD | Destination Update | Section 7.13 | 764 | TBD | Heartbeat | Section 7.14 | 765 | TBD | Link Characteristics Request | Section 7.15 | 766 | TBD | Link Characteristics ACK | Section 7.16 | 767 +---------+-------------------------------+---------------+ 769 7.1. Peer Discovery Signal 771 A Peer Discovery signal SHOULD be sent by a router to discover DLEP 772 routers in the network. The Peer Offer signal (Section 7.2) is 773 required to complete the discovery process. Implementations MAY 774 implement their own retry heuristics in cases where it is determined 775 the Peer Discovery signal has timed out. 777 To construct a Peer Discovery signal, the Signal Type value in the 778 signal header is set to DLEP_PEER_DISCOVERY (value TBD). 780 The Peer Discovery signal MUST contain one of each of the following 781 data items: 783 o DLEP Version (Section 8.1) 785 o Heartbeat Interval (Section 8.5) 787 7.2. Peer Offer Signal 789 A Peer Offer signal MUST be sent by a DLEP modem in response to a 790 Peer Discovery signal (Section 7.1). Upon receipt, and processing, 791 of a Peer Offer signal, the router responds by issuing a TCP connect 792 to the address/port combination specified in the received Peer Offer. 794 The Peer Offer signal MUST be sent to the unicast address of the 795 originator of Peer Discovery. 797 To construct a Peer Offer signal, the Signal Type value in the signal 798 header is set to DLEP_PEER_OFFER (value TBD). 800 The Peer Offer signal MUST contain one of each of the following data 801 items: 803 o DLEP Version (Section 8.1) 805 o Heartbeat Interval (Section 8.5) 807 The Peer Offer signal MAY contain one of each of the following data 808 items: 810 o Peer Type (Section 8.4) 812 o DLEP Port (Section 8.3) 814 The Peer Offer signal MAY contain one or more of any of the following 815 data items, with different values: 817 o IPv4 Address (Section 8.9), with Add/Drop indicator = 1 819 o IPv6 Address (Section 8.10), with Add/Drop indicator = 1 821 If the Peer Offer signal includes a DLEP Port data item, the port 822 number specified MUST be used to establish the TCP session. If the 823 DLEP Port number is omitted, the receiver MUST use the DLEP well- 824 known port number (Section 11.7) to establish the TCP connection. 826 The IP Address data items indicate the unicast address the receiver 827 of Peer Offer MUST use when connecting the DLEP TCP session. If 828 multiple IP Address items are present in the Peer Offer signal, 829 implementations MAY use their own heuristics to select the address to 830 connect to. If no IP Address data items are included in the Peer 831 Offer signal, the receiver MUST use the origin address of the signal 832 as the IP address to establish the TCP connection. 834 7.3. Peer Initialization Signal 836 A Peer Initialization signal MUST be sent by a router as the first 837 signal of the DLEP TCP session. It is sent by the router after a TCP 838 connect to an address/port combination that was obtained either via 839 receipt of a Peer Offer, or from a-priori configuration. 841 If any optional extensions are supported by the implementation, they 842 MUST be enumerated in the Extensions Supported data item. If an 843 Extensions Supported data item does NOT exist in a Peer 844 Initialization signal, the receiver of the signal MUST conclude that 845 there is NO support for extensions in the sender. 847 If any experimental signals or data items are used by the 848 implementation, they MUST be enumerated in one or more Experimental 849 Definition data items. If there are no Experimental Definition data 850 items in a Peer Initialization signal, the receiver of the signal 851 MUST conclude that NO experimental definitions are in use by the 852 sender. 854 To construct a Peer Initialization signal, the Signal Type value in 855 the signal header is set to DLEP_PEER_INITIALIZATION (value TBD). 857 The Peer Initialization signal MUST contain one of each of the 858 following data items: 860 o DLEP Version (Section 8.1) 862 o Heartbeat Interval (Section 8.5) 864 The Peer Initialization signal MAY contain one of each of the 865 following data items: 867 o Peer Type (Section 8.4) 869 o Extensions Supported (Section 8.6) 871 The Peer Initialization signal MAY contain one or more of any of the 872 following data items, with different values: 874 o Experimental Definition (Section 8.7) 876 7.4. Peer Initialization ACK Signal 878 A Peer Initialization ACK signal MUST be sent in response to a 879 received Peer Initialization signal (Section 7.3). The Peer 880 Initialization ACK signal completes the TCP-level DLEP session 881 establishment; the sender of the signal should transition to an 'in- 882 session' state when the signal is sent, and the receiver should 883 transition to the 'in-session' state upon receipt (and successful 884 parsing) of a Peer Initialization ACK signal. 886 All supported metric data items MUST be included in the Peer 887 Initialization ACK signal, with default values to be used on a 888 'modem-wide' basis. This can be viewed as the modem 'declaring' all 889 supported metrics at DLEP session initialization. Receipt of any 890 DLEP signal containing a metric data item NOT included in the Peer 891 Initialization ACK signal MUST be treated as an error, resulting in 892 the termination of the DLEP session between router and modem. 894 If any optional extensions are supported by the modem, they MUST be 895 enumerated in the Extensions Supported data item. If an Extensions 896 Supported data item does NOT exist in a Peer Initialization ACK 897 signal, the receiver of the signal MUST conclude that there is NO 898 support for extensions in the sender. 900 If any experimental signals or data items are used by the 901 implementation, they MUST be enumerated in one or more Experimental 902 Definition data items. If there are no Experimental Definition data 903 items in a Peer Initialization ACK signal, the receiver of the signal 904 MUST conclude that NO experimental definitions are in use by the 905 sender. 907 After the Peer Initialization/Peer Initialization ACK signals have 908 been successfully exchanged, implementations MUST only utilize 909 extensions and experimental definitions that are supported by BOTH 910 peers. 912 To construct a Peer Initialization ACK signal, the Signal Type value 913 in the signal header is set to DLEP_PEER_INIT_ACK (value TBD). 915 The Peer Initialization ACK signal MUST contain one of each of the 916 following data items: 918 o DLEP Version (Section 8.1) 920 o Heartbeat Interval (Section 8.5) 922 o Maximum Data Rate (Receive) (Section 8.13) 923 o Maximum Data Rate (Transmit) (Section 8.14) 925 o Current Data Rate (Receive) (Section 8.15) 927 o Current Data Rate (Transmit) (Section 8.16) 929 o Latency (Section 8.17) 931 The Peer Initialization ACK signal MAY contain one of each of the 932 following data items: 934 o Status (Section 8.2) 936 o Peer Type (Section 8.4) 938 o Resources (Receive) (Section 8.18) 940 o Resources (Transmit) (Section 8.19) 942 o Relative Link Quality (Receive) (Section 8.20) 944 o Relative Link Quality (Transmit) (Section 8.21) 946 o Extensions Supported (Section 8.6) 948 The Peer Initialization ACK signal MAY contain one or more of any of 949 the following data items, with different values: 951 o Experimental Definition (Section 8.7) 953 7.5. Peer Update Signal 955 A Peer Update signal MAY be sent by a DLEP peer to indicate local 956 Layer 3 address changes, or for metric changes on a modem-wide basis. 957 For example, addition of an IPv4 address to the router MAY prompt a 958 Peer Update signal to its attached DLEP modems. Also, a modem that 959 changes its Maximum Data Rate for all destinations MAY reflect that 960 change via a Peer Update signal to its attached router(s). 962 Concerning Layer 3 addresses, if the modem is capable of 963 understanding and forwarding this information (via proprietary 964 mechanisms), the address update would prompt any remote DLEP modems 965 (DLEP-enabled modems in a remote node) to issue a Destination Update 966 signal (Section 7.13) to their local routers with the new (or 967 deleted) addresses. Modems that do not track Layer 3 addresses 968 SHOULD silently parse and ignore the Peer Update signal. Modems that 969 track Layer 3 addresses MUST acknowledge the Peer Update with a Peer 970 Update ACK signal (Section 7.6). Routers receiving a Peer Update 971 with metric changes MUST apply the new metric to all destinations 972 (remote nodes) accessible via the modem. Supporting implementations 973 are free to employ heuristics to retransmit Peer Update signals. The 974 sending of Peer Update signals for Layer 3 address changes SHOULD 975 cease when a either participant (router or modem) determines that the 976 other implementation does NOT support Layer 3 address tracking. 978 If metrics are supplied with the Peer Update signal (e.g., Maximum 979 Data Rate), these metrics are considered to be modem-wide, and 980 therefore MUST be applied to all destinations in the information base 981 associated with the router/modem session. 983 To construct a Peer Update signal, the Signal Type value in the 984 signal header is set to DLEP_PEER_UPDATE (value TBD). 986 The Peer Update signal MAY contain one of each of the following data 987 items: 989 o Maximum Data Rate (Receive) (Section 8.13) 991 o Maximum Data Rate (Transmit) (Section 8.14) 993 o Current Data Rate (Receive) (Section 8.15) 995 o Current Data Rate (Transmit) (Section 8.16) 997 o Latency (Section 8.17) 999 o Resources (Receive) (Section 8.18) 1001 o Resources (Transmit) (Section 8.19) 1003 o Relative Link Quality (Receive) (Section 8.20) 1005 o Relative Link Quality (Transmit) (Section 8.21) 1007 The Peer Update signal MAY contain one or more of the following data 1008 items, with different values: 1010 o IPv4 Address (Section 8.9) 1012 o IPv6 Address (Section 8.10) 1014 7.6. Peer Update ACK Signal 1016 A Peer Update ACK signal MUST be sent by implementations supporting 1017 Layer 3 address tracking and/or modem-wide metrics to indicate 1018 whether a Peer Update signal (Section 7.5) was successfully 1019 processed. If the Peer Update ACK is issued, it MUST contain a 1020 Status data item, indicating the success or failure of processing the 1021 received Peer Update. 1023 To construct a Peer Update ACK signal, the Signal Type value in the 1024 signal header is set to DLEP_PEER_UPDATE_ACK (value TBD). 1026 The Peer Update ACK signal MAY contain one of each of the following 1027 data items: 1029 o Status (Section 8.2) 1031 A receiver of a Peer Update ACK signal without a Status data item 1032 MUST behave as if a Status data item with code 'Success' had been 1033 received. 1035 7.7. Peer Termination Signal 1037 A Peer Termination signal MUST be sent by a DLEP participant when the 1038 router/modem session needs to be terminated. Implementations 1039 receiving a Peer Termination signal MUST send a Peer Termination ACK 1040 signal (Section 7.8) to confirm the termination process. The sender 1041 of a Peer Termination signal is free to define its heuristics in 1042 event of a timeout. The receiver of a Peer Termination signal MUST 1043 release all resources allocated for the router/modem session, and 1044 MUST eliminate all destinations in the information base accessible 1045 via the router/modem pair represented by the session. Router and 1046 modem state machines are returned to the 'discovery' state. No 1047 Destination Down signals (Section 7.11) are sent. 1049 To construct a Peer Termination signal, the Signal Type value in the 1050 signal header is set to DLEP_PEER_TERMINATION (value TBD). 1052 The Peer Termination signal MAY contain one of each of the following 1053 data items: 1055 o Status (Section 8.2) 1057 A receiver of a Peer Termination signal without a Status data item 1058 MUST behave as if a Status data item with status code 'Success' had 1059 been received. 1061 7.8. Peer Termination ACK Signal 1063 A Peer Termination ACK signal MUST be sent by a DLEP peer in response 1064 to a received Peer Termination signal (Section 7.7). Receipt of a 1065 Peer Termination ACK signal completes the teardown of the router/ 1066 modem session. 1068 To construct a Peer Termination ACK signal, the Signal Type value in 1069 the signal header is set to DLEP_PEER_TERMINATION_ACK (value TBD). 1071 The Peer Termination ACK signal MAY contain one of each of the 1072 following data items: 1074 o Status (Section 8.2) 1076 A receiver of a Peer Termination ACK signal without a Status data 1077 item MUST behave as if a Status data item with status code 'Success' 1078 had been received. 1080 7.9. Destination Up Signal 1082 A DLEP participant MUST send a Destination Up signal to report that a 1083 new destination has been detected. A Destination Up ACK signal 1084 (Section 7.10) is required to confirm a received Destination Up. A 1085 Destination Up signal can be sent either by the modem, to indicate 1086 that a new remote node has been detected, or by the router, to 1087 indicate the presence of a new logical destination (e.g., a Multicast 1088 group) exists in the network. 1090 The sender of the Destination Up signal is free to define its retry 1091 heuristics in event of a timeout. When a Destination Up signal is 1092 received and successfully processed, the receiver should add 1093 knowledge of the new destination to its information base, indicating 1094 that the destination is accessible via the modem/router pair. 1096 To construct a Destination Up signal, the Signal Type value in the 1097 signal header is set to DLEP_DESTINATION_UP (value TBD). 1099 The Destination Up signal MUST contain one of each of the following 1100 data items: 1102 o MAC Address (Section 8.8) 1104 The Destination Up signal MAY contain one of each of the following 1105 data items: 1107 o Maximum Data Rate (Receive) (Section 8.13) 1109 o Maximum Data Rate (Transmit) (Section 8.14) 1111 o Current Data Rate (Receive) (Section 8.15) 1113 o Current Data Rate (Transmit) (Section 8.16) 1115 o Latency (Section 8.17) 1116 o Resources (Receive) (Section 8.18) 1118 o Resources (Transmit) (Section 8.19) 1120 o Relative Link Quality (Receive) (Section 8.20) 1122 o Relative Link Quality (Transmit) (Section 8.21) 1124 The Destination Up signal MAY contain one or more of the following 1125 data items, with different values: 1127 o IPv4 Address (Section 8.9) 1129 o IPv6 Address (Section 8.10) 1131 o IPv4 Attached Subnet (Section 8.11) 1133 o IPv6 Attached Subnet (Section 8.12) 1135 If the sender has IPv4 and/or IPv6 address information for a 1136 destination it SHOULD include the relevant data items in the 1137 Destination Up signal, reducing the need for the receiver to probe 1138 for any address. 1140 7.10. Destination Up ACK Signal 1142 A DLEP participant MUST send a Destination Up ACK signal to indicate 1143 whether a Destination Up signal (Section 7.9) was successfully 1144 processed. 1146 To construct a Destination Up ACK signal, the Signal Type value in 1147 the signal header is set to DLEP_DESTINATION_UP_ACK (value TBD). 1149 The Destination Up ACK signal MUST contain one of each of the 1150 following data items: 1152 o MAC Address (Section 8.8) 1154 The Destination Up ACK signal MAY contain one of each of the 1155 following data items: 1157 o Status (Section 8.2) 1159 A receiver of a Destination Up ACK signal without a Status data item 1160 MUST behave as if a Status data item with status code 'Success' had 1161 been received. 1163 7.11. Destination Down Signal 1165 A DLEP peer MUST send a Destination Down signal to report when a 1166 destination (a remote node or a multicast group) is no longer 1167 reachable. A Destination Down ACK signal (Section 7.12) MUST be sent 1168 by the recipient of a Destination Down signal to confirm that the 1169 relevant data has been removed from the information base. The sender 1170 of the Destination Down signal is free to define its retry heuristics 1171 in event of a timeout. 1173 To construct a Destination Down signal, the Signal Type value in the 1174 signal header is set to DLEP_DESTINATION_DOWN (value TBD). 1176 The Destination Down signal MUST contain one of each of the following 1177 data items: 1179 o MAC Address (Section 8.8) 1181 7.12. Destination Down ACK Signal 1183 A DLEP participant MUST send a Destination Down ACK signal to 1184 indicate whether a received Destination Down signal (Section 7.11) 1185 was successfully processed. If successfully processed, the sender of 1186 the ACK MUST have removed all entries in the information base that 1187 pertain to the referenced destination. 1189 To construct a Destination Down ACK signal, the Signal Type value in 1190 the signal header is set to DLEP_DESTINATION_DOWN_ACK (value TBD). 1192 The Destination Down ACK signal MUST contain one of each of the 1193 following data items: 1195 o MAC Address (Section 8.8) 1197 The Destination Down ACK signal MAY contain one of each of the 1198 following data items: 1200 o Status (Section 8.2) 1202 A receiver of a Destination Down ACK signal without a Status data 1203 item MUST behave as if a Status data item with status code 'Success' 1204 had been received. 1206 7.13. Destination Update Signal 1208 A DLEP participant SHOULD send the Destination Update signal when it 1209 detects some change in the information base for a given destination 1210 (remote node or multicast group). Some examples of changes that 1211 would prompt a Destination Update signal are: 1213 o Change in link metrics (e.g., Data Rates) 1215 o Layer 3 addressing change (for implementations that support it) 1217 To construct a Destination Update signal, the Signal Type value in 1218 the signal header is set to DLEP_DESTINATION_UPDATE (value TBD). 1220 The Destination Update signal MUST contain one of each of the 1221 following data items: 1223 o MAC Address (Section 8.8) 1225 The Destination Update signal MAY contain one of each of the 1226 following data items: 1228 o Maximum Data Rate (Receive) (Section 8.13) 1230 o Maximum Data Rate (Transmit) (Section 8.14) 1232 o Current Data Rate (Receive) (Section 8.15) 1234 o Current Data Rate (Transmit) (Section 8.16) 1236 o Latency (Section 8.17) 1238 o Resources (Receive) (Section 8.18) 1240 o Resources (Transmit) (Section 8.19) 1242 o Relative Link Quality (Receive) (Section 8.20) 1244 o Relative Link Quality (Transmit) (Section 8.21) 1246 The Destination Update signal MAY contain one or more of the 1247 following data items, with different values: 1249 o IPv4 Address (Section 8.9) 1251 o IPv6 Address (Section 8.10) 1253 o IPv4 Attached Subnet (Section 8.11) 1255 o IPv6 Attached Subnet (Section 8.12) 1257 7.14. Heartbeat Signal 1259 A Heartbeat signal SHOULD be sent by a DLEP participant every N 1260 seconds, where N is defined in the Heartbeat Interval field of the 1261 Peer Initialization signal (Section 7.3) or Peer Initialization ACK 1262 signal (Section 7.4). Note that implementations setting the 1263 Heartbeat Interval to 0 effectively set the interval to an infinite 1264 value, therefore, in those cases, this signal SHOULD NOT be sent. 1266 The signal is used by participants to detect when a DLEP session 1267 partner (either the modem or the router) is no longer communicating. 1268 Participants SHOULD allow two (2) heartbeat intervals to expire with 1269 no traffic on the router/modem session before initiating DLEP session 1270 termination procedures. 1272 To construct a Heartbeat signal, the Signal Type value in the signal 1273 header is set to DLEP_PEER_HEARTBEAT (value TBD). 1275 There are no valid data items for the Heartbeat signal. 1277 7.15. Link Characteristics Request Signal 1279 The Link Characteristics Request signal MAY be sent by the router to 1280 request that the modem initiate changes for specific characteristics 1281 of the link. The request can reference either a real (e.g., a remote 1282 node), or a logical (e.g., a multicast group) destination within the 1283 network. 1285 The Link Characteristics Request signal contains either a Current 1286 Data Rate (CDRR or CDRT) data item to request a different datarate 1287 than what is currently allocated, a Latency data item to request that 1288 traffic delay on the link not exceed the specified value, or both. A 1289 Link Characteristics ACK signal (Section 7.16) is required to 1290 complete the request. Issuing a Link Characteristics Request with 1291 ONLY the MAC Address data item is a mechanism a peer MAY use to 1292 request metrics (via the Link Characteristics ACK) from its partner. 1294 The sender of a Link Characteristics Request signal MAY attach a 1295 timer to the request using the Link Characteristics ACK Timer data 1296 item. If a Link Characteristics ACK signal is received after the 1297 timer expires, the sender MUST assume that the request failed. 1298 Implementations are free to define their retry heuristics in event of 1299 a timeout. 1301 To construct a Link Characteristics Request signal, the Signal Type 1302 value in the signal header is set to DLEP_LINK_CHAR_REQ (value TBD). 1304 The Link Characteristics Request signal MUST contain one of each of 1305 the following data items: 1307 o MAC Address (Section 8.8) 1309 The Link Characteristics Request signal MAY contain one of each of 1310 the following data items: 1312 o Link Characteristics ACK Timer (Section 8.22) 1314 o Current Data Rate (Receive) (Section 8.15) 1316 o Current Data Rate (Transmit) (Section 8.16) 1318 o Latency (Section 8.17) 1320 7.16. Link Characteristics ACK Signal 1322 A DLEP participant MUST send a Link Characteristics ACK signal to 1323 indicate whether a received Link Characteristics Request signal 1324 (Section 7.15) was successfully processed. The Link Characteristics 1325 ACK signal SHOULD contain a complete set of metric data items. It 1326 MUST contain the same metric types as the request. The values in the 1327 metric data items in the Link Characteristics ACK signal MUST reflect 1328 the link characteristics after the request has been processed. 1330 If an implementation is not able to alter the characteristics of the 1331 link in the manner requested, then a Status data item with status 1332 code 'Request Denied' MUST be added to the signal. 1334 To construct a Link Characteristics Request ACK signal, the Signal 1335 Type value in the signal header is set to DLEP_LINK_CHAR_ACK (value 1336 TBD). 1338 The Link Characteristics ACK signal MUST contain one of each of the 1339 following data items: 1341 o MAC Address (Section 8.8) 1343 The Link Characteristics ACK signal MAY contain one of each of the 1344 following data items: 1346 o Current Data Rate (Receive) (Section 8.15) 1348 o Current Data Rate (Transmit) (Section 8.16) 1350 o Latency (Section 8.17) 1351 o Resources (Receive) (Section 8.18) 1353 o Resources (Transmit) (Section 8.19) 1355 o Relative Link Quality (Receive) (Section 8.20) 1357 o Relative Link Quality (Transmit) (Section 8.21) 1359 o Status (Section 8.2) 1361 A receiver of a Link Characteristics ACK signal without a Status data 1362 item MUST behave as if a Status data item with status code 'Success' 1363 had been received. 1365 8. DLEP Data Items 1367 Following is the list of MANDATORY data items that must be recognized 1368 by a DLEP compliant implementation. As mentioned before, not all 1369 data items need be used during a session, but an implementation MUST 1370 correctly process these data items when correctly associated with a 1371 signal. 1373 The mandatory DLEP data items are: 1375 +------------+--------------------------------------+---------------+ 1376 | Data Item | Description | Section | 1377 +------------+--------------------------------------+---------------+ 1378 | TBD | DLEP Version | Section 8.1 | 1379 | TBD | Status | Section 8.2 | 1380 | TBD | DLEP Port | Section 8.3 | 1381 | TBD | Peer Type | Section 8.4 | 1382 | TBD | Heartbeat Interval | Section 8.5 | 1383 | TBD | Extensions Supported | Section 8.6 | 1384 | TBD | Experimental Definition | Section 8.7 | 1385 | TBD | MAC Address | Section 8.8 | 1386 | TBD | IPv4 Address | Section 8.9 | 1387 | TBD | IPv6 Address | Section 8.10 | 1388 | TBD | IPv4 Attached Subnet | Section 8.11 | 1389 | TBD | IPv6 Attached Subnet | Section 8.12 | 1390 | TBD | Maximum Data Rate (Receive) MDRR) | Section 8.13 | 1391 | TBD | Maximum Data Rate (Transmit) (MDRT) | Section 8.14 | 1392 | TBD | Current Data Rate (Receive) (CDRR) | Section 8.15 | 1393 | TBD | Current Data Rate (Transmit) (CDRT) | Section 8.16 | 1394 | TBD | Latency | Section 8.17 | 1395 | TBD | Resources (Receive) (RESR) | Section 8.18 | 1396 | TBD | Resources (Transmit) (REST) | Section 8.19 | 1397 | TBD | Relative Link Quality (Receive) | Section 8.20 | 1398 | | (RLQR) | | 1399 | TBD | Relative Link Quality (Transmit) | Section 8.21 | 1400 | | (RLQT) | | 1401 | TBD | Link Characteristics ACK Timer | Section 8.22 | 1402 +------------+--------------------------------------+---------------+ 1404 8.1. DLEP Version 1406 The DLEP Version data item MUST appear in the Peer Discovery 1407 (Section 7.1), Peer Offer (Section 7.2), Peer Initialization 1408 (Section 7.3) and Peer Initialization ACK (Section 7.4) signals The 1409 Version data item is used to indicate the version of the protocol 1410 running in the originator. A DLEP implementation MAY use this 1411 information to decide if the potential session partner is running at 1412 a supported level. 1414 The DLEP Version data item contains the following fields: 1416 0 1 2 3 1417 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 1418 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1419 | Data Item Type| Length = 4 | Major Version | 1420 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1421 | Minor Version | 1422 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1423 Data Item Type: TBD 1425 Length: 4 1427 Major Version: Major version of the DLEP protocol. 1429 Minor Version: Minor version of the DLEP protocol. 1431 Support of this draft is indicated by setting the Major Version to 1432 '0', and the Minor Version to '8' (i.e., Version 0.8). 1434 8.2. Status 1436 The Status data item is MAY appear in the Peer Initialization ACK 1437 (Section 7.4), Peer Termination (Section 7.7), Peer Termination ACK 1438 (Section 7.8), Peer Update ACK (Section 7.6), Destination Up ACK 1439 (Section 7.10), Destination Down ACK (Section 7.12) and Link 1440 Characteristics ACK (Section 7.16) signals as part of an 1441 acknowledgement from either the modem or the router, to indicate the 1442 success or failure of the previously received signal. 1444 The Status data item contains the following fields: 1446 0 1 2 1447 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1449 | Data Item Type| Length = 1 | Code | 1450 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1452 Data Item Type: TBD 1454 Length: 1 1456 Status Code: One of the codes defined below. 1458 +-------------------+-----------------------------------------------+ 1459 | Status Code | Reason | 1460 +-------------------+-----------------------------------------------+ 1461 | Success | The signal was processed successfully. | 1462 | Unknown Signal | The signal was not recognized by the | 1463 | | implementation. | 1464 | Invalid Signal | One or more data items in the signal are | 1465 | | invalid, unexpected or duplicated. | 1466 | Unexpected Signal | The signal was not expected while the machine | 1467 | | was in this state, e.g., a Peer | 1468 | | Initialization signal after session | 1469 | | establishment. | 1470 | Request Denied | The receiver has not completed the request. | 1471 | Timed Out | The request could not be completed in the | 1472 | | time allowed. | 1473 +-------------------+-----------------------------------------------+ 1475 8.3. DLEP Port 1477 The DLEP Port data item MAY appear in the Peer Offer signal 1478 (Section 7.2). The DLEP Port data item indicates the TCP Port number 1479 on the DLEP server available for connections. If provided, the 1480 receiver MUST use this information to perform the TCP connect to the 1481 DLEP server. 1483 The DLEP Port data item contains the following fields: 1485 0 1 2 3 1486 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 1487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1488 | Data Item Type| Length = 2 | TCP Port Number | 1489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1491 Data Item Type: TBD 1493 Length: 2 1495 TCP Port Number: TCP Port number on the DLEP server. 1497 8.4. Peer Type 1499 The Peer Type data item MAY appear in both the Peer Discovery 1500 (Section 7.1) and Peer Offer (Section 7.2) signals. The Peer Type 1501 data item is used by the router and modem to give additional 1502 information as to its type. The peer type is a string and is 1503 envisioned to be used for informational purposes (e.g., as output in 1504 a display command). 1506 The Peer Type data item contains the following fields: 1508 0 1 2 3 1509 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 1510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1511 | Data Item Type| Length = peer | Peer Type | 1512 | | type len | | 1513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1515 Data Item Type: TBD 1517 Length: Length of peer type string. 1519 Peer Type: UTF-8 encoded string. For example, a satellite modem 1520 might set this variable to "Satellite terminal". 1522 An implementation MUST NOT assume the Peer Type is NUL-terminated. 1524 8.5. Heartbeat Interval 1526 The Heartbeat Interval data item MUST appear in the Peer Discovery 1527 (Section 7.1), Peer Offer (Section 7.2), Peer Initialization 1528 (Section 7.3) and Peer Initialization ACK (Section 7.4) signals to 1529 indicate the desired Heartbeat timeout window. The receiver MUST 1530 either accept the timeout interval supplied by the sender, or reject 1531 the Peer Initialization, and close the socket. Implementations MUST 1532 implement heuristics such that DLEP signals sent/received reset the 1533 timer interval. 1535 The Interval is used to specify a period (in seconds) for Heartbeat 1536 signals (Section 7.14). By specifying an Interval value of 0, 1537 implementations MAY indicates the desire to disable Heartbeat signals 1538 entirely (i.e., the Interval is set to an infinite value), however, 1539 it is strongly recommended that implementations use non 0 timer 1540 values. 1542 A DLEP session will be considered inactive, and MUST be torn down, by 1543 an implementation detecting that two (2) Heartbeat intervals have 1544 transpired without receipt of any DLEP signals. 1546 The Heartbeat Interval data item contains the following fields: 1548 0 1 2 3 1549 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 1550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1551 | Data Item Type| Length = 2 | Interval | 1552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1553 Data Item Type: TBD 1555 Length: 2 1557 Interval: 0 = Do NOT use heartbeats on this peer-to-peer session. 1558 Non-zero = Interval, in seconds, for heartbeat signals. 1560 8.6. Extensions Supported 1562 The Extensions Supported data item MAY be used in both the Peer 1563 Initialization and Peer Initialization ACK signals. The Extensions 1564 Supported data item is used by the router and modem to negotiate 1565 additional optional functionality they are willing to support. The 1566 Extensions List is a concatenation of the types of each supported 1567 extension, found in the IANA DLEP Extensions repository. 1569 The Extensions Supported data item contains the following fields: 1571 0 1 2 3 1572 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 1573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 | Data Item Type| Length = No. | Extensions List | 1575 | | of values | | 1576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1578 Data Item Type: TBD 1580 Length: Number of Extensions supported. 1582 Extension List: A list of extensions supported, identified by their 1583 1-octet value as listed in the extensions registry. 1585 8.7. Experimental Definition 1587 The Experimental Definition data item MAY be used in both the Peer 1588 Initialization and Peer Initialization ACK signals. The Experimental 1589 Definition data item is used by the router and modem to indicate the 1590 formats to be used for experimental signals and data items for the 1591 given peer session. The formats are identified by using a string 1592 that matches the 'name' given to the experiment. 1594 The Experimental Definition item contains the following fields: 1596 0 1 2 3 1597 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 1598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1599 | Data Item Type| Length = len. | Experiment Name | 1600 | | of Experiment | | 1601 | | name | | 1602 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 Data Item Type: TBD 1606 Length: Length of the name string for the Experiment. 1608 Experiment Name: UTF-8 encoded string, containing the name of the 1609 experiment being utilized. 1611 An implementation receiving this data item MUST compare the received 1612 string to a list of experiments that it supports. An implementation 1613 MUST NOT assume the Experiment Name is NUL-terminated. 1615 8.8. MAC Address 1617 The MAC address data item MUST appear in all destination-oriented 1618 signals (i.e., Destination Up (Section 7.9), Destination Up ACK 1619 (Section 7.10), Destination Down (Section 7.11), Destination Down ACK 1620 (Section 7.12), Destination Update (Section 7.13), Link 1621 Characteristics Request (Section 7.15), and Link Characteristics ACK 1622 (Section 7.16)). The MAC Address data item contains the address of 1623 the destination on the remote node. The MAC address MAY be either a 1624 physical or a virtual destination. Examples of a virtual destination 1625 would be a multicast MAC address, or the broadcast MAC 1626 (FF:FF:FF:FF:FF:FF). 1628 0 1 2 3 1629 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 1630 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1631 | Data Item Type| Length = 6 | MAC Address | 1632 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1633 | MAC Address | 1634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1636 Data Item Type: TBD 1638 Length: 6 1640 MAC Address: MAC Address of the destination (either physical or 1641 virtual). 1643 8.9. IPv4 Address 1645 The IPv4 Address data item MUST appear in the Peer Offer signal 1646 (Section 7.2), and MAY appear in the Peer Update (Section 7.5), 1647 Destination Up (Section 7.9) and Destination Update (Section 7.13) 1648 signals. When included in Destination signals, this data item 1649 contains the IPv4 address of the destination. In the Peer Offer 1650 signal, it contains the IPv4 address of the originating peer to be 1651 used to establish a DLEP session. In either case, the data item also 1652 contains an indication of whether this is a new or existing address, 1653 or is a deletion of a previously known address. When used in a Peer 1654 Offer signal the Add/Drop Indicator MUST be 1 (i.e. Add). 1656 The IPv4 Address data item contains the following fields: 1658 0 1 2 3 1659 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 1660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1661 | Data Item Type| Length = 5 | Add/Drop | IPv4 Address | 1662 | | | Indicator | | 1663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1664 | IPv4 Address | 1665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1667 Data Item Type: TBD 1669 Length: 5 1671 Add/Drop: Value indicating whether this is a new or existing address 1672 (1), or a withdrawal of an address (0). 1674 IPv4 Address: The IPv4 address of the destination or peer. 1676 8.10. IPv6 Address 1678 The IPv6 Address data item MUST appear in the Peer Offer signal 1679 (Section 7.2), and MAY appear in the Peer Update (Section 7.5), 1680 Destination Up (Section 7.9) and Destination Update (Section 7.13) 1681 signals. When included in Destination signals, this data item 1682 contains the IPv6 address of the destination. In the Peer Offer 1683 signal, it contains the IPv6 address of the originating peer to be 1684 used to establish a DLEP session. In either case, the data item also 1685 contains an indication of whether this is a new or existing address, 1686 or is a deletion of a previously known address. When used in a Peer 1687 Offer signal the Add/Drop Indicator MUST be 1 (i.e. Add). 1689 The IPv6 Address data item contains the following fields: 1691 0 1 2 3 1692 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 1693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1694 | Data Item Type| Length = 17 | Add/Drop | IPv6 Address | 1695 | | | Indicator | | 1696 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1697 | IPv6 Address | 1698 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1699 | IPv6 Address | 1700 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1701 | IPv6 Address | 1702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1703 | IPv6 Address | 1704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1706 Data Item Type: TBD 1708 Length: 17 1710 Add/Drop: Value indicating whether this is a new or existing address 1711 (1), or a withdrawal of an address (0). 1713 IPv6 Address: IPv6 Address of the destination or peer. 1715 8.11. IPv4 Attached Subnet 1717 The DLEP IPv4 Attached Subnet allows a device to declare that it has 1718 an IPv4 subnet (e.g., a stub network) attached. Once an IPv4 Subnet 1719 has been declared on a device, the declaration can NOT be withdrawn 1720 without terminating the destination (via the Destination Down signal) 1721 and re-issuing the Destination Up signal. 1723 The DLEP IPv4 Attached Subnet data item data item contains the 1724 following fields: 1726 0 1 2 3 1727 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 1728 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1729 |Data Item Type | Length = 5 | IPv4 Attached Subnet | 1730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1731 | IPv4 Attached Subnet | Subnet Mask | 1732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1734 Data Item Type: TBD 1736 Length: 5 1738 IPv4 Subnet: The IPv4 subnet reachable at the destination. 1740 Subnet Mask: A subnet mask (0-32) to be applied to the IPv4 subnet. 1742 8.12. IPv6 Attached Subnet 1744 The DLEP IPv6 Attached Subnet allows a device to declare that it has 1745 an IPv6 subnet (e.g., a stub network) attached. As in the case of 1746 the IPv4 attached Subnet data item above, once an IPv6 attached 1747 subnet has been declared, it can NOT be withdrawn without terminating 1748 the destination (via Destination Down) and re-issuing the Destination 1749 Up signal. 1751 The DLEP IPv6 Attached Subnet data item data item contains the 1752 following fields: 1754 0 1 2 3 1755 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 1756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1757 | Data Item Type| Length = 17 | IPv6 Attached Subnet | 1758 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1759 | IPv6 Attached Subnet | 1760 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1761 | IPv6 Attached Subnet | 1762 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1763 | IPv6 Attached Subnet | 1764 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1765 | IPv6 Attached Subnet | Subnet Mask | 1766 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1768 Data Item Type: TBD 1770 Length: 17 1772 IPv4 Subnet: The IPv6 subnet reachable at the destination. 1774 Subnet Mask: A subnet mask (0-128) to be applied to the IPv6 subnet. 1776 8.13. Maximum Data Rate (Receive) 1778 The Maximum Data Rate (Receive) (MDRR) data item MUST appear in the 1779 Peer Initialization ACK signal (Section 7.4), and MAY appear in the 1780 Peer Update (Section 7.5), Destination Up (Section 7.9) and 1781 Destination Update (Section 7.13) signals to indicate the maximum 1782 theoretical data rate, in bits per second, that can be achieved while 1783 receiving data on the link. 1785 The Maximum Data Rate (Receive) data item contains the following 1786 fields: 1788 0 1 2 3 1789 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 1790 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1791 | Data Item Type| Length = 8 | MDRR (bps) | 1792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1793 | MDRR (bps) | 1794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1795 | MDRR (bps) | 1796 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1798 Data Item Type: TBD 1800 Length: 8 1802 Maximum Data Rate (Receive): A 64-bit unsigned integer, representing 1803 the maximum theoretical data rate, in bits per second (bps), that 1804 can be achieved while receiving on the link. 1806 8.14. Maximum Data Rate (Transmit) 1808 The Maximum Data Rate (Transmit) (MDRT) data item MUST appear in the 1809 Peer Initialization ACK signal (Section 7.4), and MAY appear in the 1810 Peer Update (Section 7.5), Destination Up (Section 7.9) and 1811 Destination Update (Section 7.13) signals to indicate the maximum 1812 theoretical data rate, in bits per second, that can be achieved while 1813 transmitting data on the link. 1815 The Maximum Data Rate (Transmit) data item contains the following 1816 fields: 1818 0 1 2 3 1819 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 1820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1821 | Data Item Type| Length = 8 | MDRT (bps) | 1822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1823 | MDRT (bps) | 1824 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1825 | MDRT (bps) | 1826 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1828 Data Item Type: TBD 1830 Length: 8 1832 Maximum Data Rate (Transmit): A 64-bit unsigned integer, 1833 representing the maximum theoretical data rate, in bits per second 1834 (bps), that can be achieved while transmitting on the link. 1836 8.15. Current Data Rate (Receive) 1838 The Current Data Rate (Receive) (CDRR) data item MUST appear in the 1839 Peer Initialization ACK signal (Section 7.4), and MAY appear in the 1840 Peer Update (Section 7.5), Destination Up (Section 7.9), Destination 1841 Update (Section 7.13), Link Characteristics Request (Section 7.15) 1842 and Link Characteristics ACK (Section 7.16) signals to indicate the 1843 rate at which the link is currently operating for receiving traffic. 1844 When used in the Link Characteristics Request signal, CDRR represents 1845 the desired receive rate, in bits per second, on the link. 1847 The Current Data Rate (Receive) data item contains the following 1848 fields: 1850 0 1 2 3 1851 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 1852 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1853 | Data Item Type| Length = 8 | CDRR (bps) | 1854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1855 | CDRR (bps) | 1856 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1857 | CDRR (bps) | 1858 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1860 Data Item Type: TBD 1862 Length: 8 1864 Current Data Rate (Receive): A 64-bit unsigned integer, representing 1865 the current data rate, in bits per second, that is currently be 1866 achieved while receiving traffic on the link. 1868 If there is no distinction between current and maximum receive data 1869 rates, current data rate receive MUST be set equal to the maximum 1870 data rate receive. 1872 8.16. Current Data Rate (Transmit) 1874 The Current Data Rate Receive (CDRT) data item MUST appear in the 1875 Peer Initialization ACK signal (Section 7.4), and MAY appear in the 1876 Peer Update (Section 7.5), Destination Up (Section 7.9), Destination 1877 Update (Section 7.13), Link Characteristics Request (Section 7.15) 1878 and Link Characteristics ACK (Section 7.16) signals to indicate the 1879 rate at which the link is currently operating for transmitting 1880 traffic. When used in the Link Characteristics Request signal, CDRT 1881 represents the desired transmit rate, in bits per second, on the 1882 link. 1884 The Current Data Rate (Transmit) data item contains the following 1885 fields: 1887 0 1 2 3 1888 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 1889 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1890 | Data Item Type| Length = 8 | CDRT (bps) | 1891 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1892 | CDRT (bps) | 1893 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1894 | CDRT (bps) | 1895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1897 Data Item Type: TBD 1899 Length: 8 1901 Current Data Rate (Transmit): A 64-bit unsigned integer, 1902 representing the current data rate, in bits per second, that is 1903 currently be achieved while transmitting traffic on the link. 1905 If there is no distinction between current and maximum transmit data 1906 rates, current data rate transmit MUST be set equal to the maximum 1907 data rate transmit. 1909 8.17. Latency 1911 The Latency data item data item MUST appear in the Peer 1912 Initialization ACK signal (Section 7.4), and MAY appear in the Peer 1913 Update (Section 7.5), Destination Up (Section 7.9), Destination 1914 Update (Section 7.13), Link Characteristics Request (Section 7.15) 1915 and Link Characteristics ACK (Section 7.16) signals to indicate the 1916 amount of latency, in microseconds, on the link, or in the case of 1917 the Link Characteristics Request, to indicate the maximum latency 1918 required on the link. 1920 The Latency value is reported as delay. The calculation of latency 1921 is implementation dependent. For example, the latency may be a 1922 running average calculated from the internal queuing. 1924 0 1 2 3 1925 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 1926 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1927 | Data Item Type| Length = 4 | Latency in microseconds | 1928 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1929 | Latency (cont.) microsecs | 1930 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1931 Data Item Type: TBD 1933 Length: 4 1935 Latency: A 32-bit unsigned value, representing the transmission 1936 delay that a packet encounters as it is transmitted over the link. 1938 8.18. Resources (Receive) 1940 The Resources (Receive) (RESR) data item MAY appear in the Peer 1941 Initialization ACK signal (Section 7.4), Peer Update (Section 7.5), 1942 Destination Up (Section 7.9), Destination Update (Section 7.13) and 1943 Link Characteristics ACK (Section 7.16) signals to indicate the 1944 amount of recources for reception (with 0 meaning 'no resources 1945 available', and 100 meaning 'all resources available') at the 1946 destination. The list of resources that might be considered is 1947 beyond the scope of this document, and is left to implementations to 1948 decide. 1950 The Resources (Receive) data item contains the following fields: 1952 0 1 2 1953 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1955 | Data Item Type| Length = 1 | RESR | 1956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1958 Data Item Type: TBD 1960 Length: 1 1962 Resources (Receive): A percentage, 0-100, representing the amount of 1963 resources allocated to receiving data. 1965 If a device cannot calculate RESR, this data item SHOULD NOT be 1966 issued. 1968 8.19. Resources (Transmit) 1970 The Resources (Receive) (RESR) data item MAY appear in the Peer 1971 Initialization ACK signal (Section 7.4), Peer Update (Section 7.5), 1972 Destination Up (Section 7.9), Destination Update (Section 7.13) and 1973 Link Characteristics ACK (Section 7.16) signals to indicate the 1974 amount of recources for transmission (with 0 meaning 'no resources 1975 available', and 100 meaning 'all resources available') at the 1976 destination. The list of resources that might be considered is 1977 beyond the scope of this document, and is left to implementations to 1978 decide. 1980 The Resources (Transmit) data item contains the following fields: 1982 0 1 2 1983 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1984 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1985 | Data Item Type| Length = 1 | REST | 1986 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1988 Data Item Type: TBD 1990 Length: 1 1992 Resources (Transmit): A percentage, 0-100, representing the amount 1993 of resources allocated to transmitting data. 1995 If a device cannot calculate REST, this data item SHOULD NOT be 1996 issued. 1998 8.20. Relative Link Quality (Receive) 2000 The Relative Link Quality (Receive) (RLQR) data item MAY appear in 2001 the Peer Initialization ACK signal (Section 7.4), Peer Update 2002 (Section 7.5), Destination Up (Section 7.9), Destination Update 2003 (Section 7.13) and Link Characteristics ACK (Section 7.16) signals to 2004 indicate the quality of the link for receiving data as calculated by 2005 the originating peer. 2007 The Relative Link Quality (Receive) data item contains the following 2008 fields: 2010 0 1 2 2011 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 2012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2013 | Data Item Type| Length = 1 | RLQR | 2014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2016 Data Item Type: TBD 2018 Length: 1 2020 Relative Link Quality (Receive): A non-dimensional integer, 1-100, 2021 representing relative link quality. A value of 100 represents a 2022 link of the highest quality. 2024 If a device cannot calculate the RLQR, this data item SHOULD NOT be 2025 issued. 2027 8.21. Relative Link Quality (Transmit) 2029 The Relative Link Quality (Transmit) (RLQT) data item MAY appear in 2030 the Peer Initialization ACK signal (Section 7.4), Peer Update 2031 (Section 7.5), Destination Up (Section 7.9), Destination Update 2032 (Section 7.13) and Link Characteristics ACK (Section 7.16) signals to 2033 indicate the quality of the link for transmitting data as calculated 2034 by the originating peer. 2036 The Relative Link Quality (Transmit) data item contains the following 2037 fields: 2039 0 1 2 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 2041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2042 | Data Item Type| Length = 1 | RLQT | 2043 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2045 Data Item Type: TBD 2047 Length: 1 2049 Relative Link Quality (Transmit): A non-dimensional integer, 1-100, 2050 representing relative link quality. A value of 100 represents a 2051 link of the highest quality. 2053 If a device cannot calculate the RLQT, this data item SHOULD NOT be 2054 issued. 2056 8.22. Link Characteristics ACK Timer 2058 The Link Characteristics ACK Timer data item MAY appear in the Link 2059 Characterisitics Request signal (Section 7.15) to indicate the 2060 desired number of seconds to the sender will wait for a response to 2061 the request. If this data item is omitted, implementations 2062 supporting the Link Characteristics Request SHOULD choose a default 2063 value. 2065 The Link Characteristics ACK Timer data item contains the following 2066 fields: 2068 0 1 2 2069 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 2070 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2071 | Data Item Type| Length = 1 | Interval | 2072 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2074 Data Item Type: TBD 2075 Length: 1 2077 Interval: 0 = Do NOT use timeouts for Link Characteristics requests 2078 on this router/modem session. Non-zero = Interval, in seconds, to 2079 wait before considering a Link Characteristics Request has been 2080 lost. 2082 9. Credit-Windowing 2084 DLEP includes an OPTIONAL credit-windowing scheme analogous to the 2085 one documented in [RFC5578]. In this scheme, traffic between the 2086 router and modem is treated as two unidirectional windows. This 2087 document identifies these windows as the 'Modem Receive Window', or 2088 MRW, and the 'Router Receive Window', or RRW. 2090 If the OPTIONAL credit-windowing scheme is used, credits MUST be 2091 granted by the receiver on a given window - that is, on the 'Modem 2092 Receive Window' (MRW), the modem is responsible for granting credits 2093 to the router, allowing it (the router) to send data to the modem. 2094 Likewise, the router is responsible for granting credits on the RRW, 2095 which allows the modem to send data to the router. 2097 DLEP expresses all credit data in number of octets. The total number 2098 of credits on a window, and the increment to add to a grant, are 2099 always expressed as a 64-bit unsigned integer quantity. 2101 If used, credits are managed on a neighbor-specific basis; that is, 2102 separate credit counts are maintained for each neighbor requiring the 2103 service. Credits do not apply to the DLEP session that exists 2104 between routers and modems. 2106 If a peer is able to support the OPTIONAL credit-windowing scheme 2107 then it MUST include a Extensions Supported data item (Section 8.6) 2108 including the value DLEP_EXT_CREDITS (value TBD) in the appropriate 2109 Peer Initialization or Peer Initialization ACK signal. 2111 9.1. Credit-Windowing Signals 2113 The credit-windowing scheme introduces no additional DLEP signals. 2114 However, if a peer has advertised during session initialization that 2115 it supports the credit-windowing scheme then the following DLEP 2116 signals may contain additional credit-windowing data items: 2118 9.1.1. Destination Up Signal 2120 The Destination Up signal MAY contain one of each of the following 2121 data items: 2123 o Credit Grant (Section 9.2.2) 2125 9.1.2. Destination Up ACK Signal 2127 The Destination Up ACK signal MAY contain one of each of the 2128 following data items: 2130 o Credit Window Status (Section 9.2.1) 2132 9.1.3. Destination Update Signal 2134 The Destination Update signal MAY contain one of each of the 2135 following data items: 2137 o Credit Window Status (Section 9.2.1) 2139 o Credit Grant (Section 9.2.2) 2141 o Credit Request (Section 9.2.3) 2143 9.2. Credit-Windowing Data Items 2145 The credit-windowing scheme introduces 3 additional data items. If a 2146 peer has advertised during session initialization that it supports 2147 the credit-windowing scheme then it MUST correctly process the 2148 following data items without error. 2150 +------------+-----------------------+----------------+ 2151 | Data Item | Description | Section | 2152 +------------+-----------------------+----------------+ 2153 | TBD | Credit Window Status | Section 9.2.1 | 2154 | TBD | Credit Grant | Section 9.2.2 | 2155 | TBD | Credit Request | Section 9.2.3 | 2156 +------------+-----------------------+----------------+ 2158 9.2.1. Credit Window Status 2160 If the credit-window scheme is supported by the DLEP participants 2161 (both the router and the modem), the Credit Window Status data item 2162 MUST be sent by the participant receiving a Credit Grant for a given 2163 destination. 2165 The Credit Window Status data item contains the following fields: 2167 0 1 2 3 2168 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 2169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2170 | Data Item Type| Length = 16 | Modem Receive Window Value | 2171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2172 | Modem Receive Window Value | 2173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2174 | Modem Receive Window Value | Router Receive Window Value | 2175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2176 | Router Receive Window Value | 2177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2178 | Router Receive Window Value | 2179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2181 Data Item Type: TBD 2183 Length: 16 2185 Modem Receive Window Value: A 64-bit unsigned integer, indicating 2186 the current (or initial) number of credits available on the Modem 2187 Receive Window. 2189 Router Receive Window Value: A 64-bit unsigned integer, indicating 2190 the current (or initial) number of credits available on the Router 2191 Receive Window. 2193 9.2.2. Credit Grant 2195 The Credit Grant data item is sent from a DLEP participant to grant 2196 an increment to credits on a window. The Credit Grant data item MAY 2197 appear in the Destination Up (Section 7.9) or Destination Update 2198 (Section 7.13) signals. The value in a Credit Grant data item 2199 represents an increment to be added to any existing credits available 2200 on the window. Upon successful receipt and processing of a Credit 2201 Grant data item, the receiver MUST respond with a signal containing a 2202 Credit Window Status data item to report the updated aggregate values 2203 for synchronization purposes. 2205 In the Destination Up signal, when credits are desired, the 2206 originating peer MUST set the initial credit value of the window it 2207 controls (i.e., the Modem Receive Window, or Router Receive Window) 2208 to an initial, non-zero value. If the receiver of a Destination Up 2209 signal with a Credit Grant data item supports credits, the receiver 2210 MUST either reject the use of credits, via a Destination Up ACK 2211 response containing a Status data item (Section 8.2) with a status 2212 code of 'Request Denied', or set the initial value from the data 2213 contained in the Credit Window Status data item. If the 2214 initialization completes successfully, the receiver MUST respond to 2215 the Destination Up signal with a Destination Up ACK signal that 2216 contains a Credit Window Status data item, initializing its receive 2217 window. 2219 The Credit Grant data item contains the following fields: 2221 0 1 2 3 2222 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 2223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2224 | Data Item Type| Length = 8 | Credit Increment | 2225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2226 | Credit Increment | 2227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2228 | Credit Increment | 2229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2231 Data Item Type: TBD 2233 Length: 8 2235 Reserved: A 64-bit unsigned integer representing the additional 2236 credits to be assigned to the credit window. 2238 Since credits can only be granted by the receiver on a window, the 2239 applicable credit window (either the MRW or the RRW) is derived from 2240 the sender of the grant. The Credit Increment MUST NOT cause the 2241 window to overflow; if this condition occurs, implementations MUST 2242 set the credit window to the maximum value contained in a 64-bit 2243 quantity. 2245 9.2.3. Credit Request 2247 The Credit Request data item MAY be sent from either DLEP 2248 participant, via the Destination Update signal (Section 7.13), to 2249 indicate the desire for the partner to grant additional credits in 2250 order for data transfer to proceed on the session. If the 2251 corresponding Destination Up signal (Section 7.9) for this session 2252 did NOT contain a Credit Window Status data item, indicating that 2253 credits are to be used on the session, then the Credit Request data 2254 item MUST be rejected by the receiver via a Destination Update ACK 2255 signal containing a Status data item (Section 8.2) with status code 2256 'Request Denied'. 2258 The Credit Request data item contains the following fields: 2260 0 1 2 2261 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 2262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2263 | Data Item Type| Length = 1 | Reserved, MUST| 2264 | | | be set to 0 | 2265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2267 Data Item Type: TBD 2269 Length: 1 2271 Reserved: This field is currently unused and MUST be set to 0. 2273 10. Security Considerations 2275 The protocol does not contain any mechanisms for security (e.g., 2276 authentication or encryption). The protocol assumes that any 2277 security would be implemented in the underlying transport (for 2278 example, by use of DTLS or some other mechanism), and is therefore 2279 outside the scope of this document. 2281 11. IANA Considerations 2283 This section specifies requests to IANA. 2285 11.1. Registrations 2287 This specification defines: 2289 o A new repository for DLEP signals, with sixteen values currently 2290 assigned. 2292 o Reservation of numbering space for Experimental DLEP signals. 2294 o A new repository for DLEP data items, with twenty-three values 2295 currently assigned. 2297 o Reservation of numbering space in the data items repository for 2298 experimental data items. 2300 o A new repository for DLEP status codes. 2302 o A new repository for DLEP extensions, with one value currently 2303 assigned. 2305 o A request for allocation of a well-known port for DLEP 2306 communication. 2308 o A request for allocation of a multicast address for DLEP 2309 discovery. 2311 11.2. Expert Review: Evaluation Guidelines 2313 No additional guidelines for expert review are anticipated. 2315 11.3. Signal Type Registration 2317 A new repository must be created with the values of the DLEP signals. 2319 All signal values are in the range [0..255]. 2321 Valid signals are: 2323 o Peer Discovery 2325 o Peer Offer 2327 o Peer Initialization 2329 o Peer Initialization ACK 2331 o Peer Update 2333 o Peer Update ACK 2335 o Peer Termination 2337 o Peer Termination ACK 2339 o Destination Up 2341 o Destination Up ACK 2343 o Destination Down 2345 o Destination Down ACK 2347 o Destination Update 2349 o Heartbeat 2351 o Link Characteristics Request 2353 o Link Characteristics ACK 2354 It is also requested that the repository contain space for 2355 experimental signal types. 2357 11.4. DLEP Data Item Registrations 2359 A new repository for DLEP data items must be created. 2361 All data item values are in the range [0..255]. 2363 Valid data items are: 2365 o DLEP Version 2367 o Status 2369 o DLEP Port 2371 o Peer Type 2373 o Heartbeat Interval 2375 o Extensions Supported 2377 o Experimental Definition 2379 o MAC Address 2381 o IPv4 Address 2383 o IPv6 Address 2385 o IPv4 Attached Subnet 2387 o IPv6 Attached Subnet 2389 o Maximum Data Rate (Receive) 2391 o Maximum Data Rate (Transmit) 2393 o Current Data Rate (Receive) 2395 o Current Data Rate (Transmit) 2397 o Latency 2399 o Resources (Receive) 2401 o Resources (Transmit) 2402 o Relative Link Quality (Receive) 2404 o Relative Link Quality (Transmit) 2406 o Link Characteristics ACK Timer 2408 o Credit Window Status 2410 o Credit Grant 2412 o Credit Request 2414 It is also requested that the registry allocation contain space for 2415 experimental data items. 2417 11.5. DLEP Status Code Registrations 2419 A new repository for DLEP status codes must be created. 2421 All status codes are in the range [0..255]. 2423 Valid status codes are: 2425 o Success (value 0) 2427 o Unknown Signal 2429 o Invalid Signal 2431 o Unexpected Signal 2433 o Request Denied 2435 o Timed Out 2437 11.6. DLEP Extensions Registrations 2439 A new repository for DLEP extensions must be created. 2441 All extension values are in the range [0..255]. 2443 Valid extensions are: 2445 o DLEP_EXT_CREDITS - Credit windowing 2447 11.7. DLEP Well-known Port 2449 It is requested that IANA allocate a well-known port number for DLEP 2450 communication. 2452 11.8. DLEP Multicast Address 2454 It is requested that IANA allocate a multicast address for DLEP 2455 discovery signals. 2457 12. Acknowledgements 2459 The authors would like to acknowledge and thank the members of the 2460 DLEP design team, who have provided invaluable insight. The members 2461 of the design team are: Teco Boot, Bow-Nan Cheng, John Dowdell, and 2462 Henning Rogge. 2464 The authors would also like to acknowledge the influence and 2465 contributions of Greg Harrison, Chris Olsen, Martin Duke, Subir Das, 2466 Jaewon Kang, Vikram Kaul, and Nelson Powell. 2468 13. References 2470 13.1. Normative References 2472 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2473 Requirement Levels", BCP 14, RFC 2119, March 1997. 2475 [RFC5578] Berry, B., Ratliff, S., Paradise, E., Kaiser, T., and M. 2476 Adams, "PPP over Ethernet (PPPoE) Extensions for Credit 2477 Flow and Link Metrics", RFC 5578, February 2010. 2479 13.2. Informative References 2481 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 2482 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 2484 Appendix A. Peer Level Signal Flows 2486 _NB_ The following diagrams are possibly out of date. If there is a 2487 discepancy with the text, then the text is correct. 2489 A.1. Router Device Restarts Discovery 2490 Router Modem Signal Description 2491 ==================================================================== 2493 --------Peer Discovery--------> Router initiates discovery 2495 <--------Peer Offer------------ Modem detects a problem, sends 2496 w/ Non-zero Status TLV Peer Offer w/Status TLV indicating 2497 the error. 2499 Router accepts failure, restarts 2500 discovery process. 2502 --------Peer Discovery--------> Router initiates discovery 2504 <--------Peer Offer------------ Modem accepts, sends Peer Offer 2505 w/Zero Status TLV indicating 2506 success. 2508 Discovery completed. 2510 A.2. Router Device Detects Peer Offer Timeout 2512 Router Modem Signal Description 2513 ==================================================================== 2515 --------Peer Discovery--------> Router initiates discovery, starts 2516 a guard timer. 2518 Router guard timer expires. Router 2519 restarts discovery process. 2521 --------Peer Discovery--------> Router initiates discovery, starts 2522 a guard timer. 2524 <--------Peer Offer------------ Modem accepts, sends Peer Offer 2525 w/Zero Status TLV indicating 2526 success. 2528 Discovery completed. 2530 A.3. Router Peer Offer Lost 2531 Router Modem Signal Description 2532 ==================================================================== 2534 <-------Peer Discovery--------- Modem initiates discovery, starts 2535 a guard timer. 2537 ---------Peer Offer-------|| Router offers availability 2539 Modem times out on Peer Offer, 2540 restarts discovery process. 2542 <-------Peer Discovery--------- Modem initiates discovery 2544 ---------Peer Offer-----------> Router detects subsequent 2545 discovery, internally terminates 2546 the previous, accepts the new 2547 association, sends Peer Offer 2548 w/Status TLV indicating success. 2550 Discovery completed. 2552 A.4. Discovery Success 2554 Router Modem Signal Description 2555 ==================================================================== 2557 <-------Peer Discovery--------- Modem initiates discovery 2559 ---------Peer Offer-----------> Router offers availability 2561 <-----Peer Initialization------ Modem Connects on TCP Port 2563 <------Peer Heartbeat---------- 2565 -------Peer Heartbeat---------> 2567 <==============================> Signal flow about destinations 2568 (i.e. Destination Up, Destination 2569 Down, Destination update) 2571 <-------Peer Heartbeat--------- 2573 -------Peer Heartbeat---------> 2575 --------Peer Term Req---------> Terminate Request 2577 <--------Peer Term Res--------- Terminate Response 2579 A.5. Router Detects a Heartbeat timeout 2581 Router Modem Signal Description 2582 ==================================================================== 2584 <-------Peer Heartbeat--------- 2586 -------Peer Heartbeat---------> 2588 ||---Peer Heartbeat--------- 2590 ~ ~ ~ ~ ~ ~ ~ 2592 -------Peer Heartbeat---------> 2594 ||---Peer Heartbeat--------- 2595 Router Heartbeat Timer expires, 2596 detects missing heartbeats. Router 2597 takes down all destination 2598 sessions and terminates the Peer 2599 association. 2601 ------Peer Terminate ---------> Peer Terminate Request 2603 Modem takes down all destination 2604 sessions, then acknowledges the 2605 Peer Terminate 2607 <----Peer Terminate ACK--------- Peer Terminate ACK 2609 A.6. Modem Detects a Heartbeat timeout 2610 Router Modem Signal Description 2611 ==================================================================== 2613 <-------Peer Heartbeat--------- 2615 -------Peer Heartbeat------|| 2617 <-------Peer Heartbeat--------- 2619 ~ ~ ~ ~ ~ ~ ~ 2621 -------Peer Heartbeat------|| 2623 <-------Peer Heartbeat--------- 2624 Modem Heartbeat Timer expires, 2625 detects missing heartbeats. Modem 2626 takes down all destination 2627 sessions 2629 <-------Peer Terminate-------- Peer Terminate Request 2631 Router takes down all destination 2632 sessions, then acknowledges the 2633 Peer Terminate 2635 ------Peer Terminate ACK-----> Peer Terminate ACK 2637 A.7. Peer Terminate (from Modem) Lost 2639 Router Modem Signal Description 2640 ==================================================================== 2642 ||------Peer Terminate-------- Modem Peer Terminate Request 2644 Router Heartbeat times out, 2645 terminates association. 2647 --------Peer Terminate-------> Router Peer Terminate 2649 <-----Peer Terminate ACK------ Modem sends Peer Terminate ACK 2651 A.8. Peer Terminate (from Router) Lost 2652 Router Modem Signal Description 2653 ==================================================================== 2655 -------Peer Terminate--------> Router Peer Terminate Request 2657 Modem HB times out, 2658 terminates association. 2660 <------Peer Terminate-------- Modem Peer Terminate 2662 ------Peer Terminate ACK-----> Peer Terminate ACK 2664 Appendix B. Destination Specific Signal Flows 2666 B.1. Modem Destination Up Lost 2668 Router Modem Signal Description 2669 ==================================================================== 2671 ||-----Destination Up ------------ Modem sends Destination Up 2673 Modem timesout on ACK 2675 <------Destination Up ------------ Modem sends Destination Up 2677 ------Destination Up ACK---------> Router accepts the destination 2678 session 2680 <------Destination Update--------- Modem Destination Metrics 2681 . . . . . . . . 2682 <------Destination Update--------- Modem Destination Metrics 2684 B.2. Router Detects Duplicate Destination Ups 2685 Router Modem Signal Description 2686 ==================================================================== 2688 <------Destination Up ------------ Modem sends Destination Up 2690 ------Destination Up ACK-------|| Router accepts the destination 2691 session 2693 Modem timesout on ACK 2695 <------Destination Up ------------ Modem resends Destination Up 2697 Router detects duplicate 2698 Destination, takes down the 2699 previous, accepts the new 2700 Destination. 2702 ------Destination Up ACK---------> Router accepts the destination 2703 session 2705 <------Destination Update--------- Modem Destination Metrics 2706 . . . . . . . . 2707 <------Destination Update--------- Modem Destination Metrics 2709 B.3. Destination Up, No Layer 3 Addresses 2711 Router Modem Signal Description 2712 ==================================================================== 2714 <------Destination Up ------------ Modem sends Destination Up 2716 ------Destination Up ACK---------> Router accepts the destination 2717 session 2719 Router ARPs for IPv4 if defined. 2720 Router drives ND for IPv6 if 2721 defined. 2723 <------Destination Update--------- Modem Destination Metrics 2724 . . . . . . . . 2725 <------Destination Update--------- Modem Destination Metrics 2727 B.4. Destination Up with IPv4, No IPv6 2728 Router Modem Signal Description 2729 ==================================================================== 2731 <------Destination Up ------------ Modem sends Destination Up with 2732 the IPv4 TLV 2734 ------Destination Up ACK---------> Router accepts the destination 2735 session 2737 Router drives ND for IPv6 if 2738 defined. 2740 <------Destination Update--------- Modem Destination Metrics 2741 . . . . . . . . 2742 <------Destination Update--------- Modem Destination Metrics 2744 B.5. Destination Up with IPv4 and IPv6 2746 Router Modem Signal Description 2747 ==================================================================== 2749 <------Destination Up ------------ Modem sends Destination Up with 2750 the IPv4 and IPv6 TLVs 2752 ------Destination Up ACK---------> Router accepts the destination 2753 session 2755 <------Destination Update--------- Modem Destination Metrics 2756 . . . . . . . . 2758 B.6. Destination Session Success 2759 Router Modem Signal Description 2760 ==================================================================== 2762 ---------Peer Offer-----------> Router offers availability 2764 -------Peer Heartbeat---------> 2766 <------Destination Up ----------- Modem 2768 ------Destination Up ACK--------> Router 2770 <------Destination Update--------- Modem 2771 . . . . . . . . 2772 <------Destination Update--------- Modem 2774 Modem initiates the terminate 2776 <------Destination Down ---------- Modem 2778 ------Destination Down ACK-------> Router 2780 or 2782 Router initiates the terminate 2784 ------Destination Down ----------> Router 2786 <------Destination Down ACK------- Modem 2788 Authors' Addresses 2790 Stan Ratliff 2791 VT iDirect 2792 13861 Sunrise Valley Drive, Suite 300 2793 Herndon, VA 20171 2794 USA 2796 Email: sratliff@idirect.net 2798 Bo Berry 2799 Shawn Jury 2800 Cisco Systems 2801 170 West Tasman Drive 2802 San Jose, CA 95134 2803 USA 2805 Email: sjury@cisco.com 2807 Darryl Satterwhite 2808 Broadcom 2810 Email: dsatterw@broadcom.com 2812 Rick Taylor 2813 Airbus Defence & Space 2814 Quadrant House 2815 Celtic Springs 2816 Coedkernew 2817 Newport NP10 8FZ 2818 UK 2820 Email: rick.taylor@airbus.com