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Berger, Ed. 5 Expires: May 15, 2018 LabN Consulting, L.L.C. 6 November 11, 2017 8 DLEP Multi-Hop Forwarding Extension 9 draft-ietf-manet-dlep-multi-hop-extension-02 11 Abstract 13 This document defines an extension to the DLEP protocol that enables 14 the reporting and control of Multi-Hop Forwarding by DLEP capable 15 modems. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on May 15, 2018. 34 Copyright Notice 36 Copyright (c) 2017 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. Extension Usage and Identification . . . . . . . . . . . . . 3 54 3. Extension Data Items . . . . . . . . . . . . . . . . . . . . 3 55 3.1. Hop Count . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3.2. Hop Control . . . . . . . . . . . . . . . . . . . . . . . 5 57 3.2.1. Reset . . . . . . . . . . . . . . . . . . . . . . . . 6 58 3.2.2. Terminate . . . . . . . . . . . . . . . . . . . . . . 6 59 3.2.3. Direct Connection . . . . . . . . . . . . . . . . . . 7 60 3.2.4. Suppress Forwarding . . . . . . . . . . . . . . . . . 7 61 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 63 5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 8 64 5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 8 65 5.3. Hop Control Actions Registry . . . . . . . . . . . . . . 8 66 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 67 6.1. Normative References . . . . . . . . . . . . . . . . . . 9 68 6.2. Informative References . . . . . . . . . . . . . . . . . 9 69 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 9 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 72 1. Introduction 74 The Dynamic Link Event Protocol (DLEP) is defined in [RFC8175]. It 75 provides the exchange of link related control information between 76 DLEP peers. DLEP peers are comprised of a modem and a router. DLEP 77 defines a base set of mechanisms as well as support for possible 78 extensions. This document defines one such extension. 80 Some modem technologies support connectivity to destinations via 81 multi-hop forwarding. DLEP Destination messages can be used to 82 report such connectivity, see [RFC8175], but do not provide any 83 information related to the number or capacity of the hops. The 84 extension defined in this document enables modems to inform routers 85 when multi-hop forwarding is being used, and routers to request that 86 modems change multi-hop forwarding behavior. The extension defined 87 in this document is referred to as "Multi-Hop Forwarding". 89 This document defines a new DLEP Extension Type Value in Section 2 90 which is used to indicate the use of the extension, and three new 91 DLEP Data Items in Section 3. 93 1.1. Key Words 95 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 96 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 97 "OPTIONAL" in this document are to be interpreted as described in BCP 98 14 [RFC2119] [RFC8174] when, and only when, they appear in all 99 capitals, as shown here. 101 2. Extension Usage and Identification 103 The use of the Multi-Hop Forwarding Extension SHOULD be configurable. 104 To indicate that the extension is to be used, an implementation MUST 105 include the Multi-Hop Forwarding Extension Type Value in the 106 Extensions Supported Data Item. The Extensions Supported Data Item 107 is sent and processed according to [RFC8175]. 109 The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5. 111 3. Extension Data Items 113 Three data items are defined by this extension. The Hop Count Data 114 Item is used by a modem to provide the number of network hops 115 traversed to reach a particular destination. The Hop Control Data 116 Item is used by a router to request that a modem alter connectivity 117 to a particular destination. The Suppress Forwarding Data Item is 118 used by a router to request that a modem disable multi-hop forwarding 119 on either a device or destination basis. 121 3.1. Hop Count 123 The Hop Count Data Item is used by a modem to indicate the number of 124 physical hops between the modem and a specific destination. In other 125 words, each hop represents a transmission and the number of hops is 126 equal to the number of transmissions required to go from a router 127 connected modem to the destination's connected modem. The minimum 128 number of hops is 1, which represents the router's locally connected 129 modem. 131 The data item also contains an indication of when a destination which 132 currently has a hop count of greater than one (1) could be made 133 direcly reachable by a modem, e.g., by re-aiming an antenna. 135 The Hop Count Data Item SHOULD be carried in the Destination Up, 136 Destination Update, Destination Announce Response, and Link 137 Characteristics Response Messages when the Hop Count to a destination 138 is greater than one (1). 140 A router receiving a Hop Count Data Item MAY use this information in 141 its forwarding and routing decisions, and specific use is out of 142 scope of this document. The absence of the Hop Count Data Item MUST 143 be interpreted by the router as a Hop Count value of one (1). 145 The format of the Hop Count Data Item is: 147 0 1 2 3 148 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 1 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | Data Item Type | Length | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Hop Count |P| Reserved | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 Data Item Type: TBA2 157 Length: 4 159 Hop Count: 161 An unsigned 8-bit integer indicating the number of network hops 162 required (i.e., number of times a packet will be transmitted) to 163 reach the destination indicated in the message. The special value 164 of 255 (0xFF) is used to indicate that the number of hops is an 165 unknown number greater than one (1). This field MUST contain a 166 value of at least one (1) if the associated destination is 167 reachable. 169 A value of zero (0) is used to indicated that processing of a Hop 170 Control action, see Section 3.2, has resulted in a destination no 171 longer being reachable. A zero value MUST NOT be used in any 172 message other then a Destination Announce Response Message. 174 P: 176 The P-bit indicates that a destination is potentially directly 177 reachable. When the P-bit is set, the router MAY request a direct 178 link to the associated destination using the Hop Control Data Item 179 described below. 181 Reserved: 183 MUST be set to zero by the sender (a modem) and ignored by the 184 receiver (a router). 186 3.2. Hop Control 188 The Hop Control Data Item is used by a router to request a change in 189 connectivity to a particular destination, or in multi-hop processing 190 on a device wide basis. A router can request multi-hop reachable 191 destination be changed to a single hop. A router can also indicate 192 that the modem terminate connectivity to a particular destination. 194 The Hop Control Data Item MAY be carried in a Session Update Message 195 when the control applies to the whole device, or a Link 196 Characteristics Request Message when the control applies to a 197 particular destination. 199 A router that receives the Hop Control in a Session Update Message 200 SHOULD attempt to make the change indicated by the data item for the 201 whole device. Results of any changes made are reflected in 202 Destination Down and Destination Update Messages. The modem MUST 203 notify the router of each destination that is no longer reachable via 204 a Destination Down Message. The modem MUST notify the router of any 205 changes in Hop Counts via Destination Update Messages. 207 A modem that receives the Hop Control Data Item in a Link 208 Characteristics Request Message SHOULD attempt to make the change 209 indicated by the data item for the associated destination MAC 210 address. Once the change is made, or fails or is rejected, the modem 211 MUST respond with a Link Characteristics Request Message containing 212 an updated Hop Count Data Item. Note that other destinations can be 213 impacted as a result of the change and such changes are reported in 214 Destination Down and Destination Update Messages. The modem MUST 215 notify the router of each destination that is no longer reachable via 216 a Destination Down Message. The modem MUST notify the router of any 217 changes in Hop Counts via Destination Update Messages. 219 A modem that receives the Hop Control Data Item in a Session Update 220 Message SHOULD attempt to make the change indicated by the data item 221 for the associated destination MAC address, when carried in a Link 222 Characteristics Request Message, or all destinations, when carried in 223 a Session Update Message. Once the change is made, or fails or is 224 rejected, the modem MUST respond with a Link Characteristics Request 225 Message containing an updated Hop Count Data Item. Note that other 226 destinations can be impacted as a result of the change and such 227 changes are reported in Destination Down and Destination Update 228 Messages. The modem MUST notify the router of each destination that 229 is no longer reachable via a Destination Down Message. The modem 230 MUST notify the router of any changes in Hop Counts via Destination 231 Update Messages. 233 The format of the Hop Control Data Item is: 235 0 1 2 3 236 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 1 237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 238 | Data Item Type | Length | 239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 240 | Hop Control Actions | Reserved | 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 Data Item Type: TBA3 245 Length: 4 247 Hop Control Actions: 249 An unsigned 16-bit value with the following meaning: 251 +-------+---------------------+ 252 | Value | Action | 253 +-------+---------------------+ 254 | 0 | Reset | 255 | | | 256 | 1 | Terminate | 257 | | | 258 | 2 | Direct Connection | 259 | | | 260 | 3 | Suppress Forwarding | 261 +-------+---------------------+ 263 Table 1: Hop Control Actions Values 265 3.2.1. Reset 267 The Reset Action requests that the default behavior be restored. 268 When received in a Session Update Message message, a modem SHOULD 269 clear all control actions that have previously been processed on a 270 device wide basis, and revert to its configured behavior. When 271 received in a Link Characteristics Request Message, a modem SHOULD 272 clear all control actions that have previously been processed for the 273 destination indicated in the message. 275 3.2.2. Terminate 277 The Terminate Action is only valid on a per destination basis and 278 MUST NOT be sent in a Session Update Message message. It indicates 279 that the modem SHOULD attempt to terminate communication with the 280 destination identified in the message. This request has no impact 281 for multi-hop destinations and may fail even in a single hop case, 282 i.e. MAY result in the Hop Count to the destination not being 283 impacted by the processing of the request 285 3.2.3. Direct Connection 287 The Direct Connection is only valid on a per destination basis and 288 MUST NOT be sent in a Session Update Message message. It indicates 289 that the modem SHOULD attempt to establish a direct connection with 290 the destination identified in the message. This action SHOULD only 291 be sent for destinations for which the Hop Count is greater than 1 292 and has the P-Bit set in the previously received Hop Count Data Item. 293 Results of the request for the destination identified in the message 294 are provided as described above. If any other destination is 295 impacted in the processing of this action, the modem MUST send a 296 Destination Update Message for each impacted destination. 298 3.2.4. Suppress Forwarding 300 The Suppress Forwarding Action is used by a router to indicate to its 301 peer that multi-hop forwarding is to be suppressed. A router may 302 request that multi-hop forwarding may be suppressed on a device wide 303 or destination specific basis. 305 A modem which receives the Suppress Forwarding Data Item in a Session 306 Update Message MUST suppress multi-hop forwarding on a device wide 307 basis. Impact to destination hop counts are provided to the router 308 by the modem as described above. 310 A modem which receives the Suppress Forwarding Data Item in a Link 311 Characteristics Request Message MUST suppress multi-hop forwarding 312 for only the destination indicated in the message. Results are 313 provided as described above. 315 4. Security Considerations 317 The extension enables the reporting and control of forwarding 318 information by DLEP capable modems. The extension does not 319 inherently introduce any additional threats above those documented in 320 [RFC8175]. The approach taken to Security in that document applies 321 equally when running the extension defined in this document. 323 5. IANA Considerations 325 This document requests the assignment of 3 values by IANA. All 326 assignments are to registries defined by [RFC8175]. It also requests 327 creation of one new registry. 329 5.1. Extension Type Value 331 This document requests 1 new assignment to the DLEP Extensions 332 Registry named "Extension Type Values" in the range with the 333 "Specification Required" policy. The requested value is as follows: 335 +------+----------------------+ 336 | Code | Description | 337 +------+----------------------+ 338 | TBA1 | Multi-Hop Forwarding | 339 +------+----------------------+ 341 Table 2: Requested Extension Type Value 343 5.2. Data Item Values 345 This document requests 2 new assignments to the DLEP Data Item 346 Registry named "Data Item Values" in the range with the 347 "Specification Required" policy. The requested values are as 348 follows: 350 +-----------+-------------+ 351 | Type Code | Description | 352 +-----------+-------------+ 353 | TBA2 | Hop Count | 354 | | | 355 | TBA3 | Hop Control | 356 +-----------+-------------+ 358 Table 3: Requested Data Item Values 360 5.3. Hop Control Actions Registry 362 Upon approval of this document, IANA is requested to create a new 363 DLEP registry, named "Hop Control Actions Values". The following 364 table provides initial registry values and the [RFC8126]. defined 365 policies that should apply to the registry: 367 +-------------+------------------------+ 368 | Value | Action/Policy | 369 +-------------+------------------------+ 370 | 0 | Reset | 371 | | | 372 | 1 | Terminate | 373 | | | 374 | 2 | Direct Connection | 375 | | | 376 | 3 | Suppress Forwarding | 377 | | | 378 | 4-65519 | Specification Required | 379 | | | 380 | 65520-65534 | Private Use | 381 | | | 382 | 65535 | Reserved | 383 +-------------+------------------------+ 385 Table 4: Hop Control Actions Values 387 6. References 389 6.1. Normative References 391 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 392 Requirement Levels", BCP 14, RFC 2119, 393 DOI 10.17487/RFC2119, March 1997, 394 . 396 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 397 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 398 May 2017, . 400 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 401 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 402 DOI 10.17487/RFC8175, June 2017, 403 . 405 6.2. Informative References 407 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 408 Writing an IANA Considerations Section in RFCs", BCP 26, 409 RFC 8126, DOI 10.17487/RFC8126, June 2017, 410 . 412 Appendix A. Acknowledgments 414 Henning Rogge provided valuable input to this work. 416 Authors' Addresses 418 Bow-Nan Cheng 419 Lincoln Laboratory 420 Massachusetts Institute of Technology 421 244 Wood Street 422 Lexington, MA 02421-6426 424 Email: bcheng@ll.mit.edu 426 Lou Berger (editor) 427 LabN Consulting, L.L.C. 429 Email: lberger@labn.net