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Berger, Ed. 5 Expires: May 3, 2018 LabN Consulting, L.L.C. 6 October 30, 2017 8 DLEP Multi-Hop Forwarding Extension 9 draft-ietf-manet-dlep-multi-hop-extension-01 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 3, 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Extension Usage and Identification . . . . . . . . . . . . . 3 54 3. Extension Data Items . . . . . . . . . . . . . . . . . . . . 3 55 3.1. Hop Count . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3.2. Hop Control . . . . . . . . . . . . . . . . . . . . . . . 4 57 3.2.1. Reset . . . . . . . . . . . . . . . . . . . . . . . . 6 58 3.2.2. Terminate . . . . . . . . . . . . . . . . . . . . . . 6 59 3.2.3. Direct Connection . . . . . . . . . . . . . . . . . . 6 60 3.2.4. Suppress Forwarding . . . . . . . . . . . . . . . . . 6 61 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 63 5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 7 64 5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 7 65 5.3. Hop Control Actions Registry . . . . . . . . . . . . . . 8 66 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 6.1. Normative References . . . . . . . . . . . . . . . . . . 8 68 6.2. Informative References . . . . . . . . . . . . . . . . . 9 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 71 1. Introduction 73 The Dynamic Link Event Protocol (DLEP) is defined in [RFC8175]. It 74 provides the exchange of link related control information between 75 DLEP peers. DLEP peers are comprised of a modem and a router. DLEP 76 defines a base set of mechanisms as well as support for possible 77 extensions. This document defines one such extension. 79 Some modem technologies support connectivity to destinations via 80 multi-hop forwarding. DLEP Destination messages can be used to 81 report such connectivity, see [RFC8175], but do not provide any 82 information related to the number or capacity of the hops. The 83 extension defined in this document enables modems to inform routers 84 when multi-hop forwarding is being used, and routers to request that 85 modems change multi-hop forwarding behavior. The extension defined 86 in this document is referred to as "Multi-Hop Forwarding". 88 This document defines a new DLEP Extension Type Value in Section 2 89 which is used to indicate the use of the extension, and three new 90 DLEP Data Items in Section 3. 92 1.1. Key Words 94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 95 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 96 "OPTIONAL" in this document are to be interpreted as described in BCP 97 14 [RFC2119] [RFC8174] when, and only when, they appear in all 98 capitals, as shown here. 100 2. Extension Usage and Identification 102 The use of the Multi-Hop Forwarding Extension SHOULD be configurable. 103 To indicate that the extension is to be used, an implementation MUST 104 include the Multi-Hop Forwarding Extension Type Value in the 105 Extensions Supported Data Item. The Extensions Supported Data Item 106 is sent and processed according to [RFC8175]. 108 The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5. 110 3. Extension Data Items 112 Three data items are defined by this extension. The Hop Count Data 113 Item is used by a modem to provide the number of network hops 114 traversed to reach a particular destination. The Hop Control Data 115 Item is used by a router to request that a modem alter connectivity 116 to a particular destination. The Suppress Forwarding Data Item is 117 used by a router to request that a modem disable multi-hop forwarding 118 on either a device or destination basis. 120 3.1. Hop Count 122 The Hop Count Data Item is used by a modem to indicate the number of 123 physical hops between the modem and a specific destination. In other 124 words, each hop represents a transmission and the number of hops is 125 equal to the number of transmissions required to go from a router 126 connected modem to the destination's connected modem. The minimum 127 number of hops is 1, which represents the router's locally connected 128 modem. 130 The data item also contains an indication of when a destination which 131 currently has a hop count of greater than one (1) could be made 132 direcly reachable by a modem, e.g., by re-aiming an antenna. 134 The Hop Count Data Item SHOULD be carried in the Destination Up, 135 Destination Update, Destination Announce Response, and Link 136 Characteristics Response Messages when the Hop Count to a destination 137 is greater than one (1). 139 A router receiving a Hop Count Data Item MAY use this information in 140 its forwarding and routing decisions, and specific use is out of 141 scope of this document. The absence of the Hop Count Data Item MUST 142 be interpreted by the router as a Hop Count value of one (1). 144 The format of the Hop Count Data Item is: 146 0 1 2 3 147 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 1 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 149 | Data Item Type | Length | 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | Hop Count |P| Reserved | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 Data Item Type: TBA2 156 Length: 4 158 Hop Count: 160 An unsigned 8-bit integer indicating the number of network hops 161 required (i.e., number of times a packet will be transmitted) to 162 reach the destination indicated in the message. The special value 163 of 255 (0xFF) is used to indicate that the number of hops is an 164 unknown number greater than one (1). This field MUST contain a 165 value of at least one (1) if the associated destination is 166 reachable. 168 A value of zero (0) is used to indicated that processing of a Hop 169 Control action, see Section 3.2, has resulted in a destination no 170 longer being reachable. A zero value MUST NOT be used in any 171 message other then a Destination Announce Response Message. 173 P: 175 The P-bit indicates that a destination is potentially directly 176 reachable. When the P-bit is set, the router MAY request a direct 177 link to the associated destination using the Hop Control Data Item 178 described below. 180 Reserved: 182 MUST be set to zero by the sender (a modem) and ignored by the 183 receiver (a router). 185 3.2. Hop Control 187 The Hop Control Data Item is used by a router to request a change in 188 connectivity to a particular destination, or in multi-hop processing 189 on a device wide basis. A router can request multi-hop reachable 190 destination be changed to a single hop. A router can also indicate 191 that the modem terminate connectivity to a particular destination. 193 The Hop Control Data Item MAY be carried in the Session Update 194 Message or Destination Announce Message. 196 A router that receives the Hop Control in a Session Update Message 197 SHOULD attempt to make the change indicated by the data item for the 198 whole device. Results of any changes made are reflected in 199 Destination Down and Destination Update Messages. The modem MUST 200 notify the router of each destination that is no longer reachable via 201 a Destination Down Message. The modem MUST notify the router of any 202 changes in Hop Counts via Destination Update Messages. 204 A router that receives the Hop Control in a Destination Announce 205 Message SHOULD attempt to make the change indicated by the data item 206 for the associated destination MAC address. Once the change is made, 207 or fails or is rejected, the modem MUST respond with a Destination 208 Announce Response Message containing an updated Hop Count Data Item. 210 The format of the Hop Control Data Item is: 212 0 1 2 3 213 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 1 214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 | Data Item Type | Length | 216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 217 | Hop Control Actions | Reserved | 218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 Data Item Type: TBA3 222 Length: 4 224 Hop Control Actions: 226 An unsigned 16-bit value with the following meaning: 228 +-------+---------------------+ 229 | Value | Action | 230 +-------+---------------------+ 231 | 0 | Reset | 232 | | | 233 | 1 | Terminate | 234 | | | 235 | 2 | Direct Connection | 236 | | | 237 | 3 | Suppress Forwarding | 238 +-------+---------------------+ 240 Table 1: Hop Control Actions Values 242 3.2.1. Reset 244 The Reset Action requests that the default behavior be restored. 245 When received in a Session Update Message message, a modem SHOULD 246 clear all control actions that have previously been processed on a 247 device wide basis, and revert to its configured behavior. When 248 received in a Destination Announce Message, a modem SHOULD clear all 249 control actions that have previously been processed for the 250 destination indicated in the message. 252 3.2.2. Terminate 254 The Terminate Action is only valid on a per destination basis and 255 MUST NOT be sent in a Session Update Message message. It indicates 256 that the modem SHOULD attempt to terminate communication with the 257 destination identified in the message. This request has no impact 258 for multi-hop destinations and may fail even in a single hop case, 259 i.e. MAY result in the Hop Count to the destination not being 260 impacted by the processing of the request 262 3.2.3. Direct Connection 264 The Direct Connection is only valid on a per destination basis and 265 MUST NOT be sent in a Session Update Message message. It indicates 266 that the modem SHOULD attempt to establish a direct connection with 267 the destination identified in the message. This action SHOULD only 268 be sent for destinations for which the Hop Count is greater than 1 269 and has the P-Bit set in the previously received Hop Count Data Item. 270 Results of the request for the destination identified in the message 271 are provided as described above. If any other destination is 272 impacted in the processing of this action, the modem MUST send a 273 Destination Update Message for each impacted destination. 275 3.2.4. Suppress Forwarding 277 The Suppress Forwarding Action is used by a router to indicate to its 278 peer that multi-hop forwarding is to be suppressed. A router may 279 request that multi-hop forwarding may be suppressed on a device wide 280 or destination specific basis. 282 A modem which receives the Suppress Forwarding Data Item in a Session 283 Update Message MUST suppress multi-hop forwarding on a device wide 284 basis. Impact to destination hop counts are provided to the router 285 by the modem as described above. 287 A modem which receives the Suppress Forwarding Data Item in a 288 Destination Announce Message MUST suppress multi-hop forwarding for 289 only the destination indicated in the message. Results are provided 290 as described above. 292 4. Security Considerations 294 The extension enables the reporting and control of forwarding 295 information by DLEP capable modems. The extension does not 296 inherently introduce any additional threats above those documented in 297 [RFC8175]. The approach taken to Security in that document applies 298 equally when running the extension defined in this document. 300 5. IANA Considerations 302 This document requests the assignment of 3 values by IANA. All 303 assignments are to registries defined by [RFC8175]. It also requests 304 creation of one new registry. 306 5.1. Extension Type Value 308 This document requests 1 new assignment to the DLEP Extensions 309 Registry named "Extension Type Values" in the range with the 310 "Specification Required" policy. The requested value is as follows: 312 +------+----------------------+ 313 | Code | Description | 314 +------+----------------------+ 315 | TBA1 | Multi-Hop Forwarding | 316 +------+----------------------+ 318 Table 2: Requested Extension Type Value 320 5.2. Data Item Values 322 This document requests 2 new assignments to the DLEP Data Item 323 Registry named "Data Item Values" in the range with the 324 "Specification Required" policy. The requested values are as 325 follows: 327 +-----------+-------------+ 328 | Type Code | Description | 329 +-----------+-------------+ 330 | TBA2 | Hop Count | 331 | | | 332 | TBA3 | Hop Control | 333 +-----------+-------------+ 335 Table 3: Requested Data Item Values 337 5.3. Hop Control Actions Registry 339 Upon approval of this document, IANA is requested to create a new 340 DLEP registry, named "Hop Control Actions Values". The following 341 table provides initial registry values and the [RFC8126]. defined 342 policies that should apply to the registry: 344 +-------------+------------------------+ 345 | Value | Action/Policy | 346 +-------------+------------------------+ 347 | 0 | Reset | 348 | | | 349 | 1 | Terminate | 350 | | | 351 | 2 | Direct Connection | 352 | | | 353 | 3 | Suppress Forwarding | 354 | | | 355 | 4-65519 | Specification Required | 356 | | | 357 | 65520-65534 | Private Use | 358 | | | 359 | 65535 | Reserved | 360 +-------------+------------------------+ 362 Table 4: Hop Control Actions Values 364 6. References 366 6.1. Normative References 368 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 369 Requirement Levels", BCP 14, RFC 2119, 370 DOI 10.17487/RFC2119, March 1997, 371 . 373 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 374 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 375 May 2017, . 377 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 378 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 379 DOI 10.17487/RFC8175, June 2017, 380 . 382 6.2. Informative References 384 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 385 Writing an IANA Considerations Section in RFCs", BCP 26, 386 RFC 8126, DOI 10.17487/RFC8126, June 2017, 387 . 389 Authors' Addresses 391 Bow-Nan Cheng 392 Lincoln Laboratory 393 Massachusetts Institute of Technology 394 244 Wood Street 395 Lexington, MA 02421-6426 397 Email: bcheng@ll.mit.edu 399 Lou Berger (editor) 400 LabN Consulting, L.L.C. 402 Email: lberger@labn.net