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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Mobile Ad hoc Networks Working Group R. Taylor 3 Internet-Draft Airbus Defence & Space 4 Intended status: Standards Track S. Ratliff 5 Expires: August 3, 2018 VT iDirect 6 January 30, 2018 8 Link Identifier Extension to DLEP 9 draft-ietf-manet-dlep-lid-extension-01 11 Abstract 13 There exists a class of modems that wish to support the Dynamic Link 14 Exchange Protocol (DLEP) [RFC8175] but do not present a single Layer 15 2 network domain as required by DLEP. Such devices may be: 17 o Modems that maintain a varying link to some upstream backbone 18 network infrastructure, where the ability to announce link state 19 and DLEP metrics is desired, but the concept of a DLEP destination 20 router for the backbone does not apply. Examples of such devices 21 can include LTE modems, IEEE 802.11 stations not in ad-hoc mode, 22 and some satellite terminals. 24 o Modems that provide Layer 3 wide area network connectivity between 25 devices, where individual DLEP destinations do exist, but are not 26 directly reachable by MAC address. 28 This document introduces an optional extension to the core DLEP 29 specification, allowing DLEP to be used between routers and modems 30 that operate in this way. 32 Note: 34 o This document is intended as an extension to the core DLEP 35 specification, and readers are expected to be fully conversant 36 with the operation of core DLEP. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at http://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on August 3, 2018. 55 Copyright Notice 57 Copyright (c) 2018 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 73 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3 74 2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 4 76 2.2. Negotiation . . . . . . . . . . . . . . . . . . . . . . . 4 77 3. New Data Items . . . . . . . . . . . . . . . . . . . . . . . 5 78 3.1. Link Identifier Length Data Item . . . . . . . . . . . . 5 79 3.2. Link Identifier Data Item . . . . . . . . . . . . . . . . 6 80 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 81 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 82 5.1. DLEP Link Identifier Flag . . . . . . . . . . . . . . . . 7 83 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 84 6.1. Normative References . . . . . . . . . . . . . . . . . . 7 85 6.2. Informative References . . . . . . . . . . . . . . . . . 7 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 88 1. Introduction 90 The Dynamic Link Exchange Protocol (DLEP) [RFC8175] describes a 91 protocol for modems to advertise the status of wireless links between 92 reachable destinations to attached routers. The core specification 93 of the protocol assumes that every modem in the radio network has an 94 attached DLEP router, and requires that the MAC address of the DLEP 95 interface on the attached router is used to identify the destination 96 in the network for purposes of reporting the state and quality of the 97 link to that destination. 99 This document describes a DLEP Extension allowing modems that do not 100 meet the strict requirement that DLEP must be implemented on a single 101 Layer 2 domain to use DLEP to describe link availability and quality 102 to one or more destinations reachable beyond a local or remote device 103 on the Layer 2 domain. A router can use this knowledge to influence 104 any routing or flow-control decisions regarding traffic to this 105 destination, understanding that such traffic flows via Layer 3. 107 A Layer 3 destination may be an attached DLEP router, in the case of 108 a modem that provides Layer 3 wide area network connectivity between 109 devices, or a logical destination that describes a set of attached 110 subnets, when referring to some upstream backbone network 111 infrastructure. 113 1.1. Requirements 115 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 116 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 117 document are to be interpreted as described in BCP 14, RFC 2119. 119 2. Operation 121 To refer to a Layer 3 DLEP Destination, the DLEP session participant 122 adds a Link Identifier Data Item (Section 3.2) to the relevant 123 Destination Message, and (as usual) includes a MAC Address Data Item. 124 When paired with a Link Identifier Data Item, the MAC Address Data 125 Item MUST contain the MAC address of the last reachable node in the 126 Layer 2 domain beyond which the Layer 3 DLEP Destination resides. 127 For example, if the over-the-air network is not a single Layer 2 128 domain, the MAC Address Data Item might be the address of the LAN- 129 side interface of the local modem. Alternatively, when used with 130 some kind of backbone infrastructure, the MAC Address Data Item would 131 be the address of the last device reachable on the local Layer 2 132 domain. However, how such remote destinations are discovered is 133 beyond the scope of this specification. 135 As only modems are initially aware of Layer 3 DLEP Destinations, Link 136 Identifier Data Items referring to a new link MUST first appear in a 137 DLEP Destination Up Message from the modem to the router. Once a 138 link has been identified in this way, Link Identifier Data Items MAY 139 be used by either DLEP participant during the lifetime of a DLEP 140 session. Because of this, a router MUST NOT send a DLEP Destination 141 Announce Message containing a Link Identifier Data Item referring to 142 a link that has not been mentioned in a prior DLEP Destination Up 143 Message. 145 Because the MAC Address associated with any DLEP Destination Message 146 containing a Link Identifier Data Item is not the Layer 2 address of 147 the destination, all DLEP Destination Up Messages MUST contain Layer 148 3 information. In the case of modems that provide Layer 3 wide area 149 network connectivity between devices, this means one or more IPv4 or 150 IPv6 Address Data Items providing the Layer 3 address of the 151 destination. When referring to some upstream backbone network 152 infrastructure, this means one or more IPv4 or IPv6 Attached Subnet 153 Data Items, for example: '0.0.0.0/0' or '::/0'. This allows the DLEP 154 peer router to understand the properties of the link to those routes. 156 When the DLEP peer router wishes to forward packets to the Layer 3 157 destination or subnet, the MAC address associated with the link MUST 158 be used as the Layer 2 destination of the packet. 160 2.1. Identifier Restrictions 162 A link identifier is by default 4 octets in length. If a modem 163 wishes to use an identifier of a different length, it MUST be 164 announced using the Link Identifier Length Data Item (Section 3.1) 165 contained in the DLEP Session Initialization Response message sent by 166 the modem to the router. 168 During the lifetime of a DLEP session, the length of link identifiers 169 MUST remain constant, i.e. the Length field of the Link Identifier 170 Data Item must not alter between destinations. 172 The method for generating identifiers is a modem implementation 173 matter and out of scope of this document. Routers MUST NOT make any 174 assumptions about the meaning of identifiers, or how identifiers are 175 generated. 177 Within a single DLEP session, all link identifiers MUST be unique per 178 MAC Address. This means that a Layer 3 DLEP Destination is uniquely 179 identified by the pair: {MAC Address,Link Id}. 181 Identifiers MUST NOT be reused, i.e. a {MAC Address,Link Id} pair 182 that has been used to refer to one destination MUST NOT be recycled 183 to refer to a different destination within the lifetime of a single 184 DLEP session. 186 2.2. Negotiation 188 To use this extension, as with all DLEP extensions, the extension 189 MUST be announced during DLEP session initialization. A router 190 advertises support by including the value 'Link Identifiers' (TBD1), 191 Section 5, in the Extension Data Item within the Session 192 Initialization Message. A modem advertises support by including the 193 value 'Link Identifiers' (TBD1) in the Extension Data Item within the 194 Session Initialization Response Message. If both DLEP peers 195 advertise support for this extension then the Link Identifier Data 196 Item MAY be used. 198 If a modem requires support for this extension in order to describe 199 destinations, and the router does not advertise support, then the 200 modem MUST NOT include a Link Identifier Data Item in any DLEP 201 Message. However, the modem SHOULD NOT immediately terminate the 202 DLEP session, rather it SHOULD use session-wide DLEP Data Items to 203 announce general information about all reachable destinations via the 204 modem. By doing this, a modem allows a router not supporting this 205 extension to at least make a best guess at the state of any reachable 206 network. A modem MUST NOT attempt to re-use the MAC Address Data 207 Item to perform some kind of sleight-of-hand, assuming that the 208 router will notice the DLEP Peer Type of the modem is special in some 209 way. 211 3. New Data Items 213 This extension introduces two new DLEP Data Items: the Link 214 Identifier Data Item (Section 3.2) used to identify a Layer 3 link at 215 or beyond a destination, and the Link Identifier Length Data Item 216 (Section 3.1) used to announce the length of Link Identifiers at 217 session initialization. 219 3.1. Link Identifier Length Data Item 221 The Link Identifier Length Data Item MAY be used by a DLEP modem 222 implementation to define the length of Link Identifier Data Items if 223 it does not with to use the default value of 4 octets. 225 The Link Identifier Length Data Item MAY be used during Session 226 Initialization, contained in a Session Initialization Response 227 Message. 229 0 1 2 3 230 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 1 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | Data Item Type | Length | 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | Link Identifier Length | 235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 Data Item Type: TBD2, Section 5 239 Length: 2 240 Link Identifier Length: The length, in octets, of Link Identifiers 241 used by the DLEP modem for this session. 243 3.2. Link Identifier Data Item 245 The Link Identifier Data Item MAY be used wherever a MAC Address Data 246 Item is defined as usable in core DLEP. 248 0 1 2 3 249 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 1 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 | Data Item Type | Length | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | Flags | Link Identifier... : 254 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 Data Item Type: TBD3, Section 5 258 Length: The length of the Data Item, by default 5, but may be 259 different if a Link Identifier Length Data Item (Section 3.1) has 260 been announced during session initialization. 262 Flags: Flags field, defined below. 264 Link Identifier: The unique identifier of the Layer 3 destination. 265 This identifier has no implicit meaning and is only used to 266 discriminate between multiple links. 268 The Flags field is defined as: 270 0 1 2 3 4 5 6 7 271 +-+-+-+-+-+-+-+-+ 272 | Reserved | 273 +-+-+-+-+-+-+-+-+ 275 Reserved: MUST be zero. Left for future assignment. 277 4. Security Considerations 279 As an extension to the core DLEP protocol, the security 280 considerations of that protocol apply to this extension. This 281 extension adds no additional security mechanisms or features. 283 None of the features introduced by this extension require extra 284 consideration by an implementation. 286 5. IANA Considerations 288 Upon approval of this document, IANA is requested to: 290 o Assign a new value (TBD1) from the Specification Required section 291 of the DLEP Extensions Registry, named "Link Identifiers". 293 o Assign a new value (TBD2) from the Specification Required section 294 of the DLEP Data Item Type Values Registry, named "Link Identifier 295 Length". 297 o Assign a new value (TBD3) from the Specification Required section 298 of the DLEP Data Item Type Values Registry, named "Link 299 Identifier". 301 5.1. DLEP Link Identifier Flag 303 Upon approval of this document, IANA is requested to create a new 304 DLEP registry, named "Link Identifier Flags". 306 The following table provides initial registry values and the RFC 5226 307 defined policies that should apply to the registry: 309 +------------+------------------------------------+ 310 | Bit | Description/Policy | 311 +------------+------------------------------------+ 312 | 0-7 | Unassigned/Specification Required | 313 +------------+------------------------------------+ 315 6. References 317 6.1. Normative References 319 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 320 Requirement Levels", BCP 14, RFC 2119, 321 DOI 10.17487/RFC2119, March 1997, . 324 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 325 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 326 DOI 10.17487/RFC8175, June 2017, . 329 6.2. Informative References 331 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 332 IANA Considerations Section in RFCs", RFC 5226, 333 DOI 10.17487/RFC5226, May 2008, . 336 Authors' Addresses 338 Rick Taylor 339 Airbus Defence & Space 340 Quadrant House 341 Celtic Springs 342 Coedkernew 343 Newport NP10 8FZ 344 UK 346 Email: rick.taylor@airbus.com 348 Stan Ratliff 349 VT iDirect 350 13861 Sunrise Valley Drive, Suite 300 351 Herndon, VA 20171 352 USA 354 Email: sratliff@idirect.net