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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: February 24, 2019 VT iDirect 6 August 23, 2018 8 DLEP Link Identifier Extension 9 draft-ietf-manet-dlep-lid-extension-04 11 Abstract 13 There exists a class of modems that would benefit from supporting the 14 Dynamic Link Exchange Protocol (DLEP) [RFC8175] but do not present a 15 single Layer 2 network domain as required by DLEP. Such devices may 16 be: 18 o Modems that maintain a varying link to some upstream backbone 19 network infrastructure, where the ability to announce link state 20 and DLEP metrics is desired, but the concept of a DLEP destination 21 router for the backbone does not apply. Examples of such devices 22 can include LTE modems, IEEE 802.11 stations not in ad-hoc mode, 23 and some satellite terminals. 25 o Modems that provide Layer 3 wide area network connectivity between 26 devices, where remote DLEP destinations do exist, but are not 27 directly reachable by MAC address, such as modems that contain 28 embedded routing functionality. 30 This document introduces an optional extension to the core DLEP 31 specification, allowing DLEP to be used between routers and modems 32 that operate in this way. 34 Note: 36 o This document is intended as an extension to the core DLEP 37 specification, and readers are expected to be fully conversant 38 with the operation of core DLEP. 40 Status of This Memo 42 This Internet-Draft is submitted in full conformance with the 43 provisions of BCP 78 and BCP 79. 45 Internet-Drafts are working documents of the Internet Engineering 46 Task Force (IETF). Note that other groups may also distribute 47 working documents as Internet-Drafts. The list of current Internet- 48 Drafts is at https://datatracker.ietf.org/drafts/current/. 50 Internet-Drafts are draft documents valid for a maximum of six months 51 and may be updated, replaced, or obsoleted by other documents at any 52 time. It is inappropriate to use Internet-Drafts as reference 53 material or to cite them other than as "work in progress." 55 This Internet-Draft will expire on February 24, 2019. 57 Copyright Notice 59 Copyright (c) 2018 IETF Trust and the persons identified as the 60 document authors. All rights reserved. 62 This document is subject to BCP 78 and the IETF Trust's Legal 63 Provisions Relating to IETF Documents 64 (https://trustee.ietf.org/license-info) in effect on the date of 65 publication of this document. Please review these documents 66 carefully, as they describe your rights and restrictions with respect 67 to this document. Code Components extracted from this document must 68 include Simplified BSD License text as described in Section 4.e of 69 the Trust Legal Provisions and are provided without warranty as 70 described in the Simplified BSD License. 72 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 75 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3 76 2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 77 2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 4 78 2.2. Negotiation . . . . . . . . . . . . . . . . . . . . . . . 5 79 3. New Data Items . . . . . . . . . . . . . . . . . . . . . . . 5 80 3.1. Link Identifier Length Data Item . . . . . . . . . . . . 5 81 3.2. Link Identifier Data Item . . . . . . . . . . . . . . . . 6 82 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 83 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 84 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 85 6.1. Normative References . . . . . . . . . . . . . . . . . . 7 86 6.2. Informative References . . . . . . . . . . . . . . . . . 7 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 89 1. Introduction 91 The Dynamic Link Exchange Protocol (DLEP) [RFC8175] describes a 92 protocol for modems to advertise the status of wireless links between 93 reachable destinations to attached routers. The core specification 94 of the protocol assumes that every modem in the radio network has an 95 attached DLEP router, and requires that the MAC address of the DLEP 96 interface on the attached router is used to identify the destination 97 in the network for purposes of reporting the state and quality of the 98 link to that destination. 100 This document describes a DLEP Extension allowing modems that do not 101 meet the strict requirement that DLEP must be implemented on a single 102 Layer 2 domain to use DLEP to describe link availability and quality 103 to one or more destinations reachable beyond a local or remote device 104 on the Layer 2 domain. A router can use this knowledge to influence 105 any routing or flow-control decisions regarding traffic to this 106 destination, understanding that such traffic flows via Layer 3. 108 A Layer 3 destination may be an attached DLEP router, in the case of 109 a modem that provides Layer 3 wide area network connectivity between 110 devices, or a logical destination that describes a set of attached 111 subnets, when referring to some upstream backbone network 112 infrastructure. 114 1.1. Requirements 116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 118 document are to be interpreted as described in BCP 14, RFC 2119. 120 2. Operation 122 To refer to a Layer 3 DLEP Destination, the DLEP session participant 123 adds a Link Identifier Data Item (Section 3.2) to the relevant 124 Destination Message, and (as usual) includes a MAC Address Data Item. 125 When paired with a Link Identifier Data Item, the MAC Address Data 126 Item MUST contain the MAC address of the last reachable node in the 127 Layer 2 domain beyond which the Layer 3 DLEP Destination resides. 128 For example, if the over-the-air network is not a single Layer 2 129 domain, the MAC Address Data Item might be the address of the LAN- 130 side interface of the local modem. Alternatively, when used with 131 some kind of backbone infrastructure, the MAC Address Data Item would 132 be the address of the last device reachable on the local Layer 2 133 domain. However, how such remote destinations are discovered is 134 beyond the scope of this specification. 136 As only modems are initially aware of Layer 3 DLEP Destinations, Link 137 Identifier Data Items referring to a new link MUST first appear in a 138 DLEP Destination Up Message from the modem to the router. Once a 139 link has been identified in this way, Link Identifier Data Items MAY 140 be used by either DLEP participant during the lifetime of a DLEP 141 session. Because of this, a router MUST NOT send a DLEP Destination 142 Announce Message containing a Link Identifier Data Item referring to 143 a link that has not been mentioned in a prior DLEP Destination Up 144 Message. 146 Because the MAC Address associated with any DLEP Destination Message 147 containing a Link Identifier Data Item is not the Layer 2 address of 148 the destination, all DLEP Destination Up Messages MUST contain Layer 149 3 information. In the case of modems that provide Layer 3 wide area 150 network connectivity between devices, this means one or more IPv4 or 151 IPv6 Address Data Items providing the Layer 3 address of the 152 destination. When referring to some upstream backbone network 153 infrastructure, this means one or more IPv4 or IPv6 Attached Subnet 154 Data Items, for example: '0.0.0.0/0' or '::/0'. This allows the DLEP 155 peer router to understand the properties of the link to those routes. 157 When the DLEP peer router wishes to forward packets to the Layer 3 158 destination or subnet, the MAC address associated with the link MUST 159 be used as the Layer 2 destination of the packet if it wishes to use 160 the modem network to forward the packet. 162 As most mainstream routers expect to populate their routing 163 information base with the IP address of the next router towards a 164 destination, implementations supporting this extension SHOULD 165 announce one or more valid IPv4 or IPv6 addresses of the last 166 reachable Layer 2 device, i.e. the device with the corresponding MAC 167 Address. 169 If the last reachable Layer 2 device is not the DLEP peer modem, then 170 the modem SHOULD announce a DLEP Destination with the required MAC 171 Address without including a Link Identifier Data Item. 173 2.1. Identifier Restrictions 175 A Link Identifier is by default 4 octets in length. If a modem 176 wishes to use a Link Identifier of a different length, it MUST be 177 announced using the Link Identifier Length Data Item (Section 3.1) 178 contained in the DLEP Session Initialization Response message sent by 179 the modem to the router. 181 During the lifetime of a DLEP session, the length of Link Identifiers 182 MUST remain constant, i.e. the Length field of the Link Identifier 183 Data Item MUST NOT differ between destinations. 185 The method for generating Link Identifiers is a modem implementation 186 matter and out of scope of this document. Routers MUST NOT make any 187 assumptions about the meaning of Link Identifiers, or how Link 188 Identifiers are generated. 190 Within a single DLEP session, all Link Identifiers MUST be unique per 191 MAC Address. This means that a Layer 3 DLEP Destination is uniquely 192 identified by the pair: {MAC Address,Link Identifier}. 194 Link Identifiers MUST NOT be reused, i.e. a {MAC Address,Link 195 Identifier} pair that has been used to refer to one DLEP Destination 196 MUST NOT be recycled to refer to a different destination within the 197 lifetime of a single DLEP session. 199 2.2. Negotiation 201 To use this extension, as with all DLEP extensions, the extension 202 MUST be announced during DLEP session initialization. A router 203 advertises support by including the value 'Link Identifiers' (TBD1), 204 Section 5, in the Extension Data Item within the Session 205 Initialization Message. A modem advertises support by including the 206 value 'Link Identifiers' (TBD1) in the Extension Data Item within the 207 Session Initialization Response Message. If both DLEP peers 208 advertise support for this extension then the Link Identifier Data 209 Item MAY be used. 211 If a modem requires support for this extension in order to describe 212 destinations, and the router does not advertise support, then the 213 modem MUST NOT include a Link Identifier Data Item in any DLEP 214 Message. However, the modem SHOULD NOT immediately terminate the 215 DLEP session, rather it SHOULD use session-wide DLEP Data Items to 216 announce general information about all reachable destinations via the 217 modem. By doing this, a modem allows a router not supporting this 218 extension to at least make a best guess at the state of any reachable 219 network. A modem MUST NOT attempt to re-use the MAC Address Data 220 Item to perform some kind of sleight-of-hand, assuming that the 221 router will notice the DLEP Peer Type of the modem is special in some 222 way. 224 3. New Data Items 226 This extension introduces two new DLEP Data Items: the Link 227 Identifier Data Item (Section 3.2) used to identify a Layer 3 link at 228 or beyond a destination, and the Link Identifier Length Data Item 229 (Section 3.1) used to announce the length of Link Identifiers at 230 session initialization. 232 3.1. Link Identifier Length Data Item 234 The Link Identifier Length Data Item is used by a DLEP modem 235 implementation to specify the length of Link Identifier Data Items. 236 It MUST be used if the specified length is not the default value of 4 237 octets. 239 The Link Identifier Length Data Item MAY be used during Session 240 Initialization, contained in a Session Initialization Response 241 Message. 243 0 1 2 3 244 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 1 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 | Data Item Type | Length | 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | Link Identifier Length | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 Data Item Type: TBD2, Section 5 253 Length: 2 255 Link Identifier Length: The length, in octets, of Link Identifiers 256 used by the DLEP modem for this session. 258 3.2. Link Identifier Data Item 260 The Link Identifier Data Item MAY be used wherever a MAC Address Data 261 Item is defined as usable in core DLEP. 263 0 1 2 3 264 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 1 265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 266 | Data Item Type | Length | 267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 | Link Identifier... : 269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 271 Data Item Type: TBD3, Section 5 273 Length: The length of the Data Item, by default 4, but may be 274 different if a Link Identifier Length Data Item (Section 3.1) has 275 been announced during session initialization. 277 Link Identifier: The unique identifier of the Layer 3 destination. 278 This Link Identifier has no implicit meaning and is only used to 279 discriminate between multiple links. 281 4. Security Considerations 283 As an extension to the core DLEP protocol, the security 284 considerations of that protocol apply to this extension. This 285 extension adds no additional security mechanisms or features. 287 None of the features introduced by this extension require extra 288 consideration by an implementation. 290 5. IANA Considerations 292 Upon approval of this document, IANA is requested to: 294 o Assign a new DLEP Extensions Registry value (TBD1) from the 295 Specification Required section, named "Link Identifiers". 297 o Assign a new DLEP Data Item Type Values Registry value (TBD2) from 298 the Specification Required section, named "Link Identifier 299 Length". 301 o Assign a new DLEP Data Item Type Values Registry value (TBD3) from 302 the Specification Required section, named "Link Identifier". 304 6. References 306 6.1. Normative References 308 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 309 Requirement Levels", BCP 14, RFC 2119, 310 DOI 10.17487/RFC2119, March 1997, 311 . 313 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 314 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 315 DOI 10.17487/RFC8175, June 2017, 316 . 318 6.2. Informative References 320 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 321 IANA Considerations Section in RFCs", RFC 5226, 322 DOI 10.17487/RFC5226, May 2008, 323 . 325 Authors' Addresses 327 Rick Taylor 328 Airbus Defence & Space 329 Quadrant House 330 Celtic Springs 331 Coedkernew 332 Newport NP10 8FZ 333 UK 335 Email: rick.taylor@airbus.com 336 Stan Ratliff 337 VT iDirect 338 13861 Sunrise Valley Drive, Suite 300 339 Herndon, VA 20171 340 USA 342 Email: sratliff@idirect.net