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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'EUI-64' == Outdated reference: draft-ietf-mpls-gach-adv has been published as RFC 7212 -- Possible downref: Non-RFC (?) normative reference: ref. 'LLDP' Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS D. Frost 3 Internet-Draft S. Bryant 4 Intended status: Standards Track Cisco Systems 5 Expires: January 25, 2014 M. Bocci 6 Alcatel-Lucent 7 July 24, 2013 9 MPLS-TP Next-Hop Ethernet Addressing 10 draft-ietf-mpls-tp-ethernet-addressing-08 12 Abstract 14 The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP) 15 is the set of MPLS protocol functions applicable to the construction 16 and operation of packet-switched transport networks. This document 17 presents considerations for link-layer addressing of Ethernet frames 18 carrying MPLS-TP packets. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on January 25, 2014. 37 Copyright Notice 39 Copyright (c) 2013 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 1. Introduction 54 The MPLS Transport Profile (MPLS-TP) [RFC5921] is the set of protocol 55 functions that meet the requirements [RFC5654] for the application of 56 MPLS to the construction and operation of packet-switched transport 57 networks. The MPLS-TP data plane consists of those MPLS-TP functions 58 concerned with the encapsulation and forwarding of MPLS-TP packets 59 and is described in [RFC5960]. 61 This document presents considerations for link-layer addressing of 62 Ethernet frames carrying MPLS-TP packets. Since MPLS-TP packets are 63 MPLS packets, existing procedures ([RFC3032], [RFC5332]) for the 64 encapsulation of MPLS packets over Ethernet apply. Because IP 65 functionality is only optional in an MPLS-TP network, IP-based 66 protocols for Media Access Control (MAC) address learning, such as 67 the Address Resolution Protocol (ARP) [RFC0826] and IP version 6 68 Neighbor Discovery [RFC4861], may not be available. This document 69 specifies the options for the determination and selection of the 70 next-hop Ethernet MAC address when MPLS-TP is used between nodes that 71 do not have an IP dataplane. 73 1.1. Terminology 75 Term Definition 76 ------- --------------------------- 77 ARP Address Resolution Protocol 78 G-ACh Generic Associated Channel 79 LSP Label Switched Path 80 LSR Label Switching Router 81 MAC Media Access Control 82 MPLS-TP MPLS Transport Profile 84 Additional definitions and terminology can be found in [RFC5960] and 85 [RFC5654]. 87 1.2. Requirements Language 89 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 90 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 91 document are to be interpreted as described in [RFC2119]. 93 2. Point-to-Point Link Addressing 94 When two MPLS-TP nodes are connected by a point-to-point Ethernet 95 link, the question arises as to what destination Ethernet Media 96 Access Control (MAC) address should be specified in Ethernet frames 97 transmitted to the peer node over the link. The problem of 98 determining this address does not arise in IP/MPLS networks because 99 of the presence of the Ethernet Address Resolution Protocol (commonly 100 referred to as Address Resolution Protocol and shortened to 101 ARP)[RFC0826] or IP version 6 Neighbor Discovery (ND) protocol 102 [RFC4861], which allow the unicast MAC address of the peer device to 103 be learned dynamically. 105 If existing mechanisms are available in an MPLS-TP network to 106 determine the destination unicast MAC addresses of peer nodes, for 107 example, if the network also happens to be an IP/MPLS network, or if 108 Link Layer Discovery Protocol (LLDP) [LLDP] is in use, these methods 109 SHOULD be used. If ARP, ND and LLDP are not available, and both 110 peers implement the procedures in Section 4 of this document, then 111 the GAP mechanism described in this memo SHOULD be used. The 112 remainder of this section discusses alternative options that might be 113 employed when none of the preceding MAC address learning mechanism 114 are available. 116 One common approach is for each node to be statically configured with 117 the MAC address of its peer. However static MAC address 118 configuration can present an administrative burden and lead to 119 operational problems. For example, replacement of an Ethernet 120 interface to resolve a hardware fault when this approach is used 121 requires that the peer node be manually reconfigured with the new MAC 122 address. This is especially problematic if the peer is operated by 123 another provider. 125 Another approach which may be considered is to use the Ethernet 126 broadcast address FF-FF-FF-FF-FF-FF as the destination MAC address in 127 frames carrying MPLS-TP packets over a link that is known to be 128 point-to-point. This may, however, lead to excessive frame 129 distribution and processing at the Ethernet layer. Broadcast traffic 130 may also be treated specially by some devices and this may not be 131 desirable for MPLS-TP data frames. 133 In view of the above considerations, this document recommends that, 134 if a non-negotiated address is to be used, both nodes are configured 135 to use as a destination MAC address an Ethernet multicast address 136 reserved for MPLS-TP for use over point-to-point links. The address 137 allocated for this purpose by the Internet Assigned Numbers Authority 138 (IANA) is 01-00-5E-90-00-00. An MPLS-TP implementation MUST default 139 to passing MPLS packets received from a point-to-point Ethernet link 140 with this destination MAC address to the MPLS sub-system. 142 The use of broadcast or multicast addressing for the purpose 143 described in this section, i.e. as a placeholder for the unknown 144 unicast MAC address of the destination, is applicable only when the 145 attached Ethernet link is known to be point-to-point. If a link is 146 not known to be point-to-point, these forms of broadcast or multicast 147 addressing MUST NOT be used. Thus the implementation MUST provide a 148 means for the operator to declare that a link is point-to-point if it 149 supports these addressing modes. Moreover, the operator is cautioned 150 that it is not always clear whether a given link is, or will remain, 151 strictly point-to-point, particularly when the link is supplied by an 152 external provider; point-to-point declarations therefore need to be 153 used with care. Because of these caveats it is RECOMMENDED that 154 implementations support the procedures in Section 4 so that unicast 155 addressing can be used. 157 3. Multipoint Link Addressing 159 When a multipoint Ethernet link serves as a section [RFC5960] for a 160 point-to-multipoint MPLS-TP LSP, and multicast destination MAC 161 addressing at the Ethernet layer is used for the LSP, the addressing 162 and encapsulation procedures specified in [RFC5332] SHALL be used. 164 When a multipoint Ethernet link, that is a link which is not known to 165 be point-to-point, serves as a section for a point-to-point MPLS-TP 166 LSP, unicast destination MAC addresses MUST be used for Ethernet 167 frames carrying packets of the LSP. According to the discussion in 168 the previous section, this implies the use of either static MAC 169 address configuration or a protocol that enables peer MAC address 170 discovery. 172 4. MAC Address Discovery via the G-ACh Advertisement Protocol 174 The G-ACh Advertisement Protocol (GAP) [I-D.ietf-mpls-gach-adv] 175 provides a simple means of informing listeners on a link of the 176 sender's capabilities and configuration. When used for this purpose 177 on an Ethernet link, GAP messages are multicast to the address 178 01-00-5e-80-00-0d (see [I-D.ietf-mpls-gach-adv] Section 7). If these 179 messages contain the unicast MAC address of the sender, then 180 listeners can learn this address and use it in the future when 181 transmitting frames containing MPLS-TP packets. Since the GAP does 182 not rely on IP, this provides a means of unicast MAC discovery for 183 MPLS-TP nodes without IP support. 185 This document defines a new GAP application "Ethernet Interface 186 Parameters" (TBD1), to support the advertisement of Ethernet-specific 187 parameters associated with the sending interface. The following 188 Type-Length-Value (TLV) objects are defined for this application; the 189 TLV format is as defined in [I-D.ietf-mpls-gach-adv]: 191 Source MAC Address (type = 0, length = 8): The Value of this 192 object is an EUI-64 [EUI-64] unicast MAC address assigned to one 193 of the interfaces of the sender that is connected to this data 194 link. The IEEE-defined mapping from 48-bit MAC addresses to 195 EUI-64 form is used. 197 Maximum Frame Size (MFS) (type = 1, length = 4): The Value of this 198 object is a 32-bit unsigned integer encoded in network byte order 199 that specifies the maximum frame size in octets of an Ethernet 200 Frame that can be sent over the sending interface. Where MAC 201 address learning occurs by some other means, this TLV group MAY be 202 used to advertise only the MFS. If multiple advertisements are 203 made for the same parameter, use of these advertisements is 204 undefined. 206 0 1 2 3 207 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 1 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Type=0 | Reserved | Length=8 | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 | MAC Address in EUI-64 Format | 212 | | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 Figure 1: Source MAC Address Object Format 217 0 1 2 3 218 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 1 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | Type=1 | Reserved | Length=4 | 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 | Maximum Frame Size (MFS) | 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 Figure 2: MFS Object Format 227 Per [I-D.ietf-mpls-gach-adv], MAC Address Discovery information needs 228 to be periodically retransmitted and is to be retained by a receiver 229 based on the period of time indicated by the associated Lifetime 230 field. To expedite the initialization of a link it is RECOMMENDED 231 that a node that has been reconfigured, rebooted or is aware that it 232 have been disconnected from its peer send a GAP Ethernet Interface 233 Parameter message, and that it issues a GAP request message for the 234 Ethernet parameters at the earliest opportunity. 236 When the MAC address in the received Source MAC Address TLV changes 237 the new MAC address MUST be used (see Section 5.2 of 238 [I-D.ietf-mpls-gach-adv]). 240 If a minimum MFS is configured for a link and the MFS advertised by 241 the peer is lower than that minimum, the operator MUST be notified of 242 the MFS mismatch. Under these circumstances the operator may choose 243 to configure the LSR to shut the link, thereby triggering a fault, 244 and hence causing the end-to-end path to be repaired. Alternatively 245 the operator may choose to configure the LSR to leave the link up so 246 that an OAM message can be used to verify the actual MFS. 248 A peer node could cease transmission of G-ACh advertisements, or 249 cease to include a Source MAC Address TLV in advertisements, or cease 250 to be connected, any of which will cause the TLV lifetime to expire. 251 After the Source MAC Address TLV lifetime has expired, this MAC 252 Address MUST NOT be used as the peer MAC address. The node MUST 253 return to selecting MAC addresses as though no advertisements were 254 received, using the method configured for this eventuality. 256 5. Manageability Considerations 258 The values sent and received by this protocol MUST be made accessible 259 for inspection by network operators, and where local configuration is 260 updated by the received information, it MUST be clear why the 261 configured value has been changed. The information being advertised 262 SHOULD be persistent across restarts. To ensure correct operation 263 when an equipment restarts in a new environment, previously received 264 advertisements MUST be discarded across restarts. If the received 265 values change, the new values MUST be used and the change made 266 visible to the network operators. 268 Where the link changes to a new type, i.e. from point-to-point to 269 point-to-multipoint the network operator SHOULD be informed. If the 270 new link type is incompatible with the addressing Ethernet method in 271 use the system MUST take the action that is configured under those 272 circumstances. 274 6. Security Considerations 276 The use of broadcast or multicast Ethernet destination MAC addresses 277 for frames carrying MPLS-TP data packets can potentially result in 278 such frames being distributed to devices other than the intended 279 destination node or nodes when the Ethernet link is not point-to- 280 point. The operator should take care to ensure that MPLS-TP nodes 281 are aware of the Ethernet link type (point-to-point or multipoint). 282 In the case of multipoint links, the operator should either ensure 283 that no devices are attached to the link that are not authorized to 284 receive the frames, or take steps to mitigate the possibility of 285 excessive frame distribution, for example by configuring the Ethernet 286 switch to appropriately restrict the delivery of multicast frames to 287 authorized ports. 289 An attacker could disrupt communications by modifying the Source MAC 290 Address or the MFS values, however this is mitigated by the use of 291 cryptographic authentication as described in [I-D.ietf-mpls-gach-adv] 292 which also describes other considerations applicable to the GAP 293 protocol. Visibility into the contents of either of the TLVs could 294 provide information that is useful for an attacker. This is best 295 addressed by physical security of the links. 297 7. IANA Considerations 299 7.1. Ethernet Multicast Address Allocation 301 IANA has allocated an Ethernet multicast address from the "IANA 302 Multicast 48-bit MAC Addresses" address block in the "Ethernet 303 Numbers" registry for use by MPLS-TP LSRs over point-to-point links 304 as described in Section 2. The allocated address is 305 01-00-5E-90-00-00. IANA is requested to update the reference to 306 point to the RFC number assigned to this document. 308 7.2. G-ACh Advertisement Protocol Allocation 310 IANA is requested to allocate a new Application ID in the "G-ACh 311 Advertisement Protocol Applications" registry 312 [I-D.ietf-mpls-gach-adv] (currently located in the "Pseudowire Name 313 Spaces (PWE3)"), as follows: 315 Application ID Description Reference 316 ------------------------- --------------------------- --------------- 317 TBD1 to be assigned by Ethernet Interface (this draft) 318 IANA Parameters 320 7.3. Creation of Ethernet Interface Parameters Registry 322 IANA is requested to create a new registry, "G-ACh Advertisement 323 Protocol: Ethernet Interface Parameters" within the "Pseudowire Name 324 Spaces (PWE3)" with fields and initial allocations as follows: 326 Type Name Type ID Reference 327 ------------------ ------- ------------ 328 Source MAC Address 0 (this draft) 329 Maximum Frame Size 1 (this draft) 330 The range of the Type ID field is 0 - 255. 332 The allocation policy for this registry is IETF Review or IESG 333 approval. 335 8. Acknowledgements 337 We thank Adrian Farrel for his valuable review comments on this 338 document. 340 9. References 342 9.1. Normative References 344 [EUI-64] , "[EUI64] IEEE, "Guidelines for 64-bit Global Identifier 345 (EUI-64) Registration Authority", http:// 346 standards.ieee.org/regauth/oui/tutorials/EUI64.html, March 347 1997.", . 349 [I-D.ietf-mpls-gach-adv] 350 Frost, D., Bryant, S., and M. Bocci, "MPLS Generic 351 Associated Channel (G-ACh) Advertisement Protocol", draft- 352 ietf-mpls-gach-adv-08 (work in progress), June 2013. 354 [LLDP] , "IEEE, "Station and Media Access Control Connectivity 355 Discovery (802.1AB)", September 2009.", . 357 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 358 Requirement Levels", BCP 14, RFC 2119, March 1997. 360 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 361 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 362 Encoding", RFC 3032, January 2001. 364 [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS 365 Multicast Encapsulations", RFC 5332, August 2008. 367 [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., 368 and S. Ueno, "Requirements of an MPLS Transport Profile", 369 RFC 5654, September 2009. 371 [RFC5960] Frost, D., Bryant, S., and M. Bocci, "MPLS Transport 372 Profile Data Plane Architecture", RFC 5960, August 2010. 374 9.2. Informative References 376 [RFC0826] Plummer, D., "Ethernet Address Resolution Protocol: Or 377 converting network protocol addresses to 48.bit Ethernet 378 address for transmission on Ethernet hardware", STD 37, 379 RFC 826, November 1982. 381 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 382 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 383 September 2007. 385 [RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. 386 Berger, "A Framework for MPLS in Transport Networks", RFC 387 5921, July 2010. 389 Authors' Addresses 391 Dan Frost 392 Cisco Systems 394 Email: danfrost@cisco.com 396 Stewart Bryant 397 Cisco Systems 399 Email: stbryant@cisco.com 401 Matthew Bocci 402 Alcatel-Lucent 404 Email: matthew.bocci@alcatel-lucent.com