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Farrel 4 Created: May 28, 2009 Old Dog Consulting 5 Expires: November 28, 2009 7 An Inband Data Communication Network For the MPLS Transport Profile 9 draft-ietf-mpls-tp-gach-dcn-03.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with 14 the provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 Abstract 34 The Generic Associated Channel (G-ACh) has been defined as a 35 generalization of the pseudowire (PW) associated control channel to 36 enable the realization of a control/communication channel associated 37 with Multiprotocol Label Switching (MPLS) Label Switched Paths 38 (LSPs), MPLS PWs, MPLS LSP segments, and MPLS sections between 39 adjacent MPLS-capable devices. 41 The MPLS Transport Profile (MPLS-TP) is a profile of the MPLS 42 architecture that identifies elements of the MPLS toolkit that may be 43 combined to build a carrier grade packet transport network based on 44 MPLS packet switching technology. 46 This document describes how the G-ACh may be used to provide the 47 infrastructure that forms part of the Management Communication 48 Network (MCN) and a Signaling Communication Network (SCN). 49 Collectively, the MCN and SCN may be referred to as the Data 50 Communication Network (DCN). This document explains how MCN and SCN 51 messages are encapsulated, carried on the G-ACh, and demultiplexed 52 for delivery to the management or signaling/routing control plane 53 components on a label switching router (LSR). 55 It should be noted that the use of the G-ACh to provide connectivity 56 for the DCN is intended for use only where the MPLS-TP network is not 57 capable of encapsulating or delivering native DCN messages. 59 Conventions used in this document 61 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 62 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 63 document are to be interpreted as described in RFC-2119 [RFC2119]. 65 1. Introduction 67 The associated channel header (ACH) is specified in [RFC4385]. It is 68 a packet header format for use on pseudowires (PWs) in order to 69 identify packets used for OAM and similar functions. 71 The use of the ACH is generalized in [GAL-GACH] and can be applied on 72 any Multiprotocol Label Switching (MPLS) Label Switching Path (LSP). 73 This is referred to as the Generic Associated Channel (G-ACh) and is 74 intended to create a control/management communication channel 75 associated with the LSP that can be used to carry packets used for 76 OAM and similar functions (e.g., control/management plane messages). 78 The purpose of a packet carried on the G-ACh is indicated by the 79 value carried by the Channel Type field of the ACH and a registry of 80 values is maintained by IANA [RFC4446] and [RFC4385]. The combination 81 of the ACH and the ACH TLVs that may be appended to the ACH is 82 referred in this document as the G-ACh header. 84 The MPLS transport profile (MPLS-TP) is described in [MPLS-TP] and in 85 [TP-REQ]. MPLS-TP is the application of MPLS to construct a packet 86 transport network. It constitutes a profile of MPLS that enables 87 operational models typical in transport networks, which includes 88 additional OAM, survivability and other maintenance functions not 89 previously supported by MPLS. 91 Label Switching Routers (LSRs) in MPLS networks may be operated using 92 management protocols or control plane protocols. Messaging in these 93 protocols is normally achieved using IP packets exchanged over IP- 94 capable interfaces. However, some LSRs in MPLS-TP networks may be 95 constructed without support for direct IP encapsulation on their 96 line-side interfaces and without access to an out-of-fiber data 97 communication network. In order that such LSRs can communicate using 98 management plane or control plane protocols channels must be provided 99 and the only available mechanism is to use an MPLS label. 101 The G-ACh provides a suitable mechanism for this purpose, and this 102 document defines processes and procedures to allow the G-ACh to be 103 used to build a management communication network (MCN) and a 104 signaling communication network (SCN) together known as the data 105 communication network (DCN) [G.7712]. 107 1.1. Requirements 109 The requirements presented in this section are based on those 110 communicated to the IETF by the ITU-T. 112 1. A packet encapsulation mechanism must be provided to support the 113 transport of MCN and SCN packets over the G-ACh. 115 2. The G-ACh carrying the MCN and SCN packets shall support the 116 following application scenarios: 118 a. The G-ACh interconnects two adjacent MPLS-TP nodes (used when 119 the server layer does not provide a Management Communication 120 Channel (MCC) or a Signalling Communication Channel (SCC)). 122 b. The G-ACh is carried by a MPLS-TP tunnel that traverses another 123 operator's domain (carrier's carrier scenario) 125 3. The G-ACh shall provide two independent channels: a MCC to build 126 the MCN and a SCC to build the SCN. The G-ACh packet header shall 127 indicate whether the packet is a MCC or an SCC packet in order to 128 forward it to the management or control plane application for 129 processing. 131 4. The channel separation mechanism shall allow the use of separate 132 rate limiters and traffic shaping functions for each channel (MCC 133 and SCC) ensuring that the flows do not exceed their assigned 134 traffic profile. The rate limiter and traffic shaper are outside 135 the scope of the MCC and SCC definition. 137 5. The G-ACh that carries the MCC and SCC shall be capable of 138 carrying different OSI layer 3 (network layer) PDUs. These shall 139 include IPv4, IPv6, and OSI PDUs. The G-ACh header of the MCC/SCC 140 packet shall indicate which layer 3 PDU is contained in the 141 payload field of the packet such that the packet can be forwarded 142 to the related layer 3 process within the management and control 143 plane application, respectively, for further processing. 145 6. The G-ACh is not required to provide specific security mechanisms. 146 However, the management or control plane protocols that operate 147 over the MCC or SCC are required to provide adequate security 148 mechanisms in order not to be susceptible to security attacks. 150 2. Procedures 152 Figure 1 depicts the format of an MCC/SCC packet that is sent on the 153 G-ACh. The Channel Type field indicates the function of the ACH 154 message so, to send an MCC/SCC packet on the G-ACh, the MCC/SCC 155 message is prepended with an ACH with the Channel Type set to 156 indicate that the message is a MCC or SCC message. The ACH MUST 157 include the ACH Protocol ID TLV [ACH-TLV] to identify the protocol 158 type of the MCC or SCC message, and MAY include further ACH TLVs. 160 0 1 2 3 161 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 1 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 |0 0 0 1|Version| Reserved | Channel Type | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | ACH TLV Header | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | ACH Protocol ID TLV | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 ~ zero or more other ACH TLVs ~ 170 ~ ~ 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | MCC/SCC Message | 173 ~ ~ 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 Figure 1: G-ACh MCC/SCC Packet 178 o The Channel Type field determines whether the message is an MCC or 179 an SCC message. See Section 4 for the codepoint assignments. 181 o The ACH Protocol ID TLV identifies the PDU type of the MCC/SCC 182 message. The ACH Protocol ID TLV is defined in [ACH-TLV] and uses 183 the PPP protocol identifiers to distinguish different protocols 184 [RFC1661]. 186 When the G-ACh sender receives an MCC message that is to be sent over 187 the MCC, the sender creates the G-ACh header, provides an ACH 188 Protocol ID TLV indicating the MCC layer 3 PDU type, sets the Channel 189 Type field to MCC, and prepends the MCC message with the G-ACh 190 header. The same procedure is applied when a control plane message is 191 to be sent over the SCC. In this case, the sender sets the Channel 192 Type field to SCC. 194 If the G-ACh is associated with an MPLS section, the GAL is added to 195 the message as defined in [GAL-GACH]. The TTL field MUST be set to 1, 196 and the S-bit of the GAL MUST be set to 1. 198 If the G-ACh is associated with an LSP, the GAL is added to the 199 packet and the LSP label is pushed on top of the GAL as defined in 200 [GAL-GACH]. The TTL field of the GAL MUST be set to 1, and the S-bit 201 of the GAL MUST be set to 1. 203 The DCN channel MUST NOT be used to transport user traffic and SHALL 204 only be used to carry management or control plane messages. 205 Procedures that ensure this such as deep packet inspection are 206 outside the scope of this specification. 208 When a receiver has received a packet on the G-ACh with the ACH 209 Channel Type set to MCC or SCC, it SHALL look at the PID field 210 carried in the ACH Protocol ID TLV. If the TLV is absent, the message 211 SHALL be silently discarded, although a local system MAY increment a 212 counter that records discarded or errored packets, and MAY log an 213 event. If the PID value is known by the receiver it SHALL deliver the 214 entire packet including the MCC/SCC message to the appropriate 215 processing entity. If the PID value is unknown, the receiver SHALL 216 silently discard the received packet, MAY increment a counter that 217 records discarded or errored messages, and MAY log an event. 219 It must be noted that according to [GAL-GACH] a receiver MUST NOT 220 forward a GAL packet based on the GAL label as is normally the case 221 for MPLS packets. If the GAL appears at the bottom of the label 222 stack, it MUST be processed as described in the previous paragraph. 224 Note that there is no requirement for MPLS-TP devices to support IP 225 or OSI forwarding in the fast or slow paths. Thus, if a message is 226 received on the MCC or SCC and is not targeted to an address of the 227 receiving LSR, the LSR MAY discard the message as incorrectly 228 received using whatever mechanisms are necessary according to layer 3 229 protocol concerned. 231 2.1. Pseudowire Setup 233 Provider Edge nodes may wish to set up PWs using a singaling protocol 234 that uses remote adjacencies (such as LDP [RFC5036]). In the absence 235 of an IP-based control plane network, these PEs MUST first set up an 236 LSP tunnel across the MPLS-TP network. This tunnel can be used both 237 to carry the PW once it has been set up and to provide a G-ACh based 238 DCN for control plane communications between t`he PEs. 240 Note that messages delivered on the G-ACh MUST NOT be forwarded based 241 on their payload (for example, IP, CLNS, etc). 243 3. Security Considerations 245 The G-ACh provides a virtual link between LSRs and might be used to 246 induce many forms of security attack. Protocols that operate over the 247 MCN or SCN are REQUIRED to include adequate security mechanisms and 248 implementations MUST allow operators to configure the use of those 249 mechanisms. 251 4. IANA Considerations 253 Channel Types for the Generic Associated Channel are allocated from 254 the IANA PW Associated Channel Type registry defined in [RFC4446] and 255 updated by [GAL-GACH]. 257 IANA is requested to allocate two further Channel Types as follows: 258 xx Management Communication Channel (MCC) 259 yy Signaling Communication Channel (SCC) 261 5. Normative References 263 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 264 Requirement Levels", BCP 14, RFC 2119, March 1997. 266 [RFC4385] Bryant, S., et al., "Pseudowire Emulation Edge-to-Edge 267 (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, 268 February 2006. 270 [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge 271 Emulation (PWE3)", RFC 4446, April 2006 . 273 [GAL-GACH] Vigoureux, M., Bocci, M., Ward, D., Swallow, G., and R. 274 Aggarwal, "MPLS Generic Associated Channel", 275 draft-ietf-mpls-tp-gach-gal, work in progress. 277 [ACH-TLV] Bryant, S., et al., "Definition of ACH TLV Structure", 278 draft-bryant-mpls-tp-ach-tlv, work in progress. 280 6. Informative References 282 [MPLS-TP] Bryant, S., Bocci, M., Lasserre, M., "A Framework for MPLS 283 in Transport Networks", draft-ietf-mpls-tp-framework, work 284 in progress. 286 [TP-REQ] B. Niven-Jenkins, Ed., D. Brungard, Ed., M. Betts, Ed., 287 N. Sprecher, S. Ueno, "MPLS-TP Requirements", 288 draft-ietf-mpls-tp-requirements, work in progress. 290 [G.7712] ITU-T Recommendation G.7712, "Architecture and 291 specification of data communication network", June 2008. 293 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 294 RFC 1661, July 1994. 296 [RFC5036] Andersson, L., Minei, I., and Thomas, B., "LDP 297 Specification", RFC 5036, October 2007. 299 7. Acknowledgements 301 The editors wish to thank Pietro Grandi, Martin Vigoureux, and Kam 302 Lam for their contribution to this document. 304 8. Authors' Addresses 306 Dieter Beller 307 Alcatel-Lucent Germany 308 EMail: dieter.beller@alcatel-lucent.com 310 Adrian Farrel 311 Old Dog Consulting 312 EMail: adrian@olddog.co.uk 314 Full Copyright Statement 316 The IETF Trust takes no position regarding the validity or scope of 317 any Intellectual Property Rights or other rights that might be 318 claimed to pertain to the implementation or use of the technology 319 described in any IETF Document or the extent to which any license 320 under such rights might or might not be available; nor does it 321 represent that it has made any independent effort to identify any 322 such rights. 324 Copies of Intellectual Property disclosures made to the IETF 325 Secretariat and any assurances of licenses to be made available, or 326 the result of an attempt made to obtain a general license or 327 permission for the use of such proprietary rights by implementers or 328 users of this specification can be obtained from the IETF on-line IPR 329 repository at http://www.ietf.org/ipr 331 The IETF invites any interested party to bring to its attention any 332 copyrights, patents or patent applications, or other proprietary 333 rights that may cover technology that may be required to implement 334 any standard or specification contained in an IETF Document. 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