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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'G.984' is mentioned on line 200, but not defined == Missing Reference: 'RFC4385' is mentioned on line 405, but not defined == Missing Reference: 'G.984.3' is mentioned on line 410, but not defined ** Obsolete normative reference: RFC 4447 (Obsoleted by RFC 8077) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 pwe3 Working Group H. Li 3 Internet-Draft R. Zheng 4 Intended status: Informational Huawei Technologies 5 Expires: April 1, 2012 A. Farrel 6 Old Dog Consulting 7 September 29, 2011 9 Multisegment Pseudowires in Passive Optical Networks 10 draft-li-pwe3-ms-pw-pon-06 12 Abstract 14 This document describes the application of MPLS multi-segment 15 pseudowires (MS-PWs) in a dual-technology environment comprising a 16 Passive Optical Network (PON) and an MPLS Packet Switched Network 17 (PSN). 19 PON technology may be used in mobile backhaul networks to support the 20 end segments closest to the aggregation devices. In these cases, 21 there may be a very large number of Pseudowire (PW) Terminating 22 Provider Edge nodes (T-PEs). The MPLS control plane could be used to 23 provision these end segments, but support for the necessary protocols 24 would complicate the management of the T-PEs and would significantly 25 increase their expense. Alternatively, static, or management plane, 26 configuration could be used to configure the end segments, but the 27 very large number of such segments in a PON places a very heavy 28 burden on the network manager. 30 This document describes how to set up the end segment of an end-to- 31 end MPLS PW over a Gigabit-capable Passive Optical Network (G-PON) or 32 10 Gigabit-capable Passive Optical Network (XG-PON) using the G-PON 33 and XG-PON management protocol, Optical Network Termination 34 Management and Control Interface (OMCI). This simplifies and speeds 35 up PW provisioning compared with manual configuration. 37 This document also shows how a MS-PW may be constructed from an end 38 segment supported over a PON, and switched to one or more segments 39 supported over an MPLS PSN. 41 Status of this Memo 43 This Internet-Draft is submitted in full conformance with the 44 provisions of BCP 78 and BCP 79. 46 Internet-Drafts are working documents of the Internet Engineering 47 Task Force (IETF). Note that other groups may also distribute 48 working documents as Internet-Drafts. The list of current Internet- 49 Drafts is at http://datatracker.ietf.org/drafts/current/. 51 Internet-Drafts are draft documents valid for a maximum of six months 52 and may be updated, replaced, or obsoleted by other documents at any 53 time. It is inappropriate to use Internet-Drafts as reference 54 material or to cite them other than as "work in progress." 56 This Internet-Draft will expire on April 1, 2012. 58 Copyright Notice 60 Copyright (c) 2011 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (http://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 2. Terminology for G-PON/XG-PON . . . . . . . . . . . . . . . . . 6 77 3. Multi-Segment Pseudowire over PON Network Reference Model . . 7 78 4. Label Provisioning for Pseudowires over PON . . . . . . . . . 10 79 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 80 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 81 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 82 7.1. Normative References . . . . . . . . . . . . . . . . . . . 11 83 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 86 1. Introduction 88 The use of PWs in Packet Switched Networks (PSNs) is defined in 89 [RFC3985]. This architecture is extended in [RFC5659] for multi- 90 segment pseudowires (MS-PWs) satisfying the requirements in 91 [RFC5254]. More detail on MS-PWs is provided in [RFC6073]. 93 A MS-PW is a useful technology for certain applications where there 94 is an aggregation of paths toward a common point in the network, e.g. 95 mobile backhaul; the segments can be aggregated within tunnels 96 between PW switching points thus improving scalability and reducing 97 the number of control plane adjacencies where a control plane is 98 used. 100 Segments of a MS-PW in a PSN can be setup using manual provisioning 101 (static PWs) or using a dynamic control plane such as the Label 102 Distribution Protocol (LDP)[RFC5036] [RFC4447]. 104 In many scenarios in access and metro networks, Passive Optical 105 Network (PON) provides longer distance, higher bandwidth with better 106 economy than other technologies like point-to-point Ethernet or 107 Digital Subscriber Line (DSL). Mobile backhaul with PON is already 108 being deployed. 110 Figure A depicts the physical infrastructure of an Optical 111 Distribution Network (ODN). 113 | | 114 |<--Optical Distribution Network-->| 115 | | 116 | branch main | 117 +-----+ fibers fiber 118 Base ------| | | | 119 Stations ------| ONU |\ | | 120 ------| | \ V | 121 +-----+ \ | 122 \ +----------+ | 123 +-----+ \| | | +-----+ 124 Base ------| | | Optical | V | | 125 Stations ------| ONU |---------| Splitter |-------------| OLT | 126 ------| | /| | | | 127 +-----+ / +----------+ +-----+ 128 / 129 +-----+ / 130 Base ------| |/ 131 Stations ------| ONU | 132 ------| | 133 +-----+ 135 Figure A: Typical PON System Architecture 137 In a PON, the Optical Network Unit (ONU) and Optical Line Termination 138 (OLT) are adjacent nodes connected by an Optical Distribution Network 139 (ODN), which consists of optical fibers and optical splitters in a 140 tree topology. The link between each ONU and OLT is simulated as a 141 point-to-point link, and there is no path redundancy between them. 142 The OLT resides in the central office, while ONUs reside in customer 143 premises. ONUs are deployed in huge numbers and so they are cost 144 sensitive. More information about ODNs can be found in [G.984.1]. 146 In a mobile backhaul network, many 2G and 3G base stations still use 147 legacy interfaces like TDM and ATM. Therefore, these native services 148 must be carried across the PON before they can be carried over the 149 PSN using PWs. This document describes how MS-PWs can be constructed 150 with end segments that operate over the PON and are switched to 151 further segments operated over the PSN. In this case, the base 152 stations are connected by access circuits (ACs) to the ONUs which act 153 as Terminating Provider Edge nodes (T-PEs). The OLT is a Switching 154 Provider Edge (S-PE). This model is shown in Figure B. 156 Routing protocols and dynamic label distribution protocols like LDP 157 would significantly increase the ONUs' cost and complexity as they 158 place requirements on both hardware and software. Besides coding and 159 maintenance of these new protocols, a much more powerful CPU and more 160 memory are also necessary for them to run smoothly. 162 As there is no redundant path between each ONU and the OLT, routing 163 and path selection are not necessary in the PON. Therefore, static 164 provision of PWs labels between ONUs and the OLT is simple, and is 165 preferred because it can greatly reduce the cost of an ONU that acts 166 as a T-PE. However, use of a Network Management System (NMS) to 167 provision PWs in a PON would require the network manager to configure 168 each ONU, and to configure the OLT once for each PW. Since there may 169 be very many ONUs (and hence very many PWs) in a PON, this requires a 170 large amount of operational effort. Additionally, there is an issue 171 that the configuration of each PW at the OLT and ONU might be 172 inconsistent since these nodes are configured separately. . 174 [G.988] defines the G-PON/XG-PON management protocol called the ONT 175 Management and Control Interface (OMCI). OMCI is an implementation 176 requirement for all G-PON/XG-PON systems. If OMCI is used to 177 configure PWs on an ONU, no upgrade to an ONU's hardware is required 178 and the extension to the OMCI implementation is negligible. This 179 provides a way of reducing the cost and complexity of provisioning 180 PWs in a G-PON/XG-PON. 182 This document shows how the two technologies (PON and PSN) can be 183 combined to provide an end-to-end multi-segment MPLS PW. The MPLS 184 PWs are also carried over the PON in MPLS LSP tunnels. There is an 185 MPLS LSP tunnel each direction between each ONU and the OLT in a one- 186 to-one relationship with the underlying G-PON/XG-PON channel. The 187 OLT and ONU perform penultimate hop popping (PHP) [RFC3031] on this 188 single-hop LSP so no labels are used on the wire for the MPLS LSP 189 tunnel. There is no change to the operation of MPLS PWs, and MPLS 190 packets are carried by the G-PON link layer according to ITU-T 191 [G.984.3amd1] or XG-PON link layer according to ITU-T [G.987.3]. 193 2. Terminology for G-PON/XG-PON 195 We defined the following terms derived from [G.987]: 197 o Gigabit-capable Passive Optical Network (G-PON). A variant of the 198 Passive Optical Network (PON) access technology supporting 199 transmission rates in excess of 1Gbps and based on the ITU-T 200 G.984.x series of Recommendations [G.984]. 202 o G-PON Encapsulation Method (GEM). A data frame transport scheme 203 used in G-PON systems that is connection-oriented and that 204 supports fragmentation of the user data frames into variable sized 205 transmission fragments. 207 o GEM Port. An abstraction of the G-PON adaptation layer 208 representing a logical connection associated with a specific 209 client packet flow between the OLT and the ONU. 211 o 10-gigabit-capable passive optical network (XG-PON): A PON system 212 supporting nominal transmission rates on the order of 10 Gbit/s in 213 at least one direction, and implementing the suite of protocols 214 specified in the ITU-T G.987.x series Recommendations. 216 o XG-PON encapsulation method (XGEM): A data frame transport scheme 217 used in XG PON systems that is connection-oriented and that 218 supports fragmentation of user data frames into variable sized 219 transmission fragments. 221 o XGEM port: An abstraction in the XGTC service adaptation sublayer 222 representing a logical connection associated with a specific 223 client packet flow. 225 o Optical Distribution network (ODN). In the PON context, a tree of 226 optical fibers in the access network, supplemented with power or 227 wavelength splitters, filters, or other passive optical devices. 229 o Optical Line Termination (OLT). A device that terminates the 230 common (root) endpoint of an ODN, implements a PON protocol, such 231 as that defined by ITU-T G.984 series, and adapts PON PDUs for 232 uplink communications over the provider service interface. The 233 OLT provides management and maintenance functions for the 234 subtended ODN and ONUs. In this document, the OLT is a network 235 element with multiple PON ports and uplinks that provide switching 236 capability to the PSN. 238 o Optical Network Termination (ONT). A single subscriber device 239 that terminates any one of the distributed (leaf) endpoints of an 240 ODN, implements a PON protocol, and adapts PON PDUs to subscriber 241 service interfaces. An ONT is a special case of an ONU. 243 o Optical Network Unit (ONU). A generic term denoting a device that 244 terminates any one of the distributed (leaf) endpoints of an ODN, 245 implements a PON protocol, and adapts PON PDUs to subscriber 246 service interfaces. In some contexts, an ONU implies a multiple 247 subscriber device. In this document, an ONU is a Provider Edge 248 (PE) node with one or more ACs that map to the service interfaces. 249 The ONU acts as a T-PE. 251 o ONT Management and Control Interface (OMCI). The management and 252 control channel between OLT and ONT in PON. The OMCI protocol 253 runs between the OLT Controller and the ONT Controller across a 254 GEM connection that is established at ONT initialization. The 255 OMCI protocol is asymmetric: the Controller in the OLT is the 256 master and the one in the ONT is the slave. A single OLT 257 Controller using multiple instances of the protocol over separate 258 control channels may control multiple ONTs. The OMCI protocol is 259 used to manage the ONT in areas of configuration, fault 260 management, performance and security. 262 o Passive Optical Network (PON). An OLT connected using an ODN to 263 one or more ONUs or ONTs. 265 3. Multi-Segment Pseudowire over PON Network Reference Model 267 [RFC5659] provides several pseudowire emulation edge-to-edge (PWE3) 268 reference architectures for the multi-segment case. These are 269 general models extended from [RFC3985] to enable point-to-point 270 pseudowires through multiple PSN tunnels. 272 A G-PON/XGPON consists of an OLT, an ODN and multiple ONUs. The ODN 273 is actually a fiber tree that provides physical connections between 274 the OLT and the ONUs. G-PON/XG-PON has its own physical layer and 275 link layer. A GEM/XGEM Port is a logical point-to-point connection 276 between the OLT and each ONU over GPON Transmission Convergence (GTC) 277 layer/XG-PON transmission convergence (XGTC) layer. There can be 278 more than one GEM/XGEM port between the OLT and an individual ONU. 279 Each GEM/XGEM port can be assigned different QoS and bandwidth. 281 Figure B shows how the MS-PW architecture is applied to a network 282 comprising a PON and a PSN. The Terminating PE1 (TPE1) is an ONU and 283 the Switching PE1 (SPE1) is an OLT. One or more PWs runs between the 284 ONU and the remote end system (TPE2) to provide service emulation 285 between CEs (CE1 and CE2). 287 In each of the PON and PSN, the PW segments are carried in PSN 288 tunnels. In the PSN, the tunnel is established and operated as 289 normal for PWs (see [RFC3985]). In the PON, the tunnel used is a 290 single-hop MPLS LSP tunnel so that the OLT and ONU are label edge 291 routers. The OLT and ONU make use of PHP on the MPLS LSP tunnel and, 292 since this is a single hop LSP (there are no MPLS-capable nodes 293 between the OLT and ONU) this means that there is no MPLS 294 encapsulation for the MPLS LSP tunnel on the wire (that is, no label 295 or shim header is used). This results in the on-wire encapsulations 296 shown in Figure C. 298 Native |<------Multi-Segment Pseudowire------>| Native 299 Service | GEM/XGEM | Service 300 (AC) | |<--Port-->| | (AC) 301 | | | | | | 302 | | | PSN | PSN | | 303 | | |<-Tunnel->| |<-Tunnel->| | | 304 | V V V V V V | 305 | +----+ +-----+ +----+ | 306 +----+ | |TPE1|===========|S-PE1|==========|TPE2| | +----+ 307 | |------|..... PW.Seg't1....X....PW.Seg't3.....|-------| | 308 | CE1| | | | | | | | | |CE2 | 309 | |------|..... PW.Seg't2....X....PW.Seg't4.....|-------| | 310 +----+ | | |===========| |==========| | | +----+ 311 Base ^ +----+ +-----+ +----+ ^ 312 Station | Provider Edge 1 ^ Provider Edge 2 | 313 | ONU | | 314 | PW switching point | 315 | OLT | 316 | | 317 |<------------------ Emulated Service --------------->| 319 Figure B: MS-PW over PON Network Reference Model 321 Base ----AC-- TPE1--PW over PON--SPE1--PW over PSN--TPE2--AC------ 322 Station 323 ---------- ---------- 324 -------- |Packetized| |Packetized| -------- 325 |Native | |Native | |Native | |Native | 326 |Service | |Service | |Service | |Service | 327 -------- |----------| |----------| -------- 328 |Control | |Control | 329 |Word | |Word | 330 |----------| |----------| 331 |PW Label | |PW Label | 332 |----------| |----------| 333 |GEM/XGEM | |MPLS | 334 |----------| |Tunnel | 335 |GPON/XGPON| |Label | 336 |-Phy | | | 337 ---------- |----------| 338 |Link Layer| 339 |----------| 340 |Phy | 341 ---------- 343 Figure C: On-Wire Data Encapsulations for MS-PWs 345 It should be noted that all PW segments are of the same technology, 346 which is packet encapsulated. 348 The use of the PW label enables multiple PWs to multiplexed over a 349 single GEM/XGEM port within the MPLS LSP tunnel. This enables the 350 traffic for multiple base stations to be kept separate, and allows 351 different services and separate ACs for a single base station to be 352 supported. Furthermore, the multiple ACs at an ONU can belong to 353 different native services. 355 At the same time, each ONU can support more than one GEM/XGEM port 356 (each supporting a single MPLS LSP tunnel) connecting it to the OLT. 357 This allows greater bandwidth and so more PWs. It may also be used 358 to provide a simple way to aggregate PWs intended to be routed across 359 different PSN tunnels in the core network, or even across different 360 core networks. 362 At present, Ethernet over GEM/XGEM is the dominant encapsulation in 363 G-PON/XG-PON. For fast deployment of MPLS over G-PON/XG-PON, putting 364 MPLS PWs over Ethernet over GEM/XGEM is an alternative way of 365 transporting MPLS PWs over G-PON/XG-PON with existing hardware. 367 4. Label Provisioning for Pseudowires over PON 369 For a MS-PW with a segment running over a PON, where the OLT acts as 370 a S-PE and the ONU as a T-PE, PW provisioning can be performed 371 through static configuration, e.g., from an NMS. However, in this 372 model, each ONU has to be configured as each PW is set up. The huge 373 number of ONUs (and PWs) makes this method quite forbidding. 375 The labor of provisioning static labels at the ONUs for PWs can be 376 significantly reduced by using a management protocol over PON. This 377 approach keeps the ONU simple by not requiring the implementation of 378 a new dynamic control protocol. 380 The usual management protocol in a G-PON/XG-PON system used to manage 381 and control ONUs is OMCI. It is used to perform all G-PON/XG-PON 382 physical layer and data GTC/XGTC layer configuration on ONUs. Per 383 [G.984.4amd2] and [G.988], OMCI can also be used to set up PWs and 384 the MPLS LSP Tunnels from ONUs to OLT. When using OMCI to provision 385 PWs in a G-PON/XG-PON, the network manager sends configuration 386 information to the OLT only. The OLT will select suitable PW labels 387 and send all PW and MPLS LSP tunnel parameters to the ONUs through 388 OMCI. The AC can be identified in the OMCI signaling so that the 389 network manager does not need to configure the PWs at each ONU. 391 OMCI supports the configuration of a number of PW types including 392 TDM, ATM, and Ethernet. The protocol can also be used to allow the 393 ONU to notify the OLT of the status of the AC. 395 5. IANA Considerations 397 This document makes no request for IANA action. 399 6. Security Considerations 401 This document describes a variation of a multi-segment pseudowire 402 running over an MPLS PSN, in which one or both of the MPLS PSNs that 403 provide connectivity between a T-PE and its associated S-PE is 404 replaced by a G-PON/XG-PON PSN. The security considerations that 405 apply to the PW itself [RFC3985] [RFC4385] are unchanged by this 406 change in PSN type. For further considerations of PW security see 407 the security considerations section of the specific PW type being 408 deployed. 410 G-PON/XG-PON [G.987.3] [G.984.3] includes security mechanisms that 411 are as good as those provided in a well secured MPLS PSN. The use of 412 a G-PON/XG-PON PSN in place of an MPLS PSN therefore does not 413 increase the security risk of a multi-segment pseudowire. 415 Protecting against an attack at the physical or data link layer of 416 the PON is out of the scope of this document. 418 7. References 420 7.1. Normative References 422 [G.984.1] ITU-T, "Gigabit-capable passive optical networks (GPON): 423 General characteristics", March 2008, 424 . 426 [G.984.3amd1] 427 ITU-T, "Gigabit-capable Passive Optical Networks (G-PON): 428 Transmission convergence layer specification", 429 February 2009, 430 . 432 [G.987] ITU-T, "10-Gigabit-capable passive optical network (XG- 433 PON) systems: Definitions, abbreviations, and acronyms", 434 October 2010, 435 . 437 [G.987.3] ITU-T, "10-Gigabit-capable passive optical networks (XG- 438 PON): Transmission convergence (TC) specifications", 439 October 2010, 440 . 442 [G.988] ITU-T, "ONU management and control interface (OMCI) 443 specification", 2010, 444 . 446 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 447 Label Switching Architecture", January 2001. 449 [RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to- 450 Edge (PWE3) Architecture", March 2005. 452 [RFC4447] Rosen, E., El-Aawar, N., Smith, T., and G. Heron, 453 "Pseudowire Setup and Maintenance Using the Label 454 Distribution Protocol (LDP)", April 2006. 456 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP 457 Specification", October 2007. 459 [RFC5254] Bitar, N., Bocci, M., and L. Martini, "Requirements for 460 Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)", 461 October 2008. 463 [RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi- 464 Segment Pseudowire Emulation Edge-to-Edge", October 2009. 466 7.2. Informative References 468 [G.984.4amd2] 469 ITU-T, "Gigabit-capable passive optical networks (G-PON): 470 ONT management and control interface specification", 471 November 2009, 472 . 474 [RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. 475 Aissaoui , "Segmented Pseudowire", January 2011. 477 Authors' Addresses 479 Hongyu Li 480 Huawei Technologies 481 Huawei Industrial Base 482 Shenzhen 483 China 485 Email: hongyu.lihongyu@huawei.com 487 Ruobin Zheng 488 Huawei Technologies 489 Huawei Industrial Base 490 Shenzhen 491 China 493 Email: robin@huawei.com 495 Adrian Farrel 496 Old Dog Consulting 498 Email: adrian@olddog.co.uk