idnits 2.17.00 (12 Aug 2021) /tmp/idnits60853/draft-malis-pwe3-sonet-03.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** Looks like you're using RFC 2026 boilerplate. This must be updated to follow RFC 3978/3979, as updated by RFC 4748. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- == No 'Intended status' indicated for this document; assuming Proposed Standard Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) ** The document seems to lack separate sections for Informative/Normative References. All references will be assumed normative when checking for downward references. ** The abstract seems to contain references ([PWE3-FW], [PWE3-REQ]), which it shouldn't. Please replace those with straight textual mentions of the documents in question. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year == Line 1062 has weird spacing: '...vals if neces...' -- The exact meaning of the all-uppercase expression 'MAY NOT' is not defined in RFC 2119. If it is intended as a requirements expression, it should be rewritten using one of the combinations defined in RFC 2119; otherwise it should not be all-uppercase. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). Found 'MAY NOT' in this paragraph: As discussed in section 6, a CEP de-packetizer MAY or MAY NOT support re-ordering of mis-ordered packets. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (June 2002) is 7273 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFC 2119' is mentioned on line 80, but not defined == Missing Reference: 'CEP-VT' is mentioned on line 121, but not defined == Missing Reference: 'RTP-TYPES' is mentioned on line 439, but not defined -- Looks like a reference, but probably isn't: '481' on line 837 == Missing Reference: '485v2' is mentioned on line 844, but not defined == Missing Reference: 'GR-253' is mentioned on line 1076, but not defined == Unused Reference: 'RFC2119' is defined on line 1148, but no explicit reference was found in the text == Unused Reference: 'CES-VT' is defined on line 1191, but no explicit reference was found in the text == Outdated reference: draft-ietf-pwe3-requirements has been published as RFC 3916 ** Downref: Normative reference to an Informational draft: draft-ietf-pwe3-requirements (ref. 'PWE3-REQ') == Outdated reference: A later version (-01) exists of draft-ietf-pwe3-framework-00 -- Possible downref: Normative reference to a draft: ref. 'PWE3-FW' -- Possible downref: Non-RFC (?) normative reference: ref. 'PWE3-LAYERS' -- Possible downref: Non-RFC (?) normative reference: ref. 'SONET' -- Possible downref: Non-RFC (?) normative reference: ref. 'GR253' -- Possible downref: Non-RFC (?) normative reference: ref. 'G707' ** Obsolete normative reference: RFC 1889 (Obsoleted by RFC 3550) == Outdated reference: draft-ietf-rohc-rtp-lla has been published as RFC 3242 == Outdated reference: draft-malis-sonet-ces-mpls has been published as RFC 5143 ** Downref: Normative reference to an Historic draft: draft-malis-sonet-ces-mpls (ref. 'CEM') -- Possible downref: Normative reference to a draft: ref. 'CEM-MIB' == Outdated reference: draft-martini-l2circuit-trans-mpls has been published as RFC 4906 ** Downref: Normative reference to an Historic draft: draft-martini-l2circuit-trans-mpls (ref. 'MARTINI-TRANS') == Outdated reference: draft-martini-l2circuit-encap-mpls has been published as RFC 4905 ** Downref: Normative reference to an Historic draft: draft-martini-l2circuit-encap-mpls (ref. 'MARTINI-ENCAP') == Outdated reference: A later version (-07) exists of draft-vainshtein-cesopsn-02 -- Possible downref: Normative reference to a draft: ref. 'CESoPSN' -- Possible downref: Normative reference to a draft: ref. 'CES-VT' -- Possible downref: Non-RFC (?) normative reference: ref. 'AAL1' Summary: 9 errors (**), 0 flaws (~~), 18 warnings (==), 13 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PWE3 Working Group Andrew G. Malis 3 Internet Draft Ken Hsu 4 Expiration Date: December 2002 Vivace Networks, Inc. 6 David Zelig Jeremy Brayley 7 Corrigent Systems, LTD. Steve Vogelsang 8 John Shirron 9 Jim Boyle Laurel Networks, Inc. 10 Protocol Driven Networks, Inc. 11 Luca Martini 12 Ron Cohen Craig White 13 Lycium Networks Level 3 Communications, LLC. 15 Prayson Pate Tom Johnson 16 Overture Networks, Inc. Marlene Drost 17 Ed Hallman 18 Litchfield Communications, Inc. 20 June 2002 22 SONET/SDH Circuit Emulation over Packet (CEP) 23 draft-malis-pwe3-sonet-03.txt 25 Status of this Memo 27 This document is an Internet-Draft and is in full conformance with 28 all provisions of section 10 of [RFC2026]. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF), its areas, and its working groups. Note that 32 other groups may also distribute working documents as Internet- 33 Drafts. 35 Internet-Drafts are draft documents valid for a maximum of six 36 months and may be updated, replaced, or obsoleted by other documents 37 at any time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 The list of current Internet-Drafts can be accessed at 41 http://www.ietf.org/ietf/1id-abstracts.txt. 43 The list of Internet-Draft Shadow Directories can be accessed at 44 http://www.ietf.org/shadow.html. 46 Abstract 48 Generic requirements and framework for Pseudo Wire Emulation Edge-to- 49 Edge (PWE3) have been described in [PWE3-REQ] and [PWE3-FW]. This 50 draft provides encapsulation formats and semantics for connecting 51 SONET/SDH edge networks through a packet network using IP or MPLS. 52 This basic application of SONET/SDH interworking will allow service 53 providers to take advantage of new technologies in the core in order to 54 provide traditional SONET/SDH services. 56 Table of Contents 58 1 Conventions used in this document 2 59 2 Introduction 2 60 3 Applicability Statement 3 61 4 Scope 5 62 5 CEP Encapsulation Format 7 63 6 CEP Operation 16 64 7 SONET/SDH Maintenance Signals 19 65 8 SONET/SDH Transport Timing 23 66 9 SONET/SDH Pointer Management 24 67 10 CEP Performance Monitors 25 68 11 Open Issues 27 69 12 Security Considerations 28 70 13 Intellectual Property Disclaimer 28 71 14 References 29 72 15 Acknowledgments 30 73 16 Author's Addresses 30 75 1 Conventions used in this document 77 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 78 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 79 document are to be interpreted as described in [RFC 2119]. 81 2 Introduction 83 This document describes a protocol that performs SONET Emulation 84 over a variety of Packet-Switched Networks (PSNs) as part of the 85 PWE3 Working Group. The document assumes that the reader is 86 familiar with the PWE3 terminology and concepts described in PWE3 87 requirements and framework documents [PWE3-REQ] and [PWE3-FW] as 88 well as the PWE3 Protocol Layering Model [PWE3-LAYERS]. The 89 protocol is titled "Circuit Emulation over Packet" (CEP). 91 The transmission system for circuit-oriented TDM signals is the 92 Synchronous Optical Network [SONET], [GR253] / Synchronous Digital 93 Hierarchy (SDH) [G707]. To support TDM traffic (which includes 94 voice, data, and private leased line services) PSNs must emulate the 95 circuit characteristics of SONET/SDH payloads. An RTP Header 96 [RFC1889] and a CEP Control Word are used to encapsulate the 97 SONET/SDH TDM signals for transmission over an arbitrary PSN. 99 This document also describes an optional extension to CEP called 100 Dynamic Bandwidth Allocation (DBA). This is a method for 101 dynamically reducing the bandwidth utilized by emulated SONET/SDH 102 circuits in the packet network. This bandwidth reduction is 103 accomplished by not sending the SONET/SDH payload through the packet 104 network under certain conditions such as AIS-P or STS SPE 105 Unequipped. 107 In addition, this document describes a technique for RTP header 108 compression/suppression based on [ROHC-LLA]. 110 This document is based on a previous document describing a method 111 for encapsulating SONET signals for carriage over MPLS networks 112 [CEM]. 114 This document is closely related to and references [MARTINI-TRANS], 115 which describes the control protocol methods used to signal the 116 usage of CEP, [MARTINI-ENCAP] which describes a related method of 117 encapsulating Layer 2 frames over MPLS and which shares the same 118 signaling, and [CEM-MIB] which describes a MIB for controlling and 119 observing CEM services. 121 This document is complimentary to [CESoPSN] and [CEP-VT] which 122 describe methods for transporting sub-STS-1 rate circuits in native 123 format or VT mapped respectively. 125 3 Applicability Statement 127 SONET/SDH Circuit Emulation over Packet (CEP) is an encapsulation 128 layer intended for emulating SONET/SDH circuits over a Packet 129 Switched Network. 131 This protocol provides a method for emulating the key elements of 132 traditional SONET/SDH SPE services across a packet-switched network. 133 Both large fixed-facility network operators and smaller network 134 operators using ad hoc facilities may use this service. 136 The protocol makes no assumptions as to the contents of the 137 SONET/SDH SPE, and therefore is applicable to SONET/SDH circuits 138 carrying any type of payload. 140 Because the protocol terminates the SONET/SDH section and line 141 before emulating the individual SPEs, the protocol allows the PSN to 142 operate as a distributed SONET/SDH cross-connect. 144 3.1 Fidelity of Emulated SONET/SDH SPE services 146 The protocol does not make any assumptions about the capabilities of 147 the underlying PSN. However, the fidelity of the emulated service 148 will be dependent on the characteristics of the underlying PSN. 150 Emulated SONET/SDH SPE services may differ from native SONET/SDH 151 services on the following parameters: SPE timing, service 152 reliability, end-to-end delay, and bit-error-rate. Each of these 153 parameters is discussed below. 155 Because of the rigorous synchronization requirements implied by 156 SONET/SDH services, it is expected that the protocol will most 157 commonly be deployed in situations where a common timing reference 158 is available at the PW end-points. Large network operators have 159 well-defined methods for distributing Stratum timing references 160 (such as BITS, SASE, or GPS). Using these references is the most 161 direct technique that can be mathematically proven to meet the 162 relevant network synchronization specifications. 164 However, smaller network operators or remote locations in larger 165 networks may not have access to a common reference either by design 166 or due to a persistent fault in the timing distribution network. In 167 the absence of common references adaptive timing recovery techniques 168 may be employed. However, the fidelity of the recovered SPE timing 169 will be dependent on the packet-delay variation behavior of the 170 underlying PSN and the robustness of the timing recovery algorithm 171 used. As a result, it may be difficult in these circumstances to 172 mathematically prove that the recovered SPE timing is in compliance 173 with relevant synchronization standards. 175 Service Reliability may be impacted by two components: the 176 robustness of the underlying PSN and whether specific steps have 177 been taken to protect the emulated service (such as 1+1 protection 178 switching on the emulated service). The jitter buffer and packet 179 reordering mechanisms associated with the protocol increase 180 resilience of the emulated service to fast PSN rerouting events. 182 End-to-end delay will be impacted by both the transit delay through 183 the PSN and the packet-delay-variation characteristics of the PSN. 184 The protocol makes no assumption regarding either of these 185 parameters. However, the tighter the bound on transit delay and 186 delay variation, the shorter the end-to-end delay of the emulated 187 circuit will be. 189 BER for emulated circuits will be dependent on the characteristics 190 of the PSN. Each packet dropped by the PSN will result in an 191 equivalent number of byte errors on the emulated SPE. Using smaller 192 packet sizes can reduce the effect of lost packets on the emulated 193 service but increases the ratio of overhead to payload. The 194 protocol allows flexibility in packet length to accommodate the 195 desired BER/Overhead working point. 197 To the extent possible, the use of low-loss paths (for example, by 198 reserving link bandwidth and router/switch buffering) in the PSN 199 will enhance the fidelity of the emulated circuits. 201 3.2 Performance Monitoring and Fault Isolation 203 The protocol allows collection of SONET/SDH-like faults and 204 performance monitoring parameters. Similarity with existing 205 SONET/SDH services is increased by the protocol's ability to carry 206 'far end error' indications (i.e. RDI). The protocol performance 207 monitoring capabilities are based on SONET/SDH requirements as 208 reflected by the available standards, and adapted to the nature of 209 the protocol. 211 The protocol provides the ability to detect lost packets and hence 212 allows it to distinguish between PSN problems and problems external 213 to the PSN as causes of outages and/or degradations of the emulated 214 service. In addition, the protocol supports fast detection of 215 defects, enabling vendors to implement rapid fault recovery 216 mechanisms for the emulated circuit. 218 3.3 Other Considerations 220 The protocol allows for bandwidth conservation in the PSN by 221 carrying only AIS-P and/or STS SPE Unequipped indications instead of 222 empty payloads, thus providing for efficiency gains on the PW. 223 Additional payload conservation techniques may be defined in the 224 future. 226 Being a constant bit rate (CBR) service, the protocol cannot provide 227 TCP-friendly behavior under network congestion. It will operate 228 best in environments where the Diff-Serv EF PHB with allocated 229 bandwidth is available end-to-end between the PW endpoints and the 230 EF bandwidth is sized to meet the requirements of the emulated 231 SONET/SDH circuits, or over a well engineered path as available 232 through the relevant signaling protocols like RSVP-TE and CR-LDP for 233 MPLS PSNs. Using these methods will prevent contention between the 234 SONET Emulation protocol and TCP traffic. Unusable service 235 characteristics from the packet switched network may be used to 236 trigger circuit/PW teardown or switch-over. 238 4 Scope 240 This document describes how to provide CEP for the following digital 241 signals: 243 1. SONET STS-1 synchronous payload envelope (SPE)/SDH VC-3 244 2. STS-Nc SPE (N = 3, 12, 48, or 192)/SDH VC-4, VC-4-4c, VC-4-16c, 245 or VC-4-64c 247 For the remainder of this document, these constructs will be 248 referred to as SONET/SDH channels. 250 Although this document currently covers up to OC-192c/VC-4-64c, 251 future revision MAY address higher rates. 253 Other SONET/SDH signals, such as virtual tributary (VT) structured 254 sub-rate mapping, are not explicitly discussed in this document; 255 however, it can be extended in the future to support VT and lower 256 speed non-SONET/SDH services. 258 5 CEP Encapsulation Format 260 In order to transport SONET/SDH SPEs through a packet-oriented 261 network, the SPE is broken into fragments. A CEP Header is pre- 262 pended to each fragment. The resulting packet is encapsulated in 263 RTP for transmission over an arbitrary PSN. 265 (Note: under certain circumstances the RTP header may be suppressed 266 to conserve network bandwidth. See section 5.4.3 for details). 268 The basic CEP packet appears in Figure 1. 270 +-----------------------------------+ 271 | PSN and Multiplexing Layer | 272 | Headers | 273 +-----------------------------------+ 274 | RTP Header | 275 | (RFC1889) | 276 +-----------------------------------+ 277 | CEP Header | 278 +-----------------------------------+ 279 | | 280 | | 281 | SONET/SDH SPE Fragment | 282 | | 283 | | 284 +-----------------------------------+ 286 Figure 1 - Basic CEP Packet 288 5.1 SONET/SDH SPE Fragment 290 The SONET/SDH Fragments MUST be byte aligned with the SONET/SDH SPE. 292 The first bit received from each byte of the SONET/SDH SPE MUST be 293 the Most Significant Bit of each byte in the SONET/SDH SPE fragment. 295 SONET/SDH bytes are placed into the SONET/SDH fragment in the same 296 order in which they are received. 298 SONET/SDH optical interfaces use binary coding and therefore are 299 scrambled prior to transmission to insure an adequate number of 300 transitions. For clarity, this scrambling will be referred to as 301 physical layer scrambling/descrambling. 303 In addition, many payload formats (such as for ATM and HDLC) include 304 an additional layer of scrambling to provide protection against 305 transition density violations within the SPEs. This function will 306 be referred to as payload scrambling/descrambling. 308 CEP assumes that physical layer scrambling/descrambling occurs as 309 part of the SONET/SDH section/line termination Native Service 310 Processing (NSP) functions. 312 However, CEP makes no assumption about payload scrambling. The 313 SONET/SDH SPE fragments MUST be constructed without knowledge or 314 processing of any incidental payload scrambling. 316 5.2 CEP Header 318 The CEP Header supports a basic and extended mode. The Basic CEP 319 Header provides the minimum functionality necessary to accurately 320 emulate a TDM SONET over a PSN if a common reference is available at 321 both ends of the PW. 323 Enhanced functionality and commonality with other real-time Internet 324 applications is provided by RTP encapsulation. 326 Bit 0 of the first 32-bit CEP header indicates whether or not the 327 extended header is present. When this bit is 0, then no extended 328 header is present. When this bit is 1, then an extended header is 329 present. At this time, the contents of the extended header are for 330 future study. However, it is expected that this field will provide 331 support for payload compression, header protection, enhanced 332 performance monitoring, and/or other extensions to the base 333 protocol. 335 The Basic CEP header has the following format: 337 0 1 2 3 338 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 2 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 |0|R|D|N|P| Structure Pointer[0:12] | Sequence Number[0:13] | 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 343 Figure 2 - Basic CEP Header Format 345 The Extended CEP header appears below: 347 0 1 2 3 348 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 2 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 |1|R|D|N|P| Structure Pointer[0:12] | Sequence Number[0:13] | 351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 352 | Reserved | 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 Figure 3 - Extended CEP Header Format 357 The above fields are defined as follows: 359 R bit: CEP-RDI. This bit is set to one to signal to the remote CEP 360 function that a loss of packet synchronization has occurred. See 361 section 6.4 for details. 363 D bit: Signals DBA Mode. MUST be set to zero for Normal Operation. 364 MUST be set to one if CEP is currently in DBA mode. DBA is an 365 optional mode during which trivial SPEs are not transmitted into the 366 packet network. See Table 1 and section 6 for further details. 368 The N and P bits: MAY be used to explicitly relay negative and 369 positive pointer adjustment events across the PSN. They are also 370 used to relay SONET/SDH maintenance signals such as AIS-P. See 371 Table 1 and sections 7 and 9 for more details. 373 +---+---+---+----------------------------------------------+ 374 | D | N | P | Interpretation | 375 +---+---+---+----------------------------------------------+ 376 | 0 | 0 | 0 | Normal Mode - No Ptr Adjustment | 377 | 0 | 0 | 1 | Normal Mode - Positive Ptr Adjustment | 378 | 0 | 1 | 0 | Normal Mode - Negative Ptr Adjustment | 379 | 0 | 1 | 1 | Normal Mode - AIS-P | 380 | | | | | 381 | 1 | 0 | 0 | DBA Mode - STS SPE Unequipped | 382 | 1 | 0 | 1 | DBA Mode - STS SPE Unequipped Pos Ptr Adj | 383 | 1 | 1 | 0 | DBA Mode - STS SPE Unequipped Neg Ptr Adj | 384 | 1 | 1 | 1 | DBA Mode - AIS-P | 385 +---+---+---+----------------------------------------------+ 387 Table 1. Interpretation of D, N, and P bits 389 Sequence Number[0:13]: This is a packet sequence number, which MUST 390 continuously cycle from 0 to 0x3FFF. It is generated and processed 391 in accordance with the rules established in [RFC1889]. When the RTP 392 header is used, this sequence number MUST match the LSBs of the RTP 393 sequence Number. 395 Structure Pointer[0:12]: The Structure Pointer MUST contain the 396 offset of the J1 byte within the CEP SPE Fragment. The value is 397 from 0 to 0x1FFE, where 0 means the first byte after the CEP header. 398 The Structure Pointer MUST be set to 0x1FFF if a packet does not 399 carry the J1 byte. See [SONET], [GR253], and [G707] for more 400 information on the J1 byte and the SONET/SDH payload pointer. 401 Implementations MUST support SPE Fragments of 783 bytes and MAY 402 support SPE fragments of from 8 to 8191 bytes. 404 Note 1: Implementations that choose to support programmable payload 405 lengths SHOULD support payloads that are an integer multiple of 8 406 bytes. 408 Note 2: CEP packets are fixed in length for all of the packets of a 409 particular emulated TDM stream. This length is statically 410 provisioned for each TDM stream. Therefore, the length of each CEP 411 packet does not need to be carried in the CEP header. 413 5.3 RTP Header 415 CEP uses the fixed RTP Header as shown below. 417 0 1 2 3 418 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 1 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 |V=2|P|X| CC |M| PT | sequence number | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 422 | timestamp | 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 424 | synchronization source (SSRC) identifier | 425 +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ 427 o V (version) is always set to 2 429 o P (padding) is always set to 0 431 o X (header extension) is always set to 0 433 o CC (CSRC count) is always set to 0 435 o M (marker) is set to 0 for CEP packets. 437 o PT (payload type) is used to identify packets carrying the 438 packetized SONET/SDH data. One PT value should be allocated from 439 the range of dynamic values (see [RTP-TYPES]) for every CEP PW. 440 Allocation is done during the PW setup and MUST be the same for both 441 PW directions. The PE at the PW ingress MUST set the PT value in the 442 RTP header to the allocated value. 444 o Sequence Number is used primarily to provide the common PW 445 sequencing function as well as detection of lost packets. It is 446 generated and processed in accordance with the rules established in 447 [RFC1889]. 449 o Timestamp is used primarily for carrying timing information over 450 the network. Their values are used in accordance with the rules 451 established in [RFC1889]. Frequency of the clock used for 452 generating timestamps MUST be 19.44 MHz based on a local reference. 454 O SSRC (synchronization source) value in the RTP header MAY be used 455 for detection of misconnections. 457 5.4 PSN Encapsulation 459 In principle, CEP packets can be carried over any packet-oriented 460 network. The following sections describe specifically how CEP 461 packets MUST be encapsulated for carriage over MPLS or IP networks. 463 5.4.1 IP Encapsulation 465 CEP uses the standard IP/UDP/RTP encapsulation scheme as shown 466 below. The UDP destination port MUST be used to Demultiplex 467 individual SONET channels. 469 +-----------------------------------+ 470 | | 471 | IPv6/v4 Header | 472 | | 473 +-----------------------------------+ 474 | UDP Header | 475 +-----------------------------------+ 476 | RTP Header | 477 +-----------------------------------+ 478 | CEP Header | 479 +-----------------------------------+ 480 | | 481 | | 482 | SONET/SDH SPE Fragment | 483 | | 484 | | 485 +-----------------------------------+ 487 Figure 4 - IP Transport Encapsulation 489 5.4.2 MPLS Encapsulation 491 RTP MAY be directly encapsulated in MPLS as shown below. To 492 transport a CEP packet over an MPLS network, an MPLS label-stack 493 MUST be pushed on top of the CEP packet. The bottom label in the 494 MPLS label stack MUST be used to demultiplex individual SONET 495 channels. In keeping with the conventions used in [MARTINI-TRANS], 496 this demultiplexing label is referred to as the VC Label and the 497 upper labels are referred to as Tunnel Labels. 499 +-----------------------------------+ 500 | One or more MPLS Tunnel Labels | 501 +-----------------------------------+ 502 | VC Label | 503 +-----------------------------------+ 504 | RTP Header | 505 +-----------------------------------+ 506 | CEP Header | 507 +-----------------------------------+ 508 | | 509 | | 510 | SONET/SDH SPE Fragment | 511 | | 512 | | 513 +-----------------------------------+ 515 Figure 5 - Typical MPLS Transport Encapsulation 517 5.4.3 RTP Header Suppression 519 In addition to normal RTP header compression mechanisms as described 520 in [RFC2508] and [RFC3095], an additional option may be used in CEP 521 which suppresses transmission of the RTP header altogether. 523 This mode may be used when both SONET Emulation PEs have access to a 524 common reference clock and both support RTP Header Suppression. 525 Under these conditions the following encapsulation formats may be 526 used. 528 The choice to utilize RTP Header Suppression may be statically 529 configured using [CEM-MIB], or signaled using a PW maintenance 530 protocol such as [MARTINI-TRANS]. 532 +-----------------------------------+ 533 | | 534 | IPv6/v4 Header | 535 | | 536 +-----------------------------------+ 537 | UDP Header | 538 +-----------------------------------+ 539 | CEP Header | 540 +-----------------------------------+ 541 | | 542 | | 543 | SONET/SDH SPE Fragment | 544 | | 545 | | 546 +-----------------------------------+ 548 Figure 6 - IP Transport Encapsulation w/ RTP Header Suppression 549 +-----------------------------------+ 550 | One or more MPLS Tunnel Labels | 551 +-----------------------------------+ 552 | VC Label | 553 +-----------------------------------+ 554 | CEP Header | 555 +-----------------------------------+ 556 | | 557 | | 558 | SONET/SDH SPE Fragment | 559 | | 560 | | 561 +-----------------------------------+ 563 Figure 7 - MPLS Transport Encapsulation w/ RTP Header Suppression 565 5.5 L2TP Encapsulation 567 Encapsulation for L2TP PSNs is for future study. 569 6 CEP Operation 571 The following sections describe CEP operation. 573 6.1 Introduction and Terminology 575 CEP MUST support a normal mode of operation and MAY support an 576 optional extension called Dynamic Bandwidth Allocation (DBA). 577 During normal operation, SONET/SDH payloads are fragmented, pre- 578 pended with the appropriate headers and then transmitted into the 579 packet network. During DBA mode, only the headers are transmitted. 580 This is done to conserve bandwidth when meaningful user data is not 581 present in the SPE, such as during AIS-P or STS SPE Unequipped. 583 6.1.1 CEP Packetizer and De-Packetizer 585 As with all adaptation functions, CEP has two distinct components: 586 adapting TDM SONET/SDH into a CEP packet stream, and converting the 587 CEP packet stream back into a TDM SONET/SDH. The first function 588 will be referred to as CEP Packetizer and the second as CEP De- 589 Packetizer. This terminology is illustrated in Figure 8. 591 +------------+ +---------------+ 592 | | | | 593 SONET --> | CEP | --> PSN --> | CEP | --> SONET 594 SDH | Packetizer | | De-Packetizer | SDH 595 | | | | 596 +------------+ +---------------+ 598 Figure 8 - CEP Terminology 600 Note: the CEP de-packetizer requires a buffering mechanism to 601 account for delay variation in the CEP packet stream. This 602 buffering mechanism will be generically referred to as the CEP 603 jitter buffer. 605 6.1.2 CEP DBA 607 DBA is an optional mode of operation that only transmits the headers 608 into the packet network under certain circumstances such as AIS-P or 609 STS Unequipped. 611 If DBA is supported by a CEP implementation, the user SHOULD be able 612 to configure if DBA will be triggered by AIS-P, STS Unequipped, 613 both, or neither on a per channel basis. 615 If DBA is supported, the determination of AIS-P and STS Unequipped 616 MUST be based on the state of SONET/SDH Section, Line, and Path 617 Overhead bytes. 619 During AIS-P, there is no valid payload pointer, so pointer 620 adjustments cannot occur. During STS Unequipped, the SONET/SDH 621 payload pointer is valid, and therefore pointer adjustments MUST be 622 supported even during DBA. See Table 1 for details. 624 6.2 Description of Normal CEP Operation 626 During normal operation, the CEP packetizer will receive a fixed 627 rate byte stream from a SONET/SDH interface. When a packets worth 628 of data has been received from a SONET/SDH channel, the necessary 629 headers are pre-pended to the SPE fragment and the resulting CEP 630 packet is transmitted into the packet network. Because all CEP 631 packets associated with a specific SONET/SDH channel will have the 632 same length, the transmission of CEP packets for that channel SHOULD 633 occur at regular intervals. 635 At the far end of the packet network, the CEP de-packetizer will 636 receive packets into a jitter buffer and then play out the received 637 byte stream at a fixed rate onto the corresponding SONET/SDH 638 channel. The jitter buffer SHOULD be adjustable in length to 639 account for varying network delay behavior. The receive packet rate 640 from the packet network should be exactly balanced by the 641 transmission rate onto the SONET/SDH channel, on average. The time 642 over which this average is taken corresponds to the depth of the 643 jitter buffer for a specific CEP channel. 645 The RTP sequence numbers provide a mechanism to detect lost and/or 646 mis-ordered packets. The sequence number in the CEP header may be 647 used when transmission of the RTP header is suppressed (see section 648 5.4.3 for details). The CEP de-packetizer MUST detect lost or mis- 649 ordered packets. The CEP de-packetizer SHOULD play out an all ones 650 pattern (AIS) in place of any dropped packets. The CEP de- 651 packetizer MAY re-order packets received out of order. If the CEP 652 de-packetizer does not support re-ordering, it must drop mis-ordered 653 packets. 655 6.3 Description of CEP Operation during DBA 657 There are several issues that should be addressed by a workable CEP 658 DBA mechanism. First, when DBA is invoked, there should be a 659 substantial savings in bandwidth utilization in the packet network. 660 The second issue is that the transition in and out of DBA should be 661 tightly coordinated between the local CEP packetizer and CEP de- 662 packetizer at the far side of the packet network. A third is that 663 the transition in and out of DBA should be accomplished with minimal 664 disruption to the adapted data stream. 666 Another goal is that the reduction of CEP traffic due to DBA should 667 not be mistaken for a fault in the packet network or vice-versa. 668 Finally, the implementation of DBA should require minimal 669 modifications beyond what is necessary for the nominal CEP case. 670 The mechanism described below is a reasonable balance of these 671 goals. 673 During DBA, packets MUST be emitted at exactly the same rate as they 674 would be during normal operation. This SHOULD be accomplished by 675 transmitting each DBA packet after a complete packet of data has 676 been received from the SONET/SDH channel. The only change from 677 normal operation is that the CEP packets during DBA MUST only 678 suppress the transmission of the SPE while still sending the 679 appropriate headers. Because some links have a minimum supported 680 packet size, the CEP packetizer MAY append a configurable number of 681 bytes immediately after the CEP header to pad out the CEP packet to 682 reach the mimumum supported packet size. The D-bit MUST be set to 683 one, to indicate that DBA is active. 685 The CEP de-packetizer MUST assume that each packet received with the 686 D-bit set represents a normal-sized packet containing an AIS-P or 687 SPE Unequipped payload as noted by N and P. See Table 1. The CEP 688 de-packetizer MUST accept DBA packets with or without padding. 690 This allows the CEP packetization and de-packetization logic during 691 DBA to be similar to the nominal case. It ensures that the correct 692 SONET/SDH indication is reliably transmitted between CEP adaptation 693 points. It minimizes the risk of under or over running the jitter 694 buffer during the transition in and out of DBA, since packets are 695 continuously transmitted during DBA. And, it guarantees that faults 696 in the packet network are recognized as distinctly different from 697 line conditioning on the SONET/SDH interfaces. 699 6.4 Packet Synchronization 701 A key component in declaring the state of a CEP service is whether 702 or not the CEP de-packetizer is in or out of packet synchronization. 703 The following paragraphs describe how that determination is made. 705 As discussed in section 6, a CEP de-packetizer MAY or MAY NOT 706 support re-ordering of mis-ordered packets. 708 As packets are received from the PSN, they are placed into a jitter 709 buffer prior to play out on the SONET interface. If a CEP de- 710 packetizer supports re-ordering, any packet received before its play 711 out time will still be considered valid. 713 If a CEP de-packetizer does not support re-ordering, a number of 714 approaches may be used to minimize the impact of mis-ordered or lost 715 packets on the final re-assembled SONET stream. For example, [AAL1] 716 uses a simple state-machine to re-order packets in a sub-set of 717 possible cases. 719 However, the final determination as to whether or not to declare 720 acquisition or loss of packet synchronization MUST be based on the 721 same criteria regardless of whether an implementation supports or 722 does not support re-ordering. 724 Therefore, the determination of acquisition or loss of packet 725 synchronization is always made at SONET play-out time. During SONET 726 play-out, the CEP de-packetizer will play received CEP packets onto 727 the SONET interface. However, if the jitter buffer is empty or the 728 packet to be played out has not been received, the CEP de-packetizer 729 will play out an empty packet onto the SONET interface in place of 730 the unavailable packet. 732 The acquisition of packet synch is based on the number of sequential 733 CEP packets that are played onto the SONET interface. While, loss 734 of packet synch is based on the number of sequential 'empty' packets 735 that are played onto the SONET interface. Specific details of these 736 two cases is described below. 738 6.4.1 Acquisition of Packet Synchronization 740 At startup, a CEP de-packetizer will be out of packet 741 synchronization by default. To declare packet synchronization at 742 startup or after a loss of packet synchronization, the CEP de- 743 packetizer must play-out a configurable number of CEP packets with 744 sequential sequence numbers towards the SONET interface. 746 6.4.2 Loss of Packet Synchronization 748 Once a CEP de-packetizer is in packet sync, it may encounter a set 749 of events that will cause it to lose packet synchronization. 751 If the CEP de-packetizer encounters more than a configurable number 752 of sequential empty packets, the CEP de-packetizer MUST declare loss 753 of packet synchronization (LOPS) defect. 755 Loss of Packet Synchronization (LOPS) failure is declared after 2.5 756 +/- 0.5 seconds of LOPS defect, and cleared after 10 seconds free of 757 LOPS defect state. The VC is considered down as long as LOPS failure 758 is declared. 760 7 SONET/SDH Maintenance Signals 762 There are several issues that must be considered in the mapping of 763 maintenance signals between SONET/SDH and a PSN. A description of 764 how these signals and conditions are mapped between the two domains 765 is described below. 767 For clarity, the mappings are split into two groups: SONET/SDH to 768 PSN, and PSN to SONET/SDH. 770 7.1 SONET/SDH to PSN 771 The following sections describe how SONET/SDH Maintenance Signals 772 and Alarm conditions are mapped into a Packet Switched Network. 774 7.1.1 AIS-P Indication 776 In a SONET/SDH network, SONET Path outages are signaled using 777 maintenance alarms such as Path AIS (AIS-P). In particular, AIS-P 778 indicates that the SONET/SDH Path is not currently transmitting 779 valid end-user data, and the SPE contains all ones. 781 It should be noted that nearly every type of service-affecting 782 section or line defect will result in an AIS-P condition. 784 The SONET/SDH hierarchy is illustrated below. 786 +----------+ 787 | PATH | 788 +----------+ 789 ^ 790 | 791 AIS-P 792 | 793 | 794 +----------+ 795 | LINE | 796 + ---------+ 797 ^ ^ 798 | | 799 AIS-L +------ LOP 800 | 801 | 802 +----------+ 803 | SECTION | 804 +----------+ 805 ^ ^ 806 | | 807 | | 808 LOS LOF 810 Figure 9 - SONET/SDH Fault Hierarchy 812 Should the Section Layer detect a Loss of Signal (LOS) or Loss of 813 Frame (LOF) condition, it sends AIS-L up to the Line Layer. If the 814 Line Layer detects AIS-L or Loss of Path (LOP), it sends AIS-P to 815 the Path Layer. 817 In normal mode during AIS-P, CEP packets are generated as usual. 818 The N and P bits MUST be set to 11 binary to signal AIS-P explicitly 819 through the packet network. The D-bit MUST be set to zero to 820 indicate that the SPE is being carried through the packet network. 821 Normal CEP packets with the SPE fragment, CEP Header, the Circuit ID 822 Word, and PSN Header MUST be transmitted into the packet network. 824 However, to conserve network bandwidth during AIS-P, DBA MAY be 825 employed. If DBA has been enabled for AIS-P and AIS-P is currently 826 occurring, the N and P bits MUST be set to 11 binary to signal AIS, 827 and the D-bit MUST be set to one to indicate that the SPE is not 828 being carried through the packet network. Only the CEP header, the 829 Circuit ID Word, and the PSN Header MUST be transmitted into the 830 packet network. 832 7.1.2 STS SPE Unequipped Indication 834 The declaration of STS SPE unequipped MUST conform to [GR253]. 835 Quoted below: 837 "R6-135 [481] STS PTE shall detect an STS Path Unequipped (UNEQ-P) 838 defect within 10 ms of the onset of at least five consecutive 839 samples (which may or may not be consecutive frames) of unequipped 840 STS Signal Labels (C2 byte), as specified in Table 6-2" 842 The termination of STS SPE unequipped MUST also conform to [GR253]. 844 "R6-137 [485v2] STS PTE shall terminate an UNEQ-P defect within 10 845 ms of the onset of at least five consecutive samples (which may or 846 may not be consecutive frames) of STS Signal Labels that are not 847 unequipped or all-ones, as specified in Table 6-2" 849 For normal operation during SPE Unequipped, the N and P bits MUST be 850 interpreted as usual. The SPE MUST be transmitted into the packet 851 network along with the appropriate headers, and the D-Bit MUST be 852 set to zero. 854 If DBA has been enabled for STS SPE Unequipped and the Unequipped is 855 occurring on the SONET/SDH channel, the D-bit MUST be set to one to 856 indicate DBA is active. Only the necessary headers are transmitted 857 into the packet network. The N and P bits MAY be used to signal 858 pointer adjustments as normal. See Table 1 and section 6 for 859 details. 861 7.1.3 CEP-RDI 863 The CEP function MUST send CEP-RDI towards the packet network during 864 loss of packet synchronization. This MUST be accomplished by 865 setting the R bit to one in the CEP header. 867 7.2 PSN to SONET/SDH 869 The following sections discuss how the various conditions on the 870 packet network are converted into SONET/SDH indications. 872 7.2.1 AIS-P Indication 873 There are several conditions in the packet network that will cause 874 the CEP de-packetization function to play out an AIS-P indication 875 towards a SONET/SDH channel. 877 The first of these is the receipt of CEP packets with the N and P 878 bits set to one, and the D-bit set to zero. This is an explicit 879 indication of AIS-P being received at the far-end of the packet 880 network, with DBA disabled for AIS-P. The CEP de-packetizer MUST 881 play out the received SPE fragment (which will incidentally be 882 carrying all ones), and MUST configure the SONET/SDH Overhead to 883 signal AIS-P as defined in [SONET], [GR253], and [G707]. 885 The second case is the receipt of CEP packets with the N and P bits 886 set to one, and the D-bit set to one. This indicates that AIS-P is 887 being received at the far-end of the packet network, with DBA 888 enabled for AIS-P. The CEP de-packetizer MUST play out one packet's 889 worth of all ones for each packet received, and MUST configure the 890 SONET/SDH Overhead to signal AIS-P as defined in [SONET], [GR253], 891 and [G707]. 893 A third case that will cause a CEP de-packetization function to play 894 out an AIS-P indication onto a SONET/SDH channel is during loss of 895 packet synchronization. The CEP de-packetizer MUST configure the 896 SONET/SDH Overhead to signal AIS-P as defined in [SONET], [GR253], 897 and [G707]. 899 7.2.2 STS SPE Unequipped Indication 901 There are three conditions in the packet network that will cause the 902 CEP function to transmit STS SPE Unequipped indications onto the 903 SONET/SDH channel. 905 The first, which is transparent to CEP, is the receipt of regular 906 CEP packets that happen to be carrying an SPE that contains the 907 appropriate Path overhead to signal STS SPE unequipped. This case 908 does not require any special processing on the part of the CEP de- 909 packetizer. 911 The second case is the receipt of CEP packets that have the D-bit 912 set to one to indicate DBA active and the N and P bits set to 00 913 binary, 01 binary, or 10 binary to indicate SPE Unequipped with or 914 without pointer adjustments. The CEP de-packetizer MUST use this 915 information to transmit a packet of all zeros onto the SONET/SDH 916 interface, and adjust the payload pointer as necessary. 918 The third case when a CEP de-packetizer MUST play out an STS SPE 919 Unequipped Indication towards the SONET interface is when the VC- 920 label has been withdrawn due to de-provisioning of the circuit. 922 8 SONET/SDH Transport Timing 923 It is assumed that the distribution of SONET/SDH Transport timing 924 information is addressed through external mechanisms such as 925 Building Integrated Timing System (BITS), Stand Alone 926 Synchronization Equipment (SASE), Global Positioning System (GPS) or 927 other such methods and is therefore outside of the scope of this 928 specification. 930 9 SONET/SDH Pointer Management 932 A pointer management system is defined as part of the definition of 933 SONET/SDH. Details on SONET/SDH pointer management can be found in 934 [SONET], [GR253], and [G707]. If there is a frequency offset 935 between the frame rate of the transport overhead and that of the 936 SONET/SDH SPE, then the alignment of the SPE shall periodically slip 937 back or advance in time through positive or negative stuffing. 939 The emulation of this aspect of SONET networks may be accomplished 940 using a variety of techniques including (but not limited to) 941 explicit pointer adjustment relay (EPAR) and adaptive pointer 942 management (APM). 944 In any case, the handling of the SPE data by the CEP packetizer is 945 the same. 947 During a negative pointer adjustment event, the CEP packetizer MUST 948 incorporate the H3 byte from the SONET/SDH stream into the CEP 949 packet payload in order with the rest of the SPE. During a positive 950 pointer adjustment event, the CEP de-packetizer MUST strip the stuff 951 byte from the CEP packet payload. 953 When playing out a negative pointer adjustment event, the 954 appropriate byte of the CEP payload MUST be placed into the H3 byte 955 of the SONET/SDH stream. When playing out a positive pointer 956 adjustment, the CEP de-packetizer MUST insert a stuff-byte into the 957 appropriate position within the SONET/SDH stream. 959 The details regarding the use of the H3 byte and stuff byte during 960 positive and negative pointer adjustments can be found in [SONET], 961 [GR253], and [G707]. 963 9.1 Explicit Pointer Adjustment Relay (EPAR) 965 CEP provides an OPTIONAL mechanism to explicitly relay pointer 966 adjustment events from one side of the PSN to the other. This 967 technique will be referred to as Explicit Pointer Adjustment Relay 968 (EPAR). The mechanics of EPAR are described below. 970 The following text only applies to implementations that choose to 971 implement EPAR. Any CEP implementation that does not support EPAR 972 MUST either set the N and P bits to zero or utilize them to relay 973 AIS-P and STS Unequipped as shown in table 1. 975 If EPAR is being used, the pointer adjustment event MUST be 976 transmitted in three consecutive packets by the packetizer. The de- 977 packetizer MUST play out the pointer adjustment event when any one 978 packet with N/P bit set is received. 980 References [SONET], [GR253], and [G707] specify that pointer 981 adjustment events MUST be separated by three SONET/SDH frames 982 without a pointer adjustment event. In order to explicitly relay 983 all legal pointer adjustment events, the packet size for a specific 984 circuit SHOULD be no larger than (783 * 4 * N)/3, where N is the 985 STS-Nc multiplier. 987 However, there are SONET implementations that allow pointer 988 adjustments to occur in back to back SONET/SDH frames. In order to 989 support this possibility, EPAR implementations SHOULD set the packet 990 size for a particular circuit to be no larger than (783*N)/3. Where 991 N is the STS-Nc multiplier. 993 Since the minimum value of N is one, EPAR implementations SHOULD 994 support a minimum payload length of 783/3 or 261 bytes. 996 For EPAR implementations, the CEP de-packetizer MUST utilize the CEP 997 sequence numbers to insure that SONET/SDH pointer adjustment events 998 are not played any more frequently than once per every three CEP 999 packets transmitted by the remote CEP packetizer. 1001 If both bits are set, then an AIS-P event has occurred (this is 1002 further discussed in section 7). 1004 When DBA is invoked (i.e. the D-bit = 1), N and P have additional 1005 meanings. See Table 1 and section 6. 1007 9.2 Adaptive Pointer Management (APM) 1009 Another OPTIONAL method that may be used to emulate SONET pointer 1010 management is Adaptive Pointer Management (APM). In basic terms, 1011 APM uses information about the depth of the CEP jitter buffers to 1012 introduce pointer adjustments in the reassembled SONET SPE. 1014 Details about specific APM algorithms is for future study. 1016 10 CEP Performance Monitors 1018 SONET/SDH as defined in [SONET], [GR253], and [G707] includes the 1019 definition of several counters that may be used to monitor the 1020 performance of SONET/SDH services. These counters are referred to 1021 as Performance Monitors. 1023 In order for CEP to be utilized by traditional SONET/SDH network 1024 operators, CEP SHOULD provide similar functionality. To this end, 1025 the following sections describe a number of counters that will 1026 collectively be referred to as CEP Performance Monitors. 1028 10.1 Near-End Performance Monitors 1030 These performance monitors are maintained by the CEP De-Packetizer 1031 during reassembly of the SONET stream. 1033 The performance monitors are based on two types of defects. 1035 Type 1 defect is defined as: missing or dropped packet. 1036 Type 2 defect is defined as: buffer under run, buffer over-run, 1037 LOPS. 1039 The specific performance monitors that are defined for CEP are as 1040 follows: 1042 ES-CEP - CEP Errored Seconds 1043 SES-CEP - CEP Severely Errored Seconds 1044 UAS-CEP - CEP Unavailable Seconds 1046 Each second that contain at least one type 1 defect SHALL be 1047 declared as ES-CEP. 1049 Each second that contain type 2 defect, or missing packets above 1050 pre-defined, configurable threshold of missing/dropped packets SHALL 1051 be declared both SES-CEP and ES-CEP. Default value for missing 1052 packet to SES is 3. 1054 UAS-CEP SHALL be declared after X consecutives SES-CEP, cleared 1055 after X consecutive seconds without SES-CEP. Default value of X is 1056 10 seconds. 1058 Once unavailability is declared, ES and SES counts SHALL be 1059 inhibited up to the point where the unavailability was started. Once 1060 unavailability is removed, ES that occurred along the X seconds 1061 clearing period SHALL be added to the ES counts. An update is 1062 required even for closed intervals if necessary. 1064 FC-CEP is the number of time type 1 or type 2 defect states were 1065 declared. The NE SHALL have thresholding on ES-CEP, SES-CEP and 1066 UAS-CEP (thresholding mean activate a notification if more than pre- 1067 defined # of seconds are declared as ES, etc. in 15 minutes 1068 interval). 1070 10.2 Far-End Performance Monitors 1072 These performance monitors provide insight into the CEM De- 1073 packetizer at the far-end of the PSN. 1075 Far end statistics are based on the RDI-CEP bit. Limited 1076 functionality is supported compared to [GR-253] for simplicity and 1077 because it is assumed that all relevant statistics are available 1078 from the end point of the PW. CEP-FE defect is declared when CEP-RDI 1079 is set in the incoming CEP packets. 1081 CEP-FE failure declared after 2.5 +/- 0.5 seconds of CEP-FE defect, 1082 and cleared after 10 seconds free of CES-FE defect state. Sending 1083 notification to the OS for CEP-FE failure is local policy. 1085 This draft does not attempt to define SES-CEPFE, UAS-CEPFE and FC- 1086 CEPFE, but they can be added if to fully emulate GR-253 far end PM 1087 (thresholding is required too here except for FC-CEPFE). (Note that 1088 ES-CEPFE is not relevant since CEP does not report back missing 1089 packets - only LOPS which is SES). 1091 The definition of additional performance monitors is for future 1092 study. 1094 11 Open Issues 1096 This version of the draft does not address payload compression 1097 within the emulated SONET. Payload compression is expected to be 1098 supported by future versions of this draft by utilizing the extended 1099 CEP header. 1101 This version of the draft does not tie into PWE3 maintenance 1102 mechanisms for the setup and tear down of services. That short- 1103 coming will be addressed in future revisions of this document. 1105 Underlying MPLS QoS requirements are not covered by this revision of 1106 the draft. Future revisions may discuss underlying QoS 1107 requirements. 1109 Support for VT and lower speed non-SONET/SDH services are not 1110 covered in this revision of the draft. Future revisions may address 1111 VT and non-SONET/SDH TDM services. 1113 An alternate version of DBA has been suggested that would suppress 1114 transmission of the entire CEP packet stream under certain 1115 circumstances. Future versions of this draft may define such a 1116 mechanism. 1118 It is possible to define SONET Emulation specific redundancy 1119 mechanisms, such as 1+1 or N:1. Future versions of this draft may 1120 define such mechanisms. 1122 12 Security Considerations 1124 This document does not address or modify security issues within the 1125 relevant PSNs. 1127 13 Intellectual Property Disclaimer 1129 This document is being submitted for use in IETF standards 1130 discussions. Vivace Networks, Inc. has filed one or more patent 1131 applications relating to the CEP technology outlined in this 1132 document. Vivace Networks, Inc. will grant free unlimited licenses 1133 for use of this technology. 1135 14 References 1137 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1138 3", BCP 9, RFC2026, October 1996. 1140 [PWE3-REQ] XiPeng Xiao et al, Requirements for Pseudo Wire Emulation 1141 Edge-to-Edge (PWE3), Work in Progress, July-2001, draft-ietf-pwe3- 1142 requirements-01.txt 1144 [PWE3-FW] Prayson Pate et al, Framework for Pseudo Wire Emulation 1145 Edge-to-Edge (PWE3), Work in progress, February 2002, draft-ietf- 1146 pwe3-framework-00.txt 1148 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1149 Requirement Levels", BCP 14, RFC 2119, March 1997. 1151 [PWE3-LAYERS], Stewart Bryant et al., Protocol Layering in PWE3, Work 1152 in Progress, February 2002, pwe3-protocol-layering-01.txt 1154 [SONET] American National Standards Institute, "Synchronous Optical 1155 Network (SONET) - Basic Description including Multiplex Structure, 1156 Rates and Formats," ANSI T1.105-1995. 1158 [GR253] Telcordia Technologies, "Synchronous Optical Network (SONET) 1159 Transport Systems: Common Generic Criteria", GR-253-CORE, Issue 3, 1160 September 2000. 1162 [G707] ITU Recommendation G.707, "Network Node Interface For The 1163 Synchronous Digital Hierarchy", 1996. 1165 [RFC1889] H. Schulzrinne et al, RTP: A Transport Protocol for Real- 1166 Time Applications, RFC 1889, IETF, 1996 1168 [ROHC-LLA] Lars-Eric Jonsson et al, A Link-Layer Assisted ROHC 1169 Profile for IP/UDP/RTP draft-ietf-rohc-rtp-lla-03.txt. 1171 [CEM] Malis et al, "SONET/SDH Circuit Emulation Service Over MPLS 1172 (CEM) Encapsulation", draft-malis-sonet-ces-mpls-05.txt, work in 1173 progress, July 2001. 1175 [CEM-MIB] Danenberg et al, "SONET/SDH Circuit Emulation Service Over 1176 PSN (CEP) Management Information Base Using SMIv2", draft-danenberg- 1177 pw-cem-mib-02.txt, work in progress, Feb 2002. 1179 [MARTINI-TRANS] Martini et al, "Transport of Layer 2 Frames Over 1180 MPLS", draft-martini-l2circuit-trans-mpls-06.txt, work in progress, 1181 July 2001. 1183 [MARTINI-ENCAP] Martini et al, "Encapsulation Methods for Transport 1184 of Layer 2 Frames Over MPLS", draft-martini-l2circuit-encap-mpls- 1185 02.txt, work in progress, July 2001. 1187 [CESoPSN] Vainshtein et al, "TDM Circuit Emulation Service over 1188 Packet Switched Network", draft-vainshtein-cesopsn-02.txt, work in 1189 progress, February 2002. 1191 [CES-VT] Pate et al, "TDM Service Specification for Pseudo-Wire 1192 Emulation Edge-to-Edge", draft-pate-pwe3-tdm-03.txt, work in 1193 progress, January 2001. 1195 [RFC2508] S.Casner, V.Jacobson, Compressing IP/UDP/RTP Headers for 1196 Low-Speed Serial Links, RFC 2508, IETF, 1999 1198 [RFC3095] C.Bormann (Ed.), RObust Header Compression (ROHC): 1199 Framework and four profiles: RTP, UDP, ESP, and uncompressed, RFC 1200 3095, IETF, 2001 1202 [AAL1] ITU-T, "Recommendation I.363.1, B-ISDN Adaptation Layer 1203 Specification: Type AAL1", Appendix III, August 1996. 1205 15 Acknowledgments 1207 The authors would like to thank all of the members of the PWE3 1208 working group who have contributed to the development of this draft, 1209 and specifically Danny McPherson and Allison Mankin for their advice 1210 and assistance. 1212 16 Author's Addresses 1214 Andrew G. Malis 1215 Vivace Networks, Inc. 1216 2730 Orchard Parkway 1217 San Jose, CA 95134 1218 Email: Andy.Malis@vivacenetworks.com 1220 Ken Hsu 1221 Vivace Networks, Inc. 1222 2730 Orchard Parkway 1223 San Jose, CA 95134 1224 Email: Ken.Hsu@vivacenetworks.com 1226 Jeremy Brayley 1227 Laurel Networks, Inc. 1228 2706 Nicholson Rd. 1229 Sewickley, PA 15143 1230 Email: jbrayley@laurelnetworks.com 1232 Steve Vogelsang 1233 Laurel Networks, Inc. 1234 2706 Nicholson Rd. 1235 Sewickley, PA 15143 1236 Email: sjv@laurelnetworks.com 1238 John Shirron 1239 Laurel Networks, Inc. 1240 2607 Nicholson Rd. 1241 Sewickley, PA 15143 1242 Email: jshirron@laurelnetworks.com 1244 Luca Martini 1245 Level 3 Communications, LLC. 1246 1025 Eldorado Blvd. 1247 Broomfield, CO 80021 1248 Email: luca@level3.net 1250 Tom Johnson 1251 Litchfield Communications, Inc. 1252 76 Westbury Park Rd. 1253 Watertown, CT 06795 1254 Email: tom_johnson@litchfieldcomm.com 1256 Ed Hallman 1257 Litchfield Communications, Inc. 1258 76 Westbury Park Rd. 1259 Watertown, CT 06795 1260 Email: ed_hallman@litchfieldcomm.com 1262 Marlene Drost 1263 Litchfield Communications, Inc. 1264 76 Westbury Park Rd. 1265 Watertown, CT 06795 1266 Email: marlene_drost@litchfieldcomm.com 1268 Jim Boyle 1269 Protocol Driven Networks, Inc. 1270 1381 Kildaire Farm #288 1271 Cary, NC 27511 1272 Email: jboyle@pdnets.com 1274 David Zelig 1275 Corrigent Systems LTD. 1276 126, Yigal Alon st. 1277 Tel Aviv, ISRAEL 1278 Email: davidz@corrigent.com 1280 Ron Cohen 1281 Lycium Networks 1282 Hamanofim 9, POB 12256 1283 Herzeliya, Israel 46733 1284 Email: ronc@lyciumnetworks.com 1286 Prayson Pate 1287 Overture Networks 1288 P. O. Box 14864 1289 RTP, NC, USA 27709 1290 Email: prayson.pate@overturenetworks.com 1292 Craig White 1293 Level3 Communications, LLC. 1294 1025 Eldorado Blvd, 1295 Broomfield CO 80021 1296 Email: Craig.White@Level3.com 1297 Appendix A. SONET/SDH Rates and Formats 1299 For simplicity, the discussion in this section uses SONET 1300 terminology, but it applies equally to SDH as well. SDH-equivalent 1301 terminology is shown in the tables. 1303 The basic SONET modular signal is the synchronous transport signal- 1304 level 1 (STS-1). A number of STS-1s may be multiplexed into higher- 1305 level signals denoted as STS-N, with N synchronous payload envelopes 1306 (SPEs). The optical counterpart of the STS-N is the Optical Carrier- 1307 level N, or OC-N. Table 2 lists standard SONET line rates discussed 1308 in this document. 1310 OC Level OC-1 OC-3 OC-12 OC-48 OC-192 1311 SDH Term - STM-1 STM-4 STM-16 STM-64 1312 Line Rate(Mb/s) 51.840 155.520 622.080 2,488.320 9,953.280 1314 Table 2. Standard SONET Line Rates 1316 Each SONET frame is 125 us and consists of nine rows. An STS-N frame 1317 has nine rows and N*90 columns. Of the N*90 columns, the first N*3 1318 columns are transport overhead and the other N*87 columns are SPEs. 1319 A number of STS-1s may also be linked together to form a super-rate 1320 signal with only one SPE. The optical super-rate signal is denoted 1321 as OC-Nc, which has a higher payload capacity than OC-N. 1323 The first 9-byte column of each SPE is the path overhead (POH) and 1324 the remaining columns form the payload capacity with fixed stuff 1325 (STS-Nc only). The fixed stuff, which is purely overhead, is N/3-1 1326 columns for STS-Nc. Thus, STS-1 and STS-3c do not have any fixed 1327 stuff, STS-12c has three columns of fixed stuff, and so on. 1329 The POH of an STS-1 or STS-Nc is always nine bytes in nine rows. The 1330 payload capacity of an STS-1 is 86 columns (774 bytes) per frame. 1331 The payload capacity of an STS-Nc is (N*87)-(N/3) columns per frame. 1332 Thus, the payload capacity of an STS-3c is (3*87 - 1)*9 = 2,340 1333 bytes per frame. As another example, the payload capacity of an STS- 1334 192c is 149,760 bytes, which is 64 times the capacity of an STS-3c. 1336 There are 8,000 SONET frames per second. Therefore, the SPE size, 1337 (POH plus payload capacity) of an STS-1 is 783*8*8,000 = 50.112 1338 Mb/s. The SPE size of a concatenated STS-3c is 2,349 bytes per frame 1339 or 150.336 Mb/s. The payload capacity of an STS-192c is 149,760 1340 bytes per frame, which is equivalent to 9,584.640 Mb/s. Table 2 1341 lists the SPE and payload rates supported. 1343 SONET STS Level STS-1 STS-3c STS-12c STS-48c STS-192c 1344 SDH VC Level - VC-4 VC-4-4c VC-4-16c VC-4-64c 1345 Payload Size(Bytes) 774 2,340 9,360 37,440 149,760 1346 Payload Rate(Mb/s) 49.536 149.760 599.040 2,396.160 9,584.640 1347 SPE Size(Bytes) 783 2,349 9,396 37,584 150,336 1348 SPE Rate(Mb/s) 50.112 150.336 601.344 2,405.376 9,621.504 1350 Table 2. Payload Size and Rate 1352 To support circuit emulation, the entire SPE of a SONET STS or SDH 1353 VC level is encapsulated into packets, using the encapsulation 1354 defined in section 5, for carriage across packet-switched networks. 1356 Full Copyright Statement 1358 Copyright (C) The Internet Society (2001). All Rights Reserved. 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