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rfc:rfc3255

Network Working Group N. Jones Request for Comments: 3255 Agere Systems Category: Standards Track C. Murton

                                                       Nortel Networks
                                                            April 2002
  Extending Point-to-Point Protocol (PPP) over Synchronous Optical
   NETwork/Synchronous Digital Hierarchy (SONET/SDH) with virtual
          concatenation, high order and low order payloads

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 This document describes an extension to the mapping of Point-to-Point
 Protocol (PPP) into Synchronous Optical NETwork/Synchronous Digital
 Hierarchy (SONET/SDH) to include the use of SONET/SDH SPE/VC virtual
 concatenation and the use of both high order and low order payloads.

Table of Contents

 1.  Introduction................................................1
 2.  Rate Comparisons............................................2
 3.  Physical Layer Requirements.................................4
 4.  Standards Status............................................5
 5.  Security Considerations.....................................5
 6.  References..................................................6
 7.  Acknowledgements............................................6
 8.  Authors' Addresses..........................................7
 9.  Full Copyright Statement....................................8

1. Introduction

 Current implementations of PPP over SONET/SDH are required to select
 transport structures from the relatively limited number of
 contiguously concatenated signals that are available.

Jones & Murton Standards Track [Page 1] RFC 3255 Extending PPP over SONET/SDH April 2002

 The only currently supported SONET/SDH SPE/VCs in RFC 2615 [3] are
 the following:
        SONET                   SDH
    ----------------------------------------
    STS-3c-SPE                  VC-4
    STS-12c-SPE                 VC-4-4c
    STS-48c-SPE                 VC-4-16c
    STS-192c-SPE                VC-4-64c
 Note that VC-4-4c and above are not widely supported in SDH networks
 at present.
 The use of virtual concatenation means that the right size SONET/SDH
 bandwidth can be selected for PPP links.
 For the convenience of the reader, the equivalent terms are listed
 below:
        SONET                   SDH
    ---------------------------------------------
    SPE                         VC
    VT (1.5/2/6)                Low order VC (VC-11/12/2)
    STS SPE                     Higher Order VC (VC-3/4/4-Nc)
    STS-1 frame                 STM-0 frame (rarely used)
    STS-1 SPE                   VC-3
    STS-1-nv                    VC-3-nv (virtual concatenation)
    STS-1 payload               C-3
    STS-3c frame                STM-1 frame, AU-4
    STS-3c SPE                  VC-4
    STS-3c-nv                   VC-4-nv (virtual concatenation)
    STS-3c payload              C-4
    STS-12c/48c/192c frame      STM-4/16/64 frame, AU-4-4c/16c/64c
    STS-12c/48c/192c-SPE        VC-4-4c/16c/64c
    STS-12c/48c/192c payload    C-4-4c/16c/64c
 This table is an extended version of the equivalent table in RFC 2615
 [3].  Additional information on the above terms can be found in
 Bellcore GR-253-CORE [4], ANSI T1.105 [5], ANSI T1.105.02 [6] and
 ITU-T G.707 [7].

2. Rate Comparisons

 Currently supported WAN bandwidth links for PPP over SONET/SDH:

Jones & Murton Standards Track [Page 2] RFC 3255 Extending PPP over SONET/SDH April 2002

       ANSI                   ETSI
    -----------------------------------------------------
      STS-3c (150Mbit/s)     STM-1 (150Mbit/s)
      STS-12c (620Mbit/s)    STM-4 AU-4-4c (620Mbit/s)
      STS-48c (2.4Gbit/s)    STM-16 AU-4-16c (2.4Gbit/s)
      STS-192c (9.6Gbit/s)   STM-64 AU-4-64c (9.6Gbit/s)
 Note that AU-4-4c and AU-4-16c are not generally available in SDH
 networks at present.
 With virtual concatenation the following additional WAN bandwidth
 links would be available for PPP over SONET/SDH:
      SONET
    VT-1.5-nv (n=1-64)       1.6Mbit/s-102Mbit/s
    STS-1-nv  (n=1-64)       49Mbit/s-3.1Gbit/s
    STS-3c-nv (n=1-64)       150Mbit/s-10Gbit/s
      SDH
    VC-12-nv (n=1-64)        2.2Mbit/s-139Mbit/s
    VC-3-nv  (n=1-64)        49Mbit/s-3.1Gbit/s
    VC-4-nv  (n=1-64)        150Mbit/s-10Gbit/s
 Higher levels of virtual concatenation are possible, but not
 necessarily useful.  Lower levels of virtual concatenation are
 defined in the telecommunications standards for use if needed.
 Table 1 and Table 2, respectively depict the SONET/SDH transport
 structures that are currently available to carry various popular bit
 rates.  Each table contains three columns.  The first column shows
 the bit rates of the service to be transported.
 The next column contains two values:
 a) the logical signals that are currently available to provide such
 transport and, b) in parenthesis, the percent efficiency of the given
 transport signal without the use of virtual concatenation.
 Likewise, the final column also contains two values:
 a) the logical signals that are currently available to provide such
 transport and, b) in parenthesis, the percent efficiency of the given
 transport signal with the use of virtual concatenation.

Jones & Murton Standards Track [Page 3] RFC 3255 Extending PPP over SONET/SDH April 2002

 Note, that Table 1, contains SONET transport signals with the
 following effective payload capacity: VT-1.5 SPE = 1.600 Mbit/s,
 STS-1 SPE = 49.536 Mbit/s, STS-3c SPE = 149.760 Mbit/s, STS-12c SPE =
 599.040 Mbit/s, STS-48c SPE = 2,396.160 Mbit/s, and STS-192c SPE =
 9,584.640 Mbit/s.
       Table 1. SONET Virtual Concatenation
     Bit rate     Without            With
    --------------------------------------------
     10Mbit/s    STS-1 (20%)   VT-1.5-7v (89%)
     100Mbit/s   STS-3c (67%)  STS-1-2v (100%)
     200Mbit/s   STS-12c(33%)  STS-1-4v (100%)
     1Gbit/s     STS-48c(42%)  STS-3c-7v (95%)
 Similarly, Table 2, contains SDH transport signals with the following
 effective payload capacity: VC-12 = 2.176 Mbit/s, VC-3 = 48.960
 Mbit/s, VC-4 = 149.760 Mbit/s, VC-4-4c = 599.040 Mbit/s, VC-4-16c =
 2,396.160 Mbit/s, and VC-4-64c = 9,584.640 Mbit/s.
       Table 2. SDH Virtual Concatenation
     Bit rate     Without            With
    -------------------------------------------
     10Mbit/s    VC-3 (20%)    VC-12-5v (92%)
     100Mbit/s   VC-4 (67%)    VC-3-2v (100%)
     200Mbit/s   VC-4-4c(33%)  VC-3-4v (100%)
     1Gbit/s     VC-4-16c(42%) VC-4-7v (95%)

3. Physical Layer Requirements

 There are two minor modifications to the physical layer requirements
 as defined in RFC 2615 when virtually concatenated SPEs/VCs are used
 to provide transport for PPP over SONET/SDH.
 First, the path signal label (C2 byte) value for SONET/SDH STS-1/VC-3
 and above SPE/VCs is required to be the same for all constituent
 channels.  This is in contrast to the use of a single C2 byte for PPP
 transport over contiguously concatenated SONET/SDH SPE/VCs.  The
 values used for the C2 bytes should be in accordance with RFC 2615.
 For SONET VT-1.5/2/6 and SDH VC-11/12/2 the path signal label (V5
 byte bits 5-7) is required to be the same for all constituent
 channels per ITU-T G.707 [7] and ANSI T1.105.02 [6].

Jones & Murton Standards Track [Page 4] RFC 3255 Extending PPP over SONET/SDH April 2002

 Second, for SONET/SDH STS-1/VC-3 and above SPE/VCs the multi-frame
 indicator (H4) byte will be unused for transport links utilizing
 contiguously concatenated SONET/SDH SPE/VCs.  When the concatenation
 scheme is virtual as opposed to contiguous, the H4 byte must be
 populated as per ITU-T G.707 or T1.105.02.  Similarly, for virtual
 concatenation based on SONET VT-1.5/2/6 and SDH VC-11/12/2 channels
 bit 2 of the path overhead K4 byte will be set to the value indicated
 per ITU-T G.707 [7] and ANSI T1.105.02 [6].

4. Standards Status

 ITU-T (SG13/SG15), ANSI T1X1 and ETSI TM1/WP3 have developed a global
 standard for SONET/SDH High Order and Low Order payload Virtual
 Concatenation.  This standard is defined in the following documents:
    ITU-T G.803 Architecture of transport networks based on the
    synchronous digital hierarchy (SDH)
    ITU-T G.707 Network Node Interface for the Synchronous Digital
    Hierarchy (SDH)
    ITU-T G.783 Characteristics of Synchronous Digital Hierarchy (SDH)
    Equipment Functional Blocks
    ANSI T1.105 Synchronous Optical Network (SONET) - Basic
    Description including Multiplex Structure, Rates and Formats
    ANSI T1.105.02 Synchronous Optical Network (SONET) - Payload
    Mappings
    ETSI EN 300 417-9-1 Transmission and Multiplexing (TM) Generic
    requirements of transport functionality of equipment Part 9:
    Synchronous Digital Hierarchy (SDH) concatenated path layer
    functions.  Subpart 1: Requirements
 Work in ITU-T, ANSI T1X1 and ETSI TM1/WP3 has ensured global
 standards alignment.
 With the completion of a standard for SONET/SDH SPE/VC virtual
 concatenation it is appropriate to document the use of this standard
 for PPP transport over SONET/SDH, which is the intent of this
 document.

5. Security Considerations

 The security discussion in RFC 2615 also applies to this document.
 No new security features have been explicitly introduced or removed
 compared to RFC 2615.

Jones & Murton Standards Track [Page 5] RFC 3255 Extending PPP over SONET/SDH April 2002

6. References

 [1]   Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC
       1661, July 1994.
 [2]   Simpson, W., "PPP in HDLC-like Framing", STD 51, RFC 1662, July
       1994.
 [3]   Malis, A. and W. Simpson, "PPP over SONET/SDH RFC 2615, June
       1999.
 [4]   Bellcore Publication GR-253-Core "Synchronous Optical Network
       (SONET) Transport Systems: Common Generic Criteria" January
       1999
 [5]   American National Standards Institute, "Synchronous Optical
       Network (SONET) - Basic Description including Multiplex
       Structure, Rates and Formats" ANSI T1.105-1995
 [6]   American National Standards Institute, "Synchronous Optical
       Network (SONET) - Payload Mappings" ANSI T1.105.02-1998
 [7]   ITU-T Recommendation G.707 "Network Node Interface for the
       Synchronous Digital Hierarchy" 1996

7. Acknowledgements

 We would like to acknowledge Huub van Helvoort, Maarten Vissers
 (Lucent Technologies), Paul Langner (Lucent Microelectronics), Trevor
 Wilson (Nortel Networks), Mark Carson (Nortel Networks) and James
 McKee (Nortel Networks) for their contribution to the development of
 virtual concatenation of SONET/SDH payloads.

Jones & Murton Standards Track [Page 6] RFC 3255 Extending PPP over SONET/SDH April 2002

8. Authors' Addresses

 Nevin Jones
 Agere Systems
 Broadband IC Systems Architecture
 Rm. 7E-321
 600 Mountain Avenue
 Murray Hill, NJ 07974
 EMail: nrjones@agere.com
 Chris Murton
 Nortel Networks Harlow Laboratories
 London Road, Harlow,
 Essex, CM17 9NA UK
 EMail: murton@nortelnetworks.com

Jones & Murton Standards Track [Page 7] RFC 3255 Extending PPP over SONET/SDH April 2002

9. Full Copyright Statement

 Copyright (C) The Internet Society (2002).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Jones & Murton Standards Track [Page 8]

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