RFC 3255
Extending Point-to-Point Protocol (PPP) over Synchronous Optical NETwork/Synchronous Digital Hierarchy (SONET/SDH) with virtual concatenation, high order and low order payloads
Pages: 8
Proposed Standard
Proposed Standard
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....................................81. 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.
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:
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.
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].
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.
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" 19967. 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.
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
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.