PPP over Simple Data Link (SDL) using SONET/SDH with ATM-like framing
RFC 2823

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Network Working Group                                         J. Carlson
Request for Comments: 2823                        Sun Microsystems, Inc.
Category: Experimental                                        P. Langner
                              Lucent Technologies Microelectronics Group
                                                   E. Hernandez-Valencia
                                                           J. Manchester
                                                     Lucent Technologies
                                                                May 2000

                    PPP over Simple Data Link (SDL)
                 using SONET/SDH with ATM-like framing

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   The Point-to-Point Protocol (PPP) [1] provides a standard method for
   transporting multi-protocol datagrams over point-to-point links, and
   RFCs 1662 [2] and 2615 [3] provide a means to carry PPP over
   Synchronous Optical Network (SONET) [4] and Synchronous Digital
   Hierarchy (SDH) [5] circuits.  This document extends these standards
   to include a new encapsulation for PPP called Simple Data Link (SDL)
   [6].  SDL provides a very low overhead alternative to HDLC-like
   encapsulation, and can also be used on SONET/SDH links.

Applicability

   This specification is intended for those implementations that use PPP
   over high speed point-to-point circuits, both with so-called "dark
   fiber" and over public telecommunications networks.  Because this
   enhanced PPP encapsulation has very low overhead and good hardware
   scaling characteristics, it is anticipated that significantly higher
   throughput can be attained when compared to other possible SONET/SDH
   payload mappings, and at a significantly lower cost for line
   termination equipment.

Carlson, et al.               Experimental                      [Page 1]
RFC 2823                  PPP SDL on SONET/SDH                  May 2000

   SDL is defined over other media types and for other data link
   protocols, but this specification covers only the use of PPP over SDL
   on SONET/SDH.

   The use of SDL requires the presentation of packet length information
   in the SDL header.  Thus, hardware implementing SDL must have access
   to the packet length when generating the header, and where a router's
   input link does not have this information (that is, for non-SDL input
   links), the router may be required to buffer the entire packet before
   transmission.  "Worm-hole" routing is thus at least problematic with
   SDL, unless the input links are also SDL.  This, however, does not
   appear to be a great disadvantage on modern routers due to the
   general requirement of length information in other parts of the
   system, notably in queuing and congestion control strategies such as
   Weighted Fair Queuing [7] and Random Early Detect [8].

   This document is not a replacement for the existing HDLC-like framing
   mandated by RFC 2615 [3].  Instead, the authors intend to gain
   implementation experience with this technique for operational and
   performance evaluation purposes, and would like to hear from others
   either considering or using the protocol as described in this
   document.  Please see Section 14 of this document for contact
   information.

Carlson, et al.               Experimental                      [Page 2]
RFC 2823                  PPP SDL on SONET/SDH                  May 2000

Table of Contents

   1.  Introduction ...............................................    4
   2.  Compliance .................................................    4
   3.  Physical Layer Requirements ................................    5
   3.1.  Payload Types ............................................    5
   3.2.  Control Signals ..........................................    6
   3.3.  Synchronization Modes ....................................    7
   3.4.  Simple-Data-Link LCP Option ..............................    7
   3.5.  Framing ..................................................    8
   3.6.  Framing Example ..........................................   11
   3.7.  Synchronization Procedure ................................   11
   3.8.  Scrambler Operation ......................................   12
   3.9.  CRC Generation ...........................................   12
   3.10.  Error Correction ........................................   13
   4.  Performance Analysis .......................................   14
   4.1.  Mean Time To Frame (MTTF) ................................   14
   4.2.  Mean Time To Synchronization (MTTS) ......................   15