INTERNET DRAFT PPP SDL on Packet - over - Lightwave

The Point-to-Point Protocol (PPP) in RFC-1661 [1] provides a standard method for transporting multi-protocol datagrams over point-to-point links, and RFCs 1662 [2] and 1619 [3] provide a means to carry PPP over Synchronous Optical Network (SONET) [5] and Synchronous Digital Hierarchy (SDH) [6] circuits. PPP over Simple Data Link (SDL) using SONET/SDH with ATM-like framing (PPPEXT WG work in Progress) extended these standards to include a new encapsulation for PPP called Simple Data Link (SDL) [8]. This document extends the use of SDL over raw lightwave channels without an intervening SONET/SDH layer, which are also referred to as "dark fiber" or Packet-over-Lightwave" (POL) links, This document is the product of the Point-to-Point Protocol Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the [email protected] mailing list. Applicability This specification is intended for those implementations which desire to use PPP encapsulation over high speed point-to-point circuits with the so-called "dark fiber" or raw lightwave channels. This enhanced framing mechanisms for PPP encapsulation method has very low overhead, good hardware scaling properties and is resilient to payload expansion. It is anticipated that significantly higher throughput can be attained with SDL when compared to other transport and encapsulation mechanisms for high-speed packet data over lightwave channels, and at a significantly lower cost for line termination equipment. SDL is defined over other media types and for other data link protocols, but this specification covers only the use of PPP over SDL raw lightwave channels. Systems requiring typical public network functions such as transmission quality assessment, protection switching/restoration, and OAM&P at the transmission level will may require either an additional transmission layer (e.g., SONET/SDH or OTN [7]) with or equivalent OAM&P functionality not defined in this document. 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 readily have this information (that is, for nonSDL 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 Carlson, et al. expires December 1999 [Page 2] INTERNET DRAFT PPP SDL on Packet-over-Lightwave June 1999 due to the general requirement of length information in other parts of the system, notably in queueing and congestion control strategies such as Weighted Fair Queuing [12] and Random Early Detection [13]. Carlson, et al. expires December 1999 [Page 3] INTERNET DRAFT PPP SDL on Packet-over-Lightwave June 1999 Table of