Network Working Group Dave Carr Internet Draft Gandalf expires in six months October 1993 PPP Gandalf FZA Compression Protocol draft-ietf-pppext-gandalf-00.txt Status of this Memo 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 ietf-ppp@ucdavis.edu mailing list. Distribution of this memo is unlimited. This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a ``working draft'' or ``work in progress.'' Please check the 1id-abstracts.txt listing contained in the internet-drafts Shadow Directories on nic.ddn.mil, nnsc.nsf.net, nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au to learn the current status of any Internet Draft. Abstract The Point-to-Point Protocol (PPP) [1] provides a standard method for transporting multi-protocol datagrams over point-to-point links. The PPP Compression Control Protocol [2] provides a method to negotiate and utilize compression protocols over PPP encapsulated links. This document describes the use of the Gandalf FZA data compression algorithm for compressing PPP encapsulated packets. Carr expires in six months [Page i] DRAFT Gandalf FZA October 1993 1. Introduction FZA is a high performance LZA derivative which maximizes compression at the expense of memory and CPU. Compression performance can be adjusted based on CPU and memory available. Multiple PPP packets can be combined in a single compressed frame, or a single PPP packet can be spread across multiple frames. 1.1. Licensing Source and object licenses are available on a non-discriminatory basis for either a royalty or fixed price arrangement. Patent indemnity is included with the license. Carr expires in six months [Page 1] DRAFT Gandalf FZA October 1993 2. FZA Packets Before any FZA packets may be communicated, PPP must reach the Network-Layer Protocol phase, and the CCP Control Protocol must reach the Opened state. Exactly one FZA datagram is encapsulated in the PPP Information field, where the PPP Protocol field indicates type hex 00FD (compressed datagram). The maximum length of the FZA datagram transmitted over a PPP link is the same as the maximum length of the Information field of a PPP encapsulated packet. Prior to compression, the uncompressed data begins with the PPP Protocol number. This value MAY be compressed when Protocol-Field- Compression is negotiated. PPP Link Control Protocol packets MUST NOT be sent within compressed data. Padding The FZA packets require the negotiation of the Self-Describing- Padding Configuration Option [3] at LCP Link Establishment. Reliability and Sequencing The FZA algorithm expects a reliable link, as described in "PPP Reliable Transmission" [4]. Gandalf FZA expects the packets to be delivered in sequence. Data Expansion The maximum expansion of Gandalf FZA is 2:1. However, typical expansion on pre-compressed data is 1.01:1. Expanded data is sent to maintain the integrity of the compression history. When the expansion exceeds the size of the peer's Maximum Receive Unit for the link, the expanded packet is sent in multiple PPP frames. The compressed data contains an indication of the end of the original packet. Carr expires in six months [Page 2] DRAFT Gandalf FZA October 1993 2.1. Packet Format A summary of the Gandalf FZA packet format is shown below. The fields are transmitted from left to right. 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PPP Protocol | Compressed Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ PPP Protocol The PPP Protocol field is described in the Point-to-Point Protocol Encapsulation [1]. When the Gandalf FZA compression protocol is successfully negotiated by the PPP Compression Control Protocol [2], the value is 00FD hex. This value MAY be compressed when Protocol-Field- Compression is negotiated. Compressed Data The compressed PPP encapsulated packet. Carr expires in six months [Page 3] DRAFT Gandalf FZA October 1993 3. Configuration Option Format Description The CCP Gandalf-FZA Configuration Option negotiates the use of Gandalf FZA on the link. By default or ultimate disagreement, no compression is used. A summary of the Gandalf-FZA Configuration Option format is shown below. The fields are transmitted from left to right. 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | History | Data ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 6 Length >= 3 History The History field specifies the maximum size of the compression history in powers of 2. Valid values range from 12 to 15. Data Zero or more octets of additional configuration information. Any implementation which does not implement this information MUST send a Configure-Nak without this field. Carr expires in six months [Page 4] DRAFT Gandalf FZA October 1993 Security Considerations Security issues are not discussed in this memo. References [1] Simpson, W.A., "The Point-to-Point Protocol (PPP)", work in progress. [2] Rand, D., "The PPP Compression Control Protocol (CCP)", work in progress. [3] Simpson, W.A., "PPP LCP Extensions", work in progress. [4] Rand, D., "PPP Reliable Transmission", work in progress. Acknowledgments Editting and formatting by Bill Simpson. Carr expires in six months [Page 5] DRAFT Gandalf FZA October 1993 Chair's Address The working group can be contacted via the current chair: Fred Baker Advanced Computer Communications 315 Bollay Drive Santa Barbara, California 93117 EMail: fbaker@acc.com Author's Address Questions about this memo can also be directed to: Dave Carr Gandalf Data Limited 130 Colonnade Road South Napean, Ontario, Canada K2E 7M4 (613) 723-6500 (613) 226-1717 Fax Email: dcarr@gandalf.ca Carr expires in six months [Page 6] DRAFT Gandalf FZA October 1993 Table of Contents 1. Introduction .......................................... 1 1.1 Licensing ....................................... 1 2. FZA Packets ........................................... 2 2.1 Packet Format ................................... 3 3. Configuration Option Format ........................... 4 SECURITY CONSIDERATIONS ...................................... 5 REFERENCES ................................................... 5 ACKNOWLEDGEMENTS ............................................. 5 CHAIR'S ADDRESS .............................................. 6 AUTHOR'S ADDRESS ............................................. 6 Bill.Simpson@um.cc.umich.edu