RFC 1993 (rfc1993) - Page 2 of 6
PPP Gandalf FZA Compression Protocol
Alternative Format: Original Text Document
RFC 1993 Gandalf FZA August 1996
2. FZA Packets
Before any FZA packets may be communicated, PPP must reach the
Network-Layer Protocol phase.
When the Compression Control Protocol (CCP) has reached the Opened
state, and FZA is negotiated as the primary compression algorithm,
the PPP Protocol field indicates type hex 00FB (link compressed
datagram), or 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.
Padding
The FZA packets require the negotiation of the Self-Describing-
Padding Configuration Option [5] at LCP Link Establishment.
Reliability and Sequencing
The FZA algorithm expects a reliable link, as described in "PPP
Reliable Transmission" [6].
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.
Barbir, Carr & Simpson