Appendix D. Comparison with RFC 1105

All of the changes listed in Appendices A, B, and C, plus the following.

Minor changes to the [RFC1105] Finite State Machine were necessary to accommodate the TCP user interface provided by BSD version 4.3.

The notion of Up/Down/Horizontal relations presented in RFC 1105 has been removed from the protocol.

The changes in the message format from RFC 1105 are as follows:

The Hold Time field has been removed from the BGP header and added to the OPEN message.
The version field has been removed from the BGP header and added to the OPEN message.
The Link Type field has been removed from the OPEN message.
The OPEN CONFIRM message has been eliminated and replaced with implicit confirmation, provided by the KEEPALIVE message.
The format of the UPDATE message has been changed significantly. New fields were added to the UPDATE message to support multiple path attributes.
The Marker field has been expanded and its role broadened to support authentication.

Note that quite often BGP, as specified in RFC 1105, is referred to as BGP-1; BGP, as specified in [RFC1163], is referred to as BGP-2; BGP, as specified in RFC 1267 is referred to as BGP-3; and BGP, as specified in this document is referred to as BGP-4.