
Configuring BGP Services
5-9
BGP Messages
BGP uses four different message types: Open, Keepalive, Update, and
Notification.
All of the messages share a common BGP message header made up of the
following three fields:
• Marker
This field is used for authentication. Currently, this field can only be set to all
1s, specifying the null authentication scheme, the only authentication scheme
yet defined.
• Length
This field indicates the total length of the message in octets. The value of this
field must be between 19 octets (header-only message) and 4096 octets.
• Type
This field indicates the type of message:
1 — Open message
2 — Update message
3 — Notification message
4 — Keepalive message
Open Message
The Open message is used to establish a BGP connection between two BGP
speakers. In addition to the message header, the Open message includes the
following fields:
• The BGP Version. Bay Networks currently supports BGP Version 3 and
Version 4.
• The AS Number, which provides the autonomous system number of the
transmitting BGP speaker.
• The Holdtime, which indicates the maximum number of seconds that can
elapse between the receipt of Keepalive and/or Notification and/or Update
messages. If this timer expires, the receiver assumes the connection is down.
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