Message Header Format

Message Header Format
BGP will process a message only when the entire message has been received. BGP requires that
a message be a minimum of 19 octets to a maximum of 4,096 octets. The basic message header
format is broken down into these fields:

16-byte Marker field

2-byte Length field

1-byte Type field
Figure 8.2 gives the layout for the BGP message header.
Marker
The Marker field is 16 bytes long. The Marker field is used to detect a loss of synchronization
between a set of BGP peers and also to authenticate incoming BGP messages. The
value of the Marker field depends on the type of message. If an OPEN message does not contain
authentication information, the Marker must be set to all 1s.
Length
The Length field is 2 bytes long and indicates the length of the entire message including
the Marker field. The value for the Length field must be at least 19 and no more than 4,096.