BGP Update Total Path Attribute Length field

The Total Path Attribute Length is a field found within the BGP Update message. According to the RFC, it is a 2-byte integer that indicates the total length of the Path Attributes field in octets. Its value allows the length of the Network Layer Reachability field to be determined.

A value of 0 indicates that no Path Attributes are present in this UPDATE message.

There can be multiple prefixes in one BGP update, but there is a limit to the total BGP message size. For more information about that, take a look at BGP Maximum message size.

https://datatracker.ietf.org/doc/html/rfc4271#page-16 https://networklessons.com/bgp/bgp-messages