BGP - End-of-RIB marker
An End-of-RIB marker is a BGP UPDATE message with no reachable Network Layer Reachability Information (NLRI) and an empty withdrawn NLRI field as well. The following Wireshark capture displays such an UPDATE:
Notice that the withdrawn routes is zero, and that there are no NRLI indicators at the end of that particular UPDATE message. Thus, this update message is an End-of-RIB marker.
Note that multiple BGP messages can be grouped together within a single TCP segment rather than being sent separately. In the Wireshark output above, we see that the End-of-RIB marker is actually sent as a separate Update message within the same TCP segment. Whereas the first update message has a non-zero value for the path attribute length, the final UPDATE message is indeed an End-of-RIB marker since both values are set to 0.