BGP uses authentication and Generalized TTL Security Mechanism (GTSM) to ensure exchange security between BGP peers.
BGP authentication includes Message Digest 5 (MD5) authentication and keychain authentication, which improves communication security between BGP peers. In MD5 authentication, you can only set the authentication password for a TCP connection. In keychain authentication, you can set the authentication password for a TCP connection and authenticate BGP messages.
BGP GTSM checks whether the time to live (TTL) value in the IP packet header is within a predefined range. It permits or discards the packets with TTL values outside of the predefined range to protect services above the IP layer. BGP GTSM enhances system security.
Assume that the TTL value range of packets from BGP peers is set to 254-255. When an attacker forges valid BGP packets and keeps sending these packets to attack a device, the TTL values of these packets are smaller than 254. If BGP GTSM is not enabled on the device, the device finds that these packets are destined for itself and sends the packets to the control plane for processing. Then the control layer needs to process a large number of such attack packets, causing high CPU usage. If BGP GTSM is enabled on the device, the system checks the TTL values in all BGP packets and discards the attack packets with TTL values smaller than 254. This prevents network attack packets from consuming CPU resources.