Which mechanism is commonly used to protect BGP session integrity against tampering in transit?

• A. TLS client certificates
• B. IPsec tunneling
• C. Message authentication codes such as MD5 or TCP-AO
• D. No protection is needed

Answer: (C)

Protecting BGP session integrity relies on authenticating the data that travels over the TCP connection between peers. BGP itself runs over TCP, which provides reliability and order but not authentication of the message contents. To prevent tampering or impersonation while in transit, operators use a shared secret to generate a message authentication code for each TCP segment or BGP message. This MAC, provided by algorithms like MD5 (the older TCP MD5 Signature option) or the newer TCP-AO, is checked by the receiving peer; if the data or the MAC doesn’t match, the segment is discarded. This ensures that only sessions protected with the correct secret are accepted, thwarting tampering attempts.

TLS client certificates would require wrapping BGP in TLS, which is not the standard, widely deployed method for BGP session protection. IPsec tunneling could protect the traffic but is less common for BGP specifically and introduces different deployment complexities. The idea that no protection is needed is incorrect because BGP sessions can be hijacked or tampered with if not authenticated in transit.