Which technology provides a secure channel for all Layer 2 traffic on a link?

MACsec (Media Access Control Security) operates at Layer 2 (the Data Link Layer) and provides hop-by-hop encryption and authentication for all traffic traversing a link. This makes it ideal for securing Ethernet links between network devices. SSL (Secure Sockets Layer) and its successor TLS operate at the Transport Layer (Layer 4) and are primarily used for securing application-level communication, not raw Layer 2 traffic. IPsec (Internet Protocol Security) operates at Layer 3 (the Network Layer) and secures IP packets, but not the underlying Layer 2 frames. Cisco TrustSec is a broader security framework that uses various technologies, including MACsec, but MACsec itself is the specific technology for Layer 2 link encryption.