Port 711
Cisco Tag Distribution
Cisco Tag Distribution Protocol (TDP) was an early Cisco-proprietary protocol used primarily for exchanging MPLS label bindings between routers in a network. Though it provided foundational MPLS label distribution capabilities, it has largely been superseded by the standardized Label Distribution Protocol (LDP), which offers enhanced compatibility and interoperability across diverse vendor environments..
Technical Details
Cisco Tag Distribution Protocol (TDP) is a Cisco-developed protocol that facilitates the binding and propagation of MPLS labels between adjacent routers. It establishes sessions over TCP, ensuring reliable delivery of label mapping information necessary for efficient label switched path (LSP) setup within an MPLS-enabled infrastructure.
TDP operates by exchanging labels associated with IP prefixes so that routers can quickly switch packets based on short labels instead of long network addresses. This mechanism streamlines packet forwarding, reduces processing overhead, and supports advanced MPLS features such as traffic engineering and VPN services. Despite its proprietary nature, it played a crucial role in early MPLS implementations, especially within Cisco-heavy deployments.
Over time, TDP has been phased out in favor of the Internet Engineering Task Force's Label Distribution Protocol (LDP). LDP is an open standard, enabling broader multi-vendor interoperability and support. Modern Cisco devices default to LDP, encouraging migrations from legacy TDP deployments for more standardized operations.