Port 646
Label Distribution Protocol
Label Distribution Protocol (LDP) is a key control protocol used within MPLS (Multiprotocol Label Switching) networks, enabling efficient and scalable routing by assigning labels to data packets. It facilitates the dynamic distribution and management of labels between routers, simplifying packet forwarding decisions and improving overall network performance in large-scale, multi-service network infrastructures..
Technical Details
Overview:
Label Distribution Protocol (LDP) operates as a signaling mechanism within MPLS architectures, facilitating the mapping of packet routes by distributing label bindings among adjacent routers. This allows MPLS routers to set up Label-Switched Paths (LSPs) dynamically without manual intervention.
How It Works:
LDP establishes control sessions over TCP (by default on port 646) between Label Switching Routers (LSRs). These routers exchange label mapping information, enabling each device to associate a network prefix with a locally assigned label. The label bindings disseminated via LDP help build a consistent forwarding table across the MPLS domain, ensuring that packets follow predetermined paths based on labels rather than IP lookups.
Protocol Features:
- Supports both IPv4 and IPv6 label bindings
- Operates in both downstream unsolicited and downstream on demand modes
- Utilizes TCP for reliable transmission of control messages
- Can operate over UDP for discovery of LDP peers
- Integrates with existing routing protocols (e.g., OSPF, IS-IS) for scalable deployment
LDP simplifies the management of MPLS networks by automating label distribution and path setup, which is crucial for efficient traffic engineering and service differentiation.