Cisco Cisco IOS Software Release 12.2(14)S
MPLS Label Distribution Protocol (LDP)
Supported Platforms
3
Cisco IOS Release 12.2(14)S
forwards the packet to the next hop. With MPLS forwarding, when a packet arrives at a router the router
looks at the incoming label, looks up the label in a table, and then forwards the packet to the next hop.
MPLS LDP is useful for applications that require hop-by-hop forwarding, such as MPLS VPNs.
looks at the incoming label, looks up the label in a table, and then forwards the packet to the next hop.
MPLS LDP is useful for applications that require hop-by-hop forwarding, such as MPLS VPNs.
From an historical and functional standpoint, LDP is a superset of the Cisco prestandard Tag Distribution
Protocol (TDP), which also supports MPLS forwarding along normally routed paths. For those features
that LDP and TDP share in common, the pattern of protocol exchanges between network routing
platforms is identical. The differences between LDP and TDP for those features supported by both
protocols are largely embedded in their respective implementation details, such as the encoding of
protocol messages.
Protocol (TDP), which also supports MPLS forwarding along normally routed paths. For those features
that LDP and TDP share in common, the pattern of protocol exchanges between network routing
platforms is identical. The differences between LDP and TDP for those features supported by both
protocols are largely embedded in their respective implementation details, such as the encoding of
protocol messages.
This release of LDP, which supports both the LDP and TDP protocols, provides the means for
transitioning an existing network from a TDP environment to an LDP environment. Thus, you can run
LDP and TDP simultaneously on any router platform. The routing protocol that you select can be
configured on a per-interface basis for directly connected neighbors and on a per-session basis for
nondirectly connected (targeted) neighbors. In addition, an LSP across an MPLS network can be
supported by LDP on some hops and by TDP on other hops.
transitioning an existing network from a TDP environment to an LDP environment. Thus, you can run
LDP and TDP simultaneously on any router platform. The routing protocol that you select can be
configured on a per-interface basis for directly connected neighbors and on a per-session basis for
nondirectly connected (targeted) neighbors. In addition, an LSP across an MPLS network can be
supported by LDP on some hops and by TDP on other hops.
Benefits
LDP is an IETF standards tracking protocol. The primary benefit of LDP over the prestandard TDP
protocol is that the former increases the number of platforms on which MPLS interoperability can be
achieved.
protocol is that the former increases the number of platforms on which MPLS interoperability can be
achieved.
Related Features and Technologies
The MPLS Label Distribution Protocol is used in conjunction with the following:
•
Multiprotocol Label Switching (MPLS)
•
Cisco Express Forwarding (CEF)
•
MPLS Traffic Engineering
•
MPLS VPNs
Related Documents
For additional information about MPLS functionality running on routers or switches in a network,
consult the following documentation:
consult the following documentation:
•
Multiprotocol Label Switching on Cisco Routers
•
MPLS Class of Service (CoS)
•
MPLS Traffic Engineering and Enhancements
•
MPLS Virtual Private Networks (VPNs)
Supported Platforms
LDP is supported on the following platforms:
•
Cisco 7200 series routers