Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual

Page 321

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide

297

53-1003031-02

LDP overview

NOTE

MPLS cannot be configured on the system globally when a NI-MLX-10Gx8-D card is installed.

The system supports Label Distribution Protocol (LDP) for the configuration of
non-traffic-engineered tunnel LSPs in an MPLS network. LDP is described in RFC 3036.

When used to create tunnel LSPs, LDP allows a set of destination IP prefixes (known as a
Forwarding Equivalence Class or FEC) to be associated with an LSP. Each LSR establishes a peer
relationship with its neighboring LDP-enabled routers and exchanges label mapping information.
This label mapping information is stored in an LDP database on each LSR. When an LSR
determines that one of its peers is the next hop for a FEC, it uses the label mapping information
from the peer to set up an LSP that is associated with the FEC. It then sends label mapping
information to its upstream peers, allowing the LSP to extend across the MPLS network.

The devices advertise their loopback addresses to their LDP peers as a 32-bit prefix-type FEC.
When an LSR installs a label for a FEC, it also creates an MPLS tunnel route, which is then made
available to routing applications. This allows each router to potentially be an ingress LER for an LSP
whose destination is the device's loopback address.

The result of an LDP configuration is a full mesh of LSPs in an MPLS network, with each
LDP-enabled router a potential ingress, transit, or egress LSR, depending on the destination.

The implementation supports the following aspects of LDP:

Liberal label retention – Each LSR sends its peers Label Mapping messages, which map a label to
a FEC. Peer LSR receiving these messages retain all of the mappings, even though they may not
actually be used for data forwarding.

Unsolicited label advertisement – The LSR sends Label Mapping messages to its LDP peers even
though they did not explicitly request them.

Ordered label distribution – The LSR sends a Label Mapping message to its peers only when it
knows the next hop for a FEC, or is itself an egress LER for the FEC. When an LSR does not know
the next hop for a FEC, and is not an egress LER for the FEC, it waits until a downstream LSR sends
it a Label Mapping message for the FEC. At this point, the LSR can send Label Mapping messages
for the FEC to its peers. This allows label mappings to be distributed, in an orderly fashion, starting
from the egress LER and progressing upstream.

Displaying LDP
Neighbor
Connection
Information

Yes

Displaying the
LDP Packet
Statistics

Yes

TABLE 40

Supported Brocade Label Distribution Protocol (LDP) features (Continued)

Features
supported

Brocade
NetIron XMR
Series

Brocade
MLX Series

Brocade
NetIron CES
2000 Series
BASE
package

Brocade
NetIron CES
2000 Series
ME_PREM
package

Brocade
NetIron CES
2000 Series
L3_PREM
package

Brocade
NetIron CER
2000 Series
Base
package

Brocade
NetIron CER
2000 Series
Advanced
Services
package