Alcatel-Lucent 7210 SAS M - Link LDP; Targeted LDP

Label Distribution Protocol
Page 228 7210 SAS M, T, X, R6, Mxp MPLS Configu-
ration Guide
When unlabeled packets arrive at the ingress LER, the forwarding plane will consult the LTN
entry and will use a hashing algorithm to map the packet to one of the NHLFEs (push label) and
forward the packet to the corresponding next-hop peer. For labeled packets arriving at a transit or
egress LSR, the forwarding plane will consult the ILM entry and either use a hashing algorithm to
map it to one of the NHLFEs if they exist (swap label) or simply route the packet if there are no
NHLFEs (pop label).
Static FEC swap will not be activated unless there is a matching route in system route table that
also matches the user configured static FEC next-hop.
Link LDP
Hello adjacency will be brought up using link Hello packet with source IP address set to the
interface borrowed IP address and a destination IP address set to 224.0.0.2.
By default, the LDP session uses the system interface address as the LSR-ID unless explicitly
configured using the command config>router>ldp>interface-parameters>interface>local-lsr-
id interface. Using this command user is allowed to use the local interface as both the LSR-ID and
the transport address for the link-level LDP session. Note that when the interface option is
selected, the transport connection (TCP) for the link LDP session will also use the address of the
local LDP interface as the transport address. If system is the value configured under the command
configure>router>ldp>interface-parameters>interface>transport-address, it will be
overridden.
The LSR with the highest transport address, that is, LSR-ID in this case, will bootstrap the TCP
connection and LDP session.
Source and destination IP addresses of LDP packets are the transport addresses, that is, LDP LSR-
IDs of systems A and B in this case.
Targeted LDP
Source and destination addresses of targeted Hello packet are the LDP LSR-IDs of systems A and
B.
The user can configure the local-lsr-id option on the targeted session and change the value of the
LSR-ID to either the local interface or to some other interface name, loopback or not. If the local
interface is selected the IP address of the local interface will be used as the LSR-ID. In all cases,
the transport address for the LDP session and the source IP address of targeted Hello message will
be updated to the new LSR-ID value.
The LSR with the highest transport address, that is, LSR-ID in this case, will bootstrap the TCP
connection and LDP session.