Alcatel-Lucent 7450 Manual page 536

ECMP Support for LDP
If the LSR is to behave as a transit for a given IP prefix, LDP will program a swap operation for
the prefix in the forwarding engine. This involves creating an Incoming Label Map (ILM) entry in
the forwarding plane. The ILM entry will have to map an incoming label to possibly multiple
NHLFEs. If an LSR is an egress for a given IP prefix, LDP will program a POP entry in the
forwarding engine. This too will result in an ILM entry being created in the forwarding plane but
with no NHLFEs.
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.
Page 536 7450 ESS MPLS Guide