Alcatel-Lucent 7450 Manual page 669

Session Parameters Commands
dod-label-distribution
Syntax [no] dod-label-distribution
Context config>router>ldp>session-parameters>peer
Description
This command enables the use of the LDP Downstream-on-Demand (DoD) label distribution
procedures.
When this option is enabled, LDP will set the A-bit in the Label Initialization message when the LDP
session to the peer is established. When both peers set the A-bit, they will both use the DoD label
distribution method over the LDP session (RFC 5036).
This feature can only be enabled on a link-level LDP session and therefore will apply to prefix labels
only, not service labels.
As soon as the link LDP session comes up, the 7x50 will send a label request to its DoD peer for the
FEC prefix corresponding to the peer's LSR-id. The DoD peer LSR-id is found in the basic Hello
discovery messages the peer used to establish the Hello adjacency with the 7x50.
Similarly if the 7x50 and the directly attached DoD peer entered into extended discovery and
established a targeted LDP session, the 7x50 will immediately send a label request for the FEC prefix
corresponding to the peer's LSR-id found in the extended discovery messages.
However, the 7x50 node will not advertise any <FEC, label> bindings, including the FEC of its own
LSR-id, unless the DoD peer requested it using a Label Request Message.
When the DoD peer sends a label request for any FEC prefix, the 7x50 will reply with a <FEC, label>
binding for that prefix if the FEC was already activated on the 7x50. If not, the 7x50 replies with a
notification message containing the status code of "no route." The 7x50 will not attempt in the latter
case to send a label request to the next-hop for the FEC prefix when the LDP session to this next-hop
uses the DoD label distribution mode. Hence the reference to single-hop LDP DoD procedures.
As soon as the link LDP session comes up, the 7x50 will send a label request to its DoD peer for the
FEC prefix corresponding to the peer's LSR-id. The DoD peer LSR-id is found in the basic Hello
discovery messages the peer used to establish the Hello adjacency with the 7x50.
Similarly if the 7x50 and the directly attached DoD peer entered into extended discovery and
established a targeted LDP session, the 7x50 will immediately send a label request for the FEC prefix
corresponding to the peer's LSR-id found in the extended discovery messages. Peer address has to be
the peer LSR-ID address.
The no form of this command disables the DoD label distribution with an LDP neighbor.
Default
no dod-label-distribution
7450 ESS MPLS Guide Page 669