Ldp Adjacency Capabilities - Nokia 7705 SAR-W Series Manual

Label Distribution Protocol
Dynamic Capability, as defined in RFC 5561, allows all FEC types to update the
enabled or disabled state after the LDP session initialization phase. An LSR informs
its peer that it supports Dynamic Capability by including the Dynamic Capability
Announcement TLV in the LDP initialization message. If both LSRs advertise this
capability, the user can enable or disable any of the above FEC types while the
session is up and the change takes effect immediately. The LSR then sends a SAC
capability message with the IPv4 or IPv6 SAC element having the D-bit (Disable-bit)
set or reset, or the P2MP capability TLV (IPv4 only) in a capability message with the
S-bit (State-bit) set or reset. Each LSR then takes the consequent action of
withdrawing or advertising the FECs of that type to the peer LSR. If one or both LSRs
did not advertise the Dynamic Capability Announcement TLV in the LDP initialization
message, any change to the enabled or disabled FEC types only takes effect the
next time the LDP session is restarted.
The user can enable or disable a specific FEC type for a given LDP session to a peer
by using the following CLI commands:

5.4.5 LDP Adjacency Capabilities

Adjacency-level FEC-type capability advertisement is defined in draft-pdutta-mpls-
ldp-adj-capability. By default, all FEC types supported by the LSR are advertised in
the LDP IPv4 or IPv6 session initialization; see
information. If a given FEC type is enabled at the session level, it can be disabled
over a given LDP interface at the IPv4 or IPv6 adjacency level for all IPv4 or IPv6
peers over that interface. If a given FEC type is disabled at the session level, then
FECs will not be advertised and enabling that FEC type at the adjacency level will
not have any effect. The LDP adjacency capability can be configured on link Hello
adjacency only and does not apply to targeted Hello adjacency.
The LDP adjacency capability TLV is advertised in the Hello message with the D-bit
(Disable-bit) set or reset to disable or enable the resolution of this FEC type over the
link of the Hello adjacency. It is used to restrict which FECs can be resolved over a
given interface to a peer. This provides the ability to dedicate links and data path
resources to specific FEC types. For IPv4 and IPv6 prefix FECs, a subset of ECMP
links to an LSR peer may be configured to carry one of the two FEC types. An mLDP
P2MP FEC (IPv4 only) can exclude specific links to a downstream LSR from being
used to resolve this type of FEC.
414
• config>router>ldp>session-params>peer>fec-type-capability>prefix-ipv4
• config>router>ldp>session-params>peer>fec-type-capability>prefix-ipv6
• config>router>ldp>session-params>peer>fec-type-capability>p2mp
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LDP Session Capabilities
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