MPLS and RSVP
7450 ESS MPLS Guide Page 67
Figure 14: MPLS-TP PW Information Model
In the PW information model shown in Figure 14, the MS-PW is identified by the PW Path ID that
is composed of the full AGI:SAII:TAII. The PW Path ID is also the MEP ID at the T-PEs, so a
user does not have to explicitly configure a MEP ID; it is automatically derived by the system. For
MPLS-TP PWs with static labels, although the PW is not signaled end-to-end, the directionality of
the SAII and TAII is taken to be the same as for the equivalent label mapping message i.e. from
downstream to upstream. This is to maintain consistency with signaled pseudowires using FEC
129.
On the system, an S-PE for an MS-PW with static labels is configured as a pair of spoke-sdps
bound together in an VLL service using the VC-switching command. Therefore, the PW Path ID
configured at the spoke-SDP level at an S-PE must contain the Global-ID, Node-ID and AC-ID at
the far end T-PEs, not the local S-PE. Note that the ordering of the SAII:TAII in the PW Path ID
where static PWs are used should be consistent with the direction of signaling of the egress label
to a spoke-SDP forming that segment, if that label were signaled using T-LDP (in downstream
unsolicited mode). VCCV Ping will check the PW ID in the VCCV Ping echo request message
against the configured PW Path ID for the egress PW segment.
Figure 15 shows an example of how the PW Path IDs can be configured for a simple two-segment
MS-PW.
al_0228
MEPs MIP
PW_a
Note: PW Path ID is Structured
as per FEC129 All Type 2
meg_id =
pw_path_id
mep_id =
agi::global_id::
node_id::ac_id
mip_id =
node_id::0
pw_path_id =
agi::saii::taii
Primary
T-PE X S-PE A S-PE B T-PE Y
MIP
MIP
PW_b
Secondary
global_id
node_id
S-PE C S-PE D
MIP
MEPs
MEG
To Next Page
Loading...
