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Multi-segment PW
A multi-segment PW includes multiple concatenated static or LDP PWs. Creating two PWs for a
cross-connect on a PE can concatenate the two PWs. Upon receiving a packet from one PW, the PE
removes the tunnel ID and PW label of the packet, adds the PW label of the other PW, and forwards
the packet over the public tunnel. Only static and LDP PWs can form a multi-segment PW.
As shown in Figure 84, to create a multi-segment PW between PE 1 and PE 4, you can concatenate
PW 1 and PW 2 on PE 2, and PW 2 and PW 3 on PE 3.
Figure 84 Multi-segment PW
Multi-segment PWs include intra-domain multi-segment PWs and inter-domain multi-segment PWs.
Intra-domain multi-segment PW
An intra-domain multi-segment PW has concatenated PWs within an AS. You can create an
intra-domain multi-segment PW between two PEs that have no public tunnel to each other.
As shown in Figure 85, there is no public tunnel between PE 1 and PE 4. There is a public tunnel
between PE 1 and PE 2 and a public tunnel between PE 2 and PE 4. To create an intra-domain
multi-segment PW between PE 1 and PE 4, you can perform the following operations:
1. Create a PW between PE 1 and PE 2 (PW 1) and a PW between PE 2 and PE 4 (PW 2).
2. Concatenate the two PWs on PE 2.
Intra-domain multi-segment PWs can fully use existing public tunnels to reduce end-to-end public
tunnels.
CE 1
PE
1
PE
4
PE
2
PE 3
PW 1
PW 3
CE 2
PW
2
MPLS or IP backbone
PW
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