|
Hi All! I extracted this concept from RTN905 product description in hedex file V1R5 version and I want to shared with you because I think it?s very interesting to undertand the concept of PWs and the difference between one deployment and another. Below you will find the description:
A PW that is carried in a PSN tunnel is called a single-segment PW (SS-PW). If a PW is carried in multiple PSN tunnels, the PW is called a multi-segment PW (MS-PW). MS-PW Network Reference Model Figure 1 shows the MS-PW network reference model. Figure 1 MS-PW network reference model http://localhost:7890/pages/31185815/04/31185815/04/resources/pfc/topic/image/tc_pfc_pwbsc_0007_fig01.png | T-PE: terminating provider edge | S-PE: switching provider edge | http://localhost:7890/pages/31185815/04/31185815/04/resources/public_sys-resources/icon-note.gif NOTE: PSN tunnels are available in several types, but the OptiX RTN 905 supports only MPLS tunnels. In this document, PWE3 is based on MPLS tunnels (LSPs), unless otherwise specified. In the preceding network reference model, T-PE1 and T-PE2 provide PWE3 services to CE1 and CE2. The PWs are carried in two PSN tunnels, and constitute the MS-PW. The two tunnels (PSN tunnel 1 and PSN tunnel 2) that are used to carry PWs reside in different PSN domains. PSN tunnel 1 extends from T-PE1 to S-PE1, and PSN tunnel 2 extends from S-PE1 to T-PE2. Labels of PW1 carried in PSN tunnel 1 and PW3 carried in PSN tunnel 2 are swapped at S-PE1. Similarly, labels of PW2 carried in PSN tunnel 1 and PW4 carried in PSN tunnel 2 are swapped at S-PE1. MS-PW Application Compared with the SS-PW, the MS-PW has the following characteristics: - Reduces required tunnel resources.
- Traverses different PSNs.
- Provides segment-based protection for tunnels.
The following paragraphs and figures compare the application scenarios of the SS-PW and MS-PW to show that it is easier for the MS-PW to implement segment-based protection for tunnels. Figure 2 shows the SS-PW networking mode. The services between PE1 and PE2 are transmitted on PW1 carried in MPLS tunnel 1. Both MPLS tunnel 1 and MPLS tunnel 2 are configured with 1:1 protection. Protection, however, fails to be provided if disconnection faults occur on different sides of the operator device (called the P device). Figure 2 SS-PW application
http://localhost:7890/pages/31185815/04/31185815/04/resources/pfc/topic/image/tc_pfc_pwbsc_0007_fig02.png
http://localhost:7890/pages/31185815/04/31185815/04/resources/public_sys-resources/icon-note.gif NOTE: The PWs are invisible to the P device on a PSN; the P device provides transparent transport in tunnels. Figure 3 shows the MS-PW networking mode. The services between T-PE1 and T-PE2 are transmitted on PW1 carried in MPLS tunnel 1 and PW2 carried on MPLS tunnel 2. The paired tunnels (MPLS tunnel 1 and MPLS tunnel 3; MPLS tunnel 2 and MPLS tunnel 4) are configured with 1:1 protection. In this configuration, protection can still be provided even when disconnection faults occur on different sides of the S-PE1 device. Figure 3 MS-PW application
http://localhost:7890/pages/31185815/04/31185815/04/resources/pfc/topic/image/tc_pfc_pwbsc_0007_fig03.png
Hope you like it! Best Regards! | 
Favorite (0)
Reply
