Subject: [Teas] Tunnel Termination Point in TE Topology Model

From: Xufeng Liu <[email-masked]>
Date: Mon, 1 Feb 2016 03:33:21 +0000

Authors and contributors of draft-ietf-teas-yang-te-topo are discussing the topic to add Tunnel Termination Point (TTP) to the TE topology model. The purpose is to provide useful information for path computation and tunnel setting up based on the topology. TTP also brings the relationship between TE topology model and TE tunnel model.

The related use cases include:

1)   Setting up a WDM tunnel.

When a tunnel is requested to be set up from the ingress to the egress, a path is computed to consist of a sequence of TE links. At ingress, the WDM tunnel needs to start from a WDM device rather than the end point of the first link. There is relationship between this terminating WDM device and the link end point. This WDM device is the Tunnel Termination Point (TTP).

   ..............                                               ..............

   .            .                                               .            .

   .  +-o--o-+  .                                               .  +-o--o-+  .

   .  |      |*****************************************************|      |  .

   .  +-o--o-+  .                                               .  +-o--o-+  .

   .       |    .                                               .    |       .

   .       |    .                                               .    |       .

   .       |    .                                               .    |       .

   .  +-o--o-+  .                                               .  +-o--o-+  .

   .  |      |  .                                               .  |      |  .

   .  +-o--o-+  .   .......           .......         .......   .  +-o--o-+  .

   ........|.....   .     .           .     .         .     .   .....|........

           +--------o     o-----------o     o---------o     o--------+

                    .......           .......         .......

2)   Setting up an MPLS PSC tunnel on real nodes.

When an MPLS PSC tunnel is set up from the ingress to the egress, the tunnel is identified by <ingress-address, egress-address, tunnel-id>. The ingress IP address is the Tunnel Termination Point (TTP). Additional TTP is not needed in the model. However, to make the TTP concept generic, we can use the ingress IP address as the TTP in the ingress node.

   ..............                                               ..............

   .            .                                               .            .

   .            *************************************************            .

   .            .                                               .            .

   .  +-o--o-+  .                                               .  +-o--o-+  .

   .  |      |  .                                               .  |      |  .

   .  +-o--o-+  .   .......           .......         .......   .  +-o--o-+  .

   ........|.....   .     .           .     .         .     .   .....|........

           +--------o     o-----------o     o---------o     o--------+

                    .......           .......         .......

3)   Setting up a PSC tunnel on abstract nodes.

When a PSC tunnel is requested to be set up from the ingress abstract node to the egress abstract node, a path is computed to start and stop at abstract nodes. The ingress abstract node represents a group of nodes. In such a case, the tunnel starts from one particular node inside the abstract node, and its IP address is the TTP in the ingress abstract node.

   ..............                                               ..............

   .   .......  .                                               .  .......   .

   .   .     .  .                                               .  .     .   .

   .   .     .*****************************************************.     .   .

   .   .......  .                                               .  .......   .

   .      |     .                                               .     |      .

   .      |     .                                               .     |      .

   .   .......  .                                               .  .......   .

   .   .     .  .                                               .  .     .   .

   .   .     .  .                                               .  .     .   .

   .   ...o...  .   .......           .......         .......   .  ...o...   .

   .......|......   .     .           .     .         .     .   ......|.......

          +---------o     o-----------o     o---------o     o---------+

                    .......           .......         .......

The proposed model addition is:

augment /nw:networks/nw:network/nw:node:

   +--rw te!

      +--rw te-node-id                  te-node-id

      +--rw config

      |  +--rw te-node-template*     leafref {template}?

      |  +--rw te-node-attributes

      +--ro state

      |  +--ro te-node-template*           leafref {template}?

      |  +--ro te-node-attributes

      +--rw tunnel-termination-point* [tunnel-tp-id]

         +--rw tunnel-tp-id    binary

         +--ro state

            +--ro switching-capability?     identityref

            +--ro encoding?                 identityref

            +--ro termination-capability* [link-tp]

               +--ro link-tp    leafref

Any comments are welcome.

Thanks,

- Xufeng