Point-to-Multipoint in 802.1Qay

1. Point-to-Multipoint in 802.1Qay Nurit Sprecher, Nokia Siemens Networks Hayim Porat, Ethos Networks

2. Background • The spanning tree is disabled in PBB-TE regions. • Restoration is disabled when a failure occurs along a TE service instance. • Protection switching is enabled instead, but only for point-to-point TE service instances. • In the event of a failure along a point-to-multipoint TE service instance, traffic is not restored until the failure is eliminated (hours? days?). • In PBB-TE, no control protocol is enabled; configuration is controlled by an external agent. Only protection switching can be applied to point-to-multipoint TE service instances (as restoration requires control protocols).

3. Observations • In contrast to point-to-point TE service instances, it is difficult to set up point-to-multipoint TE service instances without knowledge of: • the point-to-multipoint customer services which are to be delivered over the PBB-TE region with their corresponding source CBP and destination CBPs. • This is due to the extremely high number of possible point-to-multipoint TE service instances that can be setup between N CBPs in a PBB-TE region. • The number of possible point-to-multipoint TE service instances consisting of 2 and above destination CBPs in a PBB-TE region consisting of N CPBs is ( 2 N – 1 – N ) * N.

4. Different options for point-to-multipoint TE service instances in 802.1Qay • One point-to-multipoint TE service instance in the PBB-TE region per point-to-multipoint customer service (which does not scale) • Using a point-to-multipoint TE service instance for a group of point-to-multipoint customer services which may result either in inefficient link utilization (traffic is replicated to all branches), or in one point-to-multipoint TE service per point-to-multipoint customer service in the PBB-TE region.

5. A B C D Point-to-multipoint TE service instance per group of point-to-multipoint customer services Inefficient BW Utilization Two Multicast Groups: ABD, AC Distributed to all branches Or

6. A B C D Point-to-multipoint TE service instance per group of point-to-multipoint customer services Point-to-multipoint TE Service Instance per customer service Two Multicast Groups: ABD, AC Distributed to all branches Or Split based on MAC address

7. Different options for protection switching • Segment-based protection (e.g. per branch): • The protection entity may be point-to-point or point-to-multipoint TE service instance. • Requires the definition of MEPs on Network Provider ports of core bridges in a PBB-TE region • Requires ESP-VID translation inside the PBB-TE region when protection switching occurs. Violates the scope of the domain-wide label of PBB-TE • May be a complex problem when there are sub-branches of sub-branches • 1:1 point-to-multipoint protection: To guarantee protection, disjoint point-to-multipoint TE service instances should be set-up. • This consumes a lot of resources, especially since, in practice, one point-to-multipoint TE service instance is allocated per point-to-multipoint customer service. • This puts a lot of constraints on the resource allocation algorithm, which may result in the inability to provision protected point-to-multipoint TE services.

8. Different options for protection switching (Contd.) • 1:1 point-to-point protection: • To guarantee protection, disjoint point-to-point TE service instance should be set-up for each destination CBP. • When a failure occurs along a particular branch from the source CBP to a destination CBP, a switchover is performed from the failed branch to the relevant protection point-to-point TE service instance, without affecting the entire point-to-multipoint TE service insatnce. • Although in practice one point-to-multipoint TE service instance is allocated per point-to-multipoint customer service, this result in a better resource utilization as the protection point-to-point TE service instances for the different destination CBPs do not need to disjoint. • This does not put additional constraints on the resource allocation algorithm as compare to the 1:1 point-to-point protection switching. • Point-to-multipoint customer services are delivered over full-mesh protected point-to-point TE service instances. • This does not require any modification to the protection switching mechanism which is defined in 802.1Qay.

9. Recommendations Since point-to-multipoint TE service instances should be adequately protected, 1:1 protection switching should be defined. It is recommended to adopt the 1:1 point-to-point protection switching either by the • Pre-configuration of a disjoint point-to-point TE service instance for each destination CBP, or by the • Delivery of point-to-multipoint customer services over full mesh protected point-to-point TE service instances.

10. Thank You

11. Backup Slides

12. Protection vs. Restoration • Protection (data plane) • Utilizes the pre-assigned capacity between nodes. • 50 ms is the target time for protection switching. • In the event of failure, the protection mechanism does not involve rerouting or an additional connection setup. Only the source and destination connection controllers are involved. • Protection switching may be either unidirectional or bidirectional. • Protection at link, trunk or circuit layers • Optimization for specific topologies: Linear Protection, Ring Protection • Restoration (distributed control plane, management plane) • Utilizes any available capacity between nodes • The algorithms used for restoration involve rerouting. When restoration is used, a percentage of the transport network capacity is reserved for the rerouting of working traffic. • Any topology.

13. ESP-VID translation is needed A B C D Segment-based Protection (e.g. per branch) MEPs need to be defined to monitor the healthy of the segments Note: for simplicity only one protection entity is presented, but protection entities need to be set-up for each segment to guarantee protection switching for the entire point-to-multipoint TE service instance.

14. A B C D 1:1 point-to-point protection with disjoint point-to-point TE service instance for each destination CBP Note: for simplicity only some protection point-to-point TE service instances are presented, but protection point-to-point TE service instances need to be set-up from the source BCP to each destination BCP.

15. 1:1 point-to-point protection with Point-to-multipoint service delivery over full-mesh point-to-point TE service instances Full-mesh protected point-to-point TE service instances. For simplicity only one protection point-to-point TE service instances are presented, but protection point-to-point TE service instances need to be set-up for each point-to-point TE service instance.