Slide 1 11 May 2008

Point-to-Multipoint in 802.1Qay

Nurit Sprecher, Nokia Siemens Networks

Hayim Porat, Ethos Networks

Slide 2 11 May 2008

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).

Slide 3 11 May 2008

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.

Slide 4 11 May 2008

Different options for point-to-multipoint TE service instances in 802.1Qay

1. One point-to-multipoint TE service instance in the PBB-TE region

per point-to-multipoint customer service (which does not scale)

2. 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.

Slide 5 11 May 2008

Point-to-multipoint TE service instance per group of point-to-multipoint customer services

Two Multicast Groups :ABD, AC

Distributed to all branches

Or

Inefficient

BW Utilization A

B

C

D

Slide 6 11 May 2008

Point-to-multipoint TE service instance per group of point-to-multipoint customer services

Two Multicast Groups :ABD, AC

Distributed to all branches

Or

Split based on MAC address

A

B

C

D

Point-to-multipoint TE Service Instance per

customer service

Slide 7 11 May 2008

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.

Slide 8 11 May 2008

Different options for protection switching (Contd.)

• 1:1 point-to-point protection:

1. 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.

2. 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.

Slide 9 11 May 2008

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.

Slide 10 11 May 2008

Thank You

Slide 11 11 May 2008

Backup Slides

Slide 12 11 May 2008

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.

Slide 13 11 May 2008

A

B

C

D

Segment-based Protection (e.g. per branch)

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.

MEPs need to be defined to monitor the healthy of the segments

ESP-VID translation is needed

Slide 14 11 May 2008

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.

Slide 15 11 May 2008

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.