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

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Point-to-Multipoint in 802.1Qay

Nurit Sprecher, Nokia Siemens Networks

Hayim Porat, Ethos Networks

Slide 1 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 2 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 3 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 pointto-multipoint customer services which may result either in inefficient link utilization (traffic is replicated to all branches), or in one point-tomultipoint TE service per point-to-multipoint customer service in the

PBB-TE region.

Slide 4 11 May 2008

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

Inefficient

BW Utilization

A

Two Multicast Groups:

ABD , AC

Distributed to all branches

Or

B

C

D

Slide 5 11 May 2008

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

Point-to-multipoint TE

Service Instance per customer service

A

Two Multicast Groups:

ABD , AC

Distributed to all branches

Or

Split based on MAC address

B

C

D

Slide 6 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 7 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-tomultipoint customer service, this result in a better resource utilization as the protection point-topoint 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-topoint TE service instances.

This does not require any modification to the protection switching mechanism which is defined in 802.1Qay.

Slide 8 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 9 11 May 2008

Slide 10 11 May 2008

Thank You

Backup Slides

Slide 11 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 12 11 May 2008

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

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

A ESP-VID translation is needed

B

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-tomultipoint TE service instance.

Slide 13 11 May 2008

D

C

1:1 point-to-point protection with disjoint point-topoint TE service instance for each destination CBP

A

B

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 14 11 May 2008

D

C

1:1 point-to-point protection with Point-tomultipoint service delivery over full-mesh point-topoint 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-topoint TE service instances need to be set-up for each point-to-point TE service instance.

Slide 15 11 May 2008

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