Nurit Sprecher, Nokia Siemens Networks
Hayim Porat, Ethos Networks
Slide 1 11 May 2008

•
The spanning tree is disabled in PBB-TE regions.
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Restoration is disabled when a failure occurs along a TE service instance.
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Protection switching is enabled instead, but only for point-to-point TE service instances .
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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

•
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.
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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

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

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Segment-based protection (e.g. per branch):
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The protection entity may be point-to-point or point-to-multipoint TE service instance.
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Requires the definition of MEPs on Network Provider ports of core bridges in a PBB-TE region
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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

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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

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
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Pre-configuration of a disjoint point-to-point TE service instance for each destination CBP, or by the
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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

Slide 11 11 May 2008

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Protection (data plane)
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Utilizes the pre-assigned capacity between nodes.
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50 ms is the target time for protection switching.
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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.
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Protection switching may be either unidirectional or bidirectional.
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Protection at link, trunk or circuit layers
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Optimization for specific topologies: Linear Protection, Ring Protection
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Restoration (distributed control plane, management plane)
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Utilizes any available capacity between nodes
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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.
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Any topology.
Slide 12 11 May 2008

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

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

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