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Point-to-Multipoint in 802.1Qay. Nurit Sprecher, Nokia Siemens Networks Hayim Porat, Ethos Networks. Background. The spanning tree is disabled in PBB-TE regions. Restoration is disabled when a failure occurs along a TE service instance. - PowerPoint PPT Presentation
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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.