PointtoMultipoint 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.

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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
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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
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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
• 11 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.

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Different options for protection switching
(Contd.)

• 11 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
  11 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, 11 protection
  switching should be defined. It is recommended to
  adopt the 11 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
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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
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.
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11 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.
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11 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.