Services
7750 SR OS Services Guide Page 33
area). Multipoint packets in a multipoint service (VPLS, IES and VPRN) use significant resources
in the system, consuming ingress forwarding plane multicast bandwidth and egress replication
bandwidth. Usually, the per service unicast forwarding queues are not rate limited to a degree that
allows adequate management of multipoint packets traversing them when multipoint shared
queuing is enabled. It is possible to minimize the amount of aggregate multipoint bandwidth by
setting restrictions on the multipoint queue parameters in the QoS node’s Shared Queue policy.
Aggregate multipoint traffic can be managed per forwarding class for each of the three forwarding
types (broadcast, multicast or unknown unicast – broadcast and unknown unicast are only used by
VPLS).
A second disadvantage to multipoint shared queuing is the fact that multipoint traffic now
consumes double the ingress forwarding plane bandwidth due to dual pass ingress processing.
Figure 4: Multipoint Shared Queuing Using First Pass Unicast Queues
Second
Pass
Service
Queue
Hardware
Queue
Unicast Service Queue is Represented by a Single Hardware
Queue But Dual Pass through the Forwarding Plane
Hardware
Des t Queue
Hardware
Des t Queue
Hardware
Des t Queue
Hardware
Des t Queue
Unicast
SF Egres s
MD A 1
SF Egres s
MD A 2
SF Egres s
MD A 3
SF Egres s
MD A n
Multi cas t
Queue
Multipoint Service Queues are Ignored (Not Created) and
Multipoint Packets use First Pass Unicast Service Queues.
Second Pass Multipoint Packets Use Shared Multipoint
Queues.
Hardware
Queue
Multicast
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