Introduction
Page 30 7750 SR OS Services Guide
Figure 1: Unicast Service Queue Mapping to Multiple Destination Based Hardware Queues
Ingress Shared Queuing
To avoid the hardware queue expansion issues associated with normal service based queuing, the
system allows an ingress logical service queue to map to a single hardware queue when shared
queuing is enabled. Shared queuing uses two passes through the ingress forwarding plane to
separate ingress per service queuing from the destination switch fabric queuing. In the case of
shared queuing, ingress unicast service queues are created one-for-one relative to hardware
queues. Each hardware queue representing a service queue is mapped to a special destination in
the traffic manager that ‘forwards’ the packet back to the ingress forwarding plane allowing a
second pass through the traffic manager. In the second pass, the packet is placed into a ‘shared’
queue for the destination forwarding plane. The shared queues are used by all services configured
for shared queuing.
When the first SAP or SLA profile instance is configured for shared queuing on an ingress
forwarding plane, the system allocates eight hardware queues per available destination forwarding
plane, one queue per forwarding class. (Twenty four hardware queues are also allocated for
Unicast
Queue
Hardware
Queue
Hardware
Queue
Hardware
Queue
Hardware
Queue
Unicast
SF Egres s
MDA 1
SF Egres s
MDA 2
SF Egres s
MDA 3
SF Egres s
MDA n
Backp res s ure Throug h
Switch Fabric Based on
Class
Unicast Service Queue is
Represented by Multiple SF
destination Hardware
Queues
IOM Monitors Individual Destination
Hardware Queues Based on Offered
Load and Forwarded Rate to Determine
Each Queues Operating Parameters (CIR,
PIR …) Relative to the Service Queue
Multicas
t
Queue
Multipoint Service Queue is
Represented by a Single
Hardware Queue (Single Pass)
Hardware
Queue
Multicast
Switch Fabric
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