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are terminated. The traffic in both these directions is typically admitted into the ring after being
shaped and groomed. That is in the upstream direction (that is, in the direction of customer to
service edge) the SLA is enforced at service ingress points (that is, typically access SAPs) and the
traffic is shaped and groomed in the downstream direction (that is, in the direction of service edge
to customer) by the service edge device or the access aggregation device. In other words, this
traffic should typically be allowed to pass through the intermediate nodes of the ring, without
contention with and prioritized over the traffic that is received from the customer and being added
into the ring by the nodes on the ring. The access-uplink ports are designated as 'ring' ports and
access ports are designated as 'non-ring' ports. Traffic going any access-uplink to another access-
uplink port is identified as 'ring' traffic. Traffic going from an access port to any access-uplink
port, or traffic going from any access-uplink port to an access port (in egress), or traffic going from
an access port to another access port is identified as 'non-ring' traffic.
To ensure that the traffic received on ring ports is prioritized over traffic received on non-ring
access ports, a separate 'Ring' MBS buffer pool (one each for ingress and egress) is provided for
traffic received and sent out of access-uplink port. In addition, the access-uplink egress (where
shaped customer (access) traffic and 'ring' traffic share the 'ring' pool) two additional ring slopes
(for a total of 4 configurable WRED slopes) are provided to prioritize the 'ring' traffic. Each
egress queue on the access uplink port supports 4 slopes per queue – ring high-slope, ring low-
slope, non-ring high-slope and non-ring low-slope (in the CLI command the ring slopes are
configured using the high-slope-ring and low-slope-ring and the non-ring slopes are configured
using the high-slope and low-slope). Ring high-slope and Ring low-slope is used for in-profile and
out-of-profile QoS profile 'ring' traffic. Non-ring high-slope and low-slope is used for in-profile
and out-of-profile 'non-ring' traffic. Slope parameters (start-avg, max-avg, max-Prob) of 4 slopes
can be configured such that the ring traffic is prioritized over the 'non-ring' traffic (that is, traffic
being added onto the ring) in congestion scenarios.
A separate 'non-Ring' MBS buffer pool for traffic received and sent out of access ports along with
2 configurable WRED slopes is supported. Each queue on the access ports supports 2 slopes per
queue –non-ring high-slope and non-ring low-slope. Non-ring high-slope and low-slope is used for
in-profile and out-of-profile 'non-ring' traffic. The Non-Ring buffer pool (one each for ingress and
egress) is used to allocate buffers for non-ring traffic.
The usage of buffer pools for different traffic flows is as given below (also depicted in the picture
below):
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•
7210 SAS D, E, K OS Quality of Service Guide
Traffic received on access-uplink SAP and sent out of access-uplink SAP, uses the ring
MBS buffer pool for MBS buffers on access-uplink port ingress and access-uplink port
egress. In this case, ring high-slope is used for in-profile traffic and ring low-slope is used
for out-of-profile traffic for both access-uplink ingress and access-uplink egress.
Traffic received on access SAP and sent out of access-uplink SAP, uses the non-ring MBS
buffer pool for MBS buffers on access SAP ingress and uses the ring MBS buffer pool for
MBS buffers on access-uplink SAP egress. In this case, non-ring high slope and non-ring
low slope is used on both access ingress and access-uplink egress.
QoS Policies
Page 65
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