Traffic Management Support - Alcatel-Lucent 7750 SR Manual

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Traffic Management Support

Ingress Network Classification

Classification is based on the EXP value of the pseudowire label and EXP-to-FC mapping is

determined by the network ingress QoS policy.

Ingress Queuing and Shaping on the IOM

Each SAP of an ATM VLL has an associated single ingress service queue on the IOM. The default

QoS policy configures this queue to have CIR=0 and PIR=line rate. Other QoS policies can be

applied if they specify a single service queue. Applying a non-default QoS policy allows the CIR/

PIR of the incoming traffic to be controlled, regardless of whether ATM policing is configured,

and provides queuing and shaping to smooth traffic flows on the ingress of the network.

Egress Queuing and Shaping on the IOM

Each SAP of an ATM VLL has a single associated egress service queue on the IOM. The default

QoS policy configures this queue to have CIR=0 and PIR=line rate. Other QoS policies can be

applied if they specify a single service queue. Applying a non-default QoS policy allows the CIR/

PIR of the outgoing traffic to be controlled, regardless of whether ATM shaping is configured.

Egress Shaping/Scheduling

Each SAP of an ATM VLL has an egress ATM traffic descriptor associated with it. The default

traffic descriptor has service category UBR with zero MIR, resulting in endpoints associated with

this descriptor being scheduled at the lowest priority on the ATM MDA. Egress traffic may be

shaped or scheduled, depending on the configuration of the egress ATM traffic descriptor

associated with the SAP.

shaping settings affect egress transmission rates.

Shaping applies to CBR, rtVBR and nrtVBR service categories and results in cells being

transmitted in such a way as to satisfy a downstream ATM UPC function. In particular, the

transmission rate will be limited (in the case of CBR, there is a hard limit of PIR, while rtVBR/

nrtVBR will transmit at SIR with short (constrained by MBS) bursts of up to PIR), and the inter-

cell gap will also be controlled.

Service category UBR and rtVBR are scheduled on the WRR scheduler with the configured rates

(MIR for UBR+) determining the weight applied to the flow. Weights are between 1 and 255 and

are determined by a formula applied to the configured rate. UBR flows (for example, those with

7750 SR OS Services Guide

provides details of how the different service categories and

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