Resolving Oversubscription
Following are the two high-level tasks which need to performed to resolve the bandwidth oversubscription
on the ingress side:
•
Classifying the incoming traffic as high priority and low priority. Depending on the SPA type, the
classification is done by either a SIP or a SPA.
•
Scheduling the high-priority packets first and then processing the low-priority traffic. Depending on the
scheduling configuration, weight can be assigned to low-priority packets.
Ingress Classification Overview
To solve the bandwidth oversubscription issue, packets must be classified as high-priority data traffic and
control traffic, and guarantee their transmit to the QFP. Ingress Classification can be broadly divided into
two:
•
SPA-based classification
—
Some of the SPAs support the classification performed within the SPA
hardware.
•
SIP-based classification
—
SPAs rely on the classification performed inside the CC.
The SPAs supported on a Cisco ASR 1000 Series Aggregation Services Router can be broadly classified into
the following categories:
•
Ethernet SPAs
—
Fast Ethernet (FE), 1-Gigabit Ethernet (GE), 10-Gigabit Ethernet SPAs
•
ATM SPAs
—
OC3 and OC12 flavours
•
Channelized SPAs
—
ChT1/ E1, ChT3/ DS0, ChSTM1/ OC3, and ChOC12/ DS0 SPAs
•
Clear Channel SPAs
—
T3/ E3 and 12-in-1 SPAs
•
POS SPAs
—
OC3, OC12, OC48, and OC192 flavors
The Ethernet and ATM SPAs have classification capability at the SPA level, while the other types of SPAs
rely on the SIP for ingress classification.
Note
The following table shows the classification models followed by the various SPAs:
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
Everest 16.5
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Classifying and Scheduling Packets for the ASR 1000 Series Aggregation Services Routers
Resolving Oversubscription