Avaya BSGx4e CLI User's Guide download pdf (Page 91)

3 Configuration commands QoS (GoS) commands

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qos group

Use this command to configure a quality group. A quality group is the

definition of a Guarantee of Service (GoS) treatment, including bandwidth,

policing, and GoS class.

Note:

z The GoS link must be configured before the quality groups that

reference that link.

z Ten percent of link capacity is always reserved for Best Effort traffic.

Thus, no more than 90% of the link rate can be explicitly committed to

other quality groups. In other words the sum of the committed rates for

all other quality groups must not be greater than 90% of the link rate.

Consider the following when configuring GoS quality groups:

z When a quality group specifies committed access rate (CAR) policing,

traffic can be downgraded and discarded, as follows:

 Traffic received below the committed rate is entirely protected.

 Traffic received between the committed rate and the burst rate is

downgraded; it becomes best effort (BE) traffic. Traffic assigned to BE

is forwarded only if bandwidth is available. If bandwidth is not

available, the traffic is discarded; thus, the forwarding of downgraded

traffic is not guaranteed.

 Traffic received above the burst rate is discarded (traffic is out of

contract).

When a quality group specifies strict policing (POLICED), traffic is managed

as follows:

 Traffic received below the committed rate is entirely protected.

 Traffic received above the committed rate is discarded (traffic is out of

contract).

z Traffic can be discarded even when the average theoretical throughput

of the flow is within contract. This can happen when the traffic source is

bursting and packets are being deterministically dropped.

z Packet loss is typically due to peak traffic; however, it can also occur if

an incorrect load estimate was made.

For example, suppose up to fifteen VoIP calls can be set up

simultaneously, but the quality group to protect VoIP traffic is sized to

protect only ten calls. Calls are then dropped because of configuration

error, not because of extraordinarily high traffic. So, to avoid dropped

calls, sufficient bandwidth must be protected by the quality group to

accommodate the total number of possible calls.

When a GoS link is created, a default quality group assigned to BE (Best

Effort) is automatically created. This default quality group does not

prioritize traffic, and it is not shown when you enter show quality group.

However, this BE quality group exists to serve as default traffic manager for

the traffic flows which are not assigned to any other quality group.

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Avaya BSGx4e CLI User's Guide Page 91

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