QoS over Point-to-Point T1

mzinz · January 2008

I'm fairly new to QoS, so I have a few questions.

I'm trying to prioritize certain traffic which goes over a point-to-point T1. I would like to give VoIP traffic high priority.

One end terminates with a 7204, and the other end terminates with a 2821. Would both of these be suitable to handle the task?

Anything I should know ahead of time?

dtlokee · January 2008

Yah you can use LLQ to accomplish the goal. You need to classify the traffic somehow (it may already be marked by the phones as cs5 or EF). If it is not marked then you will need to classify it, NBAR will work here.

ip cef
!
class-map VOICE
match protocol rtp audio

then create a service policy

policy-map LLQ
class VOICE
priority 256

then apply to the interface:

interface serial 0/0/0
service-policy output LLQ

A word of warning, LLQ is a strict priority queue, it is serviced until it uses up it;s bandwidth allotment (in this case 256kb/s) and will also be policed to that rate so it is important you also use some form of CAC to restrict the total number of calls because if it exceedes the total allotment, the quality of all the calls will suffer.

Also you can add other classification and queueing methods to the policy to allow other traffic to have bandwidth allotments (use the bandwidth statement, not the priority statement fo these)

mzinz · January 2008

Thanks for the great reply, that really helps.

QoS over Point-to-Point T1

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