QOS

[mjindal01]

Hello i have one Adtran router. There is QOS policy configured on it. Below is the config:

qos map voice 1

  match dscp 46

  priority unlimited

I want to know to know the meaning of priority unlimited. Does it means that

a) When the qos policy traffic will come it will use the whole bandwidth of the link.

b) The whole bandwidth of the link is reserved for qos policy traffic.

c) When congestion will take place only in that case the whole bandwidth of the link will be used by the qos policy traffc.

Out of these which one is correct?

If all are wrong then please tell me the exact meaning of it.

Regards,

Mukesh Kumar
Network Engineeer
Spooster IT Services

[jayh]

mjindal01 wrote:

Hello i have one Adtran router. There is QOS policy configured on it. Below is the config:

qos map voice 1

  match dscp 46

  priority unlimited

I want to know to know the meaning of priority unlimited. Does it means that

a) When the qos policy traffic will come it will use the whole bandwidth of the link.

b) The whole bandwidth of the link is reserved for qos policy traffic.

c) When congestion will take place only in that case the whole bandwidth of the link will be used by the qos policy traffc.

Out of these which one is correct?

If an incoming packet has DSCP set to 46, it will be placed in the priority queue without restriction and sent first, with other traffic being queued.

This has the capability of choking out all other traffic is there is more DSCP 46 tagged traffic than available bandwidth. To avoid this possibility you can limit the amount of tagged traffic that will be prioritized by specifying a bandwidth limitation as opposed to "unlimited".

Your choice "c" is closest to being correct but there are some differences between the priority queue (send this first without delay) and bandwidth reservation (OK to queue but don't drop).

DSCP 46 is for "expedited forwarding" delay-sensitive traffic such as real-time voice payload. This differs from "assured forwarding" typically used for critical signaling.

[mjindal01]

Thanks for the information Jayh.

Regards,
Mukesh Kumar
Network Engineer
Spooster IT Services