Solved: Serial Interface speed/bandwidth

snarayanaraju · ‎01-30-2010

Dear experts,

While trying to change the number of conversation in WFQ, I read that there is relation between the Interface bandwidth and Number of conversation queues in WFQ. For example, for 64 Kbps link No. of conversation is 16.

While testing this, even by changing the Interface Bandwidth command, there is not change in Number of conversation in WFQ. I am testing this using command "show interface ser 0/0".

Then I trying to change the Physical serial interface speed. I know "bandwidth" is not the command. Whether it is correct to use "clock rate" command or it is in the control of my ISP. Is there any possibility to set the serial interface bandwidth matching to the line speed??

thanks in advance

sairam

Giuseppe Larosa · ‎01-31-2010

Hello Sairam,

you are the usual digger....

Are you using WFQ directly on the interface as queueing method or have you added fair-queue in a class-default in a policy-map that is for a traffic-class in a CBWFQ context?

I've given a look at IOS QoS command reference and the table you were referring appears under:

fair-queue (class-default)

http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_d1.html#wp1019415

notice that the command reference reports more then one entry that are discriminated as:

fair-queue (class-default)

fair-queue (DWFQ)

fair-queue (policy-map class)

fair-queue (WFQ)

but then under the last fair-queue (WFQ) says:

>> (Optional) Number of dynamic queues used for best-effort conversations (that is, a normal conversation not requiring any special network services). Values are 16, 32, 64, 128, 256, 512, 1024, 2048, and 4096. See the tables in the fair-queue (class-default) command for the default number of dynamic queues.

So what you expect should happen also if using WFQ directly on the interface.

Hope to help

Giuseppe

View solution in original post

paolo bevilacqua · ‎01-31-2010

It is NOT possible to change bandwidht or speed of a serial interface connected to a WAN circuit.

View solution in original post

Giuseppe Larosa · ‎01-31-2010

Hello Sairam,

your understanding is correct:

speed is influenced by clock rate command but this can be given only on the DCE side of the link.

In a lab the router that has the DCE cable connected to its serial, in real world it is usually the provider side as you have noted

bandwidth is more an administrative parameter.

Hope to help

Giuseppe

snarayanaraju · ‎01-31-2010

Hi Giuseppe,

Thanks, But if I am asked or attempt to match the exact speed of the link, shall i configure the clock rate parameter only??

The reason for asking this is, I am not able to change the Number of WFQ conversation based on the interface bandwidth, even after changing the clock-rate & Bandwidth statement under the serial interface. It is mentioned in the Cisco QOS configuration 12.4 guide that WFQ conversation depands on the Interface Bandwidth. (Ofcourse I sure that using "fair-queue x y z, I can change the Dynamic conversation queues)

I am just experimenting this behaviour.

Thanks for your time.

sairam

Giuseppe Larosa · ‎01-31-2010

Hello Sairam,

you are the usual digger....

Are you using WFQ directly on the interface as queueing method or have you added fair-queue in a class-default in a policy-map that is for a traffic-class in a CBWFQ context?

I've given a look at IOS QoS command reference and the table you were referring appears under:

fair-queue (class-default)

http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_d1.html#wp1019415

notice that the command reference reports more then one entry that are discriminated as:

fair-queue (class-default)

fair-queue (DWFQ)

fair-queue (policy-map class)

fair-queue (WFQ)

but then under the last fair-queue (WFQ) says:

>> (Optional) Number of dynamic queues used for best-effort conversations (that is, a normal conversation not requiring any special network services). Values are 16, 32, 64, 128, 256, 512, 1024, 2048, and 4096. See the tables in the fair-queue (class-default) command for the default number of dynamic queues.

So what you expect should happen also if using WFQ directly on the interface.

Hope to help

Giuseppe

paolo bevilacqua · ‎01-31-2010

It is NOT possible to change bandwidht or speed of a serial interface connected to a WAN circuit.