Quality of Service

svbyrne · ‎10-09-2013

hello

I am using a quality of service policy outbound on a symmetrical 4Mbs interface

the link shows rx utilisation average 144/255 with low tx average 24/255

my policy map sets a bandwidth figure of 800 for my default class

policy-map test

class class-default

bandwidth 800

random-detect

I understand that the bandwidth figure sets a minimum bandwidth in the event of congestion

Because I have set the service policy outbound

Q will my bandwidth configuration monitor congestion on the tx load only ?

I am using the show policy-map int x to monitor statistics : drops etc do not seem to match my tx/rx load trends

there is a small amount of drops relative to the load on the line

Wantser1981_2 · ‎10-10-2013

Hi,

If you have applied the service policy in an outbound direction, only outbound traffic is subject to the terms of your policy.

The fact is that you cannot really do much to control the rx on the recieving router as the traffic is already consuming the bandwidth by the time you hit the RX queue. You would need to restrict the flows on the up-stream router outbound (if uder your control)

The other thing to note is your policy doesn't really achieve anything, which is why you might be seeing odd results.

Effectively you are adding a bandwidth guarantee to the same traffic that can congest the interface. IE, you are adding a reservation for default traffic, when default traffic is all that is going to be coming through the interface because you are not classifying anything else.

HTH

Wantser

svbyrne · ‎10-10-2013

hello

sorry I should have explained there are other classes

class AF2

mat access-group AF2

police 1500 set exceed action AF22

class Af4

match access-group AF4

police 1000 set exceed action AF42

I will send on the full configuration

Joseph W. Doherty · ‎10-10-2013

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Posting

I understand that the bandwidth figure sets a minimum bandwidth in the event of congestion

For CBWFQ, yes and no. It really controls (de)scheduler priorities, but when configured with an absolute number, it should guaranteed at least that much bandwidth, on average.

Because I have set the service policy outbound

Q will my bandwidth configuration monitor congestion on the tx load only ?

Not 100% sure what you believe "monitor congestion" means especially with "only", but an outbound policy does work with tx.

I am using the show policy-map int x to monitor statistics : drops etc do not seem to match my tx/rx load trends

there is a small amount of drops relative to the load on the line

Well you can have zero drops at 100% loading and high drops with 1% load; with what you've posted, there's insufficient information to comment further.

svbyrne · ‎10-10-2013

please see output from show poicy-map interface above

please see part of the QoS configuration applied below..

poicy applied outbound

note layer 3 configuration is on the WAN sub-interface f0/0.99

service policy is applied to the physical interface f0/0

therefore as I understand it the QoS configuration will have no impact on RX load

Joseph W. Doherty · ‎10-10-2013

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