Re: qos rate limiting

rajath4444 · ‎12-21-2012

Hi All,

I have a specific requirement .

On a 5 Mbps link - rate limit voice traffic with 3 Mbps and other traffic to 2 Mbps.

And whenever we donot have any voice traffic assign complete 5 Mbps to other traffic.

Can someone please help me in choosing the best QOS mechanism to accomplish this request.

siddhartham · ‎12-21-2012

You can use MQC and configure somehing link below to achieve this

class-map match-any voice

match dscp ef

class-map match-any signaling

match dscp af31

policy-map qos

class voice

priority percent 40

set ip dscp ef

class signaling

set ip dscp af31

bandwidth remaining percent 20

class class-default

set ip dscp default

bandwidth remaining percent 80

service-policy output qos ----- on your outgoing interface.

QoS is a end to end config, your service provider should honour your markings other wise they wont carry over.

Siddhartha

Terry Cheema · ‎12-21-2012

In addition to what Siddhartha has recommended:

policy-map PARENT

class class-default

shape average 5120000 <<<<< Rate limit your link to 5Mb

policy-map qos <<< This is the child policy specified in the above post.

int XX -- Outgoing interface

service-policy output PARENT <<< instead of applying the policy qos as mentioned in the above post specify PARENT, it will apply both.

Also you under you class maps you can also add some other criteria as well for matching the traffic (ACLs, protocols etc)

Hope it helps!

Terry

Mark Combs · ‎12-21-2012

Please be keep in mind that only 75% of the bandwidth is available by default on your wan interface so you should take this in consideration when desiging different classes and QOS policies. You can change this behavior with the max reserve bandwidth command on the WAN interface and change it to 100% which basically tells the router that 100% of the bandwidth is available for allocation. However, depending on how congested this link is at times you could potentially mess with routing protocol updates and cause circuit flaps if too many of the hello messages are dropped. This is what the 25% was originally reserved for along with other "router type" traffic.

You might be thinking that 25% is a lot to reserve for hello messages and such. I would tend to agree which is why I see so many configurations nowadays that make a special class for CS6 which is where your protocols run. Give that class just what it needs.

But as Siddhartha pointed out QOS is end-to-end and you really should check with the provider on what type of QOS markings they honor. Many ISPs only honor a few different classes. If this is a point to point then its a moot point (no pun intended)

- Mark

Joseph W. Doherty · ‎12-22-2012

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Mark Combs wrote:

Please be keep in mind that only 75% of the bandwidth is available by default on your wan interface so you should take this in consideration when desiging different classes and QOS policies.

Note: that's true with pre-HQF CBWFQ; HQF changed some of the "rules".

Mark Combs wrote:

You might be thinking that 25% is a lot to reserve for hello messages and such.

Also note: re: "reserve" - CBWFQ bandwidth setting sets a minimum guarantee. I.e. unused bandwidth is available to other non-LLQ classes.

Mark Combs · ‎12-22-2012

I stand corrected. I didnt see the bandwidth remaining part and thought it was bandwidth percent only. Your correct about the pre-HQF.

Joseph W. Doherty · ‎12-22-2012