QoS configuration for 3750 switch WAN port?

[gwhuang5398]

We are using 3750 switches as WAN router facing the WAN cloud. To configure QoS for its WAN port, should I use 'auto qos voip trust" or treat it like a router port and configure class-maps, policy-maps, and attact service-policy input or output?

Because switches have different queuing and dropping methods than routers, auto qos can generate QoS configs that are considered most appropriate for 3750 switches. However the switch functions as WAN router. Maybe it should be configured using router type of QoS with policy-maps and service-policy?

Please advice.

Thanks

[Joseph W. Doherty]

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Posting

The non-metro version of the 3750, I recall, does not support outbound CBWFQ.  You're limited to the four egress queues, which you can proportionally weight and have one as a PQ.  You can also shape (roughly) the egress port's bandwidth if the contracted bandwidth is less than media bandwidth.

[Marwan ALshawi]

Just to add to to JosephDoherty post

you can use limited options in terms of QoS polices in the Cat swtiches comparing to a router

have a look at the bellow discussion it might be helpful for your

https://supportforums.cisco.com/message/3397944#3397944

HTH

if helpful Rate

[Mark Williams]

If your WAN link is anything other then 1000/100/10 you will not be able to shape traffic when using a switch

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Mark Williams wrote:
If your WAN link is anything other then 1000/100/10 you will not be able to shape traffic when using a switch

You might want to review: http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_58_se/configuration/guide/swqos.html#wp1253412

[Marwan ALshawi]

the link provided above by JosephDoherty is not shaping it is like policing the interface bandwidth

Mark is correct no shaping with a Switch

HTH

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

marwanshawi wrote:
 the link provided above by JosephDoherty is not shaping it is like policing the interface bandwidth 
Mark is correct no shaping with a Switch 
HTH

Policing or rate-limiting drops packets; shaping delays packets.  (Hopefully we agree.)

Consider in the above link "When you configure this command to 80 percent, the port is idle 20 percent of the time. The line rate drops to 80 percent  of the connected speed, which is 800 Mb/s. These values are not exact because the hardware adjusts the line rate in increments of six."

Idling the port shouldn't, I believe, drop all packets during the idle period.  If it did, then it would behave like a policer.  If this feature operated on the interface as a policer, rather that similar to a shaper, then even PQ packets would be dropped during the idle period; not too good.

Also as to "no shaping with a Switch", you might want to review the "srr-queue bandwidth shape" command in the same referenced document.

The advantage of idling the port, rather than using individual egress queue shapers, it then should behave some what similar to a CBWFQ hierarchal policy shaper with a child policy with proportional class bandwidths, i.e. using "srr-queue bandwidth share" with "srr-queue bandwidth limit".

PS:

The original poster might also want to post the original question in "ASK THE EXPERTS:LAN Switching", https://supportforums.cisco.com/message/3408554#3408554

[paul driver]

If i remember right - the auto qos feature is mainly aimed at VOIP - so if you havnt got to marked Voice traffic it would be worth appling it..

please if i am wrong please correect me?

res

Paul

[gwhuang5398]

We are doing this for VoIP. Auto QoS for VoIP would create many of those ingress and egress queuing configs that can be configured manually as well, like in the discussions.

When I started the discussion, I was just wondering if I needed to create a policy-map to apply to the port used as WAN port, similar to a router with LLQ and CBWFQ. But Joseph said the non-Metro 3750 switches don't support CBWFQ. So I guess I just can't create such a policy-map for that port.

So my option is to configure the ingress/egress queues, either using auto qos or doing it manually.

Please let me konw if I understand it correctly.

Thanks

[Marwan ALshawi]

i prefer doing it aith auto QoS then i change whatever things i need it to be done not part of the Auto QoS standard such as map diffrent COS or DSCP to diffrnet queues

HTH

if helpful Rate