QoS IP-precedence

[Ralph John Tampilic]

Hi,

We implement QoS IP-Precedence in our network. But we have a problem in our Remote Sites with 2 Mbps / 4 Mbps. They received packet loss in their Polycom VideoConference.

Head Office (Polycom) ------> L2 switch ------> Voice Gateway ------> MPLS ------->Voice Gateway Remote Sites -------> L2 SW ----> Polycom.

Polycom equipment QoS set in IP precedence.

Here's my config:

class-map match-all Test_CONTROL

match ip precedence 3

class-map match-all Test_VIDEO

match ip precedence 4

class-map match-all Test_AUDIO

match ip precedence 5

policy-map TEST_QOS

class Test_VIDEO

bandwidth percent 43

set ip precedence 4

class Test_AUDIO

priority percent 4

set ip precedence 5

class Test_CONTROL

bandwidth percent 3

set ip precedence 3

class VOICE_CLASS

priority percent 15

class class-default

fair-queue

random-detect

int g0/2

service-policy output TEST_QOS

Adding questions:

May I know where I will apply the "mls qos" and "mls qos trust" command? Remote Sites have Catalyst 2950 Switch. Is this supported for mls qos trust ip-precedence command?

Thank you.

Regards,

Ralph

[cadet alain]

Hi,

on 2950 default port behaviour for IOS is untrust so Cos will be set to zero and cos-dscp mapping will be used to derive DSCP which will be zero so you should have no match in your policy-map.

the mls qos trust command is available only on EI images and you can trust on Cos or DSCP but not IP Precedence.

This command should be used to set the  trust  boundary on the access switches on ports connected to your Polycom devices.

Regards.

Alain

Don't forget to rate helpful posts.

[Ralph John Tampilic]

Hi Alain,

We found out that even we increased the bandwidth of the Site there is a RTO in WAN link. I think the issue must check first on the MPLS to resolved the RTO. Am I correct? Because I didn't see there is a congestion on the router or the bandwidth utilization is reach only 25%. As my understanding QoS only implement if there is a congestion coming from the router.

Thank you for your immediate response.

Best regards,

Ralph

[cadet alain]

Hi,

you're rigth, QoS congestion management only comes into play when there is congestion on the outbound link.

By default MPLS copies the Tos header from the original IP header into the MPLS experimental bits on the ingress PE router but once there if the Service provider has not negotiated an SLA with you then it may simply ignore those QoS values and treat all traffic equally.

Regards.

Alain

Don't forget to rate helpful posts.

[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

As my understanding QoS only implement if there is a congestion coming from the router.

Yes, that's correct.  One common solution is to shape traffic toward the destination on you outbound router.  Then you artificially create congestion on it which you can manage.

Unfortunately, if you're using a LAN type L3 switch, shaping might not be available.

[Ralph John Tampilic]

Hi All,

Thanks for your reply.

Follow-up questions: Is this correct? we must applied mls qos trust ip-precedence in all interfaces with switchport mode trunk? i only did was enable "mls qos" in every switch and "mls qos trust ip-precedence" in interface connected to the core switch and where the Polycom connected. Because sometimes there are no packets going to my qos config.

Best regards,

Ralph