Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

QoS - can u trust dscp and cos?

Hello,

is it possible to trust DSCP and COS at the same time?

If so, which one wins?

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

Re: QoS - can u trust dscp and cos?

G'day,

It does not really make sense to trust both DSCP and CoS at the same time. You configure your switch to trust one or none of these.

As an example, if you did have the capability to trust both DSCP and CoS, imagine what would happen if you received a frame with DSCP EF and CoS 0 ? You would be faced with a conflicting situation ... if you trusted CoS, you would give a potentially high-priority packet lesser service. Whereas if you trusted DSCP, you could end up giving a potentially low-priority packet voice-like service... So the option of trusting both is not allowed.

Hope that helps - pls rate the post if it does.

Paresh

2 REPLIES
Purple

Re: QoS - can u trust dscp and cos?

G'day,

It does not really make sense to trust both DSCP and CoS at the same time. You configure your switch to trust one or none of these.

As an example, if you did have the capability to trust both DSCP and CoS, imagine what would happen if you received a frame with DSCP EF and CoS 0 ? You would be faced with a conflicting situation ... if you trusted CoS, you would give a potentially high-priority packet lesser service. Whereas if you trusted DSCP, you could end up giving a potentially low-priority packet voice-like service... So the option of trusting both is not allowed.

Hope that helps - pls rate the post if it does.

Paresh

New Member

Re: QoS - can u trust dscp and cos?

hello,

yes, I wondered about the conflict situation, but the documentation I had read didn't spell out that you couldn't do it.

Thanks again.....Will rate!

120
Views
5
Helpful
2
Replies
CreatePlease login to create content