QOS using DSCP

Are you suffering congestion on your LAN? Until there is congestion, you are simply just marking the traffic. If there is congestion on your LAN, I would remedy that before going the QOS route.

@Jordan

thanks for the reply. Right now i can mark the traffic from the audio code gateways but the IP telephony server we have is not able to mark the traffic for DSCP ( I confirm this by using wireshark trace).

so to give the SIP and RTP traffic priority should i use the same commands/logic that you mentioned in your first post ? is there any thing else that i need to look into ?

Yes, you would use the commands that I posted. This would classify and mark the traffic so that regardless of what the telephony server or devices set, you have consistent marking of the traffic for higher prioritization.

@jordan

Thanks jordan ... How can i debug the packets that are being matched on the switch and forward to the priority queue ?

and one more question how would i add access-list for all other traffic in the acl list ?

Not sure what you mean. There would be no reason to add any other traffic to the ACL. Any and all traffic added to the ACL would then receive the same priority markings.

So when i am applying service policy to the interface it only allows sip and rtp traffic and all other traffic like http etc is denied.

Also correct me if i am wrong in this. If i apply

policy-map VOIP-MAP
 class VOIP-CLASS
   set dscp ef

that's means all the packets with sip and rtp assigned the value with expedite forwarding (DSCP value 46) , means overwrite the DSCP value in the packet from 0 to 46 ?

That looks correct. Yes ,any traffic mathing the VOIP-CLASS acl will be remarked EF.
All other traffic will not be affected by the service policy.

Hi i have these commands in my running configuration because before i applied the auto qos on the switch.
mls qos srr-queue input threshold 1 80 90
mls qos srr-queue input priority-queue 2 bandwidth 30
mls qos srr-queue input cos-map queue 1 threshold 2 3
mls qos srr-queue input cos-map queue 1 threshold 3 6 7
mls qos srr-queue input cos-map queue 2 threshold 1 4
mls qos srr-queue input dscp-map queue 1 threshold 2 24
mls qos srr-queue input dscp-map queue 1 threshold 3 48 49 50 51 52 53 54 55
mls qos srr-queue input dscp-map queue 1 threshold 3 56 57 58 59 60 61 62 63
mls qos srr-queue input dscp-map queue 2 threshold 3 32 33 40 41 42 43 44 45
mls qos srr-queue input dscp-map queue 2 threshold 3 46 47
mls qos srr-queue output cos-map queue 1 threshold 3 4 5
mls qos srr-queue output cos-map queue 2 threshold 1 2
mls qos srr-queue output cos-map queue 2 threshold 2 3
mls qos srr-queue output cos-map queue 2 threshold 3 6 7
mls qos srr-queue output cos-map queue 3 threshold 3 0
mls qos srr-queue output cos-map queue 4 threshold 3 1
mls qos srr-queue output dscp-map queue 1 threshold 3 32 33 40 41 42 43 44 45
mls qos srr-queue output dscp-map queue 1 threshold 3 46 47
mls qos srr-queue output dscp-map queue 2 threshold 1 16 17 18 19 20 21 22 23
mls qos srr-queue output dscp-map queue 2 threshold 1 26 27 28 29 30 31 34 35
mls qos srr-queue output dscp-map queue 2 threshold 1 36 37 38 39
mls qos srr-queue output dscp-map queue 2 threshold 2 24
mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55
mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63
mls qos srr-queue output dscp-map queue 3 threshold 3 0 1 2 3 4 5 6 7
mls qos srr-queue output dscp-map queue 4 threshold 1 8 9 11 13 15
mls qos srr-queue output dscp-map queue 4 threshold 2 10 12 14
no mls qos rewrite ip dscp
 

will that be any effect ?

Also on the cisco SG300 switch on the policy binding page it says
"
Policy Binding
A port can be bound with either a policy or an ACL, but not both. The default action is to discard (Deny Any) all the packets that do not meet the rules in a policy.
You can override the default action of a policy to forward those packets by configuring Permit Any on the desired ports."