Qos Design Recommendation

Unanswered Question
May 8th, 2009

Hi Guys,

I have a two remote sites each running call manager express with one site having only a 4MG ADSL connection to the internet therefore leaving only 512k for upstream traffic. There is also a vpn tunnel between the two sites.

Users are experiencing qos issues when making intersite calls jitter packet drops etc.

At the moment there is no qos deployed so i have come up with the following recommendation to prioritize the voice traffic.

class-map match-all Voice

match ip dscp ef

class-map match-any Call_Signalling

match ip dscp cs3

match ip dscp af31

policy-map WAN-EDGE

class Voice

priority percent 20

class Call_Signalling

bandwidth percent 5

class class-default



interface fastethernet 0/1

service-policy output WAN-EDGE

I would like to know if there is any other mechanism i can use and if the above recommendation will be sufficient to resolve the qos issues on this link...thanks.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Joseph W. Doherty Fri, 05/08/2009 - 03:24

For QoS to be effective, it needs to match available bandwidth. In this case, you'll want a hierarchical policy with a shaper for the 512 Kbps.


policy-map shape512

class class-default

!shape slower than nomimal bandwidth to allow for Ethernet overhead

shape avg 450000

service-policy WAN-EDGE

interface fastethernet 0/1

service-policy output shape512

As the other poster (John) noted, if you're using VPN, you could use the QoS preclassify command. Since you're using DSCP tags for matching, you voice traffic would be recognized, but class-default would only see one flow w/o preclassify for all your VPN traffic.

I recommend against using FQ with non-LLQ defined classes. I would suggest you either place the call signaling traffic into the LLQ or just let FQ handle it.


This Discussion