VoIP Frame Relay

We have major voice quality problems with your new Mitel VoIP system across the WAN I have had our WAN provider and Cisco check our configs and they say everything looks good. We are experiencing high amounts of jitter and low amounts of packet lose, jitter is ranging between 60ms - 140ms. We have frame relay with Voice and Data going over the same PVC, I recently read that Cisco recommends put Voice and Data on separate PVCs.

Cisco website states the following

formatting link
A good solution employed by some customers is to use separate PVCs for data and voice. This solution enables the customer to transmit up to port speeds in the data only PVC while maintaining a load at or below CIR on the voice PVC. Some frame providers may not find the solution appropriate depending on the frame switch and its queuing structure. If possible, have the Frame Relay provider prioritize the voice PVC over the data one so that there is not any queuing delay because of the data packets.

We currently have our CIR set at 768 and our WAN provider just told us our true CIR is 128 see config below.

This is our current config and we have the CIR set to 768.

interface Serial0/0.100 point-to-point bandwidth 768 ip address frame-relay interface-dlci 100 IETF class VoIP

map-class frame-relay VoIP frame-relay fragment 1600 frame-relay cir 768000 frame-relay bc 300 frame-relay be 0 frame-relay mincir 768000 service-policy output Wan-Policy-768-Frame logging trap debugging access-list 100 permit gre host host

How would I configure separate Voice and Data PVC to allow bursting to 768 yet giving the Voice traffic a guaranteed 128 of bandwidth? Would I setup another sub interface for data with another PVC and then set the frame-relay cir to 0 on the data PVC and set the CIR to 128 on the Voice PVC?

Do you think not having our routers currently configured this way is the source of the voice quality problems please give me your thoughts?

Thank You,


Reply to
Chris T.
Loading thread data ...

Hi Chris,

You may wish to investigate the Mitel User Group:

formatting link

Brad Reese BradReese.Com=AE Cisco Resource Center Toll Free: 877-549-2680 International: 828-277-7272=20 Website:

formatting link

Reply to

You need to post the full configs on this router and the one at the other end of the link. It would be nice to see what QoS policies are in place, and if you have traffic-shaping configured.

If you have configured CIR as 768, and the provider is only giving you 128, that is probably the source of your packet-loss and jitter problems. You need to have the vendor bump up the CIR to 768 (or configure the router with the same value the vendor is proving). Depending on your FR vendor, they will handle traffic above your CIR in different ways. Most will throttle the traffic above the CIR to a specified value, which would result in the large jitter you are seeing. Also, what is at the other end of the link? Is that router interface oversubscribed? what is the CIR configured on the PVC's? How many PVC's are configured? etc. etc.

Running VoIP over frame-relay takes a lot of consideration and proper configuration to work well.

Running a separate PVC's for voice and data, you would use policy-map to route the voice over the VoIP PVC and the data over the data PVC. This is the recommended practice, along with running QoS and traffic-shaping.


formatting link
Note: A good solution employed by some customers is to use separate PVCs

Reply to

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.