05-09-2007 08:50 AM
I currently have a TAC case open, and may have stumped the technician. My company is using radio communications at a central dispatch offic to communicate with rolling trucks. Some trucks are beyond the RF range, so an application is converting the radio transmissions into UDP to be relayed across a carrier MPLS WAN to other Antenna locations that are in RF range of these trucks. Multiple problems here. First, the application uses multicast, which is not supported on the MPLS network, resulting in the need for GRE. This is working. The second problem is trying to provice LLC QoS for these transmissions. The application requires 50k for the radio communications, and must be treated like voice. I have configured QoS but when applied it is degrading the quality of the communications to the point where it is totally unusable. When the service-policy is removed, the quality improves. My current QoS configs are as follows:
class-map match-all DINET_RADIO
match access-group name DINET
!
!
policy-map OUTBOUND_POLICY
class DINET_RADIO
set dscp ef
priority 51
class class-default
fair-queue
interface Serial0/1/0
service-policy out OUTBOUND_POLICY
interface Serial0/1/0.777 point-to-point
frame-relay interface-dlci 777 IETF
ip access-list extended DINET
permit ip host 10.191.33.119 host 10.191.32.242
I have looked at FRF, but don't know if it can be used on MPLS links. Any help in understanding why the QoS configs are making the communications worse, and how to fix it would be greatly appreciated.
05-09-2007 11:00 AM
Hi,
I quess that your application requires more than you have reserved.
I would rather use the priority percent cmd.
The 75 percent rule of thumb is actually ok.
(i.e. the sum of the bandwidth percentage allocated to the high priority traffic and the bandwidth percentage allocated to the non-priority traffic cannot exceed 75 percent of the total bandwidth available on the interface. )
Keep in mind that GRE generates overhead.
HTH
Regards,
Bjornarsb
05-09-2007 11:43 AM
Actually, I have measured the amount of bandwidth used when communications is going through, and it is less than 50k. However I did at one point configure priority 102k, which made no difference. Exactly how much overhead does GRE add?
05-10-2007 03:53 AM
Hi,
Gre adds 24 byte overhead to each packet.
So it depens on your packet size.
On the other side, how much bandwith do you have available on your link?
BR,
Bjornarsb
05-10-2007 07:21 AM
The circuit is a full T1, with enterprise PVC CIR at full T1. The circuit normally runs less than 30% utilization.
Would configuring frame-relay traffic shaping to get the dual FIFO help?
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