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New Member

VoFR congestion dropped packets

The company I work for is currently running voice over frame and lately we have been having some quality issues not only with voice but data also. We have some consultants that are supposed to be managing these WAN lines but are doing a very poor job and have not figured out what is happening as of yet.

I dont know exactly what my routers are telling me but I am going to give you all some data from my main office router. I think the dropped packets are an indicating that there is indeed some sort of congestion on the line.

"show frame pvc 100" yields this info

PVC Statistics for interface Serial1/1:3 (Frame Relay DTE)

DLCI = 100, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/1:3.1

input pkts 46740452 output pkts 41096619 in bytes 2943720440

out bytes 2635388766 dropped pkts 51565 in FECN pkts 0

in BECN pkts 0 out FECN pkts 0 out BECN pkts 0

in DE pkts 0 out DE pkts 0

out bcast pkts 57336 out bcast bytes 4820024

pvc create time 14w0d, last time pvc status changed 06:27:36

Service type VoFR-cisco

Queueing strategy: weighted fair

Voice Queueing Stats: 0/0 (size/dropped)

Current fair queue configuration:

Discard Dynamic Reserved

threshold queue count queue count

64 16 0

Output queue size 1/max total 600/drops 2309

configured voice bandwidth 410000, used voice bandwidth 0

fragment type VoFR-cisco fragment size 160

cir 486000 bc 4860 be 0 limit 607 interval 10

mincir 486000 byte increment 607 BECN response no

frags 44486299 bytes 2772976275 frags delayed 44102671 bytes delayed 2761689

883

shaping active

traffic shaping drops 2309

Now I dont really know anything about WAN links, and VoFR. But I think dropped packets and traffic shaping drops are going to cause connection problems not only with Voice but data also.

I guess I am looking for some direction on what should be done. Does this command show that we are having some problems? Do I need to run anything else for you all to see before you can figure out what is wrong?

Thanks all,

LR

6 REPLIES
New Member

Re: VoFR congestion dropped packets

Hi,

Could you also send output from "show interface" command?

//Mikhail Galiulin

New Member

Re: VoFR congestion dropped packets

Here is a show int output for you. Please see the attached document.

LR

VIP Purple

Re: VoFR congestion dropped packets

Hello LR,

can you also post the configuration of the router ? That way, the traffic shaping configuration and parameters can be examined, in order to find possible reasons for your problem.

Regards,

GP

New Member

Re: VoFR congestion dropped packets

Here is the output from "show conf" please see the attached.

Re: VoFR congestion dropped packets

Hello,

first please set your bandwidth on the interfaces to the proper values. The command needs KILObps and not bps (f.e. use bandwidth 768 to specify 768 kbps).

Second I would have a look at your fragment sizes. The fragment size should determine how much a voice frame has to wait after a data frame at max, which is maximum jitter. The straight forward calculation is fragmentsize x 8 (as it is given in bytes) divided by bitrate on the line.

Using a standard value of 15 ms maximum jitter and 512000 bps line speed you get 960 Bytes. Setting much larger values increases jitter, which is bad for voice quality. Setting a much smaller value means more fragments and therefore more fragmentation headers. This results in less bandwidth for data and more overhead.

Did this help? Rate all posts please.

Martin

VIP Purple

Re: VoFR congestion dropped packets

Hello,

I am not sure if your map classes are configured right. The smallest shaping interval is 10ms, which for a CIR of 1544000, as in your ´serial´ map-class, would equal a BC of 15440, while you have only 1000 configured. I hope that makes sense to you. I would change the class maps, so that they look as following:

map-class frame-relay serial

frame-relay adaptive-shaping becn

frame-relay cir 1544000

--> frame-relay bc 15440

frame-relay be 0

frame-relay fair-queue

frame-relay voice bandwidth 1544000

frame-relay fragment 1600

!

map-class frame-relay 768sprint

no frame-relay adaptive-shaping

frame-relay cir 729000

--> frame-relay bc 7290

frame-relay be 0

frame-relay fair-queue

frame-relay voice bandwidth 576000

frame-relay fragment 480

!

map-class frame-relay 384

no frame-relay adaptive-shaping

frame-relay cir 365000

--> frame-relay bc 3650

frame-relay be 0

frame-relay mincir 365000

frame-relay fair-queue

frame-relay voice bandwidth 307000

frame-relay fragment 480

!

map-class frame-relay 512sprint

no frame-relay adaptive-shaping

frame-relay cir 486000

--> frame-relay bc 4860

frame-relay be 0

frame-relay mincir 486000

frame-relay fair-queue

frame-relay voice bandwidth 410000

frame-relay fragment 1600

!

map-class frame-relay 512

no frame-relay adaptive-shaping

frame-relay cir 486000

--> frame-relay bc 4860

frame-relay be 0

frame-relay mincir 486000

frame-relay fair-queue

frame-relay voice bandwidth 410000

frame-relay fragment 160

!

map-class frame-relay 128sprint

no frame-relay adaptive-shaping

frame-relay cir 121000

--> frame-relay bc 1210

frame-relay be 0

frame-relay mincir 121000

frame-relay fair-queue

frame-relay voice bandwidth 102000

frame-relay fragment 160

!

map-class frame-relay 384k

no frame-relay adaptive-shaping

frame-relay cir 365000

--> frame-relay bc 3650

frame-relay be 0

frame-relay mincir 365000

frame-relay fair-queue

frame-relay voice bandwidth 307000

frame-relay fragment 160

!

map-class frame-relay 512test

no frame-relay adaptive-shaping

frame-relay cir 512000

frame-relay bc 5120

frame-relay be 0

frame-relay mincir 512000

frame-relay fair-queue

frame-relay voice bandwidth 360000

frame-relay fragment 640

!

map-class frame-relay 384sprint

no frame-relay adaptive-shaping

frame-relay cir 365000

--> frame-relay bc 3650

frame-relay be 0

frame-relay mincir 365000

frame-relay fair-queue

frame-relay voice bandwidth 307000

frame-relay fragment 1600

Can you try this and see if that makes a difference ?

Regards,

GP

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