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Is Low MTU (ie 320) for VoIP over Frame-relay can be used to avoid serialization delay for large data packets?

In order to provide voice quality for VoIP, is FR fragmentation equivalent to lowering the MTU size for the serial subinterface of a Frame relay subinterface?

Is there any isues like stop communications, using Low MTU ?

1 REPLY
Anonymous
N/A

Re: Is Low MTU (ie 320) for VoIP over Frame-relay can be used to

If the router belongs to any of the

platform listed below, then use

FRF12 for you fragmentation. The MTU size

lowering also works but this can cause a high over

head as it can't be specified on a per dlci level.

With multiple dlci i.e. subinterfaces use per dlci fragmentation.. this helps reduce the overhead of changing the MTU size of the physical interface.

Snip config example.( __Must be configured on both side of the termination___)

PHONE 3333312---ROUTERA ----DLCI 100----ROUTERB ---PHONE 2111123

ROUTER A

!

dial-peer voice 1 voip

destination-pettern 2T

session target ipv4:10.10.10.2

!

int ser 0/0

encap frame-relay

frame-relay traffic-shaping

no ip address

!

interface serial0/0.1 point-to-point

ip add 10.10.10.1 255.255.255.252

frame-relay interface-dlci 100

class voice

!

map-class frame-relay voice

frame cir 64000

frame bc 640

frame mincir 64000

frame-relay ip rtp priority 16384 16383 48

frame fragment 80

frame fair-queue 64 256 0

ROUTER B

!

dial-peer voice 3 voip

destination-pettern 3T

session target ipv4:10.10.10.1

!

int ser 0/0

encap frame-relay

frame-relay traffic-shaping

no ip address

!

interface serial0/0.1 point-to-point

ip add 10.10.10.2 255.255.255.252

frame-relay interface-dlci 100

class voice

!

map-class frame-relay voice

frame cir 64000

frame bc 640

frame mincir 64000

frame-relay ip rtp priority 16384 16383 48

frame fragment 80

frame fair-queue 64 256 0

This should help if your router is

c2600, c3600, mc3810, c7200, c1750

all running the right level of IOS.

12.1(5)T and above should work well.

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