From: chrlewis@cisco.com
Date: Sat Sep 17 2005 - 20:16:24 GMT-3
The answer depends on what delay you will accept on that interface
before a voice packet can be transmitted.
The higher the speed on the interface (which is what I always use to
calculate how fast the packet is clocked on to the wire, rather than the
DLCI speed) and the smaller the fragment size, the lower the delay any
PQ packet has to wait before it can be transmitted if a non-PQ fragment
has been sent to the interface Tx-ring ahead of it.
The fragment value is in bytes, so I do it by dividing the access rate
by 8, so if there is a 256K access rate for example, this equates to
32000 bytes per second.
If I only want to allow 10 milliseconds delay for queueing in my design,
I'd set fragment to 320. There are no right answers, just how much of
your delay budget you can llocate to queueing delays at that point in
the network.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Quetta Walla
Sent: Saturday, September 17, 2005 3:12 PM
To: ccielab@groupstudy.com
Subject: Frame relay fragement and llq
Please explain:
class-map VoIP
match access group x
!
policy-map llq
class VoIP
priority percent 40
!
interface s0
encap frame
frame traffic-shaping
frame interface-dlci 201
class FRAG
!
map-class frame-relay FRAG
frame-relay fragment 100
frame-relay fair-queue
frame-relay cir 64000
service-policy output llq
!
This is fragment type end-to-end if you check under show frame pvc 201
which indicates that pure FRF.12 fragmentation type (for VoIP) is
carried on this dlci.
Other 2 options are for VoFR are vofr cisco (Cisco proprietary) and vofr
FRF.11 Annex C header. In case of vofr cisco, it can be mentioned under
frame-relay interface-dlci XX.
My question is how do we choose the proper fragment size for either
case?
--
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