From: West, Jeff (westj@telecomsys.com)
Date: Sun Mar 09 2003 - 18:19:01 GMT-3
A multilink is like a dialer interface in the fact that the commands
are not on the physical interface, but rather are on the virtual
interface. In reference to what do the fragmenting and interleaving
commands do that you highlighted, they are for LFI (link fragmentation
and interleaving). This fragments large packets and mixes in smaller
VoIP packet to give you better voice quality. If you have a 64k link
(or any link under 768 for that matter) a large data packet will take
a certain time to get out the interface (serialization delay). If I
remember the math it is something like for every 64k of your link, it
will take 10ms to send out 60bytes (i.e. 128k link, 120 bytes would
take 20ms). So what you are telling the router is to break up data
packets into 10ms chunks to allow data to fit between them without
having to wait for the whole data packet to go out the interface. It
makes a huge difference when you have a small pipe and are running
VoIP and data at the same time.
Jeff West
TeleCommunication Systems, Inc.
(813) 831-6353 x118
-----Original Message-----
From: Hunt Lee [mailto:ciscoforme3@yahoo.com.au]
Sent: Sunday, March 09, 2003 8:19 AM
To: ccielab@groupstudy.com
Subject: Multilink interface mystery
Hi Group,
I saw the following config from a VoIP config...
RTA --- RTB
PPP
64kbps
Does anyone know what does a Multilink interface do? I have used ppp
multilink & dialer-load threshold under BRI interface to combined 2 x
64k to a faster ISDN link before, but I have no idea what this
Multilink interface do...
interface Multilink1
ip unnumbered Ethernet1/0
no ip directed-broadcast
ip tcp header-compression iphc-format
no ip mroute-cache
fair-queue 64 16 0
no cdp enable
ppp multilink
ppp multilink fragment-delay 10 <---- Also, what does this do?
ppp multilink interleave <---- & this?
multilink-group 1
ip rtp header-compression iphc-format
ip rtp priority 16384 16383 48
!
interface Ethernet1/0
ip address 172.16.110.1 255.255.255.0
no ip directed-broadcast
!
interface Serial1/0
bandwidth 64
no ip address
no ip directed-broadcast
encapsulation ppp
no ip mroute-cache
no fair-queue
clockrate 64000
ppp multilink
multilink-group 1
Any help / ideas would be greatly appreciated.
Regards,
Hunt
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