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RE: config - ISDN B-Channel 2 links - up ---> Doubt posted 08/16/2005
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At a very simple viewpoint, it's Layer 2 versus Layer 3.

If you JUST use dialer load-threshold (and no ppp multilink) you will get
two identical 64K paths that your router/IGP see.  You'll do Layer 3 load
balancing at that point.

If you use dialer load-threshold WITH ppp multilink you will get the Layer 2
splitting as you have noted, which gets seen by your router/IGP as a single
128K interface.

Links minimum (or variants thereof) will determine how many links must be
active BEFORE a ppp multilink bundle is considered to be a success.  (e.g.
you require 3 but only get 2, then the world is not good)

"ppp multilink load-threshold" will do the same thing that dialer
load-threshold does, but it requires that ppp multilink be negotiated first.
So you'll never get L3 load balancing no matter what your config on that



-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Sent: Tuesday, August 16, 2005 4:17 PM
To: Arun Arumuganainar
Cc: ccielab@xxxxxxxxxxxxxx; nobody@xxxxxxxxxxxxxx
Subject: Fw: config - ISDN B-Channel 2 links - up ---> Doubt


I just remember that Solies talks about this subject. Her books has an
example using both, ppp multilink and dialer load-threshold at the same

ppp multilink
dialer load-threshold ...

I have heard that 'ppp multilink link minimum...' works better. But on
tests, both have their problems, specially when config are changed,
sometimes requiring a reload on the router. (that just happened today when I
was testing to check this threat...after removing 'dialer load-threshold'
and configuring 'ppp multilink' and 'ppp multilink minimum...' the ISDN stop
working, just displaying that there was no free channel to dial) 

I am not sure yet what happens if just configuring 'dialer load-threshold' 
concerned to the distribution of packets along the two channels.

With ppp multilink it is clear that IOS fragments packets, split them over
the two channels, and the remote router reassembles them. 
But how packet are sent across the two channels when using only dialer

Any feedback appreciated.


----- Forwarded by Alaerte Gladston Vidali/Brazil/IBM on 16/08/2005 17:08

Alaerte Gladston Vidali/Brazil/IBM
16/08/2005 17:03

"Arun Arumuganainar" <aarumuga@xxxxxxxxxxx> cc ccielab@xxxxxxxxxxxxxx,
nobody@xxxxxxxxxxxxxx Subject
Re: Re: config - ISDN B-Channel 2 links - up ---> Doubt

Hi Arun,

Sorry, I made a mistake. When using 'dialer idle-threshold.." there is two
channel, not two entries on the routing table.

If I am not mistaken, Multilink PPP load balance using both channels, while
BOD does not get load balancing. The second channel is used only when the
first is 'full'.

I hope we get more feeback on this.

Bandwidth on demand (BOD) is a Cisco proprietary implementation that allows
the aggregation of multiple B channels into a single logical connection.
This implementation is widely used in Cisco-centric networks

The implementation of Cisco's BOD solution is accomplished through the
dialer load- threshold command

Multilink PPP is a specification that enables the bandwidth aggregation of
multiple B channels into one logical pipe. Its mission is comparable to that
of Cisco's BOD. 
More specifically, the
Multilink PPP feature provides load-balancing functionality over multiple
wide area network
(WAN) links, while providing multivendor interoperability, packet
fragmentation and proper sequencing, and load calculation on both inbound
and outbound traffic Cisco's implementation of Multilink PPP supports the
fragmentation and packet sequencing specifications in RFC 1717. Multilink
PPP enables packets to be fragmented and the fragments to be sent (at the
same time) over multiple point-to-point links to the same remote addres

This discussion says:

quoted from

int bri0
        dialer load-threshold 10


int bri0
        ppp multilink
        ppp multilink load-threshold 10

Both will add a second channel when the load reaches 10/255, however in the
first case you don't really have a ppp multlink, only two seperate channels.


"Arun Arumuganainar" <aarumuga@xxxxxxxxxxx> Sent by: nobody@xxxxxxxxxxxxxx
13/08/2005 01:49
Please respond to
"Arun Arumuganainar" <aarumuga@xxxxxxxxxxx>

Alaerte Gladston Vidali/Brazil/IBM@xxxxx, <ccielab@xxxxxxxxxxxxxx>

Re: Re: config - ISDN B-Channel 2 links - up ---> Doubt

Hmmm ... I am not an Expert on ISDN . But this is what my understanding 

There are two ways of configuring Bandwidth aggrigation  1) PPP Multilink
and 2) BOD . Functionality wise both are exactly the same .

Two Channels to same destination
1 Route in the routing table .

But the difference between them is that PPP multilink is standard fromat
while BOD is cisco properitary !!!

Note : BOD is used when both the ends are CISCO !!! If you are dialing in 
non cisco devices PPP multilink is the only option

Thanks and Regards
----- Original Message -----
From: <gladston@xxxxxxxxxx>
To: <ccielab@xxxxxxxxxxxxxx>
Sent: Friday, August 12, 2005 11:46 PM
Subject: Re: Re: config - ISDN B-Channel 2 links - up ---> Doubt

> Arun,
> Would you agree with Shanky?
> I am not sure if you stating a different point.
> Configuring 'dialer load-threshold..' without 'ppp multilink':
> -- two channels to the same destination
> -- two entries on the routing table
> On the other hand, configuring 'dialer load-threshold..' with 'ppp
> -- two channels to the same destination
> -- one entry on the routing table
> Could you think about an example when 'dialer load-threshold' without 
multilink would be used?
> _______________________________________________________________________
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