From: Johnny Dedon (johnny.dedon@xxxxxxxxxx)
Date: Tue May 08 2001 - 12:52:26 GMT-3
Thanks Wayne,
You said exactly what I was trying to say after a long day.
Johnny Dedon
Senior Staff Consultant
Exodus Professional Services
johnny.dedon@exodus.net
www.exodus.net
----- Original Message -----
From: "Wayne Gustavus" <wgustavus@mentortech.com>
To: "'Mohamed Heeba'" <MAHeeba@itqan.co.ae>; <lkouncar@UU.NET>;
<ccielab@groupstudy.com>
Sent: Tuesday, May 08, 2001 10:49 AM
Subject: RE: Fatkid 505 ,dail backup question
> I believe the proper way to interpret the syntax of the command is more
> basic than what you described. The percentages that are used in the
backup
> load command are definitely in relation to the available bandwidth of the
> primary interface. The description of the disable-load threshold is
trying
> to convey the idea that the *total* traffic must be less than the value
> derived from the disable-load threshold before *all* traffic will be moved
> back to the primary link and the backup link is shut down.
>
> For example, suppose you have a primary link with a bandwidth of 100Kbps
> defined and the command "backup load 20 10". (I know the numbers may be
> unrealistic but it makes the math easy and is easy to test)
> If there is 50Kbps of traffic on the primary interface then there is a 50%
> load and the secondary link will be activated. If the router balances the
> traffic across the 2 links (don't forget about ip route-cache) then 25Kbps
> will travel across both the primary and secondary.
>
> Now suppose the traffic source(s) slows down and there is 18Kbps traffic
> presented to the network. This will result in approx 9Kbps on the primary
> and secondary. However, since the total traffic rate is still 18kbps, the
> 10% kick-out (or 10Kbps, since it is 10% of the primary's 100Kbps
bandwidth)
> the secondary stays active.
>
> Finally, if the traffic source(s) slows its rate to 8Kbps, the primary and
> secondary will each carry approximately 4Kbps of traffic. Since the
*total*
> traffic rate is below the 10% kick-out rate, the secondary link will
revert
> to 'normal operation' and go into standby mode. The primary link will
then
> carry the entire 8Kbps.
>
> The BOTTOM LINE is to think of the disable-load value as the traffic rate
> which the primary link 'decides' it doesn't need the help of the secondary
> any more. This rate is calculated as a percentage of the primary link's
> bandwidth. Therefore, the bandwidth of the secondary link does not factor
> into the equation at all (BTW, even though it isn't relevant to this
issue,
> you may want to double check the BW of the BRI interface with a "sh int
> bri0"; I think you will find it is 64Kb even though you effectively have
> 128Kb with the 2 B-channels)
>
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