[j-nsp] Auto bandwidth LSPs

Sailendra Mahanty sail at juniper.net
Tue Feb 1 08:25:14 EST 2005

Hi Jerome,

We have two variables, avg_bw_usage and max_avg_bw_usage.
At every 'x sec' interval, we calculate avg_bw_usage for every lsp since 
the last computation (before x secs).
We maintain max_avg_bw_usage for every lsp which is the highest ever 
recorded avg_bw_usage for this lsp. After every 'x secs' avg_bw_usage is 
reset to zero.
This x value is configured globally for all lsps. This 'x sec' is same 
as the mpls stat interval with a default of 300 secs. You can check this 
with help of log which look like :

"Nov 29 08:29:09 2004 UTC Total 1 sessions: 1 success, 0 fail, 0 ignored
lsp-test 230111628 pkt 14727144192 Byte 0 pps 0 Bps Util 0.00% "

The above calculated max_avg_bw_lsp for each lsp is used to adjust the 
lsp BW at a particular interval (configurable per lsp) with a default 
value of 24 Hrs you have referred to.  This we call 'adjust interval' 
and is configurable per lsp. We also show the time remaining for adjust 
interval as shown below.

"Max AvgBW util: 0bps, Bandwidth Adjustment in 26 second(s)"

If the max_avg_bw_lsp for a lsp is different from the existing BW of 
lsp, then we try to adjust the lsp BW. If successful earlier bw is 
released and the value of max_avg_bw_lsp is reset to zero. This is only 
maintained for active lsp since traffic flows through active lsp.

In your output

AdjustTimer: 86400 secs <<< 24 Hours >>>
Max AvgBW util: 73.294Mbps, Bandwidth Adjustment in 52423 second(s). <<< 
52423 second remaining for next adjustment >>>


Jerome Fleury wrote:

> Hi,
> I was wondering how the Auto bandwidth feature on Juniper routers does
> calculate the Max AvgBW (see below). I find the documentation not really
> clear about it.
> Is this an instantaneous value checked at the end of the adjust-interval
> timer ? Or is it some Max value recorded during the adjust-interval 
> period
> of time (which by default is one day).
> How does it interact with the statistics file ?
> Thanks to anyone who could help me on that.
>  From:, State: Up, ActiveRoute: 3, LSPname: BB1.GRE-BB1.STR
>  ActivePath:  (primary)
>  LoadBalance: Random
>  Autobandwidth
>  AdjustTimer: 86400 secs
>  Max AvgBW util: 73.294Mbps, Bandwidth Adjustment in 52423 second(s).
> Jerome.
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> http://puck.nether.net/mailman/listinfo/juniper-nsp

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