how to guaranty bdwidth on 3750

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Sep 5th, 2008
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hi all ,

is it possible to guarantee a min bandwidth for some flows on 3750 if there is no congestion on the link ?

i mean , my customer is rate limited to 40MB by provider (for all traffic),the 3750 uplink to provider is a giga port

he would like to guarantee min 10 mb (not max)to a network and min 5 mb (not max)to another ( on output direction) uplink port.

At max there will be 40MB and no congestion on uplink port,in such case does cmde srr-queue bandwidth share a b c d apply ?

2nd ) do a b c d are percent of bandwidth cmde under interf or speed link ?

if i use the following conf

int gi x/y

speed 100 (limit speed link to 100M)

bandwidth 40000

srr-queue bandwidth limit 40 (40Mb max)

srr-queue bandwidth share 2 1 2 5

will i have 8MB queue 1 and 4Mb q2 guaranty but not limited to ?

thanks for help

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simontibbitts Fri, 09/05/2008 - 09:22
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Yes, that makes sense. The command 'srr-queue bandwidth limit' will actually limit your port to 40% tho, hope that's what you want?

The 'srr-queue bandwidth share' command will guarantee that bandwidth but not limit it to it. (the command 'srr-queue bandwidth shape' is the one that does that)


Joseph W. Doherty Fri, 09/05/2008 - 16:41
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If the port is running at gig, then you'll need to limit to 4%; 40% for running at 100 Mbps. (I also recall, the 3750 limits are not precise, you may need to first experiment to find what % values allows the fastest rate without exceeding your 40 Mbps.)

I haven't worked the number for your share command, but depending on number of queues, you'll need to insure queue ratios provide for the 5 and 10 Mbps you want to reserve.


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