[c-nsp] multipath BGP not balancing equally.

[Dean Smith]

Would agree that volume is rare between 2xIP addresses but we have something 
similair although on not quite the scale.

We NAT a very large organisation to the Internet. They have a large number 
of disparate sites that all do their own AV updates. All the PCs download at 
the same time in the evening and we generate about .75 Gb/s of traffic 
between our external PAT address and the AV download site for a good couple 
of hours. If we had a bigger internet pipe it would be a higher figure. (for 
less time of course).

Dean
----- Original Message ----- 
From: "Rodney Dunn" <rodunn at cisco.com>
To: "Mikael Abrahamsson" <swmike at swm.pp.se>
Cc: "Cisco" <cisco-nsp at puck.nether.net>
Sent: Wednesday, August 05, 2009 2:19 PM
Subject: Re: [c-nsp] multipath BGP not balancing equally.


> For small flow combinations you are right. btw, it would be just L3 
> src/dst flows by default unless the L4 port option is enabled.
>
> I thought about there being a single flow causing the difference that 
> would be hashing down one of the paths. But 2G, while not impossible, 
> typically isn't used between two ip addresses. It's something to check 
> though for sure.
>
> Rodney
>
>
>
> Mikael Abrahamsson wrote:
>> On Tue, 4 Aug 2009, Rodney Dunn wrote:
>>
>>> That's usually caused by routes not being the same on the paths.
>>
>> It was my understanding that this usually was caused by not having enough 
>> L4 flows to loadshare on...? Ie if you have 100 TCP flows and 4 paths, 
>> then it's not enough flows to get good load share on, but if you instead 
>> have 10k flows and all of them are low-speed, then the odds of them being 
>> equally load shared is much better?
>>
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