Re: Trunking (was: Gigabit Linux Server Bottlenecks)

From: Thomas Davis (tadavis@lbl.gov)
Date: Thu Feb 10 2000 - 14:21:04 EST


Anton Ivanov wrote:
> Basically it boils down to the following:
>
> If connected to a network with more than one interface NT (at least under some
> conditions) does round robin on the Ethers for emitting packets. The Actual IP
> address of the interfaces does not matter. As a result you can get a pretty full
> concatenated pipe if your traffic is:
> A) disbalanced like web or lots of clients pulling stuff off a file server
> B) server is being hit randomly due to DNS round/robin or other load balancing
> technique.
>
> Note on this one: If you have a look at instructions on using concatenated
> Ethers on NT you will see that "all trunking functions must be turned off".
>
> In order to get the same result with linux you have to use the following setup:
> 1. The service (web, whatever) hanging off a loopback alias on the linux host.
> 2. A switch with multipath routing capabilities having a route per each Ether
> to the linux host.
> 3. The linux host having multipath enabled (2.2+) and multipath routes back.
>

In v2.2.15pre5, (and newer), there's a device called 'Ethernet
Bonding'. It does the above, and allows one to bond together mulitple
(up to 4) devices into one virtual device.

The only problem with this, is most switches still limit your
performance through this bonded device. It can however, give you a
'fatter' pipe, not a 'faster' pipe.

-- 
------------------------+--------------------------------------------------
Thomas Davis		| PDSF Project Leader
tadavis@lbl.gov		| 
(510) 486-4524		| "Only a petabyte of data this year?"

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