[LARTC] bandwidth aggregation between 2 hosts in the same subnet

[Grant Taylor]

On 07/30/07 09:10, Ralf Gross wrote:
> I'm trying to increase the bandwidth between two hosts (backup). Both 
> hosts are in the same /24 subnet and each of them is connected to a 
> Cisco switch by 2 GbE interfaces (intel e1000). The switches/host are 
> located in different building which are connected by 3 x GbE.

Ok, this is simple enough.

> My goal is to increase the bandwidth for a single tcp session between 
> the two hosts for a backup job (per packet round robin?), not for 
> multiple connections between many hosts. I know that I won't get 2 x 
> 115Mb/s because of packet reordering, but 20-30% more that a single 
> connection would be ok.

*nod*

> Any ideas what I'm missing, or if it's possible at all?

You are barking up the wrong tree, or at least the wrong layer.  If you 
have any control of the switches in each building, or can have someone 
make changes to them for you.  Bond the two connections together to make 
one logical larger connection.  Cisco calls this "EtherChannel" and 
Linux calls this "Bonding".

In the long run you will end up with two raw ethernet devices enslaved 
in to one bond0 interface.  These two bonded / etherchannel interfaces 
will have very close to 2 Gbps worth of speed.

Do this on the lower OSI Layer 2 rather than trying (and failing) to do 
it on the higher OSI Layer 3 where you are doing it presently.



Grant. . . .