Re: bandwidth aggregation between 2 hosts in the same subnet

Linux Advanced Routing and Traffic Control

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Paul Zirnik schrieb:
> > > On Monday 30 July 2007 16:10, Ralf Gross wrote:
> > > > 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.
> > > >
> > > > I followed different HowTOs
> > > >
> > > > http://www.lartc.org/howto/lartc.rpdb.multiple-links.html#AEN298
> > > > http://lartc.org/howto/lartc.loadshare.html
> > > > or something like: ip route...equalize via...
> > > >
> > > > but I never got a higher transfer rate  between the two hosts than
> > > > max 115Mb/s with benchmarks like netpipe or netio.
> > >
> > > If you have different switches for each line i suggest the use
> > > of "bonding" in balance-round-robin mode.
> > >
> > > +-------+  eth0  +--------+  eth0  +------+
> > >
> > > | Host  |--------|switch 1|--------| Host |
> > > |
> > > |       |        +--------+        |      |
> > > |
> > > |  A    |  eth1  +--------+  eth1  |   B  |
> > > |
> > > |       |--------|switch 2|--------|      |
> > >
> > > +-------+        +--------+        +------+
> >
> > I tried this setup a while ago. Both hosts were connected to a Cisco
> > switch. On the linux hosts I created bond0 interfaces (round robin)
> > and the switch ports on both switches were configured as Port
> > Channels.
[...]
> > This didn't increase the transfer rate for a tcp session between the
> > two hosts. Because the mac and ip addresses are the same for the whole
> > tcp session (backup).
> 
> This is why i sayed you need two different switches. With only one
> the switch will allways send only to one port, because he knows the
> MAC address and will not balance traffic on two or more ports with
> the same MAC address as destination. Etherchannel has no balancing
> algo it is desinged for one to many connections not for 1 to 1. With
> two switches this is not true and the traffic will utilize both
> lines even for a 1 on 1 connection.

I'm still a bit confused.  If I use balance-rr without Etherchannels
the bond0 MAC address will show up on 2 different switches. AFAIK and
what the networking staff told me, that will result in problems.

In your graph both hosts are connected by two switches and both hosts are
directly connected to each of the switches. In my case there are more switches
innvolved because the hosts are not in the same building.

That's the setup at the moment.

         building A                                building b
+--------+        +----------+           +----------+       +--------+
|        |eth2  p1|cisco 6509| 3 x GbE   |cisco 6509|p1 eth2|        |
| Host A +--------+ switch/  +---------->| switch/  +-------+ Host B |
|  data  +--------+ router   |maybe more | router   +-------+ backup |
|        |eth3  p2|          |switches   |          |p2 eth3|        |
+--------+        +----------+between the+----------+       +--------+
                              buildings


I think you refer to this part of the bonding documentation:

http://belnet.dl.sourceforge.net/sourceforge/bonding/bonding.txt
|12.2 Maximum Throughput in a Multiple Switch Topology
|-----------------------------------------------------
|
|	Multiple switches may be utilized to optimize for throughput
|when they are configured in parallel as part of an isolated network
|between two or more systems, for example:
|
|                       +-----------+
|                       |  Host A   | 
|                       +-+---+---+-+
|                         |   |   |
|                +--------+   |   +---------+
|                |            |             |
|         +------+---+  +-----+----+  +-----+----+
|         | Switch A |  | Switch B |  | Switch C |
|         +------+---+  +-----+----+  +-----+----+
|                |            |             |
|                +--------+   |   +---------+
|                         |   |   |
|                       +-+---+---+-+
|                       |  Host B   | 
|                       +-----------+
|
|[...]
|When employed in this fashion, the balance-rr mode allows individual
|connections between two hosts to effectively utilize greater than one
|interface's bandwidth.

But I don't have an isolated network. Maybe I'm still too blind to see a
simple solution.

Thanks, Ralf
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