[Asterisk-Users] Bonded ethernet ports and *

[Rich Adamson]

> Hey all - I'm sure this has been done before, but I'm curious about how well
> it works.. Typically we have all our servers setup for dual fast/gig
> ethernet failover... I.e. bond0 slaves eth0 and eth1 and fails over between
> the two. This together with dual p/s and raid1'd(at least) drives provides
> for a pretty safe solution(aside from building up a second server). So I'm
> courious thoughts/expectations/issues with doing network failover...
> Probably is a moot point, but I thought I'd ask.

I've done profession network assessments for a large number of companies
throughout the US and I've never ever seen bonded nics work as the
implementor expected them to work.

If you think seriously about how well the underlying OS and drivers function,
the length of the code path that must be executed to move packets from the
application layer all the way through to the nic card, you'll find that
most OS's are pressed very hard to keep a 1 gig interface running at max
smoke. Combine that with the overhead of tcp (not udp), latency, and the 
typical tcp windowing, and its even worse.

I'd also be checking exactly how the bonding function works in the 
primary/backup arrangement as several implementations that I've seen do
not handle shared mac addresses very well. That translates into arp table
timeout issues that essentially negates the expected benefits (eg, session
failures).

Could there be some good implementations? Probably, but just haven't seen
any persoanlly as yet.

>From a VoIP perspective, a 100 meg nic interface can (in theory) handle
1,176 simultanous g711 (or about 3,000 g729) conversations. That is 
significantly greater then what can be handled from a processing perspective
(assuming all conversations pass through asterisk code). If all 
conversations essentially involves canreinvite=yes, a 100 meg nic is still
not the bottleneck.

Last, the bonding of two nics at the server level _requires_ the associated
switch interface to support the exact same bonding algorithm. Historically,
that has been a problem for many switch vendors.

Short answer... I'd never do it. Long answer... think in terms of high
availability "systems"; the nic card is the least concerning.