[Asterisk-Users] IAX2 Softphone Quality & Network Cards

[Rich Adamson]

> Everything is set to autoneg, NICs, switches and router 
> 

To ensure reasonable performance, key devices (eg, routers, servers)
should _always_ have duplex settings statically defined. Speed is
less of an issue as the 10/100 negotiation is hard to get wrong.

Part of the duplex negotiation problem is that consistent standards
have not been implemented by all manufacturers (and nic card drivers).
The two ends of a cat5 cable will often times try to auto negotiate
the duplex settings at roughly the same time, and 50% of the time it
will be wrong (eg, mismatched). As someone mentioned previously,
mismiatched duplex settings will seriously impact performance and
throughput.

Keep in mind that opening the cat5 cable at either end (eg, unplug
and replug the rj45) will cause a re-nogitation, as will a reboot,
etc.

There are a lot of systems and drivers that don't include the code
to tell you what the actual duplex setting is after a re-negotiation.
MS-based products are poor, and finding the actual setting in many of
the linux distro's is not necessarily easy.

For an asterisk server _always_ statically define the duplex setting
on both the switch and the nic card. On sip phones and workstations,
the duplex setting is less important, but should still match at both
ends of the cable.

(FWIW, my company does professional network performance assessments
and you couldn't even guess how many large & small corporate admins
don't have a clue. That's based on 12 years of experience at sites
in over 40 US states.)