[Asterisk-doc] (Fwd) Re: [Asterisk-Users] re hardware requirement - asterisk

[Philipp von Klitzing]

Here comes part three to the "duplex story" and why it matters.

------- Forwarded message follows -------
Date sent:      	Thu, 15 Jan 2004 13:54:00 -0600
From:           	Rich Adamson <radamson@routers.com>
Subject:        	Re: [Asterisk-Users] re hardware requirement - asterisk
To:             	asterisk-users@lists.digium.com
Send reply to:  	asterisk-users@lists.digium.com

[...]
Just for fun, I moved our * box to a 10meg al-cheapo hub to force 10-half,
placed a sip-to-sip call (via two C7960's) and noticed audio was very
much half duplex. Very irritating to say the least (worse then most digital
cell-to-cell calls).

Then without changing anything other then moving the * interface to an
upstream switch running 100 full (and verifying settings), the 
half-duplex-sounding audio effects completely disappeared (as expected).

While both tests were being conducted, I ran a Sniffer analyzer to monitor
packets and validate results.

10-half vs 10-full does have a substantial impact on quality. Moving from
10-full to 100-full would have no impact unless I could have loaded it
with more rtp sessions then what I currently have the ability to do.
And, FWIW, an interface set to half-duplex on one end with full-duplex
on the other end was by far worse then when both ends of the cat 5 matched.

All tests were conducted by forcing rtp traffic "thru" * (didn't allow
the rtp to flow between the two sip phones).

BTW, 10-Full setting is truly available on a large number of NICs, but
not all. Obviously, the older stuff didn't support it, nor do the older
Cisco 10 meg interfaces, etc.