asterisk users - Mar 2004 - Need help understanding SIP phones

Greetings

i have been using asterisk with good success with soft phones and I 
need to purchase some Sip capable phones to test.

How would/do vendor specific phones like cisco 7900's and 3Com VCX 3100 
series phones work SIP to SIP if they download the protocol from the 
Vendor call centers?

I want to build my own with Asterisk, and use different phones. They 
say they are RFC 2543 compliant. Can you download the software and tftp 
to the unit? How does it work?

any insight would be helpful.

Thanks

-----------------------------------
jeff donovan
basd network operations
(610) 807 5571 x4
AIM  xtdonovan
fwd# 248217

>How would/do vendor specific phones like cisco 7900's and 3Com VCX 3100
>series phones work SIP to SIP if they download the protocol from the
>Vendor call centers?
At least in the 79xx's case, the phone actually downloads firmware updates
from a TFTP server; by changing the name of the image to use, you can make
it run SCCP/CallManager, SIP, MGCP (on the 7940/7960) or H.323 (on the
7905G) firmware. Note that you can't have multiple firmware images running
at once; you have to pick one. The phones have internal flash memory so they
don't have to download firmware every time, only when it's updated or
changed; they always download their configuration info from a set of text
files (SIPDefault.cnf, SIP<macaddr>.cnf) every time they boot, though.
Also
note that Cisco's super-low-end phones like the 7902G and 7910G only support
SCCP, and can't be changed; Asterisk has rudimentary support for SCCP, but I
don't know how functional it is.

I haven't looked at the 3Com phones, so I'm not sure exactly how they
operate, but I imagine it'd be similar to the Ciscos.

-lee