I got a hold of some Nortel IP phones at work and was doing some reaserch on how to connect them to an Asterisk server. At first I was using them with the UNIStim protocol support in Asterisk, but instead found out that you can download SIP firmware versions for most Nortel and Avaya phones directly from Avaya since they purchased Nortel.
You can get the SIP 4.x firmware here, or browse the other firmwares as well. You do not need a username and password to download them.
This site can help as well, to get you updated to a SIP firmware from UNIStim firmware and how to configure your TFTP settings.
I needed some more configuration settings in my TFTP DeviceConfig file so this is what I ended up using.
DNS_DOMAIN archaicbinary.home SIP_DOMAIN1 archaicbinary.home SERVER_IP1_1 192.168.XXX.XXX SERVER_PORT1_1 5060 SERVER_RETRIES1 3 DEF_USER1 6001 ENABLE_SERVICE_PACKAGE YES ENABLE_3WAY_CALL YES TRANSFER_TYPE STANDARD REDIRECT_TYPE RFC3261 FORCE_BANNER YES BANNER Zharvek UPDATE_USERS NO ENABLE_UPDATE YES ENABLE_PRACK YES RTP_MIN_PORT 50000 RTP_MAX_PORT 50100 SIP_PING YES AUTOLOGIN_ENABLE YES DEF_LANG English VMAIL *98 VMAIL_DELAY 300 EXP_MODULE_ENABLE YES ENABLE_BT YES DST_ENABLED YES TIMEZONE_OFFSET -18000 # (GMT-10:00) Hawaii -36000 # (GMT-09:00) Alaska -32400 # (GMT-08:00) Pacific time (US and Canada) -28800 # (GMT-07:00) Mountain time (US and Canada) -25200 # (GMT-06:00) Central time (US and Canada) -21600 # (GMT-05:00) Eastern time (US and Canada) -18000 # (GMT-04:00) Atlantic time (US and Canada) -14400 # (GMT-03:00) Brasilia, Buenos Aires -10800 # (GMT+00:00) Greenwich, Dublin, London 0 # (GMT+01:00) Amsterdam, Madrid, Paris 3600 # (GMT+02:00) Athens, Istanbul 7200 # (GMT+03:00) Moscow, St. Petersburg 10800 # (GMT+05:30) Bombay, Calcutta, Madras 18000 # (GMT+08:00) Beijing, Chongqing, Hong Kong 28800 # (GMT+09:00) Osaka, Sapporo, Tokyo, Seoul 32400 # (GMT+10:00) Canberra, Melbourne, Sydney 36000 # (GMT+12:00) Auckland, Wellington 43200 SNTP_ENABLE YES SNTP_SERVER pool.ntp.org AUTO_UPDATE YES AUTO_UPDATE_TIME 3600 # 48600 = 1:30pm # 3600 = 1:00am # 28800 = 8:00am 29700 # 54900 = 3:15pm AUTO_UPDATE_RANGE 1 MAX_INBOX_ENTRIES 50 MAX_OUTBOX_ENTRIES 50 MAX_REJECTREASONS 5 MAX_CALLSUBJECT 5 IM_NOTIFY NO IM_MODE DISABLED DEF_DISPLAY_IM NO MAX_IM_ENTRIES 20 MAX_ADDR_BOOK_ENTRIES 100 ADDR_BOOK_MODE BOTH RECOVERY_LEVEL 0 ADMIN_PASSWORD 123456789 DISABLE_PRIVACY_UI YES LOGOUT_WITHOUT_PASSWORD NO NAT_SIGNALING NONE NAT_MEDIA NONE HOLD_TYPE RFC2543