Nortel developed there own protocol called Unistim. They have licensed the protocol to a variety of vendors - Spectralink being one of them. It is based off of RFC3054. Nortel's implementation of it uses the following L4 ports.
Ports
* 4100/udp Nortel UNIStim (Unified Networks IP Stimulus), i200x
* 5000/rudp Nortel UNIStim (Unified Networks IP Stimulus), i2002/i2004 on ITG Line
* 5100/rudp Nortel UNIStim (Unified Networks IP Stimulus), ITG Line
* 5105/udp Nortel UNIStim (Unified Networks IP Stimulus) FTP (UFTP)
* 6800/tcp Nortel Unified Manager
* 7000/rudp Nortel UNIStim (Unified Networks IP Stimulus), BCM FP1 VoIP to/from IP Phones
Here is a packet decode if you wish to do further analysis.
https://wiki.wireshark.org/UNISTIM