Polycom SIP 3.1 Administrator's Manual page 54

Administrator's Guide SoundPoint IP / SoundStation IP
3 - 22
For more information, refer to "Technical Bulletin 35311: Supporting
SoundPoint IP 300 and IP 500 Phones with SIP 2.2 and Later Releases" at
http://www.polycom.com/usa/en/support/voice/soundpoint_ip/VoIP_T
echnical_Bulletins_pub.html .