Polycom V500 Release Note page 30

Release Notes
V500 and VSX systems, version 8.5
Feature Limitation
SIP V500 and VSX systems do not support firewall or NAT
traversal in SIP calls.
The MGC does not support Far End Camera Control in a SIP
conference.
The MGC does not support content sharing in a SIP
conference.
When Transport Protocol on the SIP Settings screen is set
to Both (TCP and UDP), the roll-over may cause a delay.
H.264 SIP calls do not support content sharing.
In SIP calls between a VSX system running 7.5.2 and a
VSX system running 8.0, the system running 8.0 cannot use
Far End Camera Control.
SIP transfers always report back successful, even if they fail
to transfer successfully.
SIP registrar server status is not displayed on the System
Status page on the web interface. The status is displayed
correctly on the system's user interface.
SIP calls may fail about 5% of the time when registered to a
Nortel server.
When a system is registered to Global Directory
Server/Global Address Book and SIP is enabled instead of
H.323, a non-ISDN system may show an incorrect alert
message for Global Directory Server/Global Address Book
registration.
In 64 kbps SIP calls between a VSX system and Windows
Messenger, Windows Messenger may not receive video.
When packet loss occurs, SIP calls may hang up
automatically.
When a Polycom SIP phone IP601 1.6 calls into a
VSX system, the IP phone does not receive audio from the
VSX system.
SIP calls do not work reliably between systems running
software version 8.0 and systems running version 7.x.
Do not transfer either end of a SIP call that is connected to a
VSX system.
In SIP multipoint calls with VSX systems running 7.5.x, the
7.5.x systems may crash.
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