Description

When a call is put on hold, the phone still sends out a packet through the RTP stream, at every 5 seconds, to keep the link open.

The sent packet is not a RTP packet, but a STUN message including a CHANGE-REQUEST attribute with no-change flags. There's no need to have a STUN-aware server to use this RTP Keepalive mechanism. If a STUN server reads that message, its handling results into no actions, since it indicates there's no changes about the RTP stream.

Content of the dummy (but still valid) STUN packet:

• STUN Message Type: Binding Request
• Transaction ID: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
• CHANGE-REQUEST attribute:
  • No IP change
  • No Port change

Set this setting to off to switch this behavior off.

Web User Interface

Advanced - SIP/RTP (Tab) - RTP/RTCP(Section): RTP Keepalive

Phone User Interface

N/A

Auto-provisioning