Calls drop after 15 to 40 seconds

Calls that cut off after 15 to 40 seconds nearly always point at SIP ALG on the router rather than at the phone system.

Calls that cut off after 15 to 40 seconds nearly always point at SIP ALG on the router rather than at the phone system.

Why that timing

The interval is the clue. A call that survives the ring but dies half a minute in is failing at the first moment the two ends need to confirm the session is still alive. Something in between is rewriting or dropping that traffic.

Check SIP ALG first

SIP ALG is a feature on many routers that inspects and rewrites call signalling. It is meant to help. With a hosted phone system it reliably breaks calls in exactly this way.

Switch it off in the router or firewall. The name varies: SIP ALG, SIP transformations, SIP helper. Your IT administrator or internet provider makes this change.

If that is not it

• Restart the modem or router, at home and at the office. It costs a minute and clears a surprising number of these.
• Check the firewall is not filtering the ports Collaboration uses.
• Try a cable instead of Wi-Fi. Wi-Fi that is fine for video can still drop the steady stream a call needs.

One person or everybody

This is the question worth answering before you start. If colleagues have the same problem, it is the shared connection and not your laptop, so open a ticket and say so. If it is only you, work through the list above first.

See also

• What the call quality score means
• I can hear them but they cannot hear me