416 4xx Client error RFC 3261
SIP 416 Unsupported URI Scheme
The server does not support the URI scheme in the Request-URI (for example tel: or sips:).
Typical Q.850 / ISDN cause: 127 (Interworking, unspecified)
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Common causes
- Sending tel: URIs or sips: to servers that only accept sip:.
How to fix it
- Convert to a sip: URI with user=phone, or enable TLS for sips:.
Seeing 416 on calls through a router or firewall? Check that SIP ALG is disabled. It causes a surprising number of SIP errors. Read why.
About 4xx responses
The request has a problem or cannot be completed at this server, usually because of something on the requesting side or the target user.