428 4xx Client error RFC 8224
SIP 428 Use Identity Header
The server requires an Identity header (STIR/SHAKEN) and none was supplied.
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Common causes
- A carrier that enforces signed caller ID.
How to fix it
- Have your carrier or SBC sign calls, or route through a provider that handles STIR/SHAKEN.
Seeing 428 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.