438 4xx Client error RFC 8224
SIP 438 Invalid Identity Header
The Identity header signature could not be verified.
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Common causes
- Header modified in transit, wrong 'orig' or 'dest' number, or clock skew.
How to fix it
- Make sure intermediate devices don't change From, To or Date after signing. Check NTP.
Seeing 438 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.