SIP 488 Not Acceptable Here

What this response means

The proposed session parameters cannot be accepted at this destination. In voice deployments, media negotiation is a useful first area to investigate.

Read it in context

Codec overlap, SDP structure, media-security policy or another session constraint can be involved. It is not safe to conclude that one particular codec is always missing from the code alone.

Administrator checks

Compare offer and answer-related details on the rejecting leg. Review accepted audio formats, RTP event support, encryption requirements and any diagnostic headers or logs. A PBX can negotiate different formats on each side, so inspect both legs.

On Asterisk PJSIP, first identify whether Asterisk generated the response on the incoming leg or received it from the far endpoint. Then compare the offer with the loaded endpoint and codec-negotiation preferences. Use the focused Asterisk investigation for the full evidence path.

Next action and common mistake

Do not enable every codec or disable SRTP indiscriminately. Establish a documented compatible policy and test incoming, outgoing and transferred calls. Confirm actual negotiated media and sound after setup succeeds.

Preserve the overridden offer before diagnosing 488

When dialplan changes an outbound PJSIP codec list, the PJSIP_MEDIA_OFFER diagnostic captures the callee channel, emitted SDP and rejecting leg before policy is widened.