13253: Dial: Header is too long

Twilio returns this warning when the SIP header data you send with <Dial><Sip> or in the To SIP URI is longer than the supported limit. Custom SIP headers are passed in the SIP URI, and the headers portion must be under 1024 characters.

• A custom SIP header appended to the SIP URI is longer than the supported 1024-character limit.
• A header sent with <Sip> uses a supported custom or standard SIP header name, but its value is too large. Twilio supports custom headers with the x- prefix and also supports User-to-User, Remote-Party-ID, P-Preferred-Identity, and P-Called-Party-ID in this format.
• The SIP URI includes header data in the To parameter, and the combined header content exceeds the allowed length.

• Shorten the header data you append to the SIP URI so the headers portion stays under 1024 characters.
• Remove any unnecessary custom SIP headers and send only the headers your SIP endpoint requires. For custom headers, use the x- prefix unless you are sending one of the supported standard SIP headers.
• If you create the call through the REST API, review the To parameter and confirm it contains a valid SIP URI. Keep the SIP URI body under 255 characters and keep the header data within the supported header limit.

• TwiML Voice: <Sip>
• Making SIP Calls
• TwiML Voice: <Dial>