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Pass-through headers

FlySIP is a back-to-back user agent: it builds a new INVITE for the vendor and does not copy the caller’s headers into it. When a partner network relies on a header the switch does not process, for example Remote-Party-ID or a custom X- header, list it as a pass-through header. The switch then copies it unchanged to the next call leg.

How it works

Section titled “How it works”
  1. You list the header names in Pass-Through Headers in System Management → SIP Features → SIP, separated by commas: Remote-Party-ID, X-Billing-Ref. Names are not case-sensitive.
  2. For every incoming INVITE, the switch looks for these headers and keeps every copy it finds.
  3. The switch adds the kept headers, unchanged, to each outgoing INVITE of the call: to every vendor it hunts through, and to on-net and Follow Me legs.

The list is switch-wide; there is no per-account or per-connection filter. It is stored in the configuration key system/sip/headers/passthrough, which you can also read and change with getSystemConfig and setSystemConfig of the XML-RPC API.

Screenshot "admin-panel/sip-features-sip" has not been generated yet — see scripts/screenshots/screens.yml.

Key terms

Section titled “Key terms”
  • Connection — a route to a vendor (SIP host, port, protocol, codecs) used by routing to send calls.
  • XML-RPC API — the programmatic interface of the softswitch and the panel used by integrations and by the panel itself.

Common scenarios

Section titled “Common scenarios”

A vendor needs the caller’s Remote-Party-ID exactly as received

Section titled “A vendor needs the caller’s Remote-Party-ID exactly as received”

Add Remote-Party-ID to Pass-Through Headers. The vendor gets the header byte for byte, with the caller’s host and parameters.

The vendor needs Remote-Party-ID, but the caller sends P-Asserted-Identity

Section titled “The vendor needs Remote-Party-ID, but the caller sends P-Asserted-Identity”

Pass-through cannot convert headers. Use the identity settings instead: they read either header and send either one. See Asserted identity and privacy.

Section titled “Related pages”