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Headers and compact forms

Compact header names are aliases from RFC 3261, with a few more aliases defined in the extension RFCs.

Learn in 5 minutes

  1. Expand the RFC 3261 compact forms
  2. Keep extension compact forms with their RFCs
  3. See why rewriting From or To breaks dialog matching

Visual

Compact request, long response · study drawing · cyphermonkeylabs.com UAPeer INVITE 100 200 ACK

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One character is the whole header name. Unknown one-letter names are not a license to invent aliases.

Worked example

Rewrite From on purpose Run the profile. It is legal syntax and a dangerous edit. See which URI the From header contains afterward.

  1. Read the rule.
  2. Run it on the INVITE.
  3. Compare the From URI with the original.

Fault

The SBC rewrites the From URI on the INVITE. The callee answers, and the caller's ACK gets 481.

The peer stored the From it was given. The ACK still has the caller's original From.

Quiz

The compact form of Call-ID is


The compact form of Contact is


Event's compact form o is defined in


Refer-To's compact form is


Compact form changes


A profile that replaces the From URI


Ecosystem

Glossary, sister systems, and the integration seam for this room.

E911 / emergency calling Location has to ride with the call. RFC 6881 is the BCP, RFC 6442 carries location in SIP, and the FCC MLTS page states Kari’s Law and RAY BAUM’s Act obligations for multi-line systems.

Glossary · Ecosystem map · Ports · Troubleshooting

Sources and go deeper