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Browser softphone call flow

A study ladder: WebSocket handshake, SIP INVITE, answer, then DTLS on the media path. Step the hops.

Learn in 5 minutes

  1. Order the handshake before the INVITE
  2. Keep DTLS off the SIP transaction
  3. Use the step control to read one hop at a time

Visual

Browser softphone, study sequence · study drawing · cyphermonkeylabs.com BrowserSIP server GET 101 INVITE 100 180 200 ACK DTLS

SVG HTML PNG

Select a hop in the interactive flow. Each caption is a study note, not a packet captured from a vendor.

Worked example

Step the softphone ladder Play or step. Stop on DTLS and say which path it uses.

  1. Step through the handshake.
  2. Step to INVITE and read the proto token.
  3. Step to DTLS and name the path.

Fault

The ACK is present and RTP arrives in the clear. The debugger says the dialog is finished so encryption should be on.

RFC 5764 establishes SRTP keys with DTLS, independent of signaling.

Quiz

The first hop in this study flow is


INVITE on this flow is carried


DTLS belongs


100 Trying means


The Opus line in the offer uses


This ladder's addresses are


Ecosystem

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

CRM Screen pop uses data the contact center already has: ANI, DNIS, case id. Those values may arrive in SIP headers or in a CTI event after the call is up. The CRM is not a SIP element.

Glossary · Ecosystem map · Ports · Troubleshooting

Sources and go deeper