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SIP Mastery

A free, open course · 33 modules

Learn SIP by watching it work

From the first REGISTER to one-way audio behind NAT. Every concept is an interactive call flow you can step through, message by message, with the RFC sentence that defines it.

Start with Module 0 →See the course map
  • SIP
  • SDP
  • RTP media
  • RTCP
  • DNS / ICE
  • Error

Path · Support and NOC

Read a trace. Find the fault.

Header meanings, call flows, response codes, NAT, and media faults. Every common mistake is a diagram you can switch between broken and fixed.

Path · Developers

Build SIP that follows the RFC.

Transaction and dialog state machines, matching rules, timers, and message construction, with the exact RFC text for every rule.

Course map

Twelve parts, from basics to advanced. Live modules are marked; the others follow.

Part 0

Orientation

  1. 00Anatomy of one phone callBasic

Part 1

Foundations

  1. 01VoIP and where SIP fitsBasic
  2. 02Networking for SIPBasic

Part 2

The SIP language

  1. 03SIP elements and addressesBasic
  2. 04Anatomy of a SIP messageBasic
  3. 05SIP methodsBasic → Intermediate
  4. 06Response codesBasic → Intermediate
  5. 07Headers and parametersIntermediate

Part 3

SIP mechanics

  1. 08TransactionsIntermediate → Advanced
  2. 09DialogsIntermediate → Advanced
  3. 10Routing: Via, Record-Route, RouteAdvanced
  4. 11Finding SIP servers with DNSAdvanced

Part 4

Registration, authentication, security

  1. 12RegistrationBasic → Intermediate
  2. 13Digest authenticationIntermediate → Advanced
  3. 14SIP securityAdvanced

Part 5

Media

  1. 15SDP and offer/answersoon
  2. 16RTPsoon
  3. 17RTCPsoon
  4. 18SRTP and media securitysoon

Part 6

Transports

  1. 19SIP over UDP, TCP, TLS, and WebSocketsoon

Part 7

NAT traversal

  1. 20NAT and SIPsoon

Part 8

Call flow library

  1. 21Basic call flowssoon
  2. 22Mid-call featuressoon
  3. 23Events, presence, and messagingsoon
  4. 24PSTN interworking and SIP trunkssoon

Part 9

SIP in the real world

  1. 25Proxies, B2BUAs, and SBCssoon
  2. 26WebRTC and SIPsoon
  3. 27IMS and VoLTEsoon
  4. 28Caller identity: STIR/SHAKENsoon
  5. 29Voice qualitysoon

Part 10

Troubleshooting

  1. 30Reading tracessoon
  2. 31Troubleshooting playbooksoon

Part 11

Case files

  1. 32Case filessoon