ð sip-protocol-fundamentals
Use when working with SIP messages, methods, call flows, and protocol fundamentals for VoIP applications.
Overview
Master the Session Initiation Protocol (SIP) for building VoIP applications, understanding SIP messages, methods, and call flows essential for real-time communications.
Understanding SIP
SIP is an application-layer signaling protocol defined in RFC 3261 for creating, modifying, and terminating sessions with one or more participants.
SIP Message Structure
INVITE sip:bob@biloxi.com SIP/2.0
Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sip:bob@biloxi.com>
From: Alice <sip:alice@atlanta.com>;tag=1928301774
Call-ID: a84b4c76e66710@pc33.atlanta.com
CSeq: 314159 INVITE
Contact: <sip:alice@pc33.atlanta.com>
Content-Type: application/sdp
Content-Length: 142
When to Use This Skill
Use sip-protocol-fundamentals when building VoIP applications with SIP signaling.
Best Practices
- Always include unique branch parameters in Via headers
- Implement proper transaction timeout and retransmission
- Handle all SIP response codes appropriately
Common Pitfalls
- Forgetting to include branch parameter in Via headers
- Not implementing transaction retransmission timers
- Ignoring provisional responses