505
SIP
505 Version Not Supported
The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
On this page
When You See This Code
Extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
How to Fix
Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.
Specification
Compare With
Guides
401 Unauthorized vs 403 Forbidden: When to Use Each
Security & Authentication
SIP Response Codes: Understanding VoIP Call Flow
Real-Time Protocols
SIP Call Flow: Understanding Session Setup
Real-Time Protocols
WebRTC Signaling with SIP and WebSocket
Real-Time Protocols
RFC 3261: SIP Protocol Deep Dive
Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure
Protocol Deep Dives
Glossary
Status Code
Request Method (HTTP Verb)
TLS Handshake
Authentication
TCP/IP
Port Number
NAT (Network Address Translation)
Socket
Request-Response Model
RFC (Request for Comments)
Connection-Oriented
Full-Duplex
SRV Record
SIP Dialog
Signaling
SIP Registrar
STUN (Session Traversal Utilities for NAT)
TURN (Traversal Using Relays around NAT)
SDP (Session Description Protocol)
SIP INVITE
SIP Proxy Server
SIP Redirect Server
SIP Transaction
SIP User Agent
SIP Trunk
RTP (Real-time Transport Protocol)
SRTP (Secure Real-time Transport Protocol)
SIP ACK
SIP BYE
SIP CANCEL
SIP OPTIONS
SIP SUBSCRIBE/NOTIFY
B2BUA (Back-to-Back User Agent)
SBC (Session Border Controller)
Codec Negotiation
SIP Response Classes
VoIP (Voice over IP)
Presence (SIP)
PBX (Private Branch Exchange)
MFA (Multi-Factor Authentication)
TLS Versions
Frequently Asked Questions
What is SIP 505 Version Not Supported?
The server does not support the SIP protocol version that was used in the request. Currently only SIP/2.0 is standardized.
When do you see SIP 505 Version Not Supported?
Extremely rare. Would occur if a client sends a request with a SIP version other than 2.0.
How to fix SIP 505 Version Not Supported?
Ensure your UA uses SIP/2.0 in the request line. This is the only standardized version.