Support For Transport Layer Protocols - HP FlexNetwork MSR Series Configuration Manual

Figure 39 Call redirection procedure for UAs
User agent
302 Moved Temporarily
This is a common application. Fundamentally, a redirect server can respond with the address of a
proxy server as well. The subsequent call procedures are the same as the call procedures involving
proxy servers.

Support for transport layer protocols

As an application layer protocol, SIP supports the following transport layer protocols:
•
UDP—UDP is a connectionless protocol and does not provide reliability; therefore, SIP
connections established over UDP are unreliable.
•
TCP—Ensures transmission reliability for SIP messages. TCP provides connection-oriented
and reliable transmission for SIP-based VoIP communications. Using TCP, SIP need not
consider packet loss and retransmission issues.
•
Transport layer security (TLS)—Ensures transmission security for SIP messages. For more
information, see
These transport layer protocols have their own benefits, enabling you to select a protocol based on
your network environment. The system does not support transport layer protocol switchover during
communication.
SIP security
Signaling encryption
TLS runs over TCP and provides a complete set of authentication and encryption solutions for
application layer protocols. When establishing a TLS connection, both sides need to authenticate
each other by using their own digital certificates and can communicate with each other only after
Internet
Redirect Server
INVITE
100 Trying
ACK
INVITE
100 Trying
200 OK
ACK
encryption."
"Signaling
User agent
135