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RTP Proxy. Date:2008/12/11 Speaker: Ni-Ya Li Advisor: Quincy Wu. Outline. Introduction Operation of RTP Proxy Future work Reference. Introduction. RTP The real-time transport protocol to carry data that has real-time properties RTP proxy
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RTP Proxy Date:2008/12/11 Speaker: Ni-Ya Li Advisor: Quincy Wu
Outline • Introduction • Operation of RTP Proxy • Future work • Reference
Introduction • RTP • The real-time transport protocol to carry data that has real-time properties • RTP proxy • A software proxy for RTP streams, works with SIP server • Why use RTP Proxy? • Originally created for handling NAT scenarios • NAT (Network address translation), remaps address by modifying address in packet header
Operation of RTP Proxy • When SIP Proxy receives INVITE request, it extracts call-id and communicates it to the proxy call-id 1.receives INVITE request, extracts call-id
Operation of RTP Proxy • If the session exists, returns UDP port otherwise creates a new session, binds a first empty UDP port, and return the new port number Case 2: Creates a new session and return UDP port number Session of call-id exist? call-id Case1: Session exist, return UDP port number
Operation of RTP Proxy • After receiving reply from the proxy, SIP Proxy replaces media ip:port in the SDP to point to the proxy and forwards the request
Operation of RTP Proxy • When SIP Proxy receives non-negative SIP reply with SDP, extracts call-id to proxy • Proxy does not allocate a new session if call-id doesn't exist, but performs a lookup and returns either a port number if the session is found, or error code indicating that there is no session with such id • After receiving non-error reply from the RTPproxy, SIP Proxy replaces media ip:port as usual
Operation of RTP Proxy • After session be created, proxy listens on the port for filling in the ip:port structure of two side parties. • When both structures are filled in, the proxy starts relaying UDP packets between parties
Operation of RTP Proxy • The proxy tracks each existing session, and automatically cleans up a sessions which exceed the maximum idle time (default 60s)
Future works • Loading balance • Distributed RTP proxies • A central control SIP server, decides which RTP proxy will be responsible for this conversation. • SIP Proxy gives a call to one of these RTP proxies randomly, and the decision of doing a load balance is made by proxies.
Reference • http://www.voip-info.org/wiki/view/RTPProxy • http://www.kamailio.org/docs/modules/1.2.x/nathelper.html