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8/6/2019 20081218 Linear RTPProxy v3
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RTP ProxyDate: 2008/12/18
Speaker: Ni-Ya Li
Advisor: Quincy Wu
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Outline Introduction
NAT STUN
Operation of RTP Proxy
Future work
Reference
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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
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Introduction (cont.) What is the NAT?
Network Address Translator, maps a private IP address to
a public one. Why use NAT?
Public IP addresses are almost exhausted!
Four types
Full cone
Restricted cone
Restricted port cone
Symmetric4
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Full cone NAT
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Picture from: http://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
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R estricted cone NAT
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Picture from: http://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
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R estricted port cone NAT
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Picture from: http://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
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Symmetric NAT
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Picture from: http://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
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Simple Traversal of UDP Through
Network Address Translators (STUN)
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10.10.21.17 : 5060
1. Client(10.10.21.17:5060) sends a request to STUN server with pubic IP
address (163.22.23.24)
2. STUN server gives a response with client¶s public IP address and port number
(163.22.5.59 : 56789)
3. Client use the public IP address and port (163.22.5.59 : 56789) to register to
SIP server
163.22.23.24
10.10.21.17 : 5060
163.22.5.59 : 56789
Picture from: http://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
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STUN (cont.) STUN can deal with the three type of cone NAT
Allocate a new media port, and every external host can
connect to internal client.
If client locates behind a symmetric NAT?
The previous allocated media port can not be used by the
other hosts.
Nothing heard !!We need a new tool to relay RTP pack ets
behind a symmetric NAT
RTP Proxy!!
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Operation of RTP Proxy When SIP server receives INVITE request
INVITE request,
extracts call-id
Session of
call-id exist?
Yes, returns UDP port number
No,Creates a new session,
return UDP port number
Rewrite media ip: port
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Operation of RTP Proxy When SIP server receives SIP response from
UA2 with SDP
Session of
call-id exist?
extracts call-id
No,
return error code
Yes, return UDP port number
Rewrite media ip:port
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Operation of RTP Proxy After session is created, RTP proxy listens on
the port for filling in the ip:port structure of
two side parties.
RTP streams
10.10.59.62 : 32768
10.10.21.17 : 7080
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Future work s Loading balance
Distributed RTP proxies
A central control SIP server, decides which RTP proxy will be responsible for this conversation.
SIP server gives a call to one of these RTP proxies
randomly, and the decision of doing a load balance is
made by proxies.
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R ef erence RTP Proxy
http://www.voip-info.org/wiki/view/RTPProxy
NAT, STUNhttp://ms11.voip.edu.tw/~webmaster/meeting/961/ppt/Wenping/20071122_wenping_STUN_v1.ppt
Nathelper module
http://www.kamailio.org/docs/modules/1.2.x/nathelper.html
SER Getting Started
http://siprouter.teigre.com/doc/gettingstarted/ch04s05.html
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