[Serusers] Outbound proxy definition

Klaus Darilion klaus.mailinglists at pernau.at
Wed Mar 2 10:01:41 CET 2005


Hi Thomas!

First, the definition from RFC 3261:


>Outbound Proxy: A proxy that receives requests from a client, even
>         though it may not be the server resolved by the Request-URI.
>         Typically, a UA is manually configured with an outbound proxy,
>         or can learn about one through auto-configuration protocols.

Typically, SIP messages are sent to the SIP proxy which is responsible
for this domain. that means if the request URI is sip:klaus at iptel.org,
the meassage will be sent to the SIP proxy of iptel.org.

In same cases, it is requiered that the SIP messages passes a certain
SIP proxy. E.g. in enterprise environments with certain security
policies all SIP messages will be controlled by the company's SIP proxy
before they will leave the corporate network. Another scenario is NAT
traversal. If the iptel.org's SIP proxy wouldn't do NAT traversal, you
can insert a certain SIP proxy into the signaling path, which is
responsible for NAT traversal.

In this cases, this additional SIP proxies will be called Outboundproxy.
If a SIP UA is configured with an outboundproxy, all SIP requests will
be sent to the outboundproxy instead of sending it directly to the SIP
proxy indicated in the request URI.

In certain cases (NAT travesal, security ...) the outboundproxy also
rewrites the SDP in the SIP messages to direct audio to an RTP proxy.

regards,
Klaus


support wrote:

> Hi,
>  
> I am really frustrated with the definition of outbound proxy:
>  
> /The outbound proxy is a normal SIP proxy. You configure your client, 
> the phone or software, to use the proxy for *all* SIP sessions./
>  
> I would like to know what is meant by *all SIP sessions*? Does it 
> include all SIP message as well as voice packets (i.e. RTP packets)?
>  
> Could I conclude that outbound proxy = ser + nathelper + 
> rtpproxy/mediaproxy?
>  
>  
> Hope someone could answer my questions. Thanks.
>  
>  
> Thomas
> 
> 
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