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@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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