SIP Outbound Proxy

First lets start by explaining the difference between SIP & RTP in a very simple way:

SIP (Session Initiation Protocol) handles the signaling part of a communication over the Internet and helps in establishing calls between end-users. RTP (Real Time Protocol), at the other hand, carries multimedia packets (audio, video, instant messaging...) being transferred between calling parties once the call is established.

SIP and RTP together to allow VoIP calls to take place. In general, SIP signaling involves an intermediate agent called SIP Proxy – a server reachable on a public address – which knows both parties locations and helps them to find one another, while RTP packets are meant to travel either directly between the two calling agents or via a media proxy.

What is SIP Outbound Proxy?

A SIP Outbound Proxy acts, like any proxy server, as a middleman between two communicating agents, serving as a transit point for all SIP traffic. You configure your SIP client to use the SIP Outbound Proxy server just as you would configure your web browser to use a proxy. Listening on an unblocked port number and forwarding requests between your SIP client and your VoIP provider, it helps bypassing the restrictions imposed by your Internet provider.

How do I configure my SIP client?

To start using a SIP Outbound Proxy service, you just need to enable outbound proxy settings in your SIP client and use the following domain: port as your outbound proxy:

proxy.sipoutbound.com:53

If you are not very familiar with SIP configuration, you may refer to step-by-step configuration procedures under the Configuration menu for the most known SIP Clients: E.g Huawei SIP devices  (Huawei AR Router/SIP Phones). Should you need more help configuring your device, please contact experienced huawei vendor personnel.

How does SIP Outbound Proxy help bypassing VoIP-blocking operators?

Usually, operators do block SIP traffic by applying restrictions on SIP UDP port (5060) and/or on IP addresses of most known VoIP providers as well. SIP Outbound Proxy is configured to listen to SIP messages on a different port number (e.g. DNS port number: 53) which can’t be blocked by operators. That way, the SIP traffic could bypass the providers restrictions to reach the proxy server before being forwarded to the VoIP provider. However, SIP Outbound Proxy doesn’t carry RTP traffic, which usually flows directly between SIP agent and VoIP provider without being subject to operator restrictions.

Will SIP Outbound Proxy expose my SIP credentials to third parties?

Not at all.

First, we never ask you for your password.

Second, SIP protocol encrypts your password using MD5 hashing algorithm, making it impossible to guess it by looking at the SIP traffic.

Will SIP Outbound Proxy service cause any degradation of the call quality?

No.

Voice and multimedia traffic (RTP) are exchanged directly between you and your VoIP provider without passing by our proxy server which just handles SIP signaling. SIP Oubtound Proxy never interferes with this communication, and the call quality is solely affected by your Internet connection and your SIP providers platform.

As for signalling, SIP Outbound Proxys platform is built on dedicated servers to guarantee you a robust performance and high availability.

Does SIP Outbound Proxy service work behind ALG routers?

Yes.

Most providers give their customers locked, pre-configured routers with ALG (Application-Layer Gateway) enabled by default. ALG tries to modify the content of SIP packets, but very often breaks the SIP communication. SIP Outbound Proxy guarantees a fully-working service if your SIP client is running behind an ALG-enabled router.