Session Border Controller – SBC

I believe you already hear about  Session Border Controller  named  with acronims SBC . I will try to explain in short what is main purpose for this box. We can see from name this is the box which controll something between border. And what could be the border or better if we ask where is this border. We talk about Networks border and Session Border Controller is box which separate LAN (Local Area Network) and WAN (Wide Area Network) in IP telephony world. If we don’t know much about IP telephony we can say this is some kind of firewall fro IP telephony. SBCs are inserted into the signaling or media paths between calling and called parties in a VoIP call. Of course they using the Session Initiation Protocol (SIP), H.323, and MGCP call-signaling protocols.

In many cases, in order to hide the network topology and protect the service provider or enterprise packet network, the SBC will terminate a received call and initiate a second call leg to the destination party. In technical terms, when used within the SIP protocol, this is defined as being a back-to-back user agent (B2BUA). The effect of this behavior is that not only the signaling traffic, but also the media traffic  can be controlled with Session Border Controller  -  SBC. In cases where the SBC does not have the capability to provide media services on board, SBCs are also able to redirect media traffic to a different element elsewhere in the network, for recording, generation of music-on-hold, or other purposes. Conversely, without an SBC, the media traffic travels directly between the VoIP phones, without the in-network call signaling elements having control over their path.

Additionally, some SBCs  allows VoIP calls to be set up between two phones using different VoIP signaling protocols (e.g., SIP, H.323, Megaco/MGCP) as well as performing transcoding of the media stream when different codecs are in use (e.g., from g.722 to g711)

OK, now we know that SBC hiding “inside” network topology from outside world,  and this is very good if seen from the point of view  for network security.

SX1000 会话边界控制器 (Session Border Controller) 是迅时通信 VoIP 产品系列中的一款，专为解决网关流量汇聚、私网 / 防火墙穿透、网络安全、业务保证和网络互通等 VoIP 部署所面临的问题而设计。

SX1000 是 VoIP 整体解决方案中的重要部件，通常部署在 VoIP 服务供应商网络的边缘(软交换平台和语音接入网关之间)，或部署在企业 / VPN 网络的出口，以支撑 VoIP 业务的开展。