[1] Early deployments of SBCs were focused on the borders between two service provider networks in a peering environment.
A more complex example is that of a large corporation where different departments have security needs for each location and perhaps for each kind of data.
In such a case the SBC acts as a gateway between the WebRTC applications and SIP end points.
Conversely, without an SBC, the media traffic travels directly between the endpoints, without the in-network call signaling elements having control over their path.
The proxy does not change any dialog identification information present in the message such as the tag in the From header, the Call-Id or the Cseq.
After successfully finishing the session initiation phase the user agents can exchange the media traffic directly between each other without the involvement of the proxy.
If the SBC is not expected to control the media traffic then there might be no need to change anything in the SDP body.
SBCs are often used by corporations along with firewalls and intrusion prevention systems (IPS) to enable VoIP calls to and from a protected enterprise network.
Most SBCs also provide firewall features for VoIP traffic (denial of service protection, call filtering, bandwidth management).
Protocol normalization and header manipulation is also commonly provided by SBCs, enabling communication between different vendors and networks.
From an IP Multimedia Subsystem (IMS) or 3GPP (3rd Generation Partnership Project) architecture perspective, the SBC is the integration of the P-CSCF and IMS-ALG at the signaling plane and the IMS Access Gateway at the media plane on the access side.
Those who wanted unfettered control in the endpoints only, were also greatly frustrated by the various realities of modern networks, such as firewalls and filtering/throttling.
According to Jonathan Rosenberg, the author of RFC 3261 (SIP) and numerous other related RFCs, Dynamicsoft developed the first working SBC in conjunction with Aravox, but the product never truly gained marketshare.
[citation needed] Newport Networks was the first to have an IPO on the London Stock Exchange's AIM in May 2004 (NNG), while Cisco has been publicly traded since 1990.
With the field narrowed by acquisition, NexTone merged with Reefpoint becoming Nextpoint, which was subsequently acquired in 2008 by Genband.
The continuing growth of VoIP networks pushes SBCs further to the edge, mandating adaptation in capacity and complexity.
Others, have developed new architectures using the latest generation chipsets offering higher performance SBCs and scalability using service cards.