SBCs are put into the signaling and media path between calling and called party on VoIP networks, acting as if it were the called VoIP phone and placing a second call to the called party. The effect of this is that not only the signaling traffic, but also the media traffic (voice, video etc) crosses the SBC.

Without an SBC, the media traffic travels directly between the VoIP phones. Some SBCs also allow VoIP calls to be set up between phones using different signaling protocols such as SIP, H.323 or Megaco/MGCP and transcode between different codecs.

ENUM meanwhile is an IETF standard resulting from a joint effort by Telecordia and VeriSign. It uses the domain name system to map telephone numbers to domain names or URLs. Its goal is to provide a single number to replace the multiple numbers and addresses for an individual’s home phone, business phone, fax, cell phone, and e-mail.

The thrust of the deal between Redwood City, California-based Nominum and Acme Packet, which hails from Burlington, Massachusetts, is the combination of the former’s Navitas server for ENUM-based routing with the latter’s Net-Net SBC family for a joint VoIP peering offering.

VoIP peering is of interest to carriers, explained a spokesperson for Acme, in that it makes for more efficient routing of calls, either without conversion to traditional TDM [i.e. circuit-switched] traffic, or with conversion for only a minimal part of the trajectory.

This is of particular importance where carriers have to pay for termination on, or access across the PSTN network. For this reason, in the US, a lot of the interesting in VoIP peering is coming from cable operators, the Acme spokesperson commented.

Acme Packets was cited by Frost & Sullivan in a report in mid-2005 as the leader in the SBC market, being responsible for 50% of all sessions shipped over the five-quarter period studied by the analyst firm.

Acme has a very large share in the SBC market, commented Albert Gouyet, VP of marketing at Nominum, and they can now use Navitas for routing going out or going in to a VoIP network.