The IP-to-IP Gateway Evolution - An update on the evolving "Session Controller" space

A contribution from Netrake - December 2003

As the market for Voice over IP network interconnection grows and matures, the role of session controllers is changing in carrier networks. A session controller is defined as a network element that integrates two primary functions – signaling and media mediation. Session controllers serve as a demarcation point interconnecting two VoIP networks (carrier to carrier, carrier to enterprise, carrier to consumer), thus allowing VoIP carriers to peer more cost-effectively and with a greater control of security and reliability over native IP.

Vendor implementations of session controllers differ greatly, however, with emphasis on different functions, depending on product origins, architecture and competitive positioning. Early session controllers emphasized signaling or software functionality as an extension to a softswitch. Capacity requirements of early adopter VoIP carriers were low (only a few hundred concurrent calls had to be supported), while the need for few features such as firewall, NAT, and protocol translation was high. Early devices were designed as network appliances, or network control planes, to meet these specialized requirements and to conform to emerging standards for a separate signaling element. They worked great for signaling, but they simply could not scale to meet both signaling and media demands as VoIP deployments grew larger.

Today, as large, incumbent carriers adopt VoIP in their networks, a dedicated critical network element is needed in order to process thousands of simultaneous calls without adding latency at full capacity. Because it focuses on delivery of real-time communications, the network element needs to incorporate new resource-intensive capabilities such as private addressing, rogue RTP, redundancy - measured in zero call loss, and latency measured in microseconds at full capacity.

Today, a new term is being introduced to the market in order to differentiate these functions from the signaling or software-based functionality of session controllers that is described above. That term is “IP-to-IP gateway.” While session controllers offer a subset of the functionality of IP-to-IP gateways, they do not offer the entire solution. Session controllers focus on firewall and NAT traversal, protocol internetworking and quality of service features, while IP-to-IP gateways handle all of this and more, delivering much higher levels of security, performance, scale and reliability.

A few vendors are attempting to ‘graft’ an IP-to-IP gateway onto their media gateways, which of course were originally designed as PSTN-to-IP network elements to convert PSTN calls to IP in the network using expensive DSPs. The result is a high-cost, ‘one arm bandit’ configuration where IP-to-IP gateway functionality is an afterthought. The configuration does not fully satisfy requirements for IP network control, such as VoIP demarcation, private addressing, advanced media processing for security and SLA enforcement.

Netrake: The Right IP-to-IP Gateway Approach
Netrake has adopted a more balanced approach to VoIP network interconnection. The Netrake product is built with programmable, purpose-built network processors. The result is scalabiilty to thousands of simultaneous calls without latency, providing full redundancy with no lost calls in the case of network failure, and meeting enhanced signaling requirements for features such as firewall, NAT, protocol conversion, security admission control, QoS mediation and detail records.

Netrake’s solution extends the “traditional” functionality of session controllers, creating an IP-to-IP gateway that meets the peering needs of VoIP service providers today – instead of simply providing limited functionality as an afterthought within an expensive media gateway. Netrake’s balanced approach provides investment protection for Voice over IP carriers, regardless of what feature functionality requirements. But more importantly, Netrake enables these carriers to interconnect VoIP networks end-to-end - extending Voice over IP benefits and enjoying new economies of scale.

www.netrake.com