I've been a product manager of Voice over IP gateway products for about nine years, but I continue to learn about customer needs and expectations.   During the past 3 years, I've managed the Dialogic® IMG Integrated Media Gateway products and we've spend a lot of time talking with Tier 2-4 carriers and the various partners, systems integrators and OEMs that sell to them.  

The big change in gateways in the past 4 years has been the rise of SIP (Session Initiation Protocol).   In my early years as a VoIP product manager, IP call control was a subject of fierce debate and various protocols (H.323, MGCP, H.248) contended with SIP.    SIP was not really designed with VoIP gateways in mind, but as it has gained mind share as the way to develop enhanced services, it has outpaced all of the other IP protocols and become the most favored protocol for the IP side of carrier gateways.   In fact, we've seen a great deal of interest in a new kind of SIP to SIP gateway, which I'll plan to talk about in another post. 

SIP gateways are very well suited for the network edge.   The basic concept is to put a gateway on the edge of the network and use the gateway to perform both signaling and media translation between the circuit-based Public Switched Telephone Network (PSTN) and an IP network.   Usually, the new backbone network will be IP, so that gateways enable carriers to leverage existing PSTN switch assets and serve PSTN connected subscribers.   At the same time, once the traffic has been converted to IP, the IP network is much easier to develop and manage than its circuit based predecessors and carriers can quickly build new revenue generating enhanced services on top of it.  

Very often these PSTN to SIP gateways will be placed in a data center type of setting, rather than in a traditional Central Office, and the ability to have a small form factor and network in between gateways becomes important.   In essence, the basic value proposition for a 1U (one Rack Unit or 1.75 inches) VoIP gateway for carriers is very different than that of the traditional TDM switch; the ability to start small and grow to meet expanded requirements by just adding another 1U gateway is paramount.   By using only 1U per gateway, the carrier conserves telecom rack space, which is usually a monthly operating expense, and may save capital expense by consolidating multiple gateway functions in a single box.  

Does that mean that Tier 2-4 carriers don't care about the traditional telecom values of high availability and 5 9's?   In my experience, the answer is no.   Carriers want the flexibility of using small gateway platforms and being able to rack and stack them together, but they still need to keep the network up for a high percentage of the time.  So, the old school values of high availability and redundancy are still important to carriers, even if they are moving to a new generation of equipment. 

The challenge for modern gateway companies selling to carriers is to find a way to provide the value of a small footprint gateway and also meet the "old school" needs for keeping the network up and running.   At Dialogic, we've added features to our IMG gateway products to meet these needs.   SS7 signaling is a popular feature, but our customers don't want to lose active SS7 sessions, so we provide an active / standby SS7 redundancy feature between gateways to keep the sessions up and running.   When the time comes for software upgrades, carriers want to keep accepting calls, so we've developed graceful upgrades to enable one gateway to be upgraded, while another gateway keeps running active traffic.   Some customers want to treat SIP gateways as a pool of resources, so we've worked with partners to enable server-based load balancers to be placed in front of several gateways.   

These are just some examples of how we've responded to customer requests for the old school virtues of high availability and redundancy, while still retaining the small footprint and rack and stack capabilities which drew customers to scalable SIP gateways in the first place.   I'm always on the lookout for better ways to add value to VoIP carrier gateways, so if you have ideas along these lines, please leave a comment.