The architecture for enterprise communications continues to evolve, reflecting the evolution of the overall enterprise IT architecture. This should be a constant area of skills development and expertise enhancement for enterprise communications professionals -- from telecom managers to vendors, systems integrators, and consultants.
Nature abhors a vacuum, so if the communications team is not leading the conversation in a direction that resonates with the CIO and the top-level enterprise architect, then others will establish the communications architectures for the future, with unpredictable outcomes.
Session border controllers (SBCs) and gateways, installed as software stacks on communications hardware appliances, are at the center of this evolution. The hardware provides connectivity to a range of communications services -- trunks, lines, IP networks. The software orchestrates the hardware to handle signaling, media, routing, and more. SBC software can run on the same hardware/software platform and provide connectivity for SIP trunks, Ethernet, or other IP links.
Redefining Call Switching
Gateways are redefining the very meaning of voice call switching in the all-IP world. In addition, gateways have an increasingly important role to play in adoption of cloud-based communications, since they are part of the connectivity between cloud solutions and on-premises systems, networks, and devices. You can find gateways today from a number of well-qualified, PBX-independent vendors, such as Adtran, AudioCodes, Edgewater Networks, Oracle Communications, Phybridge, Sonus Networks, and others.
In the past, the PBX ruled call switching. All of the telephone numbers existed in (and often only in) the PBX. The dial plan, programmed into the PBX, contained all of the rules for routing internal and external calls.
Dial plan programming is arcane, with each PBX make and model having its own language and options. Historically, dial plans have been so difficult to create and maintain that, for manageability, telecom managers often had to standardize on a single brand of PBX throughout the organization. Vendors had used the requirement for a single call control plane to justify the monolithic architecture.
In an era of software and distributed network architectures, these PBX-centric concepts are obsolete. Most enterprises already have multiple call control planes, even though only a few of those may connect to the public switched telephone network (PSTN). When users on one call control plane (such as Salesforce.com Chatter) need to talk to another call control plane (such as Microsoft Skype for Business, ,Avaya Aura, or Cisco Unified Call Manager), they talk through Internet protocols such as SIP, SIP/SIMPLE, or XMPP.
Gateway State of the Art
Which brings us back to gateways. The current state of the art in enterprise gateways includes these functions:
Many of the PBX vendors have their own versions of these same gateway functions. However, as usual, each vendor's solution is essentially a closed environment. PBX vendors, in other words, continue to focus on protecting themselves from competitive threats, rather than opening the services up to the industry for innovations. (I'm sure this will get some contrary posts, but that's what it looks like to us consultants and to our clients.)
By analogy to the software applications and IT architecture toward which communications technologies are evolving, the gateway roles are comparable to "enterprise message bus" software services and application middleware services. This is a proven model that has opened up significant opportunities and economies for applications; now communications architects will be well-served to follow this lead. SBC software can run on the same hardware/software platform for SIP trunks, Ethernet, or other IP connections.
So, get to know your gateways. You will likely find they open up many new opportunities for your enterprise and for your communications team.
