The PBX (or IP-PBX) is no longer the future of communications for most enterprises. Well over half of the lines and workloads on most PBXs today can and should be moved to other platforms or applications. A 7-step guide on How to Carve a PBX provides suggestions for this optimization.
A major key to this lower cost, higher-return and more flexible future is the gateway.
Most gateways from major providers include four important components:
1. IP, TDM and Analog Line Connection and Protocol Conversion are available so that almost any type of line or trunk or network can be connected to the gateway. The gateway converts the protocols as needed, for example digitizing an analog line (telephone, fax machine, monitoring device, ATM, etc.) for transmission over a Time Division Multiplexed (TDM) T1 trunk or over an IP-based SIP trunk or Ethernet backbone or Wide Area Network (WAN) service.
2. IP Addressing and Session Initiation Protocol (SIP) provides the necessary IP address information to any SIP-capable endpoints so that media streams can more efficiently flow directly between the two devices, rather than being routed through the gateway. Non-SIP connections to analog or TDM devices or trunks require routing the media stream through the gateway.
3. Directory-Based Routing and Directory Synchronization enable gateways to maintain a comprehensive address directory that is usually imported from and synchronized with the corporate Active Directory or LDAP directory. This is a very important function since this directory can contain addresses for the PBX, for any number of Unified Communication or Collaboration (UC or UCC) systems or social networks, for devices that are not associated with PBX or UCC systems, and for outside parties such as clients, partners or suppliers. Most gateways provide for rules and algorithms to reformat the addressing (internal extensions, public network numbers, SIP URLs, etc.) depending on the location of the connected devices.
4. Session Border Control (SBC) provides the necessary security at the network edge for any of the IP-based connections such as listed in point 1.
With these four capabilities, gateways offer powerful flexibility to optimize the communications network architecture in most mid-sized to large enterprises. Migration of users from a PBX to a UC system can be easily managed on a user-by-user or group-by-group basis. Analog devices that need nothing except the ability to dial and be dialed no longer need a PBX license or maintenance contract for their line. Users who are almost entirely remote can use only their cellular phone number without needing a PBX user license, but still be dialed as an internal number or an external Direct Inward Dial (DID) number.
Most PBX/IP-PBX producers offer their own gateways and SBCs, of course. Cisco's Integrated Services Routers (ISRs) can include all of the connectivity in point 1 and the addressing of points 2 and 3, and also be equipped with Cisco Unified Border Element (CUBE) software to provide the security of point 4.
The catch is that all of the directory numbers for the PBX vendor's gateways must be known to and licensed on the PBX, since the PBX is essentially the directory-based routing engine. While Cisco offers their UCL licensing for devices and their CUWL for people, most others don't distinguish the pricing between a device and a person. (Ever need to put a fax machine on hold? I think not!)
Some PBX vendors offer session manager capabilities to make their systems more competitive to gateways by including non-PBX entries in the session manager for call routing or application management. However, many session manager offers have limited directory management and synchronization functions, so administration is not as simple as with most directory-enabled gateways.
Overall, my recommendation is to take a close look at how the power of today's gateways can provide keys to unlocking the future communications architecture and resulting cost savings and business benefits for your enterprise. You can find out more about this at Enterprise Connect, of course. Leading producers of directory-enabled gateways and SBC products such as AudioCodes, Oracle (who purchased Acme Packet), and Sonus were quite present at Enterprise Connect 2014 and are expected at Enterprise Connect 2015 in Orlando, Florida, March 16 – 19, 2015, as well.
