Communications Servers Replacing The “Mainframe” Switch
The traditional premise based switch (PBX) or central of-fice switch can be likened to the computer mainframe, a central hub of processing power and information. It is gradually be-ing replaced with a disaggregated architecture. As noted above, there are routing functions in the softswitch architecture. The routing function is most commonly a SIP Proxy. SIP proxies may be one of the following:
f 1. SIP Proxies will be servers on local area networks or con-nected to other networks, depending upon the size of the organization. There may be workgroup servers, depart-mental servers, floor servers, building servers, etc. These may be joined in a hierarchical design and by many dif-ferent network interfaces.
Proxy Servers
A proxy is an application running on a gateway that relays packets between a trusted “client” and an untrusted “host.” A proxy server is software that runs on a PC, allocating IP addresses to users as they need them to access the high speed Internet connection. It may be viewed as the “corporate telephone system”
for Internet access. In addition to managing access to the Internet, the proxy server also acts as a firewall, preventing unwanted intrusion from the Internet into your corporate computer network.
– Compliments of Newton’s Telecom Dictionary
f 2. Network or central office SIP Proxy servers (outside of the office, run by telephone companies) will follow the same architecture, distributed and joined by high-speed rings of cable. This approach is gradually replacing the central office switches that can now take up a building the size of a city block.
Since traditional PBXs were designed as computers dedi-cated to switching telephone calls, the need for more general purpose programming for “not yet imagined” applications was never considered. At the time most PBXs were designed, com-puters were still expensive and not as powerful as they have become. Thus, the designers’ perspective was that their switches would run faster skipping the overhead that would have provided more openness and flexibility and instead writ-ing their software code to a small “kernel.”
The “computer-like” part of a PBX is analogous to the com-bined capabilities of a media gateway controller and an applications server in the newer softswitch environment. The PBX circuit board for outside lines is analogous to the media gateway.
An open and public operating system will mean that people other than the manufacturer can program the communications servers, making them do things that the manufacturer never thought of or did not have time to address. The communica-tions server can be programmed do what the customer wants it to do. This is the premise of the trend towards more open telecommunications systems.
This openness still requires the skill of experienced and tal-ented programmers to design and test the new applications. The more ubiquitous and flexible the programming languages (like Java and C++), the more likely that new applications can be prac-tically developed, as there will be programmers available to design and support them.
The situation driving communications server development today is clear. The average traditional PBX contains three to five million lines of software code. Central office switches such at
Northern Telecom’s DMS 100 also contain several million lines of code. Adding a few new features requested by a customer re-quires regression testing. The new software code is tested in combination with all of the old code, simulating conditions of the telephone system under normal day-to-day use. This can be a prohibitively lengthy process and in many cases, can never be completed.
It is further complicated because it is unlikely that the pro-grammers writing the new code are the same propro-grammers who wrote the original code. (Code refers to the sequence of instruc-tions in software.)
Traditional PBX manufacturers respond to this phenom-enon by releasing new system features infrequently. When they do, a whole collection of new features is introduced, resulting in a very long time for testing before the new software can be released. Once released, these software upgrades can be costly to install and may still have “bugs” to be worked out with fixes called patches.
If a customer wants just one of the new features in the new software, he must still pay for the entire upgrade.
As switches incorporate more features and thus more software code as demanded by the customers, the chance of system failures and the time required for testing are both in-creasing exponentially.
While the manufacturers are being conservative in not offer-ing too many new features too quickly, the switch users have the experience of the programmability of PCs and want the same capability for their telephone systems.
The communications equipment “factory” of the future may make each system to the specific requirements of the customer who ordered it. The factory will assemble the network interface modules, the hardware modules and the software modules or pieces into a customized telecommunications solution. The manufacturer’s skill where value is added will be in three areas:
f 1. The Network Interface – The communications server manufacturer will make it possible to connect to T-1/PRI,
E1 (European equivalent of T-1), SS7, etc. This is not trivial. There are dozens of interfaces to telecommunica-tions networks. There are standards, but the tendency has been towards non-standard interfaces. For example, there are at least 20 varieties of ISDN Basic Rate Interface lines in North America, and even more internationally.
f 2. Making the communications server rugged, durable, re-dundant, and able to support areas that could be weak such as network interfaces and supplies.
f 3. Testing of products manufactured by others to work with the communications server. The communications server manufacturer will recommend the software modules, ob-jects and peripheral hardware that will work best with their system. It remains to be seen whether or not they will guarantee the performance of the products made by the other companies.
The benefits of the communications server architecture in-clude the following:
f 1. It is customized to your individual needs. You pay for what you need, and nothing more (unlike traditional PBXs, where you may never use many of the system features).
f 2. It can be truly different from what everyone else has and therefore provides a real competitive edge for your customers.
f 3. You can get the equipment and hardware you prefer since hardware, software and telephones will all work on most platforms. (Note: This may be coming, but most commu-nications servers are still proprietary requiring the use of the manufacturer’s telephones.) Even the desktop com-puter interfaces can be tailored to provide that with which the individual is most comfortable.
f 4. New features can be added quickly.
f 5. The life cycle of switches will decline, approaching that of PC’s and local area networks.
As the communications server industry develops and softswitch networks are deployed, time will tell how much of the above actually happens and how quickly. History tells us that technology never develops exactly as the industry gurus predict.