There are several ways to categorize today’s contact centers based on the underlying technology and protocols which provide their capabilities. Knowing and understanding them, at least from a general point of view, is of paramount importance for everyone involved in running a contact center, from engineers and supervisors up to the senior management. In this post and several subsequent ones, we will briefly review the key technologies and protocols involved in various types of contact centers, and how these affect the features and functionality they can offer.
We will start by briefly examining the evolution from the classic circuit – switched telephony that dominated worldwide communications for almost a century and see how it evolved to today’s complex signaling – based protocols that allow a large amount of functionality and value added services to be added to a simple communication session. Appropriate links are provided for more information on several of these terms (most referring to wikipedia).
POTS - PSTN
Classic telephony (usually referred to as P.O.T.S. – Plain Old Telephony Service) has been virtually unchanged over the past century. While it has undergone some changes over the years, most notably the introduction of electronic exchanges and touch-tone dialing (DTMF), the basic principles remain the same. Over the years, a large network of switches came to be, interconnecting telephones all over the world. This network is known as PSTN (Public Switched Telephone Network) and includes a variety of physical interconnection mediums, ranging from copper wire to fiber optic cables and cellular networks, and a number of switches that act as hubs for these mediums.
ISDN: The first step to convergence
While the PSTN network was happily expanding and increasing its coverage in every corner of the globe, a wind of change started blowing in computing labs. The rapid expansion of computers of any type and size soon gave rise to the need of communication between them, to exchange data. Computer communication initially became important for military purposes, but it gradually became apparent that it could be applied in other activities too. As the PSTN was already in place, it was convenient to be used for data transmissions also. However, when the landline was used for data transmission, it was not possible to also use it for telephony at the same time. Thus the technology of ISDN (Integrated Services Digital Network) was developed, which allows for simultaneous digital transmission of voice and data.
Signaling: Enhancing capabilities in two worlds that are blending
During the same period that the computer and the telephony industry started affecting each other, another important change in mentality started taking place, related to signaling. Signaling refers to the use of signals during the information exchange concerning the establishment and control of a telecommunication circuit and the management of the network.
Traditional POTS/PSTN telephony uses in – band signaling (the signaling information was transmitted in the same channel as voice, along with it) and it offers limited call control capabilities (mostly call establishment and termination). More advanced protocols using in – band signaling, such as ISDN, can offer more capabilities, as they also transfer data along with voice.
Gradually, the need for more advanced communication control capabilities in telephony led to the separation of signaling from the data being transferred. Thus, out – of – band signaling was deployed. Several out – of – bound protocols were developed until the dominant protocol of SS7 became widely used during the last 30 years. SS7 is a common channel signaling system, which means that the signaling for several lines is carried in a single, common channel. We will discuss more details on SS7 and its importance to backbone networks and contact centers on subsequent posts.
Several years later after SS7, a similar signaling protocol was developed for the parallel world of data communications. This protocol, SIP (Session Initiation Protocol), similarly offers advanced signaling capabilities to data communications, being able to control transactions while staying independent on the medium used. SIP is the enabling mechanism for the concept of unified communications which is quickly becoming a part of more and more contact centers. Exploring SIP basics is also a very big topic in itself and will be examined in the future.
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