Resurrection of ISDN

ISDN was initially developed to provide integrated services digital network over a public circuit switched network. It had the following advantages over the POTS circuit switched system. Over a single cable pair, it could deliver

i. Two simultaneous channels of communications – speech, fax, or data ii. Higher data speed – 64 KBPS or 128 KBPS (with 2 B channels in use)

iii. Lower noise iv. Lower call set up times v. A single BRI can carry two simultaneous voice or data conversations (to the

same or different locations). vi. Added facilities like caller line indication, dialing direct to sub-addresses,

etc.. vii. Video conferencing

The advent of ADSL has taken away the advantages enumerated in i, ii. Further the technology advances in POTS switches has taken away the advantages enumerated in vi above. In view of this the popularity of ISDN has been on the wane. Over and above this, ISDN has been put to some incorrect uses like backing up or topping up leased lines. In both these applications, the router port is continuously connected to the ISDN lines which forms a part of the Global ISDN network which is a subset of the Global PSTN network. In these applications the ISDN lines automatically dial and set up connections in case of leased line failure or to cater to additional data load, and again disconnect when the leased line connection is restored in case of failure or when the additional load disappears. When the ISDN lines are not being used, they me be connected from the outside from other ISDN nodes in the Global ISDN networks. This is according the principle of all circuit switched networks. Thus if the number of any of the back up ISDN lines are known, any one can dial into this and get into and get into the leased line network. Although many SIs round the world have practiced this kind of connection and some of the leading manufacturers have products to meet this requirement or have been driving this practice because they have the products, this is an extremely dangerous practice and leaves your network totally exposed to the public domain networks. This practice should be done away with totally. Figure 1 shows the danger of external intrusion through the back up or top up ISDN ports on the router. For any real-time communications like speech, fax, interactive video (conferencing) the ideal communication link is a synchronous link. This is provided by circuit switched connections. ISDN’s advantage over ADSL or other broadband services is that it is circuit switched and provides synchronous communications ideally suited to real time communications. Since the connection is digital end-to-end, it is also noise free and of high fidelity. These features of ISDN can resurrect its popularity through the following uses.

A. It is still commonly used in recording studios, when a voice-over actor is in one studio, but the director and producer are in a studio at another location.

ISDN is used because of its "guaranteed" real-time, not-over-the-Internet service, and its superior audio fidelity as compared to POTS service.

B. A few companies make video conference call equipment that combine three

BRI lines and six 64K channels to create a good quality picture.

C. The quality described in v above may be used to facilitate various answering and information services

Whenever a multi-locational organisation wants to set up a video conferencing facility this should be done over public ISDN network using the facility described in B above. This will not only help them to have video conferences with their own locations, but also with their vendors, customers, business partners. Video conferencing is most required when teleconferences and meetings and are being done with company outsiders. For this the public domain ISDN network is ideal. Video-conferencing facilities should never be set up over point-to-point leased line networks which are used for either pure data or integrated networks for a company’s internal communication requirement and 100% secure WAN computing. This unnecessarily increases the bandwidth requirement, causes idle bandwidth when video conferencing is not in use, and increases the fixed annual operating costs of such networks.

VPN NETWORK

ISDN NETWORK

ISDN NETWORK

PSTN

PRESENT CONNECTIONCOMPLETELY EXPOSES YOUR DATA BASES TOPUBLIC DOMAIN NETWORKS LIKE ISDN & PSTN

Fig 1

VPN NETWORK

ISDN NETWORK

ISDN NETWORK

PSTN

PRESENT CONNECTIONCOMPLETELY EXPOSES YOUR DATA BASES TOPUBLIC DOMAIN NETWORKS LIKE ISDN & PSTN

Fig 1