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ISDN

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In this 'Viewpoint' we take a look at the world of ISDN and the role that the Transition Networks PacketBand, Liberator, Brent & Databand products, available from Lanode, are playing in addressing many of the common challenges faced by organisations across many different market sectors.

Integrated Services for Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide. It offers circuit-switched connections (for either voice or data), and packet-switched connections for data, in increments of 64 kilobit/s. A major market application for ISDN in some countries is Internet access, where ISDN typically provides a maximum of 128 kbit/s in both upstream and downstream directions. Channel bonding can achieve a greater data rate; typically the ISDN B-channels of three or four BRIs (six to eight 64 kbit/s channels) are bonded.

There are currently over 20 million ISDN Basic Rate lines and 2 million Primary Rate circuits in use in the world. There are also 56 million narrowband leased lines. And they won't be going away any time soon. Tried and trusted secure applications and terminals which encrypt services such as voice, fax and video nearly always expect to be presented with synchronous, switched connection-oriented communications services.

In the government and military sectors, much as everywhere else, there is an ever increasing push to migrate towards a single, packet-based communications infrastructure. This so-called Next Generation Network (NGN) is based on Ethernet, IP and Multi-Protocol Label Switching (MPLS) infrastructures. One of its biggest benefits is to bring together or converge equipment and applications - email, voice, data, video - on to a single network for the first time, thus greatly reducing costs and increasing manageability. But, it is not an ideal solution for all applications and traffic types.

Organisations which must place security high on their list of priorities are therefore presented with a dilemma. While wanting to stay at the forefront of network technology and maintaining or improving connectivity options, security experts are nervous that a move to IP-based secure systems will expose new constraints for some critical or legacy services. Ideally, they would like to take advantage of the benefits of NGN, but migrate secure applications at a slower pace, when the right equipment becomes available and the current secure equipment has reached the end of its life.

The IP and MPLS–based NGN is the confirmed direction for the telecoms industry. However, while some carriers are planning for widespread adoption of packet infrastructure, not all users are. While the telecom industry focuses on the next wave of IP-based infrastructure and services, many users will be happy keeping their ISDN circuit switched based equipment and applications. Why? Because they work and because there is a large world outside of VoIP and router traffic. Some will want to hold on to tried and trusted equipment such as Group 4 facsimile, synchronous terminals, TDMs, video-conferencing equipment, secure voice terminals and PBXs. As an indication, how many of your existing or target IP customers still have ISDN and leased lines delivered to site? Customers will want or need to maintain their synchronous, circuit-switched services or find a way to support them over IP.

The broadcast industry who use ISDN codecs for high quality audio communications utilising traditional ISDN services from traditional carriers. Deployments can be permanent, temporary, remote or mobile. These organisations are now migrating to Packet Networks for voice/data applications, but to-date have been unable to support clear-channel ISDN working needed by the codecs because of clocking and synchronisation issues.

Consider if your organisation is in the process of migrating its network infrastructure to IP? This raises ISDN connectivity issues for your encryptors for voice/data and fax but do you want to reduce your legacy non-IP leased line costs and support infrastructure?

PacketBand ISDN over IP

With the increasing migration to Packet Networks, or where an ISDN service is not available or perhaps where the carrier is withdrawing ISDN BRIs, existing ISDN codecs can be still be operated using Transition Networks PacketBand ISDN over IP products which are available from Lanode. This technology turns the IP network into a virtual switched ISDN and, critically, locks all units to a common clock. Dynamically switched non-compressed clear ISDN ‘B’ channels are established, as needed, providing an ISDN link between PacketBands and the connected codecs. Utilising the IP network can also offer a cost advantage over the traditional ISDN services particularly when operating internationally. Packet networks are available globally through both terrestrial and satellite services, and can support the PacketBand technology and ISDN codecs. PacketBand responds to an out-going audio ISDN call by immediately connecting to the appropriate PacketBand across the Packet Network. Codecs are connected through the PacketBands unit via their ISDN Basic Rate port (BRI port).

The PacketBand-ISDN range offers users the ability to turn an IP or Ethernet network into a virtual ISDN network, placing and clearing calls dynamically across the IP network or “breaking-out” into a real ISDN carrier service. PacketBand uses IP/MPLS networks to deliver “Pseudo-Wires” of clear switched ISDN 64kbps “B” channels. Ideal for applications needing non-compressible data, enabling them to benefit from the commercial advantages of IP networks. Where quality is of concern, PacketBand is also perfect for non-compressed voice, enabling a smooth migration to VoIP technologies for both voice and data. All products within the PacketBand range interface to Ethernet and IP/MPLS networks with support, subject to the usual constraints, for the Public Internet. All have local Ethernet ports with rate limiting and control mechanisms. All support various protocols with timing, jitter and clocking options.

Liberator

A very flexible product, not easily “pigeon-holed” to an application or specific market. Designed as a flexible ISDN cross-connect mux, conversion, simulation and routing unit. Liberator has been deployed into many different applications and countries. Liberator is currently used for:

  • sharing ISDN network access between multiple local devices;
  • delivering fractional PRIs from network BRIs;
  • as an enabling tool for VoIP migration;
  • as a least cost router;
  • as a fall-back system;
  • delivering ISDN economically to multi-tenant buildings;
  • international “break-out” for data ISDN services;
  • number conversion tool.

If you need to switch or convert between BRI, PRI, E1 or T1, have a number conversion or translation requirement, need to route to different ports on any number of criteria then Liberator will most probably be able to help.

Brent Converter

Designed specifically for the Brent encryptor, the Converter performs many roles;converting between ANSI and ETSI BRIs;

  • the ability to manipulate Information Elements to assist when connecting to various ISDN services;
  • converting PRIs (perhaps from video MCUs etc) into BRIs for Brents;
  • a configurable delay in passing “Connect” message to the DTEs whist the key exchange is taking place;
  • and ensuring the second and same dialled DDI number on the PRI is routed to the same Brent.

ISDN secure phones, including The Brent, Brent 2, STU3 and TSC2000 offer high-security communications utilising traditional ISDN service provided by a carrier. Deployments can be permanent, temporary, remote or mobile. However many organisations are now migrating to Packet and IP based networks which do not support clear channel ISDN working, or they need secure access where ISDN is unavailable. It is into this environment that we can offer a range of connectivity solutions using the PacketBand “ISDN over IP” range which can solve many of these migration and access dilemmas. PacketBands are COTS products that provide easy and flexible secure phone connectivity to both traditional ISDN network infrastructures but also to, across and through the new managed packet networks. Any other ISDN devices such as secure faxes, encryptors, high quality audio codecs and video-conferencing stations can also be connected.

Databand – Inverse Multiplexers

The Databand range is based upon a core aggregation or bonding technology, dialling and establishing multiple ISDN “B” channels into a single cohesive N*64kbps virtual leased line. The leased line backup products monitor different types of circuits and establish a backup path using multiple ISDN channels. This normally happens so quickly and reliably that end-users are unaware there has been any break in service or network problem. Ideal for critical applications and for carriers needing to provide Service Level Agreements (SLAs).

The DataBand CSI and ISU range connect high speed serial data devices together using multiple ISDN calls, in effect dialling a high-speed “leased line” between non-ISDN devices. It is ideal for use with video-conference units, MCUs, encryptors (such as KIVs) or any high-speed serial device that needs bandwidth on demand. It aggregates or inverse multiplexes multiple ISDN channels from multiple ISDN PRI interfaces into N*64kbps V.35, RS530, X.21/V.11 and E1 ports.

So who else would use PacketBand ISDN?

  • IP-based Carriers who have no method of delivering ISDN and/leased lines to customers. Additionally, Carriers who want to utilise their national or international IP network for local “break-out” to retain revenue.
  • Carriers with traditional circuit switched or TDM architecture seeking to migrate customers and products to an IP network.
  • Corporate users who want cost reductions for ISDN calls and synchronous traffic.
  • Applications where voice quality is critical. Whilst one of the main drivers for the trend towards IP is low-cost voice over IP (VoIP), some applications cannot support the degradation in voice quality associated with VoIP systems because of the compression methods and/or delays. Examples could be dealer-desk and emergency calls. Traffic that originates from mobile telephones already suffers from reductions in quality and further reductions using VoIP can compound the problem.
  • Government and Military for secure data, voice and fax transmissions.
  • System Integrators allowing provision of a more complete customer solution.
  • IP Equipment Vendors adding and “rounding” their product offering.

ISDN BRI Fibre Optic Modem

To complete the family we've also developed the FRM2-BRI/ST2 which is an ISDN over fibre modem that enables basic rate ISDN interfaces to be extended over multi-mode fibre optic cabling. The units are ideal for sensitive data applications that require the use of fibre and have been designed to transport a single ISDN Bri interface over multi-mode fibre optic cabling.

Summary

ISDN connectivity issues remain high on the networking agenda alongside optimising the existing legacy infrastructure investment, and this cuts across all organisations spanning multiple sectors. Being able to fully utilise existing technology and expand its life expectancy as well as capitalising on new technologies is a challenge for all organisations and we can help.

The PacketBand-ISDN range is unique. It delivers clear/transparent switched ISDN “B” channels across packet networks so any type of traffic can be transported, including: video-conferencing, encryptors, codecs, faxes, modems and of course voice. In addition to providing ISDN over IP access, PacketBand also performs a wide range of useful switching and routing functions. These include the ability to convert dialled numbers, to add or change CLIs and to route calls to a variety of destinations depending on a number of criteria with Primary, Secondary and Tertiary alternate paths. These functions are also available in the Liberator, an ISDN PRI/BRI conversion and routing product with a wide range of applications and uses.

Source: This article has been compiled using original source content from, and used with the kind permission of, Transition Networks Europe.