Press Release

February 2005 – 01

Going IP – Like It Or Not

In the UK BT are rolling out an IP Core for all traffic – but how will they support Legacy Systems?

The all-IP 21st century network

At a recent BT Seminar, the company announced its vision for the 21st Century as being an all-IP second generation network, which will replace both the existing telephone and data networks. A small number of switching centres would replace the existing infrastructure and result in massive cost reductions for BT.

What about non-IP data traffic?

While a large proportion of the world has gone IP, there are still a number of legacy networks, which don't suit IP, which require digital services such as those provided by BT's Kilostream or Megastream. This article explores a few options for connecting those systems when the option to purchase 'time' on the SDH backbone has become a thing of the past.

What do we class as a legacy system?

Typical legacy systems use technologies such as frame relay, X.25, SDLC, and statistical multiplexing, and while they maybe a few years old, these systems still provide reliable and efficient service to their organisations.

One might sensibly argue that organisations still running legacy systems will over time have good reason to move to IP, but there are a lot of situations where IP is not appropriate, or suitable. We have seen legacy equipment replaced by IP, only to see the IP system removed and the legacy equipment re installed some six months later.

How will we support the legacy systems?

For those of you still running a legacy network, you may wonder how your system will be supported once your no longer able to purchase digital services. This short article provides an insight into three ways different vendors have tackled the problem of legacy over IP.

TDM over IP

Over the last two years we have seen a few vendors, working on 'TDM over IP' products, with somewhat varied results. The establishment of a Timeslot Over IP is 'best endeavours' and typically a 2Mbps E1 emulated circuit takes around 2.3Mbps, and relies on guaranteeing a reliable Quality of Service. Maintaining a synchronise timing source between the end points with an IP core is quite an achievement. Most products don't go below 64Kbps, meaning anyone with really low speed 19.2Kbps transmission rates has to waste a significant amount of bandwidth.

Companies such as RAD, Germany's Pandatel and UK manufacturers Case Communications provide TDM over IP products.

X.25 over TCP/IP – XOT

Cisco systems addressed the problem for X.25 customers some time ago by implementing X25 Over TCP/IP (XOT), transporting X.25 over the IP network at the TCP layer. XOT has been said by some to be relatively complex to implement and designed for lower speed working, but it also provides enhanced functionality such as pad services. However XOT is designed for X.25 transport and not for frame relay or statistical muxes.

TCP tunnelling

As one of the UK leading communications manufacturers, Case Communications still continue to support a large number of customers with legacy systems both in the UK and internationally.

Back in the late 1980's Case advertised their products with the slogan 'future proof' and now the challenge arises of how to get customers running statistical multiplexers, frame relay and X.25 operating over an IP network.

Case have been very active in developing the next generation routers, based on industry standard hardware and open source software. These products provide very high levels of performance, and a wide range of plug-in modules, making them extremely flexible, and adhering to the age old Case slogan of 'future proof' technology.

It therefore seemed natural for Case Communications to develop an HDLC transport card, which would plug into their routers, (or other vendors' products) and transport HDLC over IP.

The Case card lifts the data stream out of the HDLC frame and encapsulates it in IP, before transmitting the data at the TCP level; the card removes the flags and the CRC checksums, and regenerates them at the remote end of the link, making the product highly efficient.

Configuration is extremely simple, you simplify specify the local port speed and physical interface, and then configure the remote IP address, physical port and data rate.

The Case product can connect to existing LANS' routers or utilise a broadband connection to provide the route to the remote end, no need for those expensive digital services anymore.

Replacing digital circuits with IP produces massive cost savings

Case Communications marketing manager Jan Corbett explains: "If you imagine the cost of a 64Kbps or 128Kbps digital circuit between London and Manchester, and then replace that with a 'broadband' connection at each end, which in total costs less than £50 per month, you can see the cost savings are huge." Corbett goes on to explain "With the Case product the only things that are required are a fixed IP address at one end of the link and ideally a guaranteed QoS. With our product users can run their existing legacy systems down the same link as their normal everyday data, in fact we can connect our system into their existing LAN and just look like another application."

Summary

While this article has not focused on broadband to any extent, it will be the key to reducing the costs of transporting legacy systems over IP. If the UK manages to catch up with some of their overseas competitors and starts to install more advanced broadband such as G.SHDSL Bis, V.SHDSL or ADSL 2 Plus, we could see customers enjoying their own transparent high-speed pipes for a few pounds per month.

An article based on this press release appeared in the February 2005 edition of Networking Plus.