TEN-34 - Implementing the Network
by Michael H. Behringer
For the first time in Europe,
the TEN-34 project has provided a pan- European high-speed network for
European researchers. To achieve this it was necessary to integrate diverse
technologies such as conventional leased lines and ATM circuits. Due to
the lack of available technical options the implementation had to work
around many non-technical obstacles. The outcome, however, is a smooth
and transparent IP service.
When the planning for the TEN-34 network started in 1995, the technical
options for high-speed international connectivity were limited: the telecom
operators for a number of countries did not offer 34 Mbit/s lines, some
only offered these and no ATM. Thus a hybrid solution of leased lines and
ATM circuits was inevitable to achieve full European coverage. The challenge
from the technical point of view was to get international ATM circuits
operational which was new ground for telecom operators at the time
- and to integrate these with traditional leased lines. From the beginning,
it was obvious that the network would consist of two parts: a mainly ATM
based part between France, the UK, Germany and Italy (called FUDI), and
a 34 Mbit/s leased line network between the Netherlands, Sweden, the UK,
Germany, Switzerland and Spain (Unisource). Other countries are connected
as shown in the figure.
The TEN-34 Topology.
The Unisource side consists of a network based on 34 Mbit/s leased lines.
The service is managed on the IP level by Unisource. A migration of the
core network to a full mesh of ATM circuits is being carried out at the
moment. Unisource provides a full IP service, to which commercial customers
also connect, and which provides connectivity to other European networks
such as Ebone.
On the FUDI side the telecom operators provide mostly ATM circuits,
and one 34 Mbit/s leased line. The ATM services in use are continuous bit
rate (CBR) and variable bit rate (VBR). The choice between the two was
mainly based on price. As only circuits and no IP services are provided,
TEN-34 provides routers to interconnect these, and to provide an IP service
over the infrastructure. The TEN-34 routers also interconnect the two sub-networks
in the UK, Germany and Switzerland. A Network Operations Centre (NOC) for
TEN-34 was established in London.
The national research networks (NRNs) have a uniform interface towards
TEN-34 on both sub-networks. Speed limitation to a specified bandwidth
was established on the access lines with ATM to ensure balance between
the NRNs. Overall, the NRNs are presented on their access point with a
transparent IP service, which hides the different implementation details.
Connectivity to the US is currently implemented independently from TEN-34
in most countries, but a 34 Mbit/s line from Frankfurt is planned for those
countries that do not have their own US line. On the US side it will connect
to two European points of presence (PoPs), and from there connections to
various US networks will be established. The line to the US will be implemented
as a clear 34 Mbit/s line without ATM. The line between the two European
routers in the US will be a clear 45 Mbit/s.
One technical problem with IP networks of this size is the provision
of traffic statistics. Routers are generally not able to use traditional
accounting methods that do not involve additional hardware. However, new
accounting methods have been developed recently. On the TEN-34 network,
accounting will be based on so-called 'net flow' statistics, which require
a workstation close to the router, so that the vast amount of accounting
data can be processed there. The workstations needed for this are currently
being procured across Europe. From these data the NOC will provide statistical
information for network planning and usage reports.
Originally it was also planned to provide direct access via ATM to the
NRNs, so that NRNs can establish virtual private internetworks. This would
involve ATM switches being deployed in all participating TEN-34 PoPs to
make use of this service. Given the short lifetime of the TEN-34 network
(up till July 1998), it is currently unclear whether the additional expenses
for the switches will indeed be incurred.
The first parts of TEN-34 became operational in March 1997. The first
four months presented a smooth IP service with few problems, despite the
introduction of new technologies and the diversity of technologies employed.
There were a number of line faults on both the ATM parts and the leased
lines but, as the majority of the network is designed to be resilient,
users did not notice major outages. The traffic has been increasing significantly
since the beginning, but the network is still not loaded. For the first
time in Europe, TEN-34 has shown that ATM circuits and leased lines can
co-exist in a IP network and that the resulting service can be presented
to the users as a uniform network.
DANTE, UK, is coordinating partner in the TEN-34 Consortium.: For further
information, see: http://www.dante.net/ten-34
Please contact:
Michael Behringer - DANTE
Tel: +44 1223 302992
E-mail: Michael.Behringer@dante.org.uk
