IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
____________________________________________________________________ .........................................
advanced in order to meet increasing technological demands. This led to
the development of the Fast Ethernet with a transmission rate of 100
Mbit/s. Presently, this rate is sufficient for most networks in the backbone
area, and is also advantageous in that the already established CSMA/CD
technology can continue to be used. In this case however, the active
network components generally need to be replaced or adapted;
furthermore, the cabling needs to be checked for compatibility with Fast
Ethernet.
- Gigabit Ethernet
As Fast Ethernet proved extremely successful following its introduction, a
demand for an even faster Ethernet-based backbone technology was
voiced. This led to the founding of the Gigabit Ethernet Alliance (GEA) by
several renowned manufacturers, who wanted to achieve a transmission
rate of 1 Gbit/s. The standardisation phase is to be completed soon in
cooperation with the IEEE. With the help of features such as a protocol
extension (Resource Reservation Protocol, RSVP) for time-critical
transmissions (e.g. in the multimedia sector), the new standard is intended
to provide dedicated bandwidths in Gigabit Ethernet systems. The aim of
this is to supply attributes similar to those applicable to ATM, such as
Quality of Service (QoS). However, as the final standard has not been
approved yet, this variant should not be selected, in order to avoid the use
of an implementation which might still be incomplete.
Token-Ring
Token-Ring technology is defined in the IEEE 802.5 standard and is based on
the token passing technique. With this technique, a special data packet (token)
travelling on a circular path is used to determine which station may use the
transmission medium. When a station receives the token, it occupies the
medium and then forwards the token to the next station. This ensures that the
medium is only occupied by one station at a time.
In contrast to Ethernet, this deterministic technique prevents stations from
having to wait for indefinite periods of time on the occurrence of high network
loads before being able to transmit data. Token-Ring makes it possible to
firmly specify the maximum waiting period.
A Token-Ring network is usually configured as a physical double-ring, which
considerably increases the availability of the network, because, in the event of
a failure of a station or an interruption of one of the rings, the faulty point can
be bridged by using the other ring.
Token-Ring allows a transmission rate of 4 or 16 Mbit/s, so that for most local
networks, its use as a backbone technology is no longer recommended either.
The available bandwidth is too narrow. In the middle of September 1997, a
"High Speed Token Ring Alliance" (HSTR) was founded by several renowned
manufacturers to achieve transmission rates of 100 Mbit/s and, at a later stage,
1 Gbit/s. For this purpose, the IEEE 802.5 standard is to be extended by the
middle of 1998. As this variant is still being developed, its use is not
recommended at present.
____________________________________________________________________ .........................................
IT-Baseline Protection Manual: Oktober 2000