Frequently Asked Questions concerning MANs
1. About MANs
1.1 What is a MAN??
1.2 What are MANs for?
1.3 Are the MANs connected to the Internet?
1.4 Must I pay to use a MAN?
1.5 Who owns the MANs?
1.6 What other MANs are there?
2. Bandwidth
2.1 What does bandwidth mean?
2.2 Why does bandwidth matter?
2.3 How fast are the MANs?
2.4 How fast is 155 Mbps?
2.5 Have I got 155 Mbps to my desktop?
3. ATM
3.1 What does ATM mean?
3.2 What is the advantage of ATM?
1) About MANs
1.1) What is a MAN??
MAN stands for Metropolitan Area Network. A Metropolitan Area Network
is a very high bandwidth computer network which connects together a
significant number of sites in a city and its surroundings. Sites
connected probably include universities, research organisations,
businesses, and hospitals.
1.2) What are MANs for?
The MANs
provide Scotland's universities, colleges and research institutions with
a computer network that is second to none in the world. This means that
ordinary computer activities are easier to carry out - email, internet
access, file sharing all work fast and reliably. Internet facilities
can be used routinely during teaching, and other novel uses are being
investigated, including including use of workstation clusters for
parallel computing, an online version of a magazine with musical
examples, and many more. More information on how the MANs are being
used is available at the Projects section of
this website.
1.3) Are the MANs connected to the Internet?
Yes; academic users in Scotland can't avoid using the MANs every time
they connect to the Internet. The MANs are part of the Internet in
Scotland
1.4) Must I pay to use a MAN??
The MANs are free at point of use. There is some discussion about
charging for network use, or for particular network services, but at
present usage is free.
1.5) Who owns the MANs ?
A large
proportion of the funding for the MANs was provided by the Scottish
Higher Education Funding Council (SHEFC) together with the Joint Information Systems
Committee (JISC) and money
contributed by the the Higher Education
Institutions (HEIs). Some MANs are partly funded by
local businesses.
1.6) What other MANs are there?
Yes, there are MANs elsewhere in the UK. Only in Scotland is the
MAN technology pervasive however. Information on other MANs is
available at EaStMAN.
2. Bandwidth
2.1) What does bandwidth mean?
The bandwidth of a network is the speed at which data is transferred
through it. Bandwidth is usually expressed in Mega bits per second
(thousands of pieces of data transferred per second), written as
Mbps or Mbit/s.
2.2) Why does bandwidth matter?
A high bandwidth means that a single piece of data moves fast, which in
turn means that a lot more data can move down the wire in a given amount
of time. This explains why high bandwidth networks are spoken of in
terms of both speed and volume.
If large amounts of data can be transferred, this means that many people
can use the network without overloading it and this in turn means the
network will be RELIABLE. All sorts of uses become possible when people
know that the network will do what they want, when they want it.
2.3) How fast are the MANs?
The Scottish MANs operate at 155 Mbps. They are connected together by
the 'Scottish Cross-Connect', which also operates at 155 Mbps.
2.4) How fast is 155 Mbps?
A transatlantic network connection for the academic community from the
UK to the US was brought into service in June 1997, operating at 45
Mbps. Scotland has a 155 Mbps network which extends into every
campus.
2.5) Have I got 155 Mbps to my desktop?
Almost certainly not. The 155 Mbps is allocated to different purposes:
approximately 50 Mbps is for ordinary Internet use; about 50 Mbps is for
videoconferencing; and about 50 Mbps is available for research
purposes. Furthermore, most people are connected to a local ethernet,
not directly to the MAN.
2.6) My local ethernet operates at 10 Mbps; can I use the
MAN?
Yes, your local ethernet is connected to the MANs. 10 Mbps is a high
speed network, so long as not too many people are sharing it. The 155
Mbps network is shared by all users in Scotland; your 10 Mbps LAN only
has a few users on it. If you find network performance is poor, speak
to your local network administrator - your network might need splitting
up so that fewer people share the same subnet.
3. ATM
3.1) What does ATM mean?
ATM stands for Asynchronous Transfer Mode, one of the methods currently
available for transferring data across networks; the Scottish MANs are
based on an ATM network.
3.2) What is the advantage of ATM?
There are two main advantages:
1) ATM networks make a 'virtual connection' between origin and
destination computers, so that data cells are sent along a known path
from one computer to the other. When a connection is set up, it is
allocated a certain amount of bandwidth, and this means that the speed
at which data will be transferred across the network is known and will
not vary however busy the network becomes. This makes it possible to
use the network for applications such as high quality sound, where
breaks in the transmission would be unacceptable, or cluster computing
where different computers are connected together effectively forming a
bigger computer.
2) Different sorts of data can be carried on an ATM network: voice
signals and data signals can be carried.
