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ITGS
Network Architecture
ITGS
• Network architecture
– The way computers are logically organized on
a network, and the role each takes.
• Client/server network - One or more computers act
as servers that provide services to the rest of the
network (the clients)
– Many advantages because files are located on a server
can be accessed by owners from any client
» If a computer needs to be repaired, files are not
lost since they are saved on the server, not the
computer
» Because the server authenticates users, security
is improved
ITGS
• Thin client network - client computers rely
heavily on a server not only to store files and
applications, but run software on a client’s
behalf (sometimes including even the OS)
– The thin client merely acts as a terminal for
accepting input and displaying output
• The client only contains enough software to initialize the
hardware and network connection, and connect to the
server
• Because this is all they do, clients have very low
specifications
– No secondary storage
– Slow processors
– Small amount of RAM
ITGS
• Peer-to-peer networks - every client (peer)
has equal status, and there is no central
authority or server
– Common in homes and small businesses
where a server is too expensive/ not necessary
• Each computer shares the files from its own hard
disk, and other machines are able to access them
• With more than a few users, the lack of a server to
aid in security and storage becomes a problem
ITGS
• Firewalls
– Hardware or software that determines which data is
allowed to enter and leave a network
• Can be dedicated computers or built into network routers
– Firewalls help secure a computer by preventing
network access from unauthorized users
– They also control which users and programs are
allowed to connect to an external network such as the
Internet
• Firewalls can be configured to allow or block traffic using
several methods:
– IP addresses - IP addresses of specific computers can be
allowed or denied access
» Denial of Service (DoS) - an attack by malicious computer
users that bombards a site’s servers until the site doesn’t
work
» In one of these attacks, the IP addresses of the attacking
machines can be blocked
ITGS
•Domain names - access to particular websites such as social
networks can be blocked by specifying their name
•Protocols and ports - different protocols can be blocked or
allowed as needed:
•Web browsing (HTTP)
•Mail (SMTP and POP3)
•File transfer (FTP)
•These protocols use a standard port , and the ports can be
blocked as well
•For example, HTTP is port 80
•Application program - individual programs can be granted or
denied network access
•This is most important for programs that try automatically
to update themselves or update themselves
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• Controversy over firewalls
– While they can be used for protections, governments can
also use them to deny services
• Proxy servers
– Act as a middle step between two computers
• Usually between a computer on a LAN and a web server on the
internet
– All communication through the two computers passes
through the proxy
» The proxy caches, filters, and logs data (like users’ web
activity)
• Caching - (saves time and bandwidth)
– A process used to speed up activities like web browsing
» Proxy servers keep a copy of commonly requested
material, such as a web page, in a storage area called a
cache.
» When a user requests the webpage, the proxy server
provides it from the local cache rather than retrieving it
from the internet