Transcript Computer Networking - missions

Principles of computer Networking
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Computer Network
What is a network ?
A network is a collection of computers and devices
connected to each other.
The network allows computers to communicate with each
other and share resources and information
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Computer network
When a network is needed ?
When you want to share resources or exchange data or
mutualize an internet connection
Example of resources :
- Printer
- Hard Disk (external or internal)
- Scanner
- Internet connection
- …
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Computer network
What makes up a network?
A network typically includes 4 things (besides the computers
themselves):
 Network interface cards (NICs):
• cards that plugs into the back (or side) of your computers and lets
them send and receive messages from other computers
 Cable:
• the medium to connect all of the computers together
 Hub/Switch/Router:
• hardware to perform traffic control
 Protocol:
• a set of communication rules to make sure that everyone speaks the
same language
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Protocol : TCP/IP
What does it mean ?
TCP Transmission Control Protocol et IP Internet Protocol
Computers are like humans beings in that they need to speak the same
language in order to communicate.
Each computer needs to be identified (with a unique "address")
It can be compare to the Post Service. They need your name, your address,
it must be an unique information to work.
IP address will be your unique id (name, first name,…)
The gateway will be the nearest Post Office
DNS server (Domain Name Server) will be able to translate the "Internet
name" (ex.:www.google.fr) into IP address (74.125.39.104)
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Protocol : TCP/IP
There is 2 ways to configure TCP/IP on computers.
Static :
You manage and enter manually the configuration
Dynamic (DHCP : Dynamic host configuration protocol) :
An automatic IP address will be given to your computer.
This can be done either by a "server" or more currently
by a router (ex.: Wi-Fi router)
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Protocol : TCP/IP
Example of static TCP/IP configuration :
Ip address : ex. : 172.16.2.114
Subnet Mask : 255.255.255.0
Default gateway : 172.16.2.205
DNS Server 1 : 172.16.2.212
DNS Server 2 : 172.16.2.208
Warning : Only items on same IP class
addresses can communicate.
Ex.: 172.16.2.114 (subnet mask
255.255.255.0) will see 172.16.2.2
Ex.: 172.16.2.114 (subnet mask
255.255.255.0) won't see 172.16.40.2
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Computer Networking
Advantages of Installing a Network
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Speed. Networks provide a very rapid method for sharing and transferring files. Without a network, files are shared by
copying them to flash disks, then carrying or sending the disks from one computer to another.
Cost. Because of sharing resources such as printer, scanner,...you don't have to buy many items.
Resource Sharing. Sharing resources is another area in which a network exceeds stand-alone computers. Most of
missions cannot afford enough laser printers, modems, scanners, … for each computer. However, if these or similar
peripherals are added to a network, they can be shared by many users.
Flexible Access / Workgroup Computing. Mission networks allow users to access their files from every computers.
Users can also work cooperatively through the network.
Drawbacks of Installing a Network
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Expensive to Install. Although a network will generally save money over time, the initial costs of installation can be
prohibitive. Cables, network cards and the installation may require the services of a technician.
Requires Administrative Time. Proper maintenance of a network requires considerable time and expertise.
File Server May Fail. Although a file server is no more susceptible to failure than any other computer, when the files
server "goes down," the entire network may come to a halt.
Security. In case of "Workgroup" network, files are accessible to every body. RUser right access can only be
implemented on Domain Network. But it requires to much knowledge and means.
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Cable Network
Installing Cable - Some Guidelines
When running cable, it is best to follow a few simple rules:
 Always use more cable than you need. Leave plenty of slack.
 Test every part of a network as you install it. Even if it is brand
new, it may have problems that will be difficult to isolate later.
 Stay at least 1 meter away from fluorescent light boxes and
other sources of electrical interference.
 If it is necessary to run cable across the floor, cover the cable
with cable protectors.
 Label both ends of each cable.
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Wireless Network
The term Wi-Fi often is used by the public as a synonym for wireless
Internet (WLAN)
A wireless access point (WAP) connects a group of wireless devices to an
adjacent wired LAN
Wireless adapters allow devices to connect to a wireless network
A wireless router allows wired and wireless ethernet LAN devices to connect
to a (usually) single WAN device such as cable modem or DSL modem
Wired Equivalent Privacy (WEP) encryption was designed to protect against
casual snooping, but is now considered completely broken.
Wired Protected Access (WPA) which uses TKIP as a stopgap solution for
legacy equipment. Though more secure than WEP, it has outlived its
designed lifetime.
WPA2 encryption standards were released. If used with a 802.1X server or in
pre-shared key mode with a strong and uncommon passphrase WPA2 is
still considered secure, as of 2009.
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Wireless Network
Installing Wireless Network - Some Guidelines
Follow a few simple rules:
 Always protect your Wi-Fi access by a WPA encryption at
least. Don't forget to protect the admin access.
 Renew frequently the password.
 Be aware that's the internet flow will be the same. It will be
divided by the number of users.
 Implement some wired connection in case of problem with
the Wi-Fi
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Glossary
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Local Area Network
A Local Area Network (LAN) is a network that is confined to a relatively small area (capital, base, Paris HQ,…)
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Wide Area Network
Wide Area Networks (WANs) connect larger geographic areas, such as Liberia, the Africa, or the world
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Switch
A switch is a device that provides a central connection point for cables from workstations, servers, and peripherals
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Router
A router translates information from one network to another
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Wireless LANs
Some networks are wireless. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between
the workstations and the file server or hubs.
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Wi-Fi
Wireless Fidelity synonym for wireless Internet (WLAN)
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Ethernet
Ethernet could be labeled as the great grand-father of all the other network types
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Internet
The collection of computers, networks and their interconnections that are more or less publically accessible.
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Intranet
An intranet is a private computer network that uses Internet technologies to securely share any part of an organization's information or
operational systems with its employees
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Extranet
An extranet can be viewed as part of a company's intranet that is extended to users outside the company (e.g.: normally over the
Internet).
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Fast Ethernet
It's a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original
Ethernet speed of 10 Mbit/s.
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Gigabit Ethernet
It's the next iteration, increasing the speed to 1000 Mbit/s
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