Networks

Computer Networks2/21/2013

Study Questions

Q1: What is a computer network?Q2: What are the components of a LAN?Q3: What are the alternatives for a WAN?Q4: How does encryption work?Q5: What is the purpose of a firewall?Q6: What is a VPN and why is it important?

Q1: What is a network?

• Network– Collection of computers – Communicate with one

another over transmission line

• Basic types of Network Topologies– Local Area Network (LAN)– Wide Area Network (WAN)– Internet

THE Internet

• Global network of networks• Connects LANs, WANs, and other networks• Public and private networks of networks• Uses layers of protocols

– HTTP = Hyper Text Transfer Protocol– TCP = Transmission Control Protocol– IP = Internet Protocol

Local Area Networks

• Computers connected on single company site

• Usually located in small area, such as a home, office building, or group of buildings

• Connects two to several hundred computers

Network Interface Card (NIC)

• Uses a protocol to talk with other devices on the network (IEEE).

• 10/100/1000 Ethernet Protocol.

• Wireless 802.11 (A, B, G, N) Protocol.

Wide Area Network

• Connects computers across multiple locations.

• Uses communication networks from vendors– Licensed by

government• Cloud computing

WAN Components

• WANs connect computers at separate sites– Use routers and public communications links between sites– Cable connections made through licensed public

telecommunications companies

• Internet service provider (ISP)– A company that provides customers access to the

Internet– Provides legitimate Internet address– Serves as gateway to Internet– Pay for Internet access

WiMax – Regional WiFi

• Mobility

• Overcomes infrastructure cost issues.

• WiMax Forum CertifiedTM systems to have capacity of 40 Mbps per channel, for fixed, nomadic, portable, and mobile applications

• Clearwire and Craig McCaw

Firewalls

• Prevents unauthorized network access.

• Organizations may have multiple firewalls.• Firebox (Perimeter ISP Firewall) • Network Firewall• Computer Firewall

Virtual Private Networks

• Use Encryption to create a secure “tunnel” extending a LAN.

• How does encryption work?– Process of transforming clear text into coded text– Uses an algorithm to “scramble” information and a key to

“unscramble”– Used for secure storage or communication

Virtual Private Networks