Ch 6: Data Communications

Q1: What is a computer network?

A computer network is a collection of computers that communicate with each other over transmission lines or wireless. There are three basic types of networks: local area networks, wide area networks, and internets.

Local Area Network (LAN): connects computers that reside in a single geographic location on the premises of the company that operates the LAN.

Wide area networks (WANs): connect computers at different geographic locations.

Internet: an internet is a network of networks; it connects LANs, WANs, and other internets.

Q2: What are the components of a LAN?

All hardware connects through a switch, which is a special-purpose computer that receives and transmits messages on the LAN.  Each device on a LAN has a hardware component called a network interface card (NIC) that connects the device’s circuitry to the cable. Each NIC has an identifier, the MAC (media access control) address. Nowadays, almost every computer has an onboard NIC. All devices on a LAN are connected with a unshielded twisted pair (UTP) cable but if they carry a lot of traffic or are far apart then optical fiber cables are used. All devices on the LAN must use the same protocol such as IEEE 802.3, Ethernet, 10/100/1000 Ethernet, etc.

Q3: What are the alternatives for a WAN?

Digital subscriber line (DSL) modems operate on the same lines as telephones but they operate so that their signals don’t interfere.

Cable modems provide high-speed data transmission using cable television lines.

A third alternative is WAN wireless connection such as EVDO from Sprint and Verizon, or AT&T’s HSDPA.

Another choice is to create a network of leased lines between company sites.

Q4: Why do organizations use virtual private networks?

A virtual private network (VPN) uses the internet to create the appearance of private point-to-point connections. VPN offers the benefit of point-to-point leased lines, and they enable remote access, both by employees and by any others who have been registered with the server.

Q5: How does encryption work?

Encryption is the process of transforming clear text into coded, unintelligible text for secure storage or communication.

Q6: What is the purpose of a firewall?

A firewall is a computing device that prevents unauthorized network access. A perimeter firewall sits outside the organizational network and it’s the first device that the internet encounters. In addition to the perimeter firewall, some organizations implement internal firewalls inside its network. It protects all of the organizations computers and its LAN.  A packet-filtering firewall examines each part of a message and determines whether to let that part pass. A firewall has an access control list (ACL) which encodes the rules stating which addresses are to be allowed and which are to be prohibited.

Q7: 2020?

Higher regulations and fees will be applied to internet usage in the future. Sales tax will be applied as well. At the moment, businesses are required to pay sales tax on purchases made over the internet from out of state, but few actually pay. Besides that, systems will also provide presence, which means that you’ll know who is on your system, who is available to the system, and who cannot currently be reached by the system.

  Kroenke, David. "Chapter 6: Data Communication." Using MIS. Upper Saddle River, NJ: Prentice Hall, 2011. 174-193. Print.