Computer Networks

Networking

The generic term node or host refers to any device on a network. A file server is a computer that stores and manages files for multiple users on a network. A web server is an application dedicated to responding to requests for web pages from web browsers on client machines.

Types of Networks

Local area network - LAN

A network that connects a relatively small number of machines in a relatively close geographical area. Various configurations are used to administrate LANs (called topologies)

  • Ring - A configuration that connects all nodes in a closed loop on which messages travel in one direction
  • Star - A configuration that centers around one node to which all others are connected and through which all messages are sent
  • Bus - All nodes are connected to a single communication line that carries messages in both directions

Wide area network - WAN

A network that connected two or more local area networks over a potentially large geographical distance. Often one particular node on a LAN is set up to serve as a gateway to handle communications going between that particular LAN and other networks.

Internet Connections

Internet backbone - A set of high speed networks that carry Internet traffic. These are provided by large companies such as AT&T.
Internet server provider (ISP) - A company that provides other companies or individuals with access to the Internet

Protocols

CSMA/CD

Used in Ethernet. The protocol does not work with radio.
The process is as follows:

  1. Listen to channel
  2. If idle then transmit
    • Else wait until the channel is idle, then transmit
  3. During transmission, listen in on transmission for collisions
    • If a collision is detected, then stop transmitting
    • Jam signal
    • Wait random amount of time
    • Restart from beginning

CSMA/CA

Used in WiFi. The process is as follows:

  1. Listen to channel
  2. If idle
    1. Wait short time
    2. If still idle then start transmission
  3. Else
    1. Wait until end of other transmission
    2. Wait random time
    3. Go to step 1

The hidden terminal problem

When end systems cannot hear each other, but can each communicate with a single AP.

Combining Networks

Device Description
 Repeater Repeats everything regardless of the destination
 Bridge Allows for some control and efficiency, as a signal is only repeated to the other side if the desination is on the other side
 Switch  Similar to a bridge, but can connect many networks together

Inter-process Communication

Client-Server

One continuously executing server serves many clients, whom initiate the communication.

Peer-to-peer (P2P)

Two processes communicating as equals on a one-to-one basis. Peer process are usually short lived.


Revision #3
Created Mon, May 15, 2017 4:17 PM by Christopher Wilkinson
Updated Mon, May 15, 2017 6:07 PM by Christopher Wilkinson