Worksheet 10.2.5: Types of Network

1. A connected system of objects or people.
2. It has two or more devices that are linked fot the purpose of sharing information, resources, or both.

3. LAN:

   Can connect many computers in a relatively small geographical area, using shared media.

   WAN:

   Uses point-to-point links to communicate over large distances.

   Circuit Switched Network:

   A connection is maintained for the whole duration of the communication. The whole comunication is via the same route.

   Packet Switched Network:

   Each packet in the communication can take a different route to the destination.

   Client/Server Network:

   Network services are located in a dedicated computer whose only function is to respond to the requests of clients.

   Peer to Peer:

   Computers act as equal pertners to each other. The roles of requester and responder can be reversed.

   Hybrid Network:

   The hybrid topology combines more than one type of topology.

4. Media Access Control (MAC)
5. Channel Service Unit/Digital Service Unit; used to connect to an external digital communication circuit such as T1 (E1).
6. simplex, half duplex, full duplex

Worksheet 10.4.2: Network Topology

1. Physical topology describes the layout of the wires, while logical topology is the path that signals travel from one point to another.

2. Bus:

   All the devices on a bus topology are connected to the same cable.

   Star:

   There is a central connection point such as a hub, switch, or router where all the cabling segments meet.

   Extended Star:

   Includes an additional networking device that is connected to the main networking device.

   Ring:

   Hosts are connected in the form of a ring with no beginning or end.

   Mesh:

   This connects all devices to all others for redundancy and fault tolerance.

   Hybrid:

   Combines more than one type of topology.

3. The means by which signals (data) are sent from one computer to another, eg coax, UTP, fibre, etc.
4. The overall structure of a computer or communication system. It determines the capabilities and limitations of the system.
5. To ensure that only one token is out on the network at a time.

Worksheet 10.6.5: OSI Model, TCP/IP, Protocols

1. Open System Interconnection
2. A message begins at the top of the application layer and moves down the OSI layers to the bottom physical layer. Email would be an example of an application.

3. Application:

   Provides network services to application processes (eg Email, ftp, telnet).

   Presentation:

   Ensures that data is readable by the receiving system. Deals with data representation.

   Session:

   Establishes, manages, and terminates sessions between applications.

   Transport:

   Handles information flow control, fault detection and recovery, and data transport reliability.

   Network:

   Provides connectivity and path selection between two end systems.

   Data Link:

   Provides the reliable transfer of data across media using physical addressing and the network topology.

   Physical:

   Consists of voltages, wires, and connectors.

4. A contolled sequence of messages that are exchanged between two or more systems to acomplish a given task. Protocol specifications define this sequence together with the format of the messages that are exchanged
5. To be a set of public standards that specify how packets of information are exchanged between computers over one or more networks
6. It is 4 layers rather than 7.
7. Provide services to application programs, eg HTTP, Telnet, FTP, SMTP, DNS.
8. Provide end-to-end management of the communication session, eg TCP, UDP.
9. Provides internetworking for the comminication session, eg IP, ICMP, RIP, ARP.

Worksheet 10.8.7: Connecting to the Internet

1. In synchronous communication, timing information is encoded with the data. In asynchronous communication, regular start/stop bits are required to resynchronise data.
2. An electronic device that is used for computer communication through telephones. Converts digital to analog tones for transmission and analog tones to digital on reception. Hence MOdulate/DEModulate.
3. expansion cards, PCMCIA cards, external, built-in
4. dialing, data exchange, answering
5. Modem control commands. The AT command set is to issue dial, hangup, reset, and other instructions to the modem.
6. Internet Service Provider. They enable long-distance access to network services for information and device sharing.
7. Very high speed Backbone Network Service. Connects 5 supercomputer networks across the USA.
8. DSL uses normal telephone lines whereas a cable modem connects to a cable TV service