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Networks

Telecommunications network is a network off telecommunications links and nodes arranged so that messages may be passed from one part of the network to another over multiple links and through various nodes.

What are messages? –Information

Networks are an indispensable part of modern society.

1. Commercial – e-commerce, banking, inventorying, telecommunications, archiving, health.

2. Social – critical infrastructure, homeland security, policing.

3. Human interaction/communication – e-mail, chat, videoconferencing, social networking, entertainment

Appears in every facet of engineering – Network every electronic device (computers, phones, sensors, planes, cars, TVs, appliances, heart monitors..)

Wider definition of a Network – A system that carries a commodity between two or more entities. E.g. Transportation network, electric grid, postal, water, telephone.

Computer Network – A system that carries information between two or more entities, in the form of electric signals.

Transportation vs Computer Networks

Transportation Network: Vehicles/ people, Street address, intersection, Street, highway, path Link/broadband/path, Traffic jam, Stop and go traffic light, Taking alternative path, Collision, HOV lane, Following a route to school

Computer Network: Packets/Payload, IP address, Bridge/router, Network congestion, flow control, Alternative route, Collision of packets, Flow priority, routing algorithm

Commonly known Networks

The Internet (The global network adopting the IP technology)

Ethernet (LAN)

WiFi

3G/4G

An internet** (Internet: A network of networks)

Main types of networks

Mobile Phone network, Satellite Network/Communications, Computer Networks

Mobi

Mobile phone Infrastructure networks, Downlink: tower to phones (forward), Uplink: phones to tower (reverse). Arranged into “cells” – Hence “Cell phones”

Cell towers – these typically have 3 sectors, each operates at a different frequency. Antennas are sectored, three 120 degree sectors, each use different frequency, don’t interfere

Cellular Backhaul - Connection between cell site and mobile telephone Switching Office (MTSO). Can be fibre, copper or wireless.

GSM Infrastructure – BTS = Base Transceiver Station

PCU = Packet Control Unit

BSC = Base Station Controller

SGSN = Serving GPRS Support Node

Gi = Gateway GPRS Support Node

MSC = Mobile Switching Centre

VLR = Visitor Location Register

PSTN = Public Switched Telephone Network

HLR = Home Location Register

Phones not designed to display web pages: New protocol developed – Wireless Application Protocol. Compresses version of HTTP, runs over UDP.

Third generation (3G) standards, Supports >1MBPS to handsets (144 kbps requirements)

IMT 2000 Internation Mobile Telecommunications 2000 is global standard

Satellite Networks – How it works – Uplink = Earth station sends a transmission to the satellite. The satellite transponder converts the signal and sends it down to the second earth station = Downlink.

Satellites are used by: FSS (Fixed Service Satellites) - point to point communication, BSS/ DBS (Broadcast Service Satellites/ Direct Broadcast Service - Satellite Television/Radio, MSS (Mobile Service Satellites – Mobile Phones.

GEO = Geostationary Earth Orbit. Above the Earths equator.

CSS = Cascading Style Sheet. This describes to the browser how items on the page should be displayed and look. E.g. h1 = border thin red solid, background pink.

Xml: Extensible MarkUp language similar to HTML. Focused on the structural organisation of the document –structure rich content.

JSON = JavaScript Object Notation is a lightweight data interchange format.

WEBSITES-

Client side: Java applets, JavaScript, Macromedia Flash.

Server Side: Common Gateway Interface, Servlets, PHP, ASP

Server will react to browser instruction and perform the task require (e.g. getting data from a database)

JavaScript, CSS etc. on browser outputs the data in a human readable visual format.

Traditional Internet Applications –

Domain mail server collects incoming mail and transmits outing mail (SMTP)

Mail server delivers collected incoming mail to clients via POP3 or IMAP.

File transfer protocol (FTP)

Telnet and SSH

More Recent Applications –

Voice over VoIP

Internet Radio N-unicast

Multicast

RIA = Rich Internet Application. Designed to deliver same features and functions normally associated with desktop applications.

Application Server: Is a server program in a computer in a distributed network that provides the business logic for an application program. It’s viewed as part of a three tier application:

GUI (Graphical User Interface) Server

An application (Business Logic) Server

A database and transaction server

A first tier, front end, web browser based graphical user interface, usually at a personal computer or workstation.

A middle tier business logic application or set of applications, possibly a on a local area network or intranet server.

A third tier, back end, database and transaction server, sometimes on a mainframe or large server.

E.g. Spotify.

Tags

The basic structure of an HTML document includes tags, which surround content and apply meaning to it.

Computer Network – A collection of computing devices that are connected in various ways in order to communicate and share resources.

Usually made through physical wires or cables. However some are wireless, using radio waves or infrared signals.

The generic term node or host refers to any device on a network.

Data transfer rate – the Speed which data is moved from one place on a network to another.

Data transfer rate is a key issue in computer networks

Computer networks have opened up an entire frontier in the world of computing called the client/ server model. On a request response basis.

File server = a computer that stores and manages files for multiple users on a network.

Web server = a computer dedicated to responding to requests (from the browser client) for web pages.

Local- area network (LAN) – A network that connects a relatively small number of machines in a relatively close geographical area. To administer LANs… there is:

Ring topology: A configuration that connects all nodes in a closed look on which messages travel in on direction. (Connected in the shape of a ring)

Star topology: A configuration that centres around one node to which all others are connected and through which all messages are sent. (Connected with one in the middle and multiple coming off it)

Bus topology: All nodes are connected to a single communication line that carries messages in both directions. (Connected in a line with ones coming off equally at each side)

Types of Networks: A bus technology called Ethernet has become the industry standard for local-area networks.

Wide-area Network (WAN) A network that connects two or more local-area networks over a potentially large geographic distance.

- Often one particular node on a LAN is set up to serve as a gateway to handle all communication going between that LAN and other networks.

- Communication between networks is called internetworking. The Internet, as we know it today is essentially the ultimate wide-area network, spanning the entire globe.

Metropolitan-area Network (MAN) the communication infrastructures that have been developed in and around large cities.

Local area network connected across a distance to create a wide area network.

Internet Connections:

Internet backbone. A set of high speed networks that carry Internet traffic. These networks are provided by companies such as AT&T, GTE, and IBM.

Internet service provider (ISP). A company that provides other companies or indivaiduals with access to the Internet.

Broadband- DSL and cable modems are broadband connections.

Network Classifications:

Scope

-Local area network (LAN)

-Metropolitan area (MAN)

-Wide area network (WAN)

Technology Ownership

-Closed (E.g. Netware) versus open (TCP/IP)

Topology (configuration)

-Bus (Ethernet)

-Star (Wireless networks with central Access Point.

Protocols

Protocols dealing with multiple access:

CSMA/CD (doesn’t work with radio)

-Used in Ethernet -Silent bus provides right to introduce new message

CSMA/CA

-Used in WiFi -Hidden terminal problem

Topologies and Ethernet

Ethernet Switch = 4 networks with a single PC on each one, connected by a switch.

Inter-process Communication:

Client server- One server, many clients. Server executes continuously, client initiates communication, server satisfies client requests.

Networks

What are messages? –Information

Why networks? – Indispensable part of modern society.

1. Commercial – e-commerce, banking, inventorying, telecommunications, archiving, health.

2. Social – critical infrastructure, homeland security, policing.

3. Human interaction/communication – e-mail, chat, videoconferencing, social networking, entertainment

Appears in evert facet of engineering – Modern trend - Network every (electronic) device (computers, phones, sensors, planes, cars, TVs, appliances, heart monitors)

Wide definition of a Network – A system that carries a commodity between two or more entities. E.g. Transportation network, electric grid, postal, water, telephone.

Computer Network – A system that carries information between two or more entities, in the form of an electric signal.

Transportation vs Computer Networks

Computer Network: Packets/Payload, IP address, Bridge/router, Network congestion, flow control, Alternative route, Collision of packets, Flow priority, routing algorithm

Commonly known Networks

The Internet* (*The global network adopting the IP technology)

Ethernet (LAN)

WiFi

3G/4G

An internet** (**Internet: A network of networks)

Varied types of network: Mobile Phone network, Satellite Network/Communications, Computer Networks

Mobile phone – Basic organisations - Infrastructure networks, Downlink: tower to phones (forward), Uplink: phones to tower (reverse

Arranged into “cells” – Hence “Cell phones”

Cell towers – these typically have 3 sectors, each operates at a different frequency

Antennas are sectored, three 120 degree sectors, each use different frequency, don’t interfere

Cellular Backhaul

Connection between cell site and mobile telephone Switching Office (MTSO)

Can be fibre, copper or wireless.