What is a Network?

In information technology, a network is a series of points or nodes interconnected by

communication paths.

In a network, a node is a connection point. In general, a node has programmed or engineered capability to recognize and process or forward transmissions to other nodes.

What is a Node?

A network is an interconnected system of things or people◦ Religions◦ Business contacts◦ Snail Mail◦ Social Media◦ Broadcasting - NBC, CBS, ABC, PBS◦ Transportation (highways & rail)◦ Cellular phone service◦ …and of course computer based (internet)

Generally speaking . . .

What is the Internet?

The Internet is a worldwide system of computer networks - a network of networks in which users at any one computer can, if

they have permission, get information from any other computer.

Intranet◦ An organizations restricted computer network ◦ Private, yet using WWW software

Extranet◦ Part of a organization‘s intranet that is extended

to users outside the organization – usually via WWW.

◦ Customer access Internet

◦ A worldwide computer network using TCP/IP protocol to transmit and exchange data. (TCP/IP is a set of communication protocols used by

networks.)

Types of Computer Networks

Simultaneous Access◦ Software/Programs◦ Data

Device Sharing◦ Printers◦ NAS – Network Access Storage

Communication◦ Email◦ VOIP – Voice over internet protocol (Skype)

Archiving◦ Backups of multiple clients by a single server

Computer Networks – Benefits

 In communication networks, a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines. There are two ways of defining network geometry: the physical topology and the logical (or signal) topology.

What is Topology?

Topologies◦ Physical connectivity

Nodes and Addressing Geographical Distribution

◦ Where are the nodes? Work Load

◦ Server networks use the nodes to disperse the workload

Computer Networks – Categorized

Network topology is the physical interconnections of the elements (Links, Nodes, Clients, etc.) of a computer network

Main Types◦ Star◦ Bus◦ Ring◦ Wireless◦ Hybrid

Computer Networks - Topology

Star Topology

Star topology is the most common topology used in today’s workplace.

North Greenville University in Tigerville uses star topology.

Bus topology is where in a computer network, a bus is a transmission path on which signals are dropped off or picked up at every device attached to the line. WAP (wireless access points) are not necessary needed.

Bus Topology

Ring Topology

A ring is a network topology or circuit arrangement in which each device is attached along the same signal path to two other devices, forming a path in the shape of a ring.

Wireless TopologyA wireless Internet service provider (WISP) is an Internet service provider (ISP) that allows subscribers to connect to a server at designated hot spots (access points) using a wireless connection such as Wi-Fi.

Standards – IEEE 802.11◦ 802.11a◦ 802.11b◦ 802.11g◦ 802.11n

802.11n has a higher frequency and transmits fastest and the longest range

Wireless - 802.11 is an evolving family of specifications for wireless local area networks (WLANs). There are several specifications in the family and new ones are occasionally added.

Coax cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses.◦ Benefit is one wire for all

computers

Cabling - Wired

Cabling - Wired

Ethernet twisted pair cable is faster than Wireless and is very commonly used in businesses

Ethernet is the most widely-installed local area network (LAN) technology.◦ One wire per node/client

Fiber optic (or "optical fiber") refers to the medium and the technology associated with the transmission of information as light impulses along a glass or plastic wire or fiber.

Cabling - Wired

Types◦ WIMAX (Worldwide Interoperability for Microwave

Access)◦ Satellite (Dish Network/Direct TV)

High transmission rate (has to be) & latency

Each node needs antenna to connect◦ Low frequency – reliable but slower transmission◦ High frequency – less reliable but higher speed

transmission

Cabling - Wireless

Fiber is the fastest - pricey

Ethernet twisted pair – cheaper and faster

COAX – still needed

Wireless – price greater than Ethernet twisted pair

Cabling – Which is best

Node – Client◦ Printers◦ Desktops◦ Laptops◦ Copiers◦ Network storage devices◦ Routers◦ Anything that can connect to a network

Cell phone GPS device IPOD/PSP/XBOX/PS3/Tivo/DVR/Slingbox…

Computer Networks – Nodes

How does the network identify a node?◦ NIC MAC address – every node’s is unique

Format: 01-23-45-67-89-ab, 01:23:45:67:89:ab Each vendor has a pool of addresses

Linksys D-Link Etc.

Hardware address Translated into a software address (IP address)

Two standards for Internet Protocol (IP) IP V4 IP V6

Computer Networks – Addressing

IP Addresses◦ IP addresses are four octets of the form and range

(0-255).(0-255).(0-255).(0-255)◦ Data is routed between nodes based on IP addresses◦ Each domain name translates to a unique IP address

www.google.com translates to 208.67.217.231 i.e. try Ping www.google.com from DOS prompt

ICANN.org is in charge of DNS Maintains Internic.org to provide info about domain names

◦ A profound shortage of addresses with IP V4 4.3 billion addresses with some reserved Usefulness of static addresses How many nodes in the world?

Computer Networks – Addressing IP V4

IP Addresses◦ Addresses structure:(8 groups of 4 base16 digits)

2001:0db8:85a3:0000:0000:8a2e:0370:7334 ◦ Version 6 provides enough addresses for every

atom in the universe - provided they buy a computer

◦ Supports 2128 (about 3.4×1038) addresses.◦ Currently used at main WWW routing points◦ Advantages of having your own address?

Your are known wherever your node physically resides

Computer Networks – Addressing IP V6

LAN – Local Area Network◦ Ex. – NGU

VLAN – Virtual LAN (act as a LAN due to common set of needs - collaboration)

MAN – Metropolitan Area Network◦ Ex. - City of Greenville

WAN – Wide Area Network◦ Ex. – Internet

Computer Networks – Geography

Server Based◦ Thin client - relies heavily on server processing◦ Ex. – NGU email server

Client Server Based◦ Fat client – shares in the work load with less

expensive server◦ Ex. – NGU CAMS (clients process the reports)

Peer to Peer Based◦ Each computer can act as client or server◦ Ex. - Home network

Computer Networks – Workload

All networks◦ Authentication

User name and password◦ Encryption

https – encrypts credit card account #s, email◦ Firewall Software

What can network users get to on your machine◦ Anti-virus Software

Protect against malware Vendors – McAfee, Symantec, AVG, etc…

◦ Finger Print Scanner◦ Contingency planning – what if the unexpected

happens Backups, backups, backups

Computer Network Security

Wireless◦ WEP – Wired Equivalency Protocol

NOT secure (Google “breaking wep encryption”)◦ WPA – Wireless Protected Access

WPA & WPA2 – secure provided you use good pass phrases

Computer Network Security

What do we transmit/exchange?◦ Text

Emails Print jobs Chat

◦ Graphics Pictures

◦ Video Movies Live Streaming

◦ Audio Songs Voice

Computer Network Data Transmission

How is it transmitted?◦ Broken into packets

Header – Packet 1 Trailer – Last Packet Those in between

◦ Not all packets take the same route◦ Reassembled on receipt to match that sent

Who owns the internet?◦ Many companies – Sprint, Verizon, Time-Warner,

etc. We’re just renting space

Computer Networks – Data Transmission

◦ Transmission is not perfect Must have schemes for re-sending dropped packets

What about audio & video – is there any reason to re-send?

What about your debit card atm transmission Easier to resend the whole thing or just what’s missing?

Computer Networks – Data Transmission

TCP/IP – Transmission Control Protocol/Internet Protocol◦ Standard network data exchange

protocol(standard)◦ TCP applications

FTP – File transfer protocol (transfer files) Telnet – Terminal connections SMTP – email transmission POP3 – email transmission

◦ IP applications HTTP – Hypertext transfer protocolVOIP – Voice over IP

Network protocols

ISP – Internet service provider◦ Types of connection for the home

Cable Modem DSL Modem ISDN Modem 56K Dial-up Modem Home satellite

◦ Types of connection for business Cable Modem – higher capacity than home DSL Modem – “ “ “ DS1/T1 High speed line (DS3 /T3 even better) Satellite

◦ Businesses concerned with throughput◦ Become a node on ISP’s network

Internet - Connections

Domains◦ Common

.com, .net, .org, .edu, .gov◦ Not so common

.uk, .us, .tv, .biz, info (checkout godaddy.com) Sub Domains

◦ Part of the larger domain◦ Ex. www.ngu.blackboard.com

Domain is www.blackboard.com Sub domain is ngu

Accessed via ngu.blackboard.com

Internet - Domains

Websites are designed using html (hypertext markup language)◦ Easy enough for anyone to create

Write html Use applications like Dreamweaver or Microsoft Expression Can save MS Office 2007 files as web pages

◦ Store cookies Ease of use User names Passwords (not so good if not secure – https)

◦ Store temporary files Faster browsing Fills up hard drive

Fragmentation

◦ Your browser will let you purge cookies and files.

Computer Networks - Websites

Data specific Websites are encoded using XML (Extensible Markup Language)

Example – see notes Standard for data exchange

◦ MS Access can import XML Microsoft Office 2007 file naming

◦ Word “Document.docx”◦ Excel “Spreadsheet.xlsx”◦ PowerPoint “Presentation.pptx”◦ Access – “Database.accdb” ?????

Computer Networks – Data specific Websites

http://wordnetweb.princeton.edu http://compnetworking.about.com http://en.wikipedia.org/ http://www.emailclients.net/

References