NetworksNetworks

Terminology and HardwareTerminology and Hardware

NetworkNetworkA network is a group of connected

computers that can communicate with each other to share information and equipment, such as printers.

Advantages of a networkAdvantages of a network

Sharing Data ReliablySharing Data Reliably – without passing physical – without passing physical volumes, easy backupvolumes, easy backup

Sharing ResourcesSharing Resources – reduces cost of buying – reduces cost of buying hardwarehardware

Sharing ProgramsSharing Programs – programs can run centrally. – programs can run centrally. CommunicationCommunication - people can communicate and - people can communicate and

exchange messages with each other easily, exchange messages with each other easily, effectively, and instantly.effectively, and instantly.

Security OptionsSecurity Options – restricted access – restricted access

Networks are classified by their:Networks are classified by their:

SizeSizeArchitectureArchitectureTopologyTopology

Size of NetworksSize of Networks

LAN – Local Area Network: Connects LAN – Local Area Network: Connects computers and devices in close proximity computers and devices in close proximity such as a small office or building like such as a small office or building like KRSS.KRSS.

WAN – Wide Area Network: Connects a WAN – Wide Area Network: Connects a number of local area networks together number of local area networks together over long distances (across cities, over long distances (across cities, countries etc…)countries etc…)

Architecture ConfigurationsArchitecture ConfigurationsPeer to Peer (p2p): Peer to Peer (p2p): People on a peer to peer

network store their files on their own computers. Anyone may access files stored on any other computer. Before the advent of TCP/IP protocols, peer to peer

provided a simple and inexpensive way to connect fewer than 10 computers. (provided in Windows 98, 2000, & XP Home)

Two Network ConfigurationsTwo Network Configurations

Client/Server - Client/Server - all files stored on a central computer. Everyone connected to the network can access the

files stored on the central server. A Client is a computer that can access information

stored on a server.

TerminologyTerminology

Protocol – set of rules for communication

Network Interface Card (NIC) – Every node is connected through an NIC – most use a 10/100 Mbps Ethernet card

Node – Anything that is connected to the network (computers, printers, scanners etc…)

Backbone – The main cabling of a network that all of the segments connect to. (usually faster than the connection to each NIC)

Segment – Any portion of a network that is separated by a switch, bridge or router, from other parts of the network

The 4 Common Wired Topologies The 4 Common Wired Topologies

Topology – The configuration of nodes connected to the network.

Bus – Each node is directly connected to a Bus – Each node is directly connected to a single central cable called a bus or backbone. single central cable called a bus or backbone. All information travels along the backbone until it All information travels along the backbone until it

reaches its destination node. reaches its destination node. Each end must be terminated (resistor) to keep Each end must be terminated (resistor) to keep

messages from bouncing back when it reaches the messages from bouncing back when it reaches the end of the cable.end of the cable.

1. Bus1. Bus

2. Ring (Token Ring)2. Ring (Token Ring) Nodes are daisy-chained. The end of the network comes back around to the first

node – completes a circuit. Nodes take turns sending and receiving info through use

of a token. Only node with token can send info or receive info

(developed by IBM).

3. Star3. Star Star – each node is connected to a central

device called a hub. The hub/concentrator takes a signal that comes from any node and passes it to all other nodes on the network.

4. Tree (Star-Bus)4. Tree (Star-Bus) The most common - combines star and bus

topologies – nodes in areas are connected to hubs/concentrators (creating stars), hubs are connected together along network backbone – stars are often nested

Basics of EthernetBasics of EthernetWhat it is:What it is: Currently, Ethernet is a type of Currently, Ethernet is a type of

wired network that connects computers wired network that connects computers and other devices.and other devices.The cables are usually copper Nodes The cables are usually copper Nodes

communicate with Packets or Frames of datacommunicate with Packets or Frames of dataWhere it came fromWhere it came from: :

Originally, the material used to connect Originally, the material used to connect computers was ether. It was a good computers was ether. It was a good conductor, and it was thought that it would be conductor, and it was thought that it would be less susceptible to interference.less susceptible to interference.

Problem: it was too expensiveProblem: it was too expensive

Basics of Ethernet cont’dBasics of Ethernet cont’d

• There are practical limits to the size of the There are practical limits to the size of the network: concerns include:network: concerns include:

• Distance limitations – electrical signals Distance limitations – electrical signals weaken as they travel.weaken as they travel.

• Electrical interference scrambles signalsElectrical interference scrambles signals• Practical number of devices as only one Practical number of devices as only one

device can transmit at any given time.device can transmit at any given time.

Ethernet Network StandardsEthernet Network Standards 10BaseT10BaseT

10 Mbps10 Mbps Uses UTP or CAT 5 cablesUses UTP or CAT 5 cables Baseband transmission – only one signal allowed on Baseband transmission – only one signal allowed on

a transmission wire a transmission wire 100BaseT100BaseT

100 Mbps (fast ethernet)100 Mbps (fast ethernet) Use CAT5 cables – fiber optic availableUse CAT5 cables – fiber optic available Broadband – multiple signals on a single wire.Broadband – multiple signals on a single wire.

1000BaseT1000BaseT – Gigabit Ethernet – Gigabit Ethernet 1000 Mbps - Broadband1000 Mbps - Broadband Use CAT5e or CAT6 cablesUse CAT5e or CAT6 cables

UTP - Unshielded Twisted Pair

10/100 BaseT – cheap, 100m max.

STP - CAT5 – Shielded Twisted Pair – used to reduce electrical interference

Coaxial Cable – must run in a ring.

Fiber Optics –expensive – largest bandwidth

Connecting Nodes

4 Types of Connectors4 Types of ConnectorsAUI – D-shaped plug with 15 pins –

common on routers and some hubsRJ45 – connectors look like big phone

connectors – uses eight wires – used by most hubs and NICs

BNC – small round barrel-like connectors – twist and lock together – used for coaxial

Fiber Optic – usually for only one fiber optic strand

CSMA/CDCSMA/CD

CSMA/CD – Carrier Sense Multiple Access with Collision Detection

Regulates Regulates communication communication among nodesamong nodes

Provides a “fair” set Provides a “fair” set of rules for use of the of rules for use of the lineline

Hub (how hubs work)Hub (how hubs work)

Receive dataReceive dataBroadcast out data on all linesBroadcast out data on all linesReceiving computers are responsible for Receiving computers are responsible for

listening to see if the data is for themlistening to see if the data is for them

Problems:

More computers more collisions

Can’t scale more than 10 computers (Scalability)

Takes more time on average for information to reach the intended node (Latency)

Router (how routers work)Router (how routers work)

Receive dataReceive dataFind out who the data is forFind out who the data is forSend out data on a port that can Send out data on a port that can

eventually reach the intended receiver eventually reach the intended receiver without going through a high traffic areawithout going through a high traffic area

Keeps a table inside the router to keep Keeps a table inside the router to keep track of where the high traffic areas aretrack of where the high traffic areas are

Switch/Bridge (how switch’s work)Switch/Bridge (how switch’s work) LAN Switches

break hub networks into distinct segments - makes it possible for several users to send data over the network at the same time without slowing each other down

creates a series of instant networks that contain only two devices communicating with each other at that particular moment.

Nodes communicate only with the switch, so it creates a collision free environment

WirelessWireless

BluetoothBluetoothWiFi: Wireless Fidelity - Otherwise known WiFi: Wireless Fidelity - Otherwise known

as Wireless Networking as Wireless Networking

IEEE StandardsIEEE Standards

802.3 – Ethernet wired standard802.3 – Ethernet wired standard802.3 is the 10 Mbps standard802.3 is the 10 Mbps standard802.3u is the 100 Mbps standard802.3u is the 100 Mbps standard802.3z is the 1000 Mbps standard802.3z is the 1000 Mbps standard

802.11 – Ethernet wireless standard802.11 – Ethernet wireless standard802.11b is the 11 Mbps standard802.11b is the 11 Mbps standard802.11g is the 54 Mbps standard802.11g is the 54 Mbps standard

IP AddressIP Address

A four part number assigned to every A four part number assigned to every computer on a networkcomputer on a network ie 192.168.1.2ie 192.168.1.2

Each part of the number can be between 0-255Each part of the number can be between 0-255

A device can be manually configured to A device can be manually configured to have the same address every time the have the same address every time the device turns ondevice turns on

A device can be set to take an assigned A device can be set to take an assigned number from a server or router every time number from a server or router every time it is turned onit is turned on

MAC AddressMAC Address

A six part hexadecimal number that is A six part hexadecimal number that is unique to unique to everyevery network card network card Ie 00:02:3F:DC:75:C4Ie 00:02:3F:DC:75:C4No two network cards have the same MAC No two network cards have the same MAC

address.address.The address is permanently put into the NIC The address is permanently put into the NIC

at the manufacturerat the manufacturer

TCP/IPTCP/IP Transmission Control Protocol/Internet Protocol

Uses IP addresses for communication (i.e. 199.175.20.10)

Developed by ARPA (Advanced Research Projects Agency) at BB&N in 1969.

Allows for Packet Switching Large pieces of data are broken into smaller pieces

called packets Included with each data packet is the address of the

sending node and receiving devices.

UDP/IPUDP/IP

User Datagram Protocol (UDP)User Datagram Protocol (UDP)A connection-less, unreliable, transport A connection-less, unreliable, transport

protocolprotocolPerfect for real time communicationPerfect for real time communication

Internet radioInternet radioVoice over IP (internet telephone)Voice over IP (internet telephone)Music on demandMusic on demandVideo conferencingVideo conferencingVideo on demandVideo on demand

SpeedsSpeeds

1 10 11 1254

100

480400

800

0

100

200

300

400

500

600

700

800

900

Mb

ps

SecuritySecurity

What can you do to stop someone from What can you do to stop someone from breaking into your system?breaking into your system?