EthernetEthernet

EthernetEthernet Ethernet is the standard communications protocol Ethernet is the standard communications protocol embedded in software and hardware devices, embedded in software and hardware devices, intended for building a local area network (LAN).intended for building a local area network (LAN).

Contention based communication Contention based communication

Two signals at the same time is called a collisionTwo signals at the same time is called a collision

If there is a signal on the wire the computer waits If there is a signal on the wire the computer waits a random amount of time, then tries againa random amount of time, then tries again

EthernetEthernetUses Frames to communicate with all devicesUses Frames to communicate with all devices

Frame must have a source address and a Frame must have a source address and a destination address destination address

EthernetEthernetTerms:Terms:Medium - Medium - Ethernet devices attach to a common medium that Ethernet devices attach to a common medium that provides a path along which the electronic signals will travel. provides a path along which the electronic signals will travel. Historically, this medium has been coaxial copper cable, but today it Historically, this medium has been coaxial copper cable, but today it is more commonly a twisted pair or fibre optic cabling. (UTP)is more commonly a twisted pair or fibre optic cabling. (UTP)

Segment – Segment – Everyone in a LAN that is communicating on the same Everyone in a LAN that is communicating on the same medium (This room, Library) medium (This room, Library)

Node - Node - Devices that attach to that segment are stations or nodes.Devices that attach to that segment are stations or nodes.

(Computer)(Computer)

Collision Domain - Collision Domain - is a physical network segment where data is a physical network segment where data packets can “collide”packets can “collide”

Token RingToken Ring Local area network (LAN) technologyLocal area network (LAN) technology

It uses a special three-byte frame called a token It uses a special three-byte frame called a token that travels around the ring. that travels around the ring.

Token ring frames travel completely around the Token ring frames travel completely around the loop. loop.

Network Network Architectures Architectures

Client ServerClient Server Communication between service providers (Communication between service providers (serversservers) and ) and service requesters, called clients service requesters, called clients

A server machine is a high-performance host that is running A server machine is a high-performance host that is running one or more server programs which share its resources with one or more server programs which share its resources with clients clients

A client does not share any of its resources, but requests a A client does not share any of its resources, but requests a server's content or service function.server's content or service function.

Types of Servers: Types of Servers: – Print serversPrint servers– DNS (Domain Name Servers)DNS (Domain Name Servers)– File Storage ServersFile Storage Servers– Database ServerDatabase Server– Internet ServersInternet Servers– Application ServersApplication Servers

Client ServerClient Server All data is stored on the servers, which generally have far greater All data is stored on the servers, which generally have far greater security controls than most clientssecurity controls than most clients

With tens or hundreds of client PC`s, a server is the only With tens or hundreds of client PC`s, a server is the only way to manage complex and simultaneous operationsway to manage complex and simultaneous operations

Dedicated ServerDedicated Server– Servers only job is to server the other computersServers only job is to server the other computers

Non Dedicated Server Non Dedicated Server – Server is used as a desktop computer for everyday useServer is used as a desktop computer for everyday use

Client ServerClient Server AdvantagesAdvantages

– High security levelsHigh security levels Login into serverLogin into server Different levels of access for files and optionsDifferent levels of access for files and options

– Centralized resourcesCentralized resources– Easy to add computers to network (Scalable)Easy to add computers to network (Scalable)– Easier to upgradeEasier to upgrade

DisadvantagesDisadvantages– More expensive to setup and maintain (increased cost) More expensive to setup and maintain (increased cost) – If server crashes the network is downIf server crashes the network is down– Server software (OS) is more expensiveServer software (OS) is more expensive

Peer to PeerPeer to Peer Allows for two or more computers to pool their Allows for two or more computers to pool their resources togetherresources together All clients provide resources, which may include All clients provide resources, which may include files, printers, storage spacefiles, printers, storage space

As nodes arrive and demand on the system As nodes arrive and demand on the system increases, the total capacity of the system also increases, the total capacity of the system also increases increases

Peer to PeerPeer to Peer Many file sharing networks, including Gnutella, G2 Many file sharing networks, including Gnutella, G2 and Limewire. Peer-to-peer file sharing popularized and Limewire. Peer-to-peer file sharing popularized peer-to-peer technologies. As of 2009, it is the peer-to-peer technologies. As of 2009, it is the largest contributor of network traffic on the Internet. largest contributor of network traffic on the Internet.

Best used for small networks under 10 computersBest used for small networks under 10 computers

Used where security is not a great concernUsed where security is not a great concern

Peer to PeerPeer to PeerAdvantagesAdvantages

– No need for network administrator ($45 per hour)No need for network administrator ($45 per hour)– Network is fast / inexpensive to set upNetwork is fast / inexpensive to set up– Each PC in the network can back up another PC for securityEach PC in the network can back up another PC for security– Easiest type of network to buildEasiest type of network to build– As clients increase so does the capacityAs clients increase so does the capacity

DisadvantagesDisadvantages– Not centralized making administration difficultNot centralized making administration difficult– Lack of securityLack of security– No one computer is reliableNo one computer is reliable– Demand on the network as computers are addedDemand on the network as computers are added– Depended on all computers to functionDepended on all computers to function– If one computer is used more often, then that computer If one computer is used more often, then that computer becomes slowerbecomes slower