Introduction to NetworkingOverview

• We will briefly cover:

• The role of data networking

• Key components of any data network

• Converged networks

• Network architectures

• We will start with a high-level view and end with a low-level view of networking

Introduction to NetworkingWhy do we use networks?

• “Connectivity”, the need to communicate (with whom?)

• Hardware resource sharing• e.g. printers, mapped drives

• Application sharing• e.g. administrative systems

• Group working• e.g. video conferences

• Backup and data security• e.g. duplicate data in separate physical location

• Remote configuration and management• e.g. technical staff can audit, fix and install software remotely

Introduction to NetworkingNetworks supporting the way we live

• The Internet - an integral part of our daily routines

• Decide what to wear using online current weather conditions

• Find the least congested route to your destination

• Display weather and traffic video from webcams

• Check your bank balance and pay bills electronically

• Receive and send e-mail, or make an Internet phone call, at an Internet cafe over lunch

• Download new recipes and cooking techniques

• Post and share your photographs, home videos, and experiences with friends or with the world.

Introduction to NetworkingNetworks supporting the way we live

• Education• E-learning

• Resources

• Businesses• Intranets - enables businesses to communicate and perform transactions

among global employee and branch locations

• Extranets - provides suppliers, vendors, and customers limited access to corporate data

• Remote workers - data network enables them to work as if they were on-site, with access to all the network-based tools normally available for their jobs

• Socializing• Online games, interest groups, Instant messaging

• Online entertainment

Introduction to NetworkingData Communication System Elements

• Messages: Information that travels from one device to another

• Devices: Systems on the network that exchange messages with each other

• Protocols: Rules or agreements to govern how the messages are sent, directed, received and interpreted

• Medium: A means of interconnecting devices to transport messages from one to another

Introduction to NetworkingWhy segment messages?

• Communication (music, video or an e-mail message)• sent across a network as one massive continuous stream of bits

• no other device would be able to send or receive messages on the same network while this data transfer was in progress

• large streams of data would result in significant delays

• if a link failed during transmission, the complete message would be lost - and then have to be retransmitted in full

• So divide the data into smaller, more manageable pieces to send over the network

• Segmentation

• many different conversations can be interleaved on the network

• segmentation can increase the reliability of network communications

Introduction to NetworkingCircuit Switching

• A temporary path, or circuit, is created through the various switching locations to use for the duration of the multi-segment message transmission

• If any link or device participating in the circuit fails, the transfer is dropped

• Priority is given to maintaining existing circuit connections, at the expense of new circuit requests

• Since there is a finite capacity to create new circuits, it is possible to occasionally get a message that all circuits are busy and a call cannot be placed

Introduction to NetworkingCircuit Switching

Introduction to NetworkingInformation as “packets”

• Imagine writing a long letter to someone

• But only having postcards on which to write…

• You would write your letter, then send lots of individual postcards

• Each one would need a stamp and an address

• And you would have to number the postcards

• What if one postcard failed to arrive?

Introduction to NetworkingPacket Switching

• Messages are chopped up into small chunks called “packets” before transmission

• Each packet has an “address” attached

• Each packet could be sent via a different route, depending on network traffic and available routes

• Packets are received at the destination (sometimes out of order) and the message is reassembled

Introduction to NetworkingPacket Switching

Introduction to NetworkingDevices

• Message source and destination• Computers, telephones, cameras, music systems, printers

and game consoles

• Intermediary devices• components that make it possible for message to be

directed across the network - exist between the source and destination devices

• Router, switch, access point, proxy server, snoop/filter system…

Introduction to NetworkingDevices

Introduction to NetworkingProtocols

• Devices interconnected by medium to provide services must be governed by rules

• The format or structure of the message

• The method by which networking devices share information about pathways with other networks

• How and when error and system messages are passed between devices

• The setup and termination of data transfer sessions

• some common services and a protocol most directly associated

• WWW – HTTP

• E-mail – SMTP

• IP Telephony- SIP

• TCP/IP (Transmission Control Protocol/Internet Protocol)

• primary protocol of the Internet

• used in home and business networks

• TCP/IP specify the formatting, addressing and routing mechanisms that ensure messages are delivered to the correct recipient

Introduction to NetworkingMedium

• Devices must be interconnected

• Wired• Copper – electrical signal

• twisted pair telephone wire

• coaxial

• Unshielded Twisted Pair (UTP)

• Optical Fiber – light signal

• Wireless• Earth's atmosphere or space -

microwaves signals

• home wireless connection

• terrestrial wireless connection

• Satellite communication

Introduction to NetworkingData Communications

• Local Area Networks (LANs) link together systems within the same site, often the same lab or floor

• Wide Area Networks (WANs) link together sites that may be distributed over a large geographic area

• Example: Staffordshire University network

• There is a variety of (often incompatible) hardware and software systems available for networking

• Large businesses may have multiple LANs per site, interconnected across sites by WANs or MANs

Introduction to NetworkingCriteria and Balances

• High Speed - usually lowest in LANs, high in WANs and highest in backbones (but note that some WANs are slow, LANs are getting faster)

• Low Latency - long delay times cause confusion and inefficiency

• High Reliability - a network full of error messages and repeated information is inefficient

• Cost, maintainability, ease of management, security, scalability, robustness, fitness for purpose