Download Introduction - Staffordshire University

Introduction to Networking
Overview
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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 Networking
Why 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 Networking
Networks supporting the way we live
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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 Networking
Networks 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 Networking
Data 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 Networking
Why 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 Networking
Circuit 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 Networking
Circuit Switching
Introduction to Networking
Information 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 Networking
Packet 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 Networking
Packet Switching
Introduction to Networking
Devices
• 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 Networking
Devices
Introduction to Networking
Protocols
• 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 Networking
Medium
• 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 Networking
Data 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 Networking
Criteria 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