Telecommunications, the Internet, Intranets, and Extranets

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Telecommunications, the Internet, Intranets, and
Extranets
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Elements of a Telecommunications System
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Components of a Communications System

• Communications network devices connected to one
  or more communication channels/media.
• Telecommunication device a hardware that
  transmits or receives electronic signals
  efficiently.
• Telecommunications Media Anything that carries
  an electronic signal and interfaces between a
  sending device and a receiving device.

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Analog and Digital signals
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Media Types
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Common Wiring and Cabling Types
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Common Telecommunications Devices
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Simplex, Half-duplex, Full-duplex transmissions
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Different transmission modes circuit, message,
packet switching

• Circuit Switching channel is dedicated to the
  user once a connection is paid e.g. voice
  telephone networks. Even if both sender and
  receiver remain silent for a long time, the
  channel is still theirs until they hang up.
• Message Switching channel is only kept open if
  there are messages to send. Messages are stored
  if a channel is not available, and is forwarded
  later when the channel is available.

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Packet Switching

• This is for networks with many channels that are
  connected to nodes, router or switching devices
  e.g. internet.
• Messages (voice, data, text, images) are first
  broken into fixed-size packets at the sender end
  e.g. email message.
• Each packet is sent to the receiver end via the
  fastest or shortest route. Thus packets of a
  message may travel different routes.
• Can balance the traffic loads on many channels if
  packet size is small.

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Packet Switching
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Network connection device Router

• A network connection device that connects one
  network to another network.
• Used in the internet as the internet consists of
  many networks connected together.
• Once a router receives a packet, it confirms the
  packets destination address, then determines the
  available routes to the receiver.
• Then, the router finds the fastest and/or
  shortest path for the packet to the destination.

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Routing Messages Over the Internet
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Terminal connection device HUB

• Allows multiple terminals, workstations and PCs
  in a network to be connected at a common point
  before being connected to the internet see next
  slide.
• A hub contains multiple ports one port for each
  of terminals, workstations and PCs in a network.

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Connecting Computing Devices Using a Home Network
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Network types

• Local area network (LAN) connects computer
  systems devices within the same geographic area
  e.g. office building, factory, using twisted-pair
  or fiber-optic cable.
• Wide area network (WAN) a network that ties
  together larger geographic regions using
  microwave satellite transmission or telephone
  lines.
• International network a network that links
  computer systems between countries e.g. intranet,
  internet.

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A Typical LAN
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A Wide Area Network
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Internet Service Provider (ISP)

• ISP is any company that provides individuals and
  organizations with access to the Internet,
  usually big telephone companies.
• To use this type of connection, you must have an
  account with the service provider and software
  that allows a direct link via TCP/IP.
• You should ask from ISP for network security
  software such as firewall etc.
• Firewall - a device that sits between your
  internal network and the outside Internet

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Intranet

• An internal corporate network built using
  Internet technologies, and WWW standards.
• It is used by the employees of an organization to
  access corporate information.
• Supports what has come to be known as workgroup
  computing - people working together in teams
• Has ability to store and share information in any
  form (text, video, sound, graphics, handwritten
  memos, or hand-drawn figures)

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Extranet

• A network that links selected resources of the
  intranet of a company with its customers,
  suppliers, or other business partners.
• Also built on internet technologies and Web
  standards.

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Summary of Internet, Intranet, and Extranet Users
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Net Issues Privacy Security

• Internet is a public, huge, global network with
  no centralized governing body controlling it.
• In cryptography, encryption is the process of
  transforming information (referred to as
  plaintext) using an algorithm (or method) to make
  it unreadable to anyone except those possessing
  special knowledge, usually referred to as a key.
  The result of the process is encrypted
  information (in cryptography, referred to as
  ciphertext).
• In many contexts, the word encryption also
  implicitly refers to the reverse process,
  decryption (e.g. software for encryption can
  typically also perform decryption), to make the
  encrypted information readable again (i.e. to
  make it unencrypted).

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Net Issues Privacy Security

• Cryptography process of converting a message
  into a secret code and changing the encoded
  message back to regular text.
• Encryption used for keeping secrets, and to
  verify the sender of a message, and to indicate
  whether or not it was tampered with en route e.g.
  digital signature.

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Cookies Privacy Security

• Cookie is a text file that an Internet company
  can place on the hard disk of a computer system
  to keep track of visits to the site and the
  actions people take
•  Cookies are parcels of text sent by a server to
  a web browser and then sent back unchanged by the
  browser each time it accesses that server.
•  Cookies are used for authenticating, tracking,
  and maintaining specific information about users,
  such as site preferences or the contents of their
  electronic shopping carts.

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Cookies Privacy Security

• Cookies have been of concern for Internet
  privacy, since they can be used for tracking
  browsing behavior.
•  Cookies have also been criticized because the
  identification of users they provide is not
  always accurate and because they could
  potentially be a target of network attackers.

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The World Wide Web

• An Internet service comprising tens of thousands
  of independently owned computers that work
  together as one.
• Home page
• Hypermedia
• Hypertext markup language (HTML)

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U.S. Top-Level Domain Affiliations
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Sample HTML