CSCI-690 Computer Networks: Shrinking the globe one click at a time Lecture 2

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CSCI-690Computer NetworksShrinking the globe
one click at a timeLecture 2

• Khurram Kazi

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Major sources of the slides for this lecture

• Slides from Tanenbaums and William Stallings
  website are used in this lecture

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Mankind and Communication

• O mankind! We have created you from a single
  (pair) of a male and female, and have made you
  into nations and tribes, so that you may know
  each other Quran 49.13
• When one ponders over how we get to know each
  other certain thoughts come to mind.
• As we venture outside our own region or domain,
  we tend to follow certain protocols that allow us
  to communicate with each other.
• Try to use common language that both parties
  understand
• Sign language
• Draw pictures, use hand gestures
• In short we find a command ground or similar
  footing which to build a communication platform
  on, even though we may come from diverse cultures
  and background

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Mankind and Communication

• Just as we have diversity in mankind, we have
  disparate, ever-evolving communications networks
• These networks are evolving towards providing
  seamless connectivity between different platforms
  and applications so that they cater to our
  insatiable need to communicate
• An integral component of networking is PROTOCOLS

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OSI A Model developed by International Standards
Organization (ISO)

• Open Systems Interconnection
• Developed by the International Organization for
  Standardization (ISO) has seven layers
• Is a theoretical system delivered too late!
• TCP (Transmission Control Protocol) /IP is the de
  facto standard

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Networking Reference Models

• The OSI Reference Model
• The TCP/IP Reference Model

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TCP/IP Protocol Architecture

• developed by US Defense Advanced Research Project
  Agency (DARPA)
• for ARPANET packet switched network
• used by the global Internet
• protocol suite comprises a large collection of
  standardized protocols

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OSI vs. TCP/IP

• The OSI TCP/IP reference model.

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Reference Models

• Protocols and networks in the TCP/IP model
  initially.

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Key Elements of a Protocol

• syntax - data format
• semantics - control info error handling
• timing - speed matching sequencing

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Simplified Network Architecture
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TCP/IP Layers

• no official model but a working one
• Application layer
• Host-to-host, or transport layer
• Internet layer
• Network access layer
• Physical layer

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Physical Layer

• concerned with physical interface between
  computer and network
• concerned with issues like
• characteristics of transmission medium
• signal levels
• data rates
• other related matters

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Network Access Layer

• exchange of data between an end system and
  attached network
• concerned with issues like
• destination address provision
• invoking specific services like priority
• access to routing data across a network link
  between two attached systems
• allows layers above to ignore link specifics

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Internet Layer (IP)

• routing functions across multiple networks
• for systems attached to different networks
• using IP protocol
• implemented in end systems and routers
• routers connect two networks and relays data
  between them

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Transport Layer (TCP)

• common layer shared by all applications
• provides reliable delivery of data
• in same order as sent
• commonly uses TCP

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Application Layer

• provide support for user applications
• need a separate module for each type of
  application

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Operation of TCP and IP
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Addressing Requirements (will discuss at length
in later lectures)

• two levels of addressing required
• each host on a subnet needs a unique global
  network address
• its IP address
• each application on a (multi-tasking) host needs
  a unique address within the host
• known as a port

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Operation of TCP/IP
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Transmission Control Protocol (TCP)

• usual transport layer is (TCP)
• provides a reliable connection for transfer of
  data between applications
• a TCP segment is the basic protocol unit
• TCP tracks segments between entities for duration
  of each connection

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TCP Header
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User Datagram Protocol(UDP)

• an alternative to TCP
• no guaranteed delivery
• no preservation of sequence
• no protection against duplication
• minimum overhead
• adds port addressing to IP

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UDP Header
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IP Header
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IPv6 Header
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TCP/IP Applications

• have a number of standard TCP/IP applications
  such as
• Simple Mail Transfer Protocol (SMTP)
• File Transfer Protocol (FTP)
• Telnet

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Some TCP/IP Protocols
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Network Design Software Hardware

• Protocol Hierarchies
• Design Issues for the Layers
• Connection-Oriented and Connectionless Services
• Service Primitives
• The Relationship of Services to Protocols

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Design Issues for the Layers

• Addressing
• Error Control
• Flow Control
• Multiplexing
• Routing

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Connection-Oriented and Connectionless Services

• Six different types of service.

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Service Primitives

• Five service primitives for implementing a simple
  connection-oriented service.

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Service Primitives (2)

• Packets sent in a simple client-server
  interaction on a connection-oriented network.

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Starting from the bottom layer of the TCP/IP
working model

• Physical Layer
• Getting into the Fundamentals

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The Theoretical Basis for Data Communication

• Fourier Analysis
• Bandwidth-Limited Signals
• Maximum Data Rate of a Channel

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Bandwidth-Limited Signals

• A binary signal and its root-mean-square Fourier
  amplitudes.
• (b) (c) Successive approximations to the
  original signal.

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Bandwidth-Limited Signals (2)

• (d) (e) Successive approximations to the
  original signal.

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Guided Transmission Data

• Magnetic Media
• Twisted Pair
• Coaxial Cable
• Fiber Optics

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Twisted Pair Widely used in Telephony and
Ethernet cabling

• (a) Category 3 UTP.
• (b) Category 5 UTP.

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Coaxial Cable Primarily used in Cable networks

• A coaxial cable.

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Fiber Optics Widely used in high speed networks

• (a) Three examples of a light ray from inside a
  silica fiber impinging on the air/silica boundary
  at different angles.
• (b) Light trapped by total internal reflection.

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Transmission of Light through Fiber

• Attenuation of light through fiber in the
  infrared region.

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Fiber Cables

• (a) Side view of a single fiber.
• (b) End view of a sheath with three fibers.

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Fiber Cables (2)

• A comparison of semiconductor diodes and LEDs as
  light sources.

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Fiber Optic Networks

• A fiber optic ring with active repeaters.

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Wireless Transmission

• The Electromagnetic Spectrum
• Radio Transmission
• Microwave Transmission
• Infrared and Millimeter Waves
• Lightwave Transmission

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The Electromagnetic Spectrum

• The electromagnetic spectrum and its uses for
  communication.

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Radio Transmission

• (a) In the VLF, LF, and MF bands, radio waves
  follow the curvature of the earth.
• (b) In the HF band, they bounce off the
  ionosphere.

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Politics of the Electromagnetic Spectrum

• Industrial, Scientific and Medical (ISM) bands in
  the United States. Originally reserved
  internationally for the use of RF electromagnetic
  fields for industrial, scientific and medical
  purposes other than communications.

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Lightwave Transmission

• Convection currents can interfere with laser
  communication systems.
• A bidirectional system with two lasers is
  pictured here.

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Communication Satellites

• Geostationary Satellites
• Medium-Earth Orbit Satellites
• Low-Earth Orbit Satellites
• Satellites versus Fiber

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Communication Satellites

• Communication satellites and some of their
  properties, including altitude above the earth,
  round-trip delay time and number of satellites
  needed for global coverage.

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Communication Satellites (2)

• The principal satellite bands.

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Public Switched Telephone System

• Structure of the Telephone System
• The Politics of Telephones
• The Local Loop Modems, ADSL and Wireless
• Trunks and Multiplexing
• Switching

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Structure of the Telephone System

• (a) Fully-interconnected network. (Mesh network)
• (b) Centralized switch.
• (c) Two-level hierarchy.

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Structure of the Telephone System (2)

• A typical circuit route for a medium-distance
  call.

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Major Components of the Telephone System

• Local loops
• Analog twisted pairs going to houses and
  businesses
• Trunks
• Digital fiber optics connecting the switching
  offices
• Switching offices
• Where calls are moved from one trunk to another

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The Local Loop Modems, ADSL, and Wireless

• The use of both analog and digital transmissions
  for a computer to computer call. Conversion is
  done by the modems and codecs (CoDecoder).

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Modems

• (a) A binary signal
• (b) Amplitude modulation
• (c) Frequency modulation
• (d) Phase modulation