CSCI 370 CSCI-370 C omputer Networks: Shrinking the globe one click at a time Lecture 2 Khurram Kazi

Major sources of the slides for this lecture  Slides from Tanenbaum’s and William Stallings’ website are used in this lecture K KaziCSCI 370 2

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 K KaziCSCI 370 3

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 K KaziCSCI 370 4

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 K KaziCSCI 370 5

Networking Reference Models  The OSI Reference Model  The TCP/IP Reference Model K KaziCSCI 370 6

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 K KaziCSCI 370 7

OSI vs. TCP/IP  The OSI & TCP/IP reference model. K KaziCSCI 370 8

Reference Models  Protocols and networks in the TCP/IP model initially. K KaziCSCI 370 9

Key Elements of a Protocol  syntax - data format  semantics - control info & error handling  timing - speed matching & sequencing K KaziCSCI

Simplified Network Architecture K KaziCSCI

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 K KaziCSCI

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 K KaziCSCI

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 K KaziCSCI

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 K KaziCSCI

Transport Layer (TCP)  common layer shared by all applications  provides reliable delivery of data  in same order as sent  commonly uses TCP K KaziCSCI

Application Layer  provide support for user applications  need a separate module for each type of application K KaziCSCI

Operation of TCP and IP K KaziCSCI

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 K KaziCSCI

Operation of TCP/IP K KaziCSCI

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 K KaziCSCI

TCP Header K KaziCSCI

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 K KaziCSCI

UDP Header K KaziCSCI

IP Header K KaziCSCI

IPv6 Header K KaziCSCI

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

Some TCP/IP Protocols K KaziCSCI

Network Design: Software & Hardware  Protocol Hierarchies  Design Issues for the Layers  Connection-Oriented and Connectionless Services  Service Primitives  The Relationship of Services to Protocols K KaziCSCI

Design Issues for the Layers  Addressing  Error Control  Flow Control  Multiplexing  Routing K KaziCSCI

Connection-Oriented and Connectionless Services  Six different types of service. K KaziCSCI

Service Primitives  Five service primitives for implementing a simple connection- oriented service. K KaziCSCI

Service Primitives (2)  Packets sent in a simple client-server interaction on a connection-oriented network. K KaziCSCI

Starting from the bottom layer of the TCP/IP working model  Physical Layer:  Getting into the Fundamentals K KaziCSCI

The Theoretical Basis for Data Communication Fourier Analysis Bandwidth-Limited Signals Maximum Data Rate of a Channel K KaziCSCI

Bandwidth-Limited Signals A binary signal and its root-mean- square Fourier amplitudes. (b) – (c) Successive approximations to the original signal. K KaziCSCI

Bandwidth-Limited Signals (2) (d) – (e) Successive approximations to the original signal. K KaziCSCI

Guided Transmission Data Magnetic Media Twisted Pair Coaxial Cable Fiber Optics K KaziCSCI

Twisted Pair: Widely used in Telephony and Ethernet cabling (a) Category 3 UTP. (b) Category 5 UTP. K KaziCSCI

Coaxial Cable: Primarily used in Cable networks A coaxial cable. K KaziCSCI

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. K KaziCSCI

Transmission of Light through Fiber Attenuation of light through fiber in the infrared region. K KaziCSCI

Fiber Cables (a) Side view of a single fiber. (b) End view of a sheath with three fibers. K KaziCSCI

Fiber Cables (2) A comparison of semiconductor diodes and LEDs as light sources. K KaziCSCI

Fiber Optic Networks A fiber optic ring with active repeaters. K KaziCSCI

Wireless Transmission The Electromagnetic Spectrum Radio Transmission Microwave Transmission Infrared and Millimeter Waves Lightwave Transmission K KaziCSCI

The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication. K KaziCSCI

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. K KaziCSCI

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. K KaziCSCI

Lightwave Transmission Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here. K KaziCSCI

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

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. K KaziCSCI

Communication Satellites (2) The principal satellite bands. K KaziCSCI

Public Switched Telephone System Structure of the Telephone System The Politics of Telephones The Local Loop: Modems, ADSL and Wireless Trunks and Multiplexing Switching K KaziCSCI

Structure of the Telephone System (a) Fully-interconnected network. (Mesh network) (b) Centralized switch. (c) Two-level hierarchy. K KaziCSCI

Structure of the Telephone System (2) A typical circuit route for a medium-distance call. K KaziCSCI

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 K KaziCSCI

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). K KaziCSCI

Modems (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation K KaziCSCI