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CPSC441. Computer Communication. What this Course is About?. Provide an introduction to modern telecommunications and computer networks, including information about : the physical characteristics of current transmission media

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CPSC441

Computer Communication


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What this Course is About?

  • Provide an introduction to modern telecommunications and computer networks, including information about :

    • the physical characteristics of current transmission media

    • layered protocol hierarchies commonly used for the organization of modern networks

    • standards and protocols for several of these layers.


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Topics

  • INTRODUCTION

  • PHYSICAL LAYER

  • DATA LINK LAYER

  • NETWORK LAYER

  • TRANSPORT LAYER

  • APPLICATION LAYER

  • TCP/IP SECURITY


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Topics

  • INTRODUCTION

    • HISTORY

    • TYPES OF NETWORKS: LAN, WAN

    • TYPES OF NETWORKS: Client - Server, Peer to Peer

    • THEORETICAL NETWORK: OSI model, TCP/IP model

    • EXAMPLES OF NETWORKS, SERVICES

  • PHYSICAL LAYER

  • DATA LINK LAYER

  • NETWORK LAYER

  • TRANSPORT LAYER

  • APPLICATION LAYER

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

      • SOME PHYSICS

      • TRANSMISSION MEDIA, MODULATION

      • TELEPHONE SYSTEM, MODEMS

      • BASEBAND, BROADBAND TRANSMISSION

      • ATM TRANSMISSION

  • DATA LINK LAYER

  • NETWORK LAYER

  • TRANSPORT LAYER

  • APPLICATION LAYER

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

    • DATA LINK LAYER

      • FRAMES, FRAME MANAGEMENT

      • ERROR CHECKING

      • DATA LINK PROTOCOLS

      • EXAMPLES: ETHERNET, TOKEN RING, others

  • NETWORK LAYER

  • TRANSPORT LAYER

  • APPLICATION LAYER

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

    • DATA LINK LAYER

    • NETWORK LAYER

      • ROUTING, ROUTING PROTOCOLS

      • IP ADDRESSING, SUBNETS, NETMASK

  • TRANSPORT LAYER

  • APPLICATION LAYER

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

    • DATA LINK LAYER

    • NETWORK LAYER

    • TRANSPORT LAYER

      • TCP, UDP protocols

      • SOCKET PROGRAMMING

  • APPLICATION LAYER

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

    • DATA LINK LAYER

    • NETWORK LAYER

    • TRANSPORT LAYER

    • APPLICATION LAYER

      • Domain Name Service (DNS)

      • BASIC INTERNET SERVICES

  • TCP/IP SECURITY


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    Topics

    • INTRODUCTION

    • PHYSICAL LAYER

    • DATA LINK LAYER

    • NETWORK LAYER

    • TRANSPORT LAYER

    • APPLICATION LAYER

    • TCP/IP SECURITY

      • INTRO TO CRYPTOGRAPHY

      • Secure Socket Layer (SSL)

      • FIREWALLS


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    Quotes

    • Computers in the future may weigh no more than 1.5 tons

    • “I think there is a world market for maybe five computers.” Thomas Watson Chairman of IBM 1943

    • “There is no reason anyone would want a computer in their home” Ken Olson president DEC 1977

    • “640K ought to be enough for anybody” Bill Gates 1981


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    History of Data Communications

    • Communications industry was already established at the beginning of the computer era.

    • First type of data communication was terminals attached to mainframes via modems and telephone lines.


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    History of Data Communications

    • Development of Semi-Automatic Business Research Environment (SABRE)

    • Development of Packet Distribution Network (PDN), allowed Advanced Research Projects Agency (ARPA) to develop ARPANET.


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    History of Data Communications

    • Development of other Proprietary Computer Networks (works on one manufacturers equipment)

      • Systems Network Architecture (SNA) developed by IBM

      • Decnet Developed by Digital

      • Telnet developed by General Telephone and Electronics (GTE)


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    Historical Events

    • 1948 first commercial computer installed UNIVAC I

    • 1958 first U.S. communication satellite

    • 1964 SABRE airline reservation system packet switching network (purposed by RAND)

    • 1969 ARPANET first packet switching network begins operation


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    Historical Events

    • 1971 first computer chip

      • 4 bit, 2,300 transistors

    • 1972 Ethernet specifications formulated

    • 1974 IBM introduces SNA

    • 1975 Altair 8800 first commercial microcomputer sold as kit


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    Historical Events

    • 1975 Paul Alan / Bill Gates wrote a BASIC language interpreter for the Altair, they formed Microsoft

    • 1976 Woznaik and Jobs built Apple I and formed Apple Computer Company

    • 1979 VisiCalc first commercial spread sheet introduced


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    Historical Events

    • 1981 IBM introduced IBM PC one floppy

    • 1983 TCP/IP becomes the official protocol on ARPANET

    • 1984 Apple introduced GUI with Apple Macintosh

    • 1986 PC Convertible (first laptop (luggable))


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    Historical Events

    • 1988 OS/2 shipped by IBM first multitasking operating system for PC 1989 Intel releases 486

    • 1989 Microsoft releases Windows 3.0 1991

    • 1989 NSF replaces ARPANET as internet backbone

    • 1991 WWW invented by CERN physicist Tim Berners-Lee


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    Historical Events

    • 1992 Mosaic release first GUI web browser

    • 1995 Netscape goes from startup to $2.9 billion in one year

    • 2000 .com melt down


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    Data Communications

    Data Communications

    Terminal to Computer

    Computer to Computer

    Local Area Networks

    Wide Area Networks

    Peer to Peer

    Client Server


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    PC as an Information tool

    • Local Area Network (LAN)

      • number of computers connected together

      • usually a small geographical area

        • office, floor, classroom

      • share resources (software, hardware)


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    PC as an Information Tool

    • Wide Area Network (WAN)

      • connection of LANs

      • connected by wire, microwave, satellite


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    Resource Sharing

    • Sharing of Information

      • Types

        • Mission critical data

        • Frequently used data (form letters)

        • Policy / procedure manuals

      • Who needs what access

        • update

        • read only


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    Information Sharing

    • What information is vital to your organization

    • What information do you need to keep consistent, or restricted, or in one place for everyone to access

    • Consider how a network (centralized control) would help


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    Hardware Sharing

    • Allows sharing of devices such as:

      • Printers

      • Fax modems

      • Scanners

      • Disk drives

      • CD ROM's

      • Tape Backup units

      • Plotters


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    Software Sharing

    • Software need not be installed on every computer

    • One install, one central location for updates

    • Consistent configuration

    • Grant or deny access to a program


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    Software Sharing

    • License considerations

      • single user

      • license per user

      • site license


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    Backup

    • Backup of central server or disk

    • Hard to backup a number of stand alone computers

    • Usually backup of workstation is responsibility of the user


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    Computer Roles in a Network

    • Clients

      • use network resources

      • provide no resources to the network

      • run their own operating system

    • Servers

      • provide resources to the network

    • Peers

      • use and provide services


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    Operating systems

    • Server

      • Novel NetWare

      • Windows NT

    • Client

      • Windows 2000

      • DOS

      • OS/2

    • Peer

      • Windows 2000


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    Categories of Networks

    • Client / Server

      • contains clients and supporting servers

      • may be dedicated or non dedicated

      • server centric

      • network centric


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    Categories of Networks

    • Peer to Peer

      • network of computers sharing resources with no dedicated server


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    Server Based Networks

    • Advantages

      • Strong central security

      • Central file storage (backup, data organization)

      • Share hardware and software

      • Optimize dedicated servers for special purpose

      • Less intrusive security (network centric)

      • manages shared resources

      • manages users


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    Server Based Networks

    • Disadvantages

      • Expensive hardware

      • Expensive software

      • Dedicated network administrator


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    Peer to Peer

    • Advantages

      • no extra hardware or software

      • easy setup

      • no network administrator

      • users control resource sharing

      • no reliance on other computers for their operation

      • lower cost for small networks


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    Peer to Peer

    • Disadvantages

      • additional load on computers because of resource sharing

      • smaller networks

      • lack of central organization, harder to find data

      • no central point of storage (backup)

      • user administer their network

      • weak security

      • no central management


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    Peer Security /Server Security

    • Peer to Peer

      • less secure than client server

      • security is controlled by access to a share directory (password)

      • each resource requires a separate password

      • cannot distinguish between users

    • Client / Server

      • network logins

      • permissions granted to users for files / resources


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    Home Network Applications (2)

    • In peer-to-peer system there are no fixed clients and servers.


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    Selecting the Network type

    • Cost

    • Expertise

    • Security issues

    • Number of work stations

    • Types of applications


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    Types of servers

    • Servers can designed for a specialized purpose

      • file servers

      • print servers

      • Application servers

      • Message servers

      • database servers

      • Web servers

    • One server (hardware / software) may perform one or more functions


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    File Servers

    • Offer services that allow users to share files

    • Typical operating systems

      • Novel NetWare, Windows NT

    • Services include

      • file transfer

      • file storage and data migration

      • file update synchronization

      • file archiving


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    File ServersFile Transfer

    • The ability to transfer files from one computer to another

    • Need for security (who has what access to which files)

    • Historical done by sneaker net


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    File ServersFile Storage and Data Migration

    • Vast amounts of data is stored (exabytes)

    • Must be able to efficiently manage the storage of this data

    • Categories of file storage

      • Online storage

      • Offline storage


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    File StorageOnline

    • Online storage consists mostly of hard drives

    • Online information is immediately available


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    File StorageOffline

    • Offline storage include media such as tape, optical disk

    • High capacity, low price

    • Not immediately available

    • Need for operator intervention

    • Best for rarely used data (backup)


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    File ServerFile Archiving

    • Process of backing up files on offline devices

    • Most systems backup file server data

    • Some backup client workstations

    • Usually the backup of the client (workstation) is the users responsibility


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    Print Servers

    • Manages and controls printing on the network

      • allows users to share printers

      • place printers where convenient

      • better workstation performance by using high speed data transfer, print queues and spooling

      • ability to send and receive faxes directly from the work station


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    Application Servers

    • Allow sharing of extra computing of expensive software applications that reside on a shared computer


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    Message Servers

    • Message services coordinate interactions between users, documents and applications

    • Interactions may be graphics, audio, video, etc.

    • Types of message services

      • Electronic mail

      • Workgroup applications

      • Object oriented

      • Directory services


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    Database Servers

    • Allows relatively weak clients to access powerful database capabilities

    • Usually runs in a client server model

    • Client runs interface

    • Server runs database operations such as

      • managing the database

      • processing queries


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    Network Topology

    • The way in which connections between devices in a network is called the topology


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    Network Topology Bus

    4

    1

    2

    3

    5

    • Components connected together by one or more wires

    • Passive topology no active electronics

    • Messages sent by one node are received by all

    • Only the node to which the message is addressed accepts the message


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    Network TopologyBus

    • Only one node can transmit at one time

    • A bus topology must be terminated

    • An unterminated bus will cause the signal to echo back (ringing)

    1

    2

    3

    4

    5


    Network topology bus55 l.jpg

    Network TopologyBus

    • Advantages

      • Simple, reliable in small networks

      • Easy to use

      • Requires least amount of cable

      • Easy to extend

      • Can be extended by using a repeater


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    Network TopologyBus

    • Disadvantages

      • Degrades with heavy traffic

      • Each connector weakens the signal

      • Difficult to troubleshoot


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    Network TopologyStar

    • Cables run from central hub to each computer

    • Each node communicates with central hub

    • Central hub can resend message to all nodes (broadcast star)

    • Central hub can resend only to destination node (switched star)


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    Network TopologyStar

    • Active hubs regenerate the signal

    • Active hubs and switches require power

    • Passive hubs such as wiring panels or punch down blocks act as a connection point

    • Some hubs allow more than on type of cable


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    Network TopologyStar

    • Advantages

      • Easy to modify

      • Easy to diagnose

      • Single computer failure does not affect the rest of the network

      • Use multiple types of cables


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    Network TopologyStar

    • Disadvantages

      • Central hub is a single point of failure

      • More costly


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    Network TopologyRing

    • Each computer is connected to the next in line the last computer is connected to the first

    • Most use token passing

    • Only the node with the token can send a message


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    Network TopologyRing

    • Advantages

      • Equal access to the network

      • Still functions under heavy load

    • Disadvantages

      • Failure of one computer could cause of the failure of the ring

      • Difficult to troubleshoot

      • Adding or removing a node disrupts the network

      • Usually more expensive


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    Network TopologyMesh Networks

    • Advantages

      • Fault tolerant

      • Easy to troubleshoot

    • Disadvantages

      • Cost


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    Failure of one computer could cause of the failure of the network avoided using Logical/Physical Topologies

    1

    2

    3

    4

    5

    Physical Bus  errors

    Logical Bus

    Physical Star  OK

    1

    2

    3

    4

    5


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    Failure of one computer could cause of the failure of the network avoided using Logical/Physical Topologies

    1

    5

    4

    Physical Ring  errors

    2

    3

    1

    5

    Logical Ring

    Physical Star  OK

    2

    4

    3


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    What Goes Wrong in the Network?

    • Bit-level errors (electrical interference)

    • Packet-level errors (congestion)

    • Link and node failures

    • Messages are delayed

    • Messages are deliver out-of-order

    • Third parties eavesdrop


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    Network SoftwareProtocol Hierarchies


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    Protocol Hierarchies

    • Example information flow supporting virtual communication in layer 5.


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    Connection-Oriented and Connectionless Services

    • Six different types of service.


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    Services to Protocols Relationship


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    OSI Model

    • The International Organization for Standardization (ISO) began developing the Open Systems Interconnection (OSI) model in 1977

    • It is now the most accepted standard for network modeling


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    OSI Model

    • Defines rules that apply to the following issues

      • how network devices contact each other

      • how network devices communicate with each other

      • who has the right to transmit data

      • are transmissions received correctly and by the right node


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    OSI Model

    • Defines rules that apply to the following issues

      • how physical media are arranged and connected

      • ensure that network devices maintain a proper rate of data flow

      • how bits are represented on the network media


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    OSI Model

    • Not implemented but many models very close (SNA)

    • OSI model divides tasks into seven layers

    • Layers are software and hardware standards


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    OSI Model

    • The seven layers

      • Physical

      • Data link

      • Network

      • Transport

      • Session

      • Presentation

      • Application


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    OSI Model

    • Protocol Stack

      • a group of protocols each communicating with it's neighbour

      • Layer N receives information from layer N-1 and provides information to layer N+1

      • for computers to communicate with each other both must be running the same protocol stack


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    OSI Model

    • Protocol stack

      • each layer creates / uses information used by / created by it's peer protocol

      • computers may be running different operating system but running the same protocol stack

        • ie Mac running TCP/IP communicating with DOS running TCP/IP

      • A computer may run more than one protocol stack at the same time


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    OSI Model


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    Peer Level Communication

    • Message sent from one application to another application on different hosts

      • travels down the layers of the sending machine

      • each layer adds a header to be used by it's corresponding peer level

      • bottom layer (physical) sends the message to the receiving machine


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    Peer level Communication

    • Sending Message (continued)

      • received on receiving side

      • passed up through each layer

      • each layer reads the corresponding header


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    Peer Level Communication


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    OSI Model: 7 Protocol Layers

    • Physical  how to transmit bits

    • Data link  how to transmit frames

    • Network  how to route packets to the node

    • Transport  how to send packets to the application

    • Session  manage connections

    • Presentation  encode/decode msgs, security

    • Application  everything else!


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    Physical Layer

    • Physical is responsible for sending bits from one computer to another

    • Is not concerned with the meaning of the bits

    • Defines electrical details (what represents a 0 or 1)

    • Mechanical connections shape and number of connector


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    Physical Layer

    • What signals are sent on which pins

    • Devices at the physical layer

      • Simple Hubs (passive and active)

      • Couplers , T connectors, terminators, cables, and cabling, repeaters

      • Transceivers on the (NIC)

      • Repeaters, multiplexers


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    Physical Layer

    • The following are addressed at the physical layer

      • Network connections

        • multipoint, point to point

      • Physical topologies

        • bus, star, or ring

      • Analog / digital signaling

      • Bit synchronization

      • Baseband / Broadband

      • Multiplexing


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    Data Link Layer

    • Provides for error free transfer of FRAMES over a single link from one device to another

    • Link

      • the circuit established between two adjacent nodes, with no intervening nodes

    • Path

      • a group of links that allows a message to move from origin to destination


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    Links and paths


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    Data Link Layer

    • Adds Cyclic Redundancy Check (CRC) to detect damaged frames

    • Adds control information

      • frame type

      • segmentation details

    • Detects when a frame is lost and asks for retransmission


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    Data Link Layer

    • Broadcast networks

      • all devices on the LAN receive the data transmission

    • Point to Point

      • only the destination computer receives the message

    • Uses physical address (NIC ID)


    Data link layer90 l.jpg

    Data Link Layer

    • Split into two sublayers

      • Media Access Control (MAC)

        • Controls how devices share the same media

      • Logical Link Control (LLC)

        • establishing and maintaining links between communicating devices

          • synchronization

          • flow control

          • error checking


    Data link layer91 l.jpg

    Data Link Layer

    • Devices

      • Bridges

      • intelligent hubs

      • NICs


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    Network Layer

    • Makes routing decisions for devices that are farther than one link away

    • Translates logical address into physical address

    • Routers work at the network layer

    • Example: IP addressing


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    Transport Layer

    • Responsible for process to process (end to end) delivery of messages

    • Breaks messages into segments

    • Can be Connection-type or Connection-less. Example: TCP or UDP


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    Session Layer

    • Allows applications on different computers to share a connection

    • Provides for checkpoints (if a connection is lost only the required info is resent

    • Dialog control who can transmit


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    Presentation Layer

    • Handles the format of the data

      • protocol conversion

      • data translation (ASCII)

      • Compression

      • Encryption


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    Application Layer

    • Provides services to support user applications such as

      • FTP (file transfer)

      • TELNET (remote login)

      • SMTP (simple mail transfer protocol ) e-mail


    Osi model97 l.jpg

    OSI Model


    Slide98 l.jpg

    A

    Subnet 2

    Subnet 1

    B

    Subnet 4

    Gateway

    Subnet 3

    Subnet 2

    Router

    Node

    Subnet 1


    Slide99 l.jpg

    Node

    Application

    AP

    Creates a new end point; allocates table space for it within the transport layer

    Socket

    interface

    Identification of application (port #)

    Transport

    Identifies the node

    Network

    Data Link

    Frames

    NA

    NIC card; identified by NIC card address


    Slide100 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    Buffer 

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    Data Link

    NA0

    NA1


    Slide101 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    hello

    Buffer 

    Buffer 

    hello

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    Data Link

    NA0

    NA1


    Slide102 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    Buffer 

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    AP1

    AP0

    hello

    Transport

    Network

    Network

    Data Link

    Data Link

    NA0

    NA1


    Slide103 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    Buffer 

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Node 1

    Node 0

    Network

    Network

    AP1

    AP0

    hello

    Data Link

    Data Link

    NA0

    NA1


    Slide104 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    Buffer 

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    Node 1

    Node 0

    Data Link

    AP1

    AP0

    hello

    NA0

    NA1

    Is Node 1 in my subnet?

    YES


    Slide105 l.jpg

    Node 0

    Node 1

    AP1

    AP0

    Buffer 

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    NA1

    NA0

    Node 0

    Node 1

    Data Link

    AP1

    AP0

    hello

    NA0

    NA1


    Slide106 l.jpg

    Node 0

    Node 1

    AP0

    AP1

    Buffer 

    hello

    hello

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    Data Link

    NA0

    NA1

    NA1

    NA0

    Node 1

    Node 0

    AP1

    AP0

    hello


    Slide107 l.jpg

    Node 0

    Node 1

    AP1

    AP0

    hello

    Buffer 

    Buffer 

    Socket

    interface

    Socket

    interface

    Transport

    Transport

    Network

    Network

    Data Link

    Node X

    Node 0

    Data Link

    AP1

    AP0

    hello

    NA0

    Is Node X in my subnet?

    NA1

    NO

    Call ROUTER


    Slide108 l.jpg

    Backbone

    Routing Tables

    Router

    Routing tables

    Subnet 30

    Node X

    Router

    Node 0

    Node 1

    NAR0

    Subnet 20

    NAR0

    NA0

    Node X

    Node 0

    AP1

    AP0

    hello


    Slide109 l.jpg

    Gateway

    Backbone

    Router

    Routing Tables

    Subnet 30

    Router

    Node 0

    Node 1

    Subnet 20


    Reference models l.jpg

    Reference Models


    Reference models tcp ip l.jpg

    Reference ModelsTCP / IP

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


    Slide112 l.jpg

    TCP/IP Model  The Internet Layer

    Packet-switching network based on a connectionless internetwork layer

    Permit hosts to inject packets, independent travel to destination

    Official packet format and protocol: IP (Internet Protocol)

    IP packets delivered where they are supposed to go


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    TCP/IP Model  The Transport Layer

    Allows peers on the source and destination hosts to carry on a conversation.

    Protocols: TCP and UDP

    TCP (Transmission Control Protocol)  reliable, connection-oriented, error-free byte stream delivering; handles flow control

    UDP (User Datagram Protocol)  unreliable, connectionless; No TCP’s flow control; applications where prompt delivery more important than accurate delivery (speech, video, …)


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    IEEE

    • Institute of Electrical and Electronic Engineers defined standards relating to the physical cabling and data transmission relating to the physical and Data Link layers

    • 802.x standards


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    Example Networks

    • The Internet

    • Connection-Oriented Networks: X.25, Frame Relay, and ATM

    • Ethernet

    • Wireless LANs: 802:11


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    Architecture of the Internet

    • Overview of the Internet.


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    ATM Virtual Circuits


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    ATM Virtual Circuits (2)

    • An ATM cell.


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    The ATM Reference Model

    • The ATM reference model.


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    The ATM Reference Model


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    Ethernet


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    Wireless LANs

    • (a) Wireless networking with a base station.

    • (b) Ad hoc networking.


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    Wireless LANs (2)


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    Wireless LANs (3)


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