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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
CPSC441

Computer Communication

what this course is about
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.
topics
Topics
  • INTRODUCTION
  • PHYSICAL LAYER
  • DATA LINK LAYER
  • NETWORK LAYER
  • TRANSPORT LAYER
  • APPLICATION LAYER
  • TCP/IP SECURITY
topics4
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
topics5
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
topics6
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
topics7
Topics
  • INTRODUCTION
  • PHYSICAL LAYER
  • DATA LINK LAYER
  • NETWORK LAYER
      • ROUTING, ROUTING PROTOCOLS
      • IP ADDRESSING, SUBNETS, NETMASK
  • TRANSPORT LAYER
  • APPLICATION LAYER
  • TCP/IP SECURITY
topics8
Topics
  • INTRODUCTION
  • PHYSICAL LAYER
  • DATA LINK LAYER
  • NETWORK LAYER
  • TRANSPORT LAYER
      • TCP, UDP protocols
      • SOCKET PROGRAMMING
  • APPLICATION LAYER
  • TCP/IP SECURITY
topics9
Topics
  • INTRODUCTION
  • PHYSICAL LAYER
  • DATA LINK LAYER
  • NETWORK LAYER
  • TRANSPORT LAYER
  • APPLICATION LAYER
      • Domain Name Service (DNS)
      • BASIC INTERNET SERVICES
  • TCP/IP SECURITY
topics10
Topics
  • INTRODUCTION
  • PHYSICAL LAYER
  • DATA LINK LAYER
  • NETWORK LAYER
  • TRANSPORT LAYER
  • APPLICATION LAYER
  • TCP/IP SECURITY
      • INTRO TO CRYPTOGRAPHY
      • Secure Socket Layer (SSL)
      • FIREWALLS
quotes
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
history of data communications
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.
history of data communications13
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.
history of data communications14
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)
historical events
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
historical events16
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
historical events17
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
historical events18
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))
historical events19
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
historical events20
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
data communications
Data Communications

Data Communications

Terminal to Computer

Computer to Computer

Local Area Networks

Wide Area Networks

Peer to Peer

Client Server

pc as an information tool
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)
pc as an information tool23
PC as an Information Tool
  • Wide Area Network (WAN)
    • connection of LANs
    • connected by wire, microwave, satellite
resource sharing
Resource Sharing
  • Sharing of Information
    • Types
      • Mission critical data
      • Frequently used data (form letters)
      • Policy / procedure manuals
    • Who needs what access
      • update
      • read only
information sharing
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
hardware sharing
Hardware Sharing
  • Allows sharing of devices such as:
    • Printers
    • Fax modems
    • Scanners
    • Disk drives
    • CD ROM\'s
    • Tape Backup units
    • Plotters
software sharing
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
software sharing28
Software Sharing
  • License considerations
    • single user
    • license per user
    • site license
backup
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
computer roles in a network
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
operating systems
Operating systems
  • Server
    • Novel NetWare
    • Windows NT
  • Client
    • Windows 2000
    • DOS
    • OS/2
  • Peer
    • Windows 2000
categories of networks
Categories of Networks
  • Client / Server
    • contains clients and supporting servers
    • may be dedicated or non dedicated
    • server centric
    • network centric
categories of networks33
Categories of Networks
  • Peer to Peer
    • network of computers sharing resources with no dedicated server
server based networks
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
server based networks35
Server Based Networks
  • Disadvantages
    • Expensive hardware
    • Expensive software
    • Dedicated network administrator
peer to peer
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
peer to peer37
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
peer security server security
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
home network applications 2
Home Network Applications (2)
  • In peer-to-peer system there are no fixed clients and servers.
selecting the network type
Selecting the Network type
  • Cost
  • Expertise
  • Security issues
  • Number of work stations
  • Types of applications
types of servers
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
file servers
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
file servers file transfer
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
file servers file storage and data migration
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
file storage online
File StorageOnline
  • Online storage consists mostly of hard drives
  • Online information is immediately available
file storage offline
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)
file server file archiving
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
print servers
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
application servers
Application Servers
  • Allow sharing of extra computing of expensive software applications that reside on a shared computer
message servers
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
database servers
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
network topology
Network Topology
  • The way in which connections between devices in a network is called the topology
network topology bus
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
network topology bus54
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
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
network topology bus56
Network TopologyBus
  • Disadvantages
    • Degrades with heavy traffic
    • Each connector weakens the signal
    • Difficult to troubleshoot
network topology star
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)
network topology star58
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
network topology star59
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
network topology star60
Network TopologyStar
  • Disadvantages
    • Central hub is a single point of failure
    • More costly
network topology ring
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
network topology ring62
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
network topology mesh networks
Network TopologyMesh Networks
  • Advantages
    • Fault tolerant
    • Easy to troubleshoot
  • Disadvantages
    • Cost
slide64

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

slide65

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

what goes wrong in the network
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
protocol hierarchies
Protocol Hierarchies
  • Example information flow supporting virtual communication in layer 5.
osi model
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
osi model72
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
osi model73
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
osi model74
OSI Model
  • Not implemented but many models very close (SNA)
  • OSI model divides tasks into seven layers
  • Layers are software and hardware standards
osi model75
OSI Model
  • The seven layers
    • Physical
    • Data link
    • Network
    • Transport
    • Session
    • Presentation
    • Application
osi model76
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
osi model77
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
peer level communication
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
peer level communication80
Peer level Communication
  • Sending Message (continued)
    • received on receiving side
    • passed up through each layer
    • each layer reads the corresponding header
osi model 7 protocol layers
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!
physical layer
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
physical layer84
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
physical layer85
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
data link layer
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
data link layer88
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
data link layer89
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
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
Data Link Layer
  • Devices
    • Bridges
    • intelligent hubs
    • NICs
network layer
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
transport layer
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
session layer
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
presentation layer
Presentation Layer
  • Handles the format of the data
    • protocol conversion
    • data translation (ASCII)
    • Compression
    • Encryption
application layer
Application Layer
  • Provides services to support user applications such as
    • FTP (file transfer)
    • TELNET (remote login)
    • SMTP (simple mail transfer protocol ) e-mail
slide98

A

Subnet 2

Subnet 1

B

Subnet 4

Gateway

Subnet 3

Subnet 2

Router

Node

Subnet 1

slide99

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

Node 0

Node 1

AP0

AP1

Buffer 

hello

Buffer 

Socket

interface

Socket

interface

Transport

Transport

Network

Network

Data Link

Data Link

NA0

NA1

slide101

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

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

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

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

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

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

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

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

Gateway

Backbone

Router

Routing Tables

Subnet 30

Router

Node 0

Node 1

Subnet 20

reference models tcp ip
Reference ModelsTCP / IP
  • Protocols and networks in the TCP/IP model initially.
slide112

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

slide113

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, …)

slide114
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
example networks
Example Networks
  • The Internet
  • Connection-Oriented Networks: X.25, Frame Relay, and ATM
  • Ethernet
  • Wireless LANs: 802:11
architecture of the internet
Architecture of the Internet
  • Overview of the Internet.
the atm reference model
The ATM Reference Model
  • The ATM reference model.
wireless lans
Wireless LANs
  • (a) Wireless networking with a base station.
  • (b) Ad hoc networking.
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