CSE 422 Computer Networks - PowerPoint PPT Presentation

Loading...

PPT – CSE 422 Computer Networks PowerPoint presentation | free to download - id: 8984f-ZDc1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

CSE 422 Computer Networks

Description:

2. Technology ... Views on politics, religion, sex, etc. distributed. Newsgroups debate ... 10km City Metropolitan Area. 100km Country (Wide Area) Network. 1, ... – PowerPoint PPT presentation

Number of Views:75
Avg rating:3.0/5.0
Slides: 64
Provided by: CSE136
Learn more at: http://www.cse.msu.edu
Category:
Tags: cse | computer | networks

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: CSE 422 Computer Networks


1
CSE 422Computer Networks
  • CSE 422

2
Technology Over The Centuries
  • 18th Century Mechanical Systems Accompanying The
    Industrial Revolution
  • 19th Century Age of The Steam Engine
  • 20th Century Information Gathering, Processing,
    and Distribution e.g.,
  • Worldwide Telephone Network
  • Invention of Radio and TV
  • Computer Industry
  • Launching of Communication Satellites

3
Internet Growth (by Number of Computers)
4
Computer Networks
  • Definition
  • Interconnected Collection of Autonomous Computers
  • Goals
  • Resource Sharing
  • Lower Communication Costs
  • Client-Server Model
  • High Reliability
  • Communication Medium Among Widely Separated
    People
  • Smooth System Growth
  • Simpler Software Design

5
Applications of Networks
  • Access to Remote Programs
  • Simulation
  • Computer Aided Ed.,
  • Medical Diagnosis
  • Access to Remote Data Bases
  • Reservations For Hotels, Airplanes
  • Home Banking
  • Automated Newspaper
  • Automated Library
  • Access to Information System (e.g. World Wide
    Web)

6
Applications of Networks (cont.)
  • Communication Medium
  • Electronic Funds Transfer System
  • Electronic Mail
  • Teleconferencing
  • Worldwide Newsgroups
  • International Contacts by Humans
  • Entertainment Industry
  • Video On Demand
  • Multiperson real-time simulation games
  • Selecting any movie/TV program ever made
  • Live TV may becomes interactive with audience

7
Social Issues
  • Views on politics, religion, sex, etc.
    distributed
  • Newsgroups debate sensitive issues
  • Network operators risk being sued for contents
  • Rights to free speech may be violated
  • Anonymous messages can be desirable, but ...

8
Classification of interconnected processors by
physical size
9
Network Structure
  • Communication Subnet (Subnet)
  • Switching Elements (Routers)
  • Transmission Lines (Circuits)

10
Types of Design For Subnets
  • Point-to-Point Circuits (Channels)
  • Example of Topologies

Some possible topologies for a point-to-point
subnet (a) Star (b) Loop (c) Tree (d) Complete
(e) Intersecting loops (f) Irregular
11
Types of Design For Subnets (cont.)
  • Broadcast Channels
  • Examples of Topologies

Communication subnet using broadcasting (a) Bus
(b) Satellite or Radio (c) Ring
12
Types of Design For Subnets (cont.)
  • Note Broadcast Subnets May Allocate Channel By
  • 1. Static Methods
  • TDMA
  • 2. Dynamic Methods
  • Centralized
  • Decentralized

13
Summary of Network types -LANs, MANs, WANs
  • Local area networks (LANs)-are privately owned
    networks within a single building or campus of up
    to a few kilometers in size
  • LANs-have three distinguished characteristics
    (1) size, (2) transmission technology, (3)
    topology
  • Metropolitan area networks (MANs)-basically a
    larger version of LANs, and uses similar
    technology
  • MAN-has just one or two cables and contains no
    switching elements

14
Network Types (Cont.)-LANs, MANs, WANs
  • MAN standard-Distributed Queue and Dual Bus
    (DQDB), consists of two unidirectional buses
    (cables) to which all computers are
    connected
  • WAN-spans a large geographical area it consists
    of several hosts, connected to a subnet, which in
    turn is connected via transmission lines and
    switching elements

15
Network Types (Cont.)-LANs, MANs, WANs
  • Architecture of DQDB metropolitan area network

16
Network Types (Cont.)-Wireless Networks
  • Mobile computing, (e.g., notebook computers
    portable digital assistants (PDA) is growing at a
    rapid rate)
  • Users want network connectivity in cars,
    airplanes, other remote sites
  • The use of a portable computer capable of
    wireless networking will very likely
    revolutionize the way we use computers
  • Possible uses portable office, fleets of trucks,
    taxis, buses, and repairpersons (keeping in
    contact with home)

17
Network Types (Cont.)-Wireless Networks
  • Other uses workers at disaster sites (fires,
    floods, etc.) where telephone system is
    destroyed military operations
  • Some disadvantages low bandwidth (1-2 Mbps),
    high error rates, frequent disconnections
  • Wireless networks communicate via modulating
    radio waves or pulsing infrared light
  • Wireless communication linked to wired network
    infrastructure by transceivers

18
Network Types (Cont.)-Wireless Networks
  • Cell-
  • area cover by an individual transceiver's
    signal the cell sizes vary widely
  • Wireless networks comes in many forms. Some
    universities have installed antennas all over
    campus to allow students to access the library
    card catalog, while sitting under the trees
  • Security is a problem, because connection to
    wireless is so easy challenge for software
    designers
  • Address migration also presents a challenge

19
Examples of Networks
  • Commercial Networks
  • DECNET
  • SNA
  • National Network
  • ARPANET
  • NREN
  • EDUNET
  • USENET

20
Examples of Networks (cont.)
  • Local Area Networks
  • NOVELL NETWARE
  • MAP and TOP
  • Packet Carriers
  • TYMNET
  • TELENET

21
The Internet Emerges-funded by ARPA
  • Need to interconnect LANs, MANs, and WANs
  • Initially interconnected NSFNET and ARPANET
  • Results Internet, with TCP/IP Software
  • Growth continues exponentially, doubles each yr.
  • Main applications Email, Remote Login, News,
    File Transfer
  • New application WWW, with Internet Explorer,
    further increased the Internet usage

22
Data Communications Organizations
  • ISO CCITT
  • ANSI State Dept.
  • EIA
  • Carriers Other NTIA
  • NCS Org.
  • Government Agencies

23
A Simplified Architecture for File Transfer
Computer X
Computer Y
File transfer application
File transfer application
File and file transfer command
Communications Service module
Communications Service module
Communications-related data units
Network access Module
Network access Module
Network interface logic
Network interface logic
24
Network Architectures
  • Protocols
  • Layers

25
The ISO Reference Model (Basic Principles)
  • 1. A layer should be created where a different
    level of abstraction is needed.
  • 2. Each layer should perform a well defined
    function.
  • 3. The function of each layer should be chosen
    with an eye toward defining internationally
    standardized protocols.

26
The ISO Reference Model (Basic Principles)
(cont.)
  • 4. The layer boundaries should be chosen to
    minimize the information flow across the
    interfaces.
  • 5. The number of layers should be large enough
    that distinct functions need not be thrown
    together in the same layer out of necessity, and
    small enough that the architecture does not
    become unwieldy.

27
Design Issues For The Layers
  • Mechanism For Connection Establishment
  • Mechanism For Connection Termination
  • Rules for Data Transfer
  • Simplex
  • Half Duplex
  • Full Duplex
  • Error Control
  • Properly Sequencing Messages

28
Design Issues For The Layers (cont.)
  • Flow Control
  • Routing
  • Multiplexing Conversations
  • Mechanism For Handling Arbitrarily Long Messages

29
Layers, protocols, and Interfaces
30
Example information flow supporting virtual comm.
in layer 7.
31
Physical Layer
  • Concerned with Transmitting Raw Bits over a
    Communication Channel.
  • Design Issues
  • Mechanical, Electrical, Procedural Interfacing to
    Subnet
  • Implemented in Hardware

32
Data Link Layer
  • Takes a Raw Transmission Facility Transforms It
    To a Line Which Appears Free of Transmission
    Errors to The Network Layer.
  • Breaks Input Data Into Frames, Transmitting
    Frames Sequentially, Process Acknowledgment
    Frames.
  • Design Issues
  • Solve Problems Caused By Damaged, Lost, or
    Duplicate Frames.
  • How to Keep Fast Transmitters From Drowning Slow
    Receiver.

33
Network Layer --- Communication Subnet Layer
  • Determines Chief Characteristics of IMP Host
    Interface How Packets Are Routed Within The
    Subnet.
  • Software Accepts Messages From The Source Host,
    Converts Them To Packets, See That Packets Are
    Routed Correctly.

34
Network Layer --- Comm. Subnet Layer (cont.)
  • Design Issues
  • The Division of Labor Between The IMPs The Host
    (i.e., Who Should Ensure That All Packets Are
    Correctly Received at Their Destination, in
    Proper Order.)
  • How The Route is Determined? By Using Static
    Tables, Dynamic Tables, or ?
  • Implemented in Host by I/O Drivers

35
Transport Layer --- Host to Host Layer
  • Provides a flow of data between two hosts, for
    the application layer above.
  • Accepts Data From Session Layer, Splits It Into
    Smaller Units, If Needed, Passes to Network
    Layer, Ensures That All Pieces Arrive Correctly
    at Other End.
  • Determines The Type of Service Provided to The
    Session Layer. e.g.,
  • Error --- Free (Virtual) Point-to-Point Channel
    That Delivers Messages in The Order They Were
    Sent.

36
Transport Layer --- Host to Host Layer (cont.)
  • Transport of Isolated Messages With No Guarantee
    About The Order of Delivery.
  • Broadcasting of Messages to Multiple
    Destinations.
  • Design Issues
  • Mechanism to Regulate The Flow of Information
    From One Host to Another.
  • Determine Which Message Belongs to Which
    Connection.
  • Implemented as Part of The Host OS.

37
Session Layer --- User Interface Layer
  • User Negotiate to Establish a Connection with a
    Process on Another Machine.
  • Manages The Session Once It Has Been Set Up,
    (e.g., If Transport Connections are Unreliable,
    The Session Layer May Be Required To Recover From
    Broken Transport Connections.)
  • Implemented as Part of The OS.

38
Presentation Layer
  • Represents Information to Communication
    Application-Entities In a Way That Preserves
    Meaning While Resolving Syntax Differences.
    Typical Functions Include
  • Text Compression
  • Encryption for Security
  • Syntax Selection
  • Conversion Between Character Codes (e.g., ASCII
    to EBCDIC)

39
Application Layer
  • Based on Request From User, This Layer Selects
    Appropriate Services To Be Supplied From Lower
    Layers. e.g.
  • Identification of Intended Communication Partners
    Their Availability Authenticity.
  • Determination of Cost Allocation Methodology.
  • Establishment of Error Recovery Responsibility.
  • Agreement on Required Privacy.

40
Application Layer (cont.)
  • Design Issues
  • Problem of Partitioning to Gain Maximum Advantage
    of Network.
  • Questions of Network Transparency, Hiding The
    Physical Distribution of Resources From The User.

41
Approximate correspondences between the various
networks
42
A Critique of the OSI Model and Protocols
  • Bad timing
  • Bad technology
  • Bad implementation
  • Bad Politics

43
A Critique of the TCP/IP Reference Model
  • Does not distinguish concepts of service,
    interface, and Protocol clearly
  • Not at all general, poorly suited to describing
    any other protocol stack
  • Host-to-network layer is not really a layer, but
    an interface between the network and the
    data-link layers
  • Does not distinguish between physical and data
    link layers
  • IP and TCP were well thought out, but the other
    protocols were ad hoc

44
Relation Between Layers at an Interface
In order to transfer the SDU, the layer N entity
may have to fragment it into several pieces, each
of which is given a header and sent as a
separate PDU such as a packet
45
Layering of TCP/IP-based protocols
46
Six different types of services
  • Service Example
  • Reliable message stream Sequence of
    pages
  • Reliable byte stream Remote login
  • Unreliable connection Digitized voice
  • Unreliable datagram Electronic junk
    mail
  • Acknowledged datagram Registered mail
  • Request-reply Database query

Connection- oriented
Connection- less
47
Service Primitives
request
response
Layer N1
2
4
Layer N
1
3
confirm
indication
Physical channel
Host 1
Host 2
48
Service Primitives (cont.)
  • Request An entity wants the service to do some
    work
  • Indication An entity is to be informed about an
    event
  • Response An entity wants to respond to an event
  • Confirm An entity is to be informed about its
    request

49
Service Primitives (cont.)
  • To make the concept of a service more concrete,
    let us consider as an example a simple
    connection-oriented service with eight service
    primitives as follows
  • 1. CONNECT.request --- Request a connection to be
    established.
  • 2. CONNECT.indication --- Signal the called
    party.
  • 3. CONNECT.response --- Used by the callee to
    accept/reject calls.
  • 4. CONNECT.confirm --- Tell the caller whether
    the call was accepted.

50
Service Primitives (cont.)
  • 5. DATA.request --- Request that data be sent.
  • 6. DATA.indication --- Signal the arrival of
    data.
  • 7. DISCONNECT.request --- Request that a
    connection be released.
  • 8. DISCONNECT.indication --- Signal the peer
    about the request.
  • In this example, CONNECT is a confirmed service
    (an explicit response is required) whereas
    DISCONNECT is unconfirmed (no response).

51
Example Data Communication Services
  • Switched Multimegabit Data Services
    (SMDS)-connecting LANs
  • SMDS is designed to handle bursty traffic
  • SMDS service simple connectionless packet
    service
  • A useful feature of SMDS is broadcasting
  • Another useful feature is address screening on
    both incoming outgoing packets

52
Example Data Communication Services (cont.)
53
Data Commun. Services (Cont.)- X.25 Networks
  • Standard developed during the 1970s by CCITT
  • Provides an interface between public packet
    networks their customers
  • X.25 comprises the physical layer, the data link
    layer the network layer
  • X.25 is connection-oriented supports both
    switched virtual circuits permanent ones
  • Provides ACKs and flow control

54
Data Commun. Services (Cont.)-X.25 Networks
  • Note some older terminals still do not speak
    X.25 need yet another way to connect (Packet
    Assembler Disassembler)
  • Multiplexing switching of logical connections
    take place in layer 3
  • Call control signaling is carried on the same
    logical connection as user data

55
Data Commun. Services (Cont.)-Frame Relay
  • An absolute connection-oriented service
  • Goal move bits from A to B at reasonable speed
    low cost
  • Can be thought as a virtual leased line
  • Does not provide ACKs or flow control
  • Variable size packets (Frames) may be up to 1600
    bytes
  • Designed to operate at user data rates of up to 2
    Mbps

56
Data Commun. Services (Cont.)-Frame Relay
  • Lower delay higher thru put, since internal
    processing is reduced, as is the protocol
    functionality at the user-network interface
  • Call control signaling is on a separate logical
    connection from user data
  • Multiplexing switching of logical connections
    take place in layer 2

57
Data Commun. Services (Cont.)- B-ISDN and ATM
  • Asynchronous Transfer Mode (ATM), Universal
    information carrier voice, data, video
  • ATM networks are connection-oriented
  • Example services video on demand, live TV from
    many sources, full motion multimedia E-mail,
    CD-quality music, high-speed data transport, LAN
    interconnection
  • Small fixed-sized packets (cells), 53 bytes long,
    of which 5 bytes are header 48 bytes are payload

58
Data Commun. Services (Cont.)- B-ISDN and ATM
  • ATM is called cell relay- a cell-switching
    technology
  • Cell delivery is not guaranteed, but the order is
  • Cell-switching highly flexible, can handle
    both VBR CBR traffic, digital switching of cell
    is easy via fiber optics, facilitates TV
    distribution broadcasting
  • Normal speed for ATM networks is 155 Mbps, 622
    Mbps, and gigabit speed later
  • The ATM Forum an international group that guides
    the future of ATM

59
Data Commun. Services (Cont.)- B-ISDN and ATM
60
Data Commun. Services (Cont.)- B-ISDN and ATM
  • The ATM layers and sublayers, and their functions

OSI layer
ATM layer
ATM sublayer
Functionality
Providing the standard interface(convergence)
CS
3/4
AAL
SAR
Segmentation and reassembly
Flow control cell header generation/extraction vir
tual circuit/path management Cell
multiplexing/demultiplexing
2/3
ATM
Cell rate decoupling Header checksum generation
and verification Cell generation Packing/unpacking
cells from the enclosing envelope Frame
generation
2
TC
Physical
Bit timing Physical network access
1
PMD
61
Data Commun. Services (Cont.)- B-ISDN and ATM
  • Different networking services.
  • Issue DQDB SMDS X.25
    Frame relay ATM
  • Connection oriented Yes No
    Yes Yes
    Yes
  • Normal speed(Mbps) 45 45
    .064 2
    155
  • Switched No
    Yes Yes No
    Yes
  • Fixed-size payload Yes
    No No No
    Yes
  • Max payload 44
    9188 128 1600
    48
  • Permanent VCs No
    No Yes Yes
    Yes
  • Multicasting No
    Yes No No
    Yes

62
Gigabits Testbeds
  • Michigan State University High-Speed Networking
    Performance Research Laboratory (HSNP)
  • ARPA NSF financed a number of
    university-industry gigabit testbeds
  • MIT, U of Penn., IBM Watson Lab, and Bellcore
    Aurora- (a testbed linking four sites in the
    Northeast)
  • AT\T Bell Labs, Berkley, the U of Wis Blanca-
    (research issues protocols, host interfaces, etc)

63
Gigabit Testbeds Cont.
  • Cal Tech, JPL, Los Alamos, San Diego Super
    Computer Center CASA- (aimed at doing research
    on super computer applications
  • CMU Nectar- (an experimental MAN from CMU to
    Pittsburgh, interested in applications involving
    chemical process flowsheeting Oper. Res.)
  • U of NC, NC State U, IBM Res. Triangle Park
    VISTAnet- research focuses on 3D images to plan
    radiation therapy for cancer patients)
About PowerShow.com