Layered Architecture


          Anjan.K
     II Sem M.Tech
       Dept of CSE
         M.S.R.I.T



           05/01/09  ...
Outline
  Layered Architecture
    • Need For Layering
    ◦OSI Reference Model
    ◦TCP/IP Model
    ◦Problems
    ◦Sock...
Need For Layering
    Allows Complex problems are decomposed in to
     small manageable units.
    Implementation detai...
The ISO/OSI Reference Model
 Physical                            Need For Standard Architecture is various
  • Transmit r...
TCP/IP Reference Model
 Also called the Internet
  Architecture
 No Strict enforcement of
  layering
 Usually shown as ...
Problem
   Suppose that the TCP entity receives a                                      1.5MB File
    1.5 megabyte file f...
Application Programming Interfaces(API)- Sockets

  API are required to implement an Network application
  Socket interf...
Socket System Calls
 Create a socket
   int socket(int family, int type, int protocol);
 Bind –binds socket to local add...
Socket Calls




           TCP Socket Calls                              UDP Socket Calls
Copyright © Communication Netwo...
Application Protocol Examples
Application          Protocol                   Underlying
                                 ...
File Transfer Protocol (FTP) [RFC 959]
    FTP client contacts FTP server at                          TCP control
     po...
IP Utilities
 PING                             TRACEROUTE – debugging tool
  ◦ Determines whether a host        ◦ Used t...
Summary
 Layered Architecture
   ◦ OSI Reference Model
   ◦ TCP/IP Model
   ◦ Socket Programming with Demo
       ◦ TCP
 ...
References
[1] Larry L Peterson, “Communication
    Networks”,3rd Edition
[2] S.keshav, “An Engineering Approach to
    Co...
Layered Architecture
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  • Layered Architecture

    1. 1. Layered Architecture Anjan.K II Sem M.Tech Dept of CSE M.S.R.I.T 05/01/09 MCSE201 : Communication Network 1
    2. 2. Outline  Layered Architecture • Need For Layering ◦OSI Reference Model ◦TCP/IP Model ◦Problems ◦Socket Programming ◦ TCP ◦ UDP ◦ Sockets Demo  Applications FTP • IP Utilities 05/01/09 MCSE201 : Communication Network 2
    3. 3. Need For Layering  Allows Complex problems are decomposed in to small manageable units.  Implementation details of the layer are abstracted. Separation of implementation and specification  Layers are work as one by sharing the services provided by each other.  Layering allows reuse functionality i.e., lower layers implement common once.  Provide framework to implement multiple specific protocols per layer 05/01/09 MCSE201 : Communication Network 3
    4. 4. The ISO/OSI Reference Model  Physical Need For Standard Architecture is various • Transmit raw bits over the vendors with various architectures. Hence ISO: medium. International Standards Organization  Data Link ( (Estd in 1947) ◦ Abstraction of an error free OSI: Open Systems Interconnection m medium (frame) ( (1970’s) ◦ Flow Control  Network ◦ Routing (Packets) R End host End host ◦ Addressing (IP address) A Application Application  Transport ◦ Error free end to end, type of Presentation Presentation service ◦ Port Addresses Session Session  Session Transport Transport ◦ establishing Sessions, ◦ dialog Control & token Network Network Network Network management Data link Data link  Presentation - Handles Syntax and Data link Data link semantics Physical Physical Physical Physical  Application- Protocols commonly needed by applications (http,ftp ,etc.,). One or m nodes w ore ithin the network Copyright © Computer Networks by Larry Peterson 05/01/09 MCSE201 : Communication Network 4
    5. 5. TCP/IP Reference Model  Also called the Internet Architecture  No Strict enforcement of layering  Usually shown as a 4 or 5 layer model Copyright © Communication Networks by Leon Garcia 05/01/09 MCSE201 : Communication Network 5
    6. 6. Problem  Suppose that the TCP entity receives a 1.5MB File 1.5 megabyte file from the application Application layer and that the IP layer is willing to carry blocks of maximum size 1500 bytes. Calculate the amount of 1.5MB File overhead incurred from segmenting the file into packet-sized units.  Solution: • MTU=1500 MSS= 1460 MTU 1 MSS+ MTU 2 ……….. MTU 1028 • 1.5 Mbyte / 1460 byte = 1027.4, Header therefore 1028 blocks are needed to transfer the file. • Overhead = ((1028 x 1500 - 1.5M)/1.5M) x 100 = 2.8% Copyright © Communication Networks by Leon Garcia 05/01/09 MCSE201 : Communication Network
    7. 7. Application Programming Interfaces(API)- Sockets  API are required to implement an Network application  Socket interface, part of Berkeley Unix, is now supported by all OS.  Socket - point where a local abstraction process attaches to the network.  Interface defines operations ◦ Creating a socket ◦ Attaching the socket to the network, ◦ Sending/Receiving messages and ◦ closing the socket. 05/01/09 MCSE201 : Communication Network 7
    8. 8. Socket System Calls  Create a socket int socket(int family, int type, int protocol);  Bind –binds socket to local address int bind(int socket,struct sockaddr *address, int addr.len);  Listen defines how many connections can be pending int listen(int socket,int backlog);  Accept carries out the passive operation int accept( int socket,struct sockaddr *address,int a addr.len) int connect(int socket,struct sockaddr *address, int addr.len); int send(int socket, char *message, int msg.len, int flags); int recv(int socket, char *buffer, int buf.len, int flags); 05/01/09 MCSE201 : Communication Network 8
    9. 9. Socket Calls TCP Socket Calls UDP Socket Calls Copyright © Communication Networks by Leon Garcia 05/01/09 MCSE201 : Communication Network 9
    10. 10. Application Protocol Examples Application Protocol Underlying Transport Protocol Electronic Mail SMTP [RFC 2821] TCP Web HTTP [RFC 1945] TCP File Transfer FTP [RFC 959] TCP Streaming RTP [RFC 1889] TCP/UDP Multimedia Internet Telephony SIP [RFC 3261] UDP Remote terminal Telnet [RFC 854] TCP access Name Domain DNS[RFC 883] UDP server 05/01/09 MCSE201 : Communication Network 11
    11. 11. File Transfer Protocol (FTP) [RFC 959]  FTP client contacts FTP server at TCP control port 21, specifying TCP as transport connection protocol port 21  Client obtains authorization over FTP control connection FTP client  Client browses remote directory by server sending commands over control TCP data connection connection. port 20  When server receives a command for a file transfer, the server opens a TCP data connection to client  After transferring one file, server closes connection. 05/01/09 MCSE201 : Communication Network 12
    12. 12. IP Utilities  PING  TRACEROUTE – debugging tool ◦ Determines whether a host ◦ Used to track route of packet is online and available and from local host to remote host make use of ICMP messages ◦ Informs about latency and ◦ Inform the sending host reachability about errors in IP datagram ◦ Makes use of both ICMP and UDP ◦ Used to measure round-trip  IPCONFIG delay between hosts  NETSTAT ◦ Utility to display TCP/IP information about a host ◦ Queries about its TCP/IP available in Windows network status ◦ Simplest form returns IP ◦ Finds status of network address, subnet mask, default drivers and their interface gateway, DNS servers cards ◦ Available with various options 05/01/09 MCSE201 : Communication Network 13
    13. 13. Summary  Layered Architecture ◦ OSI Reference Model ◦ TCP/IP Model ◦ Socket Programming with Demo ◦ TCP • UDP  Applications ◦ FTP ◦ IP Utilities 05/01/09 MCSE201 : Communication Network 14
    14. 14. References [1] Larry L Peterson, “Communication Networks”,3rd Edition [2] S.keshav, “An Engineering Approach to Computer Networking”,Pearson Education [3] Andrew.S Tannenbaum, “Computer Network”, 4th Edition [4] Leon Garcia et.al., “Communication Networks”, 2nd Edition [5] RFC’s From http://www.ietf.org [6] Leslie Miller, “ISO Reference Model of OSI” ACM transaction in Nov 1981 05/01/09 MCSE201 : Communication Network 15
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