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TCP/IP Application Layer

TCP/IP Application Layer. Comparison between OSI and TCP/IP. Client-Server Model (many-to-one). Local machine. Remote machine. Client requests a service from a server. Client program runs when it is needed Server program runs infinitely.

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TCP/IP Application Layer

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  1. TCP/IP Application Layer

  2. Comparison between OSI and TCP/IP

  3. Client-Server Model (many-to-one) Local machine Remote machine Client requests a service from a server Client program runs when it is needed Server program runs infinitely

  4. BOOTP – client-server protocol designed to provide 4 pieces of information for a diskless computer or a computer that is booted for the first time. A computer attached to TCP/IP must know the ff. info: Its IP address Its subnet mask IP address of the router IP address of the server DHCP – extension of BOOTP Provides dynamic configuration Bootstrap Protocol (BOOTP)Dynamic Host Configuration Protocol (DHCP

  5. DNS in the Internet DNS –Domain Name System Domain name – name used instead of address 3 sections of domain name space (tree)

  6. Generic Domains • Define registered hosts • according to their • generic behavior • 1st level label (3 character) • Organization types

  7. Country Domains De Anza College in Cupertino in California in the United States

  8. Inverse Domain Map an address to a name Server list an IP address of authorized clients. Client sends a query to DNS Server

  9. Popular client-server application program Enables the establishment of a connection to remote system in such a way that the local terminal appears to be a terminal at the remote system. TERminal Network (TELNET)

  10. Local Login Keystrokes are accepted by the terminal driver Pass the characters to OS OS interprets the combination of characters and invokes the application program

  11. Remote Login Transform the characters to a universal character set Network virtual terminal characters (NVT) Arrives at the TCP/IP stack Delivered to OS thru pseudoterminal driver OS does not interpret the characters

  12. Concept of NVT Network Virtual Terminal (NVT) - universal interface UNIX Ctrl+z – suspend Ctrl+c – abort Ctrl+d – end-of-file DOS Ctrl+z – end-of-file

  13. Client TELNET translates characters to NVT form Server TELNET translates NVT form into characters acceptable by the remote computer.

  14. FTP - the standard mechanism provided by TCP/IP for copying a file from one host to another. 3 components of Client Control connection – remains connected Data connection – open and then closed for each file transferred

  15. -less funtionalities than FTP ex. Diskless workstation or a router is booted, we need to download the bootstrap and configuration file Trivial File Transfer Protocol (TFTP)

  16. SMTP Concept • Simple Mail Transfer Protocol • supports e-mail • Sending single message to 1 or more recipients • Sending messages that include text, voice, video, graphics • Sending messages to users on networks outside the internet

  17. UAs and MTs User Agent & Mail Transfer Agent

  18. Relay MTAs

  19. Mail Gateways Does not use TCP/IP

  20. E-mail Address

  21. MIME

  22. POP3 and SMTP

  23. SNMP Concept Simple Network Management Protocol - for monitoring and maintaining an internet Manager – management stations - runs the SNMP client program Agent – managed station - routers/hosts that runs the SNMP server program

  24. The agent keeps performance information in a database. Ex. # of packets received and forwarded The manager can also make the router perform certain actions Ex. Reboot the agent remotely at any time.

  25. Management with SNMP is based on 3 basic ideas: A manager checks an agent by requesting information that reflects the behavior of the agent. A manager forces an agent to perform a task by resetting values in the agent database. An agent contributes to the management process by warning the manager of the unusual situation.

  26. Internet Management Components Structure of Management Information (SMI) Its functions are to name objects; to define the type of data that can be stored in an object; to show how to encode data for transmission over the network Management Information Base (MIB) A collection of all the objects that the manager can manage. Each agent has its own MIB.

  27. Objects in MIB System, interface, address, translation Each group has defined variables and/or tables

  28. SNMP Messages

  29. GetRequest – sent from the manager (client) to the agent (server) to retrieve the value of a variable. GetResponse - sent from the agent to the manager in response to GetRequest and GetNextRequest. It contains the value of the variable(s) requested by the manager. SetRequest - sent from the manager to the agent to set (store) a value in a variable. Trap – agent to manager – to report an event Ex. Agent is rebooted; reports the time of rebooting. SNMP Messages

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