McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 TCP/IP Application Layer

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Comparison between OSI and TCP/IP

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Client-Server Model (many-to-one) Client requests a service from a server Local machineRemote machine Client program runs when it is needed Server program runs infinitely

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Bootstrap Protocol (BOOTP) Dynamic Host Configuration Protocol (DHCP 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 DNS in the Internet DNS –Domain Name System Domain name – name used instead of address 3 sections of domain name space (tree)

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Generic Domains Define registered hosts according to their generic behavior 1 st level label (3 character)  Organization types

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Country Domains De Anza College in Cupertino in California in the United States

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Inverse Domain Map an address to a name Server list an IP address of authorized clients. Client sends a query to DNS Server

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 TERminal Network (TELNET) 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Remote Login OS does not interpret the characters 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Client TELNET translates characters to NVT form Server TELNET translates NVT form into characters acceptable by the remote computer.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Trivial File Transfer Protocol (TFTP) -less funtionalities than FTP ex. Diskless workstation or a router is booted, we need to download the bootstrap and configuration file

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 SMTP Concept Simple Mail Transfer Protocol -supports -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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 UAs and MTs User Agent & Mail Transfer Agent

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Relay MTAs

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Mail Gateways Does not use TCP/IP

McGraw-Hill©The McGraw-Hill Companies, Inc., Address

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 MIME

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 POP3 and SMTP

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Internet Management Components Management Information Base (MIB) 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 A collection of all the objects that the manager can manage. Each agent has its own MIB.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Objects in MIB System, interface, address, translation Each group has defined variables and/or tables

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 SNMP Messages

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 SNMP Messages 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.