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TCP/IP

Application Layer

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Comparison between OSI and TCP/IP

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Client-Server Model(many-to-one)

Client requests a service from a server

Local machine Remote machine

Client program runs when it is neededServer program runs infinitely

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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

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DNS in the Internet DNS –Domain Name System

Domain name – name used instead of address

3 sections of domain name space (tree)

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Generic Domains

Define registered hostsaccording to their generic behavior

1st level label (3 character)Organization types

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Country Domains

De Anza College in Cupertino in California in the United States

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Inverse Domain

Map an address to a name

Server list an IP address of authorized clients.

Client sends a query to DNS Server

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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.

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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

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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

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Concept of NVT

Network Virtual Terminal (NVT) - universal interface

UNIXCtrl+z – suspendCtrl+c – abortCtrl+d – end-of-file

DOSCtrl+z – end-of-file

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• Client TELNET translates characters to NVT form

• Server TELNET translates NVT form into characters acceptable by the remote computer.

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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

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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

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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

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UAs and MTsUser Agent & Mail Transfer Agent

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Relay MTAs

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Mail Gateways

Does not use TCP/IP

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E-mail Address

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MIME

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POP3 and SMTP

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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

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• 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.

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• 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.

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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.

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Objects in MIB

System, interface, address, translation

Each group has defined variables and/or tables

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SNMP Messages

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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.