Copyright 2003 Objectives: Chapter 6: TCP/IP Transport and Application Layers TCP/IP transport layer * Transport layer protocols * TCP/IP application layer * Application layer protocols

Copyright 2003 The Transport Layer Functions Five basic services: Segmenting upper-layer application data Establishing end-to-end operations Sending segments from one end host to another end host Flow control: Avoids the problem of a host at one side of the connection overflowing the buffers in the host at the other side. Ensuring data reliability Ensure integrity of the data

Copyright 2003 Three-Way Handshake

Copyright 2003 Windowing A method of controlling the amount of information transferred end to end Information can be measured in terms of the number of packets or the number of bytes

Copyright 2003 Window Size Larger window sizes increase communication efficiency.

Copyright 2003 Acknowledgment Positive acknowledgment requires a recipient to communicate with the source, sending back an acknowledgment message when it receives data. Sender keeps a record of each data packet that it sends and expects an acknowledgment.

Copyright 2003 Layer 4 Protocols

Copyright 2003 TCP Connection oriented Reliable Divides outgoing messages into segments Reassembles messages at the destination station Resends anything not received Reassembles messages from incoming segments

Copyright 2003 UDP Connectionless Unreliable Transmits messages (called user datagrams) Provides no software checking for message delivery (unreliable) Does not reassemble incoming messages Uses no acknowledgments Provides no flow control

Copyright 2003 TCP Segment Format

Copyright 2003 UDP Segment Format

Copyright 2003 Port Numbers

Copyright IP and TCP Router Network Data Link Physical A router routes with the network address (such as the IP address) Application 1 Application 2 Application 1 Application 2 IP address is used to route data around the Internet TCP part allows applications to communicate over the network

Copyright 2003 TCP/IP Application Layer

Copyright 2003 TCP/IP Protocol Graph

Copyright 2003 Responsibilities Identifying and establishing the availability of intended communication partners Synchronizing cooperating applications Establishing agreement on procedures for error recovery Controlling data integrity

Copyright 2003 Session Establishment

Copyright 2003 Session Protocols Session layer – establishes, manages, and terminates dialogs of continuity between application layer protocols Dialog Control –Parameter negotiation –Determine half-duplex or full-duplex Examples of session protocols: –Remote Procedure Call (RPC) –Appletalk Session Protocol (ASP) –X Windows System

Copyright 2003 Presentation Protocols Presentation layer – ensures that data sent by one application is readable by another application Responsibilities: –Data Format –Data Encryption –Data Compression

Copyright 2003 Data Format Protocols Text – ASCII, EBCDIC, Unicode Markup Languages – SGML, HTML, DHTML, XML Images – GIF, JPEG, TIFF Audio – WAV, MP3, WMA, MIDI Video – MPEG, Quicktime Data - XML, Morse Code, Huffman encoding

Copyright 2003 Markup Language Formats Standard Generalized Markup Language (SGML) –Old markup language used by printers HyperText Markup Language (HTML) –Subset up SGML used to display web pages Dynamic HyperText Markup Language (DHTML) –Extensions added to HTML to display dynamic elements like pop-up text, layering, updateable data –Cascading Style Sheets (CCS) - data separate from appearance eXtensible Markup Language (XML) –Large subset of SGML but less forgiving in syntax than HTML –Schemas can represent almost any kind of data

Copyright 2003 Application Layer Protocols Domain Name System (DNS) File Transfer Protocol (FTP) Hypertext Transfer Protocol (HTTP) Simple Mail Transport Protocol (SMTP) Simple Network Management Protocol (SNMP) Telnet Several other protocols available

Copyright 2003 Application program makes contact with network application for Application Convert data into a form which can be transmitted Presentation Contact remote system and request a transmission Session Negotiate data transfer and split data into segments Transport Add source and destination addresses Network Data packet converting into a form which can be transmitted over the network Data link The data frame is converted into binary form and transmitted over a physical connection Physical application program Hello. Fred. To: Fred From: Bert Hello. Fred. HELO sys.com FOR Fred To: Fred From: Bert Hello. Fred. Seg 1 Seg 2 Seg 3 Seg 1Addr Seg 2Addr Seg 3Addr Seg 1AddrStartEnd Data encapsulation Seg 2AddrStartEnd Seg 3AddrStartEnd

Copyright 2003 Domain Name System (DNS) The Domain Name System (DNS) is a hierarchical naming system for computers or any resource participating in the Internet. Most importantly, it translates domain names meaningful to humans into the numerical IP addressing of devices world-wide. An often used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses.

Copyright 2003 Domain name server Internet Once WWW browser has the IP address of the destination, it can then access it DNS returns back the IP address of the domain name DNS may interrogate Other DNS’s to Determine IP addresses WWW browser asks The DNS for the IP address of the domain name Domain name server

Copyright 2003 Example Domain Naming Structure sales res www nec sony intel pc01 www sun01 mmse dcs eece hw napier ed org ac co pc01 pc01.eece.napier.ac.uk fr uk de mil gov com edu Primary domain Example DNS mappings Domain nameIP address web.nec.com Example DNS mappings Domain nameIP address web.nec.com

Copyright 2003 File Transfer Protocol (FTP) FTP is a file transfer protocol for exchanging and manipulating files over a TCP computer network. FTP is a reliable, connection-oriented service that uses TCP protocol to transfer files between systems that support FTP. An FTP client may connect to an FTP server to manipulate files on that server.

Copyright 2003 Simple Mail Transport Protocol (SMTP) Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail ( ) transmission across IP networks. servers communicate with each other using the SMTP to send and receive mail messages User-level client mail applications typically only use SMTP for sending messages to a mail server for relaying. For receiving messages, client applications usually use either the Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP) to access their mail box accounts on a mail server.

Copyright 2003 Simple Network Management Protocol (SNMP) SNMP is an application layer protocol that facilitates the exchange of management information between network devices. SNMP is used in network management systems to monitor network devices for administration purposes. An SNMP managed network consists of the following: –Network management system (NMS) –Managed device –Agents

Copyright 2003 Telnet Telnet client software provides the ability to log in to a remote Internet host that is running a Telnet server application and then to execute commands from the command line (Remote Access).

Copyright 2003 Hypertext Transfer Protocol (HTTP) HTTP is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP is a request/response standard between a client, the end-user, and a server, the web site. The client making a HTTP request, using a web browser, the responding server stores or creates resources such as HTML files is called. In between the user agent and origin server may be several intermediaries, such as proxies, gateways, and tunnels. An HTTP client initiates a request. It establishes a TCP connection to a particular port on a host (port 80 by default). An HTTP server listening on that port waits for the client to send a request message. Upon receiving the request, the server sends back the requested resource, an error message, or some other information.

Copyright 2003 HTTP operation HTML/Java WWW server WWW browser HTTP protocol WWW browser HTTP TCP IP HTTP protocol HTML/Java WWW page Presentation Session Transport Network Internet

Copyright 2003 Server Server processes ASP or PHP tags to produce standard HTML Server-side include Client-side include WWW page with ASP or PHP HTML file HTML file sent with Java Script and/or VBScript WWW browser processes Java Script and/or VB Script WWW browser displays HTML Untitled Document Untitled Document Server Client – Server Application

Copyright 2003 HTML Fred Bloggs Fred Bloggs Home Page I'm Fred Bloggs. Below is a table of links. General Research CV Papers Published HTML/Java Tutorials Tutorial 1 Tutorial 2 Tutorial 1 Tutorial 2 Tutorial 3 Fred Bloggs Fred Bloggs Home Page I'm Fred Bloggs. Below is a table of links. General Research CV Papers Published HTML/Java Tutorials Tutorial 1 Tutorial 2 Tutorial 1 Tutorial 2 Tutorial 3

Copyright 2003 Server Side: ASP, PHP and JSP <% String user = (String)session.getAttribute("user"); if ((user == null) || (user.equals(""))){ %> <% String user = (String)session.getAttribute("user"); if ((user == null) || (user.equals(""))){ %> <?php $value=0; //our variable while($value<=10){ print(" $value = ".($value*$value)); print(" \n"); $value=$value+1; } ?> <?php $value=0; //our variable while($value<=10){ print(" $value = ".($value*$value)); print(" \n"); $value=$value+1; } ?> Current time is JSP ASP PHP

Copyright 2003 Client Side: JavaScript, VBScript var dat=new Date(), mon=["Jan","Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; document.write("Month is "); document.write(dat.getMonth()); document.write(" and the name of the month is "); document.write(mon[dat.getMonth()]); var dat=new Date(), mon=["Jan","Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"]; document.write("Month is "); document.write(dat.getMonth()); document.write(" and the name of the month is "); document.write(mon[dat.getMonth()]); sub myheader_onClick myheader.Style.Color = "BLACK" end sub JavaScript VBScript