what is protocol

2. What is a Protocols???
• Protocols define how messages are sent and
received.
• A set of rules that defines how data is
formatted and processed on a network.

3. Types of Protocols
• TCP/IP
• HTTP
• FTP
• SMTP

4. Internet Protocol
• Internet Protocol (IP) is the principal
communications protocol in the Internet Protocol
Suite for relaying datagram across network
boundaries.
• In other words, it is a set of rules used to send and
receive messages at the Internet address level.
• IP provides the method of distributing data in
packets, can distribute packets to a destination via
different routes, and can handle congestion in this
manner.

5. Transmission Control Protocol
• The Transmission Control Protocol (TCP) is one of the
core protocols of the Internet protocols suite (IP), and is
so common that the entire suite is often called TCP/IP.
• TCP provides for virtual circuits, error detection and
correction, automatic repeat requests, and other reliable
end-to-end communications, using the IP protocol for
transmission
• TCP handles reassembling packets at the destination, as
they can arrive out of order due to the IP routing scheme
to avoid congestion.
• TCP/IP together provide for the most commonly used
functions on the internet, namely e-mail, file transfer, and
the basis of the HTTP protocol for web page documents.

6. TCP Ports:

8. Hypertext Transfer Protocol
• The Hypertext Transfer Protocol (HTTP) is an
application protocol for distributed, collaborative,
hypermedia information systems. HTTP is the
foundation of data communication for the World
Wide Web.
• Hypertext is structured text that uses logical links
(hyperlinks) between nodes containing text. HTTP is
the protocol to exchange or transfer hypertext.

9. Working of HTTP

10. File Transfer Protocol
• File Transfer Protocol (FTP) is a standard
network protocol used to transfer files from one
host to another host over a TCP-based network,
such as the Internet.
• A typical FTP session operates using two
channels: a command (or control) channel and a
data channel.
• Command channel --transmitting commands and
replies to those commands (Port 21)
• Data channel --transferring data. (Port 20)

11. FTP Modes
• Two modes that FTP can run in:
– Active FTP
– Passive FTP

12. Active FTP
• A user connects from a random port on a file transfer client to
port 21 on the server. It sends the PORT command, specifying
what client-side port the server should connect to. This port
will be used later on for the data channel and is different from
the port used in this step for the command channel.
• The server connects from port 20 to the client port designated
for the data channel. Once connection is established, file
transfers are then made through these client and server ports.

13. Passive FTP
• The client connects from a random port to port 21 on the
server and issues the PASV command. The server replies,
indicating which (random) port it has opened for data transfer.
• The client connects from another random port to the random
port specified in the server's response. Once connection is
established, data transfers are made through these client and
server ports.

14. Active Vs. Passive
FTP

16. Simple Mail Transfer Protocol
• Simple Mail Transfer Protocol (SMTP) is an
Internet standard for electronic mail (e-mail)
transmission across Internet Protocol (IP)
networks.
• SMTP uses TCP port 25.

19. • Aweb portal is most often one specially-designed
Web page at a website which brings information
together from diverse sources in a uniform way.
• In other words, a website or service that offers a
broad array of resources and services, such as e-mail,
forums, search engines, and online-shopping malls.
• Usually, each information source gets its dedicated
area on the page for displaying information; often, the
user can configure which ones to display.

20. Types of Web Portals

22. • The Domain Name System (DNS) is an
hierarchical distributed naming system for
computers, services, or any resource connected
to the Internet or a private network.
• It associates various information with domain
names assigned to each of the participating
entities.
• rarely do applications deal directly with IP
addresses
• top level domains: edu, com, gov, org, net, …
• hostname.domain_name.top_level _domain
e.g., csc.liv.ac.uk

23. DNS (Continue…)
Host number
The part of the IP address that specifies a particular
host (machine) on the network.
Domain name
The specifies a specific organization or group.
Top-level domain (TLD)
The last section of a domain name that specifies the
type of organization or its country of origin.

27. • Search Engines are basically a type of program
that uses keywords to search for documents
that relate to these keywords and then puts the
results found in the order of relevance to the
topic that was searched for.
• Examples:
– Google
– Alta Vista

28. Importance
• Search engines are important because with over 8
billion web pages available, it would be impossible to
search for the information that is specifically needed.
• That is why search engines are used to filter the
information that is on the internet and transform it
into results that each individual can easily access and
use within the matter of seconds.

29. Types of Search Engines
• Crawler based search engines (e.g.: Google, Y
ahoo,
Ask.com)
• Directories (e.g.: dmoz.org, Yahoo.com)
• Specialty search engines (e.g.:Askjeeves)
• Hybrid search engines (e.g.: Yahoo.com)
• Meta search engine (e.g.: Metacrawler)

31. • A web browser is a software application for
retrieving, presenting, and passing over
information resources on the World Wide Web.
• In other words, it is an software application to
access information provided by web browsers.
• It brings information resources to the user.
• Retrieve, present, and traverse information
resources on the WWW.

32. Famous Web Browsers
• Internet Explorer
• Mozilla Firefox
• Safari
• Opera
• Google Chrome