Now let's talk about the application protocols. The protocols that work in the
session presentation and application layers off the eyes OS I model and in the application layer off the TCP I p Protocol.
These protocols are such as the http or http s that offers the Web service is
the https is the secure version off Http this US is for security
or like the file sharing service is FTP or T ftp file transfer protocol or trivial file transfer protocol or the mail service is seem pale Male transfer protocol smtp
pop three or I met Post office protocol version three or Internet message access protocol or the D. N s service is the domain name system. Service is these are the protocols or example protocols that work in the application layer off the TCP I p each of them.
It has a dedicated port number. Each of them offers a certain service
between the source and the destination between the client and the server over the Internet toe. Offer a certain service to the user off such protocols.
Let's start by the http http stands for hypertext transfer protocol. It supports the Web service. Is it supports the transmission off
images, texts and hyper lings between the Web server and the weapon through the Web browser. It supports the
older www patriots that can be transferred between the server and the client. It uses sport number 80. The secure version off http is actually TP as us here is for security and Https uses the port number for four
Actually, T p is one off the application layer protocols in T c, p, I, p
FTP or the file transfer protocol. Use a sport number 21.
It has a built in application in the M S Windows operating systems. Microsoft Windows Operating systems. Many third party programs can act as FTP server and client as well to transfer files between the FTP server. Tow the FTP client.
The Web browser animal browser can work as an FTP Klein. If you replace the http saw fix at the start off the U. R. L with the word FTP, then it will work as FTP client and can be able to transfer files
The email protocols we can see in the diagram that the email client is contacting the email server
through two protocols. One of them is for sending, which is the SMTP, and the other is for receiving e mails or downloading email messages from the email server to the email plant, which is the top three.
The communication between mail server X and mail server. Why is done via C. The SMTP Protocol Simple male transfer protocol. The SMTP is the common language between the majority of the mail servers around the Internet. Once more at the client. Why
the SMTP is used for sending e mails from the climb Tow the server plant y two server Why
and the pop three is used to download messages off client Why from the server Why the pop free or the I met? It depends whether you want to download the message through pop free or toe just excess. The message through the I met
the SMTP is the common language used by the majority off the main servers. As we have said, it sends messages
back and forth to other mail servers and it is used to sending
message between the male client and to the mail server.
The Post Office protocol is for receiving and collecting email messages from the mail server to the client. It downloads the messages on the machine so the user can work off line can now load the message at the beginning of the session and then if the Internet cuts, it can work off line.
This saves quota on the server, since the messages are downloaded from the server to the client, so the coat off the user can be emptied for other messages to arrive.
Internet. No such excess protocol is another message toe
access the messages by the client on the server. It is just for accessing. The message is reading them. It does not download the message. It does not save the court. Eight. Retrieves only the message header allows the user to read the message about the body of the message. The message itself. It's at the server side. So this is more
commonly used if you are accessing your email from a machine that is not yours from a machine, that you do not want to download your messages on
the D. N s Protocol one off the application protocols working in the TCP i. P. The understands for domain name system or domain name servers in some
written texts, the Deanna's resolves the domain name in tow i P address. For example, www dot cisco dot com is a domain name.
a name that can be understood by the human, but the machine needs numbers, needs addresses to work with. So this resolution between names that are understood by human into address is that understood by machines is done via the D. N s, the domain name system.
The D. N. A server here matches the human address with the numeric address.
The device used numbers understands only ones and zeroes and numbers. So www dot cisco dot com is mapped into the address 1 98.1 33.219 dot 215
Humans can easily understand names. Machines can easily understand addresses and the N s acts as the resolution machine for
resolving names in tow addresses.
This is the D. N s tree around the world. We can see that we have
websites or domain names ending in dot or dot com dot d that I s that UK and dot
we have each country in the world have two letters suffix like that UK United Kingdom bodies for Germany.
we have dot org's for organizations come commercial video for educational mill for military and not for networking organizations. And we also we have some organization names that are governing the Internet, like the I E T F Internet Injurying Task Force
other organizations that can
work and manage the Internet as examples off them domain names that can exist over the Internet we have here the www estimate she named that can be connected toe i e t f as that
parent domain name, then not order. This forms there
fully qualified domain name off www dot i e t f dot org's as a website.
If we can see the on us in action here we have a the N s climbed that contacts. It's local d n A server
asking for what is the i p off cisco dot com. This local Deanna server does not have the answers but can ask, apparently in us about things that
What is the i p off cisco dot com and the parent can
answer it with the I P address off. Sisko will come then the answer is transferred so the D. N s climb.
Sometimes this local Deanna server cashes the the answer
for the sake of not asking once more for that
previously Oscar domain names and can answer about www dot cisco that come from it's cash
in the second time it is asking about from any other client than the first line.
We have also a very well known and famous protocol working in the application layer that is called the the Recipe Dynamic Host Configuration Protocol. It's an important protocol in the configuration of the P C P I. P parameters Inside any machine. If a client on a certain network
moves to be up on the network, it sounds a d S c p clan broad cost Discover message that is read by several servers over the network that he is connected toe several D F. C P servers one off the server sends the DFC
server broadcast off her message,
which means that he offers the client some off the TCP I p parameters that he can take toe start and work over the Internet. What are these parameters? These parameters are the I P address, the subject mosque that if we'll get way and the N s mainly the una server that he can contact oh,
communicate over the Internet,
Then the client responds with the request message
leasing and asking for these parameters.
The offer message says that I'm server a media recipe server. I can offer you these parameters. Then the D. A s a P server finalizes the exchange with acknowledgement. Message
finalizes that this client has reserved this i p address this
sub net mosque this default gateway in this Deanna so that he cannot repeat leasing the same i p address to other machines. Otherwise, there will be a conflict of I P addresses between two machines and this is forbidden.
No two machines can have the same i p address over the same network. So what is the main benefit off this? The Hosp? It saves the offers. The efforts off the network administrator
that is used in configuring several machines with I p addresses Sub net mosque, the fold. Get way. Deanna servers. It saves this effort and makes a machine. Does this task off course? The machine does not make the mistake off the I P conflict does not make the mistake off
assigning the same i p address to two machines.
as a protocol is very commonly Weide widely used over the networks
lease I P address to distribute I P addresses over
several machines on the same network and to save the effort and received the mistakes that humans can do by conflicting i p addresses by this we have
suit should some off the
application protocols working on the application layer off the TCP I p protocol suit. Thank you.