TFTP, SMTP, POP, URL - papersocean

Computer Networks:

Physical Layers

Data link Layer(DLL)

Network Layer

Transport Layer:

Session and Presentation Layer:

Application Layer:

TFTP | SMTP | POP | URL

Trivial file transfer for protocol (TFTP):

There are events when we want to duplicate a record without the requirement for each of the highlights of the FTP protocol.

For example when a diskless workstation or a remote PC is boot we need to download the bootstrap and configure files. here we do not need all of the sophistication provided in FTP we just need protocol that quickly copies the file.

TFTP design for this type of file transfer. It is so simple packet can fit into the rate only memory of a diskless workstation. It can be used at bootstrap time. The reason that it fit on ROM is that it required only base IP and UDP. However there is no security TFTP. TFTP Can read or write a file to client. Reading means coping a file from the server site to the client site writing TFTP use the services of UDP on the well known port 69.

Simple mail transfer protocol SMTP:

One of the popular network services is electronic mail (e-mail), that TCP/IP supports email on the internet is known as simple mail transfer protocol SMTP. it is a system for sending message to other computer using based on email address. SMTP provides for male exchange between users on the same or different computer and supports:
Sending us single message to one or more recipients.
Sending messages that include text voice video or graphics.
Sending message to users on network outside the internet.

Two components of SMTP systems are:

User agent (UA)
Mail transfer agent (MTA)

User agent (UA) prepare create and put the message in the envelope. The UA is normally program used to send and receive mail. Popular user agent programs are MH. Barkeley mail, gmail.

Mail transfer agent (MTA) transfer the mail across the internet.

Post office protocol (POP):

SMTP expect the destination host the mail server receives the email, to be online all the time; otherwise a TCP connection cannot be established. For this reason it is not practical to established and SMTP session with desktop computer because desktop computers are usually power down at the end of the day.

In many organization mail is received by a SMTP server, that is always online. this SMTP server gives a mail drop service. this service receives the email on behalf of every host in the organization. Workstation interact with the SMTP house to retrieve message by using a client server protocol stack as office protocol POP.

Uniform resource locator (URL):

URL identifies a particular internet resources; for example a web page a GOPHER server, a library catalog, and image or a text file. URL represent a standardized addressing scheme for internet resources and help the user to locate this resources by entity exactly where they are. Every resource available where the world wide web has a unique URL.

URL consist of later number and punctuation. The basic structure of URL is hierarchical and Hierarchy move from left to right.