The document summarizes several key application layer protocols: Telnet allows remote access to servers by emulating a terminal. FTP is used to transfer files between machines. TFTP is a simplified version of FTP with no security. NFS enables accessing files over a network like local storage. SMTP is the standard for email services. LPD/LPR is for remote printing. X Window provides GUI functionality over networks. SNMP allows monitoring of network devices. DNS translates human-readable names to IP addresses. DHCP automatically assigns IP addresses to devices on a network.

1. Tahmina Akter
L Lecturer, Department at CSE
Por port city international university

2. APPLICATION LAYER

6. Application layer

7. Application layer protocols:
The protocols of application layer are following :
1. Telnet
2. FTP
3. TFTP
4. NFS
5. SMTP
6. LPD
7. X Window
8. SNMP
9. DNS
10. DHCP/BootP

8. Telnet:
• Telnet is the chameleon of protocols.
• Its specialty is terminal emulation.
• It allows a user on a remote client machine , called the
Telnet client, to access the resources of another machine ,
the telnet server.
• Telnet achieves this by pulling a fast one on the Telnet
server and making the client machine appears as though it
were a terminal directly attached to the local network.

9. o This projection is actually a software image – a virtual terminal that can
interact with the chosen remote host.
o Telnet client uses the ephemeral port number while the server uses
port number 23 on TCP

10. File Transfer Protocol:
 File Transfer Protocol is the protocol that actually lets us transfer files
and it can accomplish this between any two machines using it.
 But FTP isnot a protocol, its also a program.
 Operating as a protocol, FTP also allows for access to both directories
and files and can accomplish certain types of directory operation such
as relocating into different ones
 FTP is a client-server protocol where a client will ask for a file, and a
local or remote server will provide it.

11.  The end-users machine is typically called the local host machine, which
is connected via the internet to the remote host—which is the second
machine running the FTP software.
 Although a lot of file transfer is now handled using HTTP, FTP is still
commonly used to transfer files "behind the scenes" for other
applications -- e.g., hidden behind the user interfaces of banking, a
service that helps build a website, such as Wix or SquareSpace, or
other services. It is also used, via Web browsers, to download new
applications.

13.  Trivial File Transfer Protocol (TFTP) is a simple protocol used for
transferring files. TFTP uses the User Datagram Protocol (UDP) to
transport data from one end to another. TFTP is mostly used to read
and write files/mail to or from a remote server.

 TFTP is the stripped- down, stock version of FTP, but it’s the protocol of
choice if you know the exactly what you want and where to find it, plus
its so easy to use and its fast too.
Trivial File Transfer Protocol (TFTP)

14.  Trivial File Transfer Protocol is very simple in design and has limited
features as compared to File Transfer Protocol (FTP).
 TFTP provides no authentication and security while transferring files. As
a result, it is usually used for transferring boot files or configuration files
between machines in a local setup.
 Because of its simple design, it is rarely used interactively by users in a
computer network. Its lack of security also makes it dangerous for use
over the Internet.

16. Network File System:
• Network File System (NFS) is a distributed file system protocol
originally developed by Sun Microsystems (Sun) in 1984
• allowing a user on a client computer to access files over
a computer network much like local storage is accessed.
• A network file system (NFS) is a type of file system mechanism
that enables the storage and retrieval of data from multiple disks
and directories across a shared network.
• A network file system enables local users to access remote data
and files in the same way they are accessed locally.

18. Simple Mail Transfer Protocol (SMTP)
 Simple Mail Transfer Protocol (SMTP) is the standard protocol for
email services on a TCP/IP network. SMTP provides the ability to
send and receive email messages.
 SMTP is an application-layer protocol that enables the transmission
and delivery of email over the Internet. SMTP is created and
maintained by the Internet Engineering Task Force (IETF).
 Simple Mail Transfer Protocol is also known as RFC 821 and RFC
2821.

20. Line Printer Daemon:
• The Line Printer Daemon protocol/Line Printer Remote
protocol (or LPD, LPR) is a network printing protocol for
submitting print jobs to a remote printer. The original
implementation of LPD was in the Berkeley printing system in
the BSD UNIX operating system; the LPRng project also
supports that protocol.
• The line printer Daemon protocol is designed for printer
sharing.

21.  The LPD, along with the line printer (LPR) program, allows
print jobs to be spooled and sent to the networks printers
using TCP/IP

22. X Window:
• The X Window System (X11) is an open source, cross platform,
client-server computer software system that provides a GUI in a
distributed network environment.
• Used primarily on Unix variants, X versions are also available for
other operating systems. Features of the X window system include
network transparency, the ability to link to different networks, and
customizable graphical capabilities.
• The X window system was first developed in 1984, as part of
project Athena, a collaboration between Stanford University and
MIT. X.Org Foundation, an open group, manages the development
and standardization of the X window system.
• The X Window System is also known simply as X, X11 or X
Windows.

23. Simple Network Management Protocol (SNMP)
 Simple Network Management Protocol (SNMP) is a set of
protocols for network management and monitoring.
 These protocols are supported by many typical network
devices such as routers, hubs, bridges, switches, servers,
workstations, printers, modem racks and other network
components and devices.
 Supported devices are all network-attached items that
must be monitored to detect conditions.

24.  These conditions must be addressed for proper, appropriate
and ongoing network administration.
 SNMP standards include an application layer protocol, a set of
data objects and a methodology for storing, manipulating and
using data objects in a database schema.

25. Domain Name Service(DNS):
The Domain Network System (DNS) protocol helps
Internet users and network devices discover
websites using human-readable hostnames, instead
of numeric IP addresses.

26. DHCP:
 DHCP (Dynamic Host Configuration Protocol) is a network
management protocol used to dynamically assign an Internet
Protocol (IP) address to any device, or node, on a network so they
can communicate using IP.
 DHCP automates and centrally manages these configurations rather
than requiring network administrators to manually assign IP
addresses to all network devices. DHCP can be implemented on
small local networks as well as large enterprise networks.

27. THANK YOU