Download layered

Communication Network
Protocols
Jaya Kalidindi
CSC 8320(fall 2008)
Overview





Network Protocols
OSI Protocol Suite
TCP/IP Protocol Suite
Protocol Examples in Internet Network
References
Network Protocols



Network protocols are sets of standard rules :
To regulate the exchange of messages
For Representing the data,authentication and
error detection.
To provide a reliable communication.
What does a protocol tell us?

Syntax of a message



Semantics of a message



what fields does it contain?
in what format?
what does a message mean?
for example, not-OK message means
receiver got a corrupted file
Actions to take on receipt of a message

for example, on receiving not-OK message,
retransmit the entire file
Protocol layering




A network that provides many services needs many
protocols
Turns out that some services are independent but others
depend on each other
Protocol A may use protocol B as a step in its execution
 for example, packet transfer is one step in the
execution of the example reliable file transfer
protocol
This form of dependency is called layering
 reliable file transfer is layered above packet transfer
protocol
 like a subroutine
OSI Protocal Suite
Physical Layer




First level in Network Layer
Handles all the physical aspects of
communication between two
directly connected physical entities.
Provides the basis for higher level
communication services.
Main functionality is to transmit
bits.
Data Link Layer




This layer accepts the bit streams
provided by the physical layer .
Provides reliability of transfer of
data between two directly
connected entities.
Its functionality includes error
detection control, flow control and
access control.
Divided into two sub-layers:


Medium Access Control
Logical Link Control
MAC sub-layer




Defines means by which physical
means may be accessed.
It co-ordinates to seize a shared
channel by multiple MAC entities.
Provides a limited form of error
control.
Ethernet is an example of a shared
medium with defined MAC sub-layer
functionality.
LLC sub-layer


It is responsible of reliable transfer
of message-link protocol data units
between two directly connected
layer 2 entities.
LLC services can be


Connection oriented: Frames are
individually numbered and
acknowledged by their sequence
number.
Connection-less: Messages are not
acknowledged.
Data link layer
Transport Layer


Concerned with getting level 4
messages form source to
destination in a reliable manner.
Functions are:



Windowing and flow control.
Error detection and recovery.
Multiplexing.
Continued…

Two types of service quality:


Reliable service: makes sure that data
is not lost and provides data error-free
to the user.
Un-reliable service: does not have a
mechanism to show that receiver has
received the data sent.
Network Layer



Used to support data
communication between indirectly
connected entities.
Has the ability to forward messages
from layer 3 entity to another, until
final destination is reached.
Functions are:



Routing
Forwarding packets to final destination
port.
Providing logical addressing.
Session layer



Controls communication or
dialogues between applications on
hosts.
Synchronization is achieved at
coordinated timing .
NFS, NetBios, SQL are some
examples.
Session initiation protocol
Presentation Layer


Performs data transformation or
formatting if required by the end
applications.
Functions are:

Data compression
File formatting
Encryption
•
MPEG, Quicktime are some examples.


Application Layer



Provides services that directly
support an application that runs on
the host.
Most network management
activities are based on services
provided by the layer 7.
FTP, Telnet, SNMP, SMTP are some
examples.
OSI vsTCP/IP
FTP (file transfer control )
Allows users to access
remote file servers, list
remote directories, and
move files to or from
remote hosts.
FTP understands basic
file formats and can
transfer files in ASCII
character or binary
format., FTP provides a
standard
UNIX-like user interface,
regardless of the actual
underlying operating
system.
Telnet
Telnet provides a remote
terminal access protocol
running over Transport
Control Protocol. It allows a
user at one site to establish
a virtual circuit connection
to a remote system
Using Telnet, a user at one
host can login to another
host, appearing like directly
attached.
SNMP

Is an application service that
has evolved with the growth
of TCP/IP. It was derived
from a low-overhead
protocol designed to monitor
Internet routers
UDP

The User Datagram
Protocol (UDP) is a
Transport Layer protocol
in the TCP/IP protocol
suite. UDP provides a
connectionless, best
effort delivery service
UDP.
SMTP
Email is the most widely used application on the Internet (although it
does not account for the highest volume of traffic). The Simple mail
transfer protocol (SMTP) provides a simple, text-oriented protocol to
transfer mail reliably between TCP/IP-based systems
Reference




R. Chow and T. Johnson. Distributed
Operating Systems & Algorithms. 1997
Jim Kurose, Keith Ross, Computer
Networking: A Top Down Approach Featuring
the Internet, 3rd edition. Addison-Wesley,
July 2004.
Cisco Systems, OSI Network Protocols,
October 2006.
Diagrams:www.wikipedia.org,www.
google.com
TCP/IP
THANK YOU