Wireless Communication

1. Protocols and the
TCP/IP Suite
Chapter 4

2. Steps in Communication of two
Computer through a Network
1 The source system must either activate the direct data
communication path or inform the communication network
of the identity of the desired destination system.
2 The source system must ascertain that the destination system
is prepared to receive data.
3 The file transfer application on the source system must
ascertain that the file management program on the
destination system is prepared to accept and store the file for
this particular user.
4 If the file formats used on the two systems are incompatible,
one or the other system must perform a format translation
function

3. Key Features of a Protocol
 Syntax
 Concerns the format of the data blocks
 Semantics
 Includes control information for coordination
and error handling
 Timing
 Includes speed matching and sequencing

4. TCP/IP Layer: Agents Involved
in Communication
 Applications
 Exchange data between computers (e.g., electronic mail)
 Computers
 They are connected to networks & the exchange of data
is through the network & between the computers
 Networks
 Transfers data from one computer to another

5. TCP/IP Layers
 Physical layer
 Network access layer
 Internet layer
 Host-to-host, or transport layer
 Application layer

6. TCP/IP Physical Layer
 Covers the physical interface between a data
transmission device (e.g. workstation or computer)and a
transmission medium or network
 Physical layer specifies:
 Characteristics of the transmission medium
 The nature of the signals
 The data rate
 Other related matters

7. TCP/IP Network Access Layer
 Concerned with the exchange of data between an end
system (server or workstation) and the network to which
it's attached
 The sending computer must provide the address of the
destination computer, so that the network may route that
data to the appropriate destination
 The sending may wish to invoke certain services, such as
priority, that might be provided by the network
 Software used depends on type of network
 Circuit switching
 Packet switching (e.g., X.25)
 LANs (e.g., Ethernet)
 Others

8. TCP/IP Internet Layer
 Uses internet protocol (IP)
 Provides routing functions to allow data to traverse
multiple interconnected networks
 Implemented in end systems but also in routers
 Router: “It is a processor that connect two networks &
whose primary function is to relay data from one network
to the other on its route from the source to the destination
end system”

9. TCP/IP
Host-to-Host, or Transport Layer
 Commonly uses transmission control protocol (TCP)
 The reliability of the data is independent of the nature
of the application
 Provides reliability during data exchange
 Completeness
 Order

10. TCP/IP Application Layer
 It contains the logic needed to supports user
applications
 Uses separate modules that are peculiar (abnormal/
doesn’t match) to each different type of application
 For example each different type of application, such as
File Transfer, a separate module is needed.

11. Operation of TCP and IP

14. Protocol Data Units (PDUs)

16. Common TCP/IP Applications
 Simple mail transfer protocol (SMTP)
 Provides a basic electronic mail facility
 File Transfer Protocol (FTP)
 Allows files to be sent from one system to another
under user command
 Both text and binary files are accommodated, and
the protocol provides features for controlling user
access
 TELNET
 Provides a remote logon capability

17. Layers of the OSI Model
The Open Systems Interconnection (OSI) reference model was
developed by the International Organization for Standardization
(ISO)l as a model for a computer protocol architecture and as a
framework for developing protocol standards. The OSI model
consists of seven layers:
 Application
 Presentation
 Session
 Transport
 Network
 Data link
 Physical

18. OSI Application Layer
 The application layer enables the user, whether
human or software, to access the network.
 It provides user interfaces and support for services
such as electronic mail, remote file access and
transfer, shared database management, and other
types of distributed information services
 Provides access to the OSI environment for users
 Provides distributed information services

19. OSI Presentation Layer
 The presentation layer is concerned with the syntax and
semantics of the information exchanged between two
systems
 Provides independence to the application processes
from differences in data representation (syntax)

20. OSI Session Layer
 The services provided by the first three layers (physical,
data link, and network) are not sufficient for some
processes.
 The session layer is the network dialog controller. It
establishes, maintains, and synchronizes the interaction
among communicating systems.
 Provides the control structure for communication
between applications
 Establishes, manages, and terminates connections
(sessions) between cooperating applications

21. OSI Transport Layer
 The transport layer is responsible for process-to-process
delivery of the entire message. A process is an application
program running on a host. Whereas the network layer
oversees source-to-destination delivery of individual packets,
it does not recognize any relationship between those packets.
It treats each one independently, as though each piece
belonged to a separate message, whether or not it does.
 The transport layer, on the other hand, ensures that the whole
message arrives intact and in order, overseeing both error
control and flow control at the source-to-destination level
 Provides reliable, transparent transfer of data between end
points
 Provides end-to-end error recovery and flow control

22. OSI Network Layer
 The network layer is responsible for the source-to-destination
delivery of a packet, possibly across multiple networks (links).
 Whereas the data link layer oversees the delivery of the packet
between two systems on the same network (links), the network
layer ensures that each packet gets from its point of origin to its
final destination.
 Provides upper layers with independence from the data
transmission and switching technologies used to connect systems
 Responsible for establishing, maintaining, and terminating
connections

23. OSI Data link Layer
 The data link layer transforms the physical layer, a raw
transmission facility, to a reliable link.
 It makes the physical layer appear error-free to the
upper layer (network layer).
 Provides for the reliable transfer of information across
the physical link
 Sends blocks (frames) with the necessary
synchronization, error control, and flow control

24. OSI Physical Layer
 The physical layer coordinates the functions required to
carry a bit stream over a physical medium.
 It deals with the mechanical and electrical
specifications of the interface and transmission medium
 Concerned with transmission of unstructured bit stream
over physical medium
 Deals with accessing the physical medium
 Mechanical characteristics
 Electrical characteristics
 Functional characteristics
 Procedural characteristics

25. Comparison of OSI and TCP/IP

26. TCP/IP Architecture Dominance
 TCP/IP protocols matured quicker than similar OSI
protocols
 When the need for interoperability across networks
was recognized, only TCP/IP was available and ready
to go
 OSI model is unnecessarily complex
 Accomplishes in seven layers what TCP/IP does with fewer
layers

27. Internetworking Terms
 Communication network – facility that
provides a data transfer service among
devices attached to the network
 Internet – collection of communication
networks, interconnected by bridges/routers
 Intranet – internet used by an organization
for internal purposes
 Provides key Internet applications
 Can exist as an isolated, self-contained internet

28. Internetworking Terms
 End System (ES) – device used to support end-user
applications or services
 Intermediate System (IS) – device used to connect
two networks
 Bridge – an IS used to connect two LANs that use
similar LAN protocols
 Router - an IS used to connect two networks that may
or may not be similar

29. Functions of a Router
 Provide a link between networks
 Provide for the routing and delivery of data between
processes on end systems attached to different networks
 Provide these functions in such a way as not to require
modifications of the networking architecture of any of
the attached sub networks