This document provides an overview of computer networks and networking concepts. It discusses the OSI model and its seven layers, including the responsibilities of each layer. It also describes the TCP/IP protocol suite and how it maps to the OSI model. Physical network topologies like star, bus, ring and mesh are defined. The document examines addressing in TCP/IP networks, including physical, logical, and port addresses. Network devices, protocols, and the exchange of data across the OSI model layers are summarized as well.

1. EC2352- COMPUTER
NETWORKS

2. UNIT I PHYSICAL LAYER
Data Communications – Networks - Networks
models – OSI model – Layers in OSI model – TCP /
IP protocol suite – Addressing – Guided and
Unguided Transmission media
Switching: Circuit switched networks – Data gram
Networks – Virtual circuit networks. Cable networks
for Data transmission: Dialup modems – DSL –
Cable TV – Cable TV for Data transfer.

3. TEXT BOOKS:
 1. Behrouz A. Foruzan, “Data communication and
Networking”, Tata McGraw-Hill, 2006: Unit I-IV
 2. Andrew S. Tannenbaum, “Computer Networks”,
Pearson Education, Fourth Edition, 2003: Unit V

4. CHAPTER 1
 Data Communications
 Components
 Data Representation
 Data Flow
 Networks
 Network criteria
 Physical topology
 Categories of Networks
 Protocols
 Syntax
 Semantics
 Timing

5. DATA COMMUNICATIONS
 Purpose of communication- to share information
 Sharing Information can be local or remote.
 The term telecommunication means communication
at a distance.
 The word data refers to information presented in a
form agreed by the parties creating and using the
data
 Data communications are the exchange of data
between two devices via some form of transmission
medium such as a wire cable.

6. COMPONENTS

7. DATA REPRESENTATION
 Text - bit pattern (a sequence of 0’s and 1’s)
 Numbers – bit pattern (number converted to binary)
 Images – bit pattern
 Audio – sound or music
 Video – picture or movie

8. DATA FLOW

9. NETWORKS
 A network is a set of devices (often referred to as
nodes) connected by communication links.
 A node can be a computer, printer, or any other
device capable of sending and/or receiving data
generated by other nodes on the network.
 A link can be a cable, air, optical fiber, or any
medium which can transport a signal carrying
information.

10. NETWORK CRITERIA
 Performance
 Depends on Network Elements
 Reliability
 Failure rate of network components
 Security
 Data protection against corruption/loss of data due to:
 Errors
 Malicious users

11. PHYSICAL STRUCTURES
 Type of Connection
 Point to Point - single transmitter and receiver
 Multipoint - multiple recipients of single transmission

12. PHYSICAL STRUCTURES
How devices
are connected
to make a n/w.

13. MESH TOPOLOGY:
 A physical topology in which every device has a
dedicated point to point link to every other device.
 In mesh topology we need n(n-1)/2 links.
Advantages:
 It eliminating traffic problems.
 Fault identification is easy.
 Mesh topology is robust.
Disadvantages:
 It is expensive and difficult to install a mesh n/w.
Example:
Connection of telephone regional offices to every
other regional offices.

14. STAR TOPOLOGY:
 Each device has a dedicated point to point link
only to central controller usually called a hub.
Advantages:
 Hub provides Fault identification is easy.
 Less expensive than mesh.
 It include robustness.
Disadvantages:
 The failure of the central hub can bring down the
entire n/w.
Example:
 Used in LANs

15. BUS TOPOLOGY:
 Bus topology is multipoint.
 One long cable acts as a backbone to link all the
devices in a n/w.
Advantages:
 Easy to add more workstations.
 Inexpensive to install.
 Bus topology works well for small n/ws
(2-10 devices)
Disadvantages:-
 If the backbone breaks, the n/w goes down.
 It is difficult to isolate where a problem may be.
 Adding new devices may require modification or
replacement of the backbone.
Example:
 Used in Ethernet LANs.

16. RING TOPOLOGY:
 Each device has a dedicated point to point link
with only the two devices on either side of it.
Advantages:
 Easy to install and reconfigure.
 No collisions.
Disadvantages:
 A break in the ring can disable the entire n/w.

17. CATEGORIES OF NETWORKS
 Local Area Networks (LANs)
 Limited to a few kilometers
 Ex: single office, building or campus
 Wide Area Networks (WANs)
 Long distances
 Provide connectivity over large areas ie,
country, continent
 Metropolitan Area Networks (MANs)
 Size b/w LAN and WAN
 Inside city ie, cable tv n/w, telephone n/w

18. PROTOCOLS
 A protocol is synonymous with rule. It consists of a set of
rules that govern data communications.
 It determines what is communicated, how it is
communicated and when it is communicated.
 Elements of protocol:
 Syntax
 Structure or format of the data
 Indicates how to read the bits - field
 Semantics
 Interprets the meaning of the bits
 Knows which fields define what action
 Timing
 When data should be sent and what
 Speed at which data should be sent or speed at which
it is being received.

19. THE OSI MODEL
 An ISO standard that covers all aspects of network
communications is the Open Systems
Interconnection (OSI) model.
 An Open System is a set of protocols that allows
any two different systems to communicate
regardless of their underlying architecture.

20. SEVEN LAYERS OF THE OSI MODEL

21. A mnemonic for remembering the layers of the OSI
model is
“Please Do Not Touch Steve’s Pet
Alligator”
Please - Physical Layer
Do - Data Link Layer
Not – Network Layer
Touch – Transport Layer
Steve’s – Session Layer
Pet – Presentation Layer
Alligator – Application Layer

22. AN EXCHANGE USING THE OSI MODEL

23. PHYSICAL LAYER:
 The physical layer is responsible for movements of individual bits from
one hop to the next.
Responsibilities:
 Data rate : The number of bits sent each second.
 Synchronization of bits : The sender and receiver clocks must
be synchronized.
 Line configuration : Connection of device to the media.
 Physical topology : How devices are connected to make a n/w.
 Transmission mode : Direction of transmission b/w two
devices.

24. PHYSICAL LAYER

25. DATA LINK LAYER:
 The Data link layer is responsible for moving frames from one hop to
the next.
Responsibilities:
 Framing : Divides the stream of bits into manageable units
called frames.
 Flow control : A technique to control the rate of flow of frames.
 Error control : To handling errors in data transmission and to
detect and retransmit lost or damaged frames.
 Access control : To determine which device has control over
the link at any given time.
 Physical addressing : To handle the addressing problem
locally.

26. DATA LINK LAYER

27. HOP-TO-HOP DELIVERY

28. NETWORK LAYER:
 The Network layer is responsible for the delivery of individual
packets from the source host to the destination host.
Responsibilities:
 Logical addressing : The n/w layer adds a header to the
packet coming from upper layer that includes the logical
addresses of the sender and receiver.
 Routing : When n/w are connected to create a large n/w, the
connecting devices route the packets to their final destination.

29. NETWORK LAYER

30. SOURCE-TO-DESTINATION DELIVERY

31. TRANSPORT LAYER:
 The Transport layer is responsible for the delivery of a message from
one process to another.
Responsibilities:
 Segmentation and reassembly : A message is divided into
transmittable segments and to reassemble the message
correctly upon arriving at the destination.
 Connection control : It can be either connectionless or
connection oriented
 Flow control : A technique to control the rate of flow of frames.
 Error control : To handling errors in data transmission and to
detect and retransmit lost or damaged frames.

32. TRANSPORT LAYER

33. SESSION LAYER
Responsibilities:
 Dialog Control :
It allows communication b/w
two processes to take place
in either half or full duplex
mode.
 Synchronization :
It allows a process to add
checkpoints to a stream of
data.

34. PRESENTATION LAYER
Responsibilities:
 Translation : The
processes in two systems
are usually exchanging
information in the form of
character strings, numbers
and so on.
 Encryption : Original
information to another form
 Compression : Reduces
the number of bits
contained in the information.

35. APPLICATION LAYER
Services:
 File Transfer, access and
management
 Mail Services

36. SUMMARY OF LAYERS

37. TCP/IP AND OSI MODEL

38. TCP/IP AND OSI MODEL

39. PHYSICAL & DATA LINK LAYERS:
 TCP/IP does not define any specific protocol.
 It support all the standard protocols.
NETWORK LAYER:
 TCP/IP supports the Internetworking Protocol.
 IP uses four supporting protocols
 ARP, RARP, ICMP IGMP.
TRANSPORT LAYER:
 It supports three protocols.
 UDP, TCP ,SCTP.
APPLICATION LAYER:
 Many protocols are defined at this layer.
 SMTP, FTP, HTTP, DNS, SNMP, TELNET

40. ADDRESSES IN TCP/IP

41. RELATIONSHIP OF LAYERS AND ADDRESSES
IN TCP/IP

42. PHYSICAL ADDRESSES:
 The physical address also known as the link address, is the
address of a node as defined by its LAN or WAN.

43. LOGICAL ADDRESSES:
 Logical Addresses are necessary for universal communications.
 A Universal addressing system is needed in which each host can
be identified uniquely.
 A logical address in the internet is currently a 32-bit address.
 The physical addresses will change from hop to hop, but the
logical addresses usually remain the same.
PORT ADDRESSES :
 In TCP/IP architecture, the label assigned to a process is called
a port address.
 A port address in TCP/IP is 16 bits in length.
SPECIFIC ADDRESSES:
 User friendly addresses that are designed for that specific
address.
 www.gmail.com