1. Communication between computers uses transmission of digital data over a network medium using defined protocols. 2. Network interface cards connect devices to networks and operate at the data link layer, using hardware addresses and frame structures to transfer data. 3. Tools like volt-ohm meters, tone generators, and optical testers can be used to diagnose and repair physical cabling issues on a network.

1. Communication Using a Network

2. Data Communication
• Transmission of information between two computers
or nodes
Basic
Components
Sender Receiver Medium Message Protocol

3. Signaling Techniques – I
• Two types of Signaling techniques:
– Baseband
– Broadband
• Baseband Signals:
– Uses single frequency to transmit data
– Transmit information in digital form

4. Signaling Techniques – II
• Broadband Signals:
– Data is transmitted using more than one frequency
– Uses analog signals
– Adds additional information to carrier signals by process
of modulation

5. Network Interface Card (NIC) - I
• Hardware device used to connect different computers
on Network
• Serves as a link for sending and receiving data on a
network
• MAC address is address assigned by IEEE to identify
network card
NIC Types
Ethernet Card Token Ring Card

6. Network Interface Card (NIC) - II
• Operates at layer 2 of the OSI model
• Supports data transfer rate of 10, 100 or 1000
Mbps
• User can select an NIC depending on the type
of network, protocol and media used
• MAC address is stored on the PROM of the
NIC

7. Ethernet Card
• Used in devices which are connected using Ethernet
technology
• Two types of Ethernet network card – Wired and
wireless
• A wireless Ethernet card can not communicate with a
wired Ethernet card and vice-versa
• Different types of Ethernet cards can be used depending
on the type of network and corresponding connector
that is required

8. Types of Ethernet Card - I
• 10Base-5 (Thicknet) NIC
• 10Base-2

9. Types of Ethernet card - II
• 10BaseT
• Fiber –optic

10. Token Ring Card
• Used to connect to a token ring network
• Assigned a MAC address by IEEE
• Maximum of two token ring
cards can be installed at any
node
• Consists of 9 pin DIN
type connector which connects
card to network cable

11. Physical Connections
• Physical Connections
– NIC either connected on a PCI or PCI-X slot
– NIC cards can be connected to an USB port or can have a
PC card connection
• Depends on one of the cable connectors:
– BNC connector
– ST-fiber optic connector
– RJ-45 connector

12. Lights on NIC and hub
• Different LEDs on NIC:
– Link LED
– ACT LED
– Speed LED
– Collision LED
• LEDs on Hub:
– Power LED
– Port LED

13. Different LEDs on a NIC
• Link LED – Used to indicate whether any
network connection is present or not
• Act LED – If this LED flashes it indicates that
some activity is taking place on the network
• Speed LED – ON state indicates that it
operates at 100 Mbps and off for 10 Mbps
• Collision LED – Glows when a collision takes
place and present on some old NICs

14. MAC Address
• Also known as hardware or physical address
• Used to identify nodes at lower levels of the OSI model
• MAC address assigned by IEEE
• Is a 12 digit hexadecimal number (48 bit address)

15. Frame Structure
• A MAC frame is divided into 4 parts
• A maximum of 1500 bytes of data can be sent
in a frame
• CRC is only 4 bytes long

16. MAC vs IP address
MAC address IP address
Functions at data link Functions at network layer
layer
It is a physical address It is a logical address
It is fixed It changes with the
relocation of device from
one network to another
It is a 48 bit address It is a 32 bit address

17. Installing the NIC
• Different factors while choosing NIC:
– Bus type (Expansion slot)
– Speed
– Connection type (cabling)
• Hardware Requirements:
– Pentium I/233MHz
– 32 MB RAM
– 2 GB of available hard disk

18. Direct Cable Connection
• One device acts as a host and other acts as a guest
• Can also use infrared connection, if both nodes have required
hardware
• All the latest versions of windows provide a software which
allows a user to have a direct serial-to-serial, parallel-to-
parallel, or infrared-to-infrared connection with the other PC.
• To establish a connection using serial ports, a cable known as
null modem is used
• Connection speed of serial data cable connection is very slow
but it’s a cheaper option when NICs are not available

19. Diagnostic and Repair of Physical
Cabling using tools
• Tools can be used to identify the problems and also
troubleshoot these problems
• Various tools available for checking network are:
– Volt-ohm meters (VOMs) – Cable-testing tool used to
measure parameters
• Analog
• Digital

20. Tone generators and probe – I
• Tone generator is a network troubleshooting tool
• Consists of single or multi-tone signal, two test leads and
a 4-conductor modular cable
• Acts like a radio transmitter
• Probe:
– Works like a radio receiver
– Catches a tone when placed near
wire

21. Optical tester
• Fiber optic NICs mostly do not have any lights so making
the diagnosis of the problem becomes little difficult
• Optical tester is used to inspect the quality of the
connections