Networks and the Computer Network Interface Card

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Networks and the Computer Network
Interface Card

• Presented by
• Daniel D. Kochmanski
• Michael A. DiVito

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• Advantages of Networks
• Allow groups of users to exchange information and
  share data.
• Allow easy and efficient communication among
  individuals, including e-mail.
• Allow users to share peripherals such as
  printers, scanners, fax machines, and other
  devices.

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• Local Area Networks (LANs) and Internetworks
• A Local Area Network is also known as an
  Intranet. It works within a limited geographical
  area.
• i.e. within one building or complex
• Internetwork is a network 100 or more computers
  at distances in excess of 1000 feet.

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• Wide Area Networks (WANs) and the Internet
• Wide Area Network (WAN) span distances measured
  in miles.
• i.e. two or more separate LANS linked together
• Internet global WAN internetwork includes
  millions of machines and users on the world wide
  web connected via Network Interface Cards inside
  each computer.

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Network Interface Card (NIC)

• Also known as a Network Adapter.
• Integrated circuit board that plugs into the
  internal circuitry of the computer.
• Allows the members of a local-area network to
  communicate with each other.
• NIC is the physical interface from the computer
  or peripheral to the medium.
• The Medium may be physical cable, such as twisted
  pair wiring, coaxial cable, fiber optic or even
  wireless.

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• Network Cards Convert Data from
• Parallel to Serial, and vice versa
• Most computers use parallel data lines internally
  to send data between the CPU and the adapter
  cards. This is called a Bus.
• Most networking media transmit data in a single
• line, called serial transmission.
• The NIC translates parallel into serial for
  outgoing
• messages and serial into parallel for incoming
• messages.
• Prior to the invention of NICs, data was sent via
• serial ports on the computer.

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First Computer Networks usedSerial
Communications Ports

• Serial Com ports use the RS232 standard
• DB9 or DB25 type connector
• / - 12volts
• Serial means one bit at a time.
• Uses
• Networking computers
• Modem
• Mouse Printers, which are somewhat historical
  now

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Asynchronous Communications

• Both ends agree to a protocol and a speed.
• i.e. Protocol 1 start bit, 1 stop bit,
  1 parity bit 7 data bits. Speed (baud) 300
  - 115,200 bps
• Sender transmits start bit and both transmitting
  and receiving clocks start almost simultaneously.
• Data is transmitted
• Each clock is now working independently. The
  block of data is short enough so that clocks do
  not significantly drift out of sync.
• Next block of data causes the clocks to be reset.

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Sending a character
1 0 0 0 0 0 1
Line Idle
Line Idle
Data Bits
Parity bit
Start bit
Stop bit
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Receiving a character
Receivers clock
Receiver reads voltage at each agreed interval
Clock Start Signal
Line Idle
Line Idle
Data Bits
Start bit
Parity bit
Stop bit
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Parallel Data Transmission

• Used on a Computers Bus where the adapter card
  plugs in.
• i.e. ISA or PCI card bus slots
• Used for the parallel LPT port where the printer
  or scanner plugs in. Parallel ports have
• 5Volt Logic.
• Transmission of 1 Byte at a time or 8 bits.
• Bi-directional capabilities.

Grnd
Grnd
D A T A
Handshake
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• Understanding the Bus inside the Computer
• Bus width refers to number of parallel lines,
  each
• able to move one bit at a time.
• Industry Standard Architecture (ISA) slots have
  an 8-bit or 16-bit bus.
• Peripheral Component Interconnect (PCI) slots
  have a 64 bit bus and are the most popular bus
  used today.

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• The Network Interface Cards Transceiver
• NICs access the transceiver to transmit data onto
  the cable.
• Most NICs include the transceiver.
• Some Ethernet NICs offer multiple interfaces as
  you will soon see but most are designed for a
  specific medium.
• Newer NICs generally have only one type of media
  connector.

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• Network Interface Card Data Packets
• Packets are basic units of data for network
• transmission and reception.
• NICs create packages of data bits called packets,
  then
• Transmit packets serially onto the network
  medium, and
• Act as a gatekeeper, allowing only inbound
  packets intended for its computer via an
  electronic serial number known as a MAC address.

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• The MAC Address
• NICs have a unique identifier, called a Media
  Access Control (MAC) address.
• It is programmed into a ROM chip on the NIC.
• Its a 48-bit number, written as six two-digit
  hexadecimal numbers separated by colons.
• The first part identifies the manufacturer.
• The second part is unique to each NIC.

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• IP Address
• Network Cards can have a second address called an
  IP address.
• IP Address is software configurable.
• IP currently uses 32 bits split into four
  sections separated by dots.
• i.e. 165.255.110.133 These are decimal values.
• Only used in certain network protocols such as
  TCP/IP.

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• Network Protocols
• Network protocols are a common set of data
  transmission rules that
• define how to interpret signals and identify
  individual computers.
• initiate and end networked communication,
• manage information exchange across the network
  medium.
• Protocols include TCP/IP, NetBEUI, IPX/SPX, and
  NWLink

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• OSI Reference Model Structure
• For Networking
• Breaks networked communications into
• seven layers. Layers help clarify the process of
  networking.
• Application
• Presentation
• Session
• Transport
• Network
• Data Link
• Physical

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• Each layer of the OSI model communicates and
• interacts with layers immediately above and
• below it.
• Each layer is responsible for the different
  aspects of data exchange.
• Each layer puts an electronic envelope around
  data
• as it sends it down the layers or removes it
• as it travels up the layers for delivery.

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• Data Flow
• Data is broken into packets or PDUs as it moves
  down the stack.
• PDU stands for protocol data unit, packet data
  unit, or
• payload data unit.
• Packets are a self-contained data structure from
  one
• layer to another.
• At the sending end, each layer adds special
  formatting or
• addressing to the packet.
• At the receiving end, each layer reads the packet
  and strips
• off information added by the corresponding
  layer at the
• sending end.

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Packet Structure

• Each packet contains
• Address of the target machine
• Address of the source machine
• Encapsulated Data
• Error Checking Data
• The receiving machine checks all the packets. It
  accepts those with its address, then replies
  with an acknowledgement.

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Network Interface Card Data Encapsulation
Source Serial (48), Destination Serial (48)
and Protocol type
Source IP (32), Destination IP(32)
Offset in the byte stream, Acknowledgement, port
number, connection number
HELLO THERE
Ethernet Packet
IP Datagram
TCP Header
DATA
HELLO THERE
Trailers
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The Basic Ethernet Frame Format contains the
following seven fields

• Preamble (PRE)Consists of 7 bytes and is an
  alternating pattern of ones and zeros that tells
  the receiving stations that a frame is coming.
• Start-of-frame delimiter (SOF)Consists of 1
  byte.
• Destination address (DA)Consists of 6 bytes and
  identifies which station should receive the
  frame.
• Source addresses (SA)Consists of 6 bytes and it
  identifies the sending station.
• Length/TypeConsists of 4 bytes and indicates
  the number of MAC-client data bytes.
• DataIs a sequence of 1500 bytes maximum.
• Frame check sequence (FCS)Consists of 4 bytes
  and this sequence contains a 32-bit cyclic
  redundancy check (CRC).

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Basic MAC Data Frame Format
Transmission order, left to right, bit serial.
D
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Configuring a Network Interface Card

• This involves three settings
• Interrupt Request line (IRQ)
• Base Input/Output (I/O) port
• Base memory address
• In older computers, the user needed to supply the
  IRQ and base I/O port. Currently Plug and Play
  operating systems have automated this task and
  default values are normally assigned.

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• Driver Software for the NIC
• This is a small specialized program that manages
  communications between the operating system and
  the NIC.
• Earlier, each NIC vendor built its own driver.
• Now, operating system vendors define drivers for
  NICs.

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• Network Layout Design
• The Physical Topology refers to physical layout
  including computers, cables, and other resources
  on the network.
• The Logical topology refers to how data travels
  between computers on the network.

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• Todays network designs are based on three
  topologies
• Ring which connects computers to form a
  continuous circular loop.
• Bus which consists of a series of computers
  connected along a single cable segment.
• Star which connects computers via a central
  connection point known as a hub or switching hub.

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Ring Topology
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Bus Topology
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• Two Types of Coaxial Cable used as a Bus
• Thin Ethernet (also called thinnet) designated by
  the Institute of Electrical and Electronics
  Engineers (IEEE) as 10Base2
• Thick Ethernet (also called thicknet) designated
  by IEEE as 10Base5
• Each of these types of cables is terminated with
  BNC connectors.

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• Understanding IEEE Cable Designations
• 10Base2, for example, refers to a total bandwidth
  of 10 Mbps, baseband signaling, and the maximum
  cable segment length as designated in hundreds of
  meters.
• 10Base2 means 200 meters including patch cables
• 10Base5 means 500 meters

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• Star Topology
• This is the most common topology in todays
  networks.
• It connects computers to a central hub that
  receives and transmits signals to all devices on
  the network.
• Data is addressed and sent in packets to a
  specific MAC address found inside the computers
  Network Interface Card.
• There is ease in troubleshooting because the
  failure of a single computer or cable does not
  affect the entire network.

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Star Topology
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• Unshielded Twisted-Pair (UTP) wire is the most
  common cable used in a Star topology
• IEEE specifies that the most popular form of LAN
  cabling is 10BaseT and 100BaseT
• T means Twisted-Pair wire.
• Normally 4 sets of twisted-pairs 8 wires.
• The maximum length of a 10BaseT or a 100BaseT
  segment is 100 meters or 328 feet. This is called
  the channel link and includes the necessary patch
  cable at each end of the basic link.
• Twisted-Pair wire is also used for telephone
  systems.

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• Twisted-Pair Wire Categories
• Category 1 or 2 carries voice and low speed data
• Category 3 has a bandwidth up to 10 Mbps. Its
  used with older networks such as 10BaseT
  Ethernet. Its still commonly used for telephone
  networks today.
• Category 4 has a bandwidth up to 16 Mbps and was
  formally used for 16 Mbps token ring networks.
• Category 5 has a bandwidth up to 100 Mbps and is
  used with 100BaseT Ethernet.
• Category 5e or 6 is used for Gigabit Ethernet
  known as 1000BaseT.

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• Twisted-Pair Connectors
• Both Shielded Twisted-Pair and Unshielded
  Twisted-Pair wire use RJ-45 modular connectors.
• These are similar to the two wire RJ-11 or four
  wire RJ-14 modular connectors used for the
  telephones in your house.
• RJ-45 is larger and uses eight wires.

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In a star topology, the network gear at the
center can be a hub or a switching hub.

• With a hub, data is sent from one computer to
  every other computer on the hub simultaneously.
• While a switch, as its commonly called,
  maintains address tables for each connection.
• On a switch, traffic is sent
  only to the port for which
  the
  data is destined.
• A switch allows all pairsof stations to
  communicatesimultaneously at topspeed.

HUB
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Simple Router

• This router is connected to the LAN and also has
  a WAN (Internet) connection.
• One purpose for the router is to
  act as a secured gateway protecting your
  network from intruders on the Internet. It uses
  Network Address Translation (NAT) to perform this
  function. NAT simply means that the router has
  its own IP address on your network and also has
  a uniquely different IP address on the Internet.

Router
World Wide Web
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Types of Network Interface Cards

• Fiber-Optic Network Interface Cards work on a
  Fiber-Optic cabled network.
• Infrared networking uses infrared light to
  transmit data from one device to another.
• Wireless network cards with antennas operate on a
  wireless network with a wireless hub.
• Copper wired Network Interface Cards work on coax
  cable or twisted-pair wire.

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10Mbs Ethernet Card with an ISA Slot
Mounting bracket
10baseT RJ45 Socket
Status LEDs
Each network card has a unique 48 bit
identifier known as the Media Access
Control (MAC) number.
10Base2 BNC Connector
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• Electronic Components on the
• Network Interface Card
• Resistors
• Diodes
• Capacitors
• Coils
• Crystals
• Integrated Circuits such as the Realtek Fast
  Ethernet controller chip shown next.

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M
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MAC Layer Block Diagram
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Features of the Ethernet Controller

• Scrambling All the encoded data is passed to the
  data scrambler to reduce EMI by spreading the
  power spectrum using a 10-bit scrambler seed
  loaded at the beginning.
• Equalizer and Baseline Wander High speed signals
  over unshielded (or shielded) twisted pair cable
  will experience attenuation and phase shift.
  These effects depend on the signal frequency,
  cable type, cable length and the cable
  connectors. Robust circuits in the transceiver
  provide reliable adaptive equalizer and baseline
  wander compensation for amplitude attenuation and
  phase shift due to transmission line parasitics.
• 4B/5B encoding procedure Each 4-bit data nibble
  (representing half of a data byte) is mapped into
  a 5-bit binary code-group that is transmitted
  bit-serial over the link.

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Signetics Thompson Ethernet Controller STE10/100A
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Full Duplex and Half Duplex Operation of
Transceiver

• The transceiver can operate in either full duplex
  or half duplex network applications.
• In full duplex, both transmission and reception
  between the network interface cards can take
  place simultaneously.
• In half duplex mode, only one network card can
  transmit at a time.

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System Diagram of the STE10/100A
D
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Types of Digital to Digital Encoding

• Unipolar 1 for high, 0 for low. (common to all
  students)
• Polar
• NRZ Non-Return to Zero
• RZ Return to Zero
• Biphase
• Manchester
• Differential Manchester
• Bipolar
• AMI Alternate Mark Inversion, used on T1 lines
• B8ZS Binary Eight Zero Suppression, used on T1
• HDB3

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Unipolar Encoding
Amplitude
Time
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NRZ-L and NRZ-I Encoding
NRZ-L
NRZ-I
Transition cause next bit is a one.
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RZ Return to Zero Encoding
These transitions can be used for synchronization.
D
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Manchester Encoding

• Each bit period is divided into two equal
  intervals.
• Binary 1 High then Low
• Binary 0 Low then High
• Some network cards send the signal through an
  inverter so this polarity is backwards.

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Differential Manchester Encoding

• Each bit period is divided into two equal
  intervals.
• Binary 1 Lack of voltage transition from
  pervious bit
• Binary 0 Voltage transition from previous bit

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Manchester Encodingvs.Differential Manchester
Encoding
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Summary of the Network Interface Card

• Allows connectivity of one computer to another.
• Controls the communication that takes place
  between computers.
• Utilizes an ethernet controller chip to encode,
  scramble, send and receive data.
• Converts data from parallel to serial for
  transmission to another Network Interface Card.
• Comes in a variety of forms depending on the
  application or network medium.
• In other words, its all pretty simple, huh!

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I hope you enjoyed todays presentation on
Networks and the Network Interface Card by
Daniel D. Kochmanski and Michael A. DiVito

• To view this presentation again please go to
• www.ddktele.com and click on the
• Networks and the Network Interface Card link.
• For other information on this subject please go
• to www.wzrd.com/home/ddk/nic