July 6, 2012
802.3 - Ethernet
Network Interface Cards
Types of Network
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We like to thank Mrs Chaddha for her guidance throughout our
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Oil and Natural Gas Corporation Limited (ONGC) is an Indian
state-owned oil and gas company headquartered in Dehradun, India.
It is one of the largest Asia-based oil and gas exploration and
production companies, and produces around 77% of India’s crude oil
(equivalent to around 30% of the country’s total demand) and around
81% of its natural gas. ONGC is one of the largest publicly traded
companies by market capitalization in India. It is ranked 361st in the
2011 Fortune Global 500 list and is among the Top 250 Global Energy
Company by Platts.
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Our Experience (1)
Through our intership at ONGC we were exposed to the inner
working of the server room at Telbhawan. We examined the working
of the following servers
• AD - Active Director, used for authentication of employees of the
ONGC by verifying theirs CPF numbers.
• DHCP - Dynamic Host Control Protocol, used to allocated
dynamic IP address.
• Anti-virus - It is used for verifying if the client has anti-virus
installed in it.
• IWSS - It is used for scanning the computers in the network
• Blue Coat - It is the Internet distribution proxy
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Our Experience (2)
• WSUS - Windows System Update Server, used to update the
software of all the computers in the network.
• Websense - It ﬁlters the computers for possible threat
The ISP provider to ONGC is BSNL. Four lease lines of 2 Kbps is
connecting Delhi to Dehradun. The main router used in ONGC is IAS
from Cisco. At Dehradun, various routers & switch of Cisco are used.
The intranet of ONGC at Telbhawan is connected to KDMIP though
L3 switches. The optical ﬁber is extended to City Hospital.
We then visited KDMIP which uses SATCOM for communication.
The satellite works in the Ka Band channel with 3 GHz.
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A modem (modulator-demodulator) is a device that modulates an
analog carrier signal to encode digital information, and also
demodulates such a carrier signal to decode the transmitted
information. The goal is to produce a signal that can be transmitted
easily and decoded to reproduce the original digital data.
The most familiar example is a voice band modem that turns the
digital data of a personal computer into modulated electrical signals
in the voice frequency range of a telephone channel. These signals
can be transmitted over telephone lines and demodulated by another
modem at the receiver side to recover the digital data.
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Modems are generally classiﬁed by the amount of data they can send
in a given unit of time, usually expressed in bits per second (bit/s, or
bps). Modems can alternatively be classiﬁed by their symbol rate,
measured in baud. The baud unit denotes symbols per second, or the
number of times per second the modem sends a new signal. Modems
are of two types :
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Fiber Distributed Data Interface (1)
The Fiber Distributed Data Interface (FDDI) topology is ring with
two counter rotating rings for reliability with no hubs. Cable type is
ﬁber-optic. Connectors are specialized. The media access method is
token passing. The maximum length is 100 kilometers. The
maximum number of nodes on the network is 500. Speed is 100
Mbps. FDDI is normally used as a backbone to link other networks.
A typical FDDI network can include servers, concentrators, and links
to other networks.
Devices called concentrators provide functions similar to hubs. Most
concentrators use dual attachment station network cards but single
attachment concentrators may be used to attach more workstations
to the network.
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Fiber Distributed Data Interface (2)
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Fiber Distributed Data Interface (3)
FDDI token passing allows multiple frames to circulate around the
ring at the same time. Priority levels of a data frame and token can
be set to allow servers to send more data frames. Time sensitive data
may also be given higher priority. The second ring in a FDDI network
is a method of adjusting when there are breaks in the cable. The
primary ring is normally used, but if the nearest downstream neighbor
stops responding the data is sent on the secondary ring in attempt to
reach the computer. Therefore a break in the cable will result in the
secondary ring being used.
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Fiber Distributed Data Interface (4)
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Fiber Distributed Data Interface (5)
There are two network cards which are:
• Dual attachment stations (DAS) used for servers and concentrators
are attached to both rings.
• Single Attachment stations (SAS) attached to one ring and used
to attach workstations to concentrators.
A router or switch can link an FDDI network to a local area network
(LAN). Normally FDDI is used to link LANs together since it covers
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In 1973, at Xerox Corporations Palo Alto Research Center (more
commonly known as PARC), researcher Bob Metcalfe designed and
tested the ﬁrst Ethernet network. While working on a way to link
Xeroxs ”Alto” computer to a printer, Metcalfe developed the physical
method of cabling that connected devices on the Ethernet as well as
the standards that governed communication on the cable. Ethernet
has since become the most popular and most widely deployed network
technology in the world. Many of the issues involved with Ethernet
are common to many network technologies, and understanding how
Ethernet addressed these issues can provide a foundation that will
improve your understanding of networking in general.
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The Ethernet standard has grown to encompass new technologies as
computer networking has matured, but the mechanics of operation for
every Ethernet network today stem from Metcalfes original design.
The original Ethernet described communication over a single cable
shared by all devices on the network. Once a device attached to this
cable, it had the ability to communicate with any other attached
device. This allows the network to expand to accommodate new
devices without requiring any modiﬁcation to those devices already on
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Ethernet Cabling (1)
Figure: Ethernet Cabling
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Ethernet Cabling (2)
Figure: The most common kinds of Ethernet cabling
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• Topology - Physical and logical network layout
◦ Physical actual layout of the computer cables and other network
◦ Logical the way in which the network appears to the devices that use
• Common topologies
◦ Bus, ring, star, mesh and wireless
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• Uses a trunk or backbone to which all of the computers on the
• Uses a trunk or backbone to which all of the computers on the
• Coaxial cablings ( 10Base-2, 10Base5) were popular options years
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• Cable faults are easily located,
making troubleshooting easier
• Ring network are moderately
easy to install
• Expansion to the network can
cause network disruption
• A single break in the cable can
disrupt the entire network
Figure: Bus Topology
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• All computers/devices connect to a central device called hub or
• Each device requires a single cable
• point-to-point connection between the device and hub.
• Most widely implemented
• Hub is the single point of failure
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• Easily expanded without
disruption to the network
• Cable failure aﬀects only a
• Easy to troubleshoot & isolate
• Requires more cable
• A central connecting device
allows for a single point of
• More diﬃcult to implement
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• Each computer connects to every other
• High level of redundancy.
• Rarely used
◦ Wiring is very complicated
◦ Cabling cost is high
◦ Troubleshooting a failed cable is tricky
◦ A variation hybrid mesh create point to point connection between
speciﬁc network devices, often seen in WAN implementation.
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• Provides redundant path
• The network can be expanded
without to current uses
• Requires more cable than the
other LAN topologies
Figure: Mesh Topology
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• Do not require physical cabling
• Particularly useful for remote access for laptop users
• Eliminate cable faults and cable breaks.
• Signal interference and security issue.
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• Allows for wireless remote
• Network can be expanded
without disruption to current
• Potential security issues
associated with wireless
• Limited speed in comparison to
other network topologies
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• A network interface card, more commonly referred to as a NIC, is a
device that allows computers to be joined together in a LAN, or
local area network .
• The network interface card acts as the liaison for the machine to
both send and receive data on the LAN .
• In computer networking, a NIC provides the hardware interface
between a computer and a network.
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Figure: Network cards are typically available in 10/100/1000 Mbit/s
varieties. This means they can support a notional maximum transfer rate of
10, 100 or 1000 Megabits per second
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• Most computer networks transfer data across a medium at a ﬁxed
rate, often faster than the speed at which computers can process
• To accommodate the mismatch in speed, each computer attached
to a network contain special purpose hardware known as a network
interface card (NIC).
• The NIC functions like an I/O device: it is built for a speciﬁc
• It handles the details of frame transmission or reception without
requiring the CPU to process each bit.
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• A computer or device on a network can be reached by its MAC
(media access control) address through the NIC card.
• Every Ethernet network card has a unique 48-bit serial number
called a MAC address, which is stored in ROM carried on the card.
• The MACs on the network are used to direct traﬃc between the
• An example of a MAC address: A1B2C3D4E5F6
• The ﬁrst 6 hex digits in the MAC address is the OUI
(organizationally unique identiﬁer), assigned by the IEEE to each
manufacturer (e.g. Cisco, Intel etc).
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• The rest of the MAC address can be assigned in any way by the
manufacturer to the individual networking devices that it
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• The back plate of the network interface card features a port that
looks similar to a phone jack, but is slightly larger.
• A network card typically has a twisted pair, BNC, or AUI socket
where the network cable is connected, and a few LEDs to inform
the user of whether the network is active, and whether or not there
is data being transmitted on it.
• That port accommodates an Ethernet cable, which resembles a
thicker version of a standard telephone line.
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Figure: Network Interface Card for connection of a computer to an Ethernet
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...on a Network
• The card implements the electronic circuitry required to
communicate using a speciﬁc physical layer and data link layer
standard such as Ethernet or token ring.
• This provides a base for a full network protocol stack, allowing
communication among small groups of computers on the same
LAN and large-scale network communications through routable
protocols, such as IP.
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Types of Network
• Local Area Network
• Wide Area Netwok
• Metropolitan Area Network
• Wireless Networks
• Home Networks
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A LAN connects network devices over a relatively short distance. A
networked oﬃce building, school, or home usually contains a single
LAN, though sometimes one building will contain a few small LANs
(perhaps one per room), and occasionally a LAN will span a group of
In TCP/IP networking, a LAN is often but not always implemented as
a single IP subnet.
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Figure: An isolated IAN connecting 12 computers to a hub in a closet
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As the term implies, a WAN spans a large physical distance. The
Internet is the largest WAN, spanning the Earth.
A WAN is a geographically-dispersed collection of LANs. A network
device called a router connects LANs to a WAN. In IP networking, the
router maintains both a LAN address and a WAN address.
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Wireless network refers to any type of computer network that is not
connected by cables of any kind. It is a method by which homes,
telecommunications networks and enterprise (business) installations
avoid the costly process of introducing cables into a building, or as a
connection between various equipment locations. Wireless
telecommunications networks are generally implemented and
administered using a transmission system called radio waves. This
implementation takes place at the physical level (layer) of the OSI
model network structure.
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Types of wireless networks (1)
• Wireless PAN
◦ Wireless personal area networks (WPANs) interconnect devices within
a relatively small area that is generally within a person’s reach. For
example, both Bluetooth radio and invisible infrared light provides a
WPAN for interconnecting a headset to a laptop. Wi-Fi PANs are
becoming commonplace as equipment designers start to integrate
Wi-Fi into a variety of consumer electronic devices.
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Types of wireless networks (2)
• Wireless LANs
◦ A wireless local area network (WLAN) links two or more devices over
a short distance using a wireless distribution method, usually providing
a connection through an access point for Internet access. The use of
spread-spectrum or OFDM technologies may allow users to move
around within a local coverage area, and still remain connected to the
network. Products using the IEEE 802.11 WLAN standards are
marketed under the Wi-Fi brand name. Fixed wireless technology
implements point-to-point links between computers or networks at
two distant locations, often using dedicated microwave or modulated
laser light beams over line of sight paths. It is often used in cities to
connect networks in two or more buildings without installing a wired
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Types of wireless networks (3)
• Wireless mesh network
◦ A wireless mesh network is a wireless network made up of radio nodes
organized in a mesh topology. Each node forwards messages on behalf
of the other nodes. Mesh networks can ”self heal”, automatically
re-routing around a node that has lost power.
• Wireless MAN
◦ Wireless metropolitan area networks are a type of wireless network
that connects several wireless LANs. WiMAX is a type of Wireless
MAN and is described by the IEEE 802.16 standard.
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Types of wireless networks (4)
• Wireless WAN
◦ Wireless wide area networks are wireless networks that typically cover
large areas, such as between neighboring towns and cities, or city and
suburb. These networks can be used to connect branch oﬃces of
business or as a public internet access system. The wireless
connections between access points are usually point to point
microwave links using parabolic dishes on the 2.4GHz band, rather
than omnidirectional antennas used with smaller networks. A typical
system contains base station gateways, access points and wireless
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Other Types of Area Networks (1)
• Metropolitan Area Network - a network spanning a physical area
larger than a LAN but smaller than a WAN, such as a city. A
MAN is typically owned an operated by a single entity such as a
government body or large corporation.
• Campus Area Network - a network spanning multiple LANs but
smaller than a MAN, such as on a university or local business
• Storage Area Network - connects servers to data storage devices
through a technology like Fibre Channel.
• System Area Network - links high-performance computers with
high-speed connections in a cluster conﬁguration. Also known as
Cluster Area Network.
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Virtually all networks in use today are based in some fashion on the
Open Systems Interconnection (OSI) standard. OSI was developed in
1984 by the International Organization for Standardization (ISO), a
global federation of national standards organizations representing
approximately 130 countries.
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Think of the seven layers as the assembly line in the computer. At
each layer, certain things happen to the data that prepare it for the
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• Application - This is the layer that actually interacts with the
operating system or application whenever the user chooses to
transfer ﬁles, read messages or perform other network-related
• Presentation - Layer 6 takes the data provided by the Application
layer and converts it into a standard format that the other layers
• Session - Layer 5 establishes, maintains and ends communication
with the receiving device.
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Transport Set (1)
• Transport - This layer maintains ﬂow control of data and provides
for error checking and recovery of data between the devices. Flow
control means that the Transport layer looks to see if data is
coming from more than one application and integrates each
application’s data into a single stream for the physical network.
• Network - The way that the data will be sent to the recipient
device is determined in this layer. Logical protocols, routing and
addressing are handled here.
• Data - In this layer, the appropriate physical protocol is assigned to
the data. Also, the type of network and the packet sequencing is
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Transport Set (2)
• Physical - This is the level of the actual hardware. It deﬁnes the
physical characteristics of the network such as connections, voltage
levels and timing.
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Beneﬁts of the OSI Model
By separating the network communications into logical smaller pieces,
the OSI model simpliﬁes how network protocols are designed. The
OSI model was designed to ensure diﬀerent types of equipment (such
as network adapters, hubs, and routers) would all be compatible even
if built by diﬀerent manufacturers. A product from one network
equipment vendor that implements OSI Layer 2 functionality, for
example, will be much more likely to interoperate with another
vendor’s OSI Layer 3 product because both vendors are following the
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An IP address is an identiﬁer that is assigned at the Internet layer to
an interface or a set of interfaces. Each IP address can identify the
source or destination of IP packets. For IPv4, every node on a network
has one or more interfaces, and you can enable TCP/IP on each of
those interfaces. When you enable TCP/IP on an interface, you
assign it one or more logical IPv4 addresses, either automatically or
manually. The IPv4 address is a logical address because it is assigned
at the Internet layer and has no relation to the addresses that are
used at the Network Interface layer. IPv4 addresses are 32 bits long
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Types of IPv4 Addresses
Internet standards deﬁne the following types of IPv4 addresses:
Assigned to a single network interface located on a speciﬁc subnet;
used for one-to-one communication.
Assigned to one or more network interfaces located on various
subnets; used for one-to-many communication
Assigned to all network interfaces located on a subnet; used for
one-to-everyone on a subnet communication.
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• Most IP addresses are public addresses. Public addresses are
registered as belonging to a speciﬁc organization.
• Internet Service Providers (ISP) and extremely large organizations
in the U.S. obtain blocks of public addresses from the American
Registry for Internet Numbers (ARIN http://www.arin.net). Other
organizations obtain public addresses from their ISPs.
• There are ARIN counterparts in other parts of the world, and all of
these regional registration authorities are subject to the global
Internet Assigned Numbers Authority (IANA http://www.iana.org).
• Public IP addresses are routed across the Internet, so that hosts
with public addresses may freely communicate with one another
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• RFC 1918 designates the following as private addresses.
◦ Class A range: 10.0.0.0 through 10.255.255.255.
◦ Class B range: 172.16.0.0 through 172.31.255.255.
◦ Class C range: 192.168.0.0 through 192.168.255.255.
• Private addresses may be used by any organization, without any
requirement for registration.
• Because private addresses are ambiguous - cant tell where theyre
coming from or going to because anyone can use them - private
addresses are not permitted to be routed across the Internet
• ISPs block private addresses from being routed across their
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Classful IP Addressing (1)
Three main classes
• Class A networks
◦ First octet values range from 1 through 126.
◦ First octet starts with bit 0
◦ Network mask is 8 bits, written /8 or 255.0.0.0.
◦ 184.108.40.206 through 220.127.116.11 are class A networks with 16777214 hosts
• Class B networks
◦ First octet values range from 128 through 191.
◦ First octet starts with binary pattern 10.
◦ Network mask is 16 bits, written /16 or 255.255.0.0.
◦ 18.104.22.168 through 22.214.171.124 are class B networks, with 65534 hosts
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Classful IP Addressing (2)
• Class C networks
◦ First octet values range from 192 through 223.
◦ First octet starts with binary pattern 110.
◦ Network mask is 24 bits, written /24 or 255.255.255.0.
◦ 192.0.0.0 through 126.96.36.199 are class C networks, with 254 hosts
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Two additional classes and reserved addresses
• Class D addresses
◦ First octet values range from 224 through 239.
◦ First octet starts with binary pattern 1110.
◦ Class D addresses are multicast addresses, which will not be discussed
in this tutorial.
• Class E addresses
◦ Essentially everything thats left.
◦ Experimental class, which will not be discussed in this tutorial.
• Reserved addresses
◦ 0.0.0.0 is the default IP address, and it is used to specify a default
route. The default route will be discussed later.
◦ Addresses beginning with 127 are reserved for internal loopback
addresses. It is common to see 127.0.0.1 used as the internal
loopback address on many devices.
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Subnet Masks (1)
Extending the classful network mask
• Subnet masks are used to make classful networks more manageable
and eﬃcient, by creating smaller subnets and reducing the number
of host addresses per subnet to what is actually required.
• Subnet masks were ﬁrst used on class boundaries.
◦ Take class A network 10.0.0.0 with network mask 255.0.0.0.
◦ Add additional 8 subnet bits to network mask.
◦ New subnet mask is 255.255.0.0.
◦ New subnets are 10.0.0.0, 10.1.0.0, 10.2.0.0, and so on with 65534
host addresses per subnet. Still too many hosts per subnet.
◦ Take class A network 10.0.0.0 with network mask 255.0.0.0.
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Subnet Masks (2)
◦ Add additional 16 subnet bits to network mask.
◦ New subnet mask is 255.255.255.0
◦ New subnets are 10.0.0.0, 10.0.1.0, 10.0.2.0, ..., 10.1.0.0, 10.1.1.0,
10.1.2.0, ..., 10.2.0.0, 10.2.1.0, 10.2.2.0, and so on with 254 host
addresses per subnet.
◦ Take class B network 172.16.0.0 with network mask 255.255.0.0.
◦ Add additional 8 subnet bits to network mask.
◦ New subnet mask is 255.255.255.0
◦ New subnets are 172.16.0.0, 172.16.1.0, 172.16.2.0, and so on with
254 host addresses per subnet.
• As shown in these examples...
◦ A class A network can be subnetted to create 256 (28
) /16 subnets.
◦ A class A network can be subnetted to create 65536 (216
) /24 subnets.
◦ A class Bnetwork can be subnetted to create 256 (28
) /24 subnets.
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Short for Domain Name System (or Service or Server), an Internet
service that translates domain names into IP addresses. Because
domain names are alphabetic, they’re easier to remember. The
Internet however, is really based on IP addresses.
Every time you use a domain name, therefore, a DNS service must
translate the name into the corresponding IP address. For example,
the domain name www.example.com might translate to
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Figure: The DNS client program sends a request to a DNS server to map
the e-mail address to the corresponding IP address
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A name space that maps each address to a unique name can be
organized in two ways: ﬂat or hierarchical.
Flat Name Space
In a ﬂat name space, a name is assigned to an address. A name in
this space is a sequence of characters without structure. The main
disadvantage of a ﬁat name space is that it cannot be used in a large
system such as the Internet because it must be centrally controlled to
avoid ambiguity and duplication.
Hierarchical Name Space
In a hierarchical name space, each name is made of several parts.
The ﬁrst part can deﬁne the nature of the organization, the second
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part can deﬁne the name of an organization, the third part can deﬁne
departments in the organization, and so on. For example, assume two
colleges and a company call one of their computers challenger. The
ﬁrst college is given a name by the central authority such as jhda.edu,
the second college is given the name berkeley.edu, and the company is
given the name smart. com. When these organizations add the name
challenger to the name they have already been given, the end result is
three distinguishable names: challenger.jhda.edu,
challenger.berkeley.edu, and challenger.smart.com. The names are
unique without the need for assignment by a central authority.
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Figure: The domain names are always read from the node up to the root
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Figure: The last label is the label of the root (null) as below
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Figure: A domain is a subtree of the domain name space. The name of the
domain is the domain name of the node at the top of the subtree
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DISTRIBUTION OF NAME SPACE
Hierarchy of Name Servers
The solution to these problems is to distribute the information
among many computers called DNS servers. One way to do this is to
divide the whole space into many domains based on the ﬁrst level.
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Since the complete domain name hierarchy cannot be stored on a
single server, it is divided among many servers. What a server is
responsible for or has authority over is called a zone. The server
makes a database called a zone ﬁle and keeps all the information for
every node under that domain.
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A root server is a server whose zone consists of the whole tree.
There are several root servers, each covering the whole domain name
Primary and Secondary Servers
A primary server loads all information from the disk ﬁle; the
secondary server loads all information from the primary server. When
the secondary downloads information from the primary, it is called
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Figure: DNS is a protocol that can be used in diﬀerent platforms. In the
Internet, the domain name space (tree) is divided into three diﬀerent
sections: generic domains, country domains, and the inverse domain
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Figure: The generic domains deﬁne registered hosts according to their
generic behavior. Each node in the tree deﬁnes a domain, which is an index
to the domain name space database
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Figure: The country domains section uses two-character country
abbreviations (e.g., us for United States). Second labels can be
organizational, or they can be more speciﬁc, national designations.
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The inverse domain is used to map an address to a name. This may
happen, for example, when a server has received a request from a
client to do a task. Although the server has a ﬁle that contains a list
of authorized clients, only the IP address of the client (extracted from
the received IP packet) is listed. The server asks its resolver to send a
query to the DNS server to map an address to a name to determine if
the client is on the authorized list.
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