A network is a set of devices connected by physical media links. A network is recursively is a connection
of two or more nodes by a physical link or two or more networks connected by one or more nodes.

A protocol is a set of rules that govern all aspects of information communication.

At the lowest level, a network can consist of two or more computers directly connected by some physical
medium such as coaxial cable or optical fiber. Such a physical medium is called as Link.

A network can consist of two or more computers directly connected by some physical medium such as
coaxial cable or optical fiber. Such a physical medium is called as Links and the computer it connects is
called as Nodes.

A node that is connected to two or more networks is commonly called as router or Gateway. It generally
forwards message from one network to another.

a. Number of Users
b. Type of transmission medium
c. Hardware
d. Software

The duration of time it takes to send a message from one end of a network to the other and back, is called
RTT.

a. Physical Layer
b. Data Link Layer
c. Network Layer
d. Transport Layer
e. Session Layer
f. Presentation Layer
g. Application Layer.

a. Physical Layer
b. Data link Layer and
c. Network Layers

a. Session Layer
b. Presentation Layer and
c. Application Layer

In networking and in other areas, a task is often begun before the previous task has ended. This is known
as pipelining.

A technique called piggybacking is used to improve the efficiency of the bidirectional protocols. When a
frame is carrying data from A to B, it can also carry control information about arrived (or lost) frames
from B; when a frame is carrying data from B to A, it can also carry control information about the arrived
(or lost) frames from A.

(i) Broadcast and (ii) point-to-point

Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range
is called the bandwidth.

It is a simple protocol used to exchange information between the routers.

A generic term for section of a large networks usually separated by a bridge or router.

The address for a device as it is identified at the Media Access Control (MAC) layer in the network
architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

Multiplexing is the process of dividing a link, the physical medium, into logical channels for better
efficiency. Here medium is not changed but it has several channels instead of one.

It is the mode of communication between two devices in which flow of data is unidirectional. i.e. one can
transmit and other can receive.
E.g. keyboard and monitor.

It is the mode of communication between two devices in which flow of data is bi-directional but not at the
same time. i.e. each station can transmit and receive but not at the same time.
E.g. walkie-talkies are half-duplex system.

It is the mode of communication between two devices in which flow of data is bi-directional and it occurs
simultaneously. Here signals going in either direction share the capacity of the link.
E.g. telephone

It is the process of obtaining amplitude of a signal at regular intervals.

It is a serial mode of transmission.
In this mode of transmission, each byte is framed with a start bit and a stop bit. There may be a variable
length gap between each byte.

It is a serial mode of transmission. In this mode of transmission, bits are sent in a continuous stream
without start and stop bit and without gaps between bytes. Regrouping the bits into meaningful bytes is the
responsibility of the receiver.

Multiplexing is of three types. Frequency division multiplexing and wave division multiplexing is for
analog signals and time division multiplexing is for digital signals.

The transmission media is broadly categorized into two types
i)Guided media(wired)
i)Unguided media(wireless)

Data link layer is responsible for carrying packets from one hop (computer or router) to the next. The
duties of data link layer include packetizing, addressing, error control, flow control, medium access
control.

Errors can be categorized as a single-bit error or burst error. A single bit error has one bit error per data
unit. A burst error has two or more bits errors per data unit.

Redundancy is the concept of sending extra bits for use in error detection. Three common redundancy
methods are parity check, cyclic redundancy check (CRC), and checksum.

In parity check, a parity bit is added to every data unit so that the total number of 1s is even (or odd for
odd parity).Simple parity check can detect all single bit errors. It can detect burst errors only if the total
number of errors in each data unit is odd. In two dimensional parity checks, a block of bits is divided into
rows and a redundant row of bits is added to the whole block.

C RC appends a sequence of redundant bits derived from binary division to the data unit. The divisor in
the CRC generator is often represented as an algebraic polynomial.

The hamming code is an error correction method using redundant bits. The number of bits is a function of
the length of the data bits. In hamming code for a data unit of m bits, we use the formula 2r >= m+r+1 to
determine the number of redundant bits needed. By rearranging the order of bit transmission of the data
units, the hamming code can correct burst errors.

In stop and wait ARQ, the sender sends a frame and waits for an acknowledgement from the receiver
before sending the next frame.

Network control protocol is a set of protocols to allow the encapsulation of data coming from network
layer protocol that requires the services of PPP

To reduce the possibility of collision CSMA method was developed. In CSMA each station first listen to
the medium (Or check the state of the medium) before sending. It can’t eliminate collision.

It is a wireless LAN technology designed to connect devices of different functions such as telephones,
notebooks, computers, cameras, printers and so on.

The internet address (IP address) is 32bits that uniquely and universally defines a host or router on the
internet. The portion of the IP address that identifies the network is called netid. The portion of the IP
address that identifies the host or router on the network is called hostid.

It is the method used to solve the channel allocation problem .It is used for:
i)ground based radio broadcasting
ii)In a network in which uncoordinated users are competing for the use of single channel.
It is of two types:
1.Pure aloha
2.Slotted aloha

It is an electronic downbridge which is used to enhance the security of a network. It’s configuration has
two components.
i)Two routers
ii)Application gateway

the packets traveling through the LAN are inspected here and packets meeting certain criteria are forwarded and others are dropped.

A receiver receives a signal before it becomes too weak or corrupted, regenerates the original bit pattern,
and puts the refreshed copy back onto the link. It operates on physical layer of OSI model.

They divide large network into smaller components. They can relay frames between two originally
separated LANs. They provide security through partitioning traffic. They operate on physical and data link
layer of OSI model.

ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts
and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to
test whether a destination is reachable and responding. It also handles both control and error messages.

FDM is an analog technique that can be applied when the bandwidth of a link is greater than the combined
bandwidths of the signals to be transmitted.

WDM is conceptually the same as FDM, except that the multiplexing and demultiplexing involve light
signals transmitted through fiber optics channel.

TDM is a digital process that can be applied when the data rate capacity of the transmission medium is
greater than the data rate required by the sending and receiving devices.

a. Divide the data into sections
b. Add the sections together using 1's complement arithmetic
c. Take the complement of the final sum, this is the checksum.

The correction of errors is more difficult than the detection. In error detection, checks only any error has
occurred. In error correction, the exact number of bits that are corrupted and location in the message are
known. The number of the errors and the size of the message are important factors.

The protocols defined in application layer are
• TELNET
• FTP
• SMTP
• DNS

The protocols defined in transport layer are
• TCP
• UDP

In client server model ,the client runs a program to request a service and the server runs a program to
provide the service. These two programs communicate with each other. One server program can provide
services to many client programs.

TELNET is a client –server application that allows a user to log on to a remote machine, giving the user
access to the remote system. TELNET is an abbreviation of terminal Network.

It is the main protocol used to access data on the World Wide Web .the protocol transfers data in the form
of plain text, hypertext,audio,video,and so on. It is so called because its efficiency allows its use in a
hypertext environment where there are rapid jumps from one document to another.

World Wide Web is a repository of information spread all over the world and linked together. It is a unique
combination of flexibility,portability,and user-friendly features .The World Wide Web today is a
distributed client-server service,in which a client using a browser can access a service using a server. The
service provided is distributed over many locations called web sites.

The process that allows a network to self-repair networks problems. The stations on the network notify the
other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring
and FDDI networks.

A method for providing fault tolerance by using multiple hard disk drives.

NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote
computer and it hides the networking hardware from applications.
NETBEUI is NetBIOS extended user interface. A transport protocol designed by microsoft and IBM for
the use on small subnets.

The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical
address, used by a host or a router to find the physical address of another host on its network by sending a
ARP query packet that includes the IP address of the receiver.
The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it
knows only its physical address.

The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

Server-based network: provide centralized control of network resources and rely on server computers to
provide security and network administration
Peer-to-peer network: computers can act as both servers sharing resources and as clients using the
resources.

BUS topology: In this each computer is directly connected to primary network cable in a single line.
Advantages: Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology: In this all computers are connected using a central hub.
Advantages: Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical
problems.
RING topology: In this all computers are connected in loop.
Advantages: All computers have equal access to network media, installation can be simple, and signal does
not degrade as much as in other topologies because each computer regenerates it.

A network in which there are multiple network links between computers to provide multiple paths for data
to travel.

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband
transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

Packet filter is a standard router equipped with some extra functionality. The extra functionality allows
every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded
normally. Those that fail the test are dropped.

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a
uniform rate, congestion would be less common. Another open loop method to help manage congestion is
forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

It is an authentication service developed at the Massachusetts Institute of Technology. Kerberos uses
encryption to prevent intruders from discovering passwords and gaining unauthorized access to files.

When the computers on the network simply listen and receive the signal, they are referred to as passive
because they don’t amplify the signal in any way. Example for passive topology - linear bus.

a. Security/Encapsulation
b. Distributed database
c. Faster Problem solving
d. Security through redundancy
e. Collaborative Processing

a. Frequency of failure
b. Recovery time of a network after a failure

It is possible that a switch receives packets faster than the shared link can accommodate and stores in its
memory, for an extended period of time, then the switch will eventually run out of buffer space, and some
packets will have to be dropped and in this state is said to congested state.

Hidden or administrative shares are share names with a dollar sign ($) appended to their names.
Administrative shares are usually created automatically for the root of each drive letter. They do not
display in the network browse list.

They are Application, Presentation, Session, Transport, Network, Data link, and Physical.

The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical
address, used by a host or a router to find the physical address of another host on its network by sending a
ARP query packet that includes the IP address of the receiver. The reverse address resolution protocol
(RARP) allows a host to discover its Internet address when it knows only its physical address.

Clients and Servers are separate logical entities that work together over a network to accomplish a task.
Many systems with very different architectures that are connected together are also called Client/Server.

It is the 48 bit hardware address of LAN card. MAC address is usually stored in ROM on the network adapter
card and it is unique.

LAN card should be connected:

Root (partition on which window is installed) should in NTFS

Server should be configured with a static IP address.

Start ==> RUN ==> DCPROMO.

Ping 127.0.0.1

If getting reply its fine.

Workgroup:

(I)Every PC is responsible for its security own.

(ii)No centralize administration

(iii)Main aim to save hardware recourse

(iv)Best suite in school, training institute, cyber café

Domain:

(I)Server is responsible for data safety.

(ii)Centralize administration

(iii)Main aim is to secure data

(iv)Best suite in company environments

ipconfig.

Ping.

A special feature that will map network resource to my computer.

Most large businesses, organizations, and universities these days use a proxy server. This is a server that
all computers on the local network have to go through before accessing information on the Internet. By
using a proxy server, an organization can improve the network performance and filter what users
connected to the network can access.

NTDS.

International Networking.

Linux doesn’t support windows file system that contain partition scheme. It (Linux) has its own file
system known as ext2, and ext3. it will install only on it. In Linux file system it will install on / (root)
partition.

It’s the hard disk space that is used as RAM for fast processing. In window it’s known as virtual memory
and could be set as per retirement via this path .

My Computer ==> properties ==> advance

Complementary metal oxide semiconductor

Start ==> Run ==> Command ==>ipconfig.

Internet Protocol (IP) is an unreliable, best effort delivery, connectionless protocol used for transmitting
and receiving data between hosts in a TCP/IP network.

Hub is a layer 1 device. It will out the signal from all of its port except the one from where its insert. It is
unable to detect the collision. It works on single collision and single broadcast domain. Switch is layer 2
device. It maintains a CAM table that store the MAC address of devices attached on its port. CAM table is
used to make the forwarding decision. It works on per port collision and single broadcast domain.

Layer is a completely logical partition of PDU (protocol data unit) process. That define how the
information is travel form one computer to other over the network.

It is combination of two protocols TCP and IP. It is used for reliable data transfer.

An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into
the computer by a boot program, manages all the other programs in a computer. It provides a platform to
application software.

The collection of mostly used software released in package Form Company. For Example MsOffice that
contain word, power point, Excel, etc.

COM ".com" stands for "commercial".

NET ".NET" stands for "network"

ORG ".org" stands for "organization"

INFO ".info" stands for "information"

BIZ ".biz" stands for "business".

IN 'IN' stands for India. The 'IN' is a 2letter country code for India.

In a ring topology, device one connects to device two, device two connects to device three, and so on to
the last device, which connects back to device one.

Generally coaxial and TP media is used in LAN networking.

STP cable is mostly used by IBM? it has an extra cover over each pair.

UTP cable is used in star topology. It has a single cover over all pair.

PING stand for Packet Internet Grouper.

10Base2— An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses
baseband signaling, with a contiguous cable segment length of 100 meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses
baseband signaling, with 5 continuous segments not exceeding 100 meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses
baseband signaling and twisted pair cabling.

An unspecified passive open has the server waiting for a connection request from a client. A fully
specified passive open has the server waiting for a connection from a specific client.

A TCB is a complex data structure that contains a considerable amount of information about each
connection.

A Management Information Base is part of every SNMPmanaged device. Each SNMP agent has the MIB
database that contains information about the device's status, its performance, connections, and
configuration. The MIB is queried by SNMP.

Anonymous FTP enables users to connect to a host without using a valid login and password. Usually,
anonymous FTP uses a login called anonymous or guest, with the password usually requesting the user's
ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on
the host without having to go to the trouble of setting up logins for them all. Anonymous FTP systems
usually have strict controls over the areas an anonymous user can access.

A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a
pseudo tty, no connection can take place.

The Mount protocol returns a file handle and the name of the file system in which a requested file resides.
The message is sent to the client from the server after reception of a client's request.

External Data Representation is a method of encoding data within an RPC message, used to ensure that the
data is not system dependent.

OSI model was developed in February1980 that why these also known as 802.XX Standard (Notice 80
means ==> 1980, 2means ==> February)

Active Directory Structure

Computer to computer ==> cross

Switch/hub to switch/hub ==>cross

Computer to switch/hub ==>standard

In computer it's known as com port and could be available in 9pin or 25 pin. On router it have 60 pins.

It's a unique 32 bits software address of a node in a network.

Three ranges of IP addresses have been reserved for private address and they are not valid for use on the
Internet. If you want to access internet with these address you must have to use proxy server or NAT
server (on normal cases the role of proxy server is played by your ISP.).If you do decide to implement a
private IP address range, you can use IP addresses from any of the following classes:

Class A 10.0.0.0 10.255.255.255

Class B 172.16.0.0 172.31.255.255

Class C 192.168.0.0 192.168.255.255.

A public IP address is an address leased from an ISP that allows or enables direct Internet communication.

Reduce the size of the routing tables.

Reduce network traffic. Broadcast traffic can be isolated within a single logical network.

Provide a way to secure network traffic by isolating it from the rest of the network.

With static IP addressing, a computer (or other device) is configured to always use the same IP address.
With dynamic addressing, the IP address can change periodically and is managed by a centralized network
service

Automatic private IP addressing (APIPA) is a feature mainly found in Microsoft operating systems.
APIPA enables clients to still communicate with other computers on the same network segment until an IP
address can be obtained from a DHCP server, allowing the machine to fully participate on the network.
The range of these IP address are the 169.254.0.1 to 169.254.255.254 with a default Class B subnet mask
of 255.255.0.0.

The LMHOSTS file is a static method of resolving NetBIOS names to IP addresses in the same way that
the HOSTS file is a static method of resolving domain names into IP addresses. An LMHOSTS file is a
text file that maps NetBIOS names to IP addresses? it must be manually configured and updated.

A scope is a range, or pool, of IP addresses that can be leased to DHCP clients on a given subnet.

An FQDN contains (fully qualified domain name) both the hostname and a domain name. It uniquely
identifies a host within a DNS hierarchy.

DNS servers often must communicate with DNS servers outside of the local network. A forwarder is an
entry that is used when a DNS server receives DNS queries that it cannot resolve locally. It then forwards
those requests to external DNS servers for resolution.

NSLOOKUP [192.168.0.1]

[Ip of target computer].

Make changes in the hosts file in C:\WINDOWS\system32\drivers\etc The Hosts file is looked at first
before going out to the DNS (Domain Name Service) servers. you have to put the following on new lines
at the end of hosts file:

127.99.11.01 example.com

127.99.11.01 www.example.com

Put shortcut to notepad.exe in Send To folder. It is speed up work with different files like hosts,
configuration

files. Location of this folder is

C:\Documents and Settings\Default User\send to.

Open it and create shortcut of notpad.exe

FTP is short for File Transfer Protocol. This is the protocol used for file transfer over the Internet.

Click Start, point to All Programs, point to Accessories, point to System Tools, and then click Backup.
Bedside's it?

If OS support then Select Drive ==> properties ==> back up now

Router is a device that is used to connect two different networks.

Start ==> Run ==> DCPROMO

Or

Start==> Configure your server ==> add/Remove a Role

A central component of the Windows platform, Active Directory service provides the means to manage the
identities and relationships that make up network environments.

Check the network cable it should be plugged

Check root partition it should be in NTFS

Check IP of server it should be configured statically.

On Server Configure ADS (for example it’s configured with xyz.com)

On Client

Log in form local administrator account

My Computer ==> Properties ==> Computer Name ==> Change

==>Domain ==>xyz.com ==> username Administrator (of xyz.com)

Password xxxxxxxxxxx (of admin of xyz.com)

Welcome to xyz.com ==> Restart the computer.

Not every time but you are required a properly configured user account in domain controller security policy.

International standard organization.

Open System Interconnection.

Dynamic host configuration protocol. To configure it on Server

Configure your server ==>Add/Remove a role ==>DHCP server ==>complete the wizard

Start ==> Administrative tools ==> DHCP ==>New scope ==> Wizard

Now authorized this server and do activate it On client

Local area network ==> tcp/ip ==> obtain ip automatically

Obtain DNS automatically.

A physical topology describes how devices are physically cabled together. A logical topology describes
how devices communicate across the physical topology

A point to point topology has a single connection between two devices.

In a star topology, a central device has many point to point connections to other devices.

A bus topology uses a single connection or wire to connect all devices.

In a ring topology, device one connects to device two, device two connects to device three, and so on to the
last device, which connects back to device one.

For data sharing

To accumulate hardware resource.

There are lots of advantages from build up a network, but the three big facts are

File Sharing

From sharing files you can view, modify, and copy files stored on a different computer on the network just
as easily as if they were stored on your computer.

Resource Sharing

Resources such as printers, fax machines, Storage Devices (HDD, FDD and CD Drives), Webcam,
Scanners, Modem and many more devices can be shared.

Program Sharing

Just as you can share files on a network, you can often also share program on a network. For example, if
you have the right type of software license, you can have a shared copy of Microsoft Office, or some other
program, and keep it on the network server, from where it is also run.

A network is basically all of the components (hardware and software) involved in connecting computers
across small and large distances.

A process that is describes how the network will connect.

A topology defines how the devices are connected. Further it is divided in physical and logical topology.

Subnet mask is a 4 byte (32 bit) number used to identify the sub network ID and the host ID from an IP
address. All the hosts in a sub network will have the same subnet mask. E.g. 255.255.255.0,
255.255.127.0, 255.255.0.0

1. Restart the server

2. Leave the server ideal for 90 minute

3. Run ==> gpupdate (server 2003 only)

LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, and tell the
system which partition and hard drive to boot from.

Domain local groups assign access permissions to domain groups for local domain resources. Global
groups provide access to resources in entire domains.

FAT and FAT32 provide no security over locally loggedon users. Only native NTFS provides extensive
permission control on both remote and local files.

The presentation layer establishes the data format prior to passing it along to the network application's
interface. TCP/IP networks perform this task at the application layer.