Chapter 6
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Network infrastructure involves the network’s physical
configuration, logical operation, structure, procedures, data
format, protocols and other components.
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The most common forms of network architectures are Local
Area Network (LAN) and Wide Area Network (WAN)
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LAN’s are typically smaller in terms of size and geographic
coverage and consist of two or more connected devices.
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WAN’s tend to larger, covering more geographic area and
consist of two or more systems in geographically separated
areas connected by any of a variety of methods such as
leased lines, radio waves, satellite relay, microwaves or even
dial-up connection.
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Campus Area Network (CAN): a network connecting any
number of buildings in an office or university complex.
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Metropolitan Area Network (MAN): a network designed for a
specific geographic locality such as a town or a city.
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Storage Area Network (SAN): a high speed network
connecting a variety of storage devices such as a tape,
RAID, optical drives, file servers and others.
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Virtual Local Area Network (VLAN): a logical network allowing
systems on different physical network to interact as if they
were connected to the same physical network.
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Client-Sever: A network where powerful, dedicated systems
called servers provide resources to individuals workstations
or clients.
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Peer-to-Peer: a network where every system is treated as an
equal, such as a home network.
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Internet: a “global network” connecting thousands of millions
of systems and users.
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Intranet: a “private’ network only accessible to authorized
users. Many large corporations host an intranet to facilitate
information sharing within their organization.
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Extranet: a “private” network established by connecting two
or more intranets. This network is accessible only to the
authorized users from the participating intranet’s.
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Network Topology: refers to the way the network is physically
and logically arranged.
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Star Topology: all the network components are connected to
a central point.
Bus Topology: all the network components are connected to
same cable, called the “bus” or the “backbone”.
Ring Topology: all the network components are connected to
each other in a closed loop with each device directly
connected to two other devices.
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Client PC
Active
Node
Client PC
Client Scanner
Client
Client Laptop
Client Printer
Hub
Client
Server
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Client
Client
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Client
Client
Client
Server
Client
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Client
Client
Client
Server
Client
Client
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Client
Client
Client
Client
Server
Client
Client
Client
Client
Server
Client
Client
BUS
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A protocol is an agreed upon format for exchanging or
transmitting data between systems.
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A protocol defines a number of agreed upon parameters,
such as data compression methods, the type of error
checking to use, and mechanism for systems to signal when
they have finished either receiving or transmitting data.
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Ethernet: the most widely used LAN protocol.
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TCP/IP: the collection of communications protocols used to
connect hosts to the internet. TCP/IP is the most widely used
network protocol and is a combination of the TCP and IP.
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Internet Protocol: the protocol for managing and transmitting
data between packet-switched networks.
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AppleTalk: the communication protocol developed by Apple to
connect Macintosh computers and printers.
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The main purpose of communication networks is to facilitate
the sharing of information.
Every network has some limitations on the amount of data
that can be transmitted.
Larger chucks of data is broken down into smaller, more
manageable sized chunks called packets.
Breaking down a large chunk of data into smaller size chunks
has advantages, the network bandwidth is better utilized. In
case of any transmission error, we do not have to retransmit
one large large chuck data.
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Protocol version number: what kind of packet it is.
Packet header length: how large the header of the packet is.
TOC: how to process the packet, i.e., minimize delay,
maximize throughput, maximize reliability, and minimize cost.
Identification: an unique identifier so this packet can be
distinguished from other packets.
Total length: how large the entire packet is.
Flag: Whether or not this packet is part of a longer data
stream and should be handled relative to other packets.
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Fragment offset: a description of where this packet fits into
data stream as compared to other packets.
Checksum: checksum code to minimize the potential for data
corruption during transmission.
Source IP: where the packet is from.
Destination IP: where the packet is going.
Data Payload: the data this packet carries.
Options: governs security and handling restrictions, whether
or not to record the route this packet has taken.
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4-bit version
4-bit header length
8-bit type of service (TOS)
16 –bit identification
8-bit time to live (TTL)
16-bit total length (in
bytes)
3-bit
flag
8-bit protocol
13-bit fragment
16-bit header checksum
32-bit source IP address
32 –bit destination bit IP address
Optional (If used)
Data Payload
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UDP is a “connectionless” protocol.
No connection is established between the sender and the
receiver.
There is no way for the sender to know if the packet was
successfully transmitted to the receiver, and in the order sent.
Since no connection is established, UDP is considered to be
an unreliable protocol.
UDP is used when the loss of data is tolerated.
Advantage of UDP: most of the bandwidth is used for the
transfer of data, there is no overhead.
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TCP is a “connection-oriented” protocol.
Sender and the receiver establishes a connection via “three
was handshake” before transmitting the data.
TCP is a reliable protocol, the packets are processed in the
order sent. Each packet has a sequence number.
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The ultimate purpose of any communication network is to
deliver packets across the networks.
Packets can be delivered locally, if the destination address
belongs to a local network. Packets can be delivered
remotely, if the destination address is belongs to a different
network. Alternatively, the packets can be delivered remotely,
then locally.
There are two types of packet delivery mechanisms.
◦ Local Packet Delivery
◦ Remote Packet Delivery
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If the source and the destination are on the same LAN, or a
local network, local packet delivery is used.
Delivery is accomplished by using the MAC address.
Media Access Control (MAC) address is a system’s hardware
address. Every system has a unique MAC address.
A MAC address is expressed as six pairs of hexadecimal
digits such as 00:07:e9:7c:c8:aa.
Storing the MAC address of each system on the local LAN is
impossible and time consuming.
To find the destination MAC address, the sending system
must use Address Resolution Protocol (ARP).
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The sending system knows the destination IP address,
however, it does not know the destination MAC address.
To know the destination MAC address, the sending system
send a broadcast query to all the systems on the LAN asking
“who is 10.1.1.140?”
Only the system with the 10.1.1.140 IP address will respond
to the broadcast query by sending the MAC address.
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Remote packet delivery is accomplished via IP address.
For humans, IP address are very difficult to remember.
Domain Name System (DNS) protocol was developed to
translate a name into IP address.
Routers are used to interconnect different networks. The
sending system send the packet to the router, the router will
check its routing table to see where to resent the packet. This
process is called routing.
This process is repeated until the packet reaches the
destination router. The destination router fill finally determine
the MAC address, and forward the packet to the destination.
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IPv4 IP address has a network part and a host part.
The network part is called the subnet.
The process of dividing the 32 bit space into networks is
called subnetting.
Subnet mask is used to tell exactly how much of the space is
network portion and how much is the host portion.
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IP address 10.10.10.101
Subnet mask: 255.255.255.0
Convert the decimal format to binary format.
◦ Subnet mask: 11111111.11111111.11111111.00000000
◦ IP address: 00001010. 00001010. 00001010. 01100101
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Perform a bitwise AND operation to get the subnet address.
◦ Subnet Address: 00001010. 00001010. 00001010. 00000000
◦ Subnet Address in decimal format: 10.10.10.0
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Class A address:
◦ Supports 16 million host address on each of 27 network.
◦ Subnets: 10.10.10.0 to 126.255.255.255.
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Class B address:
◦ Supports 65,000 hosts on each of 16,000 networks.
◦ Subnets: 128.0.0.0 to 192.255.255.255.
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Class C address:
◦ Supports 254 hosts on each of 2,000,000 networks.
◦ Subnets: 192.0.0.0 to 223.255.255.255.
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NAT translate the private (non-routable) IP address into
public (routable) IP address.
Most organization use private IP address for internal usage,
and use a NAT device to translate many internal IP address
into small number of public IP address.
Private IP Address Range
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
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Outbound
Source: 10.10.10.121
Destination: 207.25.71.23
Source: 63.69.110.110
Destination: 207.25.71.23
Firewall Performing NAT
Internal Network
Source : 207.25.71.23
Destination: 10.10.10.121
Inbound
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www.hotmail.com
207.25.71.23
Source : 207.25.71.23
Destination: 63.69.110.110
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