Networking

TYPES OF NETWORKS
LAN – LOCAL AREA NETWORK IS A SMALL
GEOGRAPHICAL AREA typically within the premises of
A building
MAN – METROPOLITAN AREA NETWORK IS A
NETWORK OVER A LARGER GEOGRAPHICAL AREA
SUCH AS a city.
WAN – WIDE AREA NETWORK IS A NETWORK USED
OVER AN EXTREMELY LARGE GEOGRAPHICAL AREA
SUCH AS the country or beyond the nation.
Basics of Networking

NETWORKS ARE BROKEN INTO 3 TOPOLOGIES.
THEY ARE:
BUS TOPOLOGY
STAR TOPOLOGY
RING TOPOLOGY

BUS TOPOLOGY ALLOWS INFORMATION TO BE
DIRECTED FROM ONE COMPUTER TO THE OTHER.
LOTS OF BINARY COLLISION THOUGH.

Lesson 3—
Networking
BASICS 4
Bus Topology
It is a multipoint topology.
Each device shares the connection.
The bus has one starting and one
ending point.
Packets stop at each device on the
network.
Only one device at a time can
send.

STAR TOPOLOGY IS THE MOST COMMON TYPE
USED. ALL COMPUTERS ARE ATTACHED TO A HUB.
LESS COLLISIONS AND MOST EFFICIENT.

Lesson 3—
Networking
BASICS 6
Star Topology
• All devices are connected to a
central device (hub).
• The hub receives and forwards
packets.
• It is the easiest topology to
troubleshoot and manage.
• It has a single point of failure.

Lesson 3—
Networking
BASICS 7
Star Topology

RING TOPOLOGY- USES A TOKEN TO PASS
INFORMATION FROM 1 COMPUTER TO THE OTHER.
A TOKEN IS ATTACHED TO THE MESSAGE BY THE
SENDER TO IDENTIFY WHICH COMPUTER SHOULD
RECEIVE THE MESSAGE. AS THE MESSAGE MOVES
AROUND THE RING, EACH COMPUTER EXAMINES
THE TOKEN. IF THE COMPUTER IDENTIFIES THE TOKEN
AS ITS OWN, THEN IT WILL PROCESS THE
INFORMATION.

Lesson 3—
Networking
BASICS 9
Ring Topology
• It is a circle with no ends.
• Packets are sent from one
device to the next.
• It does not slow down as
more devices are added.

A DISADVANTAGE OF A TOKEN RING IS IF ONE
COMPUTER IS BROKEN OR DOWN, THE MESSAGE
CANNOT BE PASSED TO THE OTHER COMPUTERS.

11
General Architecture of
Computer Networks

12
Connection of Networks
networks or subnetworks
router or
gateway
node
(host,
station)

Lesson 3—
Networking
BASICS 13
Hybrid Topologies
• They are variations of two or more
topologies.
• Star bus – used to connect multiple
hubs in a star topology with a bus.
• Star ring – wired like star, but
functions like a ring.

Lesson 3—
Networking
BASICS 14
Common basic networking devices:
Router: a specialized network device that determines the next
network point to which it can forward a data packet towards the
destination of the packet. Unlike a gateway, it cannot interface
different protocols. Works on OSI layer 3.
Switch: a device that allocates traffic from one network segment to
certain lines (intended destination(s)) which connect the segment
to another network segment. So unlike a hub a switch splits the
network traffic and sends it to different destinations rather than to
all systems on the network. Works on OSI layer 2.

Lesson 3—
Networking
BASICS 15
Proxy: computer : network service which allows clients to make
indirect network connections to other network services
Firewall: a piece of hardware or software put on the network to
prevent some communications forbidden by the network policy
Network Address Translator: network service provide as hardware
or software that converts internal to external network addresses
and vice versa
# Network Card: a piece of computer hardware to allow the attached
computer to communicate by network
# Modem: device that modulates an analog "carrier" signal (such as
sound), to encode digital information, and that also demodulates such a
carrier signal to decode the transmitted information, as a computer
communicating with another computer over the telephone network

Lesson 3—
Networking
BASICS 16
Routers within the network recognize that the request is not for a
resource inside the network, so they send the request to the
firewall. The firewall sees the request from the computer with the
internal IP. It then makes the same request to the Internet using its
own public address, and returns the response from the Internet
resource to the computer inside the private network. From the
perspective of the resource on the Internet, it is sending
information to the address of the firewall. From the perspective of
the workstation, it appears that communication is directly with the
site on the Internet. When NAT is used in this way, all users inside
the private network access the Internet have the same public IP
address when they use the Internet. That means only one public
addresses is needed for hundreds or even thousands of users.

The seven layers of the OSI Model are:
Layer 1 PHYSICAL
Layer 2 DATA-LINK
Layer 3 NETWORK
Layer 4 TRANSPORT
Layer 5 SESSION
Layer 6 PRESENTATION

THE PHYSICAL LAYER
The physical layer is concerned with transmitting
raw bits over a communication channel though
hubs, wires (cat5UTP), modems, network cards…
basically anything that is physical to the network.
When looking at network cables, there are
2 types that affect nodes. They are:
In networking, computers are also known as
Hosts or Nodes.

•Straight though cables or also known as patch cables
•Cross-over cables
The difference in the cables are the way the wires
are connected within the RJ45. I have attached a
sheet for you in your package.

Lesson 3—
Networking
BASICS 20
Hub: connects multiple Ethernet segments together making them
act as a single segment. When using a hub, every attached all
the objects, compared to switches, which provide a dedicated
connection between individual nodes. Works on OSI layer 1.
Repeater: device to amplify or regenerate digital signals received
while sending them from one part of a network into another.
Works on OSI layer 1.

TWISTED SHIELDED PAIR – USED IN PHONE LINES, NETWORKS
UNSHIELDED TWISTED PAIR “ “ “ “
COAXIAL CABLE – USED IN CABLEVISION GREAT FOR VIDEO
FIBRE OPTIC CABLES - USES LIGHT TO CARRY SIGNAL BUT
HARD TO WORK WITH AND LOOSES SIGNAL OVER LONGER
DISTANCES
COMMUNICATION CHANNELS

THE DATA-LINK LAYER
The data link layer takes raw transmission and
transform it into a line that appears free of
transmission errors in the network layer.
The Data-Link Layer also is where you would find
the MAC Address. (Media Access Control). To find the
MAC Address of your computer, or any computer:
Start/Programs/MS Prompt and type: ipconfig/all
"C:WINDOWS>" prompt, type "tracert
www.howstuffworks.com"

THE DATA-LINK LAYER
You will also find smart devices such as switches in
the Data-Link Layer.
The digital information that needs to be sent such as
and e-mail, attachments, etc needs to be broken into
smaller bits known as packets.
These packets require some information similar to
sending a letter in the mail.

THE NETWORK LAYER
The network layer is concerned with controlling
the operation of the subnet. A ROUTER is used to
determining how packets are routed from source
to destination.
If one path is busy, then the router will select another
path for the packets to travel. So really, the packets
can all have different paths and find their way to the
final destination.

THE NETWORK LAYER
The router has millions of IP addressing built into
the software, and knows where to send the packets.
IP stands for Internet Protocol and is basically an
address that the packets will be sent to.
An example would be 216.27.61.137

THE NETWORK LAYER
If you look at the IPAddress, the number are broken
into different categories.
216. 27.61.137
Classification Hosts
216. 27.61.137
Octets

Classifications can be broken into 3 classes. They are:
Class A - Only the first octet is used for addressing and
the balance used for hosts.
Class B - The first two octet are used for addressing
and the balance used for hosts.
Class C - The first three octet are used for addressing
and the balance used for hosts.

Every machine on the Internet has a unique
identifying number, called an IP Address.
A typical IP address looks like this:
216.27.61.137
But computers communicate in binary form.

The same IP address in binary:
11011000.00011011.00111101.10001001
216.27.61.137

If you add all the positions together, you get 32,
which is why IP addresses are considered
32-bit numbers
Combine the four octets and you get 232 or a possible
4,294,967,296 unique values.
11011000.00011011.00111101.10001001

Class A - This class is for very large networks,
such as a major international company might have.
IP addresses with a first octet from 1 to 126 are
part of this class.

Class B - This class is used for medium-sized networks.
A good example is a large college campus.
IP addresses with a first octet from 128 to 191
are part of this class. Class B addresses also include
the second octet as part of the Net identifier.

Class C - Class C addresses are commonly used for
small to mid-size businesses. IP addresses
with a first octet from 192 to 223 are part of this
class. Class C addresses also include the second
and third octets as part of the Net identifier.

Loopback - The IP address 127.0.0.1 is used
as the loopback address. This means that it is
used by the host computer to send a message
back to itself.
LOOPBACK

MAC addresses are 48 bits in length and are expressed as 12
hexadecimal digits. The first 6 hexadecimal digits, which are
administered by the IEEE, identify the manufacturer or vendor
and thus comprise the Organizationally Unique Identifier (OUI).
The last 6 hexadecimal digits comprise the interface serial
number, or another value administered by the specific vendor.
MAC addresses sometimes are called burned-in addresses
(BIAs) because they are burned into read-only memory (ROM)
and are copied into random-access memory (RAM) when the
interface card initializes.

THE TRANSPORT LAYER
The transport layer “DIRECTS PACKETS”, splits it up into
smaller units if need be, pass these to the network
and ensure that the pieces are travelling in an
orderly fashion.
A series of protocols are also established in this
layer to ensure proper flow of the packets.
You can basically describe the Transport Layer as
a “TRAFFIC COP”.

THE SESSION LAYER
The session layer allows different machines to
establish sessions between themselves.
Once communications are established, encryption
then begins both parties.

THE PRESENTATION LAYER
The Presentation Layer’s job is managing data
structures and converting from the representation
used inside the computer to the network standard
representation an visa versa.
In English terms, the Presentation layer basically
takes the packets and re-assembles them so you can
open the e-mail or the attachment.
If any packets got lost along the way, or were
damaged, then the Presentation layer will send a
sign to the sender that it requires the specific packet.

THE APPLICATION LAYER
The Application layer contains a variety of protocols
that are commonly required.
Another Application layer function is file transfer.
Different file systems have different file naming
conventions, different ways of representing text lines,
and so on.
Transferring a file between two different systems
requires handling and other incompatibilities.

FTP - File Transfer Protocol
HTTP Protocol
Electronic Mail Protocols

SOAP - Sim ple Object Access
Prot ocol
DHCP
The Dynam ic Host Configuration Protocol

IPv6 - Int ernet Prot ocol version
IPv6 prom ises to relieve the current IP a
PPPoE
The Point to Point Protocol over Ethernet
(PPPoE) standard helps access providers

The Internet is a global system of interconnecting computer
networks that use the standard Internet Protocol Suite (TCP/IP)
to serve billions of users worldwide. It is a network of networks
that consists of millions of private, public, academic, business,
and government networks, of local to global scope, that are
linked by a broad array of electronic, wireless and optical
networking technologies. The Internet carries a vast range of
information resources and services, and multimedia content such
as the inter-linked hypertext documents of the World Wide Web
(WWW) and the infrastructure to support electronic mail.
Most traditional communications media including telephone,
music, film, and television are reshaped or redefined by the
Internet, giving birth to new services such as Voice over Internet
Protocol (VoIP) and IPTV.

DOMAIN NAME :
Domain names are hostnames that identify
Internet Protocol (IP) resources such as web
sites. Domain names are formed by the rules
and procedures of the Domain Name System
(DNS).
Domain names are used in various networking
contexts and application-specific naming and
addressing purposes. They are organized in
subordinate levels (subdomains) of the DNS
root domain, which is nameless.

The domain name space consists of a tree of domain names.
Each node in the tree holds information associated with the
domain name. The tree sub-divides into zones beginning at the
root zone.
A domain name consists of one or more parts, technically called
labels, that are conventionally concatenated, and delimited by
dots, such as example.com.
The right-most label conveys the top-level domain; for example,
the domain name www.example.com belongs to the top-level
domain com.
Domain name space

The hierarchy of domains descends from the right to the left
label in the name; each label to the left specifies a subdivision,
or subdomain of the domain to the right. For example: the label
example specifies a node example.com as a subdomain of the
com domain, and www is a label to create www.example.com, a
subdomain of example.com. This tree of labels may consist of
127 levels. Each label may contain 1 up to and including 63
octets
A hostname is a domain name that has at least one associated
IP address. For example, the domain names www.example.com
and example.com are also hostnames, whereas the com
domain is not. However, other top-level domains, particularly
country code top-level domains, may indeed have an IP
address, and if so, they are also hostnames.

In this example, the client is performing a name resolution for
“C.B.A.” using strictly iterative resolution. It is thus responsible
for forming all DNS requests and processing all replies. It starts
by sending a request to the root name server for this mythical
hierarchy. That server doesn’t have the address of “C.B.A.”, so it
instead
returns the address of the name server for “A.”. The client then
sends its query to that name server, which
points the client to the server for “B.A.”. That name server refers
the client to the name server that actually has the address for
“C.B.A.”, which returns it to the client. Contrast to Figure 244.

This is the same theoretical DNS resolution that I showed in
Figure 243, but this time, the client asks for the name servers to
perform recursive resolution and they agree to do so. As in the
iterative case, the client sends. Its initial request to the root name
server. That server doesn’t have the address of “C.B.A.”, but
instead of merely returning to the client the address of the name
server for “A.”, it sends a request to that server itself. That
name server sends a request to the server for “B.A.”, which in
turn sends a request to the server for “C.B.A.”. The address of
“C.B.A.” is then carried back up the chain of requests, from the
server of “C.B.A.” to that of “B.A.”, then “A.”, then the root, and
then finally, back to the client.

Networking

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