2. Definition of Networking
A network is nothing more
than two or more computers
connected to each other so that
they can exchange information,
such as e-mail messages or
documents, or share resources,
such as disk storage or printers.
In most cases, this connection
is made via electrical cables that
carry the information in the
form of electrical signals. Or by
radio signals (wireless
3. Why use a Network?
Specifically, networks are about sharing three things:
1. Information (Files)
2. Resources (Printers)
3. Applications (Server – Clients)
4. Network Classifications
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Number of devices attached.
5. Network Topology
A topology refers to the manner in which the cable is run to
individual workstations on the network.
Types of topologies:
6. Peer-to-Peer Networks
A peer-to-peer network is a network
where the computers act as both
workstations and servers.
great for small, simple, and
In a strict peer-to-peer networking
setup, every computer is an equal, a
peer in the network.
Each machine can have resources that
are shared with any other machine.
7. Client and Server
The terms "client" and "server" are
used to describe individual computers
that are part of a network where
computing resources and workload are
A server is a computer that makes its
resources available to the network and
responds to the commands of a client.
The server’s shared resources can be
files (a file server); printers (a print
server); processing power (an
application server); etc…
A client is a computer that uses the
resources made available by a server.
10. Computer Networking Models
Models, also called protocol stacks, represented in layers, help to
understand where things go right or wrong.
OSI 7-layer model
OSI 2 Data
(Open Systems Interconnection)
Protocols are sets of rules.
What do you want to do? (Application)
Where are you going? (Addressing)
How do you get there? (Media types)
Did you get there? (Acknowledgments, Error checking)
13. Physical Layer (Layer 1)
Nowadays: Pretty much just Cat 5 (or Cat 5e or Cat6)
twisted pair copper wire and microwave (wireless).
Twists in wire keep down interference
Standard connecter: RJ45.
Fiber (multi-mode or single-mode) coaxial copper (thick- and
thin-net), Cable Modem, plain phone (DSL), microwaves (wireless
14. Physical Layer (Layer 1)
Coax transmits at 10 Mbps..
Shielded Twisted Pair (STP). STP
Unshielded Twisted Pair (UTP). UTP is used in Ethernet networks (Cat5
(100Mbps) or Cat6 (1000Mbps))
Transmission rates vary between 10-100-1000-10000 Mbps.
17. Wireless (Layer 1)
Uses microwave radio waves in the 2.4Ghz (802.11b
and g) and 5.4Ghz (802.11a and n) bands to transmit
These are unregulated frequencies, so other things
(cordless phones, Bluetooth, etc.) can use the same
frequencies, but hopefully one or the other is smart
enough to hop frequencies to stay clear of the other.
802.11b at 11Mbps, both 802.11a/g claim 54Mbps.
18. Data Link Layer (Layer 2)
Addressing by MAC Address
Bridge or Switch
19. Ethernet IEEE 802.3
Ethernet is a popular, relatively inexpensive, easy-to-install LAN architecture
with the following characteristics:
Uses the CSMA/CD media access control.
Data transmission normally occurs at 100Mbps or 1000 Mbps
Typically implemented in a star topology
Ethernet LANs use Twisted Pair cables
An Ethernet LAN is often described in terms of three parameters: transmission
rate, transmission type, and segment distance or cable type.
100 - transmission rate or through put of 100Mbps
base - transmission type is baseband rather than broadband network (i.e., the signal is
placed directly on the cable, one signal at a time)
T – the cable type (e.g. Twisted pair)
Few types of Ethernet: 10Base2, 10Base5, 10BaseT and 10BaseF, 100BaseT,
20. Ethernet Addressing
Since there can be many users on an Ethernet network, everyone has to
have their own unique address.
This is called the Media Access Control (or MAC) address, or sometimes
Ethernet address, physical address, adaptor address, hardware address, etc.
It’s a 12-digit (48 bit) hexadecimal address that is unique to that Ethernet
adaptor and no other in the world.
It can be written as 00:30:65:83:fc:0a or 0030.6583.fc0a or 003065:83fc0a or
The first 6 digits are the Vendor code, (003065 belongs to Apple), the last
6 are the individual interface's own.
How to get MAC address? CMD/IPconfig, Adapter properties
Check your MAC address!
22. Hub vs. Switch
Hubs are shared media devices. Everyone sees everyone’s packets, you’re
only supposed to pay attention to those specifically directed to you, or to
broadcasts. Not too secure, but cheap.
Switches aren’t shared, most of the time. The switch pays attention to the
packets and makes a list of the “sender” Ethernet addresses and makes a
table (it removes old data after a while). When a packet comes along whose
destination address is in the table, the packet only goes to that port.
Unknown packets and broadcasts still go to all ports, but overall, there are
nearly no collisions and is generally more secure.
23. Network Layer (Layer 3)
IP Address & Subnet Mask
Network packets can be routed. This means they can be
passed from one local network to another.
Network Layer Protocols: Internet Protocol (IP)
24. IP Addressing (Layer 3)
The Internet Protocol (IP) is the Network layer protocol used on the
ARP: Address Resolution Protocol. Turns an IP number into an Ethernet
number, very important
You ask “Who’s 172.19.4.15” and if you get a reply, associate the Ethernet
address with the IP address in your ARP table.
IP addresses consists of 32 bits in decimal such as: 184.108.40.206
Each “octet, 8bits” consists of numbers between 0 and 255
Network address, Broadcast address, Subnet Mask and host IP address.
IP Classes: A, B, C, D & E
Privet IP vs. Public IP
26. Port number (Layer 3)
Security and specify exact application
Form: IP : Port
In computer networking, a port number is part of the
addressing information used to identify the senders
and receivers of messages.
HTTPS: 8080 or 443
28. Domain Name Resolution (DNS)
Since most people find it easier to remember names instead of
numbers, IP numbers can and almost always are associated
DNS exists to translate IPs to names
Any web site.
29. Routing. “How do you get there from here?”
You can put an IP (Network layer) packet inside of an
Ethernet (data layer) packet, but a Router got to pass it along
Router makes routing table
If you want to talk to someone outside your local network,
you’ll send that Ethernet packet to your router’s Ethernet
33. DHCP (Dynamic Host Configuration Protocol)
s a network protocol that enables a server to automatically
assign an IP address to a computer from a defined range of
numbers (i.e., a scope) configured for a given network
Relates IP – Names addressing automatically
DHCP assignment can be reserved for a device by reserve the
IP address to the MAC address of that device
A Virtual Private Network (VPN) extends a private network and the
resources contained in the network across public networks like the Internet.
It enables a host computer to send and receive data across shared or public
networks as if it were a private network with all the functionality, security and
management policies of the private network.
This is done by establishing a virtual point-to-point connection through the use
of dedicated connections, encryption, or a combination of the two.
The VPN connection across the Internet is technically a wide area
network (WAN) link between the sites but appears to the user as a private
network link—hence the name “virtual private network”.
Layer 2Tunneling Protocol (L2TP)
IP security (IPSec)
Secure Sockets Layer (SSL) and Transport Layer Security (TLS)
Point-To-Point Tunneling Protocol (PPTP)
Check Default network
Build a LAN
Router GUI (DHCP, NAT, FILTER, ACL, ..)
Check public IP and Rout thru internet
Create a VPN connection
VPN Server & Client
Use different internet access
Check IPs on both
Set as home network/ Firewall options