This document provides an introduction to network devices, addressing schemes, and the basic elements of a network. It discusses: - The basic function of a network is to enable communication between end users such as servers, clients, mobile devices, and PCs. - All networks have four basic elements - hardware devices and medium, and software messages and rules/agreements. It describes examples of each element. - It differentiates between end devices that users directly interact with, and networking devices that help facilitate communication between end devices. Common examples of each type of device are given. - There are three important addressing schemes that help identify locations and applications in a network - IP addresses identify individual devices, port numbers

1. Data Communications
Introduction to Network Devices &
Addressing Schemes

2. Network As
Communication Platform
Elements of a Network

3. Network as aPlatform
• The function of a network is to serve as a platform
for communications between end users.
• End users can be in the form of:
– Servers & clients
– Smart phones & other mobile devices
– PCs and webcam

4. Elements of aNetwork
• All networks have four basic elements in two categories:
– Hardware: (i) Devices, (ii) Medium,
– Software: (iii) Message, (iv) Rules/Agreement.

5. Hardware: Devices &Medium
• Devices
– will be explained in the later slides
• Medium
– this is the channel over which a message travels
– the following diagram shows some examples of a network
medium

6. Software: Message & Rules
• Message:
– Generic term that encompasses web pages,
emails, instant messages, telephone calls, video,
multimedia streaming, etc.
• Rules:
– Addressing schemes (IP, MAC address, port
numbers)
• will be explained in the later slides
– Protocols
• won’t discuss now
• topics towards to end of semester

7. Now & Future: Converged Network
• Previously, broadcast networks (TV & radio), telephone networks,
and computer networks are separate network entities governed
by different technologies, rules and devices.
• The on going trend now is to merge all these three networks into
one single converged network so that PC can communicate with
radio stations, telephones can talk to laptops.

8. Introduction to Network Devices
Fundamental visualization of networks:
End-Devices & Networking Devices

9. End-Devices & Networking Devices
• There are two big classification of devices in the
Internet/network:
– End-Devices & Networking Devices.
• End devices:
– Devices that a person can use for communication
purposes.
– End-devices normally attached to a network.
• Networking devices:
– Equipment that form the network and help to mediate
and transfer data between end-devices.

10. Example of the Devices
• End-devices:
• Networking devices:

11. Relationship between
End-Devices & Networking Devices
• A person use end-devices to communicate with another
person with another end-devices via the network formed by
networking-devices.
– A person DOES NOT use networking-devices to communicatewith
another end-devices or networking devices.
– Servers and clients are end-devices.

12. Forming your 1st Functional Network
• Perhaps one of the simplest form of a functional network is
to attach a PC and a server to a switch.
– The simplest form of network is a point-to-point network
• “Functional” means that a client can access some form of
network services via a network.
• In the following example, Home PC is accessing a web
page in the Home Server via a network switch.
Point-to-point
network

13. Point of Note for this Subject
• Network is a “complicated” subject, since you need to know ten over things first
before you make a “functional” network.
– Network is a system
• For example, for the following network, you need to know:
– How to connect and configure the routers.
– How to set up and configure servers
– How to connect & configure your PC to a switch and use an appropriate client
software.
– How to link up and configure the modem and wireless ADSL router.
• Which means, you need to know various things first in order to make one viable
service and a functional network that transfer your data.
– Be patient and work hard.

14. Quick Quiz
• Which of the following are end devices (or
networking devices)?
– Workstations
– Application Server
– Wireless access point
– I-phone
– ADSL router

15. New Networking Devices
F5 Networks BIG-IP LoadBalancer
Web server load balancer
Packeteer PacketShaper
Traffic monitor and shaper
Network Appliance NetCache
Localized content delivery platform
Ingrian i225
SSL offload appliance Nortel Alteon Switched Firewall
CheckPoint firewall and L7 switch
Cisco IDS 4250-XL
Intrusion detection system
Cisco SN 5420
IP-SAN storage gateway
Extreme Networks SummitPx1
L2-L7 application switch
NetScreen 500
Firewall and VPN

16. Comments on Previous slide
• As the network getting more complex due to
convergence, new networking devices have
emerged in the market to cater for:
– Security
– Storage
– Traffic management
– Quality of service
– Efficiency and speed.
• These new networking devices will be explained
in the future slides.

17. Reminder: Focus of this Class
• A big part of this class is to know:
– How to connect the networking-devices correctly in order to forma
functional network.
– How to configure the individual network-devices to work as a
functional member of network (e.g. router)
– How to attach an end-device to a network
– How to configure certain end-devices.
– How to configure servers that provide different type of services.
– How to use certain end-devices to explore the network and access
the network services.
– How to use the devices correctly by knowing the features of these
devices.
• You can experience all these in the lab through a
educational simulation tool called Packet Tracer.
– Of course you have to learn some theory and guiding principles from
the lectures.

18. Rules of Network: Introduction to
Addressing Scheme
Port Number – Network services
IP address – Targeted host
Physical Address – Hardware Address

19. “Some” Questions
• When you use your client software, how do you
know where (or which web site) you access?
• How does network (or Internet) knows where it
should send your data to?
• How does the network know which server or
services that it should locate?

20. “Some” Answers
• We need some addressing scheme to find our way
in the network.
• We need some addressing scheme to identify the
PCs, servers, and services in the Internet…
• There are 3 sets of addresses that help you to find
your way in the network…

21. The “Addresses” in Network
• “Address” emphasizes the location of certain elements (both
software and hardware) in the network.
– meaning, where to find certain “things” in the network
• These are the three sets of addresses that are very
important to the network and end-devices
– Network “location” address => IPAddress
– Network “application” address => Port Number
– Network “hardware” address => Physical Address (MAC address)
• These addresses are operating-system or platform
independent.
– They are used in Windows 10, Linux, Solaris, Unix, and Apple
computers

22. Locating the PCs in theNetwork
• Question: how does the network identifying
and differentiate the left PC from other PCs?

23. Locating the PCs in theNetwork
• Answer: By giving each PC an unique and
yet standardized number called IP address.

24. The standard format of IP address- 1
• There are two types of IP address
– IPv4 (32 bits) and IPv6 (128 bits)
• We will only focus on IPv4 in this class
– Whenever we talk about IP address, it is IPv4 (IP version 4)
• IP address has a standardized format that is recognized
throughout the world.

25. The standard format of IP address- 2
• The size of an IP address = 4 bytes = 32 bits
• It is written in a “dotted-decimal notation”.
– 4 numbers with 3 dots.
• Each of these 4 numbers is 1 byte
– The value range is 0 to 255 only
• Valid IP address: 199.200.45.78
• Invalid IP address: 800.354.7.432

26. Quick Quiz
• Which of the following are valid IP addresses?
– 0.0.0.0
– 100.2.300.3
– 255.255.255.1
– 1.12.0.256
– 7.7.7.69
– 192.0.1.1.1
– 200.245.80
– 6.260.80.6
– 1.2.3.4

27. Unique IP address
• Within a network, the IP address has to be unique
– There is ONLY ONE such IP address in the value.
• You CAN’T have duplicate IP addresses in the network
– The end devices with same IP addresses can’t communicate with
other end devices.
CAN’T have 2 same
IP addresses within
a network

28. Internet IP Address
• The global Internet address is “addressed” with
IP address, also known as Public IP address.
• The concept of IP address is similar to your
phone number (both handphone and land line)
• Internet IP address is unique in the whole world.
• Internet IP address can be traced to its geo-
location.
• Managed and created by the Internet Assigned
Numbers Authority (IANA).

29. Source IP and Destination IP
• There are two sides of the IP address
– Source IP (you)
– Destination IP (where you want to go)
Source IP
• Your PC MUST have a source IP
before you can communicate with the
Internet.
Destination IP

30. IP Address in EndDevices
• The following are some of the end devices
that require IP address in order to
communicate via the network.
– Almost all of the end devices require IP address.

31. IP Address in Networking Device
• Not all networking devices require IP address
– Switches, hubs, modems,repeaters.
• Routers (including wireless router) requires IP
address in order to function in the network.
Require IP address DOES NOT require
IP address

32. Identifying Network Application
• If the server send data back to PC1 (using IP
address), and PC1 is running a few network
applications, does PC1 know which network
application it should direct this data to?
• How can PC1 tell that the data is directed to
the Web browser, or Tera Term?
PC1 is running these network applications

33. Network Application Address
• We can identify and locate the end-devices in the
network with IP address.
• Question: How do we identify the network
applications within these end-devices?
• Question: How do we identify the network services
within the servers?
• Answer: Through an network applications/service
addressing scheme called Port Numbers.

34. What is a PortNumber?
• A port number is a way to identify a specific process to which
an Internet or other network message is to be forwarded
when it arrives at an end-device.
– Treat process = program = application
• Port number is unique within an end-device.
• The size of a port number is 2 bytes.
– Range => 0 to 65535
• Typically (and at this level of your study), the port numbers
are categorized into:
– Server port numbers: 0 to 1023
– Client port numbers: 1024 to 65535

35. Server Port Numbers -1
• Server port numbers are the standardized 2-byte numbers
that identify the well-known network services such as HTTP,
FTP, DNS, etc..
• IANA (Internet Assigned Numbers Authority) is responsible
for assigning these server port numbers (they are
standardized for network services)
– http://www.iana.org/assignments/port-numbers
– http://en.wikipedia.org/wiki/Port_number
• These server port numbers have been assigned with a
dedicated fixed value to describe a network service, e.g:
– Port number = 80 (HTTP)
– Port number = 53 (DNS)
– Port number = 23 (telnet)

36. Server Port Number -2
• Again, network services are identified via port numbers inside
the servers
• In the range of 0-1023, a particular value have already been
assigned and associated with a particular network services.
• Server ports are also called listening ports.
• Well known port numbers.
– 20 (FTP data), 21 (FTP control), 22 (ssh), 23 (telnet)
– 25 (smtp, email), 53 (DNS),
– 67 (BOOTP, DHCP server), 68 (BOOTP, DHCP client)
– 69 (tftp), 80 (HTTP, web),
– 109 (POP2, email), 110 (POP3, email)
• Port number = 80 is ALWAYS a web (HTTP) service.
– You may need to memorize some of these port numbers

37. A Snapshot of Server Port Number - 1

38. A Snapshot of Server Port Number - 2

39. Client Port numbers
• Client port numbers are not fixed.
• The value of client port number is not standardized
by IANA.
– It is normally larger than 1023
• Assigned by operating system randomly.
• Client ports are sometimes called connection ports
• The notation [IP:port_number] is called a socket.
• Socket can identify any network application/service
in the Internet.
– For example: 157.166.255.18:80 identify the web service
of www.cnn.com

40. IP Address & Port Number
• In previous slides, PC1 can find cnn.com because PC1
knows the IP address of cnn.com.
• When the data reach cnn.com, cnn.com will direct this data
to a particular network service based on the port number.
• In this case, port 80 will refer to the web service provided
by cnn.com.
• So, port number is used to identify:
– Network Application in clients
• When the data go to a client, which network application should it go?
– Network Service in servers
• When the data go to a server, which network service should it go?
• Same as IP address, port number is also divided into:
– Source port number
– Destination port number

41. Example of [IP:port]
• 3 PCs are accessing the web server at the same time.
• At the server, it was detected that there are 3 connections
– 192.168.1.1:80, (IP: port number). Again, this notation is called a socket.
– Meaning the server IP is 192.168.1.1 and the port number is 80 (source port
number)
– Same service (web server application) is connected to three other applications
(web browser),.
– For example, 192.168.1.2 is having a application with a port number of 1029.

42. Quick Quiz
• In this web server
– What is the source IP address?
– What is the destination IP address?
– What is the source port number?
– What is the destination port number?

43. Example of [IP:port]
• Please notice that the servers’ web service will always
have a port number of 80
• The clients port numbers are rather random.

44. Hardware Address: MAC Address
• Media Access Control address (MAC address) is a unique
identifier attached to most network adapters or network
interface card (NICs).
– Used in both wired and wireless NICs
– Unique throughout the world
• No two NIC will have the same MAC address
• Burned in the NIC chips and can’t be changed
– Contain 6 bytes (or 6 octet or 48 bits)
XEROX CORPORATION
MATRIX CORPORATION
CISCO SYSTEMS, INC.
• First 3 bytes identify the manufacturer (OUI)
• 00-00-00
• 00-00-0B
• 00-00-0C
• http://standards.ieee.org/regauth/oui/oui.txt
– Also known as Hardware Address or Physical Address
• Usually shown in hexadecimal format, with each octet
separated by a dash or colon.
– An example of a MAC address would be "00-08-74-4C-7F-1D".

45. Last Point of Network Address Schemes
• Before the data is being sent to the network
wire, typically the PC/host will have to
“gather” 3 pair of “addresses”
– Source port & Destination port
– Source IP & Destination IP
– Source MAC & Destination MAC
• We will elaborate this future lectures

46. Quiz
Helpful memory aid

47. Quiz (True/False)
1. Client port number is assigned by IANA
2. MAC address is 36 bits.
3. MAC address is maintained by IANA.
4. Port number = 266 is a server port number.
5. Each socket is unique in the Internet.
6. You can run a network service with a port number of 5091.
7. You only need the IP address to locate the program of a
remote host.
8. Windows 10 can use port number 1024 for three
client programs within a PC at the same time.
9. You can use more than 1 of the same destination port
number from a PC.

48. Quiz (MCQ)
1. Public IP address is related to?
B) Application
D) Cable
F) Server
– A) User
– C) Geo-Location
– E) Network
– G) Password
2. Port number is related to?
B) Application
D) Cable
F) Server
– A) User
– C) Geo-Location
– E) Network
– G) Password