1. UCCN 1003 (May 2010)
Data Communications & Networks
(Lecture 01b)
Introduction to Network Devices &
Addressing Schemes

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

3. 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:
– Equipments that form the network and help to mediate
and transfer data between end-devices.

4. Example of the Devices
• End-devices:
• Networking devices (with cables too):

5. 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 communicate with
another end-devices or networking devices.
– Servers and clients are end-devices.

6. 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

7. 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.

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

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

10. Reminder: Focus of this Class
• A big part of this class is to know:
– How to connect the networking-devices correctly in order to form a
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.

11. Introduction to
Addressing Scheme in Networks
Port Number – Network services
IP address – Targeted host
Physical Address – Hardware Address

12. “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?

13. “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…

14. 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 => IP Address
– 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 XP, Linux, Solaris, Unix, and Apple
computers

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

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

17. 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.

18. 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

19. 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

20. Answer
• Which of the following are valid IP addresses?
– 0.0.0.0 (valid)
– 100.2.300.3 (invalid => value 300 exceed 255)
– 255.255.255.1 (valid)
– 1.12.0.256 (invalid => value 256 exceed 255)
– 7.7.7.69 (valid)
– 192.0.1.1.1 (invalid => 5 numbers with 4 dots)
– 200.245.80 (invalid => 3 numbers with 2 dots)
– 6.260.80.6 (invalid => value 260 exceed 255)
– 1.2.3.4 (valid)

21. 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

22. 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).

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

24. IP Address in End Devices
• 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.

25. 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

26. 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

27. 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.

28. What is a Port Number?
• 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

29. 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)

30. 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

31. A Snapshot of Server Port Number - 1

32. A Snapshot of Server Port Number - 2

33. 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

34. Some Notes on Port Numbers
• In fact, every port number (0-65535) can be assigned as a network service.
– Just that it is not recognized globally (e.g. IANA)
• For example, UTAR can run a game server hosting a Wuxia World game service with a port
number of 500.
– However, port number 80 is a globally recognized HTTP service that you can’t simply
use it.
• Same applies to any port number below 1024.
• It is widely recognized that a client program can’t use port number range of 0 -
1023.
• Again, non-standardized network service can use port number range of 1024 –
65535 (which we have identify as client port numbers)
• Port number is unique within an end device at any given time. However, it can re-
used again. For example:
– OS won’t assign port number 1030 for Firefox, and Chrome at the same time.
– OS may use 1030 for Firefox and then for Chrome (after Firefox no longer using port
number 1030).

35. IP Address & Port Number
• In previous slides, cnn.com can find PC1 because cnn.com
knows the IP address of PC1.
• When the data reach PC1, PC1 will direct this data to a
particular network applications based on the port number
(contained in the network data itself).
• 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

36. 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.

37. 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?

38. Answer
– What is the source IP address?
• 192.168.1.1
– What is the destination IP address?
• 192.168.1.2; 192.168.1.3; 192.168.1.4
– What is the source port number?
• 80
– What is the destination port number?
• 1026, 1029
• Note: there are two destination port number of 1026 but they belong to
a different PC.

39. 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.

40. 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)
• First 3 bytes identify the manufacturer (OUI)
• 00-00-00 XEROX CORPORATION
• 00-00-0B MATRIX CORPORATION
• 00-00-0C CISCO SYSTEMS, INC.
• 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".

41. 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

42. Quiz
Helpful memory aid

43. 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. Window XP 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 in a PC.

44. Quiz (True/False)
1. Client port number is assigned by IANA
• (false, by OS)
2. MAC address is 36 bits.
• (false, 48 bits or 6 bytes)
3. MAC address is maintained by IANA.
• (false, by IEEE and manufacturers)
4. Port number = 266 is a server port number. (true)
5. Each socket is unique in the Internet. (true)
6. You can run a network service with a port number of 5091. (true)
7. You only need the IP address to locate the process of a remote host.
• (false, you need both the IP and port number)
8. Window XP can use port number 1024 for three client programs within
a PC at the same time.
• (false, port number is unique at any given time)
9. You can use more than 1 of the same destination port number in a
PC. (true)

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

46. Answer (MCQ)
1. Answer: C, E, F
2. Answer: B, F