Data Communications & Networks

Introduction to Network Devices &

Addressing Schemes

UCCN 1003 (May 2010)

(Lecture 01b)

Introduction to Network Devices

Fundamental visualization of networks:

End-Devices & Networking Devices

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.

Example of the Devices

• End-devices:

• Networking devices (with cables too):

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.

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-pointnetwork

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.

Quick Quiz

• Which of the following are end devices (or networking devices)?

– Workstations

– Application Server

– Wireless access point

– I-phone

– ADSL router

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)

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.

Introduction toAddressing Scheme in Networks

Port Number – Network services

IP address – Targeted host

Physical Address – Hardware Address

“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?

“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…

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

Locating the PCs in the Network

• Question: how does the network identifying and differentiate the left PC from other PCs?

Locating the PCs in the Network

• Answer: By giving each PC an unique and yet standardized number called IP address.

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.

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

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

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)

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 sameIP addresses within a network

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).

Source IP and Destination IP

• There are two sides of the IP address

– Source IP (you)

– Destination IP (where you want to go)

• Your PC MUST have a source IP before you can communicate with the Internet.

Source IP

Destination IP

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.

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

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

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.

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

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)

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

A Snapshot of Server Port Number - 1

A Snapshot of Server Port Number - 2

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

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).

IP Address & Port Number

• In previous slides, cnn.com can find PC1 because cnn.comknows 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

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.

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?

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.

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.

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".

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

Quiz

Helpful memory aid

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.

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)

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

Answer (MCQ)

1. Answer: C, E, F

2. Answer: B, F