Embed Size (px)
Citation preview
2. THE OPEN SYSTEMS INTERCONNECTION (OSI) MODEL AND NETWORK PROTOCOLS.
2.1 Know Network Communications2.2 Understand a Local Wired Network2.3 Understand basic concept of internet connection and information sent across internet2.4 Understand Network Services2.5 Apply email client server2.6 Apply Addressing Schemes for TCP/IP suite
2.1.1 DESCRIBE THE PURPOSE OF THE OSI MODEL AND EACH OF ITS LAYERS.
2.1.1 Describe the purpose of the OSI Model and of each of its layers.
• OSI model is used:
– to describe what tasks a protocol suite
performs as we explore how data moves across
a network.
• A protocol suite is most easily defined:
– as a set of rules used to determine how
computers communicate with each other.
3
Open System Interconnection (OSI)
• Open System Interconnection (OSI) merupakan sebuah
model untuk komunikasi komputer yang terdiri dari 7
layer atau lapisan (OSI 7 layer).
• Sebelum adanya OSI yang merupakan standard
antarabangsa ini, setiap syarikat komputer seperti IBM
dan DEC mempunyai seni bina masing-masing sehingga
produk yang dihasilkan mereka tidak boleh saling inter-
operasi.
4
Contoh soalan peperiksaan:Explain the purpose of various layers?
Terangkan secara ringkas, fungsi/tujuan bagi setiap lapisan?
1.The Physical Layer – coordinates the functions required to
transmit a bit stream over a physical medium.
2.The Data Link Layer – is responsible for delivering data units
from one station to the next without errors.
6
3. The Network Layer – is responsible for the source-to-
destination delivery of a packet across multiple network links.
4.The Transport Layer – is responsible for the source-to-
destination delivery of the entire message.
Contoh soalan peperiksaan:Explain the purpose of various layers?
Terangkan secara ringkas, fungsi/tujuan bagi setiap lapisan?
5. The Session Layer – establishes, maintains, and synchronizes the
interactions between communicating devices.
6.The Presentation Layer – ensures interoperability between communicating
devices through transformation of data into a mutually agreed-upon format.
7.The Application Layer – enables the users to access the network.
8
International Standards Organization's(ISO)
• The International Standards
Organization's(ISO) OSI model serves
as a standard template for describing
a network protocol stack.
9
Is learning OSI layer is important?
1. The OSI Reference Model provides the
basis for understanding how technologies
like Ethernet has some important
similarities;
10
Is learning OSI layer is important?
2. It explains how a PC can communicate using any of
several different sets of protocols, even
simultaneously;
3. It is an important part of understanding the differences
between interconnection devices such as repeaters,
hubs, bridges, switches and routers; and it also
explains how many WAN technologies interoperate.
11
The purpose of OSI model:• U can take these as an answer for questions like” what is the
purpose of OSI model?”
1. To promote the goal of communications between different types of systems by encouraging the development of internetworking devices.
2. To make sure that all functions needed for communications are addressed and that none are left out.
3. To avoid duplication of functions thereby increasing efficiency.
4. To design independence for each layer from other layers. This facilitates the interoperability of products from different manufacturers and insures that the end-user can substitute one vendor’s product for another.
5. To produce a learning tool that can be used to understand how communications in modern computer systems works.
12
Methods of using the OSI model
• There are THREE(3) different ways to use the OSI model:
1. Bottom up – troubleshooting by going from the physical layer (layer 1) up to the application layer (layer 7)
2. Top down - troubleshooting by going from the application layer (layer 7) down to the physical layer (layer 1)
3. Divide and Conquer – in this method, you start with whatever layer you feel is most likely the cause of the problem, then move in whatever direction you feel is the more likely cause of the issue (either up or down the OSI model)
13
2.1.2 Define specific functions belonging to each OSI Model layer.
Application layer
Layer Description/keywords
Protocols Devices/ components
Data encapsulatio
n
Application
• Provides an interface for a service to operate
• Communication partner identification
• HTTP• Telnet• FTP• TFTP• SNMP
Userinformationand data
15
Presentation layer
LayerDescription/
keywordsProtocols
Devices/ component
s
Data encapsulat
ion
Presentation
• Data format (file formats)
• Encryption, translation, and compression
• Data format and exchange
JPEG,BMP, TIFF,PICT, MPEG,WMV, AVI, ASCII, EBCDICMIDI, WAV
Data
16
Session layer
Layer Description/keywords Protocols
Devices/ components
Data encapsulatio
n
Session
• Keeps data streams separate (session identification)
• Set up, maintain, and tear down communication sessions
• SQL• NFS• ASP• RPC• X
windowData
17
Transport layer
Layer Description/keywords
Protocols Devices/ components
Data encapsulati
on
Transport
• Reliable (connection oriented) and unreliable (connectionless) communications
• End-to-end flow control
• Port and socket numbers
• Segmentation, sequencing, and combination
• TCP (connection-oriented)
• UDP (connectionless)
Segments
18
Network layer
LayerDescription/key
wordsProtocols
Devices/ component
s
Data encapsulat
ion
Network
• Logical addresses
• Path determination (identification and selection)
• Routing packets
• IP• IPX• AppleTal
k• DECNET
• Routers• Layer 3
switchesPackets
19
Data Link layerLayer Description/keywords Protocols
Devices/ components
Data encapsulati
on
Data link
• Convert bits into bytes and bytes into frames
• MAC address, hardware address
• Logical network topology
• Media access• Flow control
o Acknowledgements
o Bufferingo Windowing
• Parity and CRC
• LAN protocols : 802.2(LLC), 802.3 (Ethernet), 802.5(Token Ring), 802.11(Wireless)
• WAN protocols: HDLC, PPP, Frame Relay, ISDN, ATM
• Network Interface Card (NIC) transceivers
• Switch• Bridge
Frames
20
Physical layerLayer Description/keywords Protocols Devices/
componentsData encapsulation
Physical
• Move bits across media
• Cables, connectors, pin positions
• Electrical signals (voltage, bit synchronization)
• Physical topology (network layout)
• EIA/TIA 232(serial signaling)
• V.35 (modem signaling)
• Cat5• RJ45
• Transmission media (cable and wires)
• Media connectors
• Transceivers (including transceivers built into NICs)
• Modems• Repeaters• Hubs• Multiplexers• CSUs/DSUs• Wireless
Access Points
Bits
21
Questions
1. Name all SEVEN(7) OSI layers, starting with the lowest.
2. Which OSI layer handles addressing on the local physical network?
3. What layers are referred to as the hardware layers?
22
Questions
4. Which OSI layer is responsible for adding a header that includes routing information?Network Layer
5. Which OSI layer is considered the media access control layer? Data Link Layer
6. TCP functions at what layer of the OSI model? Transport Layer 23
Questions 7. Which layer is responsible for converting
data packets from the Data Link layer into electrical signals ?
8. At which layer is routing implemented, enabling connections and path selection between two end systems. ?
9. Which layer defines how data is formatted, presented, encoded, and converted for use on the network ?
24
Questions 10.Which layer is responsible for creating,
managing and terminating sessions between applications ?
11.Which layer provides logical addressing that routers will use for path determination ?
12.Which layer specifies voltage, wire speed, and pinout cables and moves bits between devices ?
25
2.1.3 DESCRIBE HOW TWO NETWORK NODES COMMUNICATE THROUGH THE OSI MODEL.
Data flow through the OSI model
27
Communication between systems
28
29
OSI REFERENCE MODEL
REAL WORLD EQUIVALENT TASKS
TCP/IP PROTOCOL
ApplicationProgram to program transfer of information
ApplicationPresentationText formatting and display code conversion
SessionEstablishing, maintaining, and coordinating communication
Transport Accurate delivery, service quality Transport
NetworkTransport routes, message handling and transfer
Internet
Data LinkCoding, addressing, and transmitting information Network
InterfacePhysical
The hardware connections (the NIC and the cables)
30
2.1.4 DESCRIBE THE STRUCTURE AND PURPOSE OF DATA PACKETS AND FRAMES.
32
The structure and purpose of data packets
• It turns out that everything you do on the
Internet involves packets.
• For example, every Web page that you receive
comes as a series of packets, and every e-mail
you send leaves as a series of packets. Networks
that ship data around in small packets are called
packet switched networks.
33
2.1.4 Explain the structure and purpose of data packets and frames.
• A packet is a basic unit of communication over a
digital network.
• A packet is also called a datagram, a segment, a
block, a cell or a frame, depending on the
protocol.
• When data has to be transmitted, it is broken
down into similar structures of data, which are
reassembled to the original data chunk once they
reach their destination.
34
Data Packet
• On the Internet, the network breaks an e-
mail message into parts of a certain size in
bytes.
• These are the packets.
35
Data Packets and Frames
• Each packet carries the information
that will help it get to its destination
-- the sender's IP address, the
intended receiver's IP address,
something that tells the network how
many packets this e-mail message
has been broken into and the number
of this particular packet. 36
Data Packets and Frames
Data Packets and Frames
• The packets carry the data in the protocols that the
Internet uses: Transmission Control Protocol/Internet
Protocol (TCP/IP).
• Each packet contains part of the body of your message.
• A typical packet contains perhaps 1,000 or 1,500 bytes.
37
Packets and protocols
• Packets vary in structure depending on the
protocols implementing them.
• VoIP uses the IP protocol, and hence IP packets.
• On an Ethernet network, for example, data is
transmitted in Ethernet frames.
38
Structure of packets
• The structure of a packet depends on the type of
packet it is and on the protocol.
• Normally, a packet has a header and a payload.
• The header keeps overhead information about the
packet, the service and other transmission-related
things.
39
Structure of packets
• For example, an IP packet includes:
– The source IP address
– The destination IP address
– The sequence number of the packets
– The type of service
– Flags
– Etc
– The payload is the data it carries.
40
Protocol
41
• There are rules governing how data is
transferred over networks, how they are
compressed, how they are presented on
the screen and so on.
• These set of rules are called protocols.
42
Protocol
Protocol
• There are many protocols, each one governing
the way a certain technology works.
• For example, the IP protocol defines a set of
rules governing the way computers use IP
packets to send data over the Internet or any
other IP-based network.
43
Protocol• It also defines addressing in IP. Likewise, we have other protocols like: 1. TCP: Transmission Control Protocol, used for the reliable transmission of data
over a network.
2. HTTP: Hypertext Transfer Protocol, used for transmitting and displaying information in the form of web pages on browsers.
3. FTP: File Transfer Protocol, used for file transfer (uploading and downloading) over the Internet
4. SMTP: Simple Mail Transfer Protocol, used for email
5. Ethernet: Used for data transmission over a LAN.
6. Wi-Fi: One of the wireless protocols.
44
2.1.5 RELATE TWO TYPES OF ADDRESSING COVERED BY THE OSI MODEL.
2.1.5 Explain TWO (2) types of addressing covered by the OSI Model.
• Each node has TWO(2) types of addresses:
1. Network address: follows hierarchical addressing scheme
• Can be assigned through OS software• Network layer addresses, logical
addresses, or virtual addresses
2. Physical address
46
2.2 UNDERSTAND A LOCAL WIRED NETWORK
2.2.1 Explain the MAC address of a Host using ipconfig /all command.2.2.2 Relate a standard IEEE 802.3 Ethernet Frame based on a given source and destination devices.2.2.3 Give logical address of a computer.2.2.4 Give IP address of a computer.
2.2.1 Explain the MAC address of a Host using ipconfig /all command.
• Physical addressing – MAC address (Media Access Control)– Ethernet communication:
– each interface has a MAC address– each device may look at the data, but only the interface that
matches the destination MAC will respond
• Ipconfig:
– Is used to find out your current TCP/IP settings.
– With IPCONFIG you can find out your IP
Address, find your Default Gateway and find
your Subnet Mask.
– This is a very handy network tool for finding
your local IP address.
ipconfig command
• ipconfig /all:
– To display all your IP information for all
adapters.
– With ipconfig /all you can also find out your
DNS Server and MAC Address.
– This will show your full TCP/IP configuration for
all adapters on your Windows machine.
ipconfig/all command
2.2.2 Relate a standard IEEE 802.3 Ethernet Frame based on a given source and destination devices.• Preamble – beginning of the timing• SFD (Start Frame Delimiter) – marks the end of the timing, but
beginning of the frame• Destination MAC• Source MAC• Length/Type
– Length – tells which protocol receives the data– Type – number of bytes of data
• Encapsulation – packet of information• FCS (Frame Check Sequence) – checks for damaged frames
2.2.3 Give logical address of a computer.• MAC vs. IP• IP Address (Logical Address):
– assigned based on where the host is located– assigned by the administrator
• Parts of an IP address:– Network – same for all hosts connected to the LAN– Host – unique to each host on the network
2.2.4 Give IP address of a computer.
• A logical address is:– the address that is given or assigned to a device
which registers its presence on the internet highway. – At a particular time this address will be unique for the
device but it may change at some times in future.– IPv4 is an example of Logical Address.
2.3 UNDERSTAND BASIC CONCEPT OF INTERNET CONNECTION AND INFORMATION SENT ACROSS INTERNET
2.3.1 LIST INTERNET SERVICE PROVIDER (ISPS)
Internet Service Providers (ISP) in Malaysia
1. Celcom Broadband – Broadband services by Celcom, based on HSDPA
2. iZZi – Wireless broadband
3. Jaring – Pioneer Internet Service Provider
4. Maxis Broadband – Broadband services by Maxis, based on HSDPA
5. P1 – Wi-Fi and WiMax Broadband, by Green Packet
Internet Service Providers (ISP) in Malaysia
59
6. PenangFON – Fibre Speed Internet Broadband
7. REDtone – Telecommunication solutions provider, VoIP,
Internet, Leased Lines, WiMax8. Streamyx
– Broadband access (ADSL), by TM9. TIME Broadband
– Zone, Fusion, BizNet, HomeNet, NetLink
2.3.2 DESCRIBE THE RELATIONSHIP BETWEEN ISP AND INTERNET
4.1.3 The ISPs Relationship With the Internet
• ISPs use a POP (Post Office Protocol) to provide service to end users.
• There are many POPs in an ISPs network.
Post Office Protocol (POP)In computing, the Post Office
Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection.
POP and IMAP (Internet Message Access Protocol) are the two most prevalent(common) Internet standard protocols for e-mail retrieval.
Post Office Protocol (POP)
Virtually all modern e-mail clients and servers support both. The POP protocol has been developed
through several versions, with version 3 (POP3) being the current standard.
Like IMAP, POP3 is supported by most webmail services such as Hotmail, Gmail and Yahoo! Mail.
63
2.3.3 EXPLAIN THE IMPORTANCE OF THE INTERNET PROTOCOLS (IP)
2.3.3 Importance of the Internet Protocol (IP)
• Must run Internet Protocol (IP) software to communicate on Internet.
• IP protocol is one of the TCP/IP (Transmission Control Protocol / Internet Protocol) Protocols .
• As Ethernet uses Frames, IP uses Packets.
• Each IP packet must contain a valid source and destination IP address.
2.3.3 Importance of the Internet Protocol (IP)
• The IP Packet (datagram)• Has a header
which contains the source and destination IP addresses.
• IP addresses must be unique on the Internet.
• Computers in homes, small businesses and other organizations obtain their IP configuration from their ISP.
2.3.4 EXPLAIN THE PACKETS TRAVEL THROUGH THE INTERNET BY USING PING AND TRACEROUTE
The Routing Process, Ping, And Traceroute3. In this example, the host wants to send data to a device
at IP address 20.1.1.2.
4. The host is attached to only one network, 10.0.0.0 /8.
5. The host will then send the data to its default gateway, which in this case happens to be a Cisco router.
6. When this datagram is sent by the host, the destination IP address will be that of the host at 20.1.1.2.
7. However, the destination MAC address will be that of the router interface closest to the sending host.
8. The router receives the datagram, “unpacks” it, and sends it to the routing process.
9. The router will then match the IP destination address against its routing table.
70
Using PING And TRACEROUTE To Test Network Connectivity• ICMP (Internet Control Message Protocol) offers two
network connectivity testing functions.
• The ping command sends five ICMP packets to the
intended destination.
• Ping will then return one of several symbols to indicate
whether IP connectivity exists, and if not, a clue to
what the issue is.
• The ping is an ICMP Echo Request; the ping reply is an
ICMP Echo Reply.71
Consider our earlier example. If the host on network 10.0.0.0 /8 has trouble reaching the host on 20.0.0.0 /8, ping helps diagnose the problem.
72
1. Ping process
73
• The two general replies from a ping are
“!!!!!” and “…..”.
• The exclamation points indicate IP
connectivity exists between the hosts; five
periods indicate that the ping packets were
unable to find the destination host.
2. Traceroute
74
• The second ICMP tool you should be
familiar with is traceroute.
• Where ping simply tells you whether IP
connectivity is or is not present, traceroute
displays the path the packet takes to reach
its destination.
Traceroute
75
• Traceroute works by sending out ICMP
packets with a Time To Live (TTL) of one to
find the first step to the final destination.
• It will then send a packet with a TTL of
two, and the TTL value increases until the
final destination is found.
Traceroute
76
• When that happens, the entire path will be
displayed on your console.
• If the final destination cannot be found, asterisks
will start to appear on your screen.
• This is a sort of error message – it means the TTL
has been exceeded.
• To abort a ping or traceroute in progress, press
<CTRL-SHIFT-6> twice in rapid succession.
Traceroute
77
• A great “1-2-3” method to troubleshoot
routing problems:
1. Ping the destination.
2. If the pings don’t come back, run show ip route
to make sure your local device has a route to the
destination.
3. If a route exists, use traceroute to determine
which downstream router can’t route the packet.
Question
1. Which definition describes the term Internet?A. a group of PCs connected together on
a LANB. a group of PCs connected together by
an ISPC. a network of networks that connects
countries around the worldD. a worldwide collection of networks
controlled by a single organization78
Question
2. What type of connection point is a point of presence (POP)?A. between a client and a hostB. between two local networksC. between a computer and a switchD. between an ISP and a home-based LAN
79
Question
5. Which THREE(3) elements are required to successfully connect to the Internet? (Choose three.)
A. an IP addressB. file sharing enabledC. a network connectionD. server services enabledE. access to an Internet service providerF. an address obtained directly from the RIR
80
Answer
1. C2. D3. A, B, and E4. C5. A, C, and E
81
2.4 UNDERSTAND NETWORK SERVICES
2.4.1 Define Domain Name Service (DNS).2.4.2 Relate ping command, a browser and nslookup to identify the relationship between domain names and IP addresses.2.4.3 Explain DNS in a LAN.2.4.4 Describe e-mail protocols in clients and servers: SMTP, POP3, and IMAP4
2.4.1 DEFINE DOMAIN NAME SERVICE (DNS).
2.4.1 Define Domain Name System
• Definition:– A system for converting host names and
domain names into IP addresses on the Internet or on local networks that use the TCP/IP protocol.
– Sistem untuk menukar nama hos dan nama domain ke dalam alamat IP di Internet atau pada rangkaian tempatan yang menggunakan protokol TCP / IP.
84
Domain Name System
• For example, when a Web site
address is given to the DNS either by
typing a URL in a browser or behind
the scenes from one application to
another, DNS servers return the IP
address of the server associated with
that name.85
Domain Name System
• In this hypothetical example, www.company.com would be converted into the IP address 204.0.8.51.
• Without DNS, you would have to type the four numbers and dots into your browser to retrieve the Web site, which, of course, you can do.
• Try finding the IP of a favourite Web site and type in the dotted number instead of the domain name!
86
2.4.2 RELATE PING COMMAND, A BROWSER AND NSLOOKUP TO IDENTIFY THE RELATIONSHIP BETWEEN DOMAIN NAMES AND IP ADDRESSES.
Relate ping command to identify the relationship between domain names and IP addresses.
• The PING command can be used to check if a domain name is resolving to an IP address, and if that IP address can be reached from your machine.
Relate a browser and nslookup to identify the relationship between domain names and IP addresses.
• In Windows, you can do plenty of things using command line.
• Converting a domain name to its IP address using the nslookup command is one of them.
• You can also find IP address of any website’s host machine.
Here’s is the step by step procedure:
1. Click on Start button and type cmd in the search box. Press “Enter”.
2. Windows command prompt will open. Now type nslookup ftp.yahoo.com and press enter.
3. It will show you Yahoo FTP IP address. This is IP address of the server where yahoo.com is hosted. Similarly you can find host machines for any other website.
4. If you want to look up IP address of a website then type nslookup in the command prompt and press enter.
5. Now enter the domain name of any website and press enter. It will show you the IP address of that particular site. For example you typed google.com and pressed enter. It returned Google’s IP address: 209.85.231.104.– It means if you type
http://209.85.231.104 in a browser’s address bar, google.com will open.
• Similarly you can convert any other domain name into its IP address. You can also check the result by typing the IP address in the browser address bar.
• Now, for the more tech savvy folks among you, the nslookup command is used for testing out DNS servers.
• Remember, for websites that don’t have a dedicated IP address, you could get different results each time you use this command.
2.4.3 EXPLAIN DNS IN A LAN.
2.4.4 DESCRIBE E-MAIL PROTOCOLS IN CLIENTS AND SERVERS: SMTP, POP3, AND IMAP4
Overview
• SMTP, POP3 and IMAP are TCP/IP protocols used for mail delivery.
• If you plan to set up an email server such as Mail Server, you must know what they are used for.
• Each protocol is just a specific set of communication rules between computers.
99
SMTP (Simple Mail Transfer Protocol)
• SMTP stands for Simple Mail Transfer Protocol.
• SMTP is used when email is delivered from an email client, such as Outlook Express, to an email server or when email is delivered from one email server to another.
• SMTP uses port 25. 100
POP3 (Post Office Protocol)
• POP3 stands for Post Office Protocol.
• POP3 allows an email client to download an email from an email server.
• The POP3 protocol is simple and does not offer many features except for
download.
• Its design assumes that the email client downloads all available email from
the server, deletes them from the server and then disconnects.
• POP3 normally uses port 110.
101
IMAP (Internet Message Access Protocol)
• IMAP stands for Internet Message Access Protocol.
• IMAP shares many similar features with POP3.
• It, too, is a protocol that an email client can use to download email from an email server.
• However, IMAP includes many more features than POP3.
• The IMAP protocol is designed to let users keep their email on the server.
• IMAP requires more disk space on the server and more CPU resources than POP3, as all emails are stored on the server. IMAP normally uses port 143.
102
2.6.1 COMPARE THE ADDRESSING SCHEME OF TCP/IP: TCP/IP CLASSES, BINARY AND DOTTED DECIMAL NOTATION, SUBNET MASK.
2.6.1 Compare the addressing scheme of TCP/IP: TCP/IP classes, binary and dotted decimal notation,
subnet mask.
• TCP/IP uses 32 bits, or four numbers
between 0 and 255, to address a
computer.
104
IP Addresses• Each computer must have an IP address before it can
connect to the Internet.
• Each IP packet must have an address before it can be
sent to another computer.
• This is an IP address: 192.68.20.50
This might be the same IP address:
www.w3schools.com
105
An IP Address Contains 4 Numbers
• Each computer must have a unique IP address.
• This is your IP address: 203.82.87.102
• TCP/IP uses four numbers to address a computer. The numbers are always between 0 and 255.
• IP addresses are normally written as four numbers separated by a period, like this: 192.168.1.50.
106
32 Bits = 4 Bytes
• In computer terms, TCP/IP uses 32 bits addressing. One byte is 8 bits. TCP/IP uses 4 bytes.
• One byte can contain 256 different values:– 00000000, 00000001, 00000010, 00000011,
00000100, 00000101, 00000110, 00000111, 00001000 .......and all the way up to 11111111.
• Now you know why a TCP/IP address is four numbers between 0 and 255.
107
Network Classes
• Internet addresses are allocated by the InterNIC (http://www.internic.net ), the organization that administers the Internet.
• These IP addresses are divided into classes. • The most common of these are classes A, B, and
C.
• Classes D and E exist, but are not generally used by end users.
108
Network Classes
• Each of the address classes has a different default subnet mask.
• You can identify the class of an IP address by looking at its first octet.
109
Following are the ranges of Class A, B, and C Internet addresses, each with an example address:
• Class A – networks use a default subnet mask of
255.0.0.0 and have 0-127 as their first octet.
– The address 10.52.36.11 is a class A address.
– Its first octet is 10, which is between 1 and 126, inclusive.
110
Following are the ranges of Class A, B, and C Internet addresses, each with an example address:
• Class B – networks use a default subnet mask of
255.255.0.0 and have 128-191 as their first octet.
– The address 172.16.52.63 is a class B address.
– Its first octet is 172, which is between 128 and 191, inclusive.
111
Following are the ranges of Class A, B, and C Internet addresses, each with an example address:
• Class C – networks use a default subnet mask of
255.255.255.0 and have 192-223 as their first octet.
– The address 192.168.123.132 is a class C address.
– Its first octet is 192, which is between 192 and 223, inclusive.
112
• In some scenarios, the default subnet
mask values do not fit the needs of
the organization, because of the
physical topology of the network, or
because the numbers of networks (or
hosts) do not fit within the default
subnet mask restrictions.113
The following table shows which bytes of the IP address are assigned to you and the range of numbers within each byte that are available for you to assign to your hosts.
114
Class Byte 1 range
Byte 2 range
Byte 3 range
Byte 4 range
A 0 - 127 1 - 254 1 - 254 1 – 254
B 128 - 191Pre-
assigned by internet
1 - 254 1 – 254
C 192 - 223Pre-
assigned by internet
Pre-assigned
by internet1 - 254
Dotted Decimal Notation
• IP addresses are normally expressed in dotted-decimal format, with four numbers separated by periods, such as 192.168.123.132.
• To understand how subnet masks are used to distinguish between hosts, networks, and sub networks, examine an IP address in binary notation.
115
Binary and Dotted Decimal Notation• For example, the dotted-decimal IP address
192.168.123.132 is (in binary notation) the 32
bit number
110000000101000111101110000100.
• This number may be hard to make sense of, so
divide it into four parts of eight binary digits.
116
Binary and Dotted Decimal Notation
• These EIGHT(8) bit sections are known as octets.
• The example IP address, then, becomes 11000000.10101000.01111011.10000100.
• This number only makes a little more sense, so for most uses, convert the binary address into dotted-decimal format (192.168.123.132).
• The decimal numbers separated by periods are the octets converted from binary to decimal notation.
117
IP Addressing Scheme
• An IP address has TWO(2) parts.
• The first part of an IP address is
used as a network address, the
second part as a host address.
118
IP Addressing Scheme
• If you take the example 192.168.123.132 and divide it into these two parts you get the following:
119
Increments of an IP Address:
• 0.0.0.0• 0.0.0.1• …increment 252 hosts…• 0.0.0.254• 0.0.0.255• 0.0.1.0• 0.0.1.1• …increment 252 hosts…• 0.0.1.254• 0.0.1.255• 0.0.2.0• 0.0.2.1• …increment 4+ billion hosts…• 255.255.255.255 120
Subnet Mask
• The second item, which is required for
TCP/IP to work, is the subnet mask.
• The subnet mask is used by the
TCP/IP protocol to determine whether
a host is on the local subnet or on a
remote network.
121
Subnet Mask
• In TCP/IP, the parts of the IP address that are used as the network and host addresses are not fixed, so the network and host addresses above cannot be determined unless you have more information.
• This information is supplied in another 32-bit number called a subnet mask. 122
Subnet Mask
• In this example, the subnet mask is 255.255.255.0.
• It is not obvious what this number means unless you know that 255 in binary notation equals 11111111; so, the subnet mask is:
123
Subnet Mask
• Lining up the IP address and the subnet mask together, the network and host portions of the address can be separated:
124
Subnet Mask
• The first 24 bits (the number of ones in the subnet mask) are identified as the network address, with the last 8 bits (the number of remaining zeros in the subnet mask) identified as the host address. This gives you the following:
125
Subnet Mask
• So now you know, for this example using a 255.255.255.0 subnet mask, that the network ID is 192.168.123.0, and the host address is 0.0.0.132.
• When a packet arrives on the 192.168.123.0 subnet (from the local subnet or a remote network), and it has a destination address of 192.168.123.132, your computer will receive it from the network and process it.
126
Subnet Mask
• Almost all decimal subnet masks convert to binary numbers that are all ones on the left and all zeros on the right.
• Some other common subnet masks are:
127
Uses of Subnet Masks
1. Identifies a Network.2. Isolates the Network ID and Host ID.3. Determines the number of
host/terminals that could be used on the same network.
4. Reduces Network traffic.
128
ANY QUESTION/COMMENT?
129
Questions
1. Internet Protocol (IP) addresses are how many bits long?
2. The address 68.56.189.17 belongs to which IP class?
3. What is the range of the first octet on a Class A TCP/IP address?
4. What is the subnet mask for a Class C TCP/IP address?
130
Questions
5. What is the binary number 10101011 in base 10?
6. What is the base 10 number 255 in binary?
7. What is the network address for the TCP/IP address 199.5.5.5? What is the computer address for the TCP/IP address 199.5.5.5? 131
2.6.2 EXPLAIN PUBLIC AND PRIVATE IP ADDRESS
2.6.2 What is Public IP address?
• Public IP Addresses (also known as Static IP Addresses) are IP addresses that are visible to the public.
• Because these IP addresses are public, they allow other people to know about and access your computer, like a Web server.
• In some cases, you do not want people to access your computer or you want to restrict certain individuals from accessing your computer or server.
133
What is Private IP address?
• These addresses can be used on a private network, but they’re not routable through the public Internet.
• This not only creates a measure of much-needed security, but it also conveniently saves valuable IP address space.
134
Current Private IP addresses as follows:
• Class A– 10.0.0.0 through 10.255.255.255
• Class B– 172.16.0.0 through 172.31.255.255
• Class C– 192.168.0.0 through 192.168.255.255
135
2.6.3 EXPLAIN UNICAST, BROADCAST, AND MULTICAST ADDRESSES
Unicast
• A unicast IP address is an IP address uniquely identifying a host in a network.
• The datagram with a unicast IP address is received and processed by only a single host.
• For example, the IP address 192.9.205.21 is a unicast IP address.
137
Broadcast address
• The datagram with a broadcast IP address is received and processed by all the hosts in the local network.
• For example, the IP addresses 255.255.255.255,192.9.205.255,180.10.255.255,10.255.255.255 are broadcast IP addresses.
138
Multicast
• A multicast address is an IP address identifying a particular group of hosts in network.
• This group of hosts is called a multicast group.
• For example, the IP address 225.2.100.1 is a multicast IP address.
139
2.6.4 RELATE HOW IP ADDRESSES ARE OBTAINED:STATIC ADDRESSESDYNAMIC ADDRESSES
2.6.4 What are fixed and dynamic IP addresses?
• In a traditional TCP/IP network architecture each computer is assigned a permanent IP address.
• This requires manual configuration of each and every computer.
• Once the address is assigned it will not change, unless someone does it manually.
• It is called a fixed IP address.
141
What are fixed and dynamic IP addresses?
• When hundreds or thousands of computers are involved this can be a lot of work.
• Sometimes networks are reconfigured and large numbers of machines must be given new IP addresses.
• Each time a computer is added care must be taken to ensure that it does not use an IP address already assigned to another computer on the same network.
• To improve this situation, Dynamic Host Configuration
Protocol (DHCP) was developed.
142
What are fixed and dynamic IP addresses?
• A DHCP server is a software program that assigns IP addresses to computers with no manual intervention.
• This has tremendous advantages in virtually
any network environment.
• Administrators of large networks save many hundreds of hours per year over manual configuration of computers.
143
What are fixed and dynamic IP addresses?
• Computers may be added or removed with no impact on the network configuration and no concerns about address conflict.
• Users on even the smallest networks benefit as they do not need to know how to configure a TCP/IP control panel.
• A computer on such a network is said to have a dynamic IP address.
144
Dynamic IP Addresses
• The biggest advantages of Dynamic IP
Addressing are
i. less security risk.
ii. the computer is assigned a new IP
address each time the customer logs on.
iii. they are cost effective.
iv. there is automatic network configuration.
145
Dynamic IP Addresses
• In contrast, Dynamic IP addressing should
not be used for VOIP, VPN, playing online
games or game hosting because Dynamic
IP addressing is less reliable(trusted) then
Static IP addressing and could cause the
service to disconnect while you are on a
VOIP, VPN or gaming.
146
2.6.7 Dynamic Host Configuration Protocol (DHCP)
server
• Dynamic Host Configuration Protocol
(DHCP) is 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.
147
Dynamic Host Configuration Protocol (DHCP) server
• A DHCP Server assigns IP addresses to client computers.
• This is very often used in enterprise networks to reduce configuration efforts.
• All IP addresses of all computers are stored in a database that resides on a server machine. 148
DHCP Server
• Normally the DHCP server provides the client with at least this basic information: i. IP Addressii. Subnet Maskiii. Default Gateway
149
DHCP Server
• Other information can be provided as well, such as Domain Name Service (DNS) server addresses and Windows Internet Name Service (WINS) server addresses.
• The system administrator configures the DHCP server with the options that are parsed out to the client.
150
