03 Iso Osi Tcp Ip Subnetting

7/27/2019 03 Iso Osi Tcp Ip Subnetting

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ISO-OSI 7-Layers TCP-IP Subnetting by MAZHAR IQBAL BUTT.1


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THE OSI REFERENCE MODELThe International Organization for

Standardization (ISO) developedthe Open System Interconnection

(OSI) Reference Model to promotecommunication between dissimilar

computers as a guide for defining aset of open protocols.


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The OSI model provides a

framework (functional guideline) for

defining standards to connect

heterogeneous computers.

This model solves the complicated

problems of communication between

computer systems by dividing the

communication into sub-tasks(layers).


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OSI

LAYER MODEL
http://en.wikipedia.org/wiki/Image:Osi-model-jb.png


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Communication environments separate

the networking functions and application

processing are called LAYERING.

OSI divides the big task of host-to-host

networking called INTERNETWORKING

into a vertical stack.

This OSI stack contains these seven

numbered layers, these indicate distinct

functions.


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Upper layers

7. application

6. presentation

5. session

Lower layers4. transport

3. network

2. data link

1. physical

Higher-level facilitiesApplication

PresentationSession

Network communication

Transport

Network

Physical mediumData Link

Physical


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APPLICATION LAYER

The application layer providesdifferent services to user

applications. It interfaces directly to these

services and provide conversionbetween associated applicationprocesses, after that it issuesrequests to the presentationlayer.


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It contains a variety of protocols

that are commonly needed.

Another application layer function

is file transfer. Different file systems have

different file naming conventions. Transferring a file between two

different systems requireshandling all incompatibilities.


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PRESENTATION LAYER

This layer provides datarepresentation and code formatting.

It provides a way for a remote host toinform the local client how to presentthe data to the application or client.

It ensures that the data that arrivesfrom the network can be used by the

application, and information send bythe application can be transmitted onthe network.


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It directly translates data from

one format to another.

It provides data encryption,

decryption and compression,decompression.

It delivers and format informationfor application layer processing.

It removes the syntacticaldifferences in data representationwithin the end-user systems.


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SESSION LAYER

It establishes, manages andterminates session betweenapplication.

It provides mechanism for managingend-user, host, process operations

termination and restart procedures. It is responsible for dialog control

between nodes. Dialog is a formalconversation in which two nodesagree to exchange data.


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The communications across a network

can take place and controlled in oneof three dialog modes, are Simplex,

Half-duplex, and Full-duplex. Testing for out-of-sequence packets is

handled also.

Sessions enables communication in

organized manner in three phases as

Connection establishment, Datatransfer, Connection release.


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TRANSPORT LAYER

It translates system names intoaddresses.

It divides messages into fragmentsthat fit within the size limitationsestablished by the network.

It allows users to segment/reassembleseveral upper layer application on to

the same transport data stream.It insures host-to-host session

connection.


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This layer is responsible for

addressing, determining routes forsending, managing network trafficproblems, packet switching,routing, data congestion, andreassembling data at the receiving

end to recover the originalmessage.

It ensures that the segmentsdelivered will be acknowledge backto sender.


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It provides retransmission of

segments those are notacknowledged.

Puts segments back into theircorrect sequence at the

destination. To enable packets reassembly in

their original order, this layerincludes a messages sequencenumber in its header.


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Sometimes it provides multiplexing

between the same two end-points.

Delivery may be 'guaranteed' or

connection-oriented streams (likeTCP) or 'best effort' or connection-less

datagram (like UDP). It is also responsible for delivering

messages from a specific process onone computer to the corresponding

process on the destination computer.


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Transport layer assigns a service

access point (SAP ID) to eachpacket. In TCP/IP terms that is

called a port. One more responsibility of the

transport layer is detecting errorsin transmitting data.


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NETWORK LAYER

The network layer operatesindependently of the physical

medium, which is a concern of thephysical layer.

Routers are network layerdevices, they can be used to

forward packets betweenphysically different networks.


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It adds a header to the messages

that includes the source and

destination network address.

This combination of data plus the

network layer is called a packet.

It translates logical addresses and

names into physical addresses for

Packets delivery.


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The addressing which makes this

delivery possible can be thought of

as a universal address as compared

to the local addressing of the MAC.

It determines routes for sending,managing network traffic problems,

packet switching, routing, data

congestion, and reassembling data.


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It control end-to-end flow of

segmentation and reassembly (SAR)

functions for the transmission of large

packets of data which exceed the

maximum transmission unit (MTU).

The Internet Protocol (IP) is the most

common example, and Novell's

Internetwork Packet eXchange (IPX) is

another popular implementation.


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DATA LINK LAYER

It sends data from network layer tophysical layer.

Manages physical layer communicationsbetween connecting systems.

It is responsible for providing node-to-

node communication on a single, localnetwork.

To provide this service, the data linklayer must perform two functions:


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1.It must provide an address

mechanism that enables messages tobe delivered to the correct nodes,Also, it must translate messages from

upper layer into bits that the physicallayer can transmit.

2.Data units at the Data Link layer aremost commonly called frames,although the term packet is used with

some protocols.


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This single layer actually incorporates two

sub-layers as IEEE Logical Link Control(LLC) model.

The lower of the two sub-layers is calledthe media access control (MAC) and theupper sub-layer is the LLC layer.

The MAC layer provides local addressing,error correction, and in some cases

includes a field to distinguish the frametype from other frame types.


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PHYSICAL LAYER

It transmits data over a physical medium

or on network hardware like cables,

cards, electrical, optical, mechanical and

functional interface to the medium.

It is responsible for transmitting bits

(zero & ones) by providing signaling of

the message and the interface between

the sender or receiver and the medium.


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MNEMONICS

The following mnemonics may help youremember the layers sequence and

names:1."People Design Networks To Send

Packets Accurately"

2."Please Do Not Take Sales People'sAdvice"

3."Always Put Some Thought IntoDesigning Programs"


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This is the worlds most popular open-

system (nonproprietary) protocol suitecan be used to communicate across any

set of interconnected networks and areequally well suited for LAN and WAN

communications either for voice, video,

or data.

TCP/IP is a large collection of different

communication protocols based upon the

two original protocols TCP and IP.


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TCP

(Transmission Control Protocol)

The TCP protocol is used for the

transmission of data from an application

to the network.

TCP is responsible for breaking data

down into IP packets before they are

sent, and for assembling the packetswhen they arrive.


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IP

(Internet Protocol)

The IP protocol takes care of thecommunication with other

computers.IP is responsible for the sending and

receiving data packets over theInternet.


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I t t ki


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Internetworking

The first design goal of TCP/IP was tobuild an interconnection of networks that

provided universal communicationservices.

The second aim is to interconnect

different physical networks to form whatappears to the user to be one large

network. A set of interconnectednetworks is called an INTERNETWORK oran INTERNET.

Th TCP i f th t l f


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The TCP is one of the core protocols of

the Internet protocol suite.It also distinguishes data for differentapplications (such as a Web server and

an email server) on the same computer.

TCP supports many of the Internet's

most popular applications, includingHTTP, SMTP, and SSH.

TCP is a connection-oriented, reliable-delivery byte-stream transport layercommunication protocol.

TCP sends data as an unstructured


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TCP sends data as an unstructured

stream of bytes.By using sequence numbers andacknowledgment messages, TCP can

provide a sending node with deliveryinformation about packets transmitted toa destination node.

Where data has been lost in transit fromsource to destination, TCP can retransmit

the data until either a timeout conditionis reached or until successful delivery hasbeen achieved.

TCP i d li t d


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TCP recognizes duplicate messages and

discards them appropriately.If the sending computer is transmitting

too fast for the receiving computer, TCPprovides flow control mechanisms to slow

data transfer.

TCP checks that no packets are lost by

giving each byte a sequence number, to

make sure that data are delivered to theentity at other end in the correct order.

Th h t it f t k h


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The heterogeneity of networks has

expanded further with the

deployment of Ethernet, Token Ring,

Fiber Distributed Data Interface

(FDDI), X.25, Frame Relay,

Switched Multi-megabit Data Service

(SMDS), Integrated Services Digital

Network (ISDN) and Asynchronous

Transfer Mode (ATM).

TCP connections contain three


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TCP connections contain three

phases: Connection establishment

Data transfer Connection termination

A 3-way handshake is used toestablish a connection.

A 4-way handshake is used todisconnect.

In 3-way handshake Server-side opens


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In 3-way handshake, Server-side opens

a socket and listens for a connectionfrom the Client.

The Client-side of a connection initiatesby sending an initial SYN segment to theserver. The server-side should respond

to a valid SYN request with a SYN/ACK.Finally, the Client-side should respond to

the server with an ACK, completing the3-way handshake and connectionestablishment phase.


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The Internet Protocol (IP) is the primary


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The Internet Protocol (IP) is the primary

Network-Layer (Layer 3) protocol in theInternet suite that contains addressing

information and some control information

that enables packets to be routed.

IP is documented in RFC 791 (Request

For Comments).

As IP is connectionless, no specific route

is defined between 2 communicatingnodes.


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Data packets or segments in TCP/IP are


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Data packets or segments in TCP/IP are

only prepared for travel by TCP and oncearrived at destination are reassembledby the receiving TCP program into the

original message. TCP then delivers themessage to the proper session orapplication.

The delivery is done through the 'port'.So, TCP is not moving data physically it

is only 'packing' and 'unpacking' it. Theprograms and hardware for moving dataare called by TCP to do the work.


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TCP/IP assigns a unique number to every


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/ g q y

workstation in the world called IPnumber.

The Internet works under a central

Internet Assigned NumbersAuthority (IANA) for the allocation andassignment of various numeric identifiersneeded for the operation of the Internet.

The IANA assigns values of protocol

parameters, including type codes,protocol numbers, port numbers, Internetaddresses and Ethernet addresses.


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To be able to identify a host on the Internet,


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y ,

each host is assigned an address, the IPaddress, or Internet Address. When the host is

attached to more than one network, it is called

multi-homed and it has one IP address foreach network interface.

An IP address is divided into three parts.

The first part designates the network address,

the second part designates the subnet

address, andthe third part designates the host address.

Traditional IP Address Classes


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The first part of an Internet addressidentifies the network, on which a host

resides, while the second part identifiesthe particular host on a given network.

The network-ID field can also be referred

to as the network-number or the

network-prefix. All hosts on a given

network share the same network-prefixbut must have a unique host-number.

There are five different address classes


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supported by IP addressing. The class ofan IP address can be determined fromthe high-order (left-most) bits.

IP Address Conversion


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FromBinary to Decimal


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ISO-OSI 7-Layers TCP-IP Subnetting by MAZHAR IQBAL BUTT. 61

(/8 Prefixes)

Class A networks are intended mainly foruse with a few very large networks,because they provide only 8 bits for the

network address field.Class A addresses were assigned tonetworks with a very large number ofhosts. The high-order bit in a class Aaddress is always set to zero.

The next seven bits (completing the first


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octet) represent the network ID andprovide 126 possible networks. Theremaining 24 bits (the last three octets)

represent the host ID. Each network canhave up to 16777214 hosts.

Class A addresses use 7 bits for the and 24 bits for the portion of the IP address. That allows for

27-2 (126) networks with 224-2(16777214) hosts each; a total of over 2billion addresses.


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(/16 Prefixes)

Class B networks allocate 16 bits for network

address field. Class B addresses were assignedto medium-sized to large-sized networks.

The two high-order bits in a class B address

are always set to binary 1 0. The next 14 bits(completing the first two octets) represent thenetwork ID. The remaining 16 bits (last two

octets) represent the host ID. Therefore, therecan be 16382 networks and up to 65534 hostsper network.

Class B addresses use 14 bits for the and 16 bits for the portion


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and 16 bits for the portionof the IP address. That allows for 214-2(16382) networks with 216-2 (65534) hostseach; a total of over 1 billion addresses.


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Class C addresses use 21 bits for the and 8 bits for the portion


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and 8 bits for the portionof the IP address. That allows for 221-2(2097150) networks with 28-2 (254) hostseach; a total of over half a billion addresses.


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Class D addresses are employed for multicastgroup usage. A multicast group may contain

one or more hosts, or none at all. The fourhigh-order bits in a class D address are alwaysset to binary 1 1 1 0.

The remaining bits designate the specificgroup, in which the client participates. Whenexpressed in dotted decimal notation,

multicast addresses range from 224.0.0.0through 239.255.255.255.

There are no network or host bits in the


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multicast operations. Packets are passedto a selected subset of hosts on anetwork. Only those hosts registered for

the multicast operation accept thepacket.

Some well-known multicast groupaddresses are assigned by IANA.

i.e. the multicast address 224.0.0.6 is

used for OSPF hello messages, and224.0.0.9 is used for RIP-2.


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Class E is an experimental address notavailable for general use. It is reserved for

future use. The high-order bits in a class Eaddress are set to 1 1 1 1 0.

Extract from RFC1812 Requirements for IPv4

Routers The explosive growth of the Internethas forced a review of address assignmentpolicies.

The traditional uses of general purpose (ClassA, B, and C) networks have been modified toachieve better use of IP's 32-bit address space.

SUMMARY


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Each address contains a self-encoding

key to identify the dividing point betweenthe network-ID and the host-Number,i.e. 0,10,110 etc.

Class A: NET.HOST.HOST.HOST


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Class B: NET.NET.HOST.HOST

Class C: NET.NET.NET.HOST


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IP CLASSES ADDRESS FORMAT


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1111RRRR.RRRRRRRR.RRRRRRRR.RRRRRRRRClass E

1110MMMM.MMMMMMMM.MMMMMMMM.MMMMMMMM

Class D

110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHHClass C

10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHHClass B

0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHHClass A

IP ADDRESS FORMATCLASS

N = The network ID bitsH = The host ID bits

M = The multicast address bitsR = Reserved bits


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All bits 0


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Stands for this:this host (IP address with =0)or this network (IP address with =0).When a host wants to communicate over anetwork, but does not yet know the network IP

address, it may send packets with =0. Other hosts on the network willinterpret the address as meaning this network.

Their reply will contain the fully qualifiednetwork address, which the sender will recordfor future use.

All bits 1


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Stands for all: all networks or all hosts.For example, the following means allhosts on network 128.2 (class B

address):

128.2.255.255

This is called a directed broadcastaddress because it contains both a valid

and a broadcast.

Loopback


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The class A network 127.0.0.0 is defined

as the loopback network.

Addresses from that network are

assigned to interfaces that process data

inside the local system and never access

a physical network (loopback interfaces).


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IANA requests organizations for use ofthe private Internet address space for


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p phosts which require IP connectivitywithin the enterprise network, but do not

require external connections to theglobal Internet.

For this purpose the IANA has reserved

the following three address blocks forprivate Internets:

10.0.0.0 - 10.255.255.255

172.16.0.0 - 172.31.255.255

192.168.0.0 - 192.168.255.255

Any organization that elects to use


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addresses from these reservedblocks can use without contacting

the IANA or an Internet registry.These addresses are never injected

into the global Internet routingsystem, the address space can be

used simultaneously by many

organizations.

SUMMARY


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Private IP Class A : 10.0.0.0 - 10.255.255.255

Class B : 172.16.0.0 - 172.31.255.255 Class C : 192.168.0.0 - 192.168.255.255

Special IP Class A : 127.0.0.0 - 127.255.255.255

Class B : 169.254.0.0 - 169.254.255.255

Public IP All remaining IP Addresses are Public

CLASSFUL IP Addressing andCLASSLESS IP Addressing


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The difference between Classful IPaddressing and Classless IP addressing is

in selecting the number of bits used forthe network ID portion of an IP address.

In Classful IP addressing, the network IDportion can take only the predefinednumber of bits 8, 16, or 24.

In Classless addressing, any number ofbits can be assigned to the network ID.


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ARP - Address Resolution Protocol


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To connect to a remote computer wemust know its IP address , but we do

not need to know its MAC address.

ARP was invented for this reason.

It relates IPs to MAC addresses only on

media that supports broadcasts. Each

node maintains a cache called the ARP

cache, which holds a table of IPs againstMAC addresses.

How ARP works

When IP is requested to send a datagram to


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another IP address, it first looks in the ARPcache to find the corresponding MAC address.

If there is no entry it then attempts to look forit using ARP. In order to do this ARP sends anARP request datagram to all LAN cards using abroadcast address.

If a response is received, the answer isentered to the ARP cache for future use. If

none is received, the request is repeated. ARPDATAGRAMS are not passed through routers.

RARP - Reverse ARP

RARP is intended for use with devices


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that can not store their IP address,usually diskless workstations. Nodes

acting as RARP servers that find a matchfor the MAC address in their RARP tableswill reply with the corresponding IP

address in a RARP response.This system requires that at least oneserver is present and that the server hasa table defining which IP addressesshould be used by each MAC address.

ICMP - Internet Control Message Protocol

E th h IP i d t i d


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Even though IP is a datagram service andthere is no delivery guarantee, ICMP is

provided within IP and can generate error

messages regarding datagram delivery.ICMP uses IP DATAGRAMS to carry its

messages back and forth between relevant

nodes. ICMP error messages are generated bya node recognizing there is a transmission

problem and they are sent back to the

originating address of the datagram that

caused the problem.


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Subnetting, means a single IP class A,B, or C network is further divided into a

ll f h t t f IP b


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smaller group of hosts to form an IP sub-network.

This technique is used to allow a singleIP network address to span multiplephysical networks. IP hosts should

support subnetting. Subnetworks arecreated for security, manageability andperformance of hosts and networks andto reduce network congestion.

Method

Some of the bits of the host ID


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Some of the bits of the host IDportion of an IP address is

further divided into a physicalsub-network ID part and a host

ID part.The sub-network ID is used to

uniquely identify the differentsub-networks within a network.

When is subnetting necessary?

Subnetting is required when one network


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Subnetting is required when one networknumber needs to be distributed acrossmultiple LAN segments. This may be the

case in instances when:

A company uses two or more types of LANtechnology (for example, Ethernet, TokenRing) on their network.

Segments need to be localized for network

management reasons (accounting segment,sales segment, etc.).

The subnet mask of the local network

number produces an even number of


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number produces an even number ofsmaller network numbers, each with a

corresponding range of IP addresses.

e.g. 255.255.255.0, 255.255.127.0,

255.255.0.0.

When a host "A" needs to communicatewith another host "B", it must know

whether host "B" is in the same networkor in a different network.

If the host "B" is in the same networkthen host "A" can send the datagramdirectly to host "B" But if the host B is in


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directly to host B . But if the host B is ina different network, then host "A" must

send the datagram to a proper router.By determining the network class of theIP address of host "B", host "A" can

determine whether host "B" is in thesame network or in a different network.By using the subnet mask host "A" canfind out whether host "B" is in the samesubnet or in a different subnet.

Every Network Starts from its NetworkID and ends with its Broadcast ID.

S 192 168 1 0 (N k ID)


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Start : 192.168.1.0 (Network ID)

End : 192.168.1.255 (Broadcast ID)

A classful network is subnetted bydividing its host ID portion, leaving some

of the bits for the host ID while allocatingothers to a new subnet ID.

These bits are then used to identify

individual subnets within the network,into which hosts are assigned.

Subnet Mask

Subnet mask is a 4 byte (32 bit) number


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Subnet mask is a 4 byte (32 bit) numberused to identify the sub-network ID and

the host ID from an IP address.

All the hosts in a sub-network will have

the same subnet mask.

The subnet mask is used to determine

the bits of the network

identifier. All hosts on the same networkshould have the same subnet mask.

In a subnetting environment, the additionalinformation about which bits are for the subnet

ID and which for the host ID must be


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ID and which for the host ID must becommunicated to devices that interpret IPaddresses.

This information is given in the form of a 32-bitbinary number called a subnet mask.

The term mask comes from the binarymathematics concept called bit masking. Thisis a technique where a special pattern of ones

and zeroes can be used in combination withboolean functions such as AND and OR toselect or clear certain bits in a number.

The subnet mask is a 32-bit binarynumber that accompanies an IP address.It is has a one bit for each


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It is has a one bit for eachcorresponding bit of the IP address that

is part of its network ID or subnet ID,and a zero for each bit of the IPaddresss host ID.

The mask thus tells TCP/IP devices whichbits in that IP address belong to the

network ID and subnet ID, and which arepart of the host ID.

How It Works

An IP address is a 32 bit number dividedinto 4 sections of 8 bits called octets


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An IP address is a 32 bit number dividedinto 4 sections of 8 bits called octets.Each octet is converted from binary to

decimal form and separated with a dot.The address is split into network andhost portion.

The network portion always remainsfixed for a particular network, remaining

bits make up the host portion can bealtered to give the range of addresses toassign to hosts.

To determine where the network portion endsand the host portion begins, a subnet mask (or

netmask, or just mask) is used to fix the


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netmask, or just mask) is used to fix thenetwork portion and allow the host portion tobe changed.

For example, the IP number 38.9.211.0 witha subnet mask of 255.255.255.0. Changingto binary, we get:

So, the netmask as 24 bits, or /24 or 38.9.211.0/24

The fixed bits become the networkportion and the remaining bits become

the host portion, so there are 8 host bits


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the host portion, so there are 8 host bitswhich account for a range from 0-255.

IP protocol standards dictate that we useaddresses of all 0's to refer to thenetwork as a whole, and addresses of all

1's to refer to the broadcast of all hostson the network, so these host addressesmay not be used.

This limits our host range from 1 - 254.


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Broadcast address of all hostson the network

38.9.211.255

Range of valid hosts38.9.211.1 -38.9.211.254

The entire /24 network38.9.211.0/24

After getting network number(/24, /25, or/27), we have the ability to extend the network

portion further into the host-number field byl h i h k


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p ylengthening the netmask.

The number of bits that you extend into the

original host portion determines how manysegments, or subnets, will be produced.

Lengthening the mask by n bits will produce

2^n subnets.

If we used 2 subnet bits. The host portionwould be reduced to six bits. There are 4different combinations of arranging the 2subnet bits, so we arrive at 4 unique subnets.


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(.192 - .255)11000000 - 11111111Subnet 4

(.128 - .191)10000000 - 10111111Subnet 3

(.64 - .127)01000000 - 01111111Subnet 2

(.0 - .63)00000000 - 00111111Subnet 1

Each has 64 Elements.

B d tH t RN t k


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38.9.211.25538.9.211.193 -38.9.211.254

38.9.211.192/26

38.9.211.19138.9.211.129 -38.9.211.190

38.9.211.128/26

38.9.211.12738.9.211.65 -38.9.211.126

38.9.211.64/26

38.9.211.6338.9.211.1 -

38.9.211.6238.9.211.0/26

BroadcastHost RangesNetwork

We have a Network ID of Class C:

192.168.1.0


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and want to make 6 subnets. Class C

IP address has pattern:Net.Net.Net.Host

To break-up host portion into subnets,We will use 2n-2 formula by putting

values {n=0, 1, 2, 3, } to get =6 or>=6.

2n-2

For n=0 20-2=1-2=-1


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For n=1 21-2=2-2=0


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192

160

128

96

64

224

32

0

BID00000111

00000011

00000101

0

0

0

0

0

1

0000001

0000110

0000010

0000100

NID0000000

248163264128

192.168.1.

Vali

dRange

HOST IDNETORK ID

HOST

(5 Remaining Bits)

SUBNET

(3 Bits)

Net.Net.Net

1248163264128


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62

63

33

32

BID11111100

01111100

1

0

1

0000100

NID0000100

248163264128

Subnet-1

192.168.1.

Valid

Range

HOST IDNETORK ID

HOST

(5 Remaining Bits)

SUBNET

(3 Bits)

Net.Net.Net

1248163264128


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94

95

65

64

BID11111010

01111010

1

0

1

0000010

NID0000010

248163264128

Subnet-2

192.168.1.

Valid

Range

Valid RangeBIDNIDSubnet StartsNo

6-Subnets of 192.168.1.0 have following details


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Valid RangeBIDNIDSubnet StartsNo

193 to 222192.168.1.223192.168.1.192192.168.1.1926

161 to 190192.168.1.191192.168.1.160192.168.1.1605

129 to 158192.168.1.159192.168.1.128192.168.1.1284

97 to 126192.168.1.127192.168.1.96192.168.1.963

65 to 94192.168.1.95192.168.1.64192.168.1.642

33 to 62192.168.1.63192.168.1.32192.168.1.321


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1. STATIC LENGTH

(FLSM-Fixed Length Subnet Mask)

2. VARIABLE LENGTH

(VLSM-Variable Length Subnet Mask)

Static Length Subnetting

If all the subnetworks in a single network use

the same subnet mask, it is called as 'StaticLength' subnetting


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Length' subnetting.

Advantage

It is easy to configure a network using 'StaticLength' subnetting. In addition, native IProuting understands only static subnetting.

Disadvantage

A large number of IP addresses will be wasted

because of Irrespective number of hosts in thesubnetwork and single subnet mask is used forall the subnetworks.

Some Examples of FLSM values


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ISO-OSI 7-Layers TCP-IP Subnetting by MAZHAR IQBAL BUTT.

116

255.255.255.128

255.255.255.192255.255.255.224

255.255.255.240

255.255.255.248

255.255.255.252

255.128.0.0

255.192.0.0255.224.0.0

255.240.0.0

255.248.0.0

255.252.0.0

255.254.0.0255.255.0.0

255.255.128.0

255.255.192.0255.255.224.0

255.255.240.0

255.255.248.0

255.255.252.0

255.255.254.0255.255.255.0

Variable Length Subnetting

If the different subnetworks in a single network

use different subnet masks, it is called as'Variable Length' subnetting


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Variable Length subnetting.

Advantage

IP addresses are allocated depending on thenumber of hosts present in the subnetwork. Soavailable host IP addresses are efficiently usedand are not wasted.

Disadvantage

All the routers in a 'Variable Length' subnettednetwork must understand this type ofsubnetting.

Summary

The subnet addresses in which all the bits are

zero or one, are special subnet IP addresses.


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The subnet address in which all the bits are

zero, represents the local subnetwork in whichthe datagram originated.

The subnet address in which all the bits are

one represents a subnet broadcast address.

In the broadcast address, all the other bits

including the network and host ID must beone.

Assignments

Class C Network ID


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Class C Network ID

202.125.147.200

Default Subnet Mask

255.255.255.0

Find the Default Network ID, Broadcast ID

Divide Default Network ID into 10 Subnets

03 Iso Osi Tcp Ip Subnetting

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