osi_ref_model.pdf

1NIC, OSI Reference Model

Networking BasicsNetworking Basics&&

OSI Reference ModelOSI Reference Model


Networking: An Overview Networking: An Overview

A A networknetwork is a group of interconnected is a group of interconnected systems which share services and interact systems which share services and interact with each other by means of a shared with each other by means of a shared communication link. communication link.

These systems can be located anywhere. These systems can be located anywhere.

Network is often classified according to its Network is often classified according to its geographical size. geographical size.


NetworkingNetworking


Benefits of networkingBenefits of networkingGoal of having networking environment is to Goal of having networking environment is to provide services and to reduce the equipment provide services and to reduce the equipment costs. The primary reasons for networking PC's costs. The primary reasons for networking PC's are as follows:are as follows:

Sharing printers and other devicesSharing printers and other devicesProviding Distributed Computing.Providing Distributed Computing.Sharing FilesSharing FilesCentralised Centralised administration of resourcesadministration of resourcesSecurity of Resources.Security of Resources.Personal communications (like ePersonal communications (like e--mail, mail,

chat, audio/video chat, audio/video conferencing)conferencing)

World Wide Web ... and many other usesWorld Wide Web ... and many other uses


Networking BasicsNetworking Basics


Networking BasicsNetworking Basicsnn Network consist many components: Network consist many components:

HardwareHardware Transmission FacilitiesTransmission Facilities Access DevicesAccess Devices Devices that repeat transmitted signalsDevices that repeat transmitted signals

SoftwareSoftware Protocol that define and regulate the way two Protocol that define and regulate the way two

or more device communicate.or more device communicate. Drivers, that guide the functionality of NICDrivers, that guide the functionality of NIC Communication Software.Communication Software.


Networking Basics: HardwareNetworking Basics: Hardwarenn Transmission FacilitiesTransmission Facilities

Are the media used to transport networks signals to their Are the media used to transport networks signals to their destination.destination.

Coaxial Cable, Twisted Pair, FiberCoaxial Cable, Twisted Pair, Fiber-- OpticOptic

nn Access DevicesAccess Devices Is known as Network Interface Card (NIC), and is Is known as Network Interface Card (NIC), and is

responsible for responsible for Properly formatting data so that it can be accepted in the netwoProperly formatting data so that it can be accepted in the networkrk Placing data on the networkPlacing data on the network Accepting transmitted data thats addressed to it.Accepting transmitted data thats addressed to it.

nn Repeaters/HubsRepeaters/Hubs Accepts transmitted signals, amplify it and puts them back Accepts transmitted signals, amplify it and puts them back

on the networkon the network


Network Basics : SoftwareNetwork Basics : Softwarenn ProtocolProtocol

Are standards that allow computer to communicate.Are standards that allow computer to communicate. Define how computer identify one another on a networkDefine how computer identify one another on a network How information be processed once it reach its final How information be processed once it reach its final

destination.destination. Define procedure for handling lost or damaged Define procedure for handling lost or damaged

packets.packets.nn Device DriversDevice Drivers

Is a hardware level program that control NICIs a hardware level program that control NIC NIC, provide an interface for its host operating systemNIC, provide an interface for its host operating system

nn Communication SoftwareCommunication Software That enable the users to communicate and share That enable the users to communicate and share

resourcesresources Windows Explorer, WWW, Telnet, FTPWindows Explorer, WWW, Telnet, FTP


Networking Basics: LANNetworking Basics: LANnn Hardware and Software are to be Hardware and Software are to be

integrated to make a LANintegrated to make a LANnn RepeaterRepeater--less LAN less LAN

nn Hub Based LANHub Based LAN


Networking Basics : LANNetworking Basics : LAN


MultiaccessMultiaccess vs. Pointvs. Point--toto--pointpoint

nn Multiaccess Multiaccess means shared medium.means shared medium. many endmany end--systems share the same physical systems share the same physical

communication resources (communication resources (wire, frequency, ...)wire, frequency, ...) There must be some arbitration mechanism.There must be some arbitration mechanism.

nn PointPoint--toto--pointpoint only 2 systems involvedonly 2 systems involved no doubt about where data came from !no doubt about where data came from !


MultiaccessMultiaccess PointPoint--toto--pointpoint


LAN LAN -- Local Area NetworkLocal Area Network

nn connects computers that are physically connects computers that are physically close together ( < 1 mile).close together ( < 1 mile). high speedhigh speed multimulti--accessaccess

nn Technologies:Technologies: EthernetEthernet 10 Mbps, 100Mbps10 Mbps, 100Mbps Token RingToken Ring 16 Mbps16 Mbps FDDI FDDI 100 Mbps100 Mbps


WAN WAN -- Wide Area NetworkWide Area Network

nn connects computers that are physically connects computers that are physically far apart. longfar apart. long--haul network.haul network. typically slower than a LAN.typically slower than a LAN. typically less reliable than a LAN.typically less reliable than a LAN. pointpoint--toto--pointpoint

nn Technologies:Technologies: telephone linestelephone lines Satellite communicationsSatellite communications


MAN MAN -- Metropolitan Area Metropolitan Area NetworkNetwork

nn Larger than a LAN and smaller than a Larger than a LAN and smaller than a WANWAN-- example: campusexample: campus--wide networkwide network-- multimulti--access networkaccess network

nn Technologies:Technologies: coaxial cable coaxial cable Microwave (Wireless Technology)Microwave (Wireless Technology)


InternetworkInternetworknn Connection of 2 or more distinct Connection of 2 or more distinct

(possibly dissimilar) networks.(possibly dissimilar) networks.nn Requires some kind of network device Requires some kind of network device

to facilitate the connection.to facilitate the connection.

Net A Net B


Network ModelsNetwork Models

nn Using a formal model allows us to deal Using a formal model allows us to deal with various aspects of Networks with various aspects of Networks abstractly.abstractly.

nn We will look at a popular model (OSI We will look at a popular model (OSI reference model).reference model).

nn The OSI reference model is a The OSI reference model is a layeredlayeredmodel.model.


OSI Reference ModelOSI Reference Model

The International Organization for The International Organization for standardization (ISO) proposed for the standardization (ISO) proposed for the standardization of the various protocols standardization of the various protocols used in computer networks (specifically used in computer networks (specifically those networks used to connect open those networks used to connect open systems) is called the systems) is called the Open Systems Open Systems Interconnection Reference ModelInterconnection Reference Model (1984), (1984), or simply the OSI model. or simply the OSI model.


OSI Model OSI Model

Although the OSI model is a just a model Although the OSI model is a just a model (not a specification), it is generally (not a specification), it is generally regarded as the most complete model (as regarded as the most complete model (as well it should be well it should be -- nearly all of the popular nearly all of the popular network protocol suites in use today were network protocol suites in use today were developed before the OSI model was developed before the OSI model was defined).defined).


OSI 7 Layer Model:OSI 7 Layer Model:

77 ApplicationApplication6 6 PresentationPresentation5 5 SessionSession4 4 TransportTransport3 3 NetworkNetwork2 2 DataData--LinkLink1 1 PhysicalPhysical

High level protocols

Low level protocols


LayeringLayeringnn Divide a task into pieces and then solve Divide a task into pieces and then solve

each piece independently (or nearly so).each piece independently (or nearly so).nn Establishing a well defined interface Establishing a well defined interface

between layers makes porting easier. between layers makes porting easier. nn Major Advantages:Major Advantages:

Code ReuseCode ReuseExtensibilityExtensibility


Layering Example: Postal Layering Example: Postal depttdeptt..nn Letter in envelope, address on outsideLetter in envelope, address on outsidenn Adds addressing information, Adds addressing information, pincodepincode..nn Local office drives to airport and Local office drives to airport and

delivers to hub.delivers to hub.nn Sent via airplane to nearest city.Sent via airplane to nearest city.nn Delivered to right officeDelivered to right officenn Delivered to right personDelivered to right person


Letter

LayersLayersLetter Addressed

Envelope

Addressed Envelope


OSI model consists of seven layers


Layering & Headers Layering & Headers nn Each layer needs to add some control Each layer needs to add some control

information to the data in order to do its job. information to the data in order to do its job. nn This information is typically This information is typically prependedprepended to the to the

data before being given to the lower layer.data before being given to the lower layer.nn Once the lower layers deliver the data and Once the lower layers deliver the data and

control information control information -- the peer layer uses the the peer layer uses the control information.control information.


HeadersHeaders

Process

Transport

Network

Data Link

Process

Transport

Network

Data Link

DATA

DATA

DATA

DATA

H

H

H

H

HH


The upper (3) layersThe upper (3) layers

nn Primarily concerned with the Primarily concerned with the application, or what the user can see. application, or what the user can see.

FTP FTP Telnet Telnet SNMPSNMP


Mid (Layers 3Mid (Layers 3--5)5)nn often referred to as transport protocols and often referred to as transport protocols and

are primarily concerned with establishing and are primarily concerned with establishing and maintaining (logical) connections and maintaining (logical) connections and resolving network names. resolving network names.

TCP/IP TCP/IP IPX/SPX IPX/SPX NetBEUI NetBEUI Net BIOS Net BIOS DEC net DEC net AppletalkAppletalk


Lower Level ProtocolsLower Level Protocols

nn (Physical Layer Standards) (Physical Layer Standards) 802.3 (8802.3)Ethernet 802.3 (8802.3)Ethernet 802.4 (8802.4)Token Bus 802.4 (8802.4)Token Bus 802.5 (8802.5)Token Ring (4 Mbps, 16 Mbps) 802.5 (8802.5)Token Ring (4 Mbps, 16 Mbps) FDDI FDDI ATMATM


OSI from the bottom upOSI from the bottom up


The Physical LayerThe Physical Layernn Responsibility:Responsibility:

transmission of raw bits over a transmission of raw bits over a communication channel.communication channel.

nn Issues:Issues: mechanical and electrical interfacesmechanical and electrical interfaces time per bittime per bit distancesdistances


nn Cables (or wireless) are often referred to as Cables (or wireless) are often referred to as the "medium media the "medium media

nn Most common media types: Most common media types: FiberFiber--optic Cableoptic Cable UnshieldedUnshielded--Twisted Pair (UTPTwisted Pair (UTP--100mts, 10100mts, 10--

100mnps)100mnps) Coaxial Cable (ThinCoaxial Cable (Thin--185mts,10mbps, Thick185mts,10mbps, Thick--

500mts,10mbps)500mts,10mbps) Shielded Twisted Pair (STP)Shielded Twisted Pair (STP)

nn These cables are used to carry digital signals These cables are used to carry digital signals between devices.between devices.


Analog SignalingAnalog Signaling

nn analog signals can be analog signals can be represented by a sine represented by a sine wavewave

nn Data in the form of 0s Data in the form of 0s and 1s is extracted from and 1s is extracted from analog signals through analog signals through various voltage and various voltage and frequency modulation frequency modulation techniques.techniques.


Digital SignalingDigital Signaling

nn LANs use digital LANs use digital singling to transfer their singling to transfer their data.data.

nn 0s and 1s are 0s and 1s are represented with or represented with or conveyed through the conveyed through the use of positive and use of positive and negative voltages. A negative voltages. A negative voltage might negative voltage might represent a 0, while a represent a 0, while a positive voltage might positive voltage might represent a 1.represent a 1.


EncodingEncodingnn Now it might be easy, but not Now it might be easy, but not

efficient to have a positive efficient to have a positive voltage represent a 0 and a voltage represent a 0 and a negative voltage represent a negative voltage represent a 1.1. Because of this inefficiency, Because of this inefficiency, various "encoding schemes" various "encoding schemes" use changes in voltages to use changes in voltages to represent one bit or the other, represent one bit or the other, rather than just using a positive rather than just using a positive or negative voltage to represent or negative voltage to represent the two states. the two states.

nn Encoding schemes seek to Encoding schemes seek to efficiently utilize voltage efficiently utilize voltage variations to turn 0s and 1s into variations to turn 0s and 1s into voltages which can be voltages which can be transferred over a cable transferred over a cable (media). (media).


Manchester EncodingManchester Encodingnn Probably the most well known Probably the most well known

encoding scheme is "Manchester encoding scheme is "Manchester EncodingEncoding

nn Manchester encoding uses a Manchester encoding uses a transition during each bit period transition during each bit period (duration) for synchronization as (duration) for synchronization as well as data. So, if the voltages well as data. So, if the voltages changes from a low or negative changes from a low or negative voltage to a high or positive voltage voltage to a high or positive voltage in the middle of its bit period, a in the middle of its bit period, a binary 1 is transmitted. The binary 1 is transmitted. The transition from positive to negative transition from positive to negative voltage in the middle of the bit voltage in the middle of the bit period represents a binary 0. period represents a binary 0.

0 0 1 0 1 1


The Data Link Layer The Data Link Layer --Data Link ControlData Link Control

nn Responsibility:Responsibility: provide an errorprovide an error--free communication linkfree communication link

nn Issues:Issues: framing framing (dividing data into chunks)(dividing data into chunks)

header & trailer bitsheader & trailer bits addressingaddressing

10110110101 01100010011 10110000001


Data Link LayerData Link Layernn TransmitTransmit

Encapsulates packet from Internet Layer in Encapsulates packet from Internet Layer in frameframeadd header for addressing and trailer for error controladd header for addressing and trailer for error control

Header says 00Header says 00--A0A0--CCCC--3939--2D2D--78, Im talking to 78, Im talking to youyou

Uses the physical layer to transmit frameUses the physical layer to transmit framenn ReceiveReceive

Uses physical layer to receive dataUses physical layer to receive data Identifies address, You talking to me?Identifies address, You talking to me? Performs necessary error recoveryPerforms necessary error recovery Delivers data to layer aboveDelivers data to layer above


OSI Layer 2. DataOSI Layer 2. Data--Link Layer Link Layer


Media Access Control:Media Access Control:

Sharing the WireSharing the Wirenn Broadcast a Broadcast a frame frame onto the onto the medium.medium.nn All nodes on the All nodes on the shared mediumshared medium see the see the

message, but ignore it unless it is addressed message, but ignore it unless it is addressed to them.to them.

nn Media access control (MAC) refers to the Media access control (MAC) refers to the need to control when devices transmit.need to control when devices transmit.

nn MAC makes sure no two devices attempt to MAC makes sure no two devices attempt to transmit data at the same time.transmit data at the same time.

nn Essentially using Statistical TDMAEssentially using Statistical TDMA



Media Access Control Media Access Control MethodsMethods

ContentionSimultaneous

Listen then talk

2 talking causes a collision

Token PassingControlled Access

Sequentially take turnsTalk/Listen



Relative PerformanceRelative Performance

In general, contention approaches work better In general, contention approaches work better than controlled approaches for small than controlled approaches for small networks that have low usage.networks that have low usage.

In high volume networks, many devices want to In high volume networks, many devices want to transmit at the same time, and a welltransmit at the same time, and a well--controlled circuit prevents collisions.controlled circuit prevents collisions.


Efficiency:Efficiency:

Data & Transmission Data & Transmission EfficiencyEfficiency

n Data field holds 46 bytes to 1500 bytesn Transmission efficiency - information bits

divided by total number of bitsn Ethernet Efficiency= 1500 / (1500 + 26) = 96.7%


CSMA/CD (IEEE 802.3) CSMA/CD (IEEE 802.3) CarrierCarrier--Sense Multiple Access with Collision DetectionSense Multiple Access with Collision Detection

nn The most common MAC layer access The most common MAC layer access method in Local Area Networksmethod in Local Area Networks

nn CSMA/CD based protocol for the CSMA/CD based protocol for the transmission of data at 10/100 Mbps. transmission of data at 10/100 Mbps. Medium AccessMedium Access Transmission Transmission Collisions DetectionCollisions Detection ReRe--TransmissionTransmission


Ethernet / CSMA/CDEthernet / CSMA/CDn Stations wishing to transmit listen to the

line to determine if it is in use.n If no is heard, the station will transmit a

message called a frame.n Every computer "hears" every

transmission, but only the "destination" computer listens to the message.

n All other stations 'filter' or disregard transmissions not addressed to them.


Ethernet VariationsEthernet Variations

n Ethernet runs over a variety of cable types at 10 Mbps. 10Base2 10Base5 10BaseF 10BaseT 100BaseT 1000BaseT


Broadband vs. Broadband vs. BasebandBaseband

nn Broadband Broadband SignalingSignaling

nn transmission system that transmission system that multiplexes multiple multiplexes multiple independent signals onto independent signals onto one cable. In one cable. In telecommunications telecommunications terminology, any channel terminology, any channel having a bandwidth greater having a bandwidth greater than a voicethan a voice--grade channel grade channel (4 kHz). In LAN terminology, (4 kHz). In LAN terminology, a coaxial cable on which a coaxial cable on which analog signaling is used. analog signaling is used. Also called wideband.Also called wideband.

nn Baseband Baseband SignalingSignalingnn Characteristic of a Characteristic of a

network technology network technology where only one where only one carrier frequency is carrier frequency is used. Ethernet is an used. Ethernet is an example of a example of a basebandbaseband network. network. Also called Also called narrowband. narrowband.


The Network LayerThe Network Layernn Responsibilities:Responsibilities:

path selection between endpath selection between end--systems (routing).systems (routing). subnet flow control.subnet flow control. fragmentation & reassemblyfragmentation & reassembly translation between different network types.translation between different network types.

nn Issues:Issues: packetpacket headersheaders virtual circuitsvirtual circuits


Network layer header Network layer header --examplesexamples

nn protocol suite protocol suite versionversion

nn type of service type of service nn length of the datalength of the datann packet identifierpacket identifiernn fragment numberfragment numbernn time to livetime to live

nn protocolprotocolnn header checksumheader checksumnn source network source network

addressaddressnn destination network destination network

addressaddress


The Transport LayerThe Transport Layernn Responsibilities:Responsibilities:

provides virtual endprovides virtual end--toto--end links between end links between peer processes.peer processes.

endend--toto--end flow controlend flow controlnn Issues:Issues:

headersheaders error detection error detection reliable communicationreliable communication


Modes of ServiceModes of Service

nn connectionconnection--oriented vs. connectionlessoriented vs. connectionlessnn sequencingsequencingnn errorerror--controlcontrolnn flowflow--controlcontrolnn byte stream vs. message basedbyte stream vs. message basednn fullfull--duplex vs. halfduplex vs. half--duplex.duplex.


ConnectionConnection--Oriented vs. Oriented vs. Connectionless ServiceConnectionless Service

nn A connectionA connection--oriented service includes the oriented service includes the establishment of a logical connection (circuit) establishment of a logical connection (circuit) between 2 processes.between 2 processes. establish logical connectionestablish logical connection transfer datatransfer data terminate connection.terminate connection.

nn Connectionless services involve sending of Connectionless services involve sending of independent messages.independent messages.


SequencingSequencing

nn Sequencing provides support for an Sequencing provides support for an order to communications.order to communications.

nn A service that includes sequencing A service that includes sequencing requires that messages (or bytes) are requires that messages (or bytes) are received in the same order they are received in the same order they are sent.sent.


Every IP datagram is an individual Every IP datagram is an individual entity and may take a different entity and may take a different

routeroute


Error ControlError Control

nn Some services require error detection (it Some services require error detection (it is important to know when a is important to know when a transmission error hastransmission error has occuredoccured).).

nn Checksums provide a simple error Checksums provide a simple error detection mechanism.detection mechanism.

nn Error control sometimes involves Error control sometimes involves notification and retransmission.notification and retransmission.


Flow ControlFlow Control

nn Flow control prevents the sending Flow control prevents the sending process from overwhelming the process from overwhelming the receiving process.receiving process.

nn Flow control can be handled a variety of Flow control can be handled a variety of ways ways -- this is one of the major research this is one of the major research issues in the development of the next issues in the development of the next generation of networks (ATM).generation of networks (ATM).


Byte Stream vs. MessageByte Stream vs. Message

nn Byte stream implies an ordered Byte stream implies an ordered sequence of bytes with no message sequence of bytes with no message boundaries.boundaries.

nn Message oriented services provide Message oriented services provide communication service to chunks of communication service to chunks of data calleddata called datagramsdatagrams. .


FullFull-- vs. Halfvs. Half--DuplexDuplex

nn FullFull--Duplex services support the Duplex services support the transfer of data in both directions.transfer of data in both directions.

nn HalfHalf--Duplex services support the Duplex services support the transfer of data in a single direction.transfer of data in a single direction.


EndEnd--toto--End vs. HopEnd vs. Hop--toHoptoHop

nn Many service modes/features such as Many service modes/features such as flow control and error control can be flow control and error control can be done either:done either:

between endpoints of the communication.between endpoints of the communication.--oror--

between every 2 nodes on the path between between every 2 nodes on the path between the endpoints.the endpoints.


EndEnd--toto--EndEndProcess A

Process B


HopHop--byby--HopHop

Process A

Process B


BufferingBuffering

nn Buffering can provide more efficient Buffering can provide more efficient communications. communications.

nn Buffering is most useful for byte stream Buffering is most useful for byte stream services.services.

Process A Process BSendBufferRecv.Buffer


The Session LayerThe Session Layer

nn Responsibilities:Responsibilities: establishes, manages, and terminates establishes, manages, and terminates

sessions between applications.sessions between applications. service location lookupservice location lookup

nn Many protocol suites do not include a Many protocol suites do not include a session layer.session layer.


The Presentation LayerThe Presentation Layer

nn Responsibilities:Responsibilities: data encryptiondata encryption data compressiondata compression data conversiondata conversion

nn Many protocol suites do not include a Many protocol suites do not include a Presentation Layer.Presentation Layer.


The Application LayerThe Application Layer

nn Responsibilities:Responsibilities: anything not provided by any of the other anything not provided by any of the other

layerslayersnn Issues:Issues:

application level protocolsapplication level protocols appropriate selection of type of serviceappropriate selection of type of service


Application LayerApplication Layer

nn Function Function to define a standard set of to define a standard set of commands understood by clients and servers commands understood by clients and servers irrespective of underlying platformirrespective of underlying platform

nn Request / Response modelRequest / Response model


Important SummaryImportant Summary

nn DataData--Link :Link :-- communication between communication between machines on the same network.machines on the same network.

nn Network :Network :-- communication between communication between machines on possibly different machines on possibly different networks.networks.

nn Transport :Transport :-- communication between communication between processes (running on machines on processes (running on machines on possibly different networks).possibly different networks).


Connecting NetworksConnecting Networks

nn Repeater: Repeater: physical layerphysical layer

nn Bridge: Bridge: data link layerdata link layer

nn Router: Router: network layernetwork layer

nn Gateway: Gateway: network layer and above.network layer and above.


RepeaterRepeater

nn Copies bits from one network to anotherCopies bits from one network to anothernn Does not look at any bitsDoes not look at any bitsnn Allows the extension of a network Allows the extension of a network

beyond physical length limitationsbeyond physical length limitations

REPEATER


BridgeBridgenn Copies frames from one network to Copies frames from one network to

anotheranothernn Can operate selectively Can operate selectively -- does not copy does not copy

all frames (must look at dataall frames (must look at data--link link headers).headers).

nn Extends the network beyond physical Extends the network beyond physical length limitations.length limitations.

BRIDGE


RouterRouternn Copies packets from one network to another.Copies packets from one network to another.nn Makes decisions about what Makes decisions about what routeroute a packet a packet

should take (looks at network headers).should take (looks at network headers).

ROUTERROUTER


GatewayGateway

nn Operates as a routerOperates as a routernn Data conversions above the network Data conversions above the network

layer.layer.nn Conversions:Conversions:

encapsulation encapsulation -- use an intermediate network use an intermediate network translation translation -- connect different application connect different application

protocolsprotocolsencryption encryption -- could be done by a gatewaycould be done by a gateway


Encapsulation ExampleEncapsulation Example

Gateway Gateway

nn Provides service connectivity Provides service connectivity even though intermediate even though intermediate network does not support network does not support protocols.protocols.


TranslationTranslation

nn Translate from green protocol to brown Translate from green protocol to brown protocolprotocol

Gateway


Encryption gatewayEncryption gatewayEncryption/Decryption

Gateways

SecureNetwork

Secure Network

GWGW ? ??

Insecure Network


Hardware vs. SoftwareHardware vs. Software

nn Repeaters are typically hardware devices.Repeaters are typically hardware devices.nn Bridges can be implemented in hardware or Bridges can be implemented in hardware or

software.software.nn Routers & Gateways are typically Routers & Gateways are typically

implemented in software so that they can be implemented in software so that they can be extended to handle new protocols.extended to handle new protocols.

nn Many workstations can operate as routers or Many workstations can operate as routers or gateways. gateways.


TCP/IPTCP/IPTransmission Control Protocol / Internet Transmission Control Protocol / Internet

ProtocolProtocol


TCP/IP & OSITCP/IP & OSI

nn In OSI reference model terminology In OSI reference model terminology --the the TCP/IP protocol suite covers the TCP/IP protocol suite covers the network and transport layers. network and transport layers.

nn TCP/IP can be used on many dataTCP/IP can be used on many data--link link layers (can support many network layers (can support many network hardware implementations). hardware implementations).


Comparison of OSI model with TCP/IP model


Internet ProtocolInternet ProtocolThe IP in TCP/IPThe IP in TCP/IP

nn IP is the network layerIP is the network layer packet delivery service (hostpacket delivery service (host--toto--host).host). translation between different datatranslation between different data--link link

protocols.protocols.


IPIP DatagramsDatagrams

nn IP provides connectionless, unreliable IP provides connectionless, unreliable delivery of delivery of IPIP datagramsdatagrams..

nn ConnectionlessConnectionless: each datagram is : each datagram is independent of all others.independent of all others.

nn Unreliable: Unreliable: there is no guarantee thatthere is no guarantee thatdatagramsdatagrams are delivered correctly or at are delivered correctly or at all.all.


IP AddressesIP Addresses

nn IP addresses are not the IP addresses are not the same as the underlying same as the underlying datadata--link (MAC) link (MAC) addresses.addresses.

Why ?Why ?

Re

ns

se

la

er



nn IP is a network layer IP is a network layer -- it must be it must be capable of providing communication capable of providing communication between hosts on different kinds of between hosts on different kinds of networks (different datanetworks (different data--link link implementations).implementations).

nn The address must include information The address must include information about what about what networknetwork the receiving host is the receiving host is on. This makes routing feasible.on. This makes routing feasible.



nn IP addresses are IP addresses are logicallogical addresses (not addresses (not physical)physical)

nn 32 bits.32 bits.nn Includes a network ID and a host ID.Includes a network ID and a host ID.nn Every host must have a unique IP address.Every host must have a unique IP address.nn IP addresses are assigned by a central IP addresses are assigned by a central

authority (the Interauthority (the Inter--NIC at SRI NIC at SRI International).International).


The The fourfour forformats of IP mats of IP AddressesAddresses

00 NetIDNetID

1010

110110 NetIDNetID

1110 Multicast Address

HostIDHostID

NetIDNetID HostIDHostID

HostIDHostID

ClassClassAA

BB

CC

DD8 bits 8 bits 8 bits8 bits


Class Al 128 possible network IDsl over 4 million host IDs per network ID

Class AClass All 128 possible network IDs128 possible network IDsll over 4 million host IDs per network IDover 4 million host IDs per network ID

Class Bl 16K possible network IDs

l 64K host IDs per network ID

Class BClass Bl 16K possible network IDs

l 64K host IDs per network ID

Class Cl over 2 million possible network IDs

l about 256 host IDs per network ID

Class CClass Cl over 2 million possible network IDs

l about 256 host IDs per network ID


Network and Host IDsNetwork and Host IDs

nn A Network ID is assigned to an A Network ID is assigned to an organization by a global authority.organization by a global authority.

nn Host IDs are assigned locally by a Host IDs are assigned locally by a system administrator.system administrator.

nn Both the Network ID and the Host ID Both the Network ID and the Host ID are used for routing.are used for routing.



nn IP Addresses are usually shown in IP Addresses are usually shown in dotted decimal dotted decimal notation:notation:

1.2.3.4 1.2.3.4 00000001 00000010 00000011 0000010000000001 00000010 00000011 00000100nn cscs..rpirpi..eduedu is 128.213.1.1is 128.213.1.1

1010000000 11010101 00000001 00000001000000 11010101 00000001 00000001

CS has a class B networkCS has a class B network


Host and Network AddressesHost and Network Addresses

nn A single network interface is assigned a A single network interface is assigned a single IP address called the single IP address called the hosthostaddress. address.

nn A host may have multiple interfaces, A host may have multiple interfaces, and therefore multiple and therefore multiple hosthost addresses.addresses.

nn Hosts that share a network all have the Hosts that share a network all have the same IP same IP networknetwork address (the network address (the network ID).ID).


IP Broadcast and Network IP Broadcast and Network AddressesAddresses

nn An IP broadcast addresses has a host ID of An IP broadcast addresses has a host ID of all 1s.all 1s.

nn IP broadcasting is not necessarily a true IP broadcasting is not necessarily a true broadcast, it relies on the underlying broadcast, it relies on the underlying hardware technology. hardware technology.

nn An IP address that has a host ID of all 0s is An IP address that has a host ID of all 0s is called a called a network address network address and refers to an and refers to an entire network.entire network.


Mapping IP Addresses to Mapping IP Addresses to Hardware AddressesHardware Addresses

nn IP Addresses are not recognized by IP Addresses are not recognized by hardware.hardware.

nn If we know the IP address of a host, how do If we know the IP address of a host, how do we find out the hardware address ?we find out the hardware address ?

nn The process of finding the hardware The process of finding the hardware address of a host given the IP address is address of a host given the IP address is called called

Address ResolutionAddress Resolution


Reverse Address ResolutionReverse Address Resolution

nn The process of finding out the IP The process of finding out the IP address of a host given a hardware address of a host given a hardware address is calledaddress is called

Reverse Address ResolutionReverse Address Resolution

nn Reverse address resolution is needed Reverse address resolution is needed by diskless workstations when booting.by diskless workstations when booting.


ARPARP

nn The The Address Resolution Protocol Address Resolution Protocol is is used by a sending host when it knows used by a sending host when it knows the IP address of the destination but the IP address of the destination but needs the Ethernet address.needs the Ethernet address.

nn ARP is a broadcast protocol ARP is a broadcast protocol -- every every host on the network receives the host on the network receives the request.request.

nn Each host checks the request against Each host checks the request against its IP address its IP address -- the right one responds.the right one responds.


ARP (cont.)ARP (cont.)nn ARP does not need to be done every ARP does not need to be done every

time an IP datagram is sent time an IP datagram is sent -- hosts hosts rememberremember the hardware addresses of the hardware addresses of each other.each other.

nn Part of the ARP protocol specifies that Part of the ARP protocol specifies that the receiving host should also the receiving host should also remember the IP and hardware remember the IP and hardware addresses of the sending host.addresses of the sending host.


ARP conversationARP conversationHEY - Everyone please listen! Will 192.168.0.44 please send me his/her Ethernet address?

not me

Hi Green! Im 192.168.0.44, and my Ethernet address is 87:A2:15:35:02:C3


RARP conversationRARP conversationHEY - Everyone please listen! My Ethernet address is 22:BC:66:17:01:75.Does anyone know my IP address ?

not me

Hi Green! Your IP address is 128.213.1.17.


Services provided by IPServices provided by IP

nn Connectionless Delivery (each Connectionless Delivery (each datagram is treated individually).datagram is treated individually).

nn Unreliable (delivery is not guaranteed).Unreliable (delivery is not guaranteed).nn Fragmentation / Reassembly (based on Fragmentation / Reassembly (based on

hardware MTU).hardware MTU).nn Routing.Routing.nn Error detection.Error detection.


IP DatagramIP DatagramVERS HL

Fragment Offset

Fragment LengthService

Datagram ID FLAG

TTL Protocol Header Checksum

Source Address

Destination Address

Options (if any)

Data

1 byte1 byte 1 byte 1 byte


IP Datagram FragmentationIP Datagram Fragmentation

nn Each fragment (packet) has the same Each fragment (packet) has the same structure as the IP datagram. structure as the IP datagram.

nn IP specifies that datagram reassembly IP specifies that datagram reassembly is done only at the destination (not on a is done only at the destination (not on a hophop--byby--hop basis).hop basis).

nn If any of the fragments are lost If any of the fragments are lost -- the the entire datagram is discarded (and an entire datagram is discarded (and an ICMP message is sent to the sender).ICMP message is sent to the sender).


IP Flow Control & Error IP Flow Control & Error DetectionDetection

nn If packets arrive too fast If packets arrive too fast -- the receiver the receiver discards excessive packets and sends discards excessive packets and sends an ICMP message to the sender an ICMP message to the sender (SOURCE QUENCH).(SOURCE QUENCH).

nn If an error is found (header checksum If an error is found (header checksum problem) the packet is discarded and an problem) the packet is discarded and an ICMP message is sent to the sender.ICMP message is sent to the sender.


ICMPICMPInternet Control Message ProtocolInternet Control Message Protocolnn ICMP is a protocol used for exchanging ICMP is a protocol used for exchanging

control messages.control messages.nn ICMP uses IP to deliver messages.ICMP uses IP to deliver messages.nn ICMP messages are usually generated ICMP messages are usually generated

and processed by the IP software, not and processed by the IP software, not the user process.the user process.


ICMP Message TypesICMP Message Types

nn Echo RequestEcho Requestnn Echo ResponseEcho Responsenn Destination UnreachableDestination Unreachablenn RedirectRedirectnn Time ExceededTime Exceedednn Redirect (route change)Redirect (route change)nn there are more ...there are more ...


TCPTCP UDPUDP

IPIP

802.3802.3

Process Layer

Transport Layer

Network Layer

Data-Link Layer

ProcessProcess ProcessProcess

ICMP, ARP &

RARP


UDP User Datagram ProtocolUDP User Datagram Protocol

nn UDP is a transport protocolUDP is a transport protocol communication between communication between processesprocesses

nn UDP uses IP to deliverUDP uses IP to deliver datagramsdatagrams to the to the right host.right host.

nn UDP uses UDP uses portsports to provide to provide communication services to individual communication services to individual processes.processes.


PortsPorts

nn TCP/IP uses an abstract destination TCP/IP uses an abstract destination point called a protocol port.point called a protocol port.

nn Ports are identified by a positive integer.Ports are identified by a positive integer.nn Operating systems provide some Operating systems provide some

mechanism that processes use to mechanism that processes use to specify a port. specify a port.


PortsPortsHost AHost A Host BHost B

Process

Process

Process

Process

Process

Process


UDPUDPnn Datagram DeliveryDatagram Deliverynn ConnectionlessConnectionlessnn UnreliableUnreliablenn MinimalMinimal

Source Port Destination Port

Length Checksum

Data

UDP Datagram FormatUDP Datagram Format


TCPTCPTransmission Control ProtocolTransmission Control Protocol

nn TCP is an alternative transport layer TCP is an alternative transport layer protocol supported by TCP/IP.protocol supported by TCP/IP.

nn TCP provides:TCP provides: ConnectionConnection--orientedoriented ReliableReliable FullFull--duplexduplex ByteByte--StreamStream


ConnectionConnection--OrientedOriented

nn Connection oriented Connection oriented means that a means that a virtual connection is established before virtual connection is established before any user data is transferred. any user data is transferred.

nn If the connection cannot be established If the connection cannot be established -- the user program is notified. the user program is notified.

nn If the connection is ever interrupted If the connection is ever interrupted --the user program(s) is notified.the user program(s) is notified.


ReliableReliable

nn ReliableReliable means that every transmission means that every transmission of data is acknowledged by the receiver. of data is acknowledged by the receiver.

nn If the sender does not receive If the sender does not receive acknowledgement within a specified acknowledgement within a specified amount of time, the sender retransmits amount of time, the sender retransmits the data. the data.


Byte StreamByte Stream

nn StreamStream means that the connection is means that the connection is treated as a stream of bytes. treated as a stream of bytes.

nn The user application does not need to The user application does not need to package data in individual package data in individual datagramsdatagrams(as with UDP).(as with UDP).


BufferingBuffering

nn TCP is responsible for buffering data TCP is responsible for buffering data and determining when it is time to send and determining when it is time to send a datagram. a datagram.

nn It is possible for an application to tell It is possible for an application to tell TCP to send the data it has buffered TCP to send the data it has buffered without waiting for a buffer to fill up.without waiting for a buffer to fill up.


Full DuplexFull Duplex

nn TCP provides transfer in both directions.TCP provides transfer in both directions.nn To the application program these To the application program these

appear as 2 unrelated data streams, appear as 2 unrelated data streams, although TCP can piggyback control although TCP can piggyback control and data communication by providing and data communication by providing control information (such as an ACK) control information (such as an ACK) along with user data.along with user data.


TCP PortsTCP Ports

nn InterprocessInterprocess communication via TCP is communication via TCP is achieved with the use of ports (just like achieved with the use of ports (just like UDP). UDP).

nn UDP ports have no relation to TCP UDP ports have no relation to TCP ports (different name spaces).ports (different name spaces).


TCP SegmentsTCP Segments

nn The chunk of data that TCP asks IP to The chunk of data that TCP asks IP to deliver is called a deliver is called a TCP segmentTCP segment..

nn Each segment contains:Each segment contains: data bytes from the byte streamdata bytes from the byte stream control information that identifies the data control information that identifies the data

bytes bytes


TCP Segment Format TCP Segment Format

Destination Port

Options (if any)

Data

1 byte 1 byte

Source Port

Sequence Number

Request Number

1 byte 1 byte

offset Reser. Control Window

Checksum Urgent Pointer


Addressing in TCP/IPAddressing in TCP/IP

nn Each TCP/IP address includes:Each TCP/IP address includes: Internet AddressInternet Address Protocol (UDP or TCP)Protocol (UDP or TCP) Port NumberPort Number


TCP vs. UDPTCP vs. UDPQ: Which protocol is better ?Q: Which protocol is better ?A: It depends on the application.A: It depends on the application.

TCP provides a connectionTCP provides a connection--oriented, oriented, reliable byte stream service (lots of reliable byte stream service (lots of overhead).overhead).

UDP offers minimal datagram delivery UDP offers minimal datagram delivery service (as little overhead as possible).service (as little overhead as possible).


TCP/IP SummaryTCP/IP Summary

nn IP: network layer protocolIP: network layer protocol unreliable datagram delivery between hosts.unreliable datagram delivery between hosts.

nn UDP: transport layer protocolUDP: transport layer protocol unreliable datagram delivery between unreliable datagram delivery between

processes.processes.

nn TCP: transport layer protocolTCP: transport layer protocol reliable, bytereliable, byte--stream delivery between stream delivery between

processes.processes.


IP Addressing and SubIP Addressing and Sub--nettingnetting


IP Address ManagementIP Address Management

nn Managed by the IANAManaged by the IANA (Internet Assigned Numbers Authority)(Internet Assigned Numbers Authority)

nn Host IP addresses are assigned by the Host IP addresses are assigned by the network administrator.network administrator.

nn Managed Statically or Dynamically.Managed Statically or Dynamically.


IP v4IP v4

nn Ipv4 uses 32 bit unique addresses Ipv4 uses 32 bit unique addresses nn Displayed in 4 part (field, byte) dotted Displayed in 4 part (field, byte) dotted

decimal notation. decimal notation. xxxxxx..xxxxxx..xxxxxx..xxxxxx


Breaking down the BytesBreaking down the Bytes

nn Each of the 4 bytes can be broken into Each of the 4 bytes can be broken into a unit of 8 bits.a unit of 8 bits. 10101110.11111000.01100110.0000011010101110.11111000.01100110.00000110


Calculating Byte ValuesCalculating Byte Values

nn Each Bit has a value.Each Bit has a value.nn Calculation starts on the left with the Calculation starts on the left with the

High order bitHigh order bitnn 128+64+32+16+8+4+2+1 = 11111111128+64+32+16+8+4+2+1 = 11111111nn 01111111 = 64+32+16+8+4+2+1 01111111 = 64+32+16+8+4+2+1 nn 10111111 = 128+32+16+8+4+2+110111111 = 128+32+16+8+4+2+1


Network Address Class Network Address Class DeterminationDetermination

nn 5 Classes of IP addresses can be 5 Classes of IP addresses can be created by changing the value of the created by changing the value of the high order bits in the first byte.high order bits in the first byte.


Classes of networks Classes of networks

nn Class AClass Ann Class BClass Bnn Class CClass Cnn Class DClass D


Specifying ClassesSpecifying Classes

nn Class A High Order Bit 0Class A High Order Bit 0nn Class B High Order Bits 10Class B High Order Bits 10nn Class C High Order Bits 11Class C High Order Bits 11nn Class D High Order Bits 1110Class D High Order Bits 1110nn Class E High Order Bits 11110Class E High Order Bits 11110


Class A AddressesClass A Addresses

nn Up to 126 addresses Up to 126 addresses nn Up to 16,777,216 hosts each. Up to 16,777,216 hosts each. nn 11--126.126.xxxxxx..xxxxxx..xxx xxx nn 0 and 127 are reserved0 and 127 are reservednn 10.0.0.0 10.0.0.0 -- 10.255.255.255 are Private 10.255.255.255 are Private

Reserved (NonReserved (Non--Routable Class A Routable Class A Addresses)Addresses)


Class B AddressesClass B Addresses

nn up to 16,384 Networksup to 16,384 Networksnn Each network with 65,000 addressesEach network with 65,000 addressesnn 128128--191.191.xxxxxx..xxxxxx..xxx xxx nn Private / Reserved Class B Addresses Private / Reserved Class B Addresses

172.16.0 172.16.0 -- 172.31.255.255172.31.255.255


Class C AddressesClass C Addresses

nn Up to 2,097,152 class C networks with Up to 2,097,152 class C networks with 254 addresses each 254 addresses each

nn (0 and 255 are reserved) (0 and 255 are reserved) nn The first two high order bits must be 1 & The first two high order bits must be 1 &

1. 1. nn 192192--254.254.xxxxxx..xxxxxx..xxx xxx nn Private Reserved Class C Addresses Private Reserved Class C Addresses

192.168.0.0 192.168.0.0 -- 192.168.255.255192.168.255.255


Class D & EClass D & E

nn Class DClass D-- used for multicasting used for multicasting High Order bits set to 1110 High Order bits set to 1110 224.0.0.0224.0.0.0--239.239.xxxxxx..xxxxxx..xxx xxx Class D addresses can not be assigned to Class D addresses can not be assigned to hosts. hosts.

nn Class EClass E-- experimental experimental High order bits set to 11110 High order bits set to 11110 240240--247.247.xxxxxx..xxxxxx..xxx xxx Class E addresses can not be assigned to Class E addresses can not be assigned to hosts hosts


Private (Reserved Addresses)Private (Reserved Addresses)nn Class A 10.0.0.0 Class A 10.0.0.0 -- 10.255.255.25510.255.255.255nn Class B 172.16.0 Class B 172.16.0 -- 172.31.255.255172.31.255.255nn Class C 192.168.0.0 Class C 192.168.0.0 -- 192.168.255.255192.168.255.255

nn Network Portion of address in a Subnet Network Portion of address in a Subnet must not = all 1s or all 0smust not = all 1s or all 0s


Subnet AddressesSubnet Addresses

nn An organization can subdivide its host An organization can subdivide its host address space into groups called subnets.address space into groups called subnets.

nn The subnet ID is generally used to group The subnet ID is generally used to group hosts based on the physical network hosts based on the physical network topology.topology.

1010 NetIDNetID SubnetIDSubnetID HostIDHostID


SubnettingSubnettingrouter

Subnet 1128.213.1.x

Subnet 2128.213.2.x

Subnet 3128.213.3.x


SubnettingSubnetting

nn Subnets can simplify routing.Subnets can simplify routing.nn IP subnet broadcasts have aIP subnet broadcasts have a hostIDhostID of of

all 1s.all 1s.nn It is possible to have a single wire It is possible to have a single wire

network with multiple subnets.network with multiple subnets.


SubSub--nettingnetting

nn SubSub--netsnets-- SubSub--nets divide a single nets divide a single network into smaller networks. network into smaller networks.

nn Routers are used to connect the smaller Routers are used to connect the smaller SubnetworksSubnetworks to the main network.to the main network.

nn SubnettingSubnetting borrows host bits and adds borrows host bits and adds them to the main network's section. them to the main network's section.


Sub Network BorrowingSub Network Borrowing

nn [x][[x][xxxxxxxxxxxxxx] (x=0 or 1)] (x=0 or 1)nn ^ Network ^ Hosts^ Network ^ Hosts


SubSub--nettingnetting

nn SubSub--netsnets-- SubSub--nets divide a single nets divide a single network into smaller networks. network into smaller networks.

nn Routers are used to connect the smaller Routers are used to connect the smaller SubnetworksSubnetworks to the main network.to the main network.

nn SubnettingSubnetting borrows host bits and adds borrows host bits and adds them to the main network's section.them to the main network's section.

nn Subnet MaskSubnet Mask-- tells TCP/IP which bits tells TCP/IP which bits have been borrowed for subhave been borrowed for sub--netting.netting.


Subnet Mask ContinuedSubnet Mask Continued

nn Flat networks are networks which do not Flat networks are networks which do not employ subnets. employ subnets. IP Address 137.150.64.1= IP Address 137.150.64.1= 10001001.10010110.01000000.0000000110001001.10010110.01000000.00000001 Subnet Mask 255.255.0.0Subnet Mask 255.255.0.0 11111111.11111111.00000000.0000000011111111.11111111.00000000.00000000


Subnet Mask Cont.Subnet Mask Cont.

nn The Subnet Mask identifies which The Subnet Mask identifies which portion of the address is used for the portion of the address is used for the network, and which portion is used for network, and which portion is used for the host.the host.


Common SubnetsCommon Subnetsnn 255255 1111111111111111

nn 254254 1111111011111110

nn 252252 1111110011111100

nn 248248 1111100011111000

nn 240240 1111000011110000

nn 224224 1110000011100000

nn 192192 1100000011000000

nn 128128 1000000010000000

nn 00 00


Theoretical Networks CreatedTheoretical Networks CreatedNumber ofSubNetworks

Host BitsUsed

2 1 bits

4 2 bits

8 3 bits

16 4 bits

32 5 bits

64 6 bits

128 7 bits

255 8 bits


Class A Subnet TableClass A Subnet Tablenn # of Subnets# of Subnets Hosts per subnetHosts per subnet Number of bitsNumber of bits Subnet MaskSubnet Masknn 00 invalidinvalid 11 invalidinvalidnn 22 4,194,3024,194,302 22 255.192.0.0255.192.0.0nn 66 2,097,1502,097,150 33 255.224.0.0255.224.0.0nn 1414 1,048,5741,048,574 44 255.240.0.0255.240.0.0nn 3030 524,286524,286 55 255.248.0.0255.248.0.0nn 6262 262,142262,142 66 255.252.0.0255.252.0.0nn 126126 131,070131,070 77 255.254.0.0255.254.0.0nn 254254 65,53465,534 88 255.255.0.0255.255.0.0


Class B Subnet TableClass B Subnet Tablenn # of Subnets# of Subnets Hosts per subnetHosts per subnet Number of bitsNumber of bits Subnet MaskSubnet Masknn 00 invalidinvalid 11 invalidinvalidnn 22 16,38216,382 22 255.255.192.0255.255.192.0nn 66 8,1908,190 33 255.255.224.0255.255.224.0nn 1414 4,0944,094 44 255.255.240.0255.255.240.0nn 3030 2,0462,046 55 255.255.248.0255.255.248.0nn 6262 1,0221,022 66 255.255.252.0255.255.252.0nn 126126 510510 77 255.255.254.0255.255.254.0nn 254254 254254 88 255.255.255.0255.255.255.0


Class C Subnet TableClass C Subnet Tablenn # of Subnets# of Subnets Hosts per subnetHosts per subnet Number of bitsNumber of bits Subnet MaskSubnet Masknn 00 invalidinvalid 11 invalidinvalidnn 22 6262 22 255.255.255.192255.255.255.192nn 66 3030 33 255.255.255.224255.255.255.224nn 1414 1414 44 255.255.255.240255.255.255.240nn 3030 66 55 255.255.255.248255.255.255.248nn 6262 22 66 255.255.255.252255.255.255.252


Calculating First and Last Calculating First and Last AddressAddress

nn When bits are borrowed from the host When bits are borrowed from the host portion of the address and given to the portion of the address and given to the network portion of the address, the network portion of the address, the ranges of address should consist of a ranges of address should consist of a network address and a first and last network address and a first and last host address.host address.


Class B ExampleClass B Example

nn 172.16.172.16.xxxxxx..xxxxxxnn 255.255.224.0255.255.224.0nn 3 subnet bits taken3 subnet bits takennn 8 subnets created 8190 hosts each8 subnets created 8190 hosts each


Class B: 3 3bit Address Class B: 3 3bit Address RangesRanges

nn 0 [000]172.16.0.1 to 172.16.31.2540 [000]172.16.0.1 to 172.16.31.254nn 1 [001]172.16.32.1 to 172.16.63.2541 [001]172.16.32.1 to 172.16.63.254nn 2 [010]172.16.64.1 to 172.16.95.2542 [010]172.16.64.1 to 172.16.95.254nn 3 [011]172.16.96.1 to 172.16.127.2543 [011]172.16.96.1 to 172.16.127.254nn 4 [100]172.16.128.1 to 172.16.159.2544 [100]172.16.128.1 to 172.16.159.254nn 5 [101]172.16.160.1 to 172.16.191.2545 [101]172.16.160.1 to 172.16.191.254nn 6 [110]172.16.192.1 to 172.16.223.2546 [110]172.16.192.1 to 172.16.223.254nn 7 [111]172.16.224.1 to 172.16.255.2547 [111]172.16.224.1 to 172.16.255.254


Class C Addresses : 2 bitsClass C Addresses : 2 bits

nn Subnet Mask 255.255.255.192Subnet Mask 255.255.255.192nn 4 Subnets 62 hosts each4 Subnets 62 hosts each

nn 0 192.168.121.1 to 192.168.121.620 192.168.121.1 to 192.168.121.62nn 1 192.168.121.65 to 192.168.121.1261 192.168.121.65 to 192.168.121.126nn 2 192.168.121.129 to 192.168.121.1902 192.168.121.129 to 192.168.121.190nn 3 192.168.121.193 to 192.168.121.2543 192.168.121.193 to 192.168.121.254


Class C Example : ContinuedClass C Example : Continued

nn 2 subnet bits = [2 subnet bits = [xxxx][][xxxxxxxxxxxx]]nn All 0 and 1 hosts are excludedAll 0 and 1 hosts are excludednn Possible network addressesPossible network addressesnn 0 = [00][0 = [00][xxxxxxxxxxxx]]nn 64 = [01][64 = [01][xxxxxxxxxxxx]]nn 128= [10][128= [10][xxxxxxxxxxxx]]nn 192= [11][192= [11][xxxxxxxxxxxx]]


nn 0 = [00][0 = [00][xxxxxxxxxxxx] .1 to .62] .1 to .62 [00][000001] to [00][111110][00][000001] to [00][111110]

nn 64 = [01][64 = [01][xxxxxxxxxxxx] .65 to .126] .65 to .126 [01][000001] to [01][111110][01][000001] to [01][111110]

nn 128= [10][128= [10][xxxxxxxxxxxx] .129 to .190] .129 to .190 [10][000001] to [10][111110][10][000001] to [10][111110]

nn 192= [11][192= [11][xxxxxxxxxxxx] .193 to .254] .193 to .254 [11][000001] to [11][111110][11][000001] to [11][111110]

Class C Example: Bit Class C Example: Bit CountingCounting


Subnet Calculations & Subnet Calculations & CalculatorsCalculators

nn Be careful when converting decimal to Be careful when converting decimal to binary that bits are not dropped.binary that bits are not dropped.

nn SubSub--net Calculators are available and net Calculators are available and can be used to calculate address can be used to calculate address ranges and network addresses for ranges and network addresses for hosts.hosts.


IP Version 6IP Version 6

nn Necessary because we are running out of 32 Necessary because we are running out of 32 bit IPv4 Addresses. And Routing Tables are bit IPv4 Addresses. And Routing Tables are becoming too large. becoming too large.

nn IP v6 uses 128 bit addressesIP v6 uses 128 bit addresses

nn IP v 6 Equipment will also support IPv4. IP v 6 Equipment will also support IPv4.

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