osi_ref_model.pdf
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1NIC, OSI Reference Model
Networking BasicsNetworking Basics&&
OSI Reference ModelOSI Reference Model
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2NIC, OSI 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.
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3NIC, OSI Reference Model
NetworkingNetworking
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4NIC, OSI Reference Model
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
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5NIC, OSI Reference Model
Networking BasicsNetworking Basics
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6NIC, OSI Reference Model
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.
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7NIC, OSI Reference Model
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
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8NIC, OSI Reference Model
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
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9NIC, OSI Reference Model
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
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10NIC, OSI Reference Model
Networking Basics : LANNetworking Basics : LAN
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11NIC, OSI Reference Model
Networking Basics : LANNetworking Basics : LAN
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12NIC, OSI Reference Model
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 !
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13NIC, OSI Reference Model
MultiaccessMultiaccess PointPoint--toto--pointpoint
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14NIC, OSI Reference Model
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
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15NIC, OSI Reference Model
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
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16NIC, OSI Reference Model
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)
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17NIC, OSI Reference Model
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
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18NIC, OSI Reference Model
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.
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19NIC, OSI Reference 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.
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20NIC, OSI Reference 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).
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21NIC, OSI Reference Model
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
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22NIC, OSI Reference Model
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
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23NIC, OSI Reference Model
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
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24NIC, OSI Reference Model
Letter
LayersLayersLetter Addressed
Envelope
Addressed Envelope
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25NIC, OSI Reference Model
OSI model consists of seven layers
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26NIC, OSI Reference Model
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.
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27NIC, OSI Reference Model
HeadersHeaders
Process
Transport
Network
Data Link
Process
Transport
Network
Data Link
DATA
DATA
DATA
DATA
H
H
H
H
HH
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28NIC, OSI Reference Model
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
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29NIC, OSI Reference Model
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
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30NIC, OSI Reference Model
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
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31NIC, OSI Reference Model
OSI from the bottom upOSI from the bottom up
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32NIC, OSI Reference Model
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
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33NIC, OSI Reference Model
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.
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34NIC, OSI Reference Model
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35NIC, OSI Reference Model
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36NIC, OSI Reference Model
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.
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37NIC, OSI Reference Model
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.
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38NIC, OSI Reference Model
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).
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39NIC, OSI Reference Model
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
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40NIC, OSI Reference Model
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
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41NIC, OSI Reference Model
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
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42NIC, OSI Reference Model
OSI Layer 2. DataOSI Layer 2. Data--Link Layer Link Layer
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43NIC, OSI Reference Model
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
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44NIC, OSI Reference Model
Media Access Control:Media Access Control:
Media Access Control Media Access Control MethodsMethods
ContentionSimultaneous
Listen then talk
2 talking causes a collision
Token PassingControlled Access
Sequentially take turnsTalk/Listen
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45NIC, OSI Reference Model
Media Access Control:Media Access Control:
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.
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46NIC, OSI Reference Model
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%
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47NIC, OSI Reference Model
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
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48NIC, OSI Reference Model
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.
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49NIC, OSI Reference Model
Ethernet VariationsEthernet Variations
n Ethernet runs over a variety of cable types at 10 Mbps. 10Base2 10Base5 10BaseF 10BaseT 100BaseT 1000BaseT
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51NIC, OSI Reference Model
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.
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52NIC, OSI Reference Model
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
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53NIC, OSI Reference Model
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
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54NIC, OSI Reference Model
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
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55NIC, OSI Reference Model
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.
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56NIC, OSI Reference Model
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.
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57NIC, OSI Reference Model
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.
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58NIC, OSI Reference Model
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
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59NIC, OSI Reference Model
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.
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60NIC, OSI Reference Model
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).
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61NIC, OSI Reference Model
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. .
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62NIC, OSI Reference Model
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.
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63NIC, OSI Reference Model
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.
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64NIC, OSI Reference Model
EndEnd--toto--EndEndProcess A
Process B
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65NIC, OSI Reference Model
HopHop--byby--HopHop
Process A
Process B
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66NIC, OSI Reference Model
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
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67NIC, OSI Reference Model
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.
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68NIC, OSI Reference Model
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.
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69NIC, OSI Reference Model
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
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70NIC, OSI Reference Model
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
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71NIC, OSI Reference 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).
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72NIC, OSI Reference Model
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.
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73NIC, OSI Reference Model
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
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74NIC, OSI Reference Model
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
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75NIC, OSI Reference Model
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
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76NIC, OSI Reference Model
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
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77NIC, OSI Reference Model
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.
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78NIC, OSI Reference Model
TranslationTranslation
nn Translate from green protocol to brown Translate from green protocol to brown protocolprotocol
Gateway
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79NIC, OSI Reference Model
Encryption gatewayEncryption gatewayEncryption/Decryption
Gateways
SecureNetwork
Secure Network
GWGW ? ??
Insecure Network
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80NIC, OSI Reference Model
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.
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81NIC, OSI Reference Model
TCP/IPTCP/IPTransmission Control Protocol / Internet Transmission Control Protocol / Internet
ProtocolProtocol
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82NIC, OSI Reference Model
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).
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83NIC, OSI Reference Model
Comparison of OSI model with TCP/IP model
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84NIC, OSI Reference 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.
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85NIC, OSI Reference Model
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.
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86NIC, OSI Reference Model
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
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87NIC, OSI Reference Model
IP AddressesIP Addresses
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.
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88NIC, OSI Reference Model
IP AddressesIP Addresses
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).
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89NIC, OSI Reference Model
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
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90NIC, OSI Reference Model
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
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91NIC, OSI Reference Model
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.
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92NIC, OSI Reference Model
IP AddressesIP Addresses
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
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93NIC, OSI Reference Model
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).
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94NIC, OSI Reference Model
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.
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95NIC, OSI Reference Model
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
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96NIC, OSI Reference Model
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.
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97NIC, OSI Reference Model
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.
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98NIC, OSI Reference Model
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.
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99NIC, OSI Reference Model
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
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100NIC, OSI Reference Model
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.
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101NIC, OSI Reference Model
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.
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102NIC, OSI Reference Model
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
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103NIC, OSI Reference Model
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).
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104NIC, OSI Reference Model
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.
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105NIC, OSI Reference Model
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.
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106NIC, OSI Reference Model
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 ...
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107NIC, OSI Reference Model
TCPTCP UDPUDP
IPIP
802.3802.3
Process Layer
Transport Layer
Network Layer
Data-Link Layer
ProcessProcess ProcessProcess
ICMP, ARP &
RARP
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108NIC, OSI Reference Model
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.
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109NIC, OSI Reference Model
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.
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110NIC, OSI Reference Model
PortsPortsHost AHost A Host BHost B
Process
Process
Process
Process
Process
Process
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111NIC, OSI Reference Model
UDPUDPnn Datagram DeliveryDatagram Deliverynn ConnectionlessConnectionlessnn UnreliableUnreliablenn MinimalMinimal
Source Port Destination Port
Length Checksum
Data
UDP Datagram FormatUDP Datagram Format
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112NIC, OSI Reference Model
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
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113NIC, OSI Reference Model
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.
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114NIC, OSI Reference Model
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.
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115NIC, OSI Reference Model
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).
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116NIC, OSI Reference Model
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.
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117NIC, OSI Reference Model
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.
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118NIC, OSI Reference Model
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).
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119NIC, OSI Reference Model
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
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120NIC, OSI Reference Model
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
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121NIC, OSI Reference Model
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
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122NIC, OSI Reference Model
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).
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123NIC, OSI Reference Model
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.
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124NIC, OSI Reference Model
IP Addressing and SubIP Addressing and Sub--nettingnetting
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125NIC, OSI Reference Model
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.
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126NIC, OSI Reference Model
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
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127NIC, OSI Reference Model
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
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128NIC, OSI Reference Model
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
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129NIC, OSI Reference Model
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.
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130NIC, OSI Reference Model
Classes of networks Classes of networks
nn Class AClass Ann Class BClass Bnn Class CClass Cnn Class DClass D
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131NIC, OSI Reference Model
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
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132NIC, OSI Reference Model
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)
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133NIC, OSI Reference Model
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
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134NIC, OSI Reference Model
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
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135NIC, OSI Reference Model
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
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136NIC, OSI Reference Model
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
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137NIC, OSI Reference Model
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
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138NIC, OSI Reference Model
SubnettingSubnettingrouter
Subnet 1128.213.1.x
Subnet 2128.213.2.x
Subnet 3128.213.3.x
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139NIC, OSI Reference Model
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.
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140NIC, OSI Reference Model
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.
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141NIC, OSI Reference Model
Sub Network BorrowingSub Network Borrowing
nn [x][[x][xxxxxxxxxxxxxx] (x=0 or 1)] (x=0 or 1)nn ^ Network ^ Hosts^ Network ^ Hosts
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142NIC, OSI Reference Model
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.
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143NIC, OSI Reference Model
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144NIC, OSI Reference Model
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
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145NIC, OSI Reference Model
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.
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146NIC, OSI Reference Model
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
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147NIC, OSI Reference Model
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
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148NIC, OSI Reference Model
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
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149NIC, OSI Reference Model
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
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150NIC, OSI Reference Model
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
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151NIC, OSI Reference Model
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.
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152NIC, OSI Reference Model
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
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153NIC, OSI Reference Model
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
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154NIC, OSI Reference Model
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
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155NIC, OSI Reference Model
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]]
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156NIC, OSI Reference Model
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
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157NIC, OSI Reference Model
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.
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158NIC, OSI Reference Model
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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