CCNA1_M11_TCPIP_Transport_Application (1130712)

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CCNA – Semester1Module 11TCP/IP Application and TransportObjectives• Functions of the TCP/IP transport layer• TCP concepts and processes• TCP/IP application layerTCP/IP Transport LayerWhy we need a transport layer?• Layer 1 allows bit streams to be createdand to travel.• Layer 2 packages those data packets intoframes to be converted to bit streams andmakes data-link delivery possible.• Layer 3 packages data from upper layers inpackets and makes routing and networkdelivery possible.ButButtheytheymademadenonoprovisionprovisionforforassuringassuringourourdatadatareliablyreliablytravelstravelsend-to-endend-to-endacrossacrossthethevastvastnetworknetworkpath.path.Introduction to transport layer• The transport layer data stream is a logicalconnection between the endpoints of a network.• Its primary duties are to transport and regulate theflow of information from source to destinationreliably and accurately.• Transport services include the following basicservices:–––––Segmentation of upper-layer application dataEstablishment of end-to-end operationsTransport of segments from one end host to another end hostFlow control provided by sliding windowsReliability provided by sequence numbers andacknowledgmentsFlow Control• Avoids the problem of a host at one side ofthe connection overflowing the buffers in thehost at the other side.• The two hosts then establish a data-transferrate that is agreeable to both.• Ensures the integrity of the dataSession Establishment• Multiple applications can share the same transportconnection in the OSI reference model.• Different applications can send data segments on a firstcome, first-served basis.

This is referred to as themultiplexing of upper-layer conversations.TCP and UDP• The emphasis of this curriculum is onTCP/IP Ethernet networks.• The TCP/IP protocol of the OSI model Layer4 (transport layer) has two protocols - TCPand UDP.TCP/IP Protocol StackPort007-1CRF• Both TCP and UDP use port (or socket)numbers to pass information to the upperlayers.Range of ports• 2 bytes: 0 – 65535.– Numbers below 255 : for public applications.– Numbers from 255 - 1023 : assigned to companiesfor marketable applications.– Numbers above 1023 : are unregulated.• End systems use port numbers to selectproper applications.• Originating source port numbers aredynamically assigned by the source host;usually, it is a number larger than 1023.TCP• TCP supplies a virtual circuit between end-userapplications. These are its characteristics:– connection-oriented.– reliable.– divides outgoing messages into segments.– reassembles messages at the destination station.– re-sends anything not received.• Protocols that use TCP include FTP, SMTP, HTTP,TelnetTCP Header format167CFR• Protocol that provides reliable full-duplexdata transmission.TCP Header format: Port number••••SourceSource PortPort 1616 bits.bits.DestinationDestination PortPort 1616 bits.bits.TCP Header format: Sequence•• SequenceSequence Number:Number: 3232 bitsbits–– TheThe sequencesequence numbernumber ofof thethefirstfirst datadata octetoctet inin thisthis segmentsegment(except(except whenwhen SYNSYN isis present).present).TCP Header format: Acknowledgment•• AcknowledgmentAcknowledgment Number:Number: 3232 bitsbits–– ThisThis fieldfield containscontains thethe valuevalue ofof thethenextnext sequencesequence numbernumber thethe sendersender ofofthethe segmentsegment isis expectingexpecting toto receive.receive.TCP Header format: Code bits•• ControlControl Bits:Bits: 88 bitsbits–– ACK:ACK: AcknowledgmentAcknowledgment fieldfield significantsignificant–– RST:RST: ResetReset thethe connectionconnection–– SYN:SYN: SynchronizeSynchronize sequencesequence numbersnumbers–– FIN:FIN: NoNo moremore datadata fromfrom sendersenderTCP Header format: Window•• Window:Window: 1616 bitsbits–– TheThe numbernumber ofof datadata octetsoctets beginningbeginningwithwith thethe oneone indicatedindicated inin thetheacknowledgmentacknowledgment fieldfield whichwhich thethe sendersenderofof thisthis segmentsegment isis willingwilling toto accept.accept.Three-way handshakeTCP: Simple acknowledgmentTCP: Sliding window acknowledgmentTCP: Sequence and acknowledgmentUDP• UDP transports data unreliably between hosts.Following are the characteristics:– Connectionless.– Unreliable.– Transmit messages (called user datagrams).– Provides no software checking for message delivery(unreliable).– Does not reassemble incoming messages.– Uses no acknowledgements.• Protocols that use include TFTP, SNMP, DHCP, DNSUDP Header format86-7CRF• UDP is a simple protocol that exchangesdatagrams, without acknowledgments orguaranteed delivery.TCP/IP Application LayerApplication Layer: TCP/IP vs.

OSI• The session and presentation layers from theOSI model were bundled into the applicationlayer of the TCP model.• This means that issues of representation,encoding, and dialog control are handled in theapplication layer rather than in separate lowerlayers as in the OSI model.Session: FunctionsPresentation: FunctionsTCP/IP Application Layer••Handles high-levelprotocols, issues ofrepresentation, encoding,and dialog control.The TCP/IP combines allapplication-related issuesinto one layer, and assuresthis data is properlypackaged for the next layer.– FTP, HTTP, SMTP, DNS,SNMP ...– Format of data, datastructure, encode …– Dialog control, sessionmanagement …Interfaces• Direct network application:– The application layer provides a direct interface for the rest ofthe OSI model by using network applications.– Client server: WEB, FTP, Mail• Indirect network application:– The application layer provides an indirect interface for the restof the OSI model by using standalone applications.– The redirector directs requests from local computer to theproper network resources.

Applications on client never have torecognize the network.– Redirector: network driver, network printerClient-Server application•• TheThe clientclient sideside isis locatedlocated onon thethe locallocalcomputercomputer andand isis thethe requestorrequestor ofof thetheservices.services.•• TheThe serverserver sideside isis locatedlocated onon aa remoteremotecomputercomputer andand providesprovides servicesservices ininresponseresponse toto thethe client’sclient’s requests.requests.Network driver•• TheThe applicationsapplications onon thethe clientclient nevernever havehavetoto recognizerecognize thethe network.network.•• RedirectorsRedirectors expandexpand thethe capabilitiescapabilities ofofnon-networknon-network software.software.Make and Break a connection• The connection to the server wasmaintained only long enough to processthe transaction.– Example : WWW, E-mail• The connection to the server wasmaintained until the user determines thathe/she has finished.– Example : FTP, TelnetDNS• The Domain Name System (DNS) is a systemused on the Internet for translating names ofdomains and their publicly advertised networknodes into IP addresses.• A domain is a group of computers that areassociated by their geographical location ortheir business type.• The DNS system is set up in a hierarchy thatcreates different levels of DNS servers.• Eg: http://www.cdit.com.vn/itc/DNS: System..comcomeduedugovgovvnnvnnvnvncomcomfrfrukukeduedugovgovDNS: Resolve www.yahoo.com..RequestRequestReplyReplyvnvnvnnvnnAddressAddressofofwww.yahoo.comwww.yahoo.comAddressAddressofofcomcomserverserverAddressAddressofofyahoo.comyahoo.comserverservercomcomyahooyahooAddressAddressofofwww.yahoo.comwww.yahoo.comFTP• File Transfer Protocol (FTP) is a reliable,connection-oriented service that uses TCP totransfer files between systems that support FTP.• When files are copied from a server, FTP firstestablishes a control connection between theclient and the server.

Then a second connectionis established, which is a link between thecomputers through which the data istransferred.TFTP• Trivial File Transfer Protocol (TFTP) is aconnectionless service that uses UDP.• TFTP is designed to be small and easy toimplement.• TFTP is used on the router to transferconfiguration files and Cisco IOS imagesand to transfer files between systems thatsupport TFTP.• TFTP can read, write, or mail files to or froma remote server but it cannot list directoriesand currently has no provisions for userauthentication.HTTP• Hypertext Transfer Protocol (HTTP) works with theWorld Wide Web, which is the fastest growing and mostused part of the Internet.• A Web browser is a client-server application, whichmeans that it requires both a client and a servercomponent in order to function.• A Web browser presents data in multimedia formats.

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