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GT ECE 4110 - Introduction and Overview

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1ECE4110Internetwork ProgrammingIntroduction and OverviewListen to wireDetect a preambleRead Destination AddressBroadcastAddressMy AddressRead DataFrame ContentsEndofFramePerformIntegrityCheckCheckPassed?Deliver data toDesignatedProcessIgnoreTransmissionDiscardData EXAMPLE GENERAL NETWORK ALGORITHMYesNoNoYesYesNoYesYesNoNoAre signals detecteddata carrying or noise?Is the listening computerthe intended party oris it for someone else?Where does themessage end?Did the computer get agood message or is itcorrupted?3DIX Ethernet Data Frame FormatPreamble(8 Bytes)DestinationMAC Address(6 Bytes)SourceMAC Address(6 Bytes)Type(2 Bytes)Data46-1500 bytesCRC(4 Bytes)• Preamble - alternating 0’s and 1’s with last bit a l. Must not be noise if see this.• Destination medium access control (MAC) address - compare this to our ownhardwired network interface card (NIC ) address. Standards exist and manufacturescomply.– Normally a NIC knows its own address and the broadcast address.• Source MAC address - sender’s NIC address.• Type -so we know what kind of data transporting, one example is Internet Protocol.• Cyclic Redundancy Check - so we can tell if what we got was received correctly, ifnot throw it away.• Aside: After the Ethernet Frame, a 12 Byte Interframe Gap must always follow.Note: Receive process does not look at data, that is done elsewhere.Note: Data is in most network technologies called a “packet.”Gap12 Bytes4ROUTING CONCEPTS7936548211Output port X1A3Output port A4ComputerXComputerYFEDCBA1AA2Network Number (Address)RouterComputer X on Network1wants to send a message to computer Y on Network5a Network5 NETWORK ADDRESS IS SOFTWARE CONFIGURABLEPreambleDestinationMac AddressSource Mac AddressType INFO CRCDestination5 : YSource1 : XOtherStuffData ROUTING TABLESComputer XDestinationNetwork5Distance3Next RouterAOutputPortX16DestinationNetworkOutput PortNext RouterDistance Router A’s Routing Table: Routers can Dynamically exchange information or they can be statically configured5 2 C A220 AA17 1 FA3............7What Happens To Ethernet Frame and Packet AddressAs Data Frame Goes From Computer X To Computer YData PresentlyOn Network #MacDestinationAddressMacSourceAddressPacket DestAddressPacketSourceAddress1945ACDYXACDY : 5Y : 5 Y : 5Y : 5X : 1 X : 1 X : 1X : 1Routing - Intelligent delivery of data from point A to point B on an Internetwork.Router - Perform routing service.Typically uses shortest pathReference: “ Networking Unix” , by Douba , Sams Publishing Chapter 1,2.8Layered Internet Protocol Stack vs OSI Reference ModelApplicationTransportInternetPhysical PhysicalData LinkNetworkTransportSessionPresentationApplicationInternet Protocol Stack OSI Reference Model9Operation Of TCP/IP ConceptsHost A Host BAPPYAPPX APPXAPPYTCP TCPIPIPPhysical PhysicalGlobal NetworkAddressethernet 2Router JIPInterface1 ethernet 1Interface210 Operation of TCP/IP Concepts Continued:• IP : is implemented in all end systems and routers.• TCP: is implemented only in the end systems.• Each host on a subnetwork must have a unique global internet address which is used byIP for routing and delivery.• Each application within a host must have an address unique within host used by TCP. Addresses are know as ports.11Tracing Through This Example Network :Suppose: Port 1 Host A to Port 2 Host B.Host A sends message down to TCP.TCP hands down to IP.IP down to network access layer (ethernet) with instructions to send to Router J.At Router J ethernet packet header examined. Using IP header info know to send onto subnetwork 2.At Host B all headers removed.Reference: “ High speed networks TCP/IP and ATM design principles” By Stallings chapter 2, 10, 1112The TCP/IP Protocol ArchitectureCommunication Task Layers:•Physical layer - Physical interface between computer and the network (nature of signals, data rate).•Link Layer - Access to and sending data across a network for two end systems attached to the network→ Example: ethernet•Internet layer - Allows data to traverse multiple interconnected networks. Internet protocol (IP) isused at this layer to provide the routing function across multiple networks.•IP implemented in end systems (computers) and also in routers. (Everywhere)•Router is a processor that connects two networks with primary function to relay data from one network to the other on its route from the source to the destination.•Transport layer - Allows data to be exchanged reliably. Transmission control protocol (TCP) is the must commonly used protocol to do this. (End Stations)•Application layer - module to perform support for application like FTP, TELNET, etc.13SMTP FTPTFTP DNS SNMPAPPLICATIONTCP UDPIGMP ICMPARP RARPIPETHERNETTRANSPORTINTERNETPHYSICALANOTHER VIEWSMTP – Simple Mail Transfer ProtocolFTP- File Transfer ProtocolTFTP- Trivial File Transfer ProtocolDNS- Domain Name ServiceSNMP- Simple Network Management ProtocolTCP- Transmission Control ProtocolUDP- User Datagram ProtocolIGMP- Internet Group Management ProtocolICMP- Internet Control Message ProtocolIP- Internet ProtocolARP- Address Resolution ProtocolRARP Reverse Address Resolution Protocol14Protocol Data Units In TCP/IP ArchitectureAPPLICATION DATAIPHEADERETHERNETHEADERTCP/UDPHEADERAPPLICATION BYTESTREAMTCP SEGMENTOR UDP USER DATAGRAMIP DATAGRAMPHYSICAL LEVEL PACKET(For Example Ethernet Frame)15TCP Header :1531 ( 32 Bits)104Bit 020 BYTESSOURCE PORT DESTINATION PORTSEQUENCE NUMBERACKNOWLEDGEMENT NUMBER HEADER LENGTH UNUSEDFLAGSWINDOWCHECKSUM URGENT POINTEROPTIONS + PADDINGACKURGRSTSYNFINPSH16TCP Header Details:• Source Port (16 bits) – source TCP user.• Destination Port (16 bits) – destination TCP user.• Sequence Number (32 bits) – sequence number of the first data octet in thissegment except when SYN flag is set. If SYN is set this field is the initial sequencenumber (ISN).• Acknowledgement Number (32 bits) – a piggybacked acknowledgement, containsthe sequence number of the next data octet that the TCP entity expects to receive.• Header Length (4 bits) – number of 32 bit words in the header.• Unused (6 bits) – unused.17TCP Header Details Continued:• Flags (6 bits) – URG – urgent pointer field significant. ACK - acknowledgement field significant. * PSH – push function.

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