Internetworking April 17, 2003A Client-Server TransactionHardware Org of a Network HostComputer NetworksLowest Level: Ethernet SegmentNext Level: Bridged Ethernet SegmentConceptual View of LANsNext Level: internetsThe Notion of an internet ProtocolWhat Does an internet Protocol Do?Transferring Data Over an internetOther IssuesGlobal IP InternetHardware and Software Org of an Internet ApplicationBasic Internet ComponentsThe Internet Circa 1993NSFNET Internet BackboneCurrent NAP-Based Internet ArchitectureInternet Connection HierarchyNetwork Access Points (NAPs)PowerPoint PresentationA Programmer’s View of the Internet1. IP AddressesDotted Decimal Notation2. Internet Domain NamesDomain Naming System (DNS)Properties of DNS Host EntriesA Program That Queries DNSQuerying DNS from the Command Line3. Internet ConnectionsPutting it all Together: Anatomy of an Internet ConnectionNext TimeInternetworkingApril 17, 2003InternetworkingApril 17, 2003TopicsTopicsClient-server programming modelNetworksInternetworksGlobal IP InternetIP addressesDomain namesConnections15-213“The course that gives CMU its Zip!”– 2 –15-213, S’03A Client-Server TransactionA Client-Server TransactionClientprocessServerprocess1. Client sends request2. Server handlesrequest3. Server sends response4. Client handlesresponseResourceEvery network application is based on the client-server Every network application is based on the client-server model:model:A server process and one or more client processesServer manages some resource.Server provides service by manipulating resource for clients.Note: clients and servers are processes running on hosts (can be the same or different hosts).– 3 –15-213, S’03Hardware Org of a Network HostHardware Org of a Network HostmainmemoryI/O bridgeMIALUregister fileCPU chipsystem bus memory busdisk controllergraphicsadapterUSBcontrollermouse keyboard monitordiskI/O busExpansion slotsnetworkadapternetwork– 4 –15-213, S’03Computer NetworksComputer NetworksA network is a hierarchical system of boxes and wires A network is a hierarchical system of boxes and wires organized by geographical proximityorganized by geographical proximityLAN (local area network) spans a building or campus.Ethernet is most prominent example.WAN (wide-area network) spans country or world.Typically high-speed point-to-point phone lines.An An internetworkinternetwork ( (internetinternet) ) is an interconnected set of is an interconnected set of networks.networks.The Gobal IP Internet (uppercase “I”) is the most famous example of an internet (lowercase “i”)Let’s see how we would build an internet from the Let’s see how we would build an internet from the ground up.ground up.– 5 –15-213, S’03Lowest Level: Ethernet SegmentLowest Level: Ethernet SegmentEthernet segment consists of a collection o f Ethernet segment consists of a collection o f hostshosts connected by wires (twisted pairs) to a connected by wires (twisted pairs) to a hubhub. . Spans room or floor in a building.Spans room or floor in a building.OperationOperationEach Ethernet adapter has a unique 48-bit address.Hosts send bits to any other host in chunks called frames.Hub slavishly copies each bit from each port to every other port.Every host sees every bit.hosthost hosthub100 Mb/s100 Mb/sports– 6 –15-213, S’03Next Level: Bridged Ethernet SegmentNext Level: Bridged Ethernet SegmentSpans building or campus.Spans building or campus.Bridges cleverly learn which hosts are reachable from which ports and then selectively Bridges cleverly learn which hosts are reachable from which ports and then selectively copy frames from port to port.copy frames from port to port.hosthost host host hosthub hubbridge100 Mb/s100 Mb/shosthosthub100 Mb/s 100 Mb/s1 Gb/shosthost hostbridgehosthosthubA BCXY– 7 –15-213, S’03Conceptual View of LANsConceptual View of LANsFor simplicity, hubs, bridges, and wires are often shown as a collection of hosts attached to a single wire:For simplicity, hubs, bridges, and wires are often shown as a collection of hosts attached to a single wire:hosthost host...– 8 –15-213, S’03Next Level: internetsNext Level: internetsMultiple incompatible LANs can be physically connected by specialized Multiple incompatible LANs can be physically connected by specialized computers called computers called routersrouters..The connected networks are called an The connected networks are called an internetinternet..hosthost hostLAN 1...hosthost hostLAN 2...router router routerWAN WANLAN 1 and LAN 2 might be completely different, totally incompatible LANs (e.g., Ethernet and ATM)– 9 –15-213, S’03The Notion of an internet ProtocolThe Notion of an internet ProtocolHow is it possible to send bits across incompatible How is it possible to send bits across incompatible LANs and WANs?LANs and WANs?Solution: Solution: protocol softwareprotocol software running on each host and running on each host and router smoothes out the differences between the router smoothes out the differences between the different networks.different networks.Implements an Implements an internet protocolinternet protocol (i.e., set of rules) that (i.e., set of rules) that governs how hosts and routers should cooperate governs how hosts and routers should cooperate when they transfer data from network to network.when they transfer data from network to network.•TCP/IP is the protocol for the global IP Internet.– 10 –15-213, S’03What Does an internet Protocol Do?What Does an internet Protocol Do?1. Provides a naming scheme1. Provides a naming schemeAn internet protocol defines a uniform format for host addresses.Each host (and router) is assigned at least one of these internet addresses that uniquely identifies it.2. Provides a delivery mechanism2. Provides a delivery mechanismAn internet protocol defines a standard transfer unit (packet)Packet consists of header and payloadHeader: contains info such as packet size, source and destination addresses.Payload: contains data bits sent from source host.– 11 –15-213, S’03Transferring Data Over an internetTransferring Data Over an internetprotocolsoftwareclientLAN1adapterHost Adatadata PH FH1data PHdata PH FH2LAN1LAN2datadata PHFH1data PH FH2(1)(2)(3)(4)(5)(6)(7)(8)internet packetLAN2 frameprotocolsoftwareLAN1adapterLAN2adapterRouterFH1LAN1 framedata PH FH2protocolsoftwareserverLAN2adapterHost B– 12 –15-213,
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