LAN Emulation, IP Over ATM and MPOAOverviewLAN Emulation: FeaturesLAN EmulationSlide 5Slide 6Protocol Layers (Cont)OperationOperation (Cont)ATM Virtual LANsIP Over ATMIP Over ATM: IssuesPacket Encapsulation [RFC1483]Encapsulation (Cont)Address ResolutionClassical IP Over ATMIP Multicast over ATMNext Hop Resolution ProtocolMultiprotocol Over ATMMPOA (Cont)SummaryHomeworkRaj JainThe Ohio State University1LAN Emulation, LAN Emulation, IP Over ATM IP Over ATM and MPOAand MPOARaj JainProfessor of Computer and Information SciencesThe Ohio State UniversityColumbus, OH 43210These slides are available athttp://www.cse.ohio-state.edu/~jain/cis777-00/Raj JainThe Ohio State University2OverviewOverviewLAN EmulationClassical IP over ATMNext Hop Resolution Protocol (NHRP)Multiprotocol over ATM(MPOA)Raj JainThe Ohio State University3LAN Emulation: Features LAN Emulation: Features One ATM LAN can be n virtual LANsLogical subnets interconnected via routersNeed drivers in hosts to support each LANOnly IEEE 802.3 and IEEE 802.5 frame formats supported. (FDDI can be easily done.)Doesn't allow passive monitoringNo token management (SMT), collisions, beacon frames. Allows larger frames.IEEE 802.3 or 802.5 FrameLE Header (2 Bytes)Raj JainThe Ohio State University4LAN EmulationLAN EmulationLAN Emulation driver replaces Ethernet driver and passes the networking layer packets to ATM driver.Each ATM host is assigned an Ethernet address.LAN Emulation Server translates Ethernet addresses to ATM addressesHosts set up a VC and exchange packetsAll software that runs on Ethernet can run on LANEATMIPEthernetIPLANEATMIPLANERaj JainThe Ohio State University5LAN EmulationLAN EmulationLAN Emulation Server ATM client BBridge2. Client sends messages on the VC1. Client gets recipient's address from LES and sets-up a VC.Broadcast/Unknown Server (BUS)Non-ATM client4. Messages for non-ATM clients are forwarded through bridges3. Messages for ATM clients are delivered directly.SwitchesRaj JainThe Ohio State University6Protocol LayersProtocol LayersApplica-tionsPhysicalLayerLANEmulationIP IPXNDIS ODIAAL5ATMPhyLayerATMLANEmulationPhyLayerAAL5ATMPhyLayerMediaAccessControlBridgingPhyLayerApplica-tionsPhysicalLayerMediaAccessControlIP IPXNDIS ODIATM HostATM SwitchATM-LAN BridgeLAN HostATMSwitchATMSwitchBridgeBridgeRaj JainThe Ohio State University7Protocol Layers (Cont)Protocol Layers (Cont)NDIS = Network Driver Interface SpecificationODI = Open Datalink InterfaceIPX = NetWare Internetworking ProtocolLAN Emulation Software:LAN Emulation Clients in each hostLAN Emulation ServersLAN Emulation Configuration server (LECS)LAN Emulation Server (LES)Broadcast and unknown server (BUS)Raj JainThe Ohio State University8OperationOperationInitialization: Client gets address of LAN Emulation Configuration Server (LECS) from its switch, uses well-known LECS address, or well known LECS PVCClient gets Server's address from LECSRegistration: Client sends a list of its MAC addresses to Server.Declares whether it wants ARP requests.Raj JainThe Ohio State University9Operation (Cont)Operation (Cont)Address Resolution: Client sends ARP request to Server. Unresolved requests sent to clients, bridges.Server, Clients, Bridges answer ARPClient setups a direct connectionBroadcast/Unknown Server (BUS): Forwards multicast traffic to all membersClients can also send unicast frames for unknown addressesRaj JainThe Ohio State University10ATM Virtual LANsATM Virtual LANsPhysical ViewLogical ViewATMSwitchATMSwitchLANEServer BLANEServer BLANEServer ALANEServer ARouterRouterA1A1B1B1A2A2B2B2RouterRouterA1A1A2A2B1B1B2B2Raj JainThe Ohio State University11IP Over ATMIP Over ATMIPATMRaj JainThe Ohio State University12IP Over ATM: IssuesIP Over ATM: IssuesHow many VC’s do we need for n protocols?Packet encapsulation [RFC1483] How to find ATM addresses from IP addressesAddress resolution [RFC1577]How to handle multicast? [MARS, RFC 2022]How do we go through n subnets on a large ATM network? [NHRP]Raj JainThe Ohio State University13Packet Encapsulation Packet Encapsulation [RFC1483][RFC1483]Question: Given an ATM link between two routers, how many VC’s should we setup?Answer 1: One VC per Layer 3 protocol. Null Encapsulation: No sharing. VC based multiplexing.IPIPXAppleTalkRouter RouterIPIPXAppleTalk IPIPXAppleTalkRaj JainThe Ohio State University14Encapsulation (Cont)Encapsulation (Cont)Answer 2: Share a VC using Logical Link Control (LLC) Subnetwork Access Protocol (SNAP). LLC Encapsulation Protocol Types: 0x0800 = IP, 0x0806 = ARP, 0x809B = AppleTalk, 0x8137 = IPXLLCIP IPX AppleTalkAAL5 TrailerLayer 3 PacketRaj JainThe Ohio State University15Address ResolutionAddress ResolutionIP address: 123.145.134.65ATM address: 47.0000 1 614 999 2345.00.00.AA....Issue: IP Address ATM Address translationAddress Resolution Protocol (ARP)Inverse ATM ARP: VC  IP Address Solution: ATMARP serversATMARPServerRaj JainThe Ohio State University16Classical IP Over ATMClassical IP Over ATMATM stations are divided in to Logical IP Subnets (LIS) ATMARP server translates IP addresses to ATM addresses.Each LIS has an ATMARP server for resolutionIP stations set up a direct VC with the destination or the router and exchange packets.RouterA1A2 B1B2ATMARPServerATMARPServerLIS 1 LIS 2Raj JainThe Ohio State University17IP Multicast over ATMIP Multicast over ATMMulticast Address Resolution Servers (MARS)Internet Group Multicast Protocol (IGMP)Multicast group members send IGMP join/leave messages to MARS Hosts wishing to send a multicast send a resolution request to MARSMARS returns the list of addressesMARS distributes membership update information to all cluster membersRaj JainThe Ohio State University18Next Hop Resolution ProtocolNext Hop Resolution ProtocolRouters assemble packets  SlowNHRP servers can provide ATM address for the edge device to any IP host Can avoid routers if both source and destination are on the same ATM network.ATM NetworkHostHostNHRPServerNHRPServerNHRPServerNHRPServerBridgeRaj JainThe Ohio State University19Multiprotocol Over ATMMultiprotocol Over ATMMPOA= LANE + “NHRP+”Extension of LANEUses NHRP to find the shortcut to the next hopNo routing (reassembly) in the ATM networkNext Hop Resolution ProtocolLAN EmulationMultiprotocol Over