Raj JainThe Ohio State University1LAN Emulation,LAN Emulation,IP Over ATMIP Over ATMand MPOAand MPOARaj JainProfessor of Computer and Information SciencesThe Ohio State UniversityColumbus, OH 43210These slides are available athttp://www.cis.ohio-state.edu/~jain/cis777-99/Raj JainThe Ohio State University2OverviewOverviewq LAN Emulationq Classical IP over ATMq Next Hop Resolution Protocol (NHRP)q Multiprotocol over ATM(MPOA)Raj JainThe Ohio State University3LAN Emulation: FeaturesLAN Emulation: Featuresq One ATM LAN can be n virtual LANsq Logical subnets interconnected via routersq Need drivers in hosts to support each LANq Only IEEE 802.3 and IEEE 802.5 frame formatssupported. (FDDI can be easily done.)q Doesn't allow passive monitoringq No token management (SMT), collisions, beaconframes.q Allows larger frames.IEEE 802.3 or 802.5 FrameLE Header (2 Bytes)Raj JainThe Ohio State University4LAN EmulationLAN Emulationq LAN Emulation driver replaces Ethernet driver andpasses the networking layer packets to ATM driver.q Each ATM host is assigned an Ethernet address.q LAN Emulation Server translates Ethernet addressesto ATM addressesq Hosts set up a VC and exchange packetsq All software that runs of Ethernet can run on LANEATMIPEthernetIPLANEATMIPLANERaj JainThe Ohio State University5LAN EmulationLAN EmulationLAN Emulation ServerATM client BBridge2. Client sendsmessages onthe VC1. Client getsrecipient'saddress fromLES and sets-up a VC.Broadcast/Unknown Server (BUS)Non-ATM client4. Messages for non-ATMclients are forwardedthrough bridges3. Messages forATM clients aredelivered directly.SwitchesRaj JainThe Ohio State University6Protocol LayersProtocol LayersApplica-tionsPhysicalLayerLANEmulationIP IPXNDIS ODIAAL5ATMPhyLayerATMLANEmulationPhyLayerAAL5ATMPhyLayerMediaAccessControlBridgingPhyLayerApplica-tionsPhysicalLayerMediaAccessControlIP IPXNDIS ODIATM HostATM SwitchATM-LAN BridgeLAN HostATMSwitchBridgeRaj JainThe Ohio State University7Protocol Layers (Cont)Protocol Layers (Cont)q NDIS = Network Driver InterfaceSpecificationq ODI = Open Datalink Interfaceq IPX = NetWare Internetworking Protocolq LAN Emulation Software:q LAN Emulation Clients in each hostq LAN Emulation Serversq LAN Emulation Configuration server (LECS)q LAN Emulation Server (LES)q Broadcast and unknown server (BUS)Raj JainThe Ohio State University8OperationOperationq Initialization:m Client gets address of LAN EmulationConfiguration Server (LECS) from its switch, useswell-known LECS address, or well known LECSPVCm Client gets Server's address from LECSq Registration:m Client sends a list of its MAC addresses to Server.m Declares whether it wants ARP requests.Raj JainThe Ohio State University9Operation (Cont)Operation (Cont)q Address Resolution:m Client sends ARP request to Server.m Unresolved requests sent to clients, bridges.m Server, Clients, Bridges answer ARPm Client setups a direct connectionq Broadcast/Unknown Server (BUS):m Forwards multicast traffic to all membersm Clients can also send unicast frames for unknownaddressesRaj JainThe Ohio State University10ATM Virtual LANsATM Virtual LANsq Physical Viewq Logical ViewATMSwitchATMSwitchLANEServer BLANEServer BLANEServer ALANEServer ARouterRouterA1A1B1B1A2A2B2B2RouterRouterA1A1A2A2B1B1B2B2Raj JainThe Ohio State University11IP Over ATMIP Over ATMIPATMRaj JainThe Ohio State University12IP Over ATM: IssuesIP Over ATM: Issuesq How many VC’s do we need for n protocols?m Packet encapsulation [RFC1483]q How to find ATM addresses from IP addressesm Address resolution [RFC1577]q How to handle multicast? [MARS, RFC 2022]q How do we go through n subnets on a large ATMnetwork? [NHRP]Raj JainThe Ohio State University13Packet EncapsulationPacket Encapsulation[RFC1483][RFC1483]q Question: Given an ATM link between two routers,how many VC’s should we setup?q Answer 1: One VC per Layer 3 protocol. NullEncapsulation: No sharing. VC based multiplexing.IPIPXAppleTalkRouter RouterIPIPXAppleTalk IPIPXAppleTalkRaj JainThe Ohio State University14Encapsulation (Cont)Encapsulation (Cont)q Answer 2: Share a VC using Logical Link Control(LLC) Subnetwork Access Protocol (SNAP). LLCEncapsulationq Protocol Types: 0x0800 = IP, 0x0806 = ARP,0x809B = AppleTalk, 0x8137 = IPXLLCIP IPX AppleTalkAAL5 TrailerLayer 3 PacketRaj JainThe Ohio State University15Address ResolutionAddress Resolutionq IP address: 123.145.134.65 ATM address: 47.0000 1 614 999 2345.00.00.AA....q Issue: IP Address ⇔ ATM Address translationm Address Resolution Protocol (ARP)m Inverse ATM ARP: VC ⇒ IP Addressq Solution: ATMARP serversATMARPServerRaj JainThe Ohio State University16Classical IP Over ATMClassical IP Over ATMq ATM stations are divided in to Logical IP Subnets(LIS)q ATMARP server translates IP addresses to ATMaddresses.q Each LIS has an ATMARP server for resolutionq IP stations set up a direct VC with the destination orthe router and exchange packets.RouterA1A2 B1B2ATMARPServerATMARPServerLIS 1 LIS 2Raj JainThe Ohio State University17IP Multicast over ATMIP Multicast over ATMq Multicast Address Resolution Servers(MARS)q Internet Group Multicast Protocol (IGMP)q Multicast group members send IGMP join/leave messages to MARSq Hosts wishing to send a multicast send aresolution request to MARSq MARS returns the list of addressesq MARS distributes membership update informationto all cluster membersRaj JainThe Ohio State University18Next Hop Resolution ProtocolNext Hop Resolution Protocolq Routers assemble packets ⇒ Slowq NHRP servers can provide ATM address for the edgedevice to any IP hostq Can avoid routers if both source and destination areon the same ATM network.ATM NetworkHostHostNHRPServerNHRPServerNHRPServerNHRPServerBridgeRaj JainThe Ohio State University19Multiprotocol Over ATMMultiprotocol Over ATMq MPOA= LANE + “NHRP+”q Extension of LANEq Uses NHRP to find the shortcut to the next hopq No routing (reassembly) in the ATM networkNext Hop Resolution ProtocolLAN EmulationMultiprotocol Over ATMRoutingBridgingMulticast Address Resolution ServerRaj JainThe Ohio State University20MPOA (Cont)MPOA (Cont)q LANE operates at layer 2q RFC 1577 operates at layer 3q MPOA operates at both layer 2 and layer 3 ⇒ MPOA can handle non-routable as well asroutable protocolsq Layer 3 protocol runs directly over ATM⇒ Can use ATM QoSq MPOA uses LANE for its layer 2 forwardingRNHS NHSH HELAN1 ELAN2Raj JainThe Ohio State University21SummarySummaryq LANE allows current applications to run on ATMq Classical IP allows ARP using