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7. LAN EMULATION (LANE)

Goal : How can existing Ethernet and Token Ring be integrated with ATM? Need : All LAN-based network applications assume that LAN is capable of Delivery of packets to individual destinations according to a unique MAC address, without the necessity for any kind of connection set-up

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7. LAN EMULATION (LANE)

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  1. Goal: How can existing Ethernet and Token Ring be integrated with ATM? Need: All LAN-based network applications assume that LAN is capable of Delivery of packets to individual destinations according to a unique MAC address, without the necessity for any kind of connection set-up to that address. Delivery of broadcast packets to all stations on the LAN or a specified group of stations, by means of a special kind of MAC destination address indicating broadcast or multicast. 7. LAN EMULATION (LANE) 1

  2. ATM World Not offering these services. ATM delivers data on VCCs which need to be set up between source and destination ATM (Connection-Oriented) LANs (Connectionless) LAN EMULATION: Masks the complexities of ATM connection set-up from applications that expect connectionless data delivery.

  3. ATM Network Physical LAN Emulated LAN PHYSICAL and EMULATED LANs

  4. ATM Workstation ATM PC ATM Switch ATM Switch Token Ring ATM Switch Bridge Ethernet • LAN Emulation Services • Configuration • Address Resolution • Broadcast Ethernet

  5. Existing Application Software Existing Application Software IP IPX NDIS ODI IP IPX NDIS ODI 802.1DBridging LAN Emulation LANE AAL 5 MAC AAL 5 MAC ATM ATM PHY PHY PHY PHY PROTOCOL LAYERS ATM Host with LANE NIC LAN Host ATM SWITCH Bridge (Network Driver Interface Specification or Open Data Link Interface)* Layer 2 LAN Switch ATM Switch ATM ATM PHY PHY * Purpose: Fooling the application software into believing that is talking to a standard network adapter driver. IPX: NetWare Internetworking Protocol

  6. LES LEC BUS LEC LECS LEC LANE COMPONENTS An Emulated LAN consists of multiple LAN Emulation Clients (LECs) and LAN Emulation Services. From Single Emulated LAN perspective: LANE SERVICES Legacy LAN LAN Emulation Server LUNI Bridge Legacy LAN Broadcast and Unknown Server LUNI Bridge LAN Emulation Configuration Server LUNI LUNI: LAN Emulation User to Network Interface

  7. UNI LES 1 ATM Host LNNI ATM Network LES n Layer 2 Switch BUS 1 LNNI LUNI Router BUS n LANE Servers LANE Clients LECS Note: The Phase 1 LANE spec only specifies the LUNI interface LANE PROTOCOL INTERFACES

  8. LEC: (LAN EMULATION CLIENTS)(e.g., ATM Host, Layer 2 Switch, Router) • * Any end-station or bridge that implements LAN Emulation. • * A process that resides in end-station or a bridge providing entry • point to ELAN. • * Entity in an end-system that performs DATA FORWARDING, ADDRESS • RESOLUTION, and other control functions for a single end-system within a • single ELAN. • * LEC also provides a standard LAN interface to any higher layer • entity that interfaces to the LEC. • * An ATM NIC or LAN switch interface to an ELAN supports a single • LEC for each ELAN to which they are connected. • * An end-system that connects to multiple ELANs (maybe over the • same UNI) will have one LEC per ELAN.

  9. LEC: (Ctd) * Each LEC is identified by a unique ATM address and is associated with one or more MAC addresses reachable through that ATM address. * In case of ATM NIC  LEC maybe associated with only a single MAC address. * In case of LAN Switch  LEC is associated with all the MAC addresses reachable through the ports of that LAN switch which are assigned to a particular ELAN. * In the latter case  set of addresses may change, i.e., MAC nodes come up and down. PROXY concept can be used!! * Ethernet-to-Token Ring Interconnection: Two Different ELANs which must be interconnected through an ATM switch which acts as a client on each ELAN.

  10. LES * Implements the control function for a particular ELAN. * Each LES is identified by a unique ATM address. * Registering and resolving MAC addresses into ATM addresses; * It also responds to LEC queries. * Each emulated LAN has ONLY one LES. * Belonging to a particular ELAN means to have a control relationship with that ELAN’s particular LES. * LES acts as a CLEARING HOUSE for ADDRESS RESOLUTION. Bottomline:LES provides ADDRESS RESOLUTION MECHANISM for resolving MAC Addresses. Also registration of an LEC, Forwarding Address Resolution Requests, Managing LEC Address Registration Information.

  11. BUS  * is a MULTICAST SERVER. * Used to flood unknown destination address traffic and forward multicast and broadcast traffic to clients within a particular ELAN. * Each LEC is associated with only a single BUS per ELAN, but there may be multiple BUSs within a particular ELAN. * BUS to which a LEC connects is identified by a unique ATM address. * In the LES, this is associated with the broadcast (“all ones”) and this mapping is normally configured into the LES.

  12. LECS * Assigns individual LECs to different (particular) ELANs. * It does this by providing each LEC with the ATM address of the LES for the emulated LAN assigned to it. * There is logically one LECS per network and this serves all ELANs withinthat domain. REMARK: * System Architecture allows these components to be distributed among multiple physical devices. * These components are connected to each other by multiple Virtual Channels (VCs).

  13. LAN Emulation Client LAN Emulation Client LAN Emulation Client LANE Configuration Server Token Ring LAN Emulation Server Broadcast/Unknown Server LAN Emulation Client LAN Emulation Client LOCATION of LAN EMULATION COMPONENTS ATM Concentrator ATM End Stations ATM Switch TR Hub Token Ring Switch Full Duplex Token Ring Ethernet Hub Router

  14. LOCATION OF LANE COMPONENTS • LEC • In any PC or workstations directly connected to ATM • network. Reside in devices such as Bridges, LAN Switches, • Routers… • As a software (on an ATM card!) • Operates underneath a standard LAN Driver interface, • ODI (Novell Open Data Link Interface) or • NDIS (Microsoft Network Data Link Interface Specification) • LEC is the integral part of driver software for ATM adapter • card.

  15. LES, BUS, LECS processes need to reside on hosts that are easily accessed by all LECs. Located on the same host or different hosts. In Actual World: On any workstation attached to the ATM network (dedicated PC or WS) e.g., implemented as Netware Loadable Modules (NLMs) and run on an existing or dedicated Netware server. Alternative LES, BUS, LECS can be on a processor integrated with an ATM switch. 10

  16. Each LEC is an entity within an ATM end system, acting on its own behalf and on the behalf of traditional LAN users identified by MAC addresses. LEC is a software process running on any ATM connected LAN switch, router, PC, or workstation. LES-1 BUS-N BUS-1 LES-N LAN (LEC) Emulation Servers LAN (LEC) Emulation Clients ATM NETWORK ATM ATM Host ATM LNNI ATM Layer 2 Switch Router LECS LUNI LNNI 13

  17. Configuration Direct VCC LANE Client LECS Control Direct VCC LANE Client LES LANE CONTROL CONNECTIONS CONTROL TRAFFIC: Control VCCs carrying control messages between a LEC & either the LECS or the LES. • Configuration Direct VCC. This is a bidirectional point-to-point VCC that is established between the LEC and the LECS as part of the LECS Connect phase. It is used by the LEC to obtain configuration information such as the ATM address of the LES. • Control Direct VCC. This is a bidirectional point-to-point VCC that is established between the LEC and the LES for the purpose of sending control information. Set up by each LEC when joined the ELAN.

  18. Control Distribute VCC LANE Client LES LANE Client LANE CONTROL CONNECTIONS • Control Distribute VCC. This is a unidirectional VCC set up from the LES back to the LEC. This is either point-to-point (LES  LANE Client (LEC)) or typically point-to-multipoint (LES  many clients (LECs)). Control Distribute VCC

  19. LANE Server (LES) Control Direct VCC Control Direct VCC LANE Client (LEC) LANE Client (LEC) Control Distribute VCC LAN Switch ATM Host Configuration Direct VCC Configuration Direct VCC LANE Configuration Server (LECS) LANE Control Connections (Overview)

  20. Data Direct VCC LANE Client LANE Client LANE DATA CONNECTIONS Data VCCs connect the LECs to each other and to the BUS. They carry encapsulated Ethernet or Token Ring frames. DATA TRAFFIC: • Data Direct VCC: This is a bidirectional point-to-point VCC that is established between two LECs that want to exchange data. Two LECs will use the same data direct VCC to carry all packets between them => to save bandwidth & set up overheads! Remark: LANE supports existing LANs which do not support QoS; => Data Direct Connections will typically be UBR or ABR connections.

  21. Multicast Send VCC LANE Client BUS LANE DATA CONNECTIONS (Ctd) • Multicast Send VCC: This is a bidirectional point-to-point VCC set up by the LECs to the BUS. This VCC is used for sending multicast data frames to the BUS, as well as initial unicast data frames whose ATM address is not known to the source LEC. A LEC may receive data frames over this VCC.

  22. Multicast Forward VCC LANE CLIENT (LEC) BUS • MULTICAST FORWARD VCC • This is a unidirectional VCC set up to the LEC from the BUS. • This is typically a point-to-multipoint connection with each • LEC as a leaf. *This VCC is used for forwarding multicast data frames to LECs.

  23. Broadcast and Unknown Server (BUS) Multicast Send VCC Multicast Send VCC Multicast Forward VCC LANE Client (LEC) LANE Client (LEC) Data Direct VCC LAN Switch ATM Host LANE DATA CONNECTIONS (Overview)

  24. LANE FUNCTIONS • INITIALIZATION. • LEC obtains the ATM address of the LES and establishes • connections with the LES and BUS; • Joining or Leaving a given ELAN. • (Connect Phase, Configuration Phase, Join Phase, • BUS Connect Phase) • REGISTRATION. • LEC registers its MAC address(es) with the LES. • (in case of Token Ring, a list of source route descriptors • that LEC represents for source route bridging)

  25. LANE FUNCTIONS • ADDRESS RESOLUTION. • Enables a source LEC to obtain the ATM address of the • destination LEC for the purpose of establishing a • Data Direct VCC. • DATA TRANSFER. • Determine which VCC to send data on and then encapsulate • in AAL5 frames.

  26. I. INITIALIZATION • Connection Phase(LEC connection to LECS) • Configuration Phase • Join Phase • BUS Connect Phase

  27. I. INITIALIZATION 1. Connection Phase (LEC to LECS) • Upon initialization (such as power-up), the LEC must first obtain its own ATM address (through Address Registration) from LECS: • To do this, LEC must first find the LOCATION (ATM address) of the LECS. THREE METHODS: • Use SNMP ILMI commands from the adjacent switch and obtain the LECS ATM address OR • Use the well-known ATM address of the LECS assigned by the ATM Forum OR • Use the well-known PVC (VPI = 0; VCI = 17) to connect to the LECS.

  28. LE_CONFIGURE_REQUEST LEC LECS (Configuration Direct VCC) LE_CONFIGURE_RESPONSE LEC LECS (Configuration Direct VCC) 2. Configuration Phase • After finding the location of the LECS, the LEC will establish the “Configuration Direct VCC” to the LECS. Figure shows the “CONTROL FRAMES” that flow between the LEC and LECS, OVER the “Configuration Direct VCC” and some important operational variables that are carried. Information:C1 : LEC ATM ADDRESS Information: C2 : LAN Type (Ethernet or Token Ring) C3 : Max. Frame Size C5 : ELAN Name C9 : Target ATM Address of the LES

  29. LE_JOIN_REQUEST LEC LES (Control Direct VCC) 3. Join Phase • LEC establishes a “Control Direct VCC” to the LES and attempts to join as a member of the ELAN. Information: C1 : LEC ATM Address C2 : LAN Type C3 : Max. Frame Size C4 : Proxy LEC (any other MAC address it is proxying (Optional!!!) C5 : ELAN Name C6 : Local Unicast MAC Address (Optional) The unique MAC address associated with the LEC. This enables the LEC to register this address and its associated ATM address, C1 variable with the LES.

  30. LEC LE_JOIN_RESPONSE LES CONTROL DISTRIBUTE VCC • Information: C2: LAN Type • C3: Max Frame Size • C5: ELAN Name • C14: LECID (unique LEC Identifier, assigned by LES for • every LEC that joins the ELAN.) • During JOIN process, LES issues to the LEC a 2-byte identity code (LECID) • that is unique for this LEC. • This value will be used as LAN Emulation header to be appended to all • Ethernet or Token Ring frames before they are segmented into cells. • REMARK: The LEC will exchange information with the LES so that the LES can • maintain a table of details of all LECs currently active on the ELAN. • REMARK:LES has the option of responding to the LEC on Control Direct • connection, or via a unidirectional point-to-multipoint Control • Distribute connection to all LECs. REMARK:

  31. 1 LEC sets up Control Direct VCC 2 LEC sends LE_JOIN_REQUEST 3 LES optionally sets up Control Distribute VCC 4 LES sends LE_JOIN_RESPONSE Connecting to the LES and Joining the Emulated LAN LAN Emulation Server (LES) LAN Emulation Client (LEC) ToOther LECs 14

  32. 4. BUS (Broadcast and Unknown Server) CONNECT PHASE (How to Handle Broadcast and Multicast?) • When LEC registers with LES; LEC locates the BUS by sending an LE_ARP_REQUEST to the LES, in order to find the ATM address that corresponds to the broadcast MAC address (hex: F^{12}). LES responds to this LE_ARP request with the ATM address of the BUS. • LEC uses this to establish a “MULTICAST SEND VCC” to the BUS. • BUS sets up a return path to the LEC, then automatically adds the LEC to an existing point-to-multipoint “MULTICAST FORWARD VCC” or BUS may establish a point-to-point VCC to the LEC. • Once the BUS connect phase is complete, then LEC can send broadcast andmulticast frames to BUS. • BUS sends then broadcast and multicast frames to all LECs that are registered with it (including the sender LEC) USING THE MULTICAST FORWARD VCC. • Once the BUS Connect Phase is complete, LEC is initialized and data transfer can begin.

  33. LANE Client LECS LES BUS Configuration Direct VCC Control Direct VCC Control Distribute VCC Multicast Send VCC Multicast Forward VCC Control and Data VCCs Established During the Initialization Phase

  34. LEC LE_REGISTER_REQUEST LES CONTROL DIRECT VCC II. ADRESS REGISTRATION Each LEC must register the additional MAC addresses it represents with the LES that were not registered during the JOIN phase. LES builds a table of ATM Address-MAC address pairs that it uses to respond to Address Resolution requests made later by another LEC. Information:C1: LEC ATM address C6: Local Unicast MAC address C8: Route Descriptor (If SRB) C14: LECID

  35. LES LEC LE_REGISTER RESPONSE “CONTROL DIRECT VCC” or “CONTROL DISTRIBUTE VCC” • Information: • STATUS • C14 : LECID LES LEC LE_UNREGISTER_REQUEST “CONTROL DIRECT VCC” • Information: • C1 : LEC ATM ADDRESS • C6 : LOCAL UNICAST MAC ADDRESS • C8 : Route Descriptor (If SRB) • C14 : LECID

  36. LES LEC LE_UNREGISTER RESPONSE “CONTROL DIRECT VCC” or “CONTROL DISTRIBUTE VCC” • Information : • STATUS • C14 : LECID

  37. III. ADDRESS RESOLUTION (requires LES and a protocol LE_ARP (LAN Emulation Resolution Protocol_ for communicating with LES) Resolved MAC Addresses on ATM Port MAC Map Address to VCI 73 6 88 3 69 6 14 8 Learned MAC Addresses on Ethernet Port 51 26 ATM 69 26 VCI=6 73 VCI=8 Ethernet-ATM Bridge 51 Ethernet-ATM Bridge VCI=3 14 Emulated MAC Address 88 3

  38. Send Data Receive Data Destination Address Source Address; Data Destination Address Source Address; Data DA-VCC Mapping Table Look up VCC to match this DA Remove LE Header and assemble frame Match Found? Resolve address and set up VCC Add 2Byte LE Header and Segment Frame Call Setup Send Data Call Connect Receive Data Destination Address VCI Data VCI Data VCI ADRESS RESOLUTION PROCESS LAN Application Yes No ATM Network

  39. Address Resolution (Ctd) • Used by source LEC to associate a destination MAC address with the matching ATM address. • Purpose: Provide to the source LEC the ATM address of the destination LEC. • The destination LEC could be a workstation or a bridge (transparent or source-routing) which is providing a proxy LEC function for the legacy MAC devices behind it.* • When the source LEC has a frame to transmit to a destination MAC address and it does not already have a Data Direct VCC open nor does it have an entry in its own MAC-to-ATM address cache (C16 variable), it sends an LE_ARP_REQUEST over the Control Direct VCC to the LES. • * (LEC needs to know the ATM address of another LEC that it knows the MAC address for, it sends a request to LES using LE-ARP).

  40. Address Resolution (Ctd) • PROXY: If LEC is a transparent bridge  it represents hundreds of MAC addresses. This list may change over time. • Stations in Ethernet come and go. This type of LEC is not permitted to register its MAC addresses with LES. • Too much overhead to maintain tables. • Instead  LEC registers as a “PROXY” and LES must forward all LE_ARP requests to it through “Control Direct VCCs” so that it can respond directly to the LEC that is requesting.

  41. Address Resolution (Ctd.) • How the LES behaves depends on whether the • MAC destination address is registered with the LES. • The LES can respond to the address resolution • request in the following manner: • If the LE_ARP_REQUEST contains the broadcast • MAC address (all ones) as the destination MAC • address, then the LES will respond with the ATM • address of the BUS in the LE_ARP_RESPONSE. • This is performed during the BUS connect phase • of the LEC initialization process.

  42. Address Resolution (Ctd.) • If the destination MAC address is known to the LES (registered), then the LES will return the destination ATM address to the source LEC in an LE_ARP_RESPONSE. • This control frame is sent over the Control Direct VCC or Control Distribute VCC. • Forwarding it over the latter will enable other LECs to update their LE_ARP caches (C16) but will incur some network and LEC processing overhead. • If the destination MAC address is unknown to the LES, then the LES will forward the LE_ARP_REQUEST to other LECs over the Control Direct VCC or Control Distribute VCC. • This will typically be the case if the destination MAC address belongs to a workstation attached to a legacy LAN on the other side of the bridge.

  43. LANE Client LES LE_ARP_REQUEST (LECID, Source MAC Address, Source ATM Address, Destination MAC Address, …) Control Direct VCC LE_ARP_RESPONSE (LECID, Source MAC Address, Source ATM Address, Destination MAC Address, Destination ATM Address, …) Control Distribute VCC or Control Direct VCC EXAMPLE (REGISTERED ADDRESS SOLUTION) LANE Client #1 wants to send a frame to another LEC (not shown) that has registered its MAC address with the LES. It will then send an LE_ARP_REQUEST over the Control Direct VCC to the LES. The LES will respond with an LE_ARP_RESPONSE, which contains the ATM address of the destination LEC. The source LEC installs the new MAC-to-ATM address mapping in its own LE_ARP cache (C16) and then sets up a Data Direct VCC to the destination LEC.

  44. Address Resolution for Unregistered MAC Address • Only LECs that are directly attached to the ATM network are allowed to register their own MAC addresses. • Devices such as ATM LAN bridges are allowed to register only their own MAC addresses, or if they are token-ring source-route bridges, then their route descriptors. • For example, an Ethernet-to-ATM transparent bridge will not register with the LES any of the MAC addresses of Ethernet-attached workstations that it has learned about. • Instead, it will respond to LE_ARP_REQUESTS that have been forwarded to it from the server with its own ATM address, the MAC address of the actual Ethernet-attached workstation, and a flag indicating that the MAC address is “remote” from the LEC that responded.

  45. Address Resolution for Unregistered MAC Address • If LEC fails to resolve a MAC address by means of LE_ARP_REQUEST, it may forward the frame to BUS using the “Multicast Send VCC”. • BUS will treat this frame as if it were a broadcast or multicast, and will forward it to all registered LECs. • If these LECs are transparent bridges, their bridging logic dictates that such frames should be forwarded on all attached LAN segments. • When the target station replies, the bridge on that segment will learn of its whereabouts, and the next time a LEC attempts an address resolution to this MAC address, the bridge will be able to respond.

  46. LES LANE Client2 LANE Client1 LE_ARP_REQUEST(LECID, Source MAC Address, Source ATM address, Destination MAC Address, …) Control Direct VCC LE_ARP_REQUEST LE_ARP_REQUEST Control Distribute VCC LE_ARP_RESPONSE(LECID, Source MAC Address, Source ATM Address, Destination MAC Address, Destination ATM Address, Remote Address Flag, …) Control Direct VCC LE_ARP_RESPONSE LE_ARP_RESPONSE Control Distribute VCC Example Unregistered Address Solution

  47. LANE Client #1 wishes to transmit a frame to a destination MAC Address that is unregistered. • It is in fact an Ethernet workstation that is attached to LANE Client #2. • LANE Client #2 is actually an Ethernet-to-ATM bridge. • So after LANE Client #1 sends the first frame to the BUS which will in turn forward it out its Multicast Forward VCC to all LECs on the ELAN, it sends an LE_ARP_REQUEST to the LES. • Because it is unregistered the LES forwards the request on its Control Distribute VCC to all LECs on the ELAN. • LANE Client #2 receives the request, checks its own MAC address cache (it is a transparent learning bridge) and determines that it contains a match for the destination MAC-address value in the request. • LANE Client #2 then issues an LE_ARP_RESPONSE that contains the destination MAC address (C27), its own ATM address, and sets a flag to indicate that the address is remote. • The response is forwarded back to LANE Client #1 who caches the information and now can set up a Data Direct VCC.

  48. LE_ARP_REQUEST LEC LES “Control Direct VCC” Address Resolution Control Frames • Information: • Source MAC Address • Source ATM Address • Destination MAC Address • C14 LECID

  49. !!!!! LE_ARP_RESPONSE LEC LES “Control Direct VCC” or “Control Distribute VCC” • Information: • Source MAC Address • Source ATM Address • Destination MAC Address • Destination ATM Address • Remote Flag • C14 LECID

  50. LE_NARP_REQUEST LEC LES “Control Direct VCC” • Information: • MAC Address that is no longer valid • Source ATM Address • Destination ATM Address(previously representing the invalid MAC Address) • C14: LECID Remark: Used when LEC (typically a proxy LEC) wishes to invalidate an existing MAC-to-ATM address mapping.

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