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ATM Traffic Management and LAN Emulation

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23 diapositives · 327 Views · Sep 10, 2014

Understand ATM Classes of Service, Traffic Management, LAN Emulation concepts & protocols by Raj Jain, Prof. at Ohio State Univ. Explore ABR, LANE v2.0, Traffic Mgmt functions, & Classes of Service for optimal network performance.

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ATM Traffic Management and LAN Emulation
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  1. ATM Traffic Management and LAN Emulation Raj JainProfessor of Computer and Information SciencesThe Ohio State Universityhttp://www.cse.ohio-state.edu/~jain/cis788-97/

  2. Overview • ATM Classes of Service • ATM Traffic Management • Available Bit Rate (ABR) • LAN Emulation (LANE) • LANE V2.0.

  3. Dime Sale One Megabit memory, One Megabyte disk, One Mbps link, One MIP processor, 10 cents each.....

  4. Future Year 1980 In 1990, the memory will be so cheap that you will not have to worry about paging, swapping, virtual memory, memory hierarchy, and....

  5. Traffic Management on the Info Superhighway CAC 1 UPC 3 Shaping 2 Scheduling 4 Selective 5 6 FrameDiscard 7 Traffic Monitoring and feedback

  6. Traffic Mgmt Functions • Connection Admission Control (CAC): Can quality of service be supported? • Traffic Shaping: Limit burst length. Space-out cells. • Usage Parameter Control (UPC): Monitor and control traffic at the network entrance. • Network Resource Management: Scheduling, Queueing, resource reservation • Priority Control: Cell Loss Priority (CLP) • Selective Cell Discarding: Frame Discard • Feedback Controls: Network tells the source to increase or decrease its load.

  7. Classes of Service Guaranteed Standby Joy Riders Confirmed

  8. Classes of Service • ABR (Available bit rate): Source follows network feedback. Max throughput with minimum loss. • UBR (Unspecified bit rate): User sends whenever it wants. No feedback. No guarantee. Cells may be dropped during congestion. • CBR (Constant bit rate): User declares required rate.Throughput, delay and delay variation guaranteed. • VBR (Variable bit rate): Declare avg and max rate. • rt-VBR (Real-time): Conferencing.Max delay guaranteed. • nrt-VBR (non-real time): Stored video.

  9. ABR: Binary Rate-based Scheme EFCI • Explicit forward congestion indicator (EFCI) set to 0 at source • Congested switches set EFCI to 1 • Every nth cell, destination sends an resource management (RM) cell to the source indicating increase amount or decrease factor Source Destination RM

  10. Current Cell Rate Explicit Rate The Explicit Rate Scheme • Sources send one RM cell every n cells • The RM cells contain “Explicit rate” • Destination returns the RM cell to the source • The switches adjust the rate down • Source adjusts to the specified rate

  11. Bridge Bridge ATM LAN Emulation • Problem: Need new networking s/w for ATM • Solution: Let ATM network appear as a virtual LAN • LAN emulation implemented as a device driver below the network layer

  12. LE Header (2 Bytes) IEEE 802.3 or 802.5 Frame 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.

  13. Applica-tions ATMSwitch Bridge IP IPX IP IPX NDIS ODI NDIS ODI LANEmulation AAL5 AAL5 ATM ATM PhysicalLayer PhyLayer Protocol Layers ATM Host LAN Host Applica-tions ATM-LAN Bridge Bridging LANEmulation Media Access Control ATM Switch Media Access Control ATM PhyLayer PhyLayer PhyLayer PhysicalLayer

  14. 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)

  15. LAN Emulation 1. Client gets recipient's address from LES and sets-up a VC. LAN Emulation Server 3. Messages for ATM clients are delivered directly. Switches ATM client B Bridge 2. Client sends messages on the VC 4. Messages for non-ATM clients are forwarded through bridges Broadcast/Unknown Server (BUS) Non-ATM client

  16. Operation • 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.

  17. 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 addresses

  18. Flush Protocol • Clients can send unicast packets via BUS while trying to resolve the address Þ Out-of-order arrivals • When the direct VCC is setup, clients send a “Flush message” to destination. Destination returns it to source. Source can then send packets on direct VC. Direct Client A Client B BUS Flush Flush

  19. LANE v2.0 • Allows multiple LE Servers: LES, BUS, and LECS on a single ELAN • LAN Emulation network-to-network interface (LNNI): Specifies interfaces for communication between the LE server entities. LECSLESBUS LECSLESBUS LNNI LogicalELAN Physical ELAN 1 Physical ELAN 2

  20. LANE v2.0 (Cont) • Server cache synchronization protocol • Changes to LAN Emulation User-to-network Interface (LUNI): • Quality of service (8 global classes) • Enhanced support for PVC • LLC multiplexing • Support for ABR • Enhanced multicast supportMulticast trees (VCs) different from broadcast tree • Status: LUNI 2.0 was in straw ballot in April 97

  21. ATM Virtual LANs • Physical View Router A1 A2 ATM Switch LANE Server A LANE Server B B1 B2 • Logical View A1 B1 Router A2 B2

  22. Summary • ATM has sophisticated traffic management • CBR, ABR, UBR • ABR provides feedback • LANE allows current applications to run on ATM • LANE V2 allows multiple servers Þ Bigger ELANs

  23. Homework • Read Section 14.3 of Stallings