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ATM: A view from the trenches

An introduction to my experience with ATM in a Cisco environment at Northwestern University, reviewing basic ATM theory and LANE, and discussing NU's network topology.

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ATM: A view from the trenches

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  1. ATM: A view from the trenches .

  2. Introduction • Laura Grill: l-grill@nwu.edu • *my* experience with ATM • cisco environment at Northwestern University

  3. Agenda • Why ATM? • Review of basic ATM theory and LANE • A look at NU’s network topology

  4. Why ATM? • 1996 ATM was the next big thing • connection oriented benefits of circuit switched using virtual circuits • efficient use of bandwidth as in packet switched • Decision was made at executive level for: • combine voice and data worlds • ATM to the desktop • 1997 built ATM backbone and bought OC-12 to Ameritech NAP • to handle voice data and video to and from the university

  5. New technologies:New strategy • The enabling technologies that make it feasible to integrate services w/o ATM • voice over IP • QOS for connectionless networks • gigabit ethernet • Today, ATM as a backbone and wan technology w/ no plans to grow it • Moving gigabit into the backbone (keeping existing ATM) • Frame versus cell: I'd rather have frames

  6. Basic ATM theory • Connection oriented vs. connectionless • 53 byte cells • Uses virtual circuits, identified with VPI/VCI

  7. Broadcast based "legacy" protocols • IP, IPX, AppleTalk (use broadcast discovery) • Why is this a problem? • Catch 22 - can’t talk on the network until a circuit is established and can’t establish a circuit without an address • Can’t broadcast on the phone network (no mechanism for this)

  8. Ways to solve the broadcast problem • RFC 1483 [native IP over ATM] • RFC 1577 [classical IP] • LANE (LAN Emulation) • MPOA

  9. LANE system • 3 servers: LECS, LES, BUS • 1 client: LEC

  10. Servers • LECS - LAN Emulation Configuration Server • hold information about the LES for each emulated LAN and gives that info to the LEC when it comes on-line • LES - client register their MAC and ATM address with the LES • BUS- maintains a VC that connects all the clients together emulated a broadcast

  11. Client • LEC - LAN Emulation Client (can be a host or router or switch)

  12. Procedure for a LEC to become part of the emulated LAN • LEC comes up and creates VC to LECS (using well known address or ILMI or statically configured) • LECS tells it what to emulate and who the LES is and what it's ATM address is • The client then registers it's MAC and ATM address with the LES • LES assigns a BUS • At this point many VC’s have been built to mesh all the LEC’s together

  13. ATM Topology at NU • See diagrams • ATM as a backbone technology to connect buildings to the core • use ATM for our WAN - OC-3c to NAP and OC-3c to Chicago campus • Some FDDI still remains • Will add gigabit this year

  14. The end • Questions?

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