ATM: A view from the trenches.

Introduction Laura Grill: Grill: *my* experience with ATM*my* experience with ATM cisco environment at Northwestern Universitycisco environment at Northwestern University

Agenda Why ATM?Why ATM? Review of basic ATM theory and LANEReview of basic ATM theory and LANE A look at NU’s network topologyA look at NU’s network topology

Why ATM? 1996 ATM was the next big thing1996 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: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 NAP1997 built ATM backbone and bought OC-12 to Ameritech NAP –to handle voice data and video to and from the university

New technologies:New strategy The enabling technologies that make it feasible to integrate services w/o ATMThe 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 itToday, ATM as a backbone and wan technology w/ no plans to grow it Moving gigabit into the backbone (keeping existing ATM)Moving gigabit into the backbone (keeping existing ATM) Frame versus cell: I'd rather have framesFrame versus cell: I'd rather have frames

Basic ATM theory Connection oriented vs. connectionlessConnection oriented vs. connectionless 53 byte cells53 byte cells Uses virtual circuits, identified with VPI/VCIUses virtual circuits, identified with VPI/VCI

Broadcast based "legacy" protocols IP, IPX, AppleTalk (use broadcast discovery)IP, IPX, AppleTalk (use broadcast discovery) Why is this a problem?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 addressCatch 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)Can’t broadcast on the phone network (no mechanism for this)

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

LANE system 3 servers: LECS, LES, BUS3 servers: LECS, LES, BUS 1 client: LEC1 client: LEC

Servers LECS - LAN Emulation Configuration ServerLECS - 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 LESLES - client register their MAC and ATM address with the LES BUS- maintains a VC that connects all the clients together emulated a broadcastBUS- maintains a VC that connects all the clients together emulated a broadcast

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

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)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 isLECS 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 LESThe client then registers it's MAC and ATM address with the LES LES assigns a BUSLES assigns a BUS At this point many VC’s have been built to mesh all the LEC’s togetherAt this point many VC’s have been built to mesh all the LEC’s together

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

The end Questions?Questions?