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Addressing Interoperability: Issues and Challenges

Addressing Interoperability: Issues and Challenges. Raj Jain The Ohio State University Columbus, OH 43210 Jain@cse.ohio-State.Edu http://www.cse.ohio-state.edu/~jain/. Overview. Life Cycle of Technologies Interoperability and Standards Issues ATM Traffic Management.

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Addressing Interoperability: Issues and Challenges

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  1. Addressing Interoperability: Issues and Challenges Raj Jain The Ohio State UniversityColumbus, OH 43210Jain@cse.ohio-State.Edu http://www.cse.ohio-state.edu/~jain/

  2. Overview • Life Cycle of Technologies • Interoperability and Standards Issues • ATM Traffic Management

  3. Life Cycles of Technologies • Phase 1: Research • Phase 2: Productization • Phase 3: Transition to the next technology Number of Problems Solved Time Phase 1 Phase 2 Phase 3

  4. 40M 30M 20M 10M Jan91 Jan06 Jan97 Internet Technology HostCount

  5. Life Cycle: Satellite Networking • Phase 1: Research Proprietary/competing solutions • Phase 2: Standard based interoperable solutions Number of Problems Solved SatelliteNetworking Time 1998

  6. Networking: Failures vs Successes • 1980: Broadband Ethernet (vs baseband) • 1984: ISDN (vs Modems) • 1986: MAP/TOP (vs Ethernet) • 1988: OSI (vs TCP/IP) • 1991: DQDB • 1992: XTP (vs TCP) • 1994: CMIP (vs SNMP)

  7. Requirements for Success • Low Cost • High Performance • Killer Applications(Remote areas, Distance Insensitive, Multicast) • Timely completion • Manageability • Interoperability • Coexistence with legacy (terrestrial) networks

  8. Interoperability: Example • Phone System: Any phone, any carrier(s), any place AT&T PTT Ameritech

  9. Teledesic PTT Interoperability? Hughes • Satellite Network: Any dish, any satellite system, any place

  10. Application Application Transport Transport Network Network Datalink Datalink Physical Physical Layers of Interoperability • Physical: Spectrum Management, Common Air Interface • Datalink: DAMA/MAC • Network: Mobility, Handoff • Transport: Satellite/Terrestrial TCP/ATM • Application: Paging, Data, Messaging

  11. Standards: A Partial List • Telecommunication Industries Association (TIA) • Common Air Interface • Spectrum Management • International Telecommunications Union (ITU) • QoS • ATM Forum • Wireless ATM • Traffic Management

  12. Why ATM? • ATM vs IP: Key Distinctions 1. Traffic Management: Explicit Rate vs Loss based 2. QoS based routing: PNNI 3. Signaling: Coming to IP in the form of RSVP 4. Switching: Coming to IP as label switching ATM IP

  13. Our Goal • Ensure satellite/terrestrial interoperability in ATM TM • Ensure that the new ATM Forum TM 4.0/5.0 specs are “Satellite-friendly” • There are no parameters or requirement that will perform badly in a long-delay satellite environment • Users can use paths going through satellite links without requiring special equipment • Develop optimal solutions for satellite networks This work is sponsored by NASA Lewis Research Center

  14. Terrestrial Satellite Issues • Binary vs Explicit Rate Feedback • ABR vs UBR: Available bit rate vs Unspecified bit rate • Improving performance over ABR: VS/VD • Improving Performance over UBR: Guaranteed Rate Note: The alternative that is best for satellite networks may or may not be so for terrestrial networks.

  15. EFCI Current Cell Rate Explicit Rate Binary vs Explicit Rate • Binary: Explicit forward congestion indication (EFCI) bit in the cell header set by congested switches.Based on DECbit scheme. • Explicit Rate: Sources send one RM cell every n cells.The switches adjust the explicit rate field down.

  16. Binary vs Explicit Feedback Go 30 km East35 km South Go left

  17. Why Explicit Rate Indication? • Longer-distance networks Can’t afford too many round-trips  More information is better • Rate-based control Queue length = Rate Time Time is more critical than with windows

  18. Bottleneck SatelliteLink Workgroup Switch VS/VD • Without Virtual Source/Virtual Destination: • With VS/VD: • With VSVD, the buffering is proportional to the delay-bandwidth of the previous loop Þ Good for satellite networks

  19. ABR or UBR? • Intelligent transport or not?

  20. Dest. Source ATM Router Dest. Source Router ABR vs UBR ABR Queue in the sourceNetwork Qs = k RTT Pushes congestion to edges Good iff end-to-end ABR Fair UBR Queue in the networkNetwork Qs = S Windows No backpressure Good iff TCP. Generally unfair

  21. Ways to Improve UBR over Satellites 1. Reserve a small fraction of bandwidth for UBR class in the switches Þ Guaranteed Rate Service. • For WANs, the effect of reserving 10% bandwidth for UBR is more than that obtained by EPD, SD, or FBA • For LANs, guaranteed rate is not so helpful. Drop policies are more important. 2. Implement “Selective Acknowledgement” in end-systems. Disable “Fast retransmit and recovery” in end-systems.

  22. Summary • Interoperability is the key to success of a technology • Layers of interoperability: Air interface to applications • ER better for satellites than Binary feedback. • ABR better than UBR for long-delay paths • VS/VD can help reduce the impact of satellite delays • Reserving a small capacity helps UBR

  23. Our Publications All our ATM Forum contributions and papers are available on-line at http://www.cis.ohio-state.edu/~jain/ • Specially see “Recent Hot Papers”

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