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A Router Architecture to Achieve Link Rate Throughput in Suburban Ad-Hoc Networks

A Router Architecture to Achieve Link Rate Throughput in Suburban Ad-Hoc Networks. Ronald Pose Carlo Kopp Muhammad Mahmudul Islam School of Computer Science & Software Engineering Monash University. Outline. Definition of the SAHN Required features & design steps for this system

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A Router Architecture to Achieve Link Rate Throughput in Suburban Ad-Hoc Networks

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  1. A Router Architecture to Achieve Link Rate Throughput in Suburban Ad-Hoc Networks Ronald Pose Carlo Kopp Muhammad Mahmudul Islam School of Computer Science & Software Engineering Monash University

  2. Outline • Definition of the SAHN • Required features & design steps for this system • Survey of existing systems • Possible hardware architecture • Required properties of RTOS for the SAHN • Comparison of various RTOSs • Initial development platform for the SAHN • References • Questions

  3. SAHN (1/3) • Provides services not offered by commercial service providers • Bypass expensive infrastructure for broadband • Provide symmetric bandwidth • WLAN in inadequate wiring infrastructure • Bypass ongoing service charges for Telco independent traffic • Features multi-hop QoS routing • Security throughout all layers • Utilizing link states (e.g. available bandwidth, link stability, latency, jitter and security) to select suitable routes • Avoid selfish routing strategy to avoid congestion • Proper resource access control and management

  4. SAHN (2/3) • Ideal for cooperative nodes. E.g. spread over a suburban area, connecting houses and business • Topology is quasi static • Uses wireless technology • Symmetric broadband, multi Mbps bandwidth

  5. SAHN (3/3) • No charges for SAHN traffic • SAHN services run alongside TCP/IP • Conceived by Ronald Pose & Carlo Kopp 1997

  6. Required Features for this System SAHN routing system should have the following features to avoid system bottleneck • Link rate throughput • Scalability • Low development cost

  7. Design Steps A scalable system achieving link rate throughput can be designed by the following steps • Identify time critical & non-time critical routing tasks • Select appropriate interconnection fabric • Design parallel processing engines for time critical tasks • Select a real-time operating system which can • manage the whole system efficiently • operate with small amount of memory and disk space

  8. Routing Tasks in a SAHN Node

  9. Various Router Architectures

  10. First Generation Router Configuration • a shared backplane bus • a CPU • a shared pool of memory • some line cards connected to the media. Advantage • simple to implement Disadvantage • data has to cross the shared bus several times, imposing a severe system bottleneck.

  11. Second Generation Router Configuration • both line cards and packet forwarding engines had fast processors with cache memories • a shared backplane bus Advantage • less load on shared bus Disadvantage • bus based architectures have traffic dependant throughput

  12. Third Generation Router Configuration • both line cards and packet forwarding engines have fast processors with cache memories • switch fabric instead of a shared bus Advantage • switch fabric provides non-blocking interconnection of time critical components with much higher capacity and speed than a traditional backplane bus Disadvantage • costly • complicated design

  13. Various Switch Fabrics (1/4) Shared medium switch fabric • like bus based backplanes of first generation routers • imposes bottleneck for inter-module traffic flow Shared memory switch fabric • connects input and output ports to a central memory pool in parallel • input and output ports can have simultaneous read and write accesses to the shared memory pool • better throughput than a shared bus • performance limited by memory access time

  14. Various Switch Fabrics (2/4)

  15. Various Switch Fabrics (3/4) Distributed output buffered switch fabric • splits the shared memory into separate output buffers/output port • input ports have separate connections to their output buffers • systems with large port counts require more memory & complicated backplane layout Space division/crossbar switch fabric with input buffers • all input and output ports are interconnected for unicast inter-port traffic flow • all input ports have their own buffers • the speed of memory buffer need not to be more than that of its associated port

  16. Various Switch Fabrics (4/4)

  17. A Generic High-Speed Router Architecture

  18. Possible Router Architecture for SAHN (1/2) The SAHN router follows a hybrid approach • A packet processing engine (PPE) is connected with each line card • A central routing processing engine (RPE) performs the non-time critical tasks. • The PPE forms the packet forwarding engine (PFE) • The PFEs are connected to each other through a suitable switch fabric

  19. Possible Router Architecture for SAHN (2/2)

  20. Properties of the RTOS in SAHN (1/2) • Higher-priority tasks must have higher preference • There should be support for fixed-priority pre-emptive scheduling for all of its tasks • Interrupt latency & the context switching time should be as small as possible • It must be cheap • Source code should be available to resolve problems with the application code • It has to be highly portable to various processor families

  21. Properties of the RTOS in SAHN (2/2) • It must support multiple processors simultaneously • Its image should fit in a small ROM/Flash-disk • It should have a familiar development environment, possibly POSIX compliant

  22. Comparison Among Various RTOSs (1/3)

  23. Comparison Among Various RTOSs (2/3) *as per GNU Public Licensing agreement.

  24. Comparison Among Various RTOSs (3/3)

  25. Initial Development Platform Initially we have decided to work with RTLinux or RTAI because • RTOSs providing more scalable properties tend to be far more expensive in terms of both upfront costs and recurring royalty/ licensing fees • some of them are not provided with source codes • RTLinux or RTAI are free under GNU Public Licensing agreement • Some performance evaluation of ad-hoc routing protocols have been done with Linux system

  26. References • R. Pose and C. Kopp.Bypassing the Home Computing Bottleneck: The Suburban Area Network. 3rd Australasian Comp. Architecture Conf. (ACAC). February, 1998. pp.87-100. • A. Bickerstaffe, E. Makalic and S. Garic.CS honours theses. Monash University. www.csse.monash.edu.au/\~rdp/SAN/. 2001 • P. Misra. Routing Protocols for Ad Hoc Mobile Networks.www.cis.ohio-state.edu/~jain/cis788-99/adhoc_routing/index.html. 02/07/2000 • Aweya James.IP Router Architectures: An Overview. Nortel Networks. Ottawa, Canada, K1Y 4H7.http://www.owlnet.rice.edu/\elec696/papers/weya99.pdf, 05/01/2003. • P. Newman, G. Minshall and L. Huston.IP switching and gigabit routers. IEEE Communications Magazine. January, 1997. • Sayrafian Kamran. Overview of Switch Fabric Architectures,http://www.zagrosnetworks.com. July, 2002. • A New Architecture for Switch and Router Design.http://www.pmc-sierra.com/pressRoom/pdf/lcs\wp.pdf. 05/01/2003

  27. Thank You ?

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