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Engineering Approaches to Computer Networking Protocol Implementation

This comprehensive guide explores the engineering strategies for implementing computer networking protocols, focusing on the dependencies of structure and environment. It covers partitioning functionality between user and kernel space, addressing trade-offs in software engineering, customizability, security, and performance. The document details interface strategies, context-switch times, data copy costs, and the impact of latency and cache effects. It presents practical insights, performance metrics, and rules of thumb for optimization, helping engineers make informed decisions in protocol design.

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Engineering Approaches to Computer Networking Protocol Implementation

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  1. Protocol Implementation An Engineering Approach to Computer Networking

  2. Protocol implementation • Depends on structure and environment • Structure • partitioning of functionality between user and kernel • separation of layer processing (interface) • Environment • data copy cost • interrupt overhead • context switch time • latency in accessing memory • cache effects

  3. Partitioning strategies • How much to put in user space, and how much in kernel space? • tradeoff between • software engineering • customizability • security • performance • Monolithic in kernel space • Monolithic in user space • Per-process in user space

  4. Interface strategies • Single-context • Tasks • Upcalls

  5. Monolithic in kernel

  6. Monolithic in user space

  7. Per-process in user space

  8. Interfaces • Single-context • Tasks • Upcalls

  9. Single context

  10. Tasks

  11. Upcalls

  12. Protocol implementation

  13. Some numbers • 10 Kbps 400 ms • 100 Kbps, 40 ms • 1 Mbps, 4 ms • 100 Mbps, 40 µs • User-to-kernel context switch ~40 µs • Copying the packet ~25 µs • Checksum in software ~40 µs • Scheduling delays ~150 µs (depends on workload) • Interrupt handling ~10-50 µs (depends on the bus) • Protocol processing ~15 -100 µs (depends on protocol complexity)

  14. Rules of thumb • Optimize common case • Watch out for bottlenecks • Fine tune inner loops • Choose good data structures • Beware of data touching • Minimize # packets sent • Send largest packets possible • Cache hints • Use hardware • Exploit application properties

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