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IFT Proposal

IFT Proposal. Changes Since Atlanta. Feedback During and after Atlanta. Adaption indication for TCP is a requirement (SCTP is example). It is desirable to enable software implementations over existing TCP implementations with best possible efficiency. Major Changes to IFT.

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IFT Proposal

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  1. IFT Proposal Changes Since Atlanta

  2. Feedback During and after Atlanta • Adaption indication for TCP is a requirement (SCTP is example). • It is desirable to enable software implementations over existing TCP implementations with best possible efficiency.

  3. Major Changes to IFT • Add adaption indication. • Make CRC optional and negotiated. • Allow speculative placement. • Allow negotiated markers if both ends consent.

  4. Optional CRC • Although CRC has low cost for custom hardware implementations, it is high cost for software implementations. • Many users will not require added protections of CRC. Examples exist of widely used protocols over TCP without added CRC.

  5. Speculative Placement • Pros: • Allows direct out of order placement by server side without requiring client side to insert markers or enforce alignment. • Allows software client on existing TCP implementation to talk to optimized hardware server in a way that is optimal for both ends.

  6. Speculative Placement • Cons – doing out of order placement requires the following: • NIC must track portions of buffer that have been written so as not to allow valid data to be overwritten by invalid speculative data. • Application interlock required so NIC is notified when a buffer may be rewritten. • Application must ignore unwritten portions of buffers as they may be trashed.

  7. Speculative Placement • May or may not be a good idea on balance. • Interesting to consider, though.

  8. Negotiated Markers • May not make sense to do both Speculative Placement and markers. Markers are not needed if SP is used. • Are markers really a win without guaranteed alignment? • If not, then markers should be used only when BOTH ends of a connections are RDDP custom hardware. Otherwise not negotiated.

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