[Srcomp] Comments on REQ-8-17-FWD-EFFICIENCY

[Ron Bonica <[e-mail]>]

Folks,

The metrics associate with REQ-8-17-FWD-EFFICIENCY are invalid. Currently, the metrics are:


  *   D.PRS(segment list): worst-case number of headers parsed during processing of the segment list.
  *   D.LKU(segment list): worst-case number of FIB lookups during processing of the segment list.

D.PRS assumes that parsing a second extension header is expensive on all ASICs. While it may be expensive on some ASIC's it is extremely inexpensive on others. Retaining this metric doesn't optimize the solution for operators. It merely creates an advantage for the ASIC that can't parse additional extension headers efficiently.

D.LKU assumes that it is possible to determine how many lookups a particular compression mechanism requires. It ignores the fact that the FIB can be optimized to reduce the number of lookups. Furthermore, it fails to make a distinction between longest match lookups and index lookups.

Finally, this requirement should be stated from the network operators perspective, not the ASIC developer's. The network operator doesn't care how many headers were parsed or how many lookups were execute. It cares about:


  *   How many packet per second the ASIC can process
  *   How much power the ASIC consumes
  *   How much heat the ASIC generates
  *   How much the ASIC costs

Unless we can develop better metric for this requirement, we should drop it.

                                                                                           Ron





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