[e2e] Stupid Question: Why are missing ACKs not considered as indicator for congestion?

Joe Touch touch at ISI.EDU
Thu Feb 1 10:45:58 PST 2007

David Borman wrote:
> Also, there is no requirement that the Timestamps values reflect actual
> clock values, or that they be consistent across connections.  Each
> connection can start at a random value for the starting point for ticks
> on that connection.  They can even represent different scales.  PAWS
> doesn't need to know what the timestamp values represent, it only
> depends on the fact that the values are increasing over time.

They need to represent 'real time'; the offset is irrelevant (except for
PAWS, as you note), but it needs to be incremented in a realistic way:

      The timestamp value to be sent in TSval is to be obtained from a
      (virtual) clock that we call the "timestamp clock".  Its values
      must be at least approximately proportional to real time, in order
      to measure actual RTT.

I don't see how they could represent different scales and be compliant
with current spec, although, as you hint, the scale could be kept on a
per connection basis, but that would be off-spec.


Joe Touch
Sr. Network Engineer, USAF TSAT Space Segment

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