[Sis-dtn] BPv7 QOS reliability

[Sipos, Brian J.]

All,

After thinking over the last presentation on BP QOS extension block content,
specifically the discussion about the reliability code points proposed, I
think there may be a more consistent way to name and think about the
proposed values.

The last proposal had values of (from what I remember, in no specific
order):

*	Required reliable
*	Preferred reliable
*	Preferred unreliable
*	Required unreliable

 

There was contention about what "required" meant and if they are meaningful
values, but I think these can be augmented slightly with the knowledge that
BP nodes are expected to store-and-forward as needed, so the code points
could be shifted slightly to have these names and definitions which I think
are more compatible with both what nodes should do with them and how people
can think about them.

*	Wait for reliable - Wait (up to the bundle lifetime) for a reliable
CL, if one is expected to become available, otherwise use an unreliable CL
now.
*	Immediate reliable - Forward with a reliable CL if one is available
immediately, otherwise use an unreliable CL now.
*	Immediate unreliable - Forward with an unreliable CL if one is
available immediately, otherwise use a reliable CL now.
*	Wait for unreliable - Wait for an unreliable CL, otherwise use a
reliable CL now.

 

The key difference here is that nodes have future information about local
contact plans and CL availability, and the first and last values allow that
information to be used differently. So rather than saying "it has to be
reliable or nothing" it's allowing a node to take into account future
expected behavior (within the specific bundle's lifetime) to inform its
short-term logic.

 

Not sure if this is helpful, but that kind of distinction might clarify the
intent of those code points and make them each more actionable by a node.

Brian S.

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