Re: [dtn] [EXTERNAL] draft-ietf-dtn-bibect-03 issues

["Burleigh, Scott C (US 312B)" <[e-mail]>]

Felix, thanks for these.  I'm working on the next edition of this draft and have modified it per your points 1(b) and 2.

I think the language you object to in 1(a) is pretty close to correct, though.  "Instantiation" is the construction of the node's initial state.  The state of the node might or might not reside in some genuinely non-volatile medium, such as disk storage.  If it does, then restarting the node would mean resuming operation of the node starting from its current state as retrieved from that non-volatile medium; in this case, the CTCs would be elements of node state and custodial transmission counting would correctly resume from the current value.  If not - that is, if the node is truly re-instantiated - then there is no way to retain the values of the CTCs from the moment at which the node was stopped; the counts must be initialized to zero.  Do you see an alternative?

Scott

From: dtn <[e-mail]> On Behalf Of [e-mail]
Sent: Friday, May 21, 2021 1:55 AM
To: [e-mail]
Subject: [EXTERNAL] [dtn] draft-ietf-dtn-bibect-03 issues

Hi,

I have spotted two issues in draft 3 of the Bundle-In-Bundle Encapsulation:

1)  Custodial Transmission Count

The CTC is defined in 3.2 as:

     1. A "custodial transmission count" (CTC).  A CTC is a
        monotonically increasing integer indicating the number of
        custodial BPDUs that have been issued to this BIBE node by the
        local node since instantiation of the local node.

a) To have the CTC as the number of BPDUs since the instantiation of the local node might be problematic in cases where the local node is re-started because the CTC is later used as 'Transmission ID' which should be unique over some time frame.

b) In the definition above, the CTC is defined per custodial node. However, later it is stated:

"The transmission ID for a BPDU for which custody transfer IS
   requested SHALL be the current value of the local node's custodial
   transmission count, plus 1."

To me, this seems to indicate a single CTC per local node.

Scott confirmed that the first interpretation is correct (one CTC per custodial node), so this text should be updated. It may still make sense to require increasing of the transmission id by 'plus 1' only as this allows more efficient custody signals.

2) Section 3.4 defines:

A  "custody transfer status report" is a bundle status report with the "reporting node attempted custody transfer" flag set to 1.

This flag and issuing this status report is described nowhere. I assume this section should be removed.

Regards,
Felix

_________________________________________
ESA - European Space Agency
Dr. Felix Flentge
Software Engineer, OPS-GSB
Ground Systems Engineering Department
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