[Sis-dtn] [EXTERNAL] Custody Transfer query
Dr. Keith L Scott
kscott at mitre.org
Wed Sep 1 17:28:54 UTC 2021
A little expansion;
1. With BPv6 custody transfer, nodes are not REQUIRED to take custody; a node may simply forward a bundle without taking custody, leaving the current custodian alone. This exacerbates the problem of trying to set a retransmission timer since the current custodian doesn’t have a protocol-enforced contract for who the next custodian will be.
2. The above problem is FURTHER exacerbated by fragmentation (though *I* believe this is largely semantic and that workable solutions exist). The ideas is that if I’m the custodian for a 1,000-byte bundle, and somebody downstream fragments it without taking custody, I can now get custody-acceptance signals for pieces of that bundle – pieces I never knew existed. So what do I do, especially if the retransmission timer (that I had trouble setting inf the first place) goes off? Do I retransmit the entire bundle, do I make fragments out of the bundle I have and retransmit all the un-custody-acked pieces?
So, in lieu of trying to solve the above, we opted for an approach where the custodian gets to affirmatively KNOW who’s going to take custody, and as a side-effect of BIBE-tunneling the custodial bundle to the next custodian, we can assert that the next custodial can/will take custody of the ENTIRE bundle.
Not *my* favorite solution, but there are definitely benefits.
v/r,
--keith
From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org> on behalf of Sanchez Net, Marc (US 332H) via SIS-DTN <sis-dtn at mailman.ccsds.org>
Date: Friday, August 20, 2021 at 11:41 AM
To: Simon Singh <simon.singh at eknoworks.com>, Pitts, Robert L. (MSFC-HP27)[HOSC SERVICES CONTRACT] <robert.l.pitts at nasa.gov>
Cc: sis-dtn at mailman.ccsds.org <sis-dtn at mailman.ccsds.org>
Subject: Re: [Sis-dtn] [EXTERNAL] Custody Transfer query
I believe one of the main reasons for the switch of custody transfer to BIBE is the inability to meaningfully/properly set the custody transfer retransmission timer in BPv6. This happens because at the Bundle Layer there is no way to tell which route a bundle will take to destination, or whether it will be fragmented on its way to it, so it is impossible to figure out what is a good value of the retransmit timer.
BIBE is supposed to be a convergence layer for the Bundle Protocol which acts as a hop-to-hop protocol rather than an end-to-end protocol. Therefore, since in BIBE you know explicitly which is the destination node to which the bundle will be sent, and there is no possibility for further fragmentation, you can have a better idea of the correct value for the retransmission timer (much like in LTP).
BIBE’s other motivation is security. By allowing you to encapsulate a bundle within another bundle, you can achieve functionality that is similar to a VPN in which encapsulated bundles are fully encrypted and possibly authenticated (fully meaning that both the payload and the header are encrypted).
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Marc Sanchez Net
Telecommunications Engineer
Jet Propulsion Laboratory
Office: (818) 354-1650<tel:(818)%20393-5840> | Email: marc.sanchez.net at jpl.nasa.gov<mailto:marc.sanchez.net at jpl.nasa.gov>
-----------------------------------------------------------------------------------------------------------------------
From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org> On Behalf Of Simon Singh
Sent: Friday, August 20, 2021 8:09 AM
To: Pitts, Robert L. (MSFC-HP27)[HOSC SERVICES CONTRACT] <robert.l.pitts at nasa.gov>
Cc: sis-dtn at mailman.ccsds.org
Subject: Re: [Sis-dtn] [EXTERNAL] Custody Transfer query
Thanks Lee.
I came across this, probably from Scott Burleigh. Any idea about "serious potential operational anomalies."
"• The “custody transfer” function is removed from BP and is defined instead in a new bundle-in-bundle encapsulation specification, to improve its efficiency and address several serious potential operational anomalies."
Best regards
Simon Singh
+1 443 538 7176 Cell
On Fri, Aug 20, 2021 at 8:16 AM Pitts, Robert L. (MSFC-HP27)[HOSC SERVICES CONTRACT] <robert.l.pitts at nasa.gov<mailto:robert.l.pitts at nasa.gov>> wrote:
I don’t know the exact reason but it was initiated in the IETF. Scott may be a better source.
Lee
From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org<mailto:sis-dtn-bounces at mailman.ccsds.org>> On Behalf Of Simon Singh
Sent: Friday, August 20, 2021 1:52 AM
To: Blanding, Beau T. (MSFC-HP27)[HOSC SERVICES CONTRACT] <beau.t.blanding at nasa.gov<mailto:beau.t.blanding at nasa.gov>>; sis-dtn at mailman.ccsds.org<mailto:sis-dtn at mailman.ccsds.org>
Subject: [EXTERNAL] [Sis-dtn] Custody Transfer query
Hi,
I would appreciate it if someone can provide insight regarding the following query.. Thanks
What was the motivation to move from BP6 style of custody transfer to one using BIBE?
Best regards
Simon Singh
+1 443 538 7176 Cell
On Thu, Aug 12, 2021 at 7:58 AM Blanding, Beau T. (MSFC-HP27)[HOSC SERVICES CONTRACT] via SIS-DTN <sis-dtn at mailman.ccsds.org<mailto:sis-dtn at mailman.ccsds.org>> wrote:
Good morning all,
Attached are BPv7 Red Book Discussion Topics from MSFC. We (MSFC) provide our opinions on how the topics listed within should be managed. Please provide your input via email on these topics so that we may take them into account as we write sections for the BPv7 book. If we run into a discussion that isn’t resolving over email, we will resolve in the SIS-DTN forum.
Regards,
Beau Blanding
HOSC Systems Engineer
MSFC 4663, Office C121
beau.t.blanding at nasa.gov<mailto:beau.t.blanding at nasa.gov>
-----Original Appointment-----
From: Dr. Keith L Scott <kscott at mitre.org<mailto:kscott at mitre.org>>
Sent: Wednesday, April 7, 2021 9:47 AM
To: Dr. Keith L Scott; sis-dtn at mailman.ccsds.org<mailto:sis-dtn at mailman.ccsds.org>
Cc: Navas, Tiffany A. (GSFC-581.0)[MTI SYSTEMS, INC.]; Torgerson, J. Leigh (JPL-332C)[JPL Employee]; HAMILTON, PAUL A. (JSC-EV811); Matusow, Carla L. (GSFC-4502); Strege, Susanne L. (GSFC-5830); LACY, SETH L DR-04 USAF AFMC AFRL/RVEN; Mayer, Jeremy P. (JSC-OT/ESA)[EUROPEAN SPACE AGENCY]; Burleigh, Scott C (JPL-312B)[JPL Employee]; Deaton, Joshua E. (MSFC-HP27)[HOSC SERVICES CONTRACT]; Gian.Paolo.Calzolari at esa.int<mailto:Gian.Paolo.Calzolari at esa.int>; Felix.Flentge at esa.int<mailto:Felix.Flentge at esa.int>; Bryant, Deann (MSFC-HP27); Wright, James R. (MSFC-HP27)[BIOSERVE Univ of CO]; George, Sandy (MSFC-IS40)[NICS]; Heiner, Sarah E.; Kazmi, Syeda A. (GSFC-5830); Tomaso.deCola at dlr.de<mailto:Tomaso.deCola at dlr.de>; Durkin, Alexander E. (GSFC-5830)
Subject: [EXTERNAL] [Sis-dtn] SIS-DTN Telecon
When: Wednesday, August 11, 2021 11:00 AM-12:00 PM (UTC-05:00) Eastern Time (US & Canada).
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20210407 – Just refreshing the calendar invite in case it got dropped somewhere.
Folks,
I’d like to set up some recurring SIS-DTN meetings to talk about our current work items. I’ve set these for every 2 weeks; if it looks like we don’t need to meet that often I’ll drop it down to monthly.
I’m proposing Wednesdays 11am; I get that this time won’t work for everyone, but let’s see how many can make it and if we have to we’ll hunt for a different time.
v/r,
--keith
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