[Sis-dtn] RE: [dtn-interest] [dtn] DTN static routing

Thu Jun 11 13:06:37 UTC 2015

Lloyd,

You're right, the non-utility of the SCPS Network Protocol (and the security protocol) were in a sense wasted effort because they weren't picked up by the space community.  The SCPS File Protocol was essentially a rubber-stamp of FTP, which the space community didn't pick up either.  The CCSDS File Delivery Protocol (CFDP) has had more success and is being baselined into missions now.  That the space community wouldn't take up what was essentially a copy of the Internet Protocol Suite, as well as the realization of the performance benefits of relaying from the Mars rovers, is what drove the development of an internetworking mechanism that could serve the space community.  That effort is DTN.

CCSDS is not getting the IETF to do anything; IETF is picking up and advancing work done by the IRTF.  We (CCSDS) certainly HOPE to be able to adopt / adapt the result for use by CCSDS agencies, with a strong desire to do so in an on-the-wire-compatible way.  This is bad how?  If your argument is that CCSDS should simply cease to exist and agencies should use standards from other bodies (like the IETF) for missions, fine.  I've tried making that argument to the people designing missions and have not succeeded (see the early draft of the CCSDS BP and LTP profiles), but maybe you'd do better.  In that case, however, be sure that the specifications from other organizations meet all of the space community's requirements, even where they conflict with those of the much larger terrestrial community.  I don't think that'll fly (NPI).

I'm not sure what to make of your parenthetical statement.  CCSDS' mission is to define recommended standards for space communication.  The agencies that make up CCSDS (and the technical people within those agencies) think there's a win to the work that CCSDS is doing, otherwise the agencies wouldn't support it.  If you as a private citizen take issue with how the space agency of your government spends its money, work for them and change the situation from the inside or lobby them from the outside.  With respect to 'rubber stamping' existing specifications, for the internetworking / DTN-related standards, I have argued strongly for on-the-wire compatibility with corresponding terrestrial standards with additions / modifications that are beneficial to space missions because I think it provides the best capabilities for the least effort.  To give an example, we found when running RFC5050 BP to (from) the international space station that custody acknowledgements were congesting the uplink (which was on the order of 100 bits per second).  The people at the University of Colorado who were running the ground side developed a mechanism to aggregate / compress multiple custody signals together in order to reduce the uplink bandwidth.  It helped them a lot.  Also, when JAXA first reviewed the proposed CCSDS spec (essentially a rubber stamp of RFC5050) they had concerns about the number of priority levels provided.  We included an Extended Class of Service block type in the CCSDS specification.  So, the non-inclusion of space-specific requirements in RFC5050 drove some domain-specific augmentations to the specification.  If the work coming out of the IETF includes everything the space agencies could possibly want then sure, CCSDS can simply adopt the IETF specification (which will take some time but very little money) and be done.  I'd LOVE that.  Please (and there's no sarcasm here) lobby the IETF WG to include all the capabilities in the current CCSDS BP spec and I'll argue that CCSDS should simply adopt it unchanged.  If the IETF specification(s) do not include all that CCSDS thinks they need, but those capabilities can be added in a reasonable way, we'll do it.

I don't get the rest of your argument.  CCSDS has moved out adopting the IRTF standard because of the timeline for getting new technologies adopted into space missions and because there are some missions now that can make use of it now.  Those missions want something that is stable (in the way that a particular RFC is stable), and they want assurances that the technology will work in space environments.  Also, when CCSDS began standardization of the CCSDS profile of RFC5050, there was not IETF working group.  Our (or at least MY) plan going forward is to try to convince missions to adopt internetworking technology (using IP and the current RFC5050-based CCSDS specification as the standards) and then to update the CCSDS BP spec to follow any RFC produced by the IETF.  My hope (I could be wrong) is that once missions have signed on to the benefits of an internetworked communication architecture, that slight modifications to the actual protocol(s) used to implement that architecture will be a non-issue.  I've been very open about this with CCSDS and NASA.

Wait, what?!?!?   CCSDS dearly wants BP (DTN) to succeed terrestrially.  CCSDS (and I argue, the space community as a whole) would like nothing better than to buy commercial routers (or appliances, something) with BP baked in that they can deploy to ground stations, mission control centers, scientists, and whatever spacecraft they might be able to use commercial hardware on (e.g. ISS, generally things with atmosphere and people).  This would be the biggest possible win for CCSDS - to cause something that CCSDS can use (DTN) to be adopted by a wider terrestrial community that actually has a large market that can cause products to be built, matured, and tested at a MUCH faster rate than the space agencies, and at an economy of scale that the space agencies could only dream of.

The space community (wider than just CCSDS) has an interest in ensuring that the protocol developed by the IETF can in fact meet their requirements in addition to those of the other interested parties (see above, we want to buy the commercial equipment that we hope will result from the IETF effort).   Sure, with my CCSDS hat on I'll argue that the IETF WG should include whatever 'space-specific' requirements we think we have in the RFC5050-bis spec.  The IETF working group will adjudicate those requests in concert with all the other requirements from other parties and do what they think is best.  Based on whatever comes out of that, CCSDS will have to decide if they should switch to the new protocol (or a profile of it) or if they should live with the old one.

                        --keith

Dr. Keith Scott                                                                                           Office: +1.703.983.6547
Chief Engineer, J86A                                                                               Fax:      +1.703.983.7142
Communications Network Engineering & Analysis                    Email: kscott at mitre.org
The MITRE Corporation<http://www.mitre.org/>                                                                        M/S H300
7515 Colshire Drive
McLean, VA 22102

Area Director, CCSDS<http://www.ccsds.org/> Space Internetworking Services<http://cwe.ccsds.org/sis/default.aspx>

MITRE self-signs its own certificates.  Information about the MITRE PKI Certificate Chain is available from http://www.mitre.org/tech/mii/pki/

From: l.wood at surrey.ac.uk [mailto:l.wood at surrey.ac.uk]
Sent: Thursday, June 11, 2015 3:47 AM
To: Scott, Keith L.; gdt at ir.bbn.com
Cc: dtn-interest at irtf.org; dtn at ietf.org
Subject: Re: [dtn-interest] [dtn] DTN static routing

The SCPS lesson is interesting.

CCSDS took IETF standards for TCP and IP, and modified them with optimisations, before publishing them as CCSDS standards, expecting their use as CCSDS blue books to take off.

Those CCSDS standards didn't take off (SCPS-TP has some use as a lowest-common denominator PEP for govt use, that's about it, -NP, security etc. are dead) so e.g. Constellation baselines actual took-over-planet-Earth-meanwhile-that's-an-entire-planet-how-many-planets-does-CCSDS-have IP, reversing the CCSDS customisations. And Constellation got CCSDS to support actual IP better in the process.

Fast forward a quarter of a century, and CCSDS is getting the IETF to standardise the DTN bundle protocol in this workgroup, with the usual intent of modifying it for adoption in CCSDS as slightly different CCSDS book standards. Just like SCPS - and CCSDS customisations to the RFC5050 bundle protocol are already happening.

(Because the IETF stuff is Not Invented Here for CCSDS, space is too special, and if CCSDS doesn't write its own standards documents and do modifications as part of rubber stamping others' designs, what is it for as a standards body?)

So, to do this and diverge from what the IETF will produce, CCSDS has to be betting that what the IETF produces for the bundle protocol in this workgroup will not be at all popular as a standard.

Because, if the IETF bundle protocol is popular and widely adopted, an embarrassing reversal to adopt the real thing, the actual IETF standard, will result in a few years' time. Just like the reversal that replaced SCPS with the more popular IP, resulting in much wasted effort and economic cost.

So, this simple analysis suggests that it is not in CCSDS interests to see the bundle protocol succeed terrestrially. Quite the opposite, in fact.

So perhaps CCSDS can ensure that the IETF work is not successful terrestrially by ensuring its design as suitable for space as possible, and not for ground use? Looks like a good bet to me.

Lloyd Wood
http://sat-net.com/L.Wood/dtn

a sequel to 'A Bundle of Problems' has been suggested.
________________________________
From: Scott, Keith L. <kscott at mitre.org<mailto:kscott at mitre.org>>
Sent: Thursday, 11 June 2015 12:14:12 AM
To: Wood L Dr (Electronic Eng); gdt at ir.bbn.com<mailto:gdt at ir.bbn.com>; scott.c.burleigh at jpl.nasa.gov<mailto:scott.c.burleigh at jpl.nasa.gov>
Cc: dtn-interest at irtf.org<mailto:dtn-interest at irtf.org>; dtn at ietf.org<mailto:dtn at ietf.org>
Subject: RE: [dtn-interest] [dtn] DTN static routing

[My apologies, none of this has anything to do with static routing.  I address Lloyd's point about CCSDS and IP, then comment on Greg's original post on interoperability.]

Lloyd,

There is no obstacle to including IP in the space domain as far as CCSDS is concerned.

The IOAG-sponsored Space Internetworking Strategy Group (SISG) phase-1 report<https://www.ioag.org/Public%20Documents/SISG%20Phase%20I%20report%20%E2%80%93%20final.pdf> concluded that both IP and BP were valid approaches to internetworking in space.  BP is the preferred mechanism since it should work over a larger domain of network conditions than IP, but IP is explicitly mentioned as an option for space (and ground) links.  The whole Solar System Internetwork Concept of Operations<https://www.ioag.org/Public%20Documents/SISG%20Operations%20Concept%20for%20SSI%20-%20final%20version.pdf> reflects this.

CCSDS has in fact embraced the Internet Protocol Suite since the 1990s, and had a set of adaptations for space (including an 'IP-like' variant, SCPS-NP, that was deprecated in favor of simply using IP).

The NASA Constellation program, while embracing CCSDS data links, baselined IP as their initial internetworking protocol, and argued strongly for greater support for IP over those links, resulting in modifications to the CCSDS link layer services to better support IP and IP header compression in particular.

The Bundle Protocol is not just for CCSDS

Since at least 2001 when people doing sensor networks became interested in BP there has been interest in other applications of BP for environments other than space.  A number of organizations (with only NASA having an explicit space application) collaborated in the creation of the Bundle Protocol.  That BP was specified as an IRTF RFC and is now being considered in the IETF (I think) demonstrates the broad (including external-to-CCSDS) support.  The CCSDS Bundle Protocol is in fact an adaptation/profile of the IRTF RFC - we (in CCSDS) followed the IRTF - and we're going to do it again when the IETF specifies their version of bundle protocol and security.

To Greg's point on Naming and Interoperability

I concur that a proliferation of naming schemes may (OK, almost surely will) lead to a lack of truly global interoperability, and that it is exactly that global interconnectivity that was the big win for IP (and internetworking in general).  However, given that there are different camps interested in using BP with different requirements that seem to argue for different naming schemes but who can all make use of the 'base' bundle protocol, allowing a multitude of schemes seems like the best solution for now.

I hope that the DTN community figures out how they want to deal with that.  For example, gateways between naming regions can be constructed to connect those regions that want to / need to communicate, or one naming scheme could come to dominate (I know which one Scott would pick, and that that's not the one everyone would pick), or different communities with different needs / applications (and naming schemes) could decide that interoperability isn't worth the effort and live with it (their choice).  I DO think this discussion should inform the IETF WG, and that they (and the DTN community) should make a deliberate decision about how to proceed - i.e. whether to enforce a single naming/addressing scheme, or not.

I view BP as a tool to effect end-to-end communication in the environments where BP can function and IP cannot (or where IP doesn't perform well) rather than as a forklift replacement for IP, and so in my mind BP doesn't HAVE to enforce immediate universal interconnectivity.  People can use BP where and how it works for them; they've seen the benefits of interconnectivity, and where it makes sense to do so, they'll put in the effort to achieve it.  BP could one day replace IP I suppose, but I suspect it's like the quote which is not mine but for which I have not been able to find a good citation: "You're an excellent writer and your works will be remembered long after Shakespeare has been forgotten.  But not until then."

                        --keith

Dr. Keith Scott                                                                                           Office: +1.703.983.6547
Chief Engineer, J86A                                                                               Fax:      +1.703.983.7142
Communications Network Engineering & Analysis                     Email: kscott at mitre.org<mailto:kscott at mitre.org>
The MITRE Corporation<http://www.mitre.org/>                                                                        M/S H300
7515 Colshire Drive
McLean, VA 22102

Area Director, CCSDS<http://www.ccsds.org/> Space Internetworking Services<http://cwe.ccsds.org/sis/default.aspx>

MITRE self-signs its own certificates.  Information about the MITRE PKI Certificate Chain is available from http://www.mitre.org/tech/mii/pki/

-----Original Message-----
From: dtn-interest [mailto:dtn-interest-bounces at irtf.org] On Behalf Of l.wood at surrey.ac.uk<mailto:l.wood at surrey.ac.uk>
Sent: Tuesday, June 09, 2015 10:14 PM
To: gdt at ir.bbn.com<mailto:gdt at ir.bbn.com>; scott.c.burleigh at jpl.nasa.gov<mailto:scott.c.burleigh at jpl.nasa.gov>
Cc: dtn-interest at irtf.org<mailto:dtn-interest at irtf.org>; dtn at ietf.org<mailto:dtn at ietf.org>
Subject: Re: [dtn-interest] [dtn] DTN static routing

Greg says:

> Implicit in different groups using different schemes is a lack of global

> interoperability.  Most if not almost all of the usefulness of IP is due

> to the existence of a single interconnected global network.  But perhaps

> that is explicitly not part of the DTN vision.

Scott says:

> I'm pretty sure there is no globally embraced DTN vision

We addressed this in

Lloyd Wood, Peter Holliday, et al. "Sharing the dream: The consensual networking hallucination offered by the Bundle Protocol"

Peer-reviewed conference paper, Proceedings of the Workshop on the Emergence of Delay-/Disruption-Tolerant Networks (E-DTN), one of a number of workshops of the International Conference on Ultra Modern Telecommunication (ICUMT), St. Petersburg, Russia, 14 October 2009.

http://dx.doi.org/10.1109/ICUMT.2009.5345655

http://personal.ee.surrey.ac.uk/Personal/L.Wood/publications/index.html#e-dtn-position

Really, the bundle protocol exists as an overlay working across both CCSDS and IP, as a bulwark to prevent incursion of IP into the space domain by claiming interoperability as an overlay of both. CCSDS is the prime proponent of the bundle protocol, and any other use or adoption of DTN and the bundle protocol is entirely secondary to and providing added support for that.

There's a global vision for the bundle protocol, inasmuch as it meets CCSDS needs.

Lloyd Wood

http://sat-net.com/L.Wood/dtn

________________________________________

From: dtn-interest <dtn-interest-bounces at irtf.org<mailto:dtn-interest-bounces at irtf.org>> on behalf of Greg Troxel <gdt at ir.bbn.com<mailto:gdt at ir.bbn.com>>

Sent: Wednesday, 10 June 2015 3:55 AM

To: Burleigh, Scott C (312B)

Cc: dtn-interest at irtf.org<mailto:dtn-interest at irtf.org>; Rick Taylor; dtn at ietf.org<mailto:dtn at ietf.org>

Subject: Re: [dtn-interest] [dtn]    DTN static routing

"Burleigh, Scott C (312B)" <scott.c.burleigh at jpl.nasa.gov<mailto:scott.c.burleigh at jpl.nasa.gov>> writes:

> Greg, strictly speaking, I don't think we're adding a new addressing

> design, because there is no addressing in BP; there is only naming.

> There is no presumption of topological significance in endpoint IDs.

> Likewise, DTN isn't going to use a flat n-bit address space because it

> doesn't use any address space at all.

I was blurring naming/addressing, which is perhaps my error, but DTN

seems to have only one thing that is some mix of both concepts.

> More specifically, I don't find the same disconnect that you do.

> We've got self-delimiting numeric values, so why should we have to

> choose between solving the low-bandwidth problem and solving the

> large-network problem?  A numeric node ID can be 3 bytes (or even

> less) for users who need to work over constrained links, and it can be

> 10 bytes for users who have bandwidth to burn.  Let's not "burden"

> either community.

Implicit in different groups using different schemes is a lack of global

interoperability.  Most if not almost all of the usefulness of IP is due

to the existence of a single interconnected global network.  But perhaps

that is explicitly not part of the DTN vision.

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