Re: [dtn] working group last call on draft-ietf-dtn-bpbis

[Stephen Farrell <[e-mail]>]

Hi Scott,

On 27/03/17 21:27, Burleigh, Scott C (312B) wrote:
> Hi, Stephen.  I won't try to respond to all these points now, but I
> do want to advance a little bit of an argument on your point (B).
> 
> If we look at, say, RFC 5681, I think we see a great deal of firmly
> prescriptive text that has nothing to do with what bits are
> transmitted over the wire, and everything to do with how the TCP
> state machine is supposed to behave.  

But 5681 is based on some decades of really widespread deployment.
If the BP were in that position I think you'd have a good argument
there, but it isn't.

> I think this is true of
> virtually every MUST in the specification, and I think that in the
> absence of this prescriptive language it would be impossible to
> distinguish a correctly functioning router from a broken one --
> impossible to test a router for correct operation.

I don't believe that an ability to test such correctness from outside
a router is really necessary nor desirable at this point in the
evolution of the BP.

> I think the prescriptive language in the BPbis specification is just
> as necessary, for exactly the same reasons.
> 
> I understand that you disagree, but I don't yet understand why.

I guess I'll point at the examples I offered as to why. I look forward
to seeing your (or others') responses to those examples.

I do hope we agree that egregious/unnecessary MUST statements are a
bad idea though. If so, the question becomes whether or not all these
many MUSTs are needed or not.

Cheers,
S.

> 
> Scott
> 
> -----Original Message----- From: Stephen Farrell
> [mailto:[e-mail]] Sent: Monday, March 20, 2017 3:06
> PM To: Burleigh, Scott C (312B) <[e-mail]>; Marc
> Blanchet <[e-mail]>; dtn <[e-mail]> Subject: Re:
> [dtn] working group last call on draft-ietf-dtn-bpbis
> 
> 
> Hi Scott,
> 
> Belated responses below. I hope the quoting isn't too messed up to
> follow.
> 
> As a TL;DR, I'd say we might be best to debate point (B) below, that
> the current text is overly prescriptive. I'm entirely happy that the
> DoS-vector that would be the current reporting text won't make it to
> the RFC, so am ok if we don't spend so much time on that.
> 
> For the "too prescriptive" point, I think you and I Scott have had
> that debate before, so I'd be most interested in other WG
> participants telling me I'm just wrong that all those MUSTs are
> needed for interop. (I mean using some of the examples below that
> refer back to point (B) and not literally a sentence that means the
> same as the sentence before this one:-)
> 
> Cheers, S.
> 
> On 15/03/17 17:00, Burleigh, Scott C (312B) wrote:
>> Hi.  As Rick suggested, I'm posting my thoughts on Stephen's
>> comments to the list in addition to noting them on Ed's spreadsheet
>> - mainly transcribing them but amplifying in a few instances.
>> In-line below.
>> 
>> Scott
>> 
>> -----Original Message----- From: dtn [mailto:[e-mail]]
>> On Behalf Of Stephen Farrell Sent: Monday, January 23, 2017 7:33 PM
>> To: Marc Blanchet <[e-mail]>; dtn <[e-mail]> 
>> Subject: Re: [dtn] working group last call on draft-ietf-dtn-bpbis
>> 
>> 
>> Hiya,
>> 
>> I've done a review of bpbis-06 and have many comments. (Sorry:-)
>> 
>> Overall I don't think this is ready, and some more discussion of
>> some of the issues is needed. Since I've not followed the list as
>> closely as I'd have liked I may have missed some such discussion in
>> which case pointing me at the relevant bit(s) of the archive would
>> be a fine response.
>> 
>> I've tried to separate stuff into things that'd cause me to ballot
>>  DISCUSS in IESG evaluation (*), things that might not, and nitty 
>> things. I hope that helps, but don't take that categorisation too 
>> seriously:-)
>> 
>> Cheers, S.
>> 
>> (*) Note that I'll likely not still be on the IESG when this gets 
>> there (I escape in March) so the fact that I would ballot DISCUSS
>> is not that relevant to what other ADs might do.
>> 
>> 
>> Possibly major issues (DISCUSS like) 
>> ------------------------------------
>> 
>> (A) intro: The last bullet list of the things that are not
>> specified here seems problematic for a PS and I think needs more 
>> discussion/work. I'm not sure if it's only the text that needs
>> work, or if the missing specification is required now. Taking the
>> bullets one at at time (numbers are in order of presentation): 1)
>> This isn't clear enough, I'm not sure what's being omitted, 2)
>> Omitting routing I think is fair, 3) It's also fair to omot RIB/FIB
>> issues, 4) it's not ok to omit security mechanism definition,
>> (making [BPSEC] normative and waiting on that in the RFC editor
>> queue would fix this, and is IMO needed), 5) I'm not sure what's
>> right here.  I think it'd be good to have some list discussion
>> about this, as it'll certainly come up in IETF LC and IESG review
>> and having list traffic at which to point will help backup whatever
>> conclusions are reached.  In particular in 4.3, I don't think it's
>> acceptable for the BIB and BCB to not have a normative reference.
>> Similarly, the "TBD" for the other extension block types are not
>> appropritate. (But those can likely be informative refs.)
>> 
>> -	I'm fine with bringing bpsec along at the same time as bp(bis)
>> and tcpcl.
> 
> Cool. I think that's the right choice.
> 
>> 
>> (B) The spec is overly prescriptive in many places and ought be 
>> loosened up wherever possible. All we need is interop and not the
>> kind of conformance at which this spec seems to aim (but maybe
>> miss). For exmple the "retention constraint" stuff has absoluely no
>> reason to be a MUST. As another, I think section 5.4 only needs a
>> MUST in step 4 and all the rest are bogus and a bad plan.  Also in
>> 3.1, the text here is often far too prescritpive and I suspect
>> based on only a couple of implementation strategies.  There are
>> many more examples. I think it'd be a good plan to do an editing
>> pass to get rid of as many of the extraneous and unnecessary
>> constraints that are here. Examples feature in other comments, but
>> I've not tried to be exhaustive in spotting all instances of this.
>> 
>> -	I disagree.  In general, I think this language needs to be 
>> normative in order to ensure coherent behavior among nodes of the 
>> network.
> 
> Yep, I figured we'd not see eye to eye on the broader conformance
> issue, in the same way that we've disagreed about that for about a
> decade now:-)
> 
> Nonetheless, I will continue to argue the point, and I note that you
> didn't respond to the examples in the above. Those are only examples,
> but I think some discussion of them may help us to see that the
> current text is (or is not) overly prescriptive.
> 
>> 
>> (C) Many of the flags relaed to reporting provide ways in which the
>>  BP, if it became widely deployed (even if not planned to be widely
>>  used), could be a significant (D)DoS accelerator. Has anyone
>> figured out the scale factors involved, (e.g. if N bogus blocks say
>> report if this can't be processed) whether those might be
>> significant and if so what potential countermeasures might apply?
>> Absent such an analysis, or fixing the problem, I'd argue it'd seem
>> irresponsible to standardise the BP.  I'd say for a PS, the minimum
>> is that BPAs MUST default to not sending all these new bundles
>> except when specifically configured to be so verbose.  This also
>> affects 5.1 and maybe elsewhere which says an agent MUST emit admin
>> bundles if asked. In 5.6, step 2: again the SHOULD needs to be
>> qualified in order to not have the BP be a fine DoS accelerator
>> (given non-singletons). Step 3's SHOULD for this is even worse as a
>> bad actor could include many such blocks.  In 5.13 - I think that
>> is too many custody signals. If one envisages DTNs with custodians
>> located at links that are particularly subject to disruption, then
>> those may be few in number and having all other nodes/routers emit
>> custody signals for each bundle not taken into custody seems hugely
>> inefficient and unnecessary. There may be more examples.  FWIW, my
>> guess is that if all the current reporting is kept, then the IESG
>> will require some kind of applicability statement about the kind of
>> network in which the BP can safely be deployed. For me, fixing the
>> problem is a better approach than constraining it via an
>> applicability statement.
>> 
>> -	I agree with making all status report generation "SHOULD" rather 
>> than "MUST".  But if it is possible to generate status reports (and
>> I think it has to be, for network troubleshooting purposes) then it
>> is always possible for a badly engineered implementation to
>> generate them more frequently than might be optimal in a given
>> network.  I'm unclear on how we can legislate against that.  Strong
>> language warning the implementer of the possible dangers would be
>> fine with me; is that enough?  Something like "Implementations MUST
>> limit the generation of status reports so as to prevent excessive
>> network traffic.  Strategies for limiting status report generation
>> are beyond the scope of this specification."
> 
> I think that a SHOULD for emitting these is just wrong for the
> Internet. If 10^8 BPAs were deployed (there are maybe that many web
> sites) and each by default will emit these reports then that'd be
> just crazy as they could be per-hop and could bounce around all over
> the place. At that scale there'd also no doubt be reports generating
> reports (due to gatewaying even if that was disallowed in the BP) and
> one would get explosions of reports. I think the only defensible
> position is for *all* of these to be specified as "MUST be off by
> default" to be acceptable for a proposed standard.
> 
> I would be ok if someone wanted to try characterise the kind of DTN
> or node(s) in which it'd be ok to have these turned on. That could of
> course be done in a separate document later. (Or outside the IETF if
> it was e.g. really better a CCSDS thing.)
> 
>> 
>> A bit less major (maybe not DISCUSS-worthy) 
>> -------------------------------------------
>> 
>> (1) 3.1's definition of a bundle correctly says that bundles are 
>> better when they include all the meta-data that might be useful. If
>>  considered naively, that conflicts with modern approaches to
>> privacy where we want to ensure that meta-data is only seen by
>> those (nodes) that need to see meta-data, as one form of data
>> minimisation. OTOH, one could argue that such bundles will ensure
>> that meta-data and payloads enjoy the same security services, which
>> is a good thing. In any case, I think it'd be useful to have a
>> discussion about the privacy aspects of the BP, esp the ways in
>> which those may be different from other protocols. For example,
>> would we expect report-to URIs to commonly allow re-identification
>> of a person? I don't recall we've ever really discussed such
>> issues.
>> 
>> -	I think having that discussion would be fine.  I don't think
>> that discussion has to happen in this specification, nor that it
>> has to happen before this specification is published.
> 
> Disagree. I think now is exactly the right time to do a privacy
> analysis. Later will be too late, if the protocol gets deployed at
> scale. Note that I'm not arguing that the result has to be a BP with
> fully understood and perfect privacy features.
> 
>> 
>> (2) 3.1, destination: I think this ought be clear that delivery to
>>  some node in the endpoint represents success, i.e.  that the BP
>> does not force successful delivery to all or failure as a binary
>> choice.
>> 
>> -	The spec doesn't define "success" at all, and I don't know why
>> it would need to.
> 
> Sure, but I was more asking for clarity - I didn't find it to be that
> well explained what kind of effort(s) are expected with endpoints
> containing >1 node.
> 
>> 
>> (3) What bad things would follow if 3.2 was deleted?  It may be
>> that I'm too familiar with DTN (and hence not a good judge if this
>> section is useful or not) but I didn't find it useful. Also - is
>> 3.2 normative? If not, I'm even happier to see it go. If it is,
>> then I gotta wonder if it conflicts with other text later. And I
>> see there are a few 2119 MUSTs in there so I guess you do mean it
>> to be normative or did they sneak in in by accident whilst editing?
>> (As can happen.) If not deleting this section, I'd argue to find
>> all the bits of text in it that are needed and move them all
>> elsewhere and then delete the section.
>> 
>> -	I think 3.2 is essential to the specification.  I'm fine with 
>> moving the 2119 language to another section, if that helps.
> 
> Again, I don't think we'll agree here, as with point (B) above:-)
> 
> I note that you've not given an argument for including 3.2 though
> other than stating that it's essential, and I did ask what'd be lost
> if it were deleted so that seems not highly responsive.
> 
>> 
>> (4) 3.2: The idea that the EID fully determines the MRG seems just
>>  wrong to me. While that might be a nice theory, I figure it's way
>> more likely that the routing scheme determines how many copies of a
>> bundle are rx'd at how many instances of the destination EID.
>> What'd be bad about losing that concept and letting (the
>> determinants of) the MRG be unspecified here?
>> 
>> -	I think that would make the behavior of nodes so indeterminate
>> that it can't be tested.
> 
> I don't get that. Given that we're not defining routing here, aren't
> we in that position already? We can't for example tell if a node
> emitting 10 copies of a bundle at different times, to different next
> hops, on different interfaces etc. is good or bad or not.
> 
>> 
>> (5) 3.2, "Custody of a bundle MAY be taken only if the destination
>> of the bundle is a singleton endpoint." That's plain wrong. Not all
>>  custodians can know about the desitnation being a singleton or
>> not. And before you say it, I don't believe in the flag in 4.1.3
>> that allows an origin to specify this - I've never seen a real
>> example of when that's useful - the only nearby case I recall was
>> where the developer (me:-) knew we wanted distibution to all nodes
>> in a multi-member endpoint but with best effort in terms of getting
>> to them all and with custody and less frequent application layer
>> re-tx's to ensure we got to as many as possible.  This also affects
>> 5.2.
>> 
>> -	"Singleton" doesn't say how many nodes are in the endpoint.  It 
>> says what the maximum number of nodes in the endpoint is.  The
>> source node should know this.
> 
> Huh? How can a source know that in general? I maintain my
> position:-)
> 
>> 
>> (6) 3.3, I'm not sure this is useful either. What'd break if it
>> were deleted? (But then I never liked those bits of DTNRG's work 
>> either;-)
>> 
>> -	Sure, don't care.
> 
> (I'll skip over stuff where there's little or nothing more to say,
> like this one:-)
> 
>> 
>> (7) Including some examples and an RFC 7942 implementation status 
>> section would be a good thing, if easily done. That would help 
>> progression and increase confidence in the correctness of the
>> spec.
>> 
>> -	I don't think this is really necessary, but I don't mind adding
>> an implementation status section.
>> 
>> (8) 4.1.6: Was sub-second timing discussed by the WG?  I'm not 
>> terribly pushed on that myself, but it'd be a shame to do an
>> interop breaking change in the BP without discussing that topic. A
>> reason to think about this is that there may be inter-VM (or
>> intra-data-centre) reasons to consider the BP with sub-second
>> timing as interesting. It'd be a shame to make that impossible just
>> to make it slightly simpler to represent time.
>> 
>> -	It was discussed by the WG, and I believe we concluded that 
>> sub-second time representation wasn't needed here.
> 
> That makes me a bit sad. If anyone else would like sub-second timing
> maybe now'd not be too late if we ask nicely?
> 
>> 
>> (9) 4.2.2, creation time rules: I don't see why it'd be a problem
>> if node-id=X, creation-time=0,counter=0,lifetime=2s is used in two
>>  bundles emitted 3 seconds apart. Why does that justify a MUST NOT
>> in the spec?
>> 
>> -	I agree with Ed on this.  There may be purposes for which a log
>> of bundles may be needed; that's impossible if bundles are not
>> uniquely identified.
> 
> (I'm not sure I saw Ed's argument, I guess it was not on the list,
> sorry if I missed it.)
> 
> I'd be a bit concerned that the MUST NOT is too hard to nodes without
> good clocks and will just be ignored across reboots. If other code
> elsewhere (e.g. log analysis) depended on a fiction from here that'd
> not be great.
> 
>> 
>> (10) 4.2.2: The "30 seconds" rule also seems wrong to me, as is the
>>  "MUST NEVER" (not a 2119 term btw) for re-use of the seq no, which
>> is unrealistic.  As an example of that last: what do you expect to
>> happen with a node that usually knows the wall clock time, but, at
>> this moment, knows that it does not? E.g. previous logs have some
>> real dates, but current clock is 1970-01-01 or whatever. I think
>> this is fixable but the current language is too prescriptive. Best
>> might be to weaken the language here and to see what
>> implementations do in the real world.
>> 
>> -	Sure.
>> 
>> (11) 4.3.1: Is the SHALL here right? I would have thought a SHOULD
>> is better to allow for legacy interop with 5050 via gateways, in
>> which case there may be no node ID. That might be better off
>> handled in some generic fashion though, and not piecemeal with each
>> mention of node ID.
>> 
>> -	There are node IDs in 5050 also,
> 
> Well, sorta but not really. IIRC implementations and deployments
> mostly did include the moral-equivalent but didn't have to.
> 
>> they're just not called by that term.  I think SHALL is correct
>> here.
> 
> But fair enough, if nobody else cared, I'd fold on this one.
> 
>> 
>> (12) 4.3.2: I don't believe it is correct to drop a bundle due to
>> the lack of a previous node block, which is what sems to be implied
>> here. Not all routing schemes need this and so it ought not be a
>> MUST. Maybe a SHOULD is enough, but even if you say "MUST insert
>> this" then I would like to argue that "receivers can decide to not
>> care" be stated explicitly e.g.  by saying that bundles MUST NOT be
>> rejected solely due to the lack of this EB.
>> 
>> -	I think this will be a source of headaches eventually, but sure,
>> we can relax this.
>> 
>> (13) I'm not sure if you have all the right "watch out for the null
>>  EID node ID" text needed. (I didn't go back over everything, but
>> it'd seem wrong e.g. in an current custodian AR.
>> 
>> -	I don't think there's an issue here, but sure, let's re-read
>> with this in mind.
>> 
>> (14) 5.4: "The bundle protocol agent MUST determine which node(s)
>> to forward the bundle to." That's ungrammatical and close to BS -
>> what if I want to multicast or broadcast the bundle or use some
>> other opportunistic CLA? Or a sneakernet where nobody knows who'll
>> be next hop.
>> 
>> -	Of course the BPA must determine which node(s) to forward the 
>> bundle to.  What else is going to make that determination?  Nothing
>> in the spec says it has to make that determination right now; maybe
>> it sets the bundle aside for a while until a data mule comes along
>> - and then it determines that this data mule is one of the nodes to
>> forward the bundle to.  The text is correct.
> 
> Disagree. A BPA might decide to send the bundle on an interface
> that's broadcast in nature and not care who turns out to be the next
> hop that e.g. accepts custody. I think the text reflects a quite
> narrow conception of a CLA.
> 
>> 
>> (15) 5.4: The text about the flow label should be deleted as it
>> says nothing. If includng this, then the flow label spec may need
>> to be a normative ref (arguably).
>> 
>> -	Okay.
>> 
>> (16) 5.4 - I think this is badly misleading. There will be many
>> cases where a bundle cannot be forwarded now but may be forwarded
>> later. Am I wrong in reading this section as precluding that?
>> 
>> -	You are wrong in reading this section as precluding deferred 
>> transmission.
> 
> Maybe it needs rewording then. (Happy to look over it with you 
> later.)
> 
>> 
>> (17) 5.6, step 4 says one MUST handle "custody transfer
>> redundancy" but that term seems undefined.
>> 
>> -	Sure, let's add a clause saying "this condition is termed
>> 'custody transfer redundancy'".
>> 
>> (18) 5.6 (step 5) points back to 5.3 which points to 5.7 or 5.4. I
>>  don't think such GOTOs are a good idea really.  I suggest removing
>>  lots of this and adding in some informative (i.e. non-normative) 
>> pseudo code (or real code) as an appendix.
>> 
>> -	I disagree.
> 
> See point (B) above I guess:-)
> 
>> 
>> (19) I think some rules related to custody and fragmentation may be
>>  missing. For example, if bundle A is multicast and reaches two
>> nodes on different paths who take custody (custodians C1/C2) and
>> who both fragment but differently (into F11/F12 and F21/F22 resp)
>> with eventually a custody ack for F21 reaching C1.  Assume F21 is
>> longer than F11, what is C1 to do with F11 when a custody timer
>> expires? Ought it re-transmit or consider that the custody ack for
>> F21 matched F11 sufficiently well?  I'm not sure what'd be right
>> here, if such cases can happen.  I'd be fine with the spec
>> admitting that some such corner cases exist, or maybe it's easy
>> enough to figure out, not sure.
>> 
>> -	I don't think there is a problem.  Custody transfer is undefined
>> if the destination endpoint is not singleton.
> 
> I wasn't referring to the destination here, C1/C2 are just routers on
> paths to that destination. So I do think there's a problem, sorry.
> 
>> 
>> (20) 5.10.1, I've always wondered why custody timer expiry is
>> covered here, and not really considered a part of DTN routing. It
>> seems to me to make more sense to couple custody timing and
>> routing. If that resonated with folks, I think the change would be
>> to make the timer-related text here into an illustrative example
>> and to say that such things are better considered together with
>> routing and/or by chunks of code that are somewhat more
>> topology/disruption-aware of the situation in the particular DTN.
>> 
>> -	Custodial retransmission really has nothing to do with routing.
> 
> I guess we disagree again there. I'd say with almost all routing
> schemes (CGR and similar being an exception) figuring out the best
> way to handle these timers will be intimately related to routing. See
> also point (B) above:-)
> 
>> 
>> (21) section 9 seems woefully incomplete - why is it ok to say
>> "will be required" at WGLC? Surely the WG should at least have
>> discussed the set of registries needed and the registration rules
>> for those? E.g. do we sill want CCSDS to be able to add entries to
>> some of those registries as we did with 5050?  And has the WG
>> considered how do all the things in this draft relate to the set of
>> IANA registries related to the BP? [1,2] (In the case of [3],
>> section 4.1.5.1 really probably does need to say something.)
>> 
>> -	Sure, let's review what other registries are needed here.
>> 
>> [1] https://www.iana.org/assignments/bundle/bundle.xhtml [2] 
>> https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml#uri-sch
>>
>> 
emes-1
>> 
>> Seemingly more minor or nitty things 
>> ------------------------------------
>> 
>> - abstract: "This Internet Draft" is no longer appropriate
>> language.
>> 
>> -	Sure.
>> 
>> - abstract: I think this ought capture the fact that this version
>> is not interoperable with 5050. That's not a bad thing, but worth
>> noting here.
>> 
>> -	Worth saying, but not in the Abstract.
>> 
>> - intro: I don't think the "sales" language is needed or
>> appropriate in the first couple of paras. It should be entirely ok
>> to say "we've learned stuff and fixed stuff."
>> 
>> -	Sure, whatever.
>> 
>> - intro: "Custodial forwarding" is too terse at this point but also
>>  hard to explain briefly, is really a mechanism and not a
>> capabililty, and maybe not such a highlight, so I'd delete that
>> bullet
>> 
>> -	I disagree.  Let's turn it into a sentence and keep it.
>> 
>> - intro: "[TUT]" is quite outdated and using dtnrg.org for the 
>> reference isn't wise (particularly at the moment when we're seeing
>>  SERVFAIL from the relevant NS;-)
>> 
>> -	Sure.
>> 
>> - intro: this is a bit self-serving, but maybe a reference to the 
>> architectural retrospective [3] that Kevin and I wrote might be
>> useful here, though I've not checked if it touches on enough of the
>> issues behind the differences between 5050 and this.
>> 
>> -	I don't think this is needed.
>> 
>> [3] https://ieeexplore.ieee.org/document/4530739
>> 
>> - Figure 1: I wonder if it'd be worth pointing out that the BP does
>>  not have to run over a layer 4 that runs over a layer 3 etc. The 
>> figure and this text does give that impression that a "proper" 
>> transport is needed, which isn't the case. (Tactically, I'm not
>> sure if the text as-is, or something more correct, would make
>> getting a new RFC easier or harder - I guess it'll depend on the
>> reader;-)
>> 
>> -	No, the spec already says "BP uses underlying "native" transport 
>> and/or network protocols".
>> 
>> - Figure 2: Few if any of the applications I've used with the BP
>> had an administrative element. That's maybe down to the
>> experimental nature of the work we've done but I don't think it's
>> correct to imply that all applications using the BP need to be able
>> to handle admin records, if that's what you're implying. (I'm not
>> sure.) I'd say indicating that that's an optional thing would be
>> right.
>> 
>> -	I disagree.  The application agent -- not the application -- is
>> the thing that has an administrative element.  We could say that a
>> given BPA's application agent might lack an administrative element,
>> in which case the node could not take custody of a bundle.  I don't
>> see much advantage in that, but I don't mind saying it.
>> 
>> - 3.1, singleton: not sure if it's clear enough that all endpoints
>> are sets, so this may puzzle folks. Maybe add e.g. "remember that 
>> endpoints are sets," not sure.
>> 
>> -	Let's assume that people reading this specification are able to 
>> read.
>> 
>> - 3.1, forwarding: the text is odd - "sustained effort" is not 
>> mandatory, and what "that node" is meant here?
>> 
>> -	Nothing says how long "sustained" is, but okay, we could delete
>> the word.  But I have no idea how to make this sentence any
>> clearer. There is exactly one possible antecedent for "that node".
>> 
>> - 4: The first two SHALL statements are odd in that there's no way
>> in which one could implement this spec and not conform to those I
>> think. In cases like that it's fine to avoid 2119 language. Not a
>> big deal though, as the current IESG don't get anal about that,
>> though some ADs in the past have done;-)
>> 
>> -	I think those statements are needed and are not obvious.
>> 
>> - 4: last item MUST be break stop code. Is a decoder supposed to
>> barf a bundle if this is not true? More generally, same question
>> applies for all MUSTs stated only in terms of what the encoding
>> must match.
>> 
>> -	Let's add a general statement, somewhere, to the effect that the 
>> bundle protocol agent MAY discard any malformed bundle it
>> receives.
>> 
>> - 4.1.1: why >1 CRC type? That seems bogus. None or strong seems 
>> better to me. (And I'd go for a crypto hash for strong.) I assume
>> the WG discussed this and found that there are real use-cases for
>> each of those specified. While those don't need to be in the spec,
>> can someone tell me what they are as I'm not at all sure, e.g. why
>> a 16 bit CRC is useful as an option.
>> 
>> -	The WG discussed this and settled on these options.  See email
>> list traffic starting on 18 January 2016.
>> 
>> - 4.1.3: "enables anonymous bundle transmission" - that's
>> overstated, chances are that something in the CLA will be
>> identifying, or allow re-identification, so I think what you want
>> to say is that omitting the source EID helps with, but does not
>> ensure, nymity.
>> 
>> -	"Anonymous" doesn't mean you can't figure out who did it. 
>> "Anonymous" means the identity of whoever did it was not attached
>> to it.  The text is correct as written.
> 
> Disagree. The term anonymous has a meaning which is not that.
> 
>> 
>> - 4.1.5.1: RFC3986 is the correct reference here, so the spec text
>> is correct as-is. It may however be worth taking a look at the
>> whatwg web page that has sometimes claimed to supercede 3986 for
>> the browser-related things in which whatwg have an interest.
>> That's just in case there're some useful error handling
>> considerations on the whatwg web page, (on the day you look at
>> it;-). It's also the case that since BP EIDs are URIs, it's
>> possible that strings that comply with today's or yesterday's
>> whatwg web page may end up in the BP, so it'd be good to know if
>> any of those (that are not valid according to 3986) might cause a
>> problem with the CBOR encoding.
>> 
>> -	If the text is correct, let's leave it.  If someone discovers
>> that it is in error for one or more of the reasons proposed, then
>> let's fix it.
>> 
>> - 4.1.5.2: Danger, metaphysics! "Every node MUST be a member of at
>>  least one singleton endpoint." This entire section is
>> over-thought. I think all you need to say is that nodes the emit
>> bundles need to have an EID they can use as a source EID for as
>> long as necessary.
>> 
>> -	I disagree.  The section is exactly enough-thought.
> 
> See point (B) above:-) And "exactly"? :-)
> 
>> 
>> - 4.2.1: this entire section is duplicative. That's a bad idea.
>> 
>> -	If the text that it duplicates can be identified then we should 
>> remove the duplication.
>> 
>> - 4.2.2: 2nd para is badly written - that'd encourage coders to use
>>  the values 8,9,10 and 11 in ways that might be unwise.
>> 
>> -	The text says nothing about using any values in any manner, for 
>> good or ill.   It only says how many elements are in the array.
>> 
>> - 4.2.2: wrt "anonymous" see earlier comment
>> 
>> -	Correct as written, as noted above.
>> 
>> - 4.2.2: description of creation time is duplicative, except the 
>> earlier text didn't cover relative time.
>> 
>> -	This section is not duplicative, it is expansive.
>> 
>> - 4.3.3: Is "Bundle Age Block" a good name? BAB used to mean
>> another type of block, so that could confuse maybe. (That said, I
>> forget how long we're had this name.)
>> 
>> -	There are no longer any Bundle Authentication Blocks.  "Bundle
>> Age Block" is a good name.
>> 
>> - 4.3.4: Do you need to say that the hop limit MUST NOT be changed,
>>  once a hop count EB is added. Also, can any node add one of these,
>> if one was not prevsiously present?
>> 
>> -	I agree, this needs to be clarified.
>> 
>> - 5: It's not necessary to say that new RFCs can supercede this. 
>> That's just standard IEFF process.
>> 
>> -	I don't see what harm this does.  For someone who is not steeped
>> in standard IETF process, but wants to read the specification
>> anyway, maybe it would be useful information.
>> 
>> - 5.2: mentions "dispatch pending" as if I should know what that is
>> - is all the retention constraint stuff sufficiently explained I
>> wonder? (Personally I don't think you need to mandate all this
>> stuff and you cannot tell if an implementation has done it or not
>> so I'd not bother trying to be so prescriptive.)
>> 
>> -	All of the retention constraint stuff is explained in detail.  I 
>> think it's necessary in order to ensure coherent behavior among the
>>  nodes of the network.
> 
> See point (B) above:-)
> 
>> 
>> - 5.4: "at the last possible moment... MUST..." that's a bit silly
>> as it seems to require BP code inside a NIC which is not how
>> this'll usually be implemented.
>> 
>> -	I don't understand the objection.  "Last possible moment" is
>> very clearly in the scope of the operation of the CLA, which is BP
>> code. If that happens to be embedded in a NIC, fine, but that's not
>>  relevant.
>> 
>> - 5.5: I'm not convinced that the MUSTs here are right for all
>> DTNs. I reckon that 5.5 could just as well say "MAY delete" and the
>> BP would be fine. That might also provide some additional
>> flexibility for some rounting schemes. That said, I won't press on
>> this - if this doesn't resonate with folks now, and later turns out
>> to be useful, I don't think we'd have such a hard time modifying
>> BPAs where needed.
>> 
>> -	Here again I think the normative language is necessary in order
>> to ensure coherent behavior among the nodes of the network.
> 
> See point (B) above.
> 
>> 
>> - 5.6: Again, this is overly prescriptive.
>> 
>> -	I disagree, again because the normative language is necessary in 
>> order to ensure coherent behavior among the nodes of the network.
>> 
> 
> See point (B) above.
> 
>> - 5.6, step 4: I wonder if an implementer will get all this right.
>> 
>> -	It has been implemented.  The implementation works fine.
> 
> Yeah, but you've been doing this for ages, it's a new implementer we
> need to consider, starting from the RFC.
> 
>> 
>> - 5.9: Badly implemented, re-assembly can create a memory
>> consumption DoS vector, perhaps esp. if attempted on a
>> non-destination node. It'd be better to warn about that. And maybe
>> change from MAY for in-path reassembly to SHOULD NOT.
>> 
>> -	I am doubtful that this specification should be a compendium of 
>> implementation tips.
> 
> s/MAY/SHOULD NOT/ is way more than a tip
> 
>> 
>> - 5.11: does this mean that a custodian MUST ignore a custody
>> signal destined for some other custodian?
>> 
>> -	This text does not imply that the receiving node must ignore a 
>> custody signal destined for another custodian.  It means exactly
>> what it says, and no more.
>> 
>> - Figure 6: I don't get when reason codes 5 to 8 would really be
>> used. Are they in fact needed?  (They seem a bit implementation
>> specific to me, but I've not gone looking.)
>> 
>> -	DTNRG thought these codes would be needed.  Let's get more 
>> deployment experience before deciding that they are not.
>> 
>> - section 8: First sentence is bogus.
>> 
>> -	Not bogus, but not necessary.  Sure, let's delete it.
>> 
>> - section 8: [SECO] isn't a good reference. It's outdated and I
>> doubt will be picked up.
>> 
>> -	Okay.
>> 
>> 
>> 
> 
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