Thanks for reminding me. I had indeed forgotten. On Thu, Oct 26, 2017 at 10:55 AM, Donald Eastlake <[email protected]> wrote:
> Hi Eric, > > I realize that most of the delay has been on the TRILL WG end but I hope > you don't mind if I ping you again on looking at the -09 revision of this > draft... > > Thanks, > Donald > =============================== > Donald E. Eastlake 3rd +1-508-333-2270 <(508)%20333-2270> (cell) > 155 Beaver Street, Milford, MA 01757 USA > <https://maps.google.com/?q=155+Beaver+Street,+Milford,+MA+01757+USA&entry=gmail&source=g> > [email protected] > > On Mon, Oct 9, 2017 at 7:05 PM, Donald Eastlake <[email protected]> wrote: > >> Hi Eric, >> >> A -09 version of draft-ietf-trill-arp-optimization has been posted. >> Could you look at it to see if it resolves your comments? >> >> Thanks, >> Donald >> =============================== >> Donald E. Eastlake 3rd +1-508-333-2270 <(508)%20333-2270> (cell) >> 155 Beaver Street, Milford, MA 01757 USA >> <https://maps.google.com/?q=155+Beaver+Street,+Milford,+MA+01757+USA&entry=gmail&source=g> >> [email protected] >> >> On Mon, Oct 2, 2017 at 2:12 PM, Eric Rescorla <[email protected]> wrote: >> >>> >>> >>> On Mon, Oct 2, 2017 at 4:54 PM, Donald Eastlake <[email protected]> >>> wrote: >>> >>>> Hi Eric, >>>> >>>> My apologies for the delay in response. (For part of the time I was on >>>> a cruise...) >>>> >>>> It looks like we are in agreement on most items. >>>> >>>> See below. >>>> >>>> On Fri, Sep 22, 2017 at 9:18 AM, Eric Rescorla <[email protected]> wrote: >>>> > >>>> > >>>> > On Wed, Aug 23, 2017 at 12:38 PM, Donald Eastlake <[email protected]> >>>> wrote: >>>> >> >>>> >> Hi Eric, >>>> >> >>>> >> On Wed, Jul 5, 2017 at 7:38 AM, Eric Rescorla <[email protected]> wrote: >>>> >> > Eric Rescorla has entered the following ballot position for >>>> >> > draft-ietf-trill-arp-optimization-08: Discuss >>>> >> > >>>> >> > ------------------------------------------------------------ >>>> ---------- >>>> >> > DISCUSS: >>>> >> > ------------------------------------------------------------ >>>> ---------- >>>> >> >>>> >> As a general comment, the Security Consideration section could use >>>> >> clarification and some expansion. >>>> >> >>>> >> Although one can imagine various mixed modes, to the first >>>> approximation >>>> >> there are two ways of doing the optimization of various >>>> multi-destination >>>> >> messages discussed in this document: >>>> >> >>>> >> + Using data plane learning by observing ARP/ND and similar messages >>>> (in >>>> >> addition to the learning of MAC addresses from the data plane which >>>> is >>>> >> enabled by default in TRILL). As described in this document, such >>>> data plane >>>> >> learning by TRILL switches can be used to sometimes optimize >>>> >> ARP/ND/RARP/unknown-destination messages. But the result isn't >>>> particularly >>>> >> more or less secure than it is when this data plane learning is done >>>> by end >>>> >> stations rather than by TRILL switches (or bridges or other kinds of >>>> >> switches) in the middle doing some optimization of the relevant >>>> >> multi-destination messages. Interface address information learned >>>> through >>>> >> data plane learning by edge TRILL switches can also be propagated >>>> via the >>>> >> control plane but this is not significantly different from >>>> propagating that >>>> >> information via the multi-destination messages that are being >>>> optimized to >>>> >> unicast or optimized away. >>>> >> + Using a complete, trusted directory as might be based on an >>>> orchestration >>>> >> system in a data center. Since the messages between TRILL switches >>>> doing >>>> >> ARP/ND/RARP/unknown-destination optimization can be secured and the >>>> TRILL >>>> >> switches can be configured to ignore data plane learning, this >>>> enables TRILL >>>> >> switches to provide answers that are "correct" in that they >>>> correspond to >>>> >> the data in this complete, trusted directory. However, there can >>>> still be >>>> >> various forged messages/addresses on a local link between end >>>> station(s) and >>>> >> edge TRILL switches. Such a local link can, with TRILL, be a bridged >>>> LAN, so >>>> >> such forgeries emitted by an end station may be seen by other end >>>> stations >>>> >> and cause incorrect learning from the data plane. >>>> >> >>>> >> The existing Security Considerations section is a bit sketchy and >>>> >> concentrates more on the data plane case, as that is the one with the >>>> >> greatest security challenges. >>>> > >>>> > Yes, this seems like a reasonable assessment. Alia, does someone have >>>> the >>>> > action item to make it less sketchy? >>>> >>>> We are working on a draft revision to reflect the above thinking to a >>>> greater extent and decrease sketchiness. >>>> >>>> >> > It's not clear to me how the security properties of this mechanism >>>> >> > compare to existing TRILL. The text says: >>>> >> > >>>> >> > Unless Secure ND (SEND [RFC3971]) is used, ARP and ND messages >>>> can be >>>> >> > easily forged. Therefore the learning of MAC/IP addresses by >>>> RBridges >>>> >> > from ARP/ND should not be considered as reliable. See Section >>>> 4.1 for >>>> >> > SEND Considerations. >>>> >> > >>>> >> > "not considered as reliable" seems suboptimal. You need to cover >>>> how >>>> >> > this mechanism compares to the non-use of this mechanism. >>>> >> >>>> >> As above, the optimization mechanisms do not make any significant >>>> >> difference to the inherent insecurities of data plane learning but >>>> when used >>>> >> with a complete, trusted directory, it improves considerably over >>>> data plane >>>> >> learning.. >>>> > >>>> > That had kind of been my impression, but then I don't understand what >>>> "not >>>> > considered as reliable" is doing here. I'm supposed to be doing >>>> something >>>> > with it, so while it may be non-secure, I'm still relying on it, no? >>>> >>>> Well, at some level some elements of your protocol stack are "relying" >>>> on it or "trusting" it or whatever term you want, but it's trivially >>>> forged unless you use additional security protocols so I guess we >>>> could say something about that. TRILL supports different link >>>> technologies but if you are using an Ethernet link, I suppose you >>>> could use 802.1AE to improve trust in MAC addresses at layer 2. It >>>> wouldn't hurt to mention that but it has very little to do with ARP/ND >>>> optimization or TRILL. >>>> >>> >>> I think if you just sort of say "you are using it, but it's not >>> trustworthy and here's why" you have it covered. >>> >>> -Ekr >>> >>> >>>> >> > This document seems very sketchy on what you do when you get >>>> duplicate >>>> >> > IPs. >>>> >> >>>> >> Why should what you do when you notice a duplicate IP address be >>>> >> significantly different just because some multi-destination messages >>>> are >>>> >> being optimized? Why shouldn't you just do whatever you do now and >>>> why is >>>> >> that any of TRILL's business? >>>> > >>>> > Because you're getting the information via different vector, TRILL >>>> needs to >>>> > specify what you do, >>>> > if only to say "do what you would do otherwise". >>>> >>>> OK. >>>> >>>> >> > In the case where the former owner replies, a Duplicate Address >>>> has >>>> >> > been detected. In this case the querying RBridge SHOULD log the >>>> >> > duplicate so that the network administrator can take appropriate >>>> >> > action. >>>> >> > >>>> >> > How does logging solve the problem? >>>> >> >>>> >> It doesn't but it seems better than not logging. >>>> >> >>>> >> > What do you reply to ARPs with and/or propagate to other nodes? >>>> >> >>>> >> If you are asking how you reply to ARPs if the IP address being >>>> ARPed for >>>> >> has been found to be duplicated, there are the two cases outlined >>>> above. If >>>> >> you are using a complete, trusted directory, you give the presumed >>>> correct >>>> >> answer provided by that directory. If you are using data plane >>>> learning, you >>>> >> use whatever you last learned from the data plane (which could have >>>> been a >>>> >> forgery over writing good information or good information over >>>> writing a >>>> >> forgery or a forgery overwriting a different forgery or ...). >>>> >> >>>> >> > Do you tell the originator of the advertisement you have a >>>> duplicate? >>>> >> >>>> >> As far as I know there is no standardized way to tell a station that >>>> you >>>> >> think it has an IP address that is duplicated locally and I don't >>>> think it >>>> >> is the job of TRILL to provide such a mechanism. Certainly this >>>> document >>>> >> does not propose anything of that sort. >>>> > >>>> > OK. >>>> > >>>> > >>>> >> > When a newly connected end-station exchanges messages with a >>>> DHCP >>>> >> > [RFC2131] server an edge RBridge should snoop them (mainly the >>>> >> > DHCPAck message) and store IP/MAC mapping information in its >>>> ARP/ND >>>> >> > cache and should also send the information out through the TRILL >>>> >> > control plane using ESADI. >>>> >> > >>>> >> > What happens if the attacker sets up a fake DHCP server and >>>> pretends >>>> >> > to assign addresses to himself? It seems like maybe that's the same >>>> >> > as fake ARPs but maybe not. >>>> >> >>>> >> This snooping on DHCP messages only applies to the data plane >>>> learning >>>> >> case. In the case of a complete, trusted directory, edge RBridges >>>> already >>>> >> know the right answer, so to speak. With data plane learning, if >>>> there are >>>> >> forged DHCP messages, things are likely to get all screwed up. Of >>>> course, >>>> >> you could run DHCP over IPsec but, partly due to the localized >>>> nature of >>>> >> DHCP, I don't think very many people do that. There is also RFC 3118 >>>> which >>>> >> can be used to authenticate DHCP messages, but that assumes the >>>> distribution >>>> >> of keying information. >>>> >> >>>> >> There isn't much difference between the various multi-destination >>>> messages >>>> >> (ARP / DHCP) advertising the addresses and point of attachment of >>>> >> interfaces. But, overall, I'm not sure why a document that is just >>>> >> describing ways to optimize the distribution of various >>>> multi-destination >>>> >> messages needs to analyze the security of the protocols implemented >>>> by those >>>> >> multi-destination when, as in the data plane learning case, it is not >>>> >> significantly changing that security. >>>> > >>>> > Well, in this case, you have a new threat vector: DHCP. Even if it is >>>> the >>>> > same kind of threats, it's still a new threat vector. >>>> > More generally documents need to contain complete security >>>> considerations >>>> > sections. If the security considerations >>>> > are the same as with some other document, then they need to say that. >>>> >>>> OK. >>>> >>>> >> > In general, the security considerations need a complete threat >>>> >> > analysis per 3552. >>>> >> >>>> >> I don't think there is that much new in this document. While the >>>> Security >>>> >> Considerations section needs clarification and some expansion, I >>>> don't think >>>> >> it is, for example, the job of this document to do a threat analysis >>>> of the >>>> >> ARP protocol as long as it can make a reasonable case that the >>>> security of >>>> >> ARP is not significantly changed by the optimizations specified. >>>> > >>>> > Sure, but it also doesn't make that case. >>>> >>>> I'll see what we can do. >>>> >>>> >> > ------------------------------------------------------------ >>>> ---------- >>>> >> > COMMENT: >>>> >> > ------------------------------------------------------------ >>>> ---------- >>>> >> >>>> >> For completeness, I've cut and pasted below the COMMENT responses I >>>> sent >>>> >> to you a while ago. >>>> >> >>>> >> Thanks, >>>> >> Donald >>>> >> =============================== >>>> >> Donald E. Eastlake 3rd +1-508-333-2270 (cell) >>>> >> 155 Beaver Street, Milford, MA 01757 USA >>>> <https://maps.google.com/?q=155+Beaver+Street,+Milford,+MA+01757+USA&entry=gmail&source=g> >>>> >> [email protected] >>>> >> >>>> >> > S 2. >>>> >> > >>>> >> > plane on the edge RBridges, it should be possible to completely >>>> >> > suppress flooding of ARP/ND messages in a TRILL Campus, When >>>> all end- >>>> >> > station MAC addresses are similarly known, it should be >>>> possible to >>>> >> > suppress unknown unicast flooding by dropping any unknown >>>> unicast >>>> >> > received at an edge RBridge. >>>> >> > >>>> >> > Are these "should be possibles" normative? Descriptive? >>>> >> >>>> >> Section 2 of this document is a general discussion of the >>>> optimization >>>> >> problem which, while it does mention a couple of possible facets of >>>> >> potential solutions, is not intended to be normative. >>>> >> >>>> >> >>>> >> > S 4. >>>> >> > This is a sequence of steps, so it would be nice to preface them >>>> with >>>> >> > a list of the steps. It's also odd to have SEND considerations >>>> right >>>> >> > in the middle here. >>>> >> >>>> >> Sorry, I don't understand exactly what you are pointing at as a >>>> >> sequence of steps. All of Section 4? Just the text between the >>>> Section >>>> >> 4 heading and the Section 4.1 heading? Something else? >>>> > >>>> > Sorry, my point is that if I read this correctly, I do 4.3, then 4.4, >>>> etc. >>>> > It would be nice if they were listed ahead of this as "this is what >>>> you do, >>>> > now read the sections" >>>> >>>> OK. We can add some clarifying material to Section 4 before the 4.1 >>>> heading. >>>> >>>> >> > 4.3 Get Sender's IP/MAC Mapping Information for Non-zero IP >>>> >> > >>>> >> > Please explain what a non-zero IP is and why it's relevant. >>>> >> > This graf also needs an introductory sentence or something before >>>> >> > the bullets. >>>> >> >>>> >> Here is a copy of the response that was sent to a similar comment in >>>> >> Dale Worley's GENART review: >>>> >> >>>> >> This section is talking about getting and handling the IP/MAC >>>> >> mapping information for a local end station by an edge RBridge. An >>>> >> ARP/ND from such a local end station might show a zero source IP >>>> >> address if the end station does not have one or is probing for >>>> >> duplicates. >>>> >> >>>> >> Perhaps the title for the Section should be something like >>>> >> >>>> >> 4.3 Extracting Local End Station IP/MAC Mapping Information >>>> >> >>>> >> and a new first paragraph could be added something like >>>> >> >>>> >> Edge RBridges extract and use information about the correspondence >>>> >> between local end station IP and MAC addresses from the ARP/ND >>>> >> messages those end stations send as described below. An apparent zero >>>> >> source IP address means that the end station is probing for duplicate >>>> >> IP addresses and messages with such a zero source IP address are not >>>> >> used for the extraction of IP/MAC address mapping information >>>> > >>>> > LGTM >>>> > >>>> > >>>> >> > S 4.4. >>>> >> > It is not essential that all RBridges use the same strategy for >>>> which >>>> >> > option to select for a particular ARP/ND query. It is up to the >>>> >> > implementation. >>>> >> > >>>> >> > This seems inconsistent with the MUST in arm (b) below, because I >>>> >> > can just take some other arm. It's also kind of surprising to be >>>> this >>>> >> > non-prescriptive. >>>> >> >>>> >> The wording needs to be clarified. Which lettered item listed below >>>> >> applies is determined by the circumstances; however, which of the >>>> >> numbered strategies associated with these items is followed is an >>>> >> implementation choice in handeling any particular ARP/ND. >>>> > >>>> > OK. >>>> > >>>> > >>>> >> > S 8. >>>> >> > some other location (MAC/VM Mobility) and gets connected to >>>> egde- >>>> >> > >>>> >> > Nit: edge is mispelled. >>>> >> >>>> >> OK. >>>> >>>> Thanks, >>>> Donald >>>> =============================== >>>> Donald E. Eastlake 3rd +1-508-333-2270 (cell) >>>> 155 Beaver Street, Milford, MA 01757 USA >>>> <https://maps.google.com/?q=155+Beaver+Street,+Milford,+MA+01757+USA&entry=gmail&source=g> >>>> [email protected] >>>> >>> >>> >> >
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