Re: [lisp] WG Last Call draft-ietf-lisp-impact-01

[Damien Saucez <[e-mail]>]

On 31 Mar 2015, at 19:48, Ronald Bonica <[e-mail]> wrote:

> Damien,
> 
> In his email below, Joel asks:
> 
>>>> if we modified the section to say that we do not know
>>>> what the impact on cache size and control overhead will be, as the
>>>> studies that have been made have been disputed as to their relevance
>>>> to the core Internet case, would the document still meet the IESG
>>>> requirements for evaluating the impact
> 
> I support Joel's request, so long as the disclaimer is complete. If cache size and control overhead have impact, they must have impact upon something.


I don’t see the point of an explicit disclaimer.  By definition when we give
hypothesis it means that results are limited to these hypotheses.  If we have
to put an explicit disclaimer in this document, it means that ALL IETF
documents based on experimentation/implementation should have such disclaimer,
but also any research document!

For me page 4 is explicit enough with the assumptions and I don’t see the point
to add a disclaimer.

The assumptions in these studies are:

o  contiguous addresses tend to be used similarly and EID prefixes
  follow the current BGP prefixes decomposition;

o  EIDs are used only at the stub ASes, not in the transit ASes;

o  the RLOCs of an EID prefix are deployed at the edge between the
  stubs owning the EID prefix and the providers, allocating the
  RLOCs in a Provider Aggregetable (PA) mode.

> Do we know what they will impact? If so, tell us. If not, tell us that.

This is the exact reason why [CCD12] is referenced. It shows that the impact
is on miss rate (see page 5). Also as it is a public analytical study, people can
adapt it relatively easily (as opposed to a traffic trace that is not available to
the community).

Damien Saucez 
> 
>                                                                                                                       Ron
> 
>> -----Original Message-----
>> From: Damien Saucez [mailto:[e-mail]]
>> Sent: Monday, March 30, 2015 7:19 PM
>> To: Ronald Bonica
>> Cc: Joel Halpern; Brian Haberman; BRUNGARD, DEBORAH A (ATTLABS); LISP
>> mailing list list
>> Subject: Re: [lisp] WG Last Call draft-ietf-lisp-impact-01
>> 
>> Ron,
>> 
>> As one of the authors I can say I am not frustrated :-)
>> 
>> We are looking on how to address in the best way the comments of this
>> thread.
>> 
>> Just that it is unrealistic to hope a new full study on the cache size from
>> research partners as such a study takes a lot of time and resources (to
>> produce the experimentation, then to get reviewed in a conference or
>> journal and finally get published) and would not change any conclusion with
>> regards to the analytical studies reference in the draft already and that draw
>> general conclusions.
>> 
>> The best solution could be to ask your customers to provide me the
>> necessary information so that I could evaluate the impact of LISP for their
>> needs. Without that, I am afraid that the only thing that we can reasonably
>> provide is theoretical/analytical studies.
>> 
>> The disclaimer you propose to add is just incorrect. It is not true that we
>> don't know the impact of cache size. Actually, in the draft, we already
>> reference the analytical study [CCD12] that demonstrates analytically that it is
>> possible to link cache size, traffic pattern, and miss rate.
>> 
>> Here is the paragraph present in the draft:
>> 
>> [CCD12]  generalizes the caching discussion and proposes an analytic
>> model for the EID-to-RLOC cache size when prefix-level traffic has a
>> stationary generating process.  The model shows that miss rate can be
>> accurately predicted from the EID-to-RLOC cache size and a small set
>> of easily measurable traffic parameters, meaning that operators can
>> provision the EID-to-RLOC cache of their ITRs according to the miss
>> rate they want to achieve for their given traffic.
>> 
>> That is clear enough for me and unless someone can prove the model wrong
>> I am perfectly fine with this observation that is supported by empirical data.
>> 
>> Cheers,
>> 
>> Damien Saucez
>> 
>> On 30 Mar 2015, at 17:17, Ronald Bonica <[e-mail]> wrote:
>> 
>>> Brian, Deborah,
>>> 
>>> I realize that the authors are frustrated. Maybe we can run with Joel's
>> proposal if we make the disclaimer complete.
>>> 
>>> Shouldn't the disclaimer read something like, "We do not know the impact
>> of cache size and control overhead on {x, y, z}", where x, y and z might be:
>>> 
>>> - LISP scaling
>>> - LISP security
>>> - LISP resiliency
>>> - other ???
>>> 
>>> Given that, might we draw some conclusions regarding LISP's applicability?
>>> 
>>>                       Ron
>>> 
>>>> -----Original Message-----
>>>> From: lisp [mailto:[e-mail]] On Behalf Of Joel M.
>>>> Halpern
>>>> Sent: Sunday, March 29, 2015 9:55 PM
>>>> To: Brian Haberman; BRUNGARD, DEBORAH A (ATTLABS)
>>>> Cc: LISP mailing list list
>>>> Subject: Re: [lisp] WG Last Call draft-ietf-lisp-impact-01
>>>> 
>>>> Brian, Deborah, if we modified the section to say that we do not know
>>>> what the impact on cache size and control overhead will be, as the
>>>> studies that have been made have been disputed as to their relevance
>>>> to the core Internet case, would the document still meet the IESG
>>>> requirements for evaluating the impact.  I don't want to ask the
>>>> authors if they can live with a certain change if that change will
>>>> cause other necessary reviewers to complain.
>>>> 
>>>> I do not see it as sensible to hold up the publication of this and
>>>> the other LISP work while researchers go off to see if they can calculate
>> better results.
>>>> Particularly not when publishing this document is required to do other
>> work.
>>>> 
>>>> Yours,
>>>> Joel
>>>> 
>>>> On 3/29/15 9:50 PM, Ross Callon wrote:
>>>>> I suppose that there are two options:
>>>>> 
>>>>> 1. Admit that we have no clue what the cache size or control
>>>>> overhead will be.
>>>>> 
>>>>> 2. Repeat the cited studies, but with a pessimistic (worse case)
>>>>> rather than optimistic (better than best case) assumption about
>>>>> cache granularity.
>>>>> 
>>>>> The second option would allow us to actually have some idea what
>>>>> would happen if LISP were deployed on an Internet-wide scale, but
>>>>> would of course take more time and more work.
>>>>> 
>>>>> Ross
>>>>> 
>>>>> PS: I will be offline at meetings all of this week, so I might be a
>>>>> bit slower to respond for the next few days.
>>>>> 
>>>>> -----Original Message----- From: Joel M. Halpern
>>>>> [mailto:[e-mail]] Sent: Sunday, March 29, 2015 9:36 PM
>> To:
>>>>> Ross Callon; Luigi Iannone; LISP mailing list list Cc:
>>>>> [e-mail] Subject: Re: [lisp] WG Last
>>>>> Call
>>>>> draft-ietf-lisp-impact-01
>>>>> 
>>>>> Putting aside the TBD (which of course needs to be fixed),  I have
>>>>> trouble figuring out what you want us to say about the main issue in
>>>>> your review.  On the one hand, this is the very issue that we have
>>>>> been asked to comment on, and on the other hand you say that we
>>>>> don't know. What do you think it is reasoanble to say?
>>>>> 
>>>>> Yours, Joel
>>>>> 
>>>>> On 3/29/15 9:03 PM, Ross Callon wrote:
>>>>>> Generally I think that this document needs more work before it will
>>>>>> be ready to submit for publication. Some comments on
>>>>>> draft-ietf-lisp-impact-01:
>>>>>> 
>>>>>> First of all, I assume that the TBD at the end of section 3 will be
>>>>>> fixed. This reads:
>>>>>> 
>>>>>> TBD: add a paragraph to explain the operational difference while
>>>>>> 
>>>>>> dealing with a pull model instead of a push.
>>>>>> 
>>>>>> Also in section 3, the third paragraph begins:
>>>>>> 
>>>>>> In addition, Iannone and Bonaventure [IB07] show that the number of
>>>>>> 
>>>>>> mapping entries that must be handled by an ITR of a campus network
>>>>>> 
>>>>>> with 10,000 users is limited to few tens of thousands, and does not
>>>>>> 
>>>>>> represent more than 3 to 4 Megabytes of memory.
>>>>>> 
>>>>>> Reference [IB07] is of course:
>>>>>> 
>>>>>> Iannone, L. and O. Bonaventure, "On the cost of caching locator/id
>>>>>> mappings", In
>>>>>> 
>>>>>> Proc. ACM CoNEXT 2007, December 2007.
>>>>>> 
>>>>>> This paper states:
>>>>>> 
>>>>>> In our analysis, we assume that the granularity of the
>>>>>> 
>>>>>> EID-to-RLOC mapping is the prefix blocks assigned by
>>>>>> 
>>>>>> RIRs. We call it /BGP granularity. In particular, we
>>>>>> 
>>>>>> used the list of prefixes made available by the iPlane
>>>>>> 
>>>>>> Project [15], containing around 240,000 entries. Using
>>>>>> 
>>>>>> /BGP granularity means that each EID is first mapped
>>>>>> 
>>>>>> on a /BGP prefix. The cache will thus contain /BGP
>>>>>> 
>>>>>> to RLOC mappings.2 This is a natural choice, since
>>>>>> 
>>>>>> routing locators are supposed to be border routers.
>>>>>> 
>>>>>> The authors should be aware that there is some aggregation /
>>>>>> summarization being done in the operation of BGP routing, and that
>>>>>> the granularity of routes which appear in the default-free BGP
>>>>>> routing tables is fundamentally different from the granularity of
>>>>>> enterprise network / ISP boundaries across which traffic is
>>>>>> exchanged.
>>>>>> 
>>>>>> The same paragraph cites Kim et al.  [KIF11], which is Kim, J.,
>>>>>> Iannone, L., and A. Feldmann, "Deep dive into the lisp cache and
>>>>>> what isps should know about it", In Proc.  IFIP Networking 2011, May
>> 2011.
>>>>>> From this document:
>>>>>> 
>>>>>> In addition, we use a local BGP prefixes
>>>>>> 
>>>>>> database, fed with the list of BGP prefixes published by the iPlane
>>>>>> Project [17].
>>>>>> 
>>>>>> The database is used to group EID-to-RLOCs mappings with the
>>>>>> granularity of
>>>>>> 
>>>>>> existing BGP prefixes, because, as for today, there is no
>>>>>> sufficient information
>>>>>> 
>>>>>> to predict what will be the granularity of mappings in a
>>>>>> LISP-enabled Internet.
>>>>>> 
>>>>>> I agree that "there is not sufficient information to predict what
>>>>>> will be the granularity of mappings in a LISP-enabled Internet".
>>>>>> However, not knowing what the mapping granularity will be does not
>>>>>> justify using an extremely optimistic guess, and then acting as if
>>>>>> the results are meaningful. These assumptions are clearly off by
>>>>>> some number of orders of magnitude, but how many orders of
>>>>>> magnitude is unknown. We will note that the current internet
>>>>>> default-free routing table includes a few hundred thousand entries
>>>>>> (roughly twice the
>>>>>> 240,000 entries that existed when this study was done).
>>>>>> 
>>>>>> For example, we might assume that the intended global deployment
>>>>>> model involves xTRs at the boundary between enterprise networks
>> and
>>>>>> service providers, and might note that there are several million
>>>>>> companies in the USA alone (most of these are relatively small
>>>>>> companies, of course). Thus there may be very roughly on the order
>>>>>> of a hundred million or so companies worldwide. If each one had a
>>>>>> separate entry in the mapping table, then the number of entries
>>>>>> will be nearly 1,000 times larger than BGP-prefix granularity.
>>>>>> 
>>>>>> Section 4 mentions as one possible use of LISP: "enable mobility of
>>>>>> subscriber end points". If individual end points are advertised
>>>>>> into LISP, then the granularity of the mapping table may be on the
>>>>>> order of individual systems. In this case the number of mapping
>>>>>> table entries that could exist globally might be on the same order
>>>>>> of magnitude as the number of people in the world, or very roughly
>>>>>> 7 Billion entries. This would suggest that the mapping table might
>>>>>> be roughly 30,000 times finer grained than was assumed in the
>>>>>> referenced studies.
>>>>>> 
>>>>>> I don't see how we can accurately predict the control plane load of
>>>>>> LISP without some sense for what the granularity of the mapping
>>>>>> table will be. It should however be possible to bound the control
>>>>>> plane load. The referenced studies give a lower bound on possible
>>>>>> control plane load (it won't be any less), but give neither an
>>>>>> accurate measurement nor an upper bound on the potential control
>>>>>> plane load. I don't think that the document can claim to explain
>>>>>> the impact of LISP without there being an attempt to measure an
>>>>>> upper bound on the control plane load.
>>>>>> 
>>>>>> Finally, perhaps I missed it but I didn't see any discussion of the
>>>>>> volume of overhead related to OAM traffic used for liveness
>>>>>> detection (the need for ITR's to determine the reachability of ETR's).
>>>>>> 
>>>>>> Thanks, Ross
>>>>>> 
>>>>>> *From:*lisp [mailto:[e-mail]] *On Behalf Of *Luigi
>>>>>> Iannone *Sent:* Monday, March 09, 2015 10:22 AM *To:* LISP mailing
>>>>>> list list *Cc:* [e-mail] *Subject:*
>>>>>> [lisp] WG Last Call draft-ietf-lisp-impact-01
>>>>>> 
>>>>>> Hi All,
>>>>>> 
>>>>>> the authors of the LISP Impact document
>>>>>> [https://tools.ietf.org/html/draft-ietf-lisp-impact-01] requested
>>>>>> the Work Group Last Call.
>>>>>> 
>>>>>> This email starts a WG Last Call, to end March 30th, 2015.
>>>>>> 
>>>>>> Because usually the pre-meeting period is already overloaded, the
>>>>>> LC duration is set to three weeks.
>>>>>> 
>>>>>> Please review this updated WG document and let the WG know if you
>>>>>> agree that it is ready for handing to the AD.
>>>>>> 
>>>>>> If you have objections, please state your reasons why, and explain
>>>>>> what it would take to address your concerns.
>>>>>> 
>>>>>> Any raised issue will be discussed during the WG meeting in Dallas.
>>>>>> 
>>>>>> Thanks
>>>>>> 
>>>>>> 
>>>>>> Luigi & Joel
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> _______________________________________________ lisp
>> mailing
>>>> list
>>>>>> [e-mail] https://www.ietf.org/mailman/listinfo/lisp
>>>>>> 
>>>>> 
>>>> 
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