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:[email protected]] On Behalf Of Luigi Iannone
Sent: Monday, March 09, 2015 10:22 AM
To: LISP mailing list list
Cc: [email protected]
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
[email protected]
https://www.ietf.org/mailman/listinfo/lisp
