Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]

Tom Herbert <> Tue, 01 May 2018 16:38 UTC

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From: Tom Herbert <>
Date: Tue, 01 May 2018 09:37:54 -0700
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To: "Joel M. Halpern" <>
Cc: Tom Herbert <>, Christian Huitema <>,, 5GANGIP <>
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Subject: Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]
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On Tue, May 1, 2018 at 9:10 AM, Joel M. Halpern <> wrote:
> Three reactions, all personal opinion (in case someone thinks my having
> helped chair the BoF is in any way relevant; it isn't):
> 1) If ILA-Ns do not have caches, the ILA-Rs will become hot-spots in the
> network.  Yes, you have provision for multiple of them sharing load.
> However, if that sharing gets to be a significant percentage of teh routers
> in the network, then there is no point in having bothered with ILA, you are
> just routing on the SIR.

If you provision a network (or any system really) based on an
assumption that caches will always attain some hit rate this is a
fundamental mistake. One of the goals of a DOS attack would be to
drive the hit rate to zero in which case someone will be in a world of
hurt. Caches and DOS are a hard mix to contend with in nearly any
context, that's why it's much better to view caches as an optimization
rather than a requirement. They can be used to alleviate load, but
that cannot be relied upon.

I would also point out that caches only make sense as internal devices
for intra domain communications. This does not make sense for edge
routers that would need to create a working set cache for any
aribtrary load of traffic from the Internet.

> 2) As far as I can tell, when some ILA-N have caches, the ILA-R have no way
> of knowing whether the ILA-N have caches or not.  I can understand what
> happens if all ILA-N in a network have the same cache state (either they all
> have caches or they all do not have caches).  But I do not know what
> behavior you expect of an ILA-R if the ILA-N are not uniform. Given the
> hot-spot issue above, I think you need to really explain why ILA-N would not
> ahve caches.
ILA-Rs and ILA-Ns communicate via ILAMP protocol. That can include
capabilities description.

> 3 - Minor) Your usage of "sharding" seems odd.  You are simply dividing the
> domain into address blocks, and distributing responsibility for those blocks
> separately.  In other contexts, sharding seems to be used more generally for
> having subcollections of the data which can be moved around.
Sharding is a database term that describes partitioning of the
database into smaller chunks for manageablibilty. That is what is
happening here (literally in the implementation since we are use a
database backend).