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

"Joel M. Halpern" <> Tue, 01 May 2018 16:58 UTC

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To: Tom Herbert <>
Cc: Tom Herbert <>,, 5GANGIP <>
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From: "Joel M. Halpern" <>
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Date: Tue, 01 May 2018 12:58:55 -0400
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Subject: Re: [Ila] [5gangip] ILA forwaring [Was Re: Problem Statement]
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If you do not use caches in your ILA-Ns (and yes, I understand your 
reasoning for not doing so), then you are constructing an overlay 
network.  One of the arguments I was given for using ILA was to enable 
direct forwarding of packets effectively without needing to have routing 
track the moving entities.  Without caches, you are pushing all the 
traffic through fewer entities.  And you seem to be either using a lot 
of ILA-R with concomitant information distribution or few ILA-R 
restricting the information distribution problem but instead having 
traffic concentration problems.

I understood from your earlier presentation that the ILA-r using the 
packet as a signal was to avoid dropping the first packet, and as a 
side-effect not needing a separate query message.
Now you seem to be saying that your think it important to support not 
having caches in the ILA-Ns, which is a VERY different trade-off.


On 5/1/18 12:37 PM, Tom Herbert wrote:
> 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.
> Joel,
> 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).
> Tom