On Apr 30, 2009, at 2:19 PM, DePriest, Greg (NBC Universal) wrote:
Thanks to Enrico and Nicholas for providing additional background and
explanations.
The key point of disagreement seems to be that adding a content
protection requirement to ALTO would "hugely complicate and compromise
the design of
ALTO."
I'm not an expert in such matters, have very limited exposure to the
area, and can't help but wonder if that is, in fact, correct.
Was there a serious investigation or did someone simply do a
back-of-the-envelope analysis.
For me, its "Intuition backed up by a threat analysis and usage cases":
We have legitimate uses which requires ID churn: its the only way to
guarantee that a rebalancing is fresh. Especially since nodes churn
all the time, and ALTO may not have notification when nodes leave.
We have legitimate uses which require IDs to be arbitrary (rather than
representative hashes): ALTO is not just for file distribution, but
other P2P optimization (eg, optimizing for low latency for DHTs) where
hashes don't have meaning. ALTO doesn't want to deal with particular
P2P protocols, which all may have different representations of what
data or blocks are. And doesn't want to deal with colliding
namespaces from different P2P programs. Thus defining ID as a UUID or
other opaque identifier means ALTO doesn't have to deal with these
problems.
We have legitimate uses which require IDs to be creatable at-will by
any party: Otherwise, ALTO becomes an admission only system which
limits utility.
Yet all three decisions (allowing churn, opaque-data IDs, at-will ID
creation) and there becomes an easy countermeasure to ANY system
predicated on "block bad IDs", as long as that system has a slower
response time than the P2P network you are trying to prevent
optimizing its communication, and you can't do "only allow good IDs"
if IDs are creatable at-will by any party.
And "if a defense has a trivial countermeasure, don't bother deploying
it".
Thus this means the only way to make ALTO "content protecting" is to
remove one of those three constraints. But all three features are
very valuable in a localization service.
Additionally, there is a large bias in the network community in
general to be "content neutral". Any time you cease to be content
neutral on the technical level, it must necessarily impose constraints
and costs on the system.
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