An open discussion list for topics related to the eduGAIN interfederation service.

[Tomasz Wolniewicz <twoln AT umk.pl>]

Hi Nick,

   I have no objections of course. Please share it with whoever you like.

Tomasz



W dniu 14.09.2016 o 21:53, Nick Roy pisze:
> Hi Tomasz, do you mind if I share this with the InCommon Technical
> Advisory Committee for their thoughts?
>
> Thank you,
>
> Nick
>
> On 9/14/16 10:03 AM, Tomasz Wolniewicz wrote:
>> Hi All,
>>     Here I am, reopening this thread. Sorry for the length of what
>> follows.
>>
>> A quick summary first.
>> The current "hard" approach to eduGAIN aggregation is that if we spot a
>> validation error then we mark the entire feed as broken and reject it.
>> There have been voices in this thread pointing out that rejecting an
>> entire feed of hundreds of entities because of a single offending entity
>> is much too harsh and that perhaps eduGAIN MDS should filter out
>> individual entities instead. This mail is primarily addressed to
>> supporters of this "soft" approach.
>>
>> I am a strong advocate of the "hard" approach so I will put together my
>> views why this is good and "soft" is bad, I am sure there will be
>> opposite opinions as well. I will not hide that my true intention is to
>> convince the SG to the decision supporting the "hard" solution and have
>> this subject closed for at least a year.
>>
>> Pros for "hard".
>>
>> a) eduGAIN metadata profiles specifies the requirements for a correct
>> feed and does not have a notion of a semi-correct one. Accepting
>> something which is not correct and making decisions on what can be fixed
>> and how should not be something for the central aggregator to do.
>>
>> b) This approach is clear and not open to any interpretations.
>>
>> c) The "hard" approach does not do any real harm - if we stick to the
>> rule that ValidUntil should not ever drop below 4 days, the federation
>> should have plenty of time to fix the feed before the cached copy might
>> be dropped.
>>
>> d) This approach is very easy to implement, but perhaps this should not
>> be a deciding factor.
>>
>> Cons against "soft". These really are the questions that automatically
>> pop up, for which we will need to invent answers (read - new
>> regulations).
>>
>> a) If we decide that a single entity can be dropped, what do we do if
>> there are 2, 3, 100? Where is the limit?
>>
>> b) How long do we tolerate errors in a feed, should there be a time
>> limit or do we just let it run indefinitely? If we set the limit, will
>> the situation be that much different from having this time limit being
>> equal to 0 which is another formulation of the "hard" approach.
>> Eventually the limit will arrive and then what - drop the whole feed on
>> the floor and leave nothing?
>>
>> c) If a federation feed suddenly has corrupt data about an entity that
>> previously was OK what do we do? Keep the correct copy of this entity in
>> metadata or simply drop it? We definitely cannot keep the entity longer
>> than the validUntil of the last correct metadata feed, therefore to keep
>> we would have to implement per-entity valid-until counters and separate
>> per-entity warnings. This makes the system quite complex.
>>
>> d) The "soft" solution supports a lax approach to the way that
>> federation cooperate within eduGAIN and we should not encourage that.
>>
>> Cheers
>> Tomasz
>>
>

-- 
Tomasz Wolniewicz    
          twoln AT umk.pl        http://www.home.umk.pl/~twoln

Uczelniane Centrum Informatyczne       Information&Communication Technology 
Centre
Uniwersytet Mikolaja Kopernika         Nicolaus Copernicus University,
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