Subject: [Simple] Infinite loops in rls subscriptions

From: <[email-masked]>
Date: Fri, 19 May 2006 10:58:49 +0200

Hi, 

in draft-ietf-simple-event-list-07 is written:

7.4 Infinite Loops

   One risk introduced by the ability to nest resource lists is the
   possibility of creating lists which ultimately contain themselves as
   a sub-list.  Detection and handling of such a case is trivial when
   the RLS services all of the virtual subscriptions internally.  When
   back-end subscriptions are created to service virtual subscriptions,
   however, detection of such situations becomes a more difficult
   problem.
   Implementors of RLSes that create back-end subscriptions MUST
   implement safeguards to prevent such nestings from creating an
   infinite loop of subscriptions.  Typically, such mechanisms will
   require support in the back-end subscription protocol.  In
   particular, applying filters to the back-end subscriptions can be an
   effective way to preclude such problems.

I have 2 questions:
- if an user performs rls subscription and RLS detects loop in virtual
subscriptions, should it break the cycle and keep the rls subscription
active, or reject the rls subscription?

- it seems to me that it is not possible to detect loops in back end
subscriptions (subscriptions between different servers). If I have list
in RLS1 which contains reference to list in RLS2, and the list in RLS2
contains reference back to the list in RLS1, there is no way (provided
by standards) how to detect this loop, because the back-end subscription
coming from RLS2 to RLS1 wont carry any hint that it is related to
preceding back-end subscription from RLS1 to RLS2. Am I correct? 

Thanks, 

Silvestr Peknik
Software Specialist
TietoEnator

_______________________________________________
Simple mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/simple