Subject: [VIPR] PVP entropy

From: Marc Petit-Huguenin <[email-masked]>
Date: Sun, 04 Sep 2011 13:53:01 -0700

Section 10.1 of the -pvp draft is an empty section that is supposed to describe
how to aggregate entropy.  The idea is that the fact that one validation
succeeds could not be enough for a remote VIPR server to give back routes and
ticket for this destination.  For example a site could decide that 3 different
calls validated with method "b" are needed to let a SIP call reach the endpoint.

This proposal describes a mechanism for PVP to implement this.  The idea is that
when a PVP validation succeeds, the PVP server will return a ticket[1] but may
not return the list of routes if the entropy threshold is not reached.  The
ticket will contain an opaque value set by the PVP server that contain the level
of entropy that this caller has reached.  The PVP client stores the ticket but
does not notify the call agent as there is no routes available.  The next time
the PVP client has a successful validation with the same destination, it sends
the saved ticket in addition to the domain.  The PVP server then evaluates the
ticket, increases the entropy value stored and send back a new ticket back.  If
the threshold has been reached, then the PVP server sends back the routes at the
same time, routes that the PVP client can now send with the ticket to the call
agent.

When renewing the routes/ticket, the PVP client also sends the existing ticket,
so the PVP server can decide to lower the threshold based on the entropy
collected the previous time and the date of the ticket.

This can be combined with my proposal for method priority.  If multiple methods
are available for a destination but the first that succeeds does not return the
routes then the PVP client can use the next available methods in the list to try
to increase the entropy and receive them.

A PVP server may even use different thresholds, depending on the domains to
validate.  This become then an extension to the white/black list, where a
blacklist is implemented as a default threshold of X and a infinite threshold
for the domains blacklisted, and where a whitelist is implemented as a default
infinite threshold and a threshold of X for the domains whitelisted.

[1] Or a certificate if my other proposal is accepted.

- -- 
Marc Petit-Huguenin
Personal email: [email-masked]
Professional email: [email-masked]
Blog: http://blog.marc.petit-huguenin.org