Subject: [Sipping] RE: Comments on sip-guid-00

From: "Brian Stucker" <[email-masked]>
Date: Sun, 29 Feb 2004 20:16:02 -0600

I think you're leaving a key element out of your argument of how unique this
type of mechanism is. UAs are not envisioned to be generating these IDs on a
whim, really it's something that they do at build time (ie embedded into the
hardware perhaps, ala MAC, etc) or something they do at installation time
(soft phone, etc). 

Because of this, I believe the uniqueness is much higher than you've
calculated because in your example, all of those billion UA's would have to
have been installed within that 15 minute period as well, typically. This is
highly unlikely to ever occur, and furthermore, if it should ever occur, I'd
be willing to eat my hat (given that the odds of me being struck dead by a
meteorite or dying of old age are vastly more likely). =)

Regards,

Brian

-----Original Message-----
From: Eric Burger [mailto:[email-masked]]
Sent: Sunday, February 29, 2004 1:50 PM
To: Stucker, Brian [NGC:B617:EXCH]
Cc: Sipping (E-mail)
Subject: Comments on sip-guid-00

First, a statistics issue.  I disagree that the time, in of itself, has
quite the properties asserted.  For example, given a billion UA's, if they
have a 15-minute clock drift with a Normal distribution, well over 3,000 of
them will think it is the same time in any given 5-minute window.

That is still pretty good odds, but not the one-in-a-trillion asserted.
This gets worse if the UA's have random number generators that have a
correlation with their notion of time (e.g., time is used as a salt, boot at
the same time with the same salt, etc.).  [Yes, I did Monte Carlo
simulations a lifetime ago...]

The text goes through the algorithm for generating a GUID, but then the
example has what looks like an IP address in it.  Is that a proper
interpretation?  Where does the 10.33.15.8 come from?

---

From: "Eric Burger" <[email-masked]>
Date: Sun, 29 Feb 2004 21:23:58 -0500

Agreed :-)

-----Original Message-----
From: Brian Stucker [mailto:[email-masked]]
Sent: Sunday, February 29, 2004 9:16 PM
To: Eric Burger
Cc: Sipping (E-mail)
Subject: RE: Comments on sip-guid-00

I think you're leaving a key element out of your argument of how unique this type of mechanism is. UAs are not envisioned to be generating these IDs on a whim, really it's something that they do at build time (ie embedded into the hardware perhaps, ala MAC, etc) or something they do at installation time (soft phone, etc). 
Because of this, I believe the uniqueness is much higher than you've calculated because in your example, all of those billion UA's would have to have been installed within that 15 minute period as well, typically. This is highly unlikely to ever occur, and furthermore, if it should ever occur, I'd be willing to eat my hat (given that the odds of me being struck dead by a meteorite or dying of old age are vastly more likely). =)
Regards, 
Brian 
-----Original Message----- 
From: Eric Burger [mailto:[email-masked]] 
Sent: Sunday, February 29, 2004 1:50 PM 
To: Stucker, Brian [NGC:B617:EXCH] 
Cc: Sipping (E-mail) 
Subject: Comments on sip-guid-00 

First, a statistics issue.  I disagree that the time, in of itself, has quite the properties asserted.  For example, given a billion UA's, if they have a 15-minute clock drift with a Normal distribution, well over 3,000 of them will think it is the same time in any given 5-minute window.
That is still pretty good odds, but not the one-in-a-trillion asserted.  This gets worse if the UA's have random number generators that have a correlation with their notion of time (e.g., time is used as a salt, boot at the same time with the same salt, etc.).  [Yes, I did Monte Carlo simulations a lifetime ago...]
The text goes through the algorithm for generating a GUID, but then the example has what looks like an IP address in it.  Is that a proper interpretation?  Where does the 10.33.15.8 come from?

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