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I was just reading up on Kerberos and realized that the lifetime of a master ticket called the TGT(ticket granting ticket) is 25 hours. Is there any particular reason behind this choice of lifetime?

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according to technet.microsoft.com/en-us/library/bb742516.aspx the lifetime is 10 hrs. Where does it say that it is 25 ? –  sudhacker Nov 13 '12 at 3:45
    
over here, "itservices.stanford.edu/service/kerberos/user_guide/how"; –  uki Nov 13 '12 at 4:09
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Judging by the fact that you've taken information from Stanford's IT services, it goes to show that, the lifetime of a ticket is dependent on where it is deployed. ~10 hours is the standard in most cases since it is the average working time in an office environment. Whereas Stanford may afford to have it 25 hrs. –  sudhacker Nov 13 '12 at 4:32
    
@eQuiNoX__ Btw, your link is broken by the ". itservices.stanford.edu/service/kerberos/user_guide/how –  Henning Klevjer Nov 14 '12 at 7:01

1 Answer 1

The Kerberos (v5) RFC does not specify a lifetime but recommends nothing more than 25 hours life for each ticket (section 8.2) and a renewal time of max. one week. There is probably no good answer here as to why Stanford chose to break that recommendation.

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Okay -- but any thoughts on why "25 hours" was chosen? Seems a bit odd to me. –  uki Nov 13 '12 at 12:21
    
No, really no idea. Long hours at Stanford? Being a university, I would guess they have actually discussed and written down somewhere why they chose 25, but finding out who did or where could be a problem. –  Henning Klevjer Nov 13 '12 at 12:25
    
My assumption would be that they made it just long enough that they could renew a ticket for the next day before expiry. Just a guess. –  Rory Alsop Nov 13 '12 at 17:30

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