[ntp:questions] ntpdate.c unsafe buffer write

Unruh unruh-spam at physics.ubc.ca
Tue Feb 12 17:08:04 UTC 2008


Martin Burnicki <martin.burnicki at meinberg.de> writes:

>Dave,

>David L. Mills wrote:
>> Serge,
>> 
>> The behavior after a step is deliberate. The iburst volley after a step
>>   is delayed a random fraction of the poll interval to avoid implosion
>> at a busy server. An additional delay may be enforced to avoid violating
>> the headway restrictions. This is not to protect your applications; it
>> is to protect the server.

>Is it really necessary to insert a random delay after a step? There has
>already been a random delay immediately after startup, before the client
>has decided that a step was required.

>So even if a bunch of clients started up at the same time and had to step,
>they wouln't step at the same time, and thus wouldn't do the next iburst
>volley at the same time anyway.

Why not? The power comes on on your computer farm of 2000 machines, all the clients are the same type so the
bootup sequence is identical. They all start ntp at the same time, to
within a second or so. And suddenly the poor server is flooded. 

>Martin
>-- 
>Martin Burnicki

>Meinberg Funkuhren
>Bad Pyrmont
>Germany




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