[ntp:questions] ISP bloked port 123

unruh unruh at invalid.ca
Wed Sep 18 16:37:11 UTC 2013

On 2013-09-18, Bert G?tterup Petersen <BUP at bang-olufsen.dk> wrote:
> David,
> I understand that a Raspberry-Pi would do the trick, and I am sure that would work  for everyone reading this.
> However, to our customers and installers this would be rather invasive. They are buying/installing a TV not an IT system..
> Our accuracy requirement are not impressive, merely to allow the product to talk to our cloud service (UTC +-5min).
> Our assumption is that some ISP block the port to prevent their customers from running a public NTP server.

Again, is the ISP blocking outgoing or incoming port 128. Preventing
servers is incoming but that should not prevent outgoing queries to an
ntp server. 

> At the moment our best bet seem to be using 'ntpdate' on a different port at regular intervals. From a SW perspective, this is not nice nor elegant, but it would do the trick...

That uses the same outgoing port. 
Using it on a different port would mean that the server has to respond.
So you would have to use your own servers to give the time. 
Mind you for +- 5 min, this solution once aweek should be fine. 

> Cheers
> Bert

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