[ntp:questions] Number of sockets in NTP

Danny Mayer mayer at ntp.isc.org
Fri Jul 4 16:02:27 UTC 2008

Kiran Shirol wrote:
> Hi,
> I am wondering why do we need to open one socket per interface in the
> system.
> In a very large setups with huge number of interfaces, NTP can potentially
> open large number
> of sockets.  What is the motive and the advantages of opening one socket per
> interface ?
> Can we not do away with just the wildcard sockets ?

No, it not as simple as that. Because NTP uses UDP there is no 
previously established connection to respond on. There are a number of 
other reasons to avoid using wildcards, including autokey and firewalls 
which expect responses to packets from the same address to which the 
outgoing packet was sent.

There is code that will allow you to specify which IP addresses to open 
and which to send queries out on but it's not yet available while we 
resolve some configuration questions. See 
http://support.ntp.org/bin/view/Dev/NtpdAndNetworkSockets for what we 
are looking at doing.

Note that this issue has been extensively discussed and you should find 
them in the archives.


More information about the questions mailing list