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ExNet NTP Services

As a service to the Internet at large, ExNet makes available NTP V3 time service.

NTP is a protocol for distributing time across a network, easily, cheaply and reliably, to all manner of machines including end-user desk-top machines. This is useful to ensure that systems that work together, eg file servers and compute servers involved in a make build, or used to timestamp a financial transaction, or as part of a security mechanism, `chime' together---that is they are closely synchronised to one another and to the correct time. The NTP mechanism is robust and partially self-organising, and its ultimate source of time is from national standards (eg atomic clocks maintained by national standards laboratories) usually picked up via radio receivers (eg via GPS).

To quote from the NTP-V3 RFC (1305):

NTP provides the mechanisms to synchronize time and coordinate time distribution in a large, diverse internet operating at rates from mundane to lightwave. It uses a returnable-time design in which a distributed subnet of time servers operating in a self- organizing, hierarchical-master-slave configuration synchronizes local clocks within the subnet and to national time standards via wire or radio. The servers can also redistribute reference time via local routing algorithms and time daemons.

Contents

Conditions of Use

There is no charge for this service (we're glad to return a favour to the Net), though we would like you to ask before using our server, partly so we can make sure it does not get overloaded. We will enter your details in the list below if you use our server, partly so that other people can contact you to peer at the next stratum down if appropriate (please send us your name, email address, a URL if appropriate, and the address and stratum of a machine you are happy for others to synchronise to if you have such a machine by email or use the form below). Please synchronise only one of your hosts to any one of our servers, and use a recent XNTP implementation, to keep the load on our servers and lines to a minimum. We reserve the right to withdraw or alter the service without notice, and make no warranties of any kind about its usability. Send all mail to dhd@exnet.com. All that said, enjoy!

(PS. Feel free to `test-drive' our stratum-2 server to make sure it will work for you before emailing.)

We have been running XNTP for a few years now, and do have some external sites synching to us, but those users predate this page and so do not appear in the lists of users below.

Request ExNet NTP Service

You're most welcome to our ntp service, but the current situation is:

  • ntp.exnet.com is currently overloaded; we are working on a solution (ie upgrading the machine), but it may take a while. You are welcome to contact us again in a couple of months.
  • If you are going to synchronise a group of more than about 10 or more machines from the one that you synchronise to us, you may use ntp1.exnet.com (our stratum-1 server) instead.

Please observe our restrictions on use: our servers are complaining about the various loads they're carrying and that has an impact on the service that we give to our paying customers; they must be given priority.

Please submit the following form to us for publication on this website:

Contact Name:

Contact Email Address:

Company or Organisation:

Comments

URL:

Country:

Machines:

(The set of machines being synched -- eg, *.ThisCompany.com)

Address and Stratum:

(The machine on your site to which other people can synchronise)

Service Details

In the past we have run a stratum-1 clock, and will do again when we can.

There are two machines available (sometimes they will be the same server):

  • ntp.exnet.com nominally at stratum 2
  • ntp1.exnet.com nominally at stratum 1
These names are DNS aliases (CNAMES) and you should use those names rather than IP addresses where possible since the IP addresses may change.

Note that you will not necessarily be able to interrogate these machines with tools such as ntpq since access from ports other than the (privileged) NTP server port may be blocked by our firewall.

Note that in the absence of all lower-stratum servers, ntp.exnet.com will regard itself as a high-stratum (10 or greater) server free-running on its own clock. This is primarily so that it can go on providing some co-ordination to our internal machines. If this proves to be a problem for any external users, please tell me. Similarly ntp1.exnet.com will fall back to stratum 8 or greater in case of failure of its radio clocks.

Before trying to use our NTP server(s), please contact us with the details requested above plus the IP address of the machine you will synch from; we will ensure that your traffic is allowed through our firewalls. We will not disclose your IP address if you do not want other people to use it.

ExNet is based in the south-west of London. Greenwich, of GMT fame, is not very far away in the south-east of London. According to our GPS receiver ExNet HQ (or, more accurately, the antenna) is at 51.4154N 0.2921W.

NTP Peers of ntp.exnet.com(2)

As at 1997/05/21, ntp.exnet.com has the NTP peers listed below (the number in brackets indicates the stratum at which we expect them them to be running). The people and organisations concerned are outstanding examples to us all! B^)
  • ARCRON MSF radio clock at stratum 1.
  • swisstime.ethz.ch(1) Zürich, Switzerland.
  • canon.inria.fr(1) Rocquencourt (near Paris), France.
  • bear.zoo.bt.co.uk(2/1) * British Telecom Labs, Ipswitch?, UK.
  • cuckoo.uk0.vbc.net(2) * VBC Net, Telehouse (East London), UK.
  • chime.MCS(2) * Chicago, IL, US.
  • ntp.adelaide.edu.au(2) Adelaide, (South) Australia.
  • ntp.olivetti.com(2) Cupertino, CA, US.
  • LOCAL(9) (local clock as fallback)
Servers marked * are not apparently open-access public servers, so please be especially diligent in checking with the owners before considering using these servers directly, or eschew using them altogether.

Registered Users of ntp.exnet.com(2)

Unless one or more hosts are explicitly listed at the end of each line above, please assume that there are no publicly-available NTP servers for you to synch to.

NTP Peers of ntp1.exnet.com(1)

As at 1997/12/31, ntp1.exnet.com has the NTP peers listed below (the number in brackets indicates the stratum at which we expect them them to be running). The people and organisations concerned are outstanding examples to us all! B^)
  • Trimble Placer 400 GPS radio clock at stratum 0.
  • ARCRON MSF radio clock at stratum 1.
  • swisstime.ethz.ch(1) Zürich, Switzerland.
  • ntp0.nl.net(1) Amsterdam, Netherlands.
  • utcnist.microsoft.com(1) Redmond, WA, US.
  • LOCAL(7) (local clock as fallback)
Servers marked * are not apparently open-access public servers, so please be especially diligent in checking with the owners before considering using these servers directly, or eschew using them altogether.

Registered Users of ntp1.exnet.com(1)

Entry For Public Secondary NTP Servers List

  1. ntp.exnet.com
    Location: ExNet Ltd, London, UK; 51.4154N 0.2921W.
    Synchronization: NTP V3 secondary (stratum 2), Linux
    Service area: UK/Europe/any
    Access policy: semi-open access, please send message first
    Contact: dhd@exnet.com
    Note: Please see our Web page before using. Please use CNAME ntp.exnet.com since IP address may well change.

NTP Resources

Other NTP/time resources and links that you may find useful.

Author's Note

I hope this is of some use to you; let me know.

Regards,

Damon


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