nanog mailing list archives
Re: Question on Loosely Synchronized Router Clocks
From: "Robert E. Seastrom" <rs () seastrom com>
Date: Mon, 17 Sep 2007 20:48:04 -0400
"Xin Liu" <smilerliu () gmail com> writes:
Sorry for the confusion. Let me clarify. We are interested in a number of questions: 1. Can we assume loosely synchronized router clocks in the Internet, or we have to make absolutely no assumption about router clocks at all?
Make no assumption.
2. If the router clocks are indeed loosely synchronized, what is the granularity we can assume? Particularly, we are interested in whether we can assume router clocks are synchronized within 10 minutes.
It's not even a fair assumption that all routers have clocks (as in wall time / time of day or year clocks, not CPU clocks).
3. It's always possible that a router's clock goes wrong. In practice, how often does this happen?
Let's suppose you were writing software for a router and you wanted it to behave in a certain fashion if its clock were out of sync with some time standard, say for the sake of argument, TAI. How would the software in this router go about determining that it was out of sync with standard time? ---Rob
Thank you for all the replies. Best Regards, Xin Liu On 9/17/07, Randy Bush <randy () psg com> wrote:i conversed offline with the OP. he was reading a sigcomm research paper and confusing it with the internet. randy
Current thread:
- Re: Question on Loosely Synchronized Router Clocks, (continued)
- Re: Question on Loosely Synchronized Router Clocks Steven M. Bellovin (Sep 18)
- Re: Question on Loosely Synchronized Router Clocks Adrian Chadd (Sep 18)
- Re: Question on Loosely Synchronized Router Clocks William Herrin (Sep 18)
- Re: Question on Loosely Synchronized Router Clocks Stephen Sprunk (Sep 18)
- Re: Question on Loosely Synchronized Router Clocks Jeff McAdams (Sep 19)
- Re: Question on Loosely Synchronized Router Clocks James R. Cutler (Sep 20)
- Re: Question on Loosely Synchronized Router Clocks Brandon Galbraith (Sep 20)
- Re: Question on Loosely Synchronized Router Clocks Steven M. Bellovin (Sep 20)
- RE: Question on Loosely Synchronized Router Clocks Buhrmaster, Gary (Sep 20)
- Re: Question on Loosely Synchronized Router Clocks Janet Sullivan (Sep 17)
- Re: Question on Loosely Synchronized Router Clocks Robert E. Seastrom (Sep 17)
- Re: Question on Loosely Synchronized Router Clocks Stephen Sprunk (Sep 18)
- Re: Question on Loosely Synchronized Router Clocks bmanning (Sep 19)
- Re: Question on Loosely Synchronized Router Clocks Deepak Jain (Sep 17)
- Re: Question on Loosely Synchronized Router Clocks Kevin Oberman (Sep 17)