Answers to Chapter Review Questions

     
A1:

Yes, anyone can set up a Stratum-2 timeserver. The University of Delaware maintains a list of all current Stratum-1 and Struatum-2 timeservers (as well as being the repository for the current versions of the NTP software). The University has published, on its Web site, Rules of Engagement, which dictate what is required to be a recognized, publicly accessible Stratum-2 timeserver. The Rules of Engagement is a form of NTP etiquette that everyone involved in NTP agrees to adhere to. Legally, there is little the University of Delaware could do if someone in a distant corner of the Internet decided to flout these rules, except make widely known their abhorrent behavior and ensure that everyone using NTP avoids such rogues at all costs.

A2:

The answer, technically, has to be "it depends." If you are simply looking to make sure that all the machines in the network use the same time, then you could use a local clock impersonator, which may not be correct in relation to TIA, but it means that all machines read the same time. In mission-critical situations or where human life is at risk, not knowing the correct time may be life threatening . In such situations, it is important to have a correct and reliable time source.

A3:

From the given information, we cannot say which server we will synchronize with, because ntpdate will contact all available servers and choose the most appropriate one. When making a change to our system clock, ntpdate has the ability to move our system clock backward in time. This can be problematic , especially for some human-critical or financial applications, e.g., financial applications where the recording of the current time against particular transactions can have significant financial implications. The ntpdate command can slew time (the “B option) whereby a step-change is not performed but future time adjustments are made very slowly. The xntpd daemon has a similar behavior (with the “x option).

A4:

Server clock001 is acting as our clock source. Both servers are broadcasting time packets on their networks (the t = type field: b = broadcast). Server clock001 is a Stratum-2 server (st = 2 field) and has been selected as our clock source because the delay field (showing network round-trip time) is lowest .

A5:

Fudging is the notion of changing particular attributes of a clock source. One of the most common uses of fudging is to fudge the stratum level of a clock source, e.g., a local clock impersonator to more properly reflect the reliability of the clock source.



HP-UX CSE(c) Official Study Guide and Desk Reference
HP-UX CSE(c) Official Study Guide and Desk Reference
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 434

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net