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Gemini G3 - User Manual
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Appendix 4 - Time Synchronisation, and WEB Browser Cache - Instructions
The contents of this appendix are also available in Technical Instruction Sheet 051 (TIS051), dated No-
vember 10, 2006.
Overview
The instructions in TIS051, intended for maintenance technicians and for end-users, address a built-in
web server synchronization and browser cache issue where web pages of a unit may contain information
that does not seem to match the expected content, especially after a firmware upgrade.
The following paragraphs detail the cause of the problem and steps to prevent the problem.
Likely Cause
Most web browsers store the pages they display in a browser cache, so that the next time the same page is
displayed, the browser does not have to download it all over again from the server. The browser instead
displays the version of the page that was previously stored in the cache.
This process relies on a combination of factors to establish whether a page can be retrieved from the
cache or must be freshly downloaded from the server. Typically, they are:
♦
The IP address of the server
♦
The time and date the page was last updated on the server.
Unless your unit was configured to pick up and maintain time-of-day (section 4.7.3.7), its time and date
restarts from the same point (typically, 1970-01-01 00:00:00*) after each reset or power-up. In this condi-
tion, the timestamp applied to web pages during a firmware upgrade might predate the timestamp of the
pages already in the browser's cache. When next accessing the pages in question, the browser will pickup
the cached version, as it appears to be newer than that of the freshly upgraded unit.
* Encoded system time using the number of one-second ticks elapsed since the start of the “epoch”
set at 1970-01-01 00:00:00 Z.
Problem Prevention
In order to avoid picking up stale data, it is strongly recommended that you empty the browser's cache
before starting to browse the web content of a unit, following a software update, and when going from
one unit to another.
Enabling time-of-day synchronization
(on units that support it)
will also help prevent this problem.
Cache Clearing
If using Internet Explorer v6.0, select “Tools” in the menu bar, select “Internet Options”, select the “Gen-
eral” tab and click on the “Delete Files” button in the “Temporary Internet files” pane; click on the “OK’
button to confirm the deletion and on the OK button to exit.
If using Mozilla Firefox v1.5.0.4, select “Tools” in the menu bar and select the “Clear Private Data” op-
tion. Alternately, you can use the keystroke combination of “Ctrl+Shift+Delete”.
Adjust the above methods according to your browser or to its version number.