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A quick look at some of the inner workings of IE7’s RSS ability

May 4th 2006 in Uncategorized

I think its worthwhile sharing some off the inner workings of IE7’s RSS ability.  There have apparently been expressions of concern about the demand that may be placed on RSS services once everybody (aka IE users) has easy access (which reminds me of the old “AOL ruined the internet” argument – now some are worried IE7 will ruin RSS). 

Some concerns expressed relate to:

. Frequency of updates
. Traffic spikes
. Technical issues on a server
. Feeds that no longer exist

Let’s have a look at some of the inner workings of IE7 relevant to the above:

Frequency of updates:  IE7 enforces a minimum 15 minute break between updates.  In addition, feed publishers can enforce a longer minimum through the use of the TTL tag.  It is important to note that IE7 will ony enforce the TTL tag for automatic synchronization. Manual refreshing overrides it.

Traffic spikes:  Internet Explorer uses a process called “salting” to try and alleviate traffic spikes.  After a successful download IE7 will set the next download time for a feed as the time of successful download plus the user’s predefined interval plus a random fraction of that interval thereby “staggering” refresh times.
Feed experiencing technical issues:  Internet Explorer 7 uses a progressive back-off algorithm. Instead of retrying every couple of seconds when unable to access a feed, IE7 will double the retry interval after each failed refresh.  Once the retry interval becomes as large or larger then the normal feed interval then that normal interval will be used from then on.

Feeds that longer exist:  IE7 respects the 410 HTTP response (which basically means “sorry nobody lives here anymore”).  When IE7 encounters a 410, it will automatically set the synchronization schedule to “never” for that feed but will *not* delete previously downloaded articles until the user’s pre-defined deletion preference is triggered  (articles are not deleted by IE7 until a pre-set total of up to 2500 articles per feed is reached).

I am interested to find out how Firefox and other Web browsers with inbuilt RSS abilities, and non-Browser RSS readers, address the above issues.  Anybody want to share?

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