Photographs courtesy of Toby Watt - lawyer, friend and photographer extraordinaire...
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).
If a user is unable to access your Feed, they will see this error:
If your Feed has an error, the user will see: