Just learning about this via youtube but could not find answer to my question of how reader knows there is an update.
Is it like a Push in blackberry?
5 Answers
RSS is a pull technology. The reader re-fetches the RSS feed now and then (for example two times per hour, or more often if the reader learns that it's an often updated feed).
The feed is served through regular HTTP and consists of a simple XML file. It is always fetched from the same URL.
It just check the feed for update regularly.
Recently there is a new protocol called pubsubhubbub to make feed push to the listener. But it requires the publishers support it.
Here is a list of web services support real-time RSS pushing, including Google Reader, Blogger, FeedBurner, FriendFeed, MySpace, etc.
It's a pull. That's why you have to configure your reader how often it should refresh the feed.
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