Mib Software Newsrate Usenet Server Comparisons

How do news articles get "missed?"

> If propagation of posts is highly distributed (if that's the correct
> phrase), then what could be the problem?

"Receiver-side bottlenecks" is the number one reason. You can have 3 sites trying to shove articles at you, but if you can't process and store them fast enough, you won't get everything you are supposed to get. The second most likely reason is that you didn't get offered the article.

Current transfer rates for full Usenet feeds have to be 7-15 articles per second, 24 hours a day, 7 days a week. That is very demanding on network, disk, etc.

> Here's one thing I'm still unclear about.
> It's my impression that in http, if you miss getting a packet, it will
> wait until you get it and might even be resent if necessary. But from
> what you are saying, if a news server misses an incoming article, it'll
> be lost for good?

The term I use to describe article propagation is "first-to-offer." If a site has two newsfeeds, this does not mean that both newsfeeds transfer all articles. What happens is that a sending machine first checks to see if a message has already been received at the "downstream" site. If not, then it sends it. News is transferred via "push" methods, not like HTTP which is "pull."

Some messages can get lost because there may not be enough time to send everything. I mentioned that a full Usenet feed takes at least 7 articles per second. If there is a bottleneck somewhere, a machine may only be able to take 6 articles per second at its fastest rate.

What ends up happening is that the "upstream" newsfeed runs out of time to offer every article. The ones it never has time to offer never get sent.

Slow response time (a.k.a. bottlenecks), can be due to network outages or network slowness, too heavy a load on the sending or receiving machines, disk subsystems that are too slow, not enough memory on the sending or receiving machine, etc.

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