HTTP persistent connection option

[Larry]

Hi Krein,

I wonder if you could elaborate on the 'persistent connection' option under preferences>internet.

With this option enabled (by default as I remember) recently I have found that right after opening TF, downloads are very fast, but within a minute or so, often the dowloading slows to a stop. A bit later TF will tell me that it cannot connect with the server.

I've been experimenting with this feature off - no persistent connections - and the problem seems to be solved. It's as if the server, after briefly handling my TCP requests on a persistent connection, has put remaining requests at the bottom of its to-do list.  

I found this explantion of persistent connections helpful:

http://en.wikipedia.org/wiki/HTTP_persistent_connections

And I wondered about this: "According to RFC 2616, a single-user client should not maintain more than 2 connections with any server or proxy."

I've been using anywhere between 6 and 30 connections - still experimenting. Could it be that the server might be trying to 'encourage' compliance with the reccomendation?

More detail about the internet options would be great!

Larry

[Krein]

That's interesting, thanks for the pointer to the wikipedia article.

I suppose it's possible that the server is slowing down with too many persistent connections, but I'd think if they were really trying to enforce something, it would be more strict -- like not allowing it at all.

Sometimes (like right now for example) persistent connections keep on rocking, at a pretty incredible speed.  But I have seen what you describe -- a lag after some short bursts of tiles.  It may just been that Terraserver puts later requests on a persistent connection at lower priority than first requests.  So depending on server load (probably low right now) it may be faster or slower.

There's nothing on the TF end that would cause the slowdown, it's all based on the server's response.

Looks like we may want to disable persistent connections if we leave the higher thread option on there.

Let us know if you experiment further with it.