Webpage sticks more often than not

[silverback]

This is not specifically a Mozilla problem as it happens on my IE8 as well.

I'm trying to access another forum on this page.
Most of the time it hangs as shown in the attached picture. EVentually, the browser will time out, saying the server is taking too long to respond.
Another strange thing about this is, if I close Mozilla completely, and then open it and try to access the webpage again, it doesn't even get as far as the attached picture. The screen remains completely blank.
All other pages I've tried - at the same time so as to compare - render completely, in normal time.

When the forum page does open (once in 10 goes???) it renders very quickly and everything works OK.

I'm wondering if other loungers have a problem opening this page and, whether they do or not, whether someone can offer a suggestion about why it's happening on my PC.

Thanks
Silverback

[HansV]

I've followed your link twenty times or so in Firefox 4.0.1 and in Internet Explorer 9, and also forced a full refresh several times. The page loaded quicky, fully and without problems each time...

[Leif]

Like Hans, I appear to be accessing it OK. (There were 3,448 active users on-line at the time.)

I would think their server was having a temporary glitch. Have you had the same problem before?

As for it being slower on re-starting Firefox, I would suspect your cache is being cleared on a restart and so every image has to be downloaded again. When you simply refresh, the images are still in your local cache.

[silverback]

Result.
Googled for SYN flood to Host (which was what was apparently causing the problem) and found a link specifically for Firefox. Both things turned out to be nothng to do with the problem at all (only symptoms).

The recommendation was to change "Maximum incomplete TCP/UDP sessions number from same host" from 10 to 30 in the router settings. This parameter is in a hidden page of router settings!

The problem has gone away - at least for the last few times I've accessed the website - but what exactly does this setting mean in layman's terms, please? (there was no explanation of what this setting does - only the instruction to change the value.)

Thanks
Silverback

[HansV]

I'm glad you found a solution. Thanks for posting it!

I found the following very helpful explanation:

Maximum incomplete TCP/UDP sessions number from same host: Maximum number of incomplete TCP/UDP sessions from the same host.

I can't find a decent reference, but this appears to be one of a series of settings that have to do with detecting so-called Denial-Of-Service attacks, where an attempt is made to overload an internet server by sending a very large amount of requests in a short period of time. Apparently some routers have a too "defensive" setting. Increasing the number that you mention makes the protection slightly more "relaxed".

[silverback]

The forum I found the fix on has closed down which is why I couldn't ask on that site.
The only clue, which links in to what you say, is that the responder says "some routers are too sensitive". Changing the value gives a bit more leeway.
However, exactly why that site exceeds the 'maximum incomplete TCP/UDP sessions number from same host' when all other sites I access don't cause a problem, I can't imagine.

Thanks for your help.
Silverback

[StuartR]

When you connect to a TCP host there is an exchange of messages to set up the connection. Firstly the client sends a SYN packet to the host. When this SYN packet is received the host allocates memory for the connection information and sends an acknowledgement (that includes a SYN packet) to the client. It then waits to get an acknowledgement from the client to complete setting up the connection.

In a SYN flood attack you send lots of SYN packets to a host, but you ignore the acknowledgement. Eventually the host runs out of memory. One defense against this is to limit the total number of connections that can be in this state, refusing new connections when the number of outstanding ACK packets exceeds a threshold. Another defense is to limit the amount of time that you wait for an acknowledgement from the client before you deallocate the memory again.

[silverback]

ACK
Thanks for this comprehensive reply. I think I might even understand it!
However, I'm still puzzled as to why it's only been this one website that's caused the problem; everything else I've accessed on the web has functioned normally. The website can't have been busy every time I tried, surely.

Thanks again
Silverback

[silverback]

A final comment on this.
Since my last posting (10th July) I've kept all the messages in the Security Log on my router and there hasn't been a single SYN Flood to Host in this period. Neither have I had any 'sticking' webpages.

So changing this value seems to have solved my problem, at least.

Silverback