A Possible Cause of AT&T's Wireless Clog — Configuration Errors

AT&T customers (iPhone users notably among them) have seen some wireless congestion in recent months; Brough Turner thinks the trouble might be self-inflicted. According to Turner, the poor throughput and connection errors can be chalked up to "configuration errors specifically, congestion collapse induced by misconfigured buffers in their mobile core network." His explanation makes an interesting read.

Comments

Re:Zero packet loss = epic fail

[MBCook]

Wow. This is kind of amazing.

Nothing on this page (as I type) talks about zero packet loss, except you. That means you read the article.

Of course, the article says that AT&T has set their buffers large enough to prevent packet loss due to congestion in transit, not that they expect no radio packet loss. The problem is that TCP/IP needs packet loss to tell it when it's going too fast and AT&T's decision causes this to fail spectacularly at times.

The trolls read the articles. Weird.

Non-obvious cause

[NixieBunny]

If you take the time to RTFA, you will see that the problem with TCP management (as Mr. Turner describes it) is that you have to cause the system to drop packets occasionally when it's near but not quite at saturation, to let the TCP device at the other end know that the network is getting congested. If there are no dropped packets, TCP ups the packet rate until the network becomes clogged.

So in this case, zero packet loss is a setup for disaster instead of a desirable quality.

The trouble is that it's not an intuitive solution to a problem, the introduction of occasional packet loss. It's usually something to avoid.