Why do I get HTTP Code 414 on one network but not another?

Question

I have an otherwise working iPhone program. A recent change means that it generates some very long URLs (over 4000 characters sometimes) which I know isn't a great idea and I know how to fix -- that's not what I'm asking here.

The curious thing is that when I make the connection using a 3G network (Vodafone UK) I get this HTTP "414 Request-URI Too Long" error but when I connect using my local WiFi connection it works just fine.

Why would I get different results using different types of network? Could they be routing requests to different servers depending on where the connection originates? Or is there something else at stake here?

The corollary questions relate to how common this is. Is it likely to happen whenever I use a cell network or just some networks?

Answer 1

I would suspect that your 3G requests are being passed through some proxy which doesn't fancy 4000 char long URLs, and returns an HTTP 414 error.

Answer 2

I suspect the Vodafone connection is going through a proxy and/or gateway that can't handle the extra-long URL, and that your 414 Request-URI Too Long is coming from it.

Answer 3

Some wireless operators - including Vodafone UK, I believe - deploy inline proxies that transparently intercept your HTTP requests for purposes of optimization. Some of these proxies are based on software like the Squid proxy cache, which can have problems with very long URLs. As a result, your requests might not even be making it to your server.

To work around this issue, you can try sending your HTTP requests to the server on a non-standard TCP port. Generally speaking, these proxies are only configured to perform HTTP processing on port 80. Thus, if you can send your traffic on a different port, it might make it through unscathed.