What sort of addresses do 3G end stations receive?

January 7, 2009 11:05 AM

What sort of addresses do 3G end stations receive?

A quick survey around the office has revealed that cell phone manufacturers are not really keen on making the local IP address accessible (and frankly, such a small survey wouldn't be of much use anyway).

Intuitively I would assume they're given RFC1918 private IP addresses and sit behind a NAT box, but I'm hoping someone out there in AskMe land has more direct knowledge.

posted by tkolar to technology (10 comments total)

If you go to www.whatismyip.com it will tell you. On my sprint phone I get 173.100.xxx.xxx
posted by Ferrari328 at 11:21 AM on January 7

Whatismyip.com (totally useful website) won't know if they have a 1918 address.
posted by These Premises Are Alarmed at 11:27 AM on January 7

Heh - I was curious and went to try it from my sprint phone, and got a message that I've been banned from whatismyip.com for overuse. Since I've never visited that site before, that's some evidence that the system's behind a NAT box and/or proxy.
posted by moonmilk at 11:33 AM on January 7

checkip.dyndns.org is another easy-to-remember alternative for checking your public IP address.

Does your connection go through an HTTP proxy? Some of them add extra headers to HTTP requests, including the originating host.
posted by teraflop at 11:43 AM on January 7

Does your connection go through an HTTP proxy? Some of them add extra headers to HTTP requests, including the originating host.

Hmm, interesting point. I know that most cell phones end up going through a proxy; Perhaps I can set up an http server and capture the incoming headers.

Still, all that will tell me is that any particular cell phone ended up with a private/public address. I could get similar one-offs with a 3G card in a laptop. I'm hoping to discover if there is a industry standard or at least best practice...
posted by tkolar at 12:19 PM on January 7

My T-Mobile (non-3G) phone resolves to 66.94.27.11.
posted by mmascolino at 12:27 PM on January 7

This varies per carrier. Most carriers are adopting NAT strategies (e.g. RFC1918 to public) due to the large number of end devices. On a GSM/GPRS/UMTS/EDGE/whatever carrier this can vary by APN; I assume it's the same on CDMA carriers (e.g. VZN, Sprint). The NAT solution is ultimately not very scalable (doing carrier grade NAT is hard) and eventually either we'll see 6to4 translation stacks or dual stacks on the phones.

On GSM networks, when the PDP or UMTS attach is performed, the address is assigned and stays that way until the PDP or UMTS context is released. This is done at the GGSN (not exactly, but good enough for the explanation). A GGSN frequently has a number of NAT pools used for this purpose and you can scale by having n GGSNs. The Regional Internet Registrys (RIRs) are playing hardball with the mobile carriers on this topic.

A recent request from a Cingular (AT&T) terminal came up with:

mobile-0xx-1xx-0xx-2xx.mycingular.net

Where the Xes were replaced with valid IP numbers and the DNS pointed to that address.
posted by arimathea at 12:32 PM on January 7 [2 favorites]

I disclaim the above post by saying I have both worked at a cellular carrier and for a major networking equipment vendor and i'm intimately familiar with the technologies used; so memail me if you have other questions.
posted by arimathea at 12:33 PM on January 7

What phones? Some have status or config screens that list the IP. You may need to google around for the key combo that brings this screen up. Third party applications seem to have access to this info so the IP must be revealable through the network API.

I know that most cell phones end up going through a proxy

Perhap a web proxy but not a proxy for everything. Ive gotten servers to run on smartphones and laptops with EVDO cards all the time. I can host FTP from my pocket. I just get my IP from any 'what is' website, open the application, and it works. Perhaps some plans dont allow this, but my plain-jane sprint EVDO connection isnt NAT'd. I get a new IP everytime I connect, but its a real IP. I guess there could be some transparent 6to4 transition going on, but I have seen no evidence of that yet.
posted by damn dirty ape at 1:34 PM on January 7

Thanks, arimathea!

I'm not on memail so I took the liberty of mailing the address in your profile.
posted by tkolar at 11:58 PM on January 7