06-13-2012 11:35 AM - edited 06-13-2012 12:20 PM
As of yesterday, SSH connections to all SSH servers I normally connect to, keep disconnecting if I connect via my AT&T cell phone. The ConnectBot Android SSH client disconnects after 5 to 20 seconds of use, consistently.
This only started yesterday. Before that, I never had a problem with it. It has happened in different parts of the city so it's not connected to a given cell tower. This is still happening today.
When I connect from my phone using any WiFi access point, I do not get disconnected, so it's not a problem with the app nor the target server.
Has AT&T made an unannounced policy change about SSH ports? Perhaps a process on their servers that seeks out various ports it "doesn't like" and kills the connections?
06-13-2012 1:21 PM
I just talked with some other people, and they are seeing the same things happening on TCP ports that aren't in the usual list of web/ftp ones.
AT&T must have changed some policy and started disallowing ports it doesn't like.
Can any AT&T representative speak to this?
06-13-2012 3:19 PM
I noticed this behavior too.
While running a network analyzer on my handset and the server it is connecting to, I can see that something forges a packet in the TCP session (source = my server, destination = my handset) with the RST bit set. This instructs the TCP/IP stack on the handset to tear down the socket, resulting in a "connection reset by peer" message.
The RST comes down approximately 30 seconds after the socket is established, and happens when the handset connects to an SSH server on port 22, or a web server on port 80. (Try downloading a big file from a slow server. You won't get the whole thing.)
Since the analyzer running on the server side does not see the packet with the RST bit, and the one on the handset does, it's pretty safe to assume that something is forging the packet. My guess is AT&T's NAT gateway, as it's one of the few places on a network that maintains enough session information to forge a plausible TCP packet.
No idea who to contact. After three levels of suport, I've concluded that they're not equipped to handle this situation.
06-13-2012 4:40 PM
Very interesting - if it were AT&T's goal to block a port, you'd think they'd just block it outright in their firewall.
Sending an RST packet after a connection has already been established is kind of bizarre (unless it's just a misconfiguration issue, or AT&T trying to be sneaky :-) ).
06-14-2012 11:04 AM
Amazingly, even connecting via my MicroCell at home, using my own data connection, AT&T is terminating SSH connections made from my phone.
Thanks, AT&T - I'm using my own data, a device I bought from you, and you are terminating my connections without telling me why. :-(
06-14-2012 3:25 PM
As others have said, I'm also noticing that any kind of a long download (FTP only - HTTP downloads appear fine, though I wouldn't bet on it) stall after awhile.
I'm wondering if it's across the board for certain protocols and download sizes, or only account or phone-type specific (eg. "You're not using an AT&T phone" or "You've used unusual protocols" or "We think you may be tethering" or whatever, and thus any kind of long connection is terminated.
I still want an answer from AT&T about what in the world is going on!
06-14-2012 6:57 PM - edited 06-14-2012 7:10 PM
I noticed a few days ago now, that the streaming audio app I use about half hour a day on the way to work now no longer works as the connection is terminated every 28 seconds or so. I thought at first it was a problem wit the app, so downloaded a different one and I see exactly the same thing. Everything works fine on WiFi it just disconnects when on Cellular. Looks like I will be cancelling my contract as this is about he only thing I actually use my phone for...
06-14-2012 7:08 PM
Lwlandy, are you using a phone you bought from AT&T, or an unbranded phone? I'm trying to find a pattern here, and see if it's just people like me who are using unbranded phones (Galaxy Nexus from Google), or what.
06-14-2012 7:15 PM
Its an AT&T phone bought in an AT&T store, and I actually have an unlimited data plan. At first I thought they were throttling my connection but I dont use more that 2GB a month either and when this started I had only used about 700k according to the ATT data tracking on their portal.
I am planning on calling customer service tomorrow and asking why my app no longer works on their Network.
06-14-2012 9:20 PM
Well, good luck talking to tech support. I had no luck there. Please report back if you discover anything, please! :-)
06-15-2012 7:33 AM
So on my way in to work this morning my Streaming app worked! Yay!
Not sure if someone at ATT saw this thread, or if they realised they had made a change and backed it out, but it seems to be back to normal again (For me at least).
06-15-2012 9:02 AM
Lwlandy - hooray for you!
And apparently, you may be right, since I just tested my phone and SSH has stopped disconnecting after 10 seconds.
I will test it throughout the next week and see if it comes back.
I bet you're right - someone either read these forums, or saw they had misconfigured something, and backed it out.
I wish they would TELL us something, but that might open them up to legal action, so I bet it'll never happen.
I shall report back in a few days or a week as to if the problem ever returned.
Thanks for letting me know, and happy streaming!
06-15-2012 2:46 PM