Strange Wifi problem

Question

Hello all,
Im aware that most of you are not waiting for yet another wifi problem and I always try to solve them myself, but this time Im not able to do so. The problem is as follows. On my university, I can get a good wifi connection for approximately 30 minutes, (IP and data) but then the connection refuses to transmit any more data.
I've tried multiple wifi cards (Centrino 1030, Ralink RT5370) and dongles, they all give the same problem so I assume thats not the cause of the problem. Also in Windows the connection is kept alive continuously, so thats another confirmation the hardware is working fine.
My guess is that there is a problem in the configuration of my wifi connection on Arch. Two possibilities pop up to me.
1. There is some kind of threshold (time or amount of data), that blocks the connection after a while
2. The wifi connection needs to be refreshed each particular amount of time but Arch (dhclient / dhcpd) is not able to do so
My question is, do you have any suggestions how I could test for both theories or even better solve the problem. Its very annoying when Im working the internet connection stops working every 20 minutes or so. Thanks!
Last edited by Archer22 (2015-04-18 08:45:58)

Answer 1

Archer22 wrote:2. The wifi connection needs to be refreshed each particular amount of time but Arch (dhclient / dhcpd) is not able to do so
This seems the most likely to me - as this is how it works.  But knowing which one of those tools you use would be helpful.  When you connect dhcpcd and/or dhclient gets a lease from the DHCP server on the university network.  These leases have a fixed lifespan (30-minutes sounds reasonable).  When they are about to expire dhcpcd/dhclient should try to renew the lease.  Generally, though, the DHCP server (as far as I understand it) will trigger the renewal a bit before the expiration time.  Based on my experience at a few universities, however, university networks (at least in the US) often have malfunctioning dhcp servers which limp along mostly functional on most days.  I don't know the workings well enough to understand why dhcpcd or dhclient would fail to renew the lease when they are supposed to - even in the absence of the early-renewal trigger from the server, but anecdotally, I see this happen occasionally as well.
And this is complete speculation but I wonder if it is possible for the DHCP server to send out over-estimated lifespans for the lease which then prevents dhcpcd from renewing at the appropriate time.  I don't know these systems well enough to know if this idea makes any sense - but it would certainly fit with my experiences.