Raspberry Pi B+ wi-fi slowdown

Instead than an idea I suggest a possibility: it may depend on the gateway that - I suppose - It is the main gateway and the ADSL connection too. I experienced almost the same problem with the master PI on the Meditech project but I also discovered that this was only when the data packets was going to the router to be addressed to other machines. Then it was not occurring inside of the Meditech networks, where the gateway is a Raspberry PI instead of the main LAN router.

Beside this verifications I also noted that after a certain period of inactivity - keeping the connection up - between a Mac and the main Raspberry PI, both machines connected to the same LAN with the ADSL router as the gateway some slowdown occurred as I was trying again when starting something from the Mac on the Raspberry via SSH over terminal.

My actual conclusion is that this may depend on the fact that the PI after a certain period of inactivity maybe goes in a sort of power-saving mode (should be investigated, I am not 100% sure where I read something about this). When the network connection is awaken, linux machines like the OSX of the Mac simply adapt the packages transmission and the PI in a couple of seconds re-enable all the sleeping services and the connection restarts at the expected speed.

On the router side instead, as it is probably not equipped with a very good software, as the speed goes low then it simply keep this IP packets transmission speed low.

I suggest two test that maybe useful for alls:

• After the connection goes slow for one of the reasons you mentioned, ignore this fact, continue working for a reasonable time (i.e. half one hour or more if possible) and see if the router aligns again it s speed.
• Instead of rebooting try simply to stop and restart the networking on the PI and see if the speed remain slow or not (sudo /etc/init.d/networking stop then sudo /etc/init.d/networking start) and see if the same problem occur again and if the slow state persists.

Then with these information maybe we can investigate more in-detph enabling some specific logs on the network behaviour.

Enrico

After I posted this I realized my cell phone was having an issue too.  Been doing it for a few days.

I realized that PI is set to static IP, and cell phone set to dynamic.  DHCP was assigning the same IP as the PI!

Changed the cell to static and its all fixed!

Joey,

happy that we focused the center of the problem These are the things that makes us crazy when all seems indicating a direction while it is not the right way to see the things.

Enrico

Yes sometimes it is something simple because something improbable has occurred.  I need to reserve a range of IP for static and make DHCP start above that range.

Let me know if you post any questions I will try to help, I am trying to get questions marked as helpful so I can earn that badge

Picking static IP address needs to be done thoughtfully and not randomly.

C

So Im an idiot, got it! 

No not at all because few understand DHCP.

C

Odd behavior when you get 2 devices with the same IP on a network.  I know windows used to pop up a warning but I didn't see anything in the Pis log nor did my cell phone say anything.

DCHP is usually random but the fact it picked the same random number as I did is amazing.  Normally I pick a block for static and a block for DHCP but I kept buying routers and returning them.  It seems that you have to spend $200USD+ to get a router that is functional and stable.  I have an ASUS that finally works.  The 3 others I bought last year all became unstable.

For years I had an old Linksys wrt54g and DDRT installed.  I finally replaced it but all these new routers made me miss it.  DDRT is somewhat unpolished so I don't care to use it.

Yes because underlying ARP tables cannot handle two macs with same IP address. I have seen this behaviour before. Maybe a good install is a IP detector that should show who is using what IP for things like your problem, but also if someone is using your wireless too.

C

Naw just need to setup the DHCP block.  I gave up using MAC filters and hidden SSID, I read nothing I do is really secure except choosing a stong password.

if someone really wants to use it there is no stopping them if they want to put in enough effort.