| | 02-04-12, 09:59 AM Thread Author #1
BlackBerry Playbook tether app from TetherBridge: a Review
I have been looking for an app for tethering my BlackBerry to my Playbook since last April. I wrote to Tether a few times and frequently checked Tether support forum as well. Much to my frustration, there has been absolutely nothing coming out of Tether. They always say they are working on it but do not have a release date. But they have been saying that for almost a year now with nothing to show for. Out of my frustration, I actually started looking into making an app myself.
This search is finally over. A week ago I found a Playbook tether app on TetherBridge website and have done extensive tests on it (already purchased it, trial for 5 days). Strangely enough, TetherBridge support simply told me they did not have an app for the Playbook when I checked with them last November. They never gave me any indication this was coming nor emailed me after they made this app available.
As a whole, this app (Bluetooth Tether Bridge for BlackBerry) works reasonally well but is not for everybody in my opinion. You only need to install the app to your BlackBerry and it provides the standard bluetooth DUN service. On the Playbook side, you use the Internet Tethering facility coming with the Playbook. You can use this app with Windows PC's, MAC's, and Linux. I tried it with Windows 7 and Linux. It worked fine.
The key to get this app to work is that you need to go to Bluetooth Options on your BlackBerry to disable Dial-Up Networking. This is a little bit counter intuitive. I initially failed to get it to work because I did not read their guide (I used dial-up modems and wrote my Linux modem script myself before). What gets disabled is the default BlackBerry DUN service and disabling actually makes the DUN service of the app effective. You also need to run this app for every tether session. Another thing to note is that you need to enter "tbapn" for the APN entry on the Playbook side instead of your carrier APN specifics (so no need for a carrier tether plan).
I did a lot of speed tests with Speedtest.net - The Global Broadband Speed Test. I also did comparison tests with the BlackBerry Bridge. The lowest Ping latency I got with the app was about 140 ms. With the BB Bridge, the lowest I got was over 700 ms. For download speed, the best I got from the app was 1.7 mb/s while that from the BB Bridge was 1.1 mb/s.
However, the apparently much lower latency and higher bandwidth did NOT always translate to significant speed difference when browsing web pages. This is how it has worked for me: With the BB Bridge, web browsing is fine about 2/3 of the times. For the rest 1/3 of times, it is just frustration. A page may take a few minutes to load or just does not load at all. I used to blame my carrier service for that but no longer. Now with another option, I have found that when the BB Bridge works fine for those 2/3 of times, the TetherBridge app does not give me any noticeable boost. This is surprising and I do not have an explanation for it. I have tried web pages with rich content with a lot of thumbnail pictures. The only exception is web pages with a number of huge sized images. For these pages, the TetherBridge app is a clear winner. It loads twice as fast. The real value of the app to me is for the 1/3 of times when the BB Bridge does not work well. When this happens, I fire up the TetherBridge app, Bingo, it goes fast 9 out of 10.
Now I always use the BB Bridge first, if it works well, that is it. If it does not, I start the TetherBridge app. So far, I have run into problems with both only once. I think that was really a problem with my carrier.
Now I have a much better appreciation of the performance difference between browsing through RIM servers and browsing without going through RIM servers. When the RIM server you use is overloaded at the time when you use it, you can have serious performance problems. This explains why some users have had great experiences with the BB Bridge while others have been complaining really loud. RIM is likely having some algorithm doing load blancing to direct connections to different servers. They definitely have a lot of them. It might be based on the source IP address of the connection initiator (your BlackBerry). This can make some pool of users much worse off than others. Some users get a lightly loaded server and therefore they always get good performance. Those who get a badly overloaded server will have trouble most of the time. I guess I am just in the middle of the pack.
So, if your BB Bridge works well for you, don't even bother to try the TetherBridge app. It will not do anything for you. If you are like me having problem with the Bridge sometimes and caring about it, you can give the app a try. If the BB Bridge simply does not work for you either because of the poor performance or because of special Playbook apps not working with the BB Bridge, it will be really worthwhile for you to try out the TetherBridge app.
BTW, I now have a much better understanding why there was no tether app for the Playbook for so long. As I mentioned above, I looked into making an app myself.
To make an app to run on the Playbook (like the app on PC/MAC side from Tether), you have to be able to make some kind of network driver for the Playbook. RIM will never provide an API for developers to do that as this is at the very core of the OS and security. Even less security concerned Google Android OS and Apple iOS do not allow you to do that, except rooted (Android) or jailbroken (iOS). So, Tether or any other developer will never be able to make an app for the Playbook.
The only options left are making your BlackBerry into a Wi-Fi access point (mobile hot-spot as some call it) or bluetooth DUN as TetherBridge has done. Making the BlackBerry into a Wi-Fi access point is not feasible because RIM does not provide the requried API to developers. I have checked all versions of BlackBerry API and found RIM has not allowed for that to happen, even though BB OS 7.1 has mobile hotspot support (your carrier may make you pay though). So, what TetherBridge has done is really the only possiblity.
I have also observed the DUN on Playbook has something most likely not standard. After it has started talking to my BlackBerry, it will say "Authenticating" and stay with it for around 20 seconds. It will then say "Acquiring IP address". I am quite familiar with the interworking of modems. Normally, you start by issuing AT commands (modem stage) and then start a PPP session. What is strange is RIM calls it "Authenticating". Apparently, they are doing something more than the standard AT commands. Perhaps they are doing some security association between the BlackBerry and the Playbook as they call it Authenticating. It is probably setting up some complex security context on both sides for later encryption as it takes so long to complete. I tried the TetherBridge app with my Windows 7 PC and Linux PC (my own modem script), and the whole connection setup took only a couple of seconds. So, this complication only happens when one side is a BlackBerry and the other is a Playbook. RIM is likely doing some security protection. Another thing I noticed is that a bluetooth DUN connection attempt will fail every 5-10th attempt. What is strange is the TetherBridge app will give an alert and ask me to reset the bluetooth signal on Playbook and BlackBerry. How does TetherBridge app know the other end is a Playbook? Normally the AT commands only allow the host (in this case the Playbook) to query the modem properties. The modem side (BlackBerry) won't know the identity of the host. But apparently the TetherBridge app knows the identity of the host when it is a Playbook.
This explains to me why there was no tether app for the Playbook for so long. If you do not know how it is supposed to work with the Playbook as it is not standardized and not published, it will be a dawnting job to try to figure it out. I would be very surprised if Tether has not tried to make this. They probably knew this issue several months ago but ran into a wall. I don't blame them anymore.