Category: Networking

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English Usability Web Browsers WTF

Firefox 29 “Sync” nightmare

The — as I later found out — completely revamped “Sync” feature in Firefox 29 caused me a lot of grief yesterday, and I wasted more than 3 hours due to it. :-(

The issue started after I had to set the system time back on one of my Macs which I hadn’t used for a couple of weeks, so the Firefox data on that machine was outdated and not in-sync with the other machines synced to the same Firefox Sync account. Not sure whether setting the date back was the root cause, but anyway… I suddenly noticed that I had old passwords on another machine, too. Obviously it had received them via Firefox “Sync” from said Mac.

So, what to do?

I first cleared the data stored in my Firefox Sync account by logging on to the old account management (https://account.services.mozilla.com/), to make sure that the outdated passwords do not propagate to more machines.

I then disassociated the machines that had already received the outdated passwords from Firefox Sync.

Afterwards I wanted to add the device back the same way I did when adding a new machine in the past. But it didn’t work as it used to work. No way I could display the sync code I needed to enter on the “master” machine. :-(

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Cell Phones Communications Networking WTF

OpenWRT Quality-of-Service module caveat: speed limit

As I still have “issues” with my DSL line being extremely slow during certain times (especially between 18:30 and 23:00), I wanted to use USB tethering from my OpenWRT router to my Android LTE phone to enjoy the massive speed I have in our area (up to 90 MBit/s downlink and 70 MBit/s uplink, according to the Ookla Speedtest.Net).

So I configured the router according to the OpenWRT wiki. The internet connection did not come up immediately, and I couldn’t find out why, so as a last resort I rebooted the router. After I switched on USB tethering again on my mobile phone (which seems to be required each time you reboot the router since the mobile phone then loses the USB tethering connection), I suddenly had a working Internet connection.

However, for some reason the Internet speeds I was seeing in Ookla’s web browser-based speed test (which is a Flash applet) were very disappointing, around the same speeds I’m used to with my DSL line (14 MBit/s downlink, about 0.8 MBit/s uplink). I thought it might be an issue with USB tethering not working well in my build of OpenWRT (still r39582), so I tried USB tethering with my Mac (using HoRNDIS). I got the full speed I expected. So back to OpenWRT…

Then suddenly I suspected what might be going on: Since I had more or less exactly the same speed as my DSL connection (with the uplink of less 1 MBit/s being dramatically slower than what I should get via LTE) I thought about what could possibly limit the speed. And then I remembered that in the “Quality of Service” (QoS) module I configured the speeds of my DSL line (at the top of the page, in the Download speed (kbit/s) and Upload speed (kbit/s) fields). Could it be that these settings actually limit your speed to these values?!

I disabled QoS, and immediately thereafter I got the full LTE speed I expected.

So, another thing learnt.

I hope this helps people who might be in a similar situation…

Categories
Computers Networking

How to properly benchmark your broadband connection

Since a while my broadband connection gets slow frequently, so I wanted to perform regular benchmarking probes and create a graph to illustrate the actual uplink and downlink speed.

Your first approach to this might be to download and upload a payload, measure the time this took, and divide the sizes of the files you downloaded and uploaded by the times it took. But this approach is seriously flawed… Why? Simple. In a usual scenario you have a router that terminates your internet connection, so eventually other LAN clients will cause traffic at the same time you’re performing your probe. This would “limit” the bandwidth you have for your probe, and thus artificially reduce the speed you calculate.

So how to do it properly? You should ask your internet gateway (your router) for the traffic it sees.

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Networking Routers

Arcor bzw. Vodafone EasyBox 803A: Verwendung nur als “Modem”

Bisher habe ich an meinem Arcor- bzw. nunmehr Vodafone-ISDN/DSL-Anschluss noch separate Komponenten verwendet: Splitter, ISDN NTBA und Speed-Modem 200. Aus aktuellem Anlass (plötzlich drastische Einbrüche bei der Internet-Geschwindigkeit von normal 16 MBit/s auf teilweise nur 1-3 MBit/s) habe ich diese jedoch gegen eine Vodafone EasyBox 803A ausgetauscht, weil ich einen Defekt des Modems oder Splitters vermutet hatte.

Die EasyBox ist recht clever konstruiert, sie kann nämlich selbständig feststellen, ob sie an einem Analog-/ISDN-Anschluss betrieben wird, wo der Splitter benötigt wird (um das UK0-Signal für den NTBA abzutrennen), oder an einem reinen DSL-Anschluss (NGN), wo er nicht benötigt wird, weil dort Sprache per VoIP über DSL übertragen wird. Je nachdem wird also der Splitter und NTBA in den Signalweg eingeschliffen oder nicht. Das ist das Klickgeräusch beim Einschalten der Box! Man sollte bei Verwendung der EasyBox einen evtl. noch vorhandenen separaten Splitter aus dem Signalweg entfernen und die EasyBox direkt an die “erste” TAE-Dose (früher “Monopoldose” genannt) anschließen, um die Dämpfung (“Leitungsqualität”) zu verbessern (und damit ggf. noch ein wenig zusätzliche Geschwindigkeit aus dem DSL-Anschluss “herauszukitzeln”).

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Computers Networking

OpenWRT: Easy and secure guest WLAN access

I use OpenWRT on my TP-Link TL-WDR3500, and I have a guest WLAN defined on each of the two radios (2.4 and 5 GHz). The guest WLANs are isolated from my LAN, i. e. guest WLAN stations can’t talk to any of my own hosts (either on the WLAN, or in the LAN, i. e. hosts connected via Ethernet). Guest WLAN stations also can’t talk to each other. The actual OpenWRT configuration (apart from passwords, of course ;-)) is not a secret, I will publish an article about that soon.

For security reasons I didn’t want a static guest WLAN password, but one that changes daily, so that I don’t have to manually revoke the right to use my WLAN by changing the password all the time. So I created two tiny scripts, one that actually changes the active WLAN password every day, and one CGI script that displays the password so that I can give it to my guests.

Here’s the first one that sets the password. I run it from cron at 00:01 every day:

 #!/bin/ash
 SALT="theSalt"
 DATE=`date -I`
 PWD=`echo -n "${SALT}${DATE}" | md5sum | cut -c1-16`
 CHANGE=0

 if [ `uci get wireless.@wifi-iface[2].network`x = guestlanx ]; then
   uci set wireless.@wifi-iface[2].key=$PWD
   CHANGE=1
 fi
 if [ `uci get wireless.@wifi-iface[3].network`x = guestlan2x ]; then
   uci set wireless.@wifi-iface[3].key=$PWD
   CHANGE=1
 fi
 if [ $CHANGE -eq 1 ]; then
   uci commit wireless
   wifi
 fi

And here’s the CGI script that needs to go to /www/cgi-bin to show the current password:

#!/bin/ash
SALT="theSalt"
SSID="Guest-WLAN"
DATE=`date -I`
PWD=`echo -n "${SALT}${DATE}" | md5sum | cut -c1-16`

echo "Content-Type: text/plain"
echo ""
echo "Today's Guest Password for $SSID is $PWD"

Don’t forget to make the scripts executable by running “chmod +x <script>“.

If you find this helpful I would appreciate your feedback.

Categories
Communications Computers Networking

Windows 7 PPPoE-Protokoll schlecht implementiert?

Anläßlich eines Problems mit meinem Vodafone 16 MBit/s-DSL-Anschluss — Geschwindigkeit ging plötzlich dramatisch in die Knie, ca. 1-2 MBit/s nur noch! — habe ich testweise die PPPoE-Verbindung direkt vom Laptop unter Windows 7 über das Arcor-DSL Speed-Modem 200 zum Konzentrator bei Vodafone aufgebaut. Auf diese Weise wurde das Modem als “Schuldiger” ausgemacht: Ein baugleiches Ersatzmodem lieferte sofort über 14 MBit/s!.

Nachdem ich dann wieder das DSL-Modem mit dem TP-Link TL-WDR3500-Router (mit OpenWRT als Firmware) verkabelt hatte, stellte ich plötzlich erstaunt Folgendes fest: Die Ping-Round-Trip-Zeiten gingen von 31-32 ms (unter Windows 7 als PPPoE-Client) deutlich herunter auf 21 ms (mit OpenWRT Barrier Breaker r39582 als PPPoE-Client). Das ist insofern sehr erstaunlich, da ja nun eine 802.11an-WLAN-Strecke und der Router als zusätzliche Latenz erzeugende “Komponenten” hinzu kamen!

Ich interpretiere das so, dass die PPPoE-Implementierung unter OpenWRT der von Windows 7 deutlich überlegen ist, da sie offensichtlich “schneller” bzw. “effizienter” ist. Bevor jetzt jemand sagt “Vielleicht hast Du einen krötenlangsamen Laptop verwendet?” — nein, das ist nicht der Fall, es war ein Lenovo X220 mit einem Core i5-Prozessor mit 2.5 GHz…. Und der Laptop war dauernd “idle”… 🙂

Eure Meinung zu dieser Interpretation würde mich sehr interessieren, daher würde ich mich über Kommentare freuen.

Categories
Networking

OpenWRT on the TP-Link TL-WDR3500

I got myself a TP-Link TL-WDR3500 since it boasts great hardware (see below for detailed info), and at the same time is supported by OpenWRT which I easily found out by searching in the OpenWRT forums.

Here’s the direct link to the firmware image (current “unstable” or “bleeding edge” OpenWRT release “Barrier Breaker” — i. e. not current stable one, which is Attitude Adjustment — build r36486) which you can use to upgrade a device with the factory firmware still installed. (Update: The link refers to the “trunk”, i. e. the development branch, where daily builds are available.)

Installing OpenWRT using the stock firmware’s “Firmware Upgrade” function worked smoothly. Less than 5 mins. after I started the upgrade I had OpenWRT running (thanks, folks!).

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Categories
Networking Routers

OpenWRT and DNS UPDATE

I’m hosting my domain myself on a dedicated root server, and I wanted my Internet router to automatically update a hostname in my own domain (in a designated dynamic zone) with my current public IP. With OpenWRT this was easily accomplished. I used these instructions as a starting point.

When trying to check whether everything was set up correctly I always got some strange error from the following command:

# ACTION=update INTERFACE=wan /sbin/hotplug-call iface

It turned out that the following statement

config_get ipaddr wan ipaddr

did not return the currently assigned IP address in my case, but just an empty response, so I got the following error message:

could not read rdata
syntax error

(For testing I hooked a spare router with a fresh OpenWRT install with the WAN port into my LAN, and configured the WAN interface to receive its IP address via DHCP from out of the LAN. In “production” the WAN interface receives its IP via PPPoE.)

Some friendly guy in the OpenWRT forum suggested I try the following instead:

. /lib/functions/network.sh
network_get_ipaddr ipaddr wan

And indeed this worked well.

Categories
Networking Windows

Cisco VPN install nightmare on Vista

Here’s another Cisco VPN client nightmare for you:

The old 4.9.x.x Cisco VPN client does’t run under Vista anymore. So I downloaded the most current version our organization has available, 5.0.05.290. I started the installer and pretty quickly received an error message that simply said: “Internal Error 2738″.

I thought maybe the install file was corrupt, so I redownloaded it — same error.

Now I read the readme file (which I normally don’t do ;-)) It said you need a Microsoft hotfix in order to be able to install the VPN client. So I downloaded that one as well and retried the installation after rebooting the machine — same error message agin.

Damn!

So I googled for this problem and quickly came across this website — which indeed fixed the problem for me.

Thanks, Microsoft, for making such a lousy job of not registering said DLL. And thanks, Cisco, for not pointing your customers to this problem.

Gaaaawd, how I hate monopolies…