Phuket Information Technology Blog

Warning: 3BB installs routers with WEP encryption

admin — Wed, 28 Sep 2011 12:22:34 +0000

Warning to all 3BB customers: 3BB routinely installs ADSL routers (recently Huawei) where wireless is protected by a WEP key. It only takes a few minutes for a skilled IT person on a vacation to break into a WEP-protected network just for fun from the house or cafe nearby.
Dangers: if you have shared unprotected content within your network it will be accessible to such person. If he will carry some malicious activity using ADSL connection belonging to you, activity might be attributed to you. Just think about the implications of someone downloading child porn or plotting a terrorist attack using your connection!
Don’t say “nobody have a reason to hack me”, upgrade you security to WPA at least, or WPA2 if it’s supported by your router and wireless adapter. Use a good password that cannot be found in any dictionary. For a power user it only takes a couple of minutes to make the settings right.

SpeedTest vs. DSLReports Analysis

admin — Sat, 17 Sep 2011 07:21:51 +0000

I decided to do a little check on this article:
http://www.phuketgazette.net/archives/articles/2011/article10972.html

Update: details for SpeedTest.net are for Los Angeles as well now.

SpeedTest.net

Latency

Get http://ndt.dhspeedtest.com/flash/speedtest/latency.txt?x= (this request repeats 10 times)

Last-Modified: Fri, 28 Jul 2006 23:31:21 GMT

Download Speed

Download in 1 thread http://ndt.dhspeedtest.com/flash/speedtest/random750x750.jpg
Download in 2 threads http://ndt.dhspeedtest.com/flash/speedtest/random750x750.jpg

Note: URL is for Los Angeles server

Upload Speed

Upload in 2 threads 29705 bytes of random data
Upload in 2 threads 29705 bytes of random data
Upload in 2 threads 95251 byte of random data
Upload in 2 threads 95251 byte of random data

Note: the download and upload patterns differ for different locations!

DSLReports

Latency

Get http://www.dslreports.com/ft?c=gd&o=records&limit=4&f=myuid

Cache-Control: no-cache, max-age=0

Download Speed

Downloading http://dslreports.linkline.com/SpeedTests/random750x750.jpg?x=0.928372583817691
Downloading http://dslreports.linkline.com/SpeedTests/random500x500.jpg?x=0.663370833266526

Note: URL is for Los Angeles server

Upload Speed and Compression Check

Uploading 100009 bytes of zeros
Uploading 50009 bytes of random data
Uploading 100009 bytes of random data

Conclusions

Upload and download speed differences are most likely not related to any caching; data downloaded and uploaded is random. Numbers are different because DSLReports uses single thread and SpeedTest.net uses 2-4 threads. One question remains: do both sites do any checksumming on the downloaded data to assure it is really what their servers send them or it’s a stale copy from some cache?

Latency: SpeedTest server does not put the proper Cache-Control: directives in the reply, therefore the latency measurement is more likely to be affected by caching. DSLReports put the proper directive in the reply but that does not mean the latency result cannot be faked intentionally by the ISP proxy. It is possible to configure a proxy server to always use cached result for a given URL, ignoring directives from a Web server; but in that case the proxy would not be RFC2616-compliant anymore.

RFC2616, 13.3 Validation Model

When a cache has a stale entry that it would like to use as a response to a client’s request, it first has to check with the origin server (or possibly an intermediate cache with a fresh response) to see if its cached entry is still usable.

Please note what for the latency measurement the content returned is not important; if proxy complies with RFC2616 it MUST check the resource on the original server before returning the resource and this means HTTP “ping” value would be about right (it will consist of round-trip time from the client to the proxy + round-trip time from proxy to the original server).

On the other hand, if the proxy is not RFC2616 compliant, I do not see any advantage of DSLReports over SpeedTest.net; it seems that DSLReports latency can be faked as well if ISP wishes to do so.

LCD TV and Monitor Repair

admin — Fri, 09 Sep 2011 08:41:28 +0000

Since we started our LCD repair service, we fixed several dozens of monitors and LCD TVs, mostly Samsungs. The most common failure is a power-on problem. It usually starts like the monitor/TV does not power on immediately and needs more and more time to warm up; at the end it does not power up at all, screen stays dark and only the power LED is blinking on some models. Other models with the same failure power on just fine but the backlight brightness flickers. The price for the repair of this problem usually varies from 1000 to 1500 baht.

Mobile Number Porting from True Move to AIS

admin — Fri, 09 Sep 2011 06:11:12 +0000

I am battling for almost a month already with both True Move and AIS to port my number. The porting request was rejected already 3 times with the reason sent by SMS from AIS: …your name or your mobile phone number is incorrect…
What exactly is incorrect is unknown and AIS representative claims the True Move do not give this information to them. Also AIS representative spoke directly to True Move call center (but only after I insisted they do it) to verify all contact details. The result – another rejection! The True representative said on the phone what if AIS sends the name in the request like “JOHN DOE” but it’s recorded in the True database as “John Doe”, they will reject the request. Same if it’s “Mr. John Doe against “Mr.John Doe” it will be rejected as well! And this has nothing to do with the computer unable to match the records – it’s the live person who makes the decision. Also it seems the name on file in True Move is kept in more than one location, so it’s possible that your name is spelled right in their main database and wrong on the invoice they sent you!
I’ve sent the complaint regarding this case to the Office of the Consumer Protection Board by email listed on the bottom of their main page and I hope the people experiencing the same difficulties will do it as well.

Phuket electronics recycling – win the prize!

admin — Tue, 06 Sep 2011 15:33:50 +0000

Phuket News tells us about the new way to recycle your electronic trash. You can even win the prize for that!
The project has a Facebook page. I wonder what they are going to do with the item #84001 though…

True Cable (DOCSIS) Internet Hardware

admin — Mon, 05 Sep 2011 11:23:06 +0000

The hardware we saw so far:

Warning: IP address you will get on WAN interface is from private ip address range (10.x.x.x)! Therefore no port forwarding would be possible (probably the most common use for it on the island is remote access to the CCTV recorders and IP cameras); problems with VPN etc…

ZTE MF180 (AIS branded)

admin — Wed, 31 Aug 2011 06:21:35 +0000

Just tested ZTE MF180 3G modem provided by AIS with our 3G sharing wireless router. Download speed ~ 2.5 Mbps, upload ~ 400kbps (to Prince of Songkla University, Phuket). Works under Ubuntu Linux too.

AIS 3G on Phuket

admin — Sun, 17 Jul 2011 10:05:25 +0000

It seems AIS intends to deploy 3G connectivity island-wide from July 28.

TOT problems with HTTPS traffic

admin — Sun, 17 Jul 2011 04:10:06 +0000

Since July 17 secure web sites work very slowly on TOT ADSL connection. Looks like the problem is Thailand-wide:
http://www.thaivisa.com/forum/topic/483338-tot-blocking-access-to-secure-web-sites/
It is definitely not blocking, but perhaps traffic shaping gone wrong? We noticed all the other sites are loading a lot slower, and HTTPS protocol is very sensitive to the packet loss…

Matching Linux ata numbers to the device names

admin — Sat, 16 Jul 2011 11:13:25 +0000

Many thanks to Dirk Tilger for the information on his blog. I am just providing the more manageable commands to type

Recently we had to recover data from a 8-drive soft-RAID5 on Linux. It had 3 devices failed out of 8. 2 of the drives just had some bad sectors on them. The problem is, the Linux kernel reports errors on the device as ata channel numbers, for example as “ata1.00″. All 8 drives were the same model, the serial number is not reported via dmesg, so how to know the device name (like /dev/sda) that is causing these error messages?

The command

grep '[0-9]' /sys/class/scsi_host/host{0..9}/unique_id

will provide output like this:

/sys/class/scsi_host/host0/unique_id:1
/sys/class/scsi_host/host1/unique_id:2
/sys/class/scsi_host/host2/unique_id:0
/sys/class/scsi_host/host3/unique_id:0
/sys/class/scsi_host/host4/unique_id:3
/sys/class/scsi_host/host5/unique_id:4
/sys/class/scsi_host/host6/unique_id:5
/sys/class/scsi_host/host7/unique_id:6

so we can match the unique id used in kernel error messages to the host number. Then the command:

ls -l /sys/block/sd*

Will show us which device name belongs to which host number:

/sys/block/sda -> ../devices/pci0000:00/0000:00:13.2/usb1/1-6/1-6:1.0/host2/target2:0:0/2:0:0:0/block/sda
/sys/block/sdb -> ../devices/pci0000:00/0000:00:13.2/usb1/1-8/1-8:1.0/host3/target3:0:0/3:0:0:0/block/sdb
/sys/block/sdc -> ../devices/pci0000:00/0000:00:12.0/host6/target6:0:0/6:0:0:0/block/sdc
/sys/block/sdd -> ../devices/pci0000:00/0000:00:13.2/usb1/1-8/1-8:1.0/host3/target3:0:0/3:0:0:1/block/sdd
/sys/block/sde -> ../devices/pci0000:00/0000:00:13.2/usb1/1-8/1-8:1.0/host3/target3:0:0/3:0:0:2/block/sde
/sys/block/sdf -> ../devices/pci0000:00/0000:00:13.2/usb1/1-8/1-8:1.0/host3/target3:0:0/3:0:0:3/block/sdf
/sys/block/sdg -> ../devices/pci0000:00/0000:00:12.0/host7/target7:0:0/7:0:0:0/block/sdg

From these two outputs we can see that the unique id 6 maps to host7, and host7 maps to /dev/sdg. And finally, with the command:

hdparm -i /dev/sdg

/dev/sdg:
 Model=ST3500418AS, FwRev=CC34, SerialNo=6VM2KSFD

we can find the serial number of the drive.