TechBait

TCP/IP is used within corporate and other private networks.  Address conflicts with Internet systems is something to be avoided, so non routable IP address ranges are used internally on private networks to prevent this and also for security reasons.  An Internet based system cannot directly address one of these IP addresses.  The non routable addressed systems are allowed to access the Internet through NAT or a proxy system.

The non routable IP address ranges are:

Class A:  10.0.0.0 – 10.255.255.255

Class B: 172.16.0.0 – 172.31.0.0

Class C: 192.168.0.0 – 192.168.255.255

I recently bought a Motorola DROID smart phone on the Verizon Wireless network.  The phone seems to be very durable, and the Android operating system is a wonderful competitor to Apple’s iPhone.  There are a growing number of apps available for these phones, with some notable ports of iPhone apps to the Android platform.  There are some weaknesses of the Motorola DROID phone that potential customers should know about.  The ones that I have stumbled upon are that text messages get deleted often by the phone, even when the auto delete setting is switched off, the fact that the phone has pathetically small internal memory for apps (about 256 megabytes, which is pathetic), and that multimedia messages take up so much internal memory that you might end up deleting apps just so that the phone dialer storage doesn’t run you into the wall when its growth runs wild, and vanishing bluetooth devices.

• Text message threads are set to auto delete when they hit a certain number of messages.  You can alter or turn off this default behavior in the test message app settings, but it will eventually delete them anyway.  It happened to me several times and it is happening to others our there.  The only thing you can do right now is to install SMS Backup, a nifty free app that will copy your text messages to your Gmail account for archiving.  It works, and there are paid apps that will also do this for multimedia messages (picture and video containing messages).

• The Motorola DROID has a pathetically small internal memory of 512 MB, half of which is available for apps.  To add insult to injury, Verizon is advertising that phone as having 16GB of memory due to the micro SD card that they ship with.  The problem is that Google has made it so that only internal phone memory is available for app executables, and most apps are made in a way that they use the internal memory for everything, so if you install many apps you run out of memory pretty quickly.  Regular apps are small, but install a few games or some data crazy apps and see how far you get.  Shame on Motorola for cheaping out on memory, Verizon for false advertising, and Google for not allowing some more leeway for using the SD card for applications, although they cite security and piracy concerns.

• The “phone dialer storage” app seems to store data of some sort on the phone, and it tends to runaway with itself as you create more message threads, especially those rich with photos or video attachments.  The obvious cure would be to delete the photos and other attachments or purge your text messages every so often, which works up to a point, but I found that my phone dialer storage held it’s data cache even after I purged.  The phone got sluggish and rebooted itself a few times too.  Finally after one spontaneous reboot, the cache was somehow purged.  Perhaps there is some internal software setting that does this, but it’s VERY annoying and not a graceful way to go about it.  The best thing that Android users who hit their phone’s memory limits can do in the meantime is to get an app management application which allows them to shuffle apps around from the SD card back to phone memory.  What this means is that you have to archive the app to the SD card and then uninstall it through the management app.  If you want to use it later you can reinstall it from the archived copy.  This allows you to archive those many megabyte game apps that you might not use everyday but don’t want to ditch for good.  It’s a compromise but it works.

• My bluetooth ear piece, a Samsung WEP470, occasionally vanishes from the phone.  Usually rebooting the ear piece fixes the problem, but I found that one time it did not.  Sometimes turning the phone’s bluetooth on and off would fix the problem.  One time nothing worked, and you could hear the incoming phone call beep in the ear piece but when the call was answered no sound came through the ear piece.  I thought the Samsung bit the dust and even started shopping for a new one.  I tried a shot in the dark approach of turning the phone off and removing the battery for a few seconds, about 10, and then powering it up again.  My bluetooth ear piece now worked fine again.  Go figure.

Have you ever wanted to communicate somewhat securely over a public network, like the Internet, in order to exchange confidential or sensitive information, passwords, or other data?  You need a VPN to connect you from one point to another over the insecure public medium.  This secure connection is the VPN, or Virtual Private Network.  The VPN, whether purely software or by utilizing a VPN appliance device containing it’s own software, uses encryption software to construct a tunnel between the two points, thus allowing the user to exchange confidential information or sensitive login information between two points.  VPN’s can also be useful for simply contacting your private network remotely, since you don’t want unknown entities to see your internal network infrastructure, hosts, or to sniff out your passwords.

On a similarly related line of thought, if you use UNIX or Linux, a good way to access your home network over the Internet from a remote point is to set up an SSH tunnel, where the Secure Shell is used to contruct a tunnel.  You login to the remote UNIX or Linux host via SSH, and then you can launch graphical Xwindows applications using an SSH tunnel.  You can do this from a Windows client by using the Cygwin or other software which allows one to run POSIX, GNU, and UNIX/Linux utilities on a Windows machine.  You can do this from work if your network allows this sort of Internet access.  It is handy to be able to access your home UNIX/Linux server over an SSH tunnel.

$ ssh -X u...@server.homenetwork.com
$ ssh -X user@<public ip address of server>

You can requests compression of all data to improve up user experience (good for a low speed link such as wan link) using -c option:

$ ssh -c -X user@<public ip address of server>

You can then run any Xwindows application on the remote xterm by simply typing the program executable name followed by the ampersand to spin it off into it’s own process ID.  You can also run an entire desktop like KDE, Gnome, or the default Xwindows desktop with the startx command.

In computer networking parlance, ARP stand for Address Resolution Protocol.  Well, this tells us that computer addresses are being resolved via some sort of lookup table.  The ARP cache is what translates IP (Internet Protocol) addresses to hardware MAC (Media Access Control) addresses within a TCP/IP network.  ARP replies can be spoofed easily if one of your network;s systems are compromised.  The compromised system can spoof other systems on the network.  The spoofing is when the target machine receives faulty information linking an unsafe MAC address to a local IP address.  The preventative measure (UNIX and *NIX) is a list of trusted systems that is hard coded into the /etc/ethers (or equivalent) file where the true MAC addresses are mapped to the true IP address, preventing the ARP protocol from overriding this information.  The file needs to be updated if a network card is changed since every networked device must have a unique MAC address.

The Archos 5 is a slate computer that competes in the same market segment as Apple’s iPad and HP’s Slate computer which runs Windows.  The Archos is a nifty gadget because it is compatible with the Android marketplace apps and is essentially backed by Google’s massive software effort.  It is larger than a phone and makes for a great WiFi Internet device when home or have access to a WiFi hotspot.  As anyone knows, the small screens on most smart phones are woefully inadequate for real web surfing, and the Archos and other similar devices provide a larger screen and more memory for a fuller Internet experience.  While it is true that this device would be better if it had 3G capability like the iPad or other devices in this segment, perhaps the Archos makers know that most gadget freaks already have 3G smart phones and this is yet another tool that the true gadget freak will have in their technology bag of fun.

I’m happy to see that the Rite Group still has their page up on how to set up a Solaris DHCP client.  This works and it is very useful.  I always would point field engineers who needed to accomplish this task to this page, and I used it myself for any in house Solaris machines that had to be set up as DHCP clients.  Find this useful method HERE.

Solaris is Sun Microsystems’ version of UNIX.  For non NIS/NIS+ Solaris machines, the things necessary to add it to an IP network are:

• The /etc/hosts file must have the hostname and IP address of the machine.
• There must be an /etc/hostname.[interface] file which contains the system hostname.  The [interface] is the designation of the network interface assigned the address, for example, /etc/hostname.eri0 or /etc/hostname.dmfe0
• There must exist an /etc/netmasks file which holds the subnet mask for the machine.
• The /etc/resolv.conf file must contain the DNS server if the host relies on DNS for name to IP address resolution.
• Finally, the /etc/defaultrouter file needs to hold the IP address of the router for the subnet – or in other words the default gateway address.

I just read an interesting Wired article about how an unnamed FaceBook employee told a reporter that the CEO doesn’t believe in privacy.  While this is merely one employee’s off the record opinion, FaceBook actions and policies seem to bear this out.  I didn’t realize how much information was being shared out by FaceBook, and it is true that they are littered with hackers and social engineering types who cause all sorts of havoc for account holders.  What’s your opinion on that?

Ever wonder how to use your smart phone’s Internet connection as a modem for your notebook or laptop computer while unable to connect to another WiFi hot spot?  While WiFi hot spots are available at an increasing rate, sometimes you are in a place where an unsecured public access one just is not available.  Now, if you are out and about one might wonder can’t you just use the phone’s web browser to look something up?  Well, yes, to a degree.  Sometimes there is just no replacement for a full computer for your Internet needs.  There are several programs out there, and there are also methods that involve rooting your phone, but a non root convenient method is to use a nifty application called PDAnet on your PC and phone.  Simply install PDAnet to the computer and it will also install the driver.  Once you connect your Android phone to the computer via the USB charging cable, the phone side app will be installed and you can now use the phone as a modem for the computer.  You have to turn on USB debugging mode, which was already enabled on my phone.  Once everything is up and running, you will have full Internet access on the computer via the phone and your unlimited data plan.  I wouldn’t use it as my sole connection or to download vast amounts of data, but it is great in a pinch.  Case in point, you want to use your computer with Internet access at a friend’s house where there is no WiFi hot spot to connect to.  You need to show them something on the computer which requires Internet access.  This solution is the solution to that conundrum.  PDAnet has a trial period and after that you need to pay a modest one time $29 fee for continued full access.  You can continue to use it free of charge but secure HTTPS sites will not be able to be accessed from the free version after the trial expiration.  You can still use it for regular HTTP access however.

NAT is most commonly used in a private IP network where the NAT device or server will forward packets between networks making all source packets look as if they originate from the NAT device or server itself.  After a reply is gotten, the NAT system reformulates the destination address which allows the packet to be delivered to the system that requested it.  This is a proxy system which is a good security measure.  A large amount of systems can access an outside network – usually the Internet – through a single IP address.  Since Internet IP addresses are rare and getting rarer, this system allows a person or corporate entity to have many non routable IP’s in their private network accessing the larger network through an ISP assigned IP address.