Archive for the ‘Networks’ Category

Femtocells, VOIP, and cordless phones synthesis?

Thursday, January 7th, 2010

It has been a big change taking a lot of time. The landline telephone network started development just a bit over 100 years ago. Cable TV is less than half that and its expansion into networking is less than half of that. Cell phones have an age similar to cable networking of only a couple of decades.

It was a big deal when cordless phones could replace the old telephone sets in homes. Now that technology is up to DECT 6.0 standards with many features and, just as that standard is taking hold, another technology is encroaching on its territory.

Cordless household phones were only a small step towards wireless freedom. Those phones have only limited range and are still rather bulky. Cell phones, on the other hand, can be used nearly anywhere and are small, convenient, and packed with many features that make them much more than just a telephone. That is why the wired connections to houses business is shrinking.

Back towards the 1970′s you had to have specially certified equipment to connect to the telephone network and that network was the only readily available public method for communications. That gave Amateur Radio operators headaches as they built the interface between their hobby equipment and the telephone networks to extent the utility of their services in emergencies. It also raised costs on early data modems and other equipment that connected computing devices.

That monopoly was broken and now the back end networks are separated from front end consumer access points. Ironing out the standards to keep all of these parts functionally integrated has been a difficult process and is still suffering rough spots. What has happened is that there are now many ways to get into and out of the back end network and cost and pricing pressures are stimulating innovation.

VOIP is old hat now. The next step may be that of circumventing the front end cell network to be able to use common cell phones to connect more directly to less expensive I’net service points while still retaining the cell network access. This is where the femtocell idea comes in. (see Airvana Femtocell Technology)

Femtocells have the potential to transform communications by making the mobile device the tool of choice even in home settings.  However, vendors and operators face substantial technical challenges to realize the potential of femtocells.  For example, femtocells will increase the number of base stations by several orders of magnitude over the existing “macro” base station infrastructures.  This increase will demand new approaches to areas such as mobility and interference mitigation.  At such volumes, femtocell vendors will also need to follow an aggressive cost curve.  Femtocells will require new approaches to installation and configuration, because they will be installed by non-technical users.

Where the shift occurs is in the purchase of I’net services via an ISP and then using various service providers for such things as addressing such as telephone numbers and access methods. The interface out the the PSTN (public service telephone network) is the province of VOIP providers and they use either computer audio (e.g. Skype) or dedicated phone set to I’net devices (e.g. Vonage, Teleblend) or phone set to computer interfaces (typically USB) like Magicjack. These devices make it possible to use an existing I’net backbone like a regular telephone and that means that the costs for long distance and other such features are paid for in a customized way between your ISP and your VOIP provider.

Now it looks like Magicjack is going to provide a femtocell option (CES PSA) to build on their POTS to USB service interface. This means that you can ‘introduce’ your cell phone to the femtocell and then your cell phone calls will use that access point rather than a cell phone tower when you are in range of the femtocell. Since you don’t access the cell network, your cell phone provider should not charge you for the use of the phone when using the femtocell. What that means is that your cell phone acts like an old cordless phone around home except that is will still work when you are away from home, will be more compact, and may still have many features the cordless doesn’t have.

The portability aspects for travelers also have interesting implications. The Magicjack is intended to be portable so it can be used wherever there is a decent high speed I’net connection. If their femtocell works the same way, it means that you can reduce cell phone costs when traveling if you have access to a motel or RV park or other public access broadband service with your laptop.

Exactly when this will happen is a question. Magicjack has promised number porting and Linux capable software as being available ‘Real Soon Now’ and the wait has been extended. Someday. And someday, the femtocell, too. It is coming together and the pace, if looking back, is breathtaking. But seeing what is in the pipe can still be a frustration of anticipation.

Telephone wiring and VoIP issues

Monday, September 14th, 2009

Michigan Telephone has an interesting page on How to Distribute VoIP Throughout a Home that is a reminder that things have changed a bit. It used to be the old red and green quad wire thing but now, it seems, cat 5 wiring is preferred for all house communications wiring. The history with color codes and issues is described. Other topics for good wiring are covered, too. Splices need to be done right. Isolating the VoIP lines from the telephone company covers the network interface methods the telco uses.

While written with VoIP in mind, there is a lot of good information about telephony issues that provides definitions and background and the issues that might arise. A lot of good ideas with the reasoning behind them can help in understanding modern telephone systems.

DreamHost emergency moves

Sunday, May 24th, 2009

DreamHost sent a note Friday morning that they had made an emergency move of my account to another server. That changed the IP addresses of all of my web pages and other services hosted on their machines.

It took until late afternoon before the web sites were again available.

It took until Sunday noon before e-mail services were up again.

DreamHost tech support asked for a traceroute output for the mail server. It went about fifteen hops and then timed out so they said it wasn’t them and to call Charter, my ISP to fix it. The problem with that was that the route got out of Charter’s network so it wasn’t them either. Oh, boy! nothing like a problem where everyone is pointing at the other guy and I am stuck in the middle and not able to address the problem.

I had always thought that subdomains would go to the primary which would then pass them down the line. This does not appear to have been the case. The subdomains to handle mail services and webmail seemed to have their own routing information on the I’net and that information did not get properly updated after DreamHost swapped servers on me.

Now to see if I can find out how this works…

OpenDNS

Wednesday, May 6th, 2009

A DNS or domain name server is the resource that converts your Inet address names to specific address numbers used to route traffic. When a new web page is put on the net, its name and address get circulated to all of the DNS, which is why it may take a day or two to access a new one. OpenDNS is a

leading provider of free security and infrastructure services that make the Internet safer through integrated Web content filtering, anti-phishing and DNS. OpenDNS services enable consumers and network administrators to secure their networks from online threats, reduce costs and enforce Internet-use policies. OpenDNS is used today by millions of users and organizations around the world.

Quick Online Tips has a good review of the features and capabilities – Use OpenDNS to Browse Faster, Safer, Fix DNS Errors

The default DNS you normally use is the one provided by your ISP. You will very likely find that changing the default to OpenDNS will get you faster access to web pages with fewer problems and less down time. OpenDNS is also a first step in blocking dangerous web sites to make your family network safer and more family friendly. The use of the service is free and you can set up an account to customize features and even collect statistics.

The business model seems to be similar to that of Craig’s List. Businesses that need a reliable corporate DNS with special features provide the rest of us a special free benefit.

Samba CIFS permission problems

Tuesday, April 21st, 2009

Samba, the implementation of Windows [Personal Computer or PC] type file sharing on Unix type machines, is a classic example of ‘east meets west’ in security models. Unix was always designed as multi-user and it has a clear separation between users and the computer. In the PC world, the culture started out as assuming the user owned the machine and everything connected to it.

For Unix based machines, connecting to a network simply extended its security model to a ‘network is the computer’ idea. In the PC world, it was a case of needing to address a new concern – that of distinguishing self from other. Logins came to the PC and, with that, a whole raft of options and ideas about how to control who could do what.

If security isn’t an issue, permission to do things to files and devices on the network isn’t much of a problem. Just leave the doors open. In Unix systems this means keeping the ‘everyone’ permissions wide open for each file or device. In the PC world, it means setting up shares without conditions. Even then problems can occur when trying to cross the divide.

For instance, it is a common problem when using rsync to backup a Linux file system to a CIFS (PC) share. That share is usually mounted on the Linux system at a point owned by the root user. It may be set wide open but that isn’t the whole story. If you try to run rsync as a non-root user, you might encounter errors that say you do no have permission to set certain attributes. To get around these errors, you have to either run rsync as root or to mount the CIFS share to a mount point you, rather than root, own.

Another common issue in blending Unix and PC security models is that of adding Unix ideas to the PC shares. These often have to to with the user and group identification method used in Unix systems. These ‘Unix extensions’ can mean that the PC share pays attention to Unix user and group ID numbers used to control file permissions in Unix systems. If the Unix clients trying to access the PC shares do not have carefully planned user and group ID numbers used consistently throughout the network, users can have problems when a mismatch causes permission problems. This is why the CIFS filesystem in Linux has options such as nounix, noperms, and so on.

Another method to turn off these Unix extensions to PC share features is to command “sudo echo 0 > /proc/fs/cifs/LinuxExtensionsEnabled” which changes a CIFS parameter. You may need to “sudo modprobe cifs” in order to start the module and get the proc variables established.

There is a lot more to this story …

Remote login, Q&D substitute for VNC on a LAN

Thursday, March 12th, 2009

In Ubuntu, you enable remote logins on a machine with System->Administration->Login Window in the remote tab to enable a server. Then all you need to do is hit the button at the lower left of the client login screen to select the login to a remote computer option.

Juliet Kemp describes this in Remote Graphical Desktop With GDM and KDM, Graphical Remote Control. The process involves setting an xdmcp enabled line in the GDM or KDMrc configuration files and then using “Xnest -query remotemachine.com -geometry 1280×1024 :1″ to launch the remote login. Note that this command sets up a second X windows session on your computer as the :0 is your primary desktop. Then you can use the CTRL ALT F7 or F8 to switch between windows.

The big unknown is the host name or address of the server machine (remotemachine.com in the Xnest code example). When using the GDM client login, you can select from a displayed list of available servers. From the command line, you have to know it (and to spell it correctly!). That’s the dif between the GUI and command line approaches in general. There must be a utility to list available Xdmcp hosts – now to find it …

Working with web search engines

Wednesday, February 18th, 2009

A post about a Google (XML) Sitemaps Generator for WordPress was a good starting point for learning about this technology. Google has defined a sitemaps format to help their web crawlers index websites.

Google has unveiled a new Google Sitemaps program allowing webmasters and site owners to feed it pages they’d like to have included in Google’s web index. Participation is free. Inclusion isn’t guaranteed, but Google’s hoping the new system will help it better gather pages than traditional crawling alone allows. Feeds also let site owners indicate how often pages change or should be revisited.

The technical details of the format is described at sitemaps.org. It is an XML format with six attributes. From the FAQ

As with all XML files, any data values (including URLs) must use entity escape codes for the following characters: ampersand (&), single quote (‘), double quote (“), less than (<), and greater than (>). You should also make sure that all URLs follow the RFC-3986 standard for URIs, the RFC-3987 standard for IRIs, and the XML standard.[link to rfx 3986 fixed]

This is one of several forms of website meta data that need to be understood and used in creating a successful website. The “robots.txt” file is explained at Thomas Brunt’s Outfront or robotstxt.org

The /robots.txt is a de-facto standard, and is not owned by any standards body. There are two historical descriptions:

In addition there are external resources:

The /robots.txt standard is not actively developed. See What about further development of /robots.txt? for more discussion. The rest of this page gives an overview of how to use /robots.txt on your server, with some simple recipes. To learn more see also the FAQ.

It should be noted that this is not content creation or web software development. It is about how to define behind the scenes website data that coordinates your website with other web services. From here you can start to look at using RSS feeds and similar technologies to improve your website.

This is a field undergoing a significant rate of change. It, like many in information technology, can be hacked at by amateurs but those amateurs are going to be missing an awful lot of the implications of their work until they become familiar with the underlying technological concepts and ideas.

OpenDNS and privacy issues

Sunday, February 8th, 2009

The Slashdot entry OpenDNS To Block and Monitor Conficker Worm is interesting not only as an example of how a free service can innovate in being useful and in making money but also in how people worry about it.

The story is about how the OpenDNS service can be used to help organizations control Cornficker intrusions by detecting access to problematic web addresses and notifying system administrators. The worry warts take note that OpenDNS can watch every move you make and can re-route your traffic, which it does to its advantage when you try to access an invalid URL.

For some, the OpenDNS assistance in finding proper URL’s and other services is a benefit. The service is often more reliable, for instance, than Charter’s default DNS service. For others, there is worry about being watched and monitored even if they aren’t but can’t tell because there isn’t any way to tell until it is too late.

I think that those worried about privacy should just behind closed doors. If you want to use public resources you are going to be visible in public. Make your presence decent and participate in proper accountability and awareness to help reinforce a trust that is necessary for effective social interaction.

Shutdown problems with CIFS shares

Monday, January 19th, 2009

If you have CIFS shares mounted in Ubuntu you might have a long wait at shutdown. According to Sander Marechal, this is because the CIFS driver is a bit unusual and doesn’t reside in kernal space like most drivers. The shutdown process first ends all applications then unmounts network drives then local drives. The CIFS driver gets shut down with the applications but the system still thinks it has network drives to shutdown so it gets confused. See his explanation at Lone Wolves Automatically mounting and unmounting Samba/Windows shares with CIFS.

A script to handle this is provided in the Ubuntu Forums how to: automatically umount cifs partitions to take care of this. See 33 for an explanation of what it does.

One of the interesting tidbits about the Sys V type init.d startup and shutdown process is involved in properly installing this script. That is the use of the update-rc.d command. It appears that this command is used to synchronize the links in the various run level directories with the library of scripts in /etc/init.d/

Now to see if this works.

Nov 4 results: FCC opens path

Wednesday, November 5th, 2008

On November 4 the FCC cleared the way for the use of TV channel guard bands for I’net access. As TV moves from analog to digital, the need for an empty space, a guard band, between channels to prevent them from interfering with each other is reduced. Getting more TV in less spectrum is the promise of digital TV and this FCC action is an attempt to utilize that promise. It is a second step after auctioning off the upper UHF channels (51 to 80) freed up in the planned transition.

The idea on this use of the guard bands for I’net access is that, while the equipment must still be FCC approved, transmissions do not need a license. There will have to be provision to make sure the equipment does not interfere with nearby digital TV transmissions. This will likely mostly depend upon a location database more than it will signal sensing.

A key feature of using this part of the spectrum is that it is at a lower frequency than the traditional 2.4 GHz WiFi which means it will suffer less attenuation getting into and out of buildings and other solid objects. It will tend to have a longer range with some trade-off for lower data rates.

Joshua Breitbart has a good description in Open the airwaves and the sky’s the limit and why the ‘free is good’ folks are very happy.

Wireless access is not a full replacement for wired connections, but it is a much cheaper way to bring people the Internet. Mobile phones are far more widespread than in-home computers with broadband connections, especially among the groups currently marginalized from the Internet. …

Once you don’t have to rely on big, corporate license-holders to get a connection, you can start to invent entirely new devices and applications. The FCC used the same kind of open platform for innovation with the 2.4 gigahertz band. That led to an astounding array of inventions — cordless phones, remote controls, microwave ovens, and wi-fi routers — all sharing one tiny piece of the airwaves.

Google has been one the primary backers of this idea. Catherine Holahan described their effort in Business Week’s Google’s Plans for the Space Between Your TV Channels

Companies such as Clearwire are providing I’net service similar to that envisioned by Google. This FCC action will make that type of service easier to implement over more area.