Analog communication has been around for many years, spanning the globe with longer, older cabling and switching equipment. However, the problems inherent to analog communication now seem to be surpassing its effective usefulness. Fortunately, other means of communication now exist to address the complications of analog transmission. Some of the newer engineering is digital and ISDN/xDSL technologies (covered in the next section).
Dial- up analog transmission transpires through a single channel, where the analog signal is created and handled in the electrical circuits. A modem provides communication emulation, in the form of an analog stream on both the dialing and answering networks. Telephone system functionality derives from analog transmissions through equipment switching, to locate the destination and open an active circuit of communication. The cabling, microwaves, switching equipment, and hardware involved in
analog transmission, by numerous vendors, is very complex and inefficient. These issues are exacerbated by the many problems rela ting to analog communication.
Problem Areas and Remedies
Some of the problems encountered in analog transmission include noise and attenuation. Noise is considered to be any transmissions outside of your communication stream, and that interferes with the signal. Noise interference can cause bandwidth degradation and, potentially, render complete signal loss. The five primary causes for noisy lines are:
• Heat exposure
• Parallel signals, or cross-talk • Electrical power interference • Magnetic fields
• Electrical surges or disturbances
There are some remediations for certain types of noise found in lines. Telephone companies have techniques and equipment to measure the strength of the signal and noise to effectively extract the signal and provide a better line of communication.
Attenuation derives from resistance, as electrical energy travels through conductors, while transmission lines grow longer. One result of attenuation is a weak signal or signal distortion. An obvious remedy for degradation caused by attenuation is the use of an amplifier. Consequently, however, any existing noise will be increased in amplitude along with the desired communication signal.
Placing a signal-to-noise ratio service call with your local telephone company is highly recommended for optimal signal strength and bandwidth allocation.
Public telephone networks were primarily designed for voice communications. To utilize this technology, modems were developed to exchange data over these networks. Due to the problems just mentioned in typical phone lines, without some form of error correction, modem connections are unreliable. Although many of the public networks ha ve been upgraded to digital infrastructures, users are still plagued by the effects of low-speed connections, caused by error detection and correction mechanisms that have been incorporated to new modems.
The most recent trick used to avoid upgrading available bandwidth by adding an ISDN line to achieve dial- up access, is to incorporate larger data transfers during the communication process. But before we explore the fundamentals of this new initiative, let’s review the maximum transfer unit (MTU).
Maximum Transfer Unit
The MTU is the largest IP datagram that may be transferred using a data link connection, during the communication sequences between systems. The MTU is a mutually acceptable value, whereby both ends of a link agree to use the same specific va lue. Because TCP and/or UDP are unaware of the particular path taken by a packet as it travels through a network such as the Internet, they do not know what size of packet to generate. Moreover, because small packets are quite common, these become inefficient, as there may be very little data as compared to large headers. Clearly then, a larger packet is much more efficient.
A wide variety of optimization software that allow you to optimize settings, such as MTU, that affect data transfer over analog and digital lines is available for download on the Internet. Most of these settings are not easily adjustable without directly editing the System Registry (described next). Some of these software packages include NetSonic (www.NetSonic.com), TweakAll (www.abtons -shed.com) and MTUSpeed (www.mjs.u-net.com). These utility suites optimize online system performance by increasing MTU data transfer sizes, Time -to-live (TTL) specifications detail the number of hops a packet can take before it expires, and provide frequent Web page caching by using available system hard drive space. System Registry
The System Registry is a hierarchical database wit hin later versions of Windows (95/98, Millennium, NT4, NT5, and 2000) where all the system settings are stored. It replaced all of the initialization (.ini) files that controlled Windows 3.x. All system configuration information from system.ini, win.ini and control.ini, are all contained within the Registry. All Windows program initialization and configuration data are stored within the Registry as well.
It is important to note that the Registry should not be viewed or edited with any standard editor; you must use a program that is included with Windows, called RegEdit for Windows 95 and 98 and RegEdit32 for Windows NT4 and NT5. This program isn’t listed on the Start Menu and in fact is well hidden in your Windows directory. To run this program, click Start, then Run, then type regedit (for Win9x) or regedit32 (for WinNT) in the input field. This will start the Registry Editor.
It is very important to back up the System Registry before attempting to implement these methods or software suites. Registry backup software is available for download at TuCows (www.tucows.com) and Download (www.download.com). An example of the Windows Registry subtree is illustrated in Figure 3.12. The contents of its folders are described in the following list:
Figure 3.12 The Windows Registry subtree.
• HKEY_CLASSES_ROOT. Contains software settings about drag-and-drop operations; handles shortcut information and other user interface information. A subkey is included for every file association that has been defined.
• HKEY_CURRENT_USER. Contains information regarding the currently logged-on user, including:
• AppEvents: Contains settings for assigned sounds to pla y for system and applications sound events.
• Control Panel: Contains settings similar to those defined in system.ini, win.ini, and control.ini in Windows 3.xx.
• InstallLocationsMRU: Contains the paths for the Startup folder programs. • Keyboard Layout: Specifies current keyboard layout.
• Network: Gives network connection information.
• RemoteAccess: Lists current log-on location information, if using dial-up networking. • Software: Displays software configuration settings for the currently logged-on user.
• HKEY_LOCAL_MACHINE. Contains information about the hardware and software settings that are generic to all users of this particular computer, including:
• Config: Lists configuration information/settings. • Enum: Lists hardware device information/settings.
• Hardware: Displays serial communication port(s) information/settings.
• Network: Gives information about network(s) to which the user is currently logged on. • Security: Lists network security settings.
• Software: Displays software-specific information/settings.
• System: Lists system startup and device driver information and operating system settings. • HKEY_USERS. Contains information about desktop and user settings for each user who
logs on to the same Windows 95 system. Each user will have a subkey under this heading. If there is only one user, the subkey is .default.
• HKEY_CURRENT_CONFIG. Contains information about the current hardware configuration, pointing to HKEY_LOCAL_MACHINE.
• HKEY_DYN_DATA. Contains dynamic information about the plug-and-play devices installed on the system. The data here changes when devices are added or removed on the fly.