It is not easy to troubleshoot problems related to remote access connections as various factors such as physical connection and type of remote access has to be taken into consideration. You must also ensure that all remote connections share number of common areas. The areas to be considered are explained as follows:
Physical remote connection not running
The signals that run between your PC and other connections are called as the physical connection. This includes telephone lines, such as PSTN, DSL and Ti or coaxial cables or cable modems and also the signals they carry. The physical remote access connection depends on the type of connection. The following are the possibilities:
1. You can check the dial tone if it’s a PSTN line. Absence of the dial tone indicates that the modem is unplugged from the phone jack.
2. Cable and DSL connections are virtually identical. This is because of the LEDs on the cable or DSL modems are almost same. If these LEDs are off, the connection should be reset.
3. CSU/DSU is the place to check for the connection if Ti or other high end connections are used. Channel Service Unit and Data Service Unit are two separate devices but they are considered as one. The terminal and the digital line are connected using a device called CSU. Protective and diagnostic functions for telecommunication lines are performed by DSU. It can be considered as a very high powered and expensive modem. LED is present on every CSU/DSU. A Ioopback or loop test of the line has to be performed if this LED shows no connection. The loop test is performed by the local exchange carrier. To verify that the connection to other CSU/DSU is in good order, all CSU!DSUs have some form of self-test
Remote Access Methods
The different remote access methods used for remote access connectivity are:
a. Using phone lines and modems
b. Using ISDN lines
c. Using X.25
d. Using VSAT
These remote access methods are explained as follows:
a. Using phone lines and modems — The most common dial-up connections are made using a standard analog telephone line and a modem or using a cable modem such as Digital Subscriber Line (DSL). Standard analog phone lines available worldwide are called Public Switched Telephone Network (PSTN) or Plain Old Telephone Service (POTS). Most modems such as the internal modems are automatically detected.
b. Using ISDN lines — Integrated Services Digital Network (ISDN) lines are used to enhance the connection speeds. For network connections, a local telephone line is used by ISDN. It provides end-to-end digital
connectivity between the computer and a remote computer or a network. It is slower than LANs which are supported by high-speed data communications technology but faster than analog telephone lines. An ISDN line must be installed at the client’s site and at the remote access server by the phone company. An ISDN adapter must also be installed.
c. Using X.25 — The data is transmitted along with a packet-switching protocol using an X.25 network. It is a standard for packet-switching network.
d. Using VSAT - VSAT is an abbreviation for a Very Small Aperture Terminal. It is basically a two-way satellite around station with a less than 3 meters tall (most of them are about 0.75 m to 1.2 m tall) dish antenna s-ationed. The transmission rates of VSATs are usually from very low and up to 4 Mbit/s. These VSATs’ pr mary job is accessing the satellites in the geosynchronous orbit and relaying data from terminals in earth to other terminals and hubs. They will often transmit narrowband data, such as the transactions of credit cards, polling, REID (radio frequency identification) data, and SCADA (Supervisory Control and Data Acquisition), or broadband data, such as satellite Internet, VolP and videos. However, the VSAT technology is also used for various types of communications. In 1985, the current world’s most used VSATs, the Ku band (12 to 14 GHz) was co-developed by Schlumberger Oilfield Research and Hughes erospace
A private communication link between two companies is called as a dedicated connection. It is a permanent connection. It is always available for use as it is hired from the telephone company. different workstations are connected to the Internet.
A company uses a dedicated connection for the following purposes:
Reduce the telephone bill — When a user wants to connect to the Internet very often Connect at higher speeds — To establish higher connection speeds than regular dial-up.
The permanent connection between two remote networks is called the dedicated connection. It can be divided into two groups such as dedicated private connections between two locations and the dedicated connections to the Internet. Dedicated private connections demonstrate themselves as two locations interconnected by a high speed Ti line connection. Each end of Ti line goes into the router after passing through a CSU/DSU. CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interlace device used to connect a Data Terminal Equipment device or DTE, such as a router, to a digital circuit, for example a Ti or T3 line. These types of dedicated connections are expensive and are used only by large organizations that need the Dedicated bandwidth. Individual computers on the network cannot see these connections. No special remote connection configuration for the inividuaI systems is required. However there may be some configuration of DHC DNS and WINS servers required to ensure that the network runs properly. Cable modems and DSL have made dedicated connections to the Internet inexpensive and very popular. You do not have to configure much in these connections. Many cable and DSL providers give an installation CD that includes testing software, PPPoE login support, e-mail clients and software firewalls. The first version of Windows to come up with the broadband support wizards is Windows XP.
The oldest, cheapest and the most common way for home and small office users to connect to the Internet is just dialing up to the Internet. To create a connection to your ISP some method is required by the dial-up. Some information is needed by the connection to work properly. The information needed is as follows:
1. The telephone number to dial
2. The modem to use
3. User name and password provided by the ISP
4.Type of connection such as PPP or SLIP
5.IP information provided by the ISP
You can also have more than one dial-up connection to the Internet. The operating system you use have to create a way to store multiple connections from which you can choose the’appropriate one.
Using Remote Access
There is a great need for people to be able to access files and resources over a great distance. WAN connection is used in remote access which allows computer to log on to the network from the other side of the city, state or even the globe. It is important that the information remains accessible when people travel from one place to another place. Remote access enables users to dial into a server at the business location and log in to the network as if they were local to the user.
Communication established with a distant computer system or computer network is called as remote access. Remote Access, the remote computer becomes a host on the network. To connect to the network, a computer, a modem or some remote access software is needed.
Types of Remote Access Connectivity
1. Dial-up remote access
2. Virtual Private Network (VPN) remote access — Using an Internet connection to connect to a private network. A virtual point-to-point connection with a remote access server which is acting as the VPN server. An IP Internetwork is used by a VPN client to create the VPN remote access.
3. Dial up to the Internet — Using a dial-up connection to connect to your ISP
4. Dedicated Connection — Using a non-dial-up connection to another private network or the Internet.
Dial up remote access (Private Dial up)
A remote system is connected to a private network using a private dial-up connection. It requires two systems such as a remote access server (RAS) and a client running dial-up network. RAS in Windows is a server that is dedicated to handle users. These users are not directly connected to a LAN but they need access to file and print services on the LAN from a remote location. For example, consider a user dialing into a network from home using an ISDN connection or an analog modem. The user then dials into a RAS. The user can access shared drives and printers only after he is authenticated. For this, a RAS server system must be set up in your LAN. This system should handle password authentication and should also accept the incoming calls. You must ensure that your remote access server is using the TCP/IP protocol for its network communications as it is most widely used. The server should also be configured to set the dial-in rights and permissions for the user.
The creation of the client side of a private dial-up connection is similar to setting up a dial-up connection to the Internet. However there is only one difference between the two. Instead of using an ISP to tell you what IP settings, account name and password to use the RAS server administrator tells you this ntormation.
For centuries light wave transmission has been used. To connect the LANs in two buildings using lasers on their rooftops is the most modern application of light wave transmission. These lasers follow a unidirectional path. Thus, each building should have its own laser and its own photo detector. light wave transmission technology has the following advantages:
1. It is a cost effective solution.
2. It offers very high bandwidth.
3. It is very easy to install.
Electromagnetic (EM) Waves
When energy is traveled through a material medium or through free space in the form of electromagnetic waves, it is called as an electromagnetic (EM) radiation. Radio waves. visib’e ght. IR. ultraviolet radiation, X rays and gamma rays are all examples of EM waves. Reflection, refraction.Interference and diffraction are some of the wave-like properties that EM exhibits. All types of EM radiation travel at the same speed but all vary in frequency and wavelength.
Types of radiation in the EM spectrum
EM radiations are of two types, visible light and radio waves. Visible light is the energy that travels and spreads out. Radio waves come from a radio station. The different types of radiation in the EM spectrum, in order from the lowest energy to the highest are as explained as follows:
1. Radio It is a form of radiation which has the lowest frequency and the longest wavelength. Radio waves are emitted by radio stations and stars in space. The composition of these stars and gases can be studied with the help of these waves.
2. Microwaves — It is an EM radiation which has a longer wavelength than visible light. They can be used to study the Universe and communicate with’satellites in the Earth orbit.
3. Infrared — Wavelengths longer than the red end of visible light and shorter than microwaves (roughly between 1 and 100 microns) is an IR radiation. In space, the dust between the stars can be mapped using the lR light.
4. Visible Light — EM radiation at wavelengths which the human eye can see is called visible light. This radiation comprises of colors ranging from red (longer wavelengths) to violet (shorter wavelengths).
5. Ultraviolet — They are having radiations at wavelengths shorter than the violet end of visible light. UV radiation is emiffed by stars and other hot objects in space.
6.X-rays — Radiation of very short wavelength and very high energy is called as X-rays. They have shorter wavelengths than ultraviolet light and longer wavelengths than gamma rays.
7. Gamma rays — They are having highest energy and shortest wavelength EM radiations. Gamma-rays are emitted by radio active materials.
Infrared (IR)
Omnidirectinal — It is also known as broadcast. In this system, a scattered infrared technology is used. To provide an environment for mobile devices, the light reflects off all available surfaces. The data transfer speed is less than 1 Mbps. Sunlight affects these systems. These systems are simple to install as no alignment is required.
Reflective — It uses optical transceivers. These are placed near devices that transmit data to a common location. This data is then redirected to the receiving device.
Applications
It has an excellent potential for data transmission. A wide infrared band of 400 THz can be used for this purpose. Digital data can be transmitted with a very high data rate using such a wide bandwidth. Standards have been established for using IR signals for communication between various devices such as keyboards, mice, PCs and printers. These standards have been published by Infrared Data Association (lrDA) which is an association for sponsoring the use of IR waves. A wireless keyboard can communicate with a PC using a special port called the IrDA port which is provided by some manufacturers.
Disadvantages of infrared
1. It does not have any penetration ability.
2. When exposed to light, IR signal goes weak. To resolve this problem they should have very high output.
3.Very expensive when used over large distances.
Uses of microwave
Microwaves have various applications in different fields. The different uses of microwave are as follows:
1. Microwave passes easily through the earth’s atmosphere with less interference and thus it is used in broadcasting transmissions. They are widely used in television news to transmit a signal from a remote
location to a television station from a specially equipped van.
2. Lower microwave frequencies are used in the cable TV and Internet access. GSM, a mobile phone network also uses the lower microwave frequencies.
3. Microwaves can be used to transmit power over long distances.
Unidirectional Antenna
Unidirectional antennas that send out signals in one direction are needed by microwaves. Unidirectional property has an advantage as it enables you to align a pair of antennas without interfering with other antennas. Microwave communication requires two types of antennas which are as follows:
Parabolic dish antenna — It is based on the geometry of a parabola. All lines intersect in a common point. This point is called as focus. Wide range of waves are caught by the parabolic dish and sent to a
common point.
Horn antenna In horn antenna, a stem is used which broadcasts the outgoing transmissions. A curved head then deflects these transmissions outwards in a series of narrow parallel beams. The received transmissions are collected by the scooped shape of horn and then deflected down into the stem.