There are various methods to connect systems to a remote location. From the network layer up, a remote connection is the same as a direct LAN connection, but the data-link and physical layers can differ.
Public Switched Telephone Network (PSTN): PSTN is a telephone service and uses copper-based twisted pair cable. A modem can be connected to the line to transmit data to any location. Connections are fed into a centralized locale where calls are then converted to analog and routed to their destinations. Modems convert the digital signals to analog, and transmit them over the PSTN. PSTN connections are slow. The quality of the connection depends on location and the state of the cables.
Most modems support the Plug and Play standard. Networks can detect and install the correct drivers for it. With external modems, the IRQ and I/O address are designated to the serial port that links the modem to the system. The system is supported by two serial ports and is assigned to: COM1 and COM2 share IRQ4, and COM2 and COM4 share IRQ3. A chip, universal asynchronous receiver-transmitter (UART), maintains communication.
Virtual Private Network (VPN): VPN serves as the connection between a remote system and a server on a private network that uses Internet support. A remote user can access the Internet through a modem and connect to an ISP. A secured connection is then established between the remote system and network server to protect information that’s transmitted by using tunneling.
The protocol that allows tunneling is the Point-to-Point Tunneling Protocol (PPTP). PPTP works with PPP to secure a connection between the client computer and a server. Once tunneling is activated the system transmits data by encapsulating the PPP data.
Integrated Services Digital Network (ISDN): Developed to replace the analog telephone system. Digital Subscriber Line (DSL) and cable television (CATV) services are advanced systems with faster performance and cheaper than ISDN. No modem is needed with ISDN as it uses dial-up service and has connectivity with different sites. ISDN uses the same wiring as PSTN and is higher quality in terms of speed. Though it uses the same wiring, additional equipment is required at the terminal locations. The telephone company provides a U-interface with a four-wire connection. Because of the speed, the length of the connection is limited.
Digital Subscriber Line (DSL): Also referred to as xDSL, DSL is a broad label for an array of digital communication services that use standard telephone lines. Its data transmission is faster than both PSTN and ISDN. DSL operates at a higher frequency than standard phone services and supports special signaling schemes. DSL is a direct, stable connection. DSL services include: High-bit-rate Digital Subscriber Line (HDSL): Is commonly used by larger organizations in place of a dedicated leased line. HDSL has a max length of 12,000 feet and transmit at full-duplex at a rate of 1.544 Mbps when using two wire pairs.
Symmetrical Digital Subscriber Line (SDSL): Symmetrical DSL supports the same upstream speeds as its downstream speeds. The max length for a DSL cable is 10,000 feet and can transmit at 1.544 Mbps or 1.048 Mbps using a paired wire connection.
Asymmetric Digital Subscriber Line (ADSL): Asymmetric DSL has faster downstream rates then upstream rates. Downstream transmission rate of anywhere between 1.544 – 8.4 Mbps down and a max of 640 Kbps upstream. The maximum cable length for ADSL is 18,000 feet.
Rate-Adaptive Digital Subscriber Line (RADSL): Can adapt it’s transmission speed according to the type of traffic that is being sent over it. The transmission rates can vary from 640 Kbps to 2.2 Mbps downstream and 272 Kbps to 1.088 Mbps upstream. It has a connection length of 10,000 to 18,000 feet. Like ADSL, it is used for internet/intranet access, remote LAN access, virtual private networking, video-on-demand, voice-over-IP, however, the transmission speed is dynamically adjusted to match the link length and signal quality.
ADSL Lite: A low level internet connection solution ADSL Lite has a transmission rate of up to 1 Mbps down-stream and up to 512 Kbps upstream. It has a connection length of 18,000 feet.
Very-high-bit-rate Digital Subscriber Line (VDSL): has a transmission rate of 12.96 to 51.84 Mbps downstream and 1.6 to 2.3 Mbps upstream. It has a connection length of 1,000 to 4,500 feet.
ISDN Digital Subscriber Line (IDSL): has a transmission rate of up to 144 Kbps in full duplex; and a connection length of 18,000 feet.
Cable Television (CATV): CATV uses broadband transmission, which allows one network medium to carry multiple signals simultaneously. CATV can stream Internet data as fast as TV signals, however the connections are not secure. Users that access the network with Windows can see others on the same network. This obviously compromises security as the bandwidth is shared. Firewalls will help resolve this issue. A CATV connection can’t be used to connect a PC with office LAN.
Remote Access Requirements to Establish a Network Connection
The following is required to establish a remote network connection:
- Common protocols – computers that are connected have to share common protocols at the data-link layer and above. Both computers require a data-link layer protocol that supports point-to-point connections, such as PPP or SLIP.
The computers must share a common network and transport layer protocol for example, TCP/IP or IBX TCP/IP configuration – when using TCP/IP protocols to connect with the host network, a system must have an IP address and other configuration parameters required for that network. DHCP is utilized in most networks to automatically assign IP address configuration Most remote networking solutions enable DHCP to automatically assign configuration parameters.
Host and remote software – the remote system utilizes a client program that can set up a connection.
Security – protective mechanisms are required for the host computer and the other systems on the network it is connected with to administer access to the network resources.