Leased Line / Connectivity Glossary

Glossary

A

ATM
Asynchronous Transfer Mode is a switching technology potentially capable of switching all types of telecommunications traffic.

B

Backbone
A segment of a network that's often a higher speed than the rest of the network and connects all the other segments. If you don't have a fast backbone, your network will lag. That's why a lot of ISPs are constantly restructuring their backbones.

Backbone Network
The name given to a core network connecting all of the larger sites and concentration sites.

Bandwidth
The amount of data that can be sent through a given communications circuit per second.

Bandwidth on demand
Specifically designed to cater for organisations who require high bandwidth for peak times, or when transferring large files. In these cases, a second channel is opened to allow for the extra traffic. The second channel control is seamless to the end user, but there will be a higher ISDN charge. When the volume of data being transmitted is low, only the 64k portion of the ISDN-2 line would be used, saving on call charges.

Bit
Binary Digit -- A single digit number in base-2, in other words, either a 1 or a zero. The smallest unit of computerised data. Bandwidth is usually measured in bits-per-second.

Bit Error Rate
A quality measurement of how many bits are lost or corrupted in transmission.

Burst Traffic
The flow of Traffic increases, requiring more bandwidth. LAN devices can be used to grab the whole bandwidth for a very short period, resulting in peaks of activity.

Byte
A set of Bits that represent a single character. Usually there are 8 Bits in a Byte, sometimes more, depending on how the measurement is being made

Browser
An application that allows users to view and navigate the contents of the WWW.

C

CGI
(Common Gateway Interface) -- A set of rules that describe how a Web Server communicates with another piece of software on the same machine, and how the other piece of software (the "CGI program") talks to the web server. Any piece of software can be a CGI program if it handles input and output according to the CGI standard. Usually a CGI program is a small program that takes data from a web server and does something with it, like putting the content of a form into an e-mail message, or turning the data into a database query. You can often see that a CGI program is being used by seeing "CGI-bin" in a URL, but not always.

CIR
Committed Information Rate. The guaranteed bandwidth available over the virtual circuit. If the network has spare bandwidth, devices can burst above the CIR.

Co-location
Most often used to refer to having a server that belongs to one person or group physically located on an Internet-connected network that belongs to another person or group. Usually this is done because the server owner wants their machine to be on a high-speed Internet connection and/or they do not want the security risks of having the server on their own network.

Compression
This feature typically offers a 4:1 compression ratio depending on the type of file being handled and so increases the volume of data, which can be transmitted in a given time, as well as increasing efficiency and decreasing call charges.

D

Domain name
A domain name is another way of referring to the Internet address of a computer or group of computers on the Internet. Whereas an Internet address is made up of numbers (e.g. 124.2.35.6) and therefore difficult to remember, a domain name (e.g. company.co.uk) is made up of meaningful words. A domain name could be anything you like, for example, your own business name. Using a domain name makes for a memorable e-mail address, and if you have webspace, your website address (URL) will include your domain name (www.company.co.uk).

Domain name mail rewriting
Provides unlimited e-mail addresses all delivered to a shared mailbox. For example, you could have an e-mail address for every department (accounts@company.co.uk, sales@company.co.uk, or for members of staff john@company.co.uk, andrew@company.co.uk

E

E-1
A leased-line connection capable of carrying data at 2,048,000 bits-per-second. At maximum theoretical capacity, a E-1 line could move a megabyte in less than 4 seconds. That is still not fast enough for full-screen, full-motion video, for which you need at least 10,000,000 bits-per-second. T-1 is the fastest speed commonly used to connect networks to the Internet.

E-3
A leased-line connection capable of carrying data at 34,368,000 bits-per-second. This is sufficient capacity to support full-screen, full-motion video.

Encryption/Decryption
Encryption is the process of making information unintelligible to anyone not possessing the decryption key and algorithm.

Ethernet
A very common method of networking computers in a LAN. Ethernet will handle about 10,000,000 bits-per-second and can be used with almost any kind of computer. The most commonly installed Ethernet Systems are called 10Base-T and provide transmission speeds up to 10Mbps, also a fast Ethernet providing 100Base-T, a 100Mbps option.

F

Firewall
The firewall is a security device which helps prevent unauthorised computer users from accessing your LAN. By using password checks the firewall is useful for companies who feel that they might be a target for unauthorised users or who would like extra security added to their Internet connection.

Frame Relay
Connection oriented WAN which caters for bursty traffic. Strictly on interface standard.

G

G703
A physical layer transmission standard for private circuits which provides a time synchronous bit stream (isochronous ) service.

H

HDLC
High level Data Link Layer Control protocol is a standard for transmitting variable length packets over a data link

I

Internet
A Worldwide network of computers that communicate which each other using a common language called Transmission Control Protocol (TCP/IP). The Internet facilitates services such as e-mail, the World Wide Web (WWW), the transfer of files (FTP), and Internet Relay Chat (IRC). Growth is estimated at about 1 million new users per month.

Intranet
A private network that allows users within a given organisation to use Internet related technologies.

IP addresses
A unique string of numbers separated by dots making four sets. This number identifies each computer on the Internet.

ISDN-2
This provides two 64k digital phone line 'channels' which provide faster and better quality. BT or your preferred telco service provider can arrange installation for you. ISDN can transmit data four times faster than a normal telephone line significantly reducing call charges.

K

kbps
1024 bits of information every second.

L

Latency
A measure of the transit delay across the network.

Leased-line
Refers to a phone line that is rented for exclusive 24-hour, 7 -days-a-week use from your location to another location. The highest speed data connections require a leased line.

Local loop
The connection between a customer's building and the local point of presence.

M

Mbps
1,048,576 bits per second.

Modem
A device that uses a telephone line PSTN or ISDN to connect one computer to another.

Multimedia
Information which combines at least two of the following : text, image, sound, animation or video.

N

NAT
NAT is an acronym for Network Address Translation. It is a commonly used IP translation and mapping technology. NAT acts as an interpreter between two networks. It sits between the Internet and your internal network. The Internet is considered the 'public' side and your home network is considered the 'private' side. When a computer in the private side request data from the public side (the Internet), the NAT device will open a little conduit between your computer and the destination computer. When the public computer returns results from the request, it is passed back through the NAT device to the requesting computer.

Using a device or piece of software that implements NAT allows an entire home network to share a single internet connection over a single IP address. A single cable mode, DSL modem, or even 56k modem could connect all the computers in a small internal network to the Internet simultaneously.

NAT is built in to the most common Internet Connection Sharing technologies around. Microsoft has built their ICS around it and every Cable/DSL Broadband Router on the market accomplishes its job with NAT.

P

Packets
A unit of data sent across a network. If there is a large amount of data being sent at once, it is broken up into several packets and is reassembled when it reaches its destination.

Permanent Virtual Circuit (PVC)
A pre-established virtual circuit. See virtual circuit and Frame Relay.

POP3 mail
With a POP3 mail account, each user needs to dial into the mail server when they wish to check for mail or to send mail. Any e-mail sent to the POP3 mailbox will be stored until the next time the user logs in to check the mailbox. All Global Internet POP3 accounts are provided with unlimited extra e-mail addresses (firstname.lastname@domain.co.uk)

Private Circuit
A point to point connection providing a fixed amount of allocated bandwidth.

PSTN
Public Switched Telephone Network. This is the everyday network.

R

Router
A computer that directs traffic and moves packets of information from one computer to another, or between networks. A router saves money and offers performance benefits. It overcomes the need for separate ISDN-2 lines and adapters/ISDN cards for each user as all can share the same line. Your router will also provide full Internet connectivity to a LAN.

Routers
Connect different types of LANs and WANs, help resolve addresses, decide the route packets take through the network, enforce output queue priorities, enable the network to be broken down into manageable domains, provide security barriers and fragment/reassemble large packets where necessary.

S

Server
A computer, or a software package, that provides a specific kind of service to client software running on other computers. The term can refer to a particular piece of software, such as a WWW server, or to the machine on which the software is running, e.g. our mail server is down today, that's why e-mail isn't getting out. A single server machine could have several different server software packages running on it, thus providing many different servers to clients on the network.

Service level Agreements (SLA)
Defines how a service should be provided, paying particular attention to performance, detailing sanctions if performance is poor.

SMTP mail
With SMTP mail forwarding service, the collection of e-mail is automated. At pre-set intervals, the e-mail server on your LAN can be set to call the mail server to send and retrieve e-mail. Retrieved mail can be delivered straight to the recipient's workstation if your server/LAN configuration allows this. You will need a dedicated or shared server on the LAN, which connects to the router. And as with the POP3 version, an unlimited number of e-mail addresses may be issued.

Source Address
The network address of the sending devise.

T

TCP
Transmission Control Protocol is a transport layer (OSI layer 4) protocol which provides guaranteed delivery of packets.

U

UNIX
Became the de-facto standard operating system for mini computers. The objective was portability of applications. Several variants exist.

URL
Every page on the WWW has a specific address, the Uniform Resources Locator (URL). To find a page on the WWW you need to open your browser, type the URL into the address bar and hit return. The browser searches for the web page you specified, once it has been found, the page will appear on your computer screen.

V

Video Conferencing
Using telecommunications to see and talk to people at a remote location.

Virtual Channel
An individual connection within a virtual path.

Virtual Circuit
A connection where bandwidth is available on demand but not permanently allocated. A logical transmission path.

VPN
Virtual Private Network combines the features of a private network with the economy of scale and flexibility of using public switched services.

W

Webspace
This is your own space on the WWW, which can be used to advertise your particular products and services. Together the webpages are referred to as a website or just a 'site'. You can create your own website or commission an independent company to create one for you.

X

X.25
A type of packet switched network used extensively by Public Network Operations (PNOs) for public services and popular for transaction based private networks.

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