ADSL
Asymmetric Digital Subscriber Line. What it's all about! A method for getting reasonably high data rates (around 1Mbit per second) down an existing telephone twisted pair wire. The asymmetric simply refers to the different data rates provided upstream and downstream.

ATM
Asynchronous Transfer Mode. Preferred transport Layer for ADSL.

BAS
Broadband Access Server. Exchange equipment providing the attachment point to which the customer's line is connected.

Contention Ratio
This is the ratio of customer connections to the local exchange bandwidth available at your specific connection point. For example 20:1 would allow, worse case, a 1Mbps down link to deliver as little as 50kbps (ie less than an ISDN line!). On average though it would be much better than this.

Copper Loop
The final leg of the PSTN/POTS network between the customer and his trusty telephone. The physical carrier used to transport the ADSL signal.

CPE
Customer Premises Equipment. Anything at the customer end needed to make the service work - usually it means the carrier service provider supplied it as part of the connection. For POTS it's simply the familiar box on the wall. For an ISDN line it would be the ISDN box (Highway or 2e) and possibly a router or TA. For ADSL it would be the splitter, router and/or other equipment supplied by BT as part of the carrier service.

DHCP
Dynamic Host Configuration Protocol. This technique allocates a variable IP address at the start of a connection. As customers cannot define ahead of time which address will be allocated, it is difficult, though not impossible, to run a server.

IP
Internet Protocol. The almost universal data packet format used to carry data over networks.

ISDN
Integrated Services Digital Network. The not-so-integrated and not-so-highspeed digital dial-up interconnect BT flogged before it got told to get its finger out and offer ADSL.

ISP
Internet Service Provider.

NAT
Network Address Translation. allows a whole network to hide behind a single or pool of IP addresses. Private address are translated to a fixed source address on outgoing traffic and then translated back on incoming traffic. This does not mean you can't run servers, it just makes it difficult! Whether you can or not is decided by your ISP. Often associated with DHCP

NTE
Network Terminating Equipment. The box on the customers' wall that terminates the wire or fibre connection.

POTS
Plain Old Telephone Service. The old fashoned analogue connection between your phone and the local exchange. Can be used to refer to any analogue telephony thing! (eg the POTS ports on the back of a ISDN TA, or on Home/Business Highway).

PPP
Point to Point Protocol. A common protocol for carrying IP traffic over serial connections.

PSTN
Public Switched Telephone Network. The familiar analogue telephone network (POTS).

RADIUS
Remote Access Dial In User Server. A central place where usernames and passwords get checked.

SP
Service Provider. Generic term for any provider of any service (sic).

Splitter
Generic term for any device that converts a single signal into two or more separate signals. In the ADSL context it splits combined signal into baseband (normal telephone signal) and ADSL carrier.

TA
Terminal adaptor. Used as a simple connection from an ISDN line directly to a PC via a serial or USB port. Sometimes used in the ADSL context for a similarly functional unit.

USB
Universal Serial Bus. An increasingly common PC interface format for local peripherals. Replaces separate serial, parallel, keyboard and mouse interfaces etc.

VSP
Video Service Provider.

WDSL
Wireless DSL The transfer of information without the need for wires, satillite, radio etc.

xDSL
Generic term for any/all of the Digital Subscriber Line (DSL) variants.