VoIP and the SME

Copyright © 2007, Gordon Henderson

A brief Glossary of Terms

• ADSL-MAX: The 2nd generation of ADSL in the UK. Supports incoming speeds up to 8Mbps and outgoing speeds up to 448KBps for domestic connections, and up to 830Kbps for the business version.

• Broadband: A high speed Internet connection.
  There are many technologies that can be labelled "broadband", the most common in the UK is Broadband Internet provided via a DSL connection, but there are cable and wireless systems also in use.

• DDI: Direct Dialling In-bound.
  With a DDI system, every phone in an SME can have it's own directly dialable phone number.

• DSL: Digital Subscriber Line.
  A method of superimposing a digital signal (which usually allows you to connect to the global Internet) over existing analogue (copper) telephone wiring.
  Further split into 2 categories; ADSL and SDSL. ADSL is Asynchronous DSL where the incoming and outgoing speeds differ, and SDSL is Symmetric DSL where the incoming and outgoing speeds are identical. Standard ADSL supports incoming speeds of up to 2Mbps and outgoing speeds of up to 256Kbps.

• Gbps/Mbps/Kbps: Giga, Mega or Kilo bits per second.
  A measure of speed of data over a digital connection. Kilo in computer terms usually means 1024 and Mega is 1024 * 1024, and Giga is 1024 * 1024 * 1024.
  Note that speed is usually referred to in bits per second, but data quantity is usually measured in bytes and typically represented by a capital letter G, M or K. E.G. GB. There are 8 bits to a byte.
  It's also important to note that disk manufacturers sometimes use decimal numbers - and this is sometimes referred to by using a lower-case "i" in the name. E.G. GiB. They did this so that you would get less for your money. A 100GiB drive (which they would advertise as 100GB) would contain 100,000,000,000 bytes of data rather than the usually recognised power of 2 quantity: 107,374,182,400.

• IAX: Inter Asterisk eXchange.
  An open standard designed to allow two (or more) Asterisk PBX systems to communicate with each other.

• IP: Internet Protocol.
  The low-level commands that your computers use to talk to each other over the Internet.

• IP Address: A unique number that every directly connected Internet device has.

• ISDN: Integrated Services Digital Network.
  This is essentially a digital telephone network. Between every BT exchange, data is carried digitally, and traditionally the data from the exchange to your premises is carried in an analogue fashion. ISDN is a way to extend the digital format back to your premises. In the UK there are 2 flavours of ISDN; ISDN2 and ISDN30 (Sometimes you'll see the letter "e" after these, but it's all the same) ISDN2 can carry 2 simultaneous telephone calls, while ISDN30 can carry up to 30. The telephone company can route multiple numbers down the lines, so it's possible to have an ISDN30 service with 200 (or more) telephone numbers. This would be used for direct dialling to every persons desk for example.

• ISP: Internet Service Provider
  The company that provides basic connectivity from your home/office to the global Internet

• NAT: Network Address Translation.
  A means that allows multiple computers on a private network to access the Internet through a single gateway device (Eg. an ADSL modem/router). The NAT function is carried out by the gateway device.

• PABX: Private Automatic Branch Exchange.
  A small office telephone exchange device. Connects incoming calls to extensions, manages voicemail, lets extensions connect to each other and much much more.

• POTS: Plain Old Telephone Service.
  This is a common name for what we'd simply call a "phone line", or a "land line". It represents and analogue connect from a wall socket to the local telephone exchange.

• PSTN: Public Switched Telephone Network
  Ie. The "normal" telephone network in the UK which is made from the telephone networks belonging to BT, Telewest, NTL, Cable&Wireless, and several other telecom companies connected together.

• QoS: Quality of Service.
  A method of giving a certain Internet based service a guarantee of service availability. Eg. on a busy Internet connection, you may wish to give a higher priority to voice traffic than web or email traffic to help voice communications work without any disconnections.

• SIP: Session Initiation Protocol.
  A way to let to communication devices talk to each other to enable them to setup a communications path between them. SIP does the signalling, but doesn't carry the actual data.
  SIP is an open standard defined in RFC3261.

• Skype: A proprietary VoIP system.

• SLA: Service Level Agreement.
  A measure of how confident the provider of the service is that their system won't fail, or when it does fail, how long they will take to fix it, and what penalties they may forfeit should they not meet the SLA.

• VoIP: Voice over Internet Protocol
  A way of transmitting speech over the global Internet, or over a private IP network.

• VPN: Virtual Private Network
  A way to connect offices together over the global Internet in a way that makes it looks like they have a direct and connection.

• Wi-Fi: Wi-Fi is not an acronym, but rather a name or word which is easier to say than IEEE 802.11. It generally means wireless Internet connection. It comes in various formats and frequencies. "b" is the lowest-level standard, but others that currently exist include "a", "g" and "n".

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