Voice over IP: Security, stability, success

Summary:If you're thinking about voice over IP -- and sooner or later you'll have to -- we take a look at the steps involved in getting it set up and what's on offer from four major vendors.

Glossary of terms

  Voice over IP

 VoIP at a glance
 Getting started with VoIP
 Bandwidth issues

Cisco systems

 Final words
 Glossary of terms
 About RMIT
  • DTMF (dual tone multi-frequency). The system used by touch tone phones, where each key is converted to a predefined unique frequency or tone enabling the user to enter codes via their telephone's keypad to interface with electronic systems such as voicemail or electronic banking.

  • Forklift upgrade. Applied to legacy telephony systems too old or not able to be upgraded within an organisation. Therefore a forklift mentality is used: out with the old in with the new. Unfortunately in some VoIP deployments this may be the most practical -- if not cost effective -- solution.

  • G.723. Part of the H.323 protocol designed for voice/audio in particular and supports real-time encoding/decoding.
  • Gateway. The box that controls the links between IP and the normal telephony network, in many cases also controls the phone links and software such as voicemail.
  • Greenfields. A VoIP deployment where there is no other legacy VoIP and in most cases no existing telephony solution at all. For example, in a brand new development that is under construction, the business may make a conscious decision from the word go to deploy VoIP. If you are currently planning to expand and build, this is definitely something worthy of consideration.
  • H.323. A standard approved by the International Telecommunication Union (ITU) that dictates how video and audio streams across IP devices, in theory enabling two different devices to interoperate seamlessly.
  • Handset. The thing on your desk with the buttons and the banana-shaped device you hold to your ear.
  • IM (instant messaging). Enables the users to establish a private text-based chat over the Internet. Most IM systems have the ability for users of the system to indicate whether or not a they are available for instant messaging at any given time.
  • ISDN (integrated services digital network). A digital telephone technology standard that supports voice, video, and data calls at 64kbps.
  • Jitter. The slight variation of a transmission signal in time or phase that can introduce errors and loss of synchronisation. More jitter will be encountered with longer cables, cables with higher attenuation, and signals at higher data rates. Also, called phase jitter, timing distortion, or intersymbol interference (see www.femf.org/education/Summit2000syll/ottglossary.htm)
  • PABX/PBX (private automatic branch exchange). The main box that controls how calls are handled when coming into the site and out of the site.
  • PoE (power over Ethernet). The ability to run relatively low DC voltages over Ethernet cable to power devices such as wireless access points and VoIP handsets.
  • POTS (plain old telephone system). The slowest, oldest form of analogue telephone system still in use, mainly defined and hindered by its limited bandwidth of less than 50Kbps in most cases.
  • PSTN (public switched telephone network). The worldwide network of POTS carrying analogue voice data.
  • SIP (session initiated protocol). A standards-based protocol which is used for setting up IP-based communications like VoIP or IM sessions; controls the initiation of call setup, features, routing, and authentication between the endpoints.
  • Sniffing. Sniffers exist on the one hand to allow network administrators to monitor the quality of their network but on the other hand to allow hackers to intercept network traffic for their own use. Once the data has been sniffed and dumped to a file, the data can then be pieced together again. A very popular tool used to convert from unencrypted G.7x dumped data traffic to audio files is called VOMIT (voice over misconfigured Internet telephones) and can be found at vomit.xtdnet.nl.
  • Soft phone. An application that enables suitably enabled PCs or handhelds (generally those with a speaker and microphone) to act as an IP phone. Most of these applications have a graphical representation of a normal telephone handset to ease users' migration from one to the other.
  • Toll bypass. Some VoIP calls can be placed over the Internet bypassing the PSTN. These cost less than a call placed directly via the PSTN, effectively bypassing the traditional phone system altogether. While some savings can be made by this method, it certainly should not be the main reason why a business deploys VoIP.
  • VPN (virtual private network). A secure link or tunnel between two systems over a WAN that effectively simulates a LAN link.
  • WAN (wide area network). A network connecting the local area networks of several remote sites together via IP-based VPNs, leased lines, or other connections.

This article was first published in Technology & Business magazine.
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Topics: Networking, Reviews

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