Understanding VOIP

What is VoIP?
A: VoIP is technology that enables one to make and receive phone calls thru the Internet instead of using the traditional analog PSTN lines.

What are the advantages of VoIP over analog PSTN lines?
A: The main advantage of VoIP over PSTN lines is cost: it’s cheaper! Other advantages of VoIP are: digital features not commonly available on PSTN lines such as voicemail, caller ID, conference, music-on-hold, etc.

What type of service and equipment are needed for VoIP deployment?
A: The following equipment and services are required for VoIP deployment: a high-speed Internet connection, an IP Phone or an ATA with a regular phone, and a VSP account. A VoIP router can also help.

What are VSPs?

A: VSPs are the next generation telcos that provide interconnection between VoIP and PSTN networks. They allow call origination and termination between these two networks.

Can I make and receive calls to/from PSTN lines using VoIP?
A: Absolutely! VoIP users can definitely make and receive calls to/from PSTN lines. Any type of calls (e.g. local, long distance, international, etc.) are allowed. This requires an account with a VSP that provide termination, and they are available on a subscription basis.

How I can make/receive free VoIP calls to/from remote location?
A: Making and receiving free VoIP calls can be made possible by signing up with VoIP Service Providers such as Free World Dialup (FWD) that allow unlimited VoIP calling. These providers will sometimes allow making/receiving free VoIP to PSTN calls (and vice versa). In addition, VoIP end user devices such as ATAs and IP phones can be set up to make point to point VoIP calls between one another.

May I keep my existing phone number when migrating to VoIP?
A: Most VSPs will allow you to keep your existing PSTN phone number for VoIP. However, you will need to check with the provider since not all of them offer this service. A signed “Letter of Authorization” will be required by the provider when keeping your number.


What is an IP phone?
A: It’s a phone with integrated VoIP capability. They come in two flavours: software and hardware. The software IP phones (aka softphones) require a PC and either a soundcard with speakers and microphone, or a compatible USB phone.

Should I use an ATA or an IP phone?

A: It depends on your preference and budget. An ATA will allow you to use analog phones for VoIP. While this might save money, they do not have one touch feature keys (e.g. transfer, hold, etc). On the other hand, using IP phones will provide more features that are similar to digital phones.

Do I need a computer to make/receive VoIP calls?

A: The answer depends on whether or not you will be using a softphone with your VoIP integration. If softphones are used instead of physical phones or ATA devices, then computers are needed.

What is a VoIP router? Do I need one?
A: A router connects IP networks together. When the IP phone or ATA is connected to the network, it will have to be through a router. Some IP phones and ATAs have embedded routing capabilities and their use is recommended because they have VoIP prioritisation. This helps ensure VoIP quality, regardless of other traffic. See [H6].

Can I use dial-up for VoIP or do I need broadband?

A: Dial-up can be used for VoIP when necessary or if its the only type of connection available. However, a broadband connection is recommended since VoIP usually requires higher bandwidth than what dialup can provide.

Can I surf the web during VoIP calls?
A: Yes, VoIP allows web surfing while making and receiving VoIP calls simultaneously. However, since the connection is shared, the quality of VoIP might suffer if the bandwidth allocated drops below certain limits. One way to ensure that VoIP gets sufficient bandwitdh is using QoS, which is built into most VoIP routers.

Can I use VoIP for all the phones in my residence?
A: Definitely, VoIP can replace every single phone in your residence. Both ATA devices and IP phones can be used instead of regular analog phones. This setup requires an account with a VSP.


What are IP PBXs?
A: IP PBXs (Private Branch Exchanges) are complete phone systems that provide advanced telephony features and services between VoIP and PSTN networks. Common features and services include: call transfer, conference, voicemail, music-on-hold, auto-attendant, and auto call routing.

What are VoIP Gateways?
A: VoIP gateways are devices that take analog voice signals and convert them to IP for transport over the LAN or WAN.

What are FXO and FXS ports?

A: Foreign Exchange Office (FXO) ports are interfaces used to connect with PSTN analog lines. Foreign Exchange Station (FXS) ports are interfaces used to connect with end user devices (e.g. phone or fax).

What are PSTN failover lines?
A: PSTN failover lines are used as backup connections in the event your VoIP or Internet connection goes down. These are optional ports on ATA devices or IP phones that connect directly to the analog PSTN lines coming from the telephone company. This setup requires having both a regular analog telephone line and a VSP account.

Which VoIP signaling protocols are commonly used?
A: VoIP signaling protocols are used to setup and tear down calls, carry the required information to locate end users, and negotiate device capabilities. The following list shows the most common VoIP signaling protocols available: SIP (Session Initiation Protocol), H.323, Cisco SCCP (Skinny Client Control Protocol), IAX (Inter-Asterisk Exchnage), and MGCP (Media Gateway Control Protocol).

Which VoIP codec should I use?

A: VoIP codecs convert analog voice signals to their digital encoded version. Codecs vary in size, sound quality, bandwidth and computation requirements. The most common VoIP codecs currently available are: G.711 (alaw & ulaw), G.723, G.726, G.729, GSM, and iLBC.

What are Gatekeepers and Registrars?

A: Gatekeepers and Registrars are gateways that provide authentication, authorization, call control and call routing, and session invites for end user devices.

VoIP = Voice over Internet Protocol
VSP = VoIP Service Provider
PSTN = Public Switched Telephone Network
ATA = Analog Telephone Adapters
QoS = Quality of Service
Please also see the “Voice Over IP Reference Page” – http://www.protocols.com/pbook/VoIP.htm

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