Voice Over IP (VOIP) Protocols
Technology has changed. Maturing software and voice technology have met with
widely available High speed internet. It was a match made in heaven.
Gone are the days of poor quality internet phone programs. Today we have a
large variety of quality internet phone options.
Options are good. But sometimes it can be confusing with each technology speaking
a different "protocol". What is a VOIP protocol? It's essentially the behind the
scenes technology used to send your call from A to B. For a voice call to be
successful the technology (protocol) at both ends has to match.
Apples and Oranges. There are a few competing standards in the VOIP world. I'm not going to cover them all.
Just a few of the more popular ones.
Be cautious of vendors that have their own proprietary standards.
You may be stuck buying all your equipment from them or have difficultly integrating their
equipment with other vendors.
VOIP Protocol Round Up
The most common protocols are:
SIP: Session Initiation Protocol
All hail SIP! Sip is the most popular VOIP protocol in use today. Everything from soft phones,
PC phones, to Phone systems speak SIP. In theory most SIP devices can be made to play nice and
In reality some vendors have done a half ass job of implementing the SIP standard.
Do you need a "STUN" server? If you don't know what STUN is relax. STUN is SIP's voodoo to helps figure out what type of router or gateway you are behind so that everything magically works.
This is a popular protocol. Support is included in many software internet phones ranging from
NetMeeting, older versions of Messenger, and hardware IP phones.
However, most new products are using SIP so unless you have a strong reason to go with H.323 you
are better off going SIP.
IAX: Inter Asterisk Exchange
This protocol is "open" but not as much a standard as SIP or H.323. However, it has definite advantages
Disadvantages? This protocol is not as commonly supported. You have fewer choices of soft phones (Firefly).
Fewer Analog Telephone adapter choices (Digium's IAXy). This protocol is really only of use to people
who use the Asterisk phone system. However, this is one protocol to keep an eye on.
- Lower Bandwidth
- It only uses one UDP Port making it more firewall friendly
- Easier NAT traversal
- Ability to trunk multiple VOIP calls to the same office in the same data stream
MGCP: Media Gateway Control Protocol
This isn't very popular these days. Primus uses this protocol with its TalkBroad service.
Mitel IP (MiNET )
This is Mitel's proprietary standard. MiNET typically won't work with anything other than Mitel hardware.
For future upgradeability you are better off sticking with a
more supported standard, like SIP.
SCCP: Cisco® Skinny® aka Skinny Client Control Protocol
This is a proprietary protocol connecting the Cisco call manager and Cisco VOIP phones. This standard is also used by a few other vendors, including Asterisk.
The general consensus about Cisco IP Phones is that they are expensive but good. If you want to get the SIP version of a CISCO IP phone be careful. Some Cisco phones come in both a SCCP and SIP version. Rumour has it that you may have to kick up a fuss to get the SIP firmware without having to pay for support.
Skype is a proprietary protocol. It's rumoured to be a variant of
SIP with something similar to a "STUN" server.
Skype is the cool kid on the block. It's down side is that it doesn't really want to associate with
other protocols and products. I do have to give full marks to Skype for ease of use.
Sign up. Download. Install. Done! Like Vonage Skype has mastered the important element: making the product friendly and easy to use.
It's advised that you do yourself a favour and research compatibilty on the specific phones and phone system you plan to buy. Upgrading your phone to the latest firmware is usually advised as well.
Unless you have to work with older or proprietary VOIP technology you are most likely going to want
the most common protocol (SIP). However, if you are using Asterisk then IAX may also be of interest.