Voice over IP Overview

I recently tried to google for "VoIP basics" and a few similar terms. The results were, uhm, unsatisfactory. The pages in the result set all seem to waste too much of the "real estate" with advertisement, the actual content is short and only touches the surface of individual topics.

So perhaps it might help if I write my own Voice over IP Overview. So far, I've covered the digitization of voice, audio codecs, latency and bandwidth optimization, and the Real time protocol. In the next piece, I would like to touch jitter, and then go straight to describing the main VoIP protocols, SIP, and H.323. After that, I would like to discuss for example the topic of VoIP vs. firewalls, and the additional protocols like H.248, IAX2, and SCCP.

What do you think? Will this be useful?

15 komentářů:

Codecs řekl(a)...

Hi valdmir!

Its really good info. i was wondering if you could tell me the pros and cons of iLBC codec.

recently i found good blog about pros and cons of speech codec at http://speechcodecs.wordpress.com/
but i couldn't found info about iLBC.

And is this iLBC codec is sellable or licensable? just like what other companies does at www.ipsupermarket.com

Vladimír Toncar řekl(a)...


The floating point implementation of the codec is available royalty free (see http://www.ilbcfreeware.org/). I cannot offer any direct experience with the codec but I would expect the claims about good quality and packet loss robustness to be true, given the slightly higher bitrate (13.33 or 15.2 kbps).

Anonymní řekl(a)...

Hi Vladimir,

I'm Jairo Cardona from Colombia South America, and I like to use this tutorial to teach h.323 with my students.

May I used this tutorial?


Jairo A. Cardona
Universidad del Norte

Vladimír Toncar řekl(a)...

Yes, feel free to use it in your course.

Anil Singhal řekl(a)...

Thank you..its was really useful.

Mikey řekl(a)...

hi first, i don't read this language hehe, i assume this was a post.

Well i readp SIP in you blog and YES this was the best so far.. Thank you and keep doing it. right now i am trying to build an app out of JAIN SIP simple call to my cellphone using Android like voip. but i am having still a lot of difficulty. ANyway more power!

-Mike ,from Philippines

Unknown řekl(a)...

hello Mr Toncar. I read your article about, "About Jitter".
first, thank you for this good and useful article.
I try to translate it to persian language.
in your article there is: "seach 20 milliseconds". I think your mean was "each" not "seach".

good luck

sip based voip řekl(a)...

Hi Vladimir! Great blog. Keep posting!

Regards, Nikki from voip-sip.org

Eugene Blanchard řekl(a)...

Hi Vladimir

Thank you for the excellent tutorial on SIP and VoIP. I was missing some key points to put it all together. You've done an excellent job in explaining it in simple and concise terms. I will post a link in the PBX in a Flash forums to share with others who use the open source Asterisk distribution. Thanks

Anonymní řekl(a)...

Hi Vladimir,
I just make your way through your H323Plus tutorial and it's really great! It really helps me a lot to get the basics behind this!
Keep up the great work!

Anonymní řekl(a)...

Some good info on various aspects of SIP. As a new beginner it is too much for me but the ground covered is vast. I agree that very few pages related to SIP on Web are useful. Recently I was lucky enough to find some basic Interview Questions on SIP :)

Anonymní řekl(a)...

This is extemely useful and simple to follow. It would be more helpful to us if you could include the video aspect as well.
Atleast the basics if not totally detailed.


DmB.UK řekl(a)...

Vladimir, very useful and fairly simple post. Thank you!
Could you recommend the best way to detect both call parties in H323?

stuchl4n3k řekl(a)...

Thank you, Vladimir, for sharing your insight. Your overview was very useful to me.

Unknown řekl(a)...

Very Useful Vladimir. Got all the information on VOIP Protocols in one place.