Posts

H.323 - https://www.chinaroby.com/

Image
  H.323 https://www.chinaroby.com/ This International Telecommunication Union (ITU) protocol was originally designed to provide an IP transport mechanism for video-conferencing. It has become the standard in IP-based video-conferencing equipment, and it briefly enjoyed fame as a VoIP protocol as well. While there is much heated debate over whether SIP or H.323 (or IAX) will dominate the VoIP protocol world, in Asterisk, H.323 has largely been deprecated in favour of IAX and SIP. H.323 has not enjoyed much success among users and enterprises, although it is still the most widely used VoIP protocol among carriers. The two versions of H.323 supported in Asterisk are handled by the modules chan_h323.so (supplied with Asterisk) and chan_oh323.so (available as a free add-on). You have probably used H.323 without even knowing itMicrosoft's NetMeeting client is arguably the most widely deployed H.323 client. 8.2.3.1. History H.323 was developed by the ITU i...
Post a Comment
Read more

SIP - Protocol

  SIP The Session Initiation Protocol ( SIP ) has taken the world of VoIP by storm. Originally considered little more than an interesting idea, SIP now seems poised to dethrone the mighty H.323 as the VoIP protocol of choicecertainly at the endpoints of the network. The premise of SIP is that each end of a connection is a peer, and the protocol negotiates capabilities between them. What makes SIP compelling is that it is a relatively simple protocol, with a syntax similar to that of other familiar protocols such as HTTP and SMTP. SIP is supported in Asterisk with the chan_sip.so module. 8.2.2.1. History SIP was originally submitted to the Internet Engineering Task Force (IETF) in February of 1996 as "draft-ietf-mmusic-sip-00." The initial draft looked nothing like the SIP we know today and contained only a single request type: a call setup request. In March of 1999, after 11 revisions, SIP RFC 2543 was born. At first, SIP was all but ignored, as H.323 was consider...
Post a Comment
Read more

VoIP Protocols - https://www.chinaroby.com

  VoIP Protocols The mechanism for carrying a VoIP connection generally involves a series of signaling transactions between the endpoints (and gateways in between), culminating in two persistent media streams (one for each direction) that carry the actual conversation. There are several protocols in existence to handle this. In this section, we will discuss some of those that are important to VoIP in general and to Asterisk specifically. 8.2.1. IAX (The "Inter-Asterisk eXchange" Protocol) The test of your Asterisk-ness comes when you have to pronounce the name of this protocol. Newbies say "eye-ay-ex"; those in the know say "eeks." IAX [*] is an open protocol, meaning that anyone can download and develop for it, but it is not yet a standard of any kind. [*] Officially, the current version is IAX2, but all support for IAX1 has been dropped, so whether you say "IAX" or "IAX2," it is expected that you are talking about the V...
Post a Comment
Read more

Compiling Asterisk - chinaroby.com

  Compiling Asterisk Once you've compiled and installed the zaptel and libpri packages (if you need them), you can move on to Asterisk . This section walks you through a standard installation and introduces some of the alternative make arguments that you may find useful. We'll also look at how you can edit the Makefile to optimize the compilation of Asterisk. 3.5.1. Standard Installation Asterisk is compiled with gcc through the use of the GNU make program. Unlike many other programs, there is no need to run a configuration script for Asterisk. To get started compiling Asterisk, simply run the following commands (replace version with your version of Asterisk): # cd /usr/src/asterisk- version # make clean # make # make install # make samples Be aware that compile times will vary between systems. On a current-generation processor, you shouldn't need to wait more than five minutes. At Astricon, someone reported successfully compiling ...
Post a Comment
Read more

SIP Protocol - - from www.chinaroby.com

 www.chinaroby.com SIP The Session Initiation Protocol (SIP) has taken the world of VoIP by storm. Originally considered little more than an interesting idea, SIP now seems poised to dethrone the mighty H.323 as the VoIP protocol of choicecertainly at the endpoints of the network. The premise of SIP is that each end of a connection is a peer, and the protocol negotiates capabilities between them. What makes SIP compelling is that it is a relatively simple protocol, with a syntax similar to that of other familiar protocols such as HTTP and SMTP. SIP is supported in Asterisk with the chan_sip.so module. 8.2.2.1. History SIP was originally submitted to the Internet Engineering Task Force (IETF) in February of 1996 as "draft-ietf-mmusic-sip-00." The initial draft looked nothing like the SIP we know today and contained only a single request type: a call setup request. In March of 1999, after 11 revisions, SIP RFC 2543 was born. At first, SIP was all but ignored, as H.3...
Post a Comment
Read more

IAX protocol - chinaroby.com

  The IAX protocol was developed by Digium for the purpose of communicating with other Asterisk servers (hence " the Inter-Asterisk eXchange protocol "). IAX is a transport protocol (much like SIP) that uses a single UDP port (4569) for both the channel signaling and Realtime Transport Protocol (RTP) streams. As discussed below, this makes it easier to firewall and more likely to work behind NAT. IAX also has the unique ability to trunk multiple sessions into one dataflow, which can be a tremendous bandwidth advantage when sending a lot of simultaneous channels to a remote box. Trunking allows multiple data streams to be represented with a single datagram header, to lower the overhead associated with individual channels. This helps to lower latency and reduce the processing power and bandwidth required, allowing the protocol to scale much more easily with a large number of active channels between endpoints. 8.2.1.2. Future Since IAX was optimized for voice, it has rece...
Post a Comment
Read more

Linux Considerations

  Linux Considerations If you ask anyone at the Free Software Foundation, they will tell you that what we know as Linux is in fact GNU/Linux . All etymological arguments aside, there is some valuable truth to this statement. While the kernel of the operating system is indeed Linux, the vast majority of the utilities installed on a Linux system and used regularly are in fact GNU utilities. " Linux " is probably only 5% Linux, possibly 75% GNU, and perhaps 20% everything else. Why does this matter? Well, the flexibility of Linux is both a blessing and a curse. It is a blessing because with Linux you can truly craft your very own operating system from scratch. Since very few people ever do this, the curse is in large part due to the responsibility you must bear in determining which of the GNU utilities to install, and how to configure the system. If this seems overwhelming, do not fear. In the next chapter, we will discuss the selection, installation, and configuration of...
Post a Comment
Read more