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15th July 2008
Stun Protocol details
As seen in previous article, STUN protocol plays an important role in VOIP implementations; to discover the presence of NAT and to learn and use the bindings allocate to the client by the NAT
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10th June 2008
STUN Protocol and VOIP Part 2
As seen in Part 1 of this article, STUN enables a SIP entity running behind a NAT to discover its public IP and what type of NAT is running on the gateway it is connected to. It also enables the SIP entity to discover which port external SIP entities can connect to
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22nd May 2008
STUN Protocol and VOIP Part 1
STUN stands for Simple Traversal of User Datagram Protocol (UDP) through Network Address Translators (NATs). Typically it is used in several different network implementations and scenarios, one of which is in VOIP implementations
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1st May 2008
Session Description Protocol (SDP) and VOIP Part2
When a SIP based VOIP call is established, the audio or video sent between 2 SIP entities or more is streamed. Since many different codecs are supported by different devices or software, and each individual SIP entity taking part in the call does not know the IP address
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18th April 2008
Session Description Protocol (SDP) and VOIP Part1
When media is streamed in a SIP based VOIP call, being audio, or video or both, one of the requirements is for the participants to know the media details, i.e. transport address, transport protocol, codec, ports and other session description metadata.
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5th April 2008
Direct SIP explained (Direct SIP URI dialing).
If your telecom solution is running an IP PBX, it is possible to have your telephone "number" identical to your email address. People using SIP based VOIP phones can call you by using your email address as dialing property.
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14th March 2008
Busy Lamp Field (BLF). How does it work?
Busy lamp field, BLF for short, is a light on an IP phone which tells you whether another extension connected to the same PBX is busy or not.
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23rd February 2008
Why do we need secure VOIP? - SIP over TLS and SRTP.
Sooner or later VOIP will be one of the targets for malicious users who are always looking for new sources from where to get confidential data. By capturing VOIP calls malicious users can listen to calls and gather other information about the calls as explained later in this article.
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10th February 2008
Table of common used SIP devices and software and if they do support encryption or not.
Table of common used SIP devices and software and if they do support encryption or not.
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