Tag: Kamailio
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Fixing SIP header addresses – Contact headers
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Part 3 of this series of articles focusses on the Contact header. In particular, I examine the use-cases where it is necessary to “fix” (or alter) a received Contact header. Contact headers work in close combination with Record-Route and Route headers in a mechanism known as loose routing. To get the most from this article some prior knowledge is required about loose routing, so if you are not already well acquainted with this subject please head…
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Contact and Record-Route headers explained
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Diagnosing some problems in the world of VoIP requires close inspection of the SIP messages being exchanged, but there are many occasions where a good understanding of loose routing will be invaluable. The headers that underpin loose routing are Contact, Record-Route and Route. In this post, I explain how they work and provide some insight into the way they interact. Some Acronyms and terminology UAC UAS SIP Proxy URI * Sequential Request User Agent Client (for…
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What is OpenSIPS?
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There are a number of open source applications available that are used to build IP Telephony solutions. OpenSIPS may not be as well-known as Asterisk, but it is widely used by service providers as a core part of their infrastructure because of its robustness, speed and capacity. In this article I will review the history of OpenSIPS, explain what it is, what features it offers and its core operational roles. This will include a summary of…
