About SIP - The Protocol

This section is dedicated to all things related to the SIP protocol itself and you will find information ranging from the very basic use case of SIP, deep dives into areas such as the transaction state machine to issues with NAT & Firewall as related to SIP.

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SIP Basics

If you don't know what SIP is, what it is used for or why you should even care then this is the section for you. This presentation will go over the very basics of SIP and assumes no previous knowledge of SIP or really any other network experience either. Topics it will touch upon is:

  • What SIP is all about
  • SIP and sessions management
  • Basic call flow
  • Brief discussion of SIP messages
  • SIP and audio

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Transactions & Dialogs

This section is an introduction to SIP transactions and dialogs and is suitable for those who either are working with SIP at a basic level, perhaps debugging SIP scenarios, or people that just want to know a little more. If you wish to become a SIP expert, knowing transactions and dialogs is a must. Even if your life goal isn't to become an expert in SIP, knowing what transactions and dialogs are will be tremendously helpful as soon as you do anything related to SIP, such as developing your first little application using something like JSR289 or similar.

This presentation will go over:

  • What is a transaction.
  • When does a transaction begin and when does it end.
  • What is the relation between a dialog and a transaction.
  • When is a dialog established.
  • Why do we need dialogs?

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SIP Routing

To fully appreciate SIP you need to understand its routing capabilities and how they enable SIP to traverse a network. These capabilities also help SIP deal with common network issues such as NAT and firewalls. SIP's flexible routing also enables features like application composition, a very valuable asset when designing, implementing, and building a loosely coupled system.

This presentation is for those that are looking to get a deeper understanding of SIP. Perhaps you have been tasked to spin up a completely new SIP infrastructure at work? Then you really need to understand how SIP finds its way through a network. By understanding the routing decisions SIP makes, you will be successful in your next SIP endeavor.

Questions that will be answered:

  • How does a SIP request traverse the network?
  • How do we know which transport to use?
  • How do responses find their way back?
  • Any difference for in-dialog requests?

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For many years I designed & implemented a presence solution based off of the OMA Presence Enabler 1.0. While doing so I learned a lot about Presence and what started off as emails & discussions between colleagues, grew to presentations then to internal white-papers and eventually I decided to put it all together as a book. I never finished the project but decided to post it here in case someone finds it useful. Note: nothing really useful until chapter 3! :-)