At SIPit26 we began setting up a series of automated self-tests for IPv6, like we’ve done previously with SIP/TLS. We also integrated IPv6 in as many multiparty tests as possible, to see how IPv4 and IPv6 lived together.Some notes and experiences:

  • IPv4-only applications will receive IPv6 in messaging. Even if an application DO NOT support IPv6-native connections, the application will surely get IPv6 addresses in various places in the message. In SIP, a call may traverse an IPv6 proxy before reaching your IPv4 proxy or phone. Via headers will have IPv6 and maybe a record-route header too. All user agents needs to support this. We had at least one crash in a proxy that failed to parse an IPv6 address.
  • Placing an IPv4 call to a proxy that forwards the message to an IPv6 phone without handling RTP traversal leads to issues as well. The phone gets an IPv6 address in the Contact: header and failes to send the ACK properly. This happened with Asterisk. Because of parsing failure, the parser gave up and sent ACKs and BYEs to the wrong address.
  • We did successfully set up calls between IPv6 user agents using IPv6 proxys. The failures happened in the mixed scenarious.
  • When placing a call to a domain that was configured with both A and AAAA records for the SRV records, but only one of them responding, we noticed long timeouts before failover, if that even happened. Many discussions about this followed, which lead to the conclusion that this was a poorly configured domain. Some implementations have hard-coded a preference for IPv4 since IPv6 is mostly used over tunnels and add latency today. This should be user-configurable. An owner of a domain can use SRV record weights to indicate a preference to one or the other protocols, which is a better solution. If you use IPv6 over tunnels, make sure that you separate host records for A and AAAA and have a preference towards the A record hosts in your SRV records.

We do need to continue testing all kinds of migration scenarious to  be able to come up with a best current practise document. SIPit26 gave us many good experiences to build from. I hope that testing continues at SIPit27 with the new SIPit IPv6-o-matic(R)(C)(TM) and the prompts from Allison Smith!

SIPit 26 is over and everything was packed together quickly, thanks to help from sponsors and participants. It did surprise me a lot how quickly we could pack all the phones, cables, tables and equipment together. Three days to set everything up, three hours to take it down.


I think it’s been a great SIPit. Unfortunately, I did not have time to test much myself, but I will take the oppurtunity to test at the next SIPit. On the other hand, we’ve run many successful multiparty tests. Successful tests doesn’t mean that everything works as expected. It’s a good thing to locate new bugs in implementations, to find issues with the standard specifications.  That’s exactly why we run the SIPit interoperability tests.


SIPit26 added a lot of focus on IPv6. We integrated IPv6 in standard tests, we added IPv6 self-tests and we run IPv6 multiparty tests. I’ll write more about the results and experiences learned later.


A big thank you to:

  • The SIP Forum and Robert Sparks for organizing SIPits
  • My co-host, TANDBERG.
  • The sponsors: .se, Ingate, Intertex
  • Our partner, the IPv6 Forum
  • SNOM Technologies that provided all the phones
  • My family that helped me set things up. Lisa printed badges and welcome packs, Erik that helped me building the network
  • Lasse Andersson at Whizom who helped me all week, including setting up everything
  • Electrum Conference in Kista, that took care of us in a good way and handled everything very professionally.
  • All the SIPit partipant companies and attendees. Together we make the SIP world better, promoting interoperability between vendors and products.

Being a SIPit host is an experience I would happily repeat. Join the club and offer to host a coming SIPit. Next up is Asia, possibly Australia. After that it’s back to the USA again. Now, it’s time for me to get back to a normal life and get out in my garden.

With SIPit greetings from a sunny Sollentuna!

In a joint press release, the SIP Forum and the IPv6 Forum launches a cooperation in order to raise the pressure on the members and the market to move forward with IPv6 and realtime SIP communication.

“SIP and IPv6 are the two fundamental Internet plumbing pieces of the future Internet. This partnership will allow the SIP Forum and the IPv6 Forum to leverage each organization’s powerful worldwide user base to drive the right knowledge and best practices to the Internet community at large,” said Latif Ladid, President of the IPv6 Forum & Emeritus Trustee Internet Society. “This union will smooth the adoption of these two technologies and spur Internet growth and solid sustainability.” 

“The SIP Forum shares a similar mission and vision as the IPv6 Forum for the broad interoperability and adoption of open standards, next generation Internet-based technologies and services,” said Richard Shockey, SIP Forum Chairman of the Board. “By coming together, our two organizations can help move the industry forward and develop the foundation to fuel a new generation of communications innovation.”

I believe this partnership can lead to a lot of progress. Unified Communication ties people together across boundaries. One of these boundaries will be the IPv4 and the IPv6 Internet. The SIP industry has a responsibility to make sure that this transition works seamlessly and that our customers get products and services that will continue to work as the IPv6-only part of the Internet starts growing – and I’m not only talking about laptops with softphones and chat software – SIP is an application that will run on smartphones, TV sets, pads and all kinds of connected things. A Unified Communication network requires IPv6 to be unified.

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