Friday, August 12, 2011
The snom m9 is actually one of the first SIP devices that I know that support IPv6 and IPv4 at the same time. IPv6 will become very important over the next few years, and to me it looks like most of the VoIP industry is still ignoring this fact to a very large extend. IPv6 does not only make IP addresses a lot cheaper; it does also make NAT obsolete, which is one of the biggest problems in the deployment of VoIP in the Internet. And IPv6 was specified when VoIP was already there, so the engineers had the chance to put some other specifics about real time communications into the protocol that will make our life a lot easier.
I believe right now only a few guys are using the IPv6 feature. At least I know only one! Most of the features were so far tested only in the lab environment. It would be great to get more feedback, because honestly lab testing is good and necessary but often the real life out there looks different.
For example we had a discussion if in the world of IPv6, we would still need a DHCP client. As you know, in IPv6 there are router advertisements going through the network, so that every device can just pick an address and go ahead. Specifically, how would you find the DNS server? The m9 supports the multicast DNS server discovery method, but it was not clear how much that would be done really in the real life. So at the end of the day we decided to put in a DHCPv6 client in, where the DHCP server can explicitly set the DNS server and also other parameters that we know from DHCPv4.
Also, we were discussing how you would find the provisioning server in IPv6. Because there is nothing like an option 66 and we don’t even know if there would be a DHCP server at all, we decided to go another route and use DNS to locate the provisioning server. So we added another stage that tries to resolve “m9.snom.provisioning.local” and fetch the provisioning data from there. This method also works for IPv4, and as long as you are able to control the DNS server that is a beautiful way of controlling where you fetch your configuration from.
Apart from that, I was surprised to see how stuff like SRTP and SIP/TLS was working pretty much the same in IPv6 than in IPv4. It makes me optimistic that once that the transition from Ipv4 to IPv6 is at full speed, the m9 should do the upgrade without even a reboot of the base station. I would love to hear your stories.