Skype for Business 2016 client only supports new v19 ICE

Skype for Business client was released on September 2015, and featured a number of new functionalities, as well as some discarded ones, as described here. The one I'd like to talk about is quite under-the-hood, but potentially important.

What you will not find in the article above (but you would have probably hoped for), is that the new client got support for the legacy (v6) ICE removed.
ICE (Interactive Connectivity Establishment) is, in simple terms, a set of protocols (STUN and TURN) used to facilitate media connectivity establishment for endpoints under various restricted network scenarios (e.g. when not directly routable, behind a NAT or firewall). If you'd like to know more, please refer to this excellent resource.

ICE has gone though several iterations. Until OCS 2007 "R1", only ICE v6 was used. OCS 2007 R2 introduced the new and more efficient ICE v19 version, but v6 was maintained for backward compatibility until the SfB 2015 client.

The implications of such change lie with intercommunicating with legacy systems because OCS 2007 "R1" and Exchange 2007 UM only understand ICE v6; so, expect issues if you need to interoperate with these systems. Examples:

- Skype for Business 2016 client calls to Exchange 2007 UM

- Skype for Business 2016 client calls Communicator 2007 "R1" client.

In case you are wondering, I haven't discovered anything new so I am just broadcasting. Credit goes to this blog and to Mastering Skype for Business 2015 book by Keith Hanna. Both are great reads to know more about the issue. Only, despite the potential implications, this doesn't seem to have been in the headlines (or perhaps I just missed it)?

A trace analysis from a Skype for Business 2015 server with the latest July 2016 cumulative update reveals both v6 and v19 ICE are presented in the call negotiations (some servers are also ICE clients).