Kindly attach articles to know about peer to peer call flow and external call flow diagram articles for lync 2010 and lync 2013

Not sure if there's anything that only has specifically that - but you can take a look at these to see if that helps: http://www.microsoft.com/en-us/download/details.aspx?id=6797

Hi,

For Lync Server 2013 Workflow, you can refer to the following link:

http://www.microsoft.com/en-us/download/details.aspx?id=39968

Best Regards,

Eason Huang

George, kindly share me more information about call establishment. In detail information about Address discovery, address exchange, connectivity checks, candidate promotion, and medial flow