A question often asked by my education customers. Recently, a well respected and unbiased 3rd party network consultancy company called Miercom conducted a series of tests to validate if Lync Server 2010 could sustain 3 days of a million calls without incident to see if it were on par with other enterprise IP PBX systems. 

After 3 days without Lync showing a hiccup Miercom engineers decided to hammer it for another 10 days to see what they could find. Here are the results of their testing:


The 4.1 million calls completed by Lync Server 2010 without a single dropped call was the highest success rate of any PBX or UC system tested by Miercom to date including several Avaya and Cisco IP PBX systems:

“The delivery rate with sustained operation is the highest capacity test applied to any Unified Communications /IP PBX product we have tested to date” – Miercom analysis

Another amazing fact as a byproduct of the test was:

13,167 calls per hour against a single virtualized Lync Server 2010 Standard Edition server running all the Lync roles (mediation, front end, etc). Total hardware used for 5 VMs including a domain controller, SharePoint 2010 server, Exchange 2010 server, QMS server, and a Lync server was a single Hyper-V host which had 16GB of RAM and an 8 way i7 system.

This 3rd party analysis of the reliability and scalability certainly demonstrates Lync Server can scale to handle large call volumes without a single error using only a single server in a virtualized role! From what I have seen with other UC / IP PBX systems, I would challenge other PBX vendoers to provide this level of call scale/volume or reliability with a single virtualized server/appliance.

Their bottom line analysis of Lync Server 2010 from Miercom:

“Microsoft Lync 2010 is a resilient, scalable, feature rich Unified Communications System.
Microsoft Lync 2010 should be in the short list of top three to consider for enterprises
communications infrastructure upgrades
. Quality third party peripherals from Aastra, Polycom and
SNOM will help Microsoft achieve more market acceptance at the Enterprise Desktop. Third party
hardware such as the survivable branch appliance UX 2000 from NET will enable branch offices
the resiliency needed for enterprise communications.” - Miercom analysis

Download the full Miercom analysis and tests conducted against Lync Server 2010 here.

Who is Miercom? Read more about them here.