Media Bypass is a huge investment and improvement in CS “14” (Communications Server “14” – next release of OCS).  So what is Media Bypass, what does it get me, and how does it work?

What is it?

  • Media Bypass allows for Communicator clients to communicate directly with a qualified PSTN voice gateway or qualified IP-PBX without traversing the Mediation server for media transcoding
  • When clients use Media Bypass, the Communicator client uses the G.711 codec over SRTP

What are the benefits?

  • Greatly simplifies topology
    • Allows for Mediation server to collocate with Front End server or SBA because of low CPU intensity
    • Greatly reduces the amount of servers needed in deployment resulting in lower TCO
  • Optimizes media flow and quality
    • Eliminates unnecessary hops and potential points of failure
    • Saves WAN bandwidth
    • Improves voice quality with use of G.711 codec


Below are just a few scenarios that show the resulting behavior when Media Bypass is used.  The diagrams show the Mediation server as a separate server for clarity only, usually the Mediation server will be collocated on the Front End server.

PSTN call in main office through local gateway

PSTN Main Gateway large

PSTN call in branch office through branch gateway/SBA

PSTN Branch Gateway

PSTN call in branch office through branch IP-PBX (same scenario for IP-PBX in main office)


Communicator call to PBX phone through IP-PBX

Main PBX Call

Media Bypass in CS “14” is the key to better voice quality and lower TCO for multi-site deployments of Enterprise Voice.  In future posts I will go deeper into the other new voice features of CS “14”.