Media Bypass is a new feature in Lync 2010 enabling media to flow directly between clients and PSTN gateways. The basic concept is that the client and the Mediation Server exchanges BypassId’s and if the Id’s match each other media bypass is possible, but not guaranteed (as I’ll discuss later). The BypassId’s are assigned either globally, in which case all servers and clients use the same Id, or per network site, in which case the Id is assigned per subnet membership of the servers and clients. You can control if media bypass is used per PSTN Gateway using Set-CsTrunkConfiguration –EnableBypass.
As I wrote above it is the Mediation Server responsible for the PSTN gateway, which will decide if media bypass can be established. It happens during the signaling in the call setup phase. The PSTN gateway is not necessarily involved.
I’ve set it up in my lab and wanted to share some learning's:
<provisionGroup name="mediaConfiguration" > <propertyEntryList > <property name="bypassEnabled" >true</property> <property name="internalBypassMode" >Any</property> <property name="externalBypassMode" >Off</property> <property name="bypassId" >c61755ed-402f-4b3b-86e2-2bd96252a23c</property> </propertyEntryList> </provisionGroup>
Thanks for the great summary Jens. In your research, have you found whether it's possible to enable media bypass on a conference endpoint? My understanding was that once an MCU is involved, media bypass will not work-is this correct?
Jens>Thanks & Yes :-)
I have a question about media bypass for connections to 3rd Party IP PBXs
"When a user makes a call to the PSTN, the Mediation Server compares the bypass ID of the client subnet with the bypass ID of the gateway subnet. If the two bypass IDs match, media bypass is used for the call. If the bypass IDs do not match, media for the call must flow through the Mediation Server."
My question is: Is the GW subnet defined by the IP address of the signaling peer or the "alternate media IP address" or can either of these addresses be used to find a subnet match to invoke media by pass ?
Jens>Hi Tony, It will always use the alternate media IP address, if it is set.
What is externalBypassMode for and can I utilise (in the lab) already? Is this for Media Bypass via Edge? ;-)
Jens>It's reserved for future use - http://technet.microsoft.com/en-us/library/gg425718(v=ocs.15).aspx
Thanks for the answer! Yes, I have read that already. In essence I am trying to figure out what scenario this is meant to support. Maybe to reach SIPTrunk-Provider directly via Media Bypass when connected via Edge :-)? In larger environments, I could envision oneself being the "provider" with PSTN-Gateways.
BTW: Slightly disappointed about the Office365 Lync Hybrid news :-(