Deploy media bypass in Skype for Business Server

Deploy media bypass in Skype for Business Server Enterprise Voice. Includes prerequisites and deployment process checklist.

This article assumes that you have published and configured either at least one or more Mediation Servers and at least one gateway peer to provide PSTN connectivity. For more information, see Deploy a Mediation Server in Topology Builder in Skype for Business Server and Define a gateway in Topology Builder in Skype for Business Server.

If the peer you connect to is the SBC of a SIP trunking provider, make sure that the provider is a qualified provider and that the provider supports media bypass. For example, many SIP trunking providers allow their SBC to receive traffic from the Mediation Server. If so, then bypass must not be enabled for the trunk in question. Also, you can't enable media bypass unless your organization reveals its internal network IP addresses to the SIP trunking provider.

Note

Media bypass will not interoperate with every PSTN gateway, IP-PBX, and SBC. Microsoft has tested a set of PSTN gateways and SBCs with certified partners and has done some testing with Cisco IP-PBXs. Media bypass is supported only with products and versions listed on Unified Communications Open Interoperability Program - Lync Server.

If you have optionally configured call admission control (CAC), another advanced Enterprise Voice feature, the bandwidth reservation performed by call admission control doesn't apply to any calls for which media bypass is employed. The verification of whether to employ media bypass is performed first, and if media bypass is employed, call admission control isn't used for the call; only if the media bypass check fails is the check performed for call admission control. The two features are thus mutually exclusive for any particular call that is routed to the PSTN. This is the logic because media bypass assumes that bandwidth constraints don't exist between the media endpoints on a call; media bypass can't be performed on links with restricted bandwidth. As a result, one of the following applies to a PSTN call: a) media bypasses the Mediation Server, and call admission control doesn't reserve bandwidth for the call; or b) call admission control applies bandwidth reservation to the call, and media processes the Mediation Server involved in the call.

In addition to enabling media bypass for individual trunk connections associated with a peer, you must also enable media bypass globally. Global media bypass settings can either specify that media bypass is always attempted for calls to the PSTN, or that media bypass is employed by using the mapping of subnets to network sites and network regions—similar to what is done by call admission control, another advanced voice feature. When media bypass and call admission control are both enabled, then the network region, network site, and subnet information that is specified for call admission control is automatically used when determining whether to employ media bypass. This means that you can't specify that media bypass is always attempted for calls to the PSTN when call admission control is enabled.

Note

When you use these steps to configure media bypass, the assumption is that you have good connectivity between clients and the Mediation Server peer (for example, a PSTN gateway, an IP-PBX, or an SBC at a SIP trunking provider). If there are any bandwidth limitations on the link, media bypass cannot be applied to the call. Media bypass will not interoperate with every PSTN gateway, IP-PBX, and SBC. Microsoft has tested a set of PSTN gateways and SBCs with certified partners and has done some testing with Cisco IP-PBXs. Media bypass is supported only with products and versions listed on Unified Communications Open Interoperability Program - Lync Server.

Deployment Process for media bypass

The following table provides an overview of the media bypass deployment process.

Phase	Steps	Roles	Deployment documentation
Configure trunks for media bypass	If you haven't already done so, configure one or more trunks for media bypass.	A member of RTCUniversalServerAdmins group, or a member of the CsVoiceAdministrator, CsServerAdministrator, or CsAdministrator role	Configure a trunk with media bypass in Skype for Business Server
Configure media bypass globally	Configure media bypass for either all calls to the PSTN, or certain calls based on network sites and network regions.	A member of RTCUniversalServerAdmins group, or a member of the CsVoiceAdministrator, CsServerAdministrator, or CsAdministrator role	Configure media bypass in Skype for Business Server to always bypass the Mediation Server Configure media bypass global settings in Skype for Business Server to use site and region information
Associate subnets with network sites, if necessary	If you configure media bypass to use site and region information, you must associate the subnets of your deployment with network sites and regions (If you haven't already done so for another voice feature.)	A member of RTCUniversalServerAdmins group, or a member of the CsVoiceAdministrator, CsServerAdministrator, or CsAdministrator role	Associate a subnet with a network site