Mediation Service Details Test

The Mediation Server is considered the last point of contact for the Skype for Business environment before communicating to the telephony world for audio communication, whether its ingress or egress VoIP calls to the Public Switched Telephone Network (PSTN) world. The Mediation Server is required for leveraging for inbound calls, outbound calls, and dial-in conferencing in a Skype for Business 2013 environment.

The Mediation Server listens for calls from both the server and the gateway. To listen for calls from the server, it uses Session Initiation Protocol (SIP) listening ports. Typically, port 5070 is used for Transport Layer Security (TLS) traffic coming from the Skype for Business server. To listen for calls from the gateway, it uses port 5067 for IP and PSTN traffic.

The Mediation Server is considered a Back-to-Back User Agent (B2BUA), which is responsible for handling communication between two endpoints in a SIP call. All SIP signaling will traverse through the Front End Server and Mediation Server when in route to a PSTN gateway. Only when media bypass is enabled will calls bypass the Mediation Server, which means that the calls go from the Skype for Business 2013 client straight to the PSTN gateway. When there's a PSTN gateway device local to where the call is being made, organizations will typically enable the Skype for Business environment for media bypass to avoid having the media traverse the WAN to make a call. This improves call quality because it reduces the chance for latency, jitter, and packet loss, which naturally occurs when a VoIP call travels through multiple hop points before the call reaches the endpoint receiving the call.

Some of the Mediation Server's key functions include:

  • Encrypting and decrypting Secure Real-Time Transport Protocol (SRTP) data on the Skype for Business server side
  • Translating SIP over TCP to SIP over mutual TLS (MTLS)
  • Translating media streams between the Skype for Business server and the gateway peer of the Mediation Server

Using the Mediation Server Details test, it is possible to figure out how many audio channels are enabled with Phase Shift Modulation quality reporting and how many calls actually failed due to heavy load as well as due to the unexpected interaction from the proxy.

Target of the test : A Microsoft Skype for Business server

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for the target Microsoft Skype for Business server that is to be monitored.

Configurable parameters for the test
Parameters Description

Test Period

How often should the test be executed.

Host

The host for which the test is to be configured.

Port

The port at which the specified host listens. The default port is 5060.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

PSM quality enabled audio channels

Indicates the number of audio channels that are currently enabled with Phase Shift Modulation (PSM) quality reporting.

Number

A low value is desired for this measure. Calculating PSM may cause processing overhead which in turn may directly affect the performance of the server. Therefore, administrators need to keep a check on the number of audio channels for which PSM reporting is enabled.

Calls that failed due to unexpected interaction from the Proxy

Indicates the number of calls that failed due to the unexpected interaction from proxy on the mediation server during the last measurement period.

Number

Ideally, the value of this measure should be zero.

Media connectivity check failures

Indicates the number of calls that failed when the media connectivity between the Mediation server and the remote endpoints could not be established.

Number

Ideally, the value of this measure should be zero.

Missing candidates

Indicates the number of times the media stack does not have media relay components.

Number

 

Call failures due to heavy load

Indicates the scaled index between zero and 100 that is related to all call failures due to Global Health Index as a heavy load.

Number