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Troubleshooting Call Quality issues


Skype for Business Enterprise Voice is a true PBX replacement, and when deployed properly is capable of five 9’s reliability. However, the nature of any Voice Over IP system is that it requires a properly deployed supporting cast. This supporting cast in a Skype for Business deployment can include Servers, Virtual hosts, Network Cards, Network Cabling, Switches, VoIP Gateways, Telephony Trunks, Wireless infrastructure and more. Due to the large supporting cast of a VoIP solution, voice quality issues can be somewhat overwhelming to start troubleshooting. This article aims to clarify the troubleshooting process for Skype for Business voice (and video) quality issues.

The first step to any troubleshooting process is to try to determine the location of the root cause. First, start by gathering the following information about the users’ issues:

  • Are the voice issues robotic, drops, etc.?

  • Does it happen at specific times of day? How long has this been occurring?

  • Does it happen on Conference calls? Peer-to-peer calls? PSTN Calls?

  • How are you connected to the internet? Wired or wireless? Bandwidth?

  • Are you experiencing any other issues with your computer / device? What type of device are you using?


Once you have gathered this information, you may start to see a pattern which points you to the location of the problem. The “locations” (in order of most likely root cause to least likely) and some possible cues that point to them are listed below:

  • Client-side:

    • Problems only reported by one or very few users

    • Client experiences problems whether in a PSTN call, Skype conference call or in a Skype peer to peer call

    • Client is remote (At home, hotel, coffee shop, etc.), and doesn’t have issues in the office or in other location

    • Client is on WiFi / 4G, and doesn’t experience issues when hard-wired

    • Client’s PC / Mac / Mobile device is underpowered or outdated

    • On a conference call, other attendees do not experience issues


  • Server / VM / Hardware infrastructure:

    • Problem reports are widespread *

    • Issues may worsen during Skype conference calls *

    • Peer-to-Peer calls work fine, while Conference and/or PSTN calls are troublesome *

    • Issues may worsen during peak usage *

    • Issues only occur on users traversing the Edge server (to determine if user is traversing the Edge server, CTRL + Right click on the Skype icon on the task tray. Click on configuration information. Inside User Status: FALSE = Coming in via the Edge TRUE = Inside the network / WAN) *

    • Issues only occurring on PSTN calls routed via specific gateway or gateway card


  • LAN / Bandwidth:

    • Only particular offices experience the issues, while users outside of that location may not

    • Issues worsen during peak bandwidth usage

    • Location is at peak utilization for Network / Circuit

    • PSTN is delivered via shared bandwidth SIP trunk, and issues occur only during PSTN calls (Not via IP-only Conferences or Peer-to-Peer calls)


  • WAN:

    • Only remote offices experience the issue, while users local to the Skype servers do not *

    • Peer-to-Peer calls within the office are fine, while Peer-to-Peer calls to remote offices or conference calls are troublesome

    • Users experiencing problems are on a VPN


  • Telephony Provider (or Office 365-related):

    • Issues ONLY occur during PSTN calls (Dialing to a conference bridge, or a call from a Skype user to a phone number)

    • Problems only occurring on one specific trunk


* Not applicable to Office 365 Skype Online Cloud PBX users.


Now that you have hopefully zeroed in on the “location” of the root cause, you can run through some steps to resolve the issue. Below are some recommended items to check (in order) for the specific locations:


  • Troubleshooting Client-side issues:

    • If on a VPN, disconnect from VPN and test (Administrator may need to configure split-DNS to avoid Skype traffic traversing the VPN)

    • Instruct user to connect to a Hardwired internet connection if possible, and test

    • Ask client to run a bandwidth test from

    • Instruct user to go to Start Run CMD, and type in “Ping -t”, keep it running in the background, and monitor during issues for high ping time / lost packets

      • A fast, steady stream of lings during voice quality issues removes the client’s network / bandwidth from the suspect list

    • Ask client to go to the Skype client Settings Tools Options General, and enable “Full” logging, review logs during failure

    • Ask client to make call from another PC / Mac / Mobile device, and determine if issues still exist

    • Assure that client OS and Skype client are up to latest patch level


  • Troubleshooting Server / VM / Hardware infrastructure:

    • Assure that Skype servers meet minimum requirements *

      • 12 CPUs (cores), 32 GB RAM for Front ends, Back ends (SQL)

      • 8 CPUs (Cores), 16 GB RAM for Mediation, Edge

      • Do not deploy servers with less than the minimum specs, unless instructed to by an Enabling or Microsoft Engineer

      • Healthy PerfMon logs do not indicate that there are enough resources, instead subscribe to minimum requirements

    • Assure that VM infrastructure is deployed properly *

      • RAM and CPU should not be dynamically assigned

      • A hardwire NIC (not Broadcom) should be dedicated to Skype servers if possible

    • Assure that the number of users for a single Skype pool does not exceed the max allowed *

    • Assure that Cable runs for Telephony (PRIs primarily) is not too long, and use shielded cable if possible

    • Assure that Server rooms are properly cooled *

    • Broadcom NICs are not recommended *

    • Review Skype error logs and monitoring server logs *

    • Assure that on-premises Skype for Business servers are up to the latest patch level *


  • Troubleshooting LAN / Bandwidth issues:

    • Deploy QoS on the Skype side, as well as the network infrastructure to prioritize voice and video traffic

    • If using a shared bandwidth SIP trunk (or bring your own bandwidth), consider using a dedicated SIP trunk

    • Monitor internet and MPLS bandwidth, and increase bandwidth if limit is reached

    • Replace any network equipment that is outdated / possible bottleneck (10bt equipment, routers, unmanaged switches)

    • Review Switch logs to determine if any errors are occurring.

    • For office 365, consider using Express Route


  • Troubleshooting WAN issues:

    • Assure that Skype traffic does not traverse a VPN (instead, configure WAN users to traverse the internet)

    • Skype traffic should not run through bandwidth optimizers

    • Review MPLS Bandwidth, and increase if needed


  • Troubleshooting Telephony Provider (or Office 365-related):

    • Open a ticket with the Telephony Provider *

    • Open a ticket with Microsoft support for Office 365 issues


* Not applicable to Office 365 Skype Online Cloud PBX users.


If you have made it through this list, and are not able to determine root cause or resolve the issues, reach out to Enabling Technologies to assist. Enabling Technologies may be reached at or +1-443-625-5199.


Enabling Technologies has created a VOIP Troubleshooting Checklist for our clients.  If you would like a copy of this checklist kindly request here

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