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Tom Arbuthnot MCSM Communications

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Skype for Business Online Quality of Service DSCP Markings and Port Ranges

Published 15/12/2015 - 7 Comments



With Office 365 Skype for Business Online and Azure ExpressRoute you can have true end to end QoS from your endpoint on the corp network to the cloud. Here are the marking Microsoft use for Skype for Business Online.


Can customers choose or change these DSCP markings or define port ranges?

No, these are globally set on Office 365, so they can’t be changed on a per customer or tenant level. If you have hybrid with SfB Server and want to keep your QoS uniform you could use the same recommendations

SfBO Client Port Ranges (can be marked for QoS just for internal SfB Calls even if not using ExpressRoute):

Port Protocol Direction Usage
50000-50019 RTP/UDP Outbound Audio
50020-50039 RTP/UDP Outbound Video
50040-50059 TCP Outbound Application sharing and file transfer

Client and server (Destination)

Purpose Source IP Destination IP Source Port Destination Port
Session Initiation Protocol (SIP) Signaling Client Office 365 Ephemeral ports TCP 443 TCP
Persistent Shared Object Model (PSOM) Web Conferencing Client Office 365 Ephemeral ports TCP 443 TCP
HTTPS downloads Client Office 365 Ephemeral ports TCP 443 TCP
Audio Client Office 365 50000 – 50019 UDP and TCP 443 TCP, 3478 UDP, 50000 – 59999 UDP and TCP
Video Client Office 365 50020 – 50039 UDP and TCP 443 TCP, 3478 UDP, 50000 – 59999 UDP and TCP
Desktop Sharing Client Office 365 50040 – 50059 UDP and TCP 443 TCP, 50000 – 59999 TCP


ExpressRoute for Office 365 and other Network Connection Options

Azure ExpressRoute for Office 365

You can’t connect to Skype for Business Online

Lync Online Media Port Changes Offer Better Bandwidth Management

Tom Arbuthnot

Tom Arbuthnot

Principal Solutions Architect at Modality Systems
Tom Arbuthnot is Principal Solutions Architect at Unified Communications specialist Modality Systems. He is a Microsoft Certified Master and MVP, blogger, regular on The UC Architects Podcast, and speaker at events including Microsoft TechEd and Ignite. He co-runs The Microsoft UC User Group London.


Dewalt Kotze - 30/05/2017 Reply

How would you apply QoS for a SfB Online environment where GPO is not available on the client side? By default the client uses 1024 – 65k ports so I am wondering how would you be able to make sure the correct dscp marking is applied for voice and video traffic? Or would you set dscp marking on the network layer for traffic coming from the SfB Online side based on the standard SfB port ranges?

Simon Nurse - 07/11/2017 Reply

Hi Tom,

Thanks for the article – we use 0365 and S4B (not Express Route) and when I take Wireshark captures of S4B voice and video calls EVERYTHING is being marked at CS0.

I know I can setup Class-Maps on my Cisco LAN to capture the traffic based on the ports being used for the individual services. I had hoped to get the application to do the DSCP markings however, how is this enabled? via GPO ?? The only articles I can find on this online seem to be referring to S4B Server (which I understand to be “on-prem”) and we use 0365???

Any help would be much appreciated! many thanks!!


    Tom Arbuthnot - 07/11/2017 Reply


    With SfB Online, you can set the client marking via GPO, but you can’t change the marking coming from the “server”/Service. However, if you don’t have express route that should be stripped when hitting the internet(?)

Usman Patel - 21/11/2017 Reply


I am not familiar with SfB. I am a cisco admin.

Cust complains of poor quality audio for conference calls only which are terminated on a SfB server on the internet. Any ideas how o can identify the conf call traffic?

Port ranges ?
SfB Server IP or URL ?

Usman Patel

ARRA - 19/12/2017 Reply

If I would like to DSCP mark INBOUND audio/video traffic FROM Skype Online so that traffic is prioritized to my Skype for Business Online Clients. Per this statement:

“For traffic from server to clients on your network, traffic prioritization, if desired, should be applied at the ingress point based on destination port”

What is the Destination Ports for Audio/Video traffic for Skype Online clients? Is it the same as the Source Ports for Outbound Audio/Video Skype Client traffic, which is 50000-50019 Audio and 50020-50039 Video

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