When does Microsoft Teams use TCP?

Question

When does Microsoft Teams use TCP?
Is it after it detects some ports blocked ?

Answer 1

Hi @Historical_Swimming ,

I tried searching a lot but it seems that currently there's no official document available explicitly stating this. Below are some potentially relevant information I found during my research for reference:

• For Teams to function correctly, you must open TCP ports 80 and 443 from the clients to the internet, and UDP ports 3478 through 3481 from the clients to the internet. The TCP ports are used to connect to web-based content such as SharePoint Online, Exchange Online, and the Teams Chat services. Plug-ins and connectors also connect over these TCP ports. The four UDP ports are used for media such as audio and video, to ensure they flow correctly. (Evaluate my environment)
• For all Microsoft 365 and Office 365 workloads, the recommended connection method to Teams services is bypassing the forward proxy where possible. When a proxy server sits between a client and the Office 365 data centers, media might be forced over TCP instead of UDP, which would impact media quality. (Microsoft 365 and Office 365 URLs and IP address ranges)

Besides, below is an additional article about this topic and hopefully you can find it be of some help:
UDP vs TCP, what is best for Microsoft Teams Voice?
(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Hi HistoricalSwimming

I all my Teams voice projects Teams use TCP if the media could not use UDP blocked by Firewall or not correct configuration on proxy to bypass.
TCP will be used as fallback if UDP fails.

Answer 3

TCP are used on process to process communication using the port number. It then transmits the data as a stream of bytes from source to destination.
It groups the data from one an application to packets called segments then add a header that contains the destination address .