Service limits for Azure Communication Services

This document explains some of the limitations of Azure Communication Services and what to do if you are running into these limitations.

Throttling patterns and architecture

When you hit service limitations you will generally receive an HTTP status code 429 (Too many requests). In general, the following are best practices for handling throttling:

• Reduce the number of operations per request.
• Reduce the frequency of calls.
• Avoid immediate retries, because all requests accrue against your usage limits.

You can find more general guidance on how to set up your service architecture to handle throttling and limitations in the Azure Architecture documentation for throttling patterns.

Acquiring phone numbers

Before trying to acquire a phone number, make sure your subscription meets the geographic and subscription requirements, otherwise you can't purchase a phone number. The below limitations apply to purchasing numbers through the Phone Numbers SDK and the Azure portal.

Operation	Scope	Timeframe	Limit (number of requests)
Purchase phone number	Azure tenant	-	1
Search for phone numbers	Azure tenant	1 week	5

Action to take

For more information, see the phone number types concept page and the telephony concept overview page.

If you would like to purchase more phone numbers or put in a special order, follow the instructions here. If you would like to port toll-free phone numbers from external accounts to their Azure Communication Services account follow the instructions here.

Identity

Operation	Timeframes (seconds)	Limit (number of requests)
Create identity	30	500
Delete identity	30	500
Issue access token	30	500
Revoke access token	1	100
createUserAndToken	30	1000
exchangeTokens	30	500

Action to take

We always recommend you acquire identities and tokens in advance of starting other transactions like creating chat threads or starting calls, for example, right when your webpage is initially loaded or when the app is starting up.

For more information, see the identity concept overview page.

SMS

When sending or receiving a high volume of messages, you might receive a 429 error. This indicates you are hitting the service limitations and your messages will be queued to be sent once the number of requests is below the threshold.

Rate Limits for SMS:

Operation	Scope	Timeframe (seconds)	Limit (number of requests)	Message units per minute
Send Message	Per Number	60	200	200

Action to take

If you require sending an amount of messages that exceeds the rate-limits, please email us at phone@microsoft.com.

For more information on the SMS SDK and service, see the SMS SDK overview page or the SMS FAQ page.

Chat

Size Limits

Name	Limit
Number of participants in thread	250
Batch of participants - CreateThread	200
Batch of participants - AddParticipant	200
Page size - ListMessages	200

Operation Limits

Operation	Bucketed by	Limit per 10 seconds	Limit per minute
Create chat thread	User	10	-
Delete chat thread	User	10	-
Update chat thread	Chat thread	5	-
Add participants / remove participants	Chat thread	10	30
Get chat thread / List chat threads	User	50	-
Get chat message / List chat messages	User and chat thread	50	-
Get chat message / List chat messages	Chat thread	250	-
Get read receipts	User and chat thread	5	-
Get read receipts	Chat thread	250	-
List chat thread participants	User and chat thread	10	-
List chat thread participants	Chat thread	250	-
Send message / update message / delete message	Chat thread	10	30
Send read receipt	User and chat thread	10	30
Send typing indicator	User and chat thread	5	15
Send typing indicator	Chat thread	10	30

Voice and video calling

Call maximum limitations

Name	Limit
Number of participants	350

Calling SDK streaming support

The Communication Services Calling SDK supports the following streaming configurations:

Limit	Web	Windows/Android/iOS
Maximum # of outgoing local streams that can be sent simultaneously	1 video or 1 screen sharing	1 video + 1 screen sharing
Maximum # of incoming remote streams that can be rendered simultaneously	4 videos + 1 screen sharing	6 videos + 1 screen sharing

While the Calling SDK won't enforce these limits, your users may experience performance degradation if they're exceeded.

Calling SDK timeouts

The following timeouts apply to the Communication Services Calling SDKs:

Action	Timeout in seconds
Reconnect/removal participant	120
Add or remove new modality from a call (Start/stop video or screen sharing)	40
Call Transfer operation timeout	60
1:1 call establishment timeout	85
Group call establishment timeout	85
PSTN call establishment timeout	115
Promote 1:1 call to a group call timeout	115

Action to take

For more information about the voice and video calling SDK and service, see the calling SDK overview page or known issues.

Teams Interoperability and Microsoft Graph

If you are using a Teams interoperability scenario, you will likely end up using some Microsoft Graph APIs to create meetings.

Each service offered through Microsoft Graph has different limitations; service-specific limits are described here in more detail.

Action to take

When you implement error handling, use the HTTP error code 429 to detect throttling. The failed response includes the Retry-After response header. Backing off requests using the Retry-After delay is the fastest way to recover from throttling because Microsoft Graph continues to log resource usage while a client is being throttled.

You can find more information on Microsoft Graph throttling limits in the Microsoft Graph documentation.

Network Traversal

Operation	Timeframes (seconds)	Limit (number of requests)
Issue TURN Credentials	5	30000
Issue Relay Configuration	5	30000

Action to take

We always recommend you acquire tokens in advance of starting other transactions like creating a relay connection.

For more information, see the network traversal concept overview page.

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