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Azure Communications Gateway limits, quotas and restrictions

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This article contains the usage limits and quotas that apply to Azure Communications Gateway. If you're looking for the full set of Microsoft Azure service limits, see Azure subscription and service limits, quotas, and constraints.

General restrictions

The following restrictions apply to all Azure Communications Gateways:

  • All traffic must use IPv4.
  • All traffic must use TLS 1.2 or greater. Earlier versions aren't supported.
  • The number of active calls is limited to 15% of the number of Users assigned to the Azure Communications Gateway as defined in Plan and manage costs for Azure Communications Gateway.

SIP message restrictions

Azure Communications Gateway applies restrictions to individual fields in SIP messages. These restrictions are applied for:

  • Performance - Having to process oversize messages elements decreases system performance.
  • Resilience - Some oversize message elements are commonly used in denial of service attacks to consume resources.
  • Security - Some network devices may fail to process messages that exceed this limit.

SIP size limits

Resource Limit
Maximum SIP message size 10 Kilobytes
Maximum length of an SDP message body 128 Kilobytes
Maximum length of request URI 256 Bytes
Maximum length of Contact header URI 256 Bytes
Maximum length of the userinfo part of a URI 256 Bytes
Maximum length of domain name in From header 255 Bytes
Maximum length of a SIP header's name 32 Bytes
Maximum length of a SIP body name 64 Bytes
Maximum length of a Supported, Require or Proxy-Require header 256 Bytes
Maximum length of a SIP option-tag 32 Bytes

SIP behavior restrictions

Some endpoints might add parameters in the following headers to an in-dialog message when those parameters weren't present in the dialog-creating message. In that case, Azure Communications Gateway will strip them, because this behavior isn't permitted by RFC 3261.

  • Request URI
  • To header
  • From header

Next steps

Some default limits and quotas can be increased. To request a change to a limit, raise a change request stating the limit you want to change.