# istio_protocol-detection-timeout.yaml
apiVersion: release-notes/v2
kind: feature
area: networking
issue:
- 24379
releaseNotes:
- |
  **Removed** the protocol detection timeout by default, reducing traffic failures during slow connections.
upgradeNotes:
- title: Protocol Detection Timeout Changes
  content: |
    In order to support permissive mTLS traffic as well as [automatic protocol detection](istio.io/latest/docs/ops/configuration/traffic-management/protocol-selection/#automatic-protocol-selection),
    the proxy will sniff the first few bytes of traffic to determine the protocol used. For certain "server first" protocols, such
    as the protocol used by `MySQL`, there will be no initial bytes to sniff. To mitigate this issue in the past, Istio introduced
    a detection timeout. However, we found this caused frequent telemetry and traffic failures during slow connections, while increasing latency
    for misconfigured server first protocols rather than failing fast.

    This timeout has been disabled by default. This has the following impacts:

    - Non "server first" protocols will no longer have a risk of telemetry or traffic failures during slow connections
    - Properly configured "server first" protocols will no longer have an extra 5s latency on each connection
    - Improperly configured "server first" protocols will experience connection timeouts. Please ensure you follow the steps listed in [Server First Protocols](https://preliminary.istio.io/latest/docs/ops/configuration/traffic-management/protocol-selection/#server-first-protocols)
      to ensure you do not run into traffic issues.