title: “asm/WARN/2025_002” linkTitle: “WARN/2025_002” weight: 1 type: docs description: > ASM: Upstream connection established successfully with no protocol errors

Product: Anthos Service Mesh
Rule class: WARN - Something that is very likely to be wrong

Description

The error “upstream connect error or disconnect/reset before headers. reset reason: protocol error” typically indicates a invalid headers during the connection establishment between Envoy and the upstream service. This could occur when Envoy receives headers that are not properly formatted contain duplicates, or conflict with each other (e.g., multiple Transfer-Encoding headers) leading to a protocol error.

Remediation

To remediate the “upstream connect error or disconnect/reset before headers reset reason: protocol error”: Ensure the upstream service is not sending duplicate or conflicting headers, such as multiple Transfer-Encoding headers Validate the headers are properly formatted and comply with HTTP standards You can also perform a PCAP capture on the application pod to check the response headers being sent by application.