SIP 100 Trying vs 420 Bad Extension
SIP 100 (Trying) is a 1xx Provisional response, while 420 (Bad Extension) is a 4xx Client Failure response. 100 indicates that the request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses. In contrast, 420 means that the server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
Descrição
The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
Quando você o vê
Immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
Como corrigir
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Descrição
The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
Quando você o vê
When the request includes a Require header with SIP extensions that the server does not support.
Como corrigir
Check the Unsupported header in the response. Remove the unsupported extension from the Require header or make it optional via Supported.
Diferenças principais
100 is a 1xx Provisional response, while 420 is a 4xx Client Failure response.
SIP 100: The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
SIP 420: The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
You encounter 100 when immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
You encounter 420 when when the request includes a Require header with SIP extensions that the server does not support.
Quando usar qual
For 100 (Trying): No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration. For 420 (Bad Extension): Check the Unsupported header in the response. Remove the unsupported extension from the Require header or make it optional via Supported.