Protocol

Client Errors (E1)

Server Errors (E2)

SIP

4xx Status Codes

5xx, 6xx Status Codes

HTTP

4xx Errors

5xx Errors

Diameter

1001, 3001-3010

4001-4003, 5001-5017

DNS

3: Name Error (Domain name referenced in the query doesn’t exists)
4: Query type not implemented
5: Request refused for policy reasons

All other

SMPP

8: System Error

All other

GTP

N/A

All

Radius

N/A

All