title: Should there be authentication/authorization between microservices?
body: <p>I know this may be not a good question.</p>
  
  <p>I was asked a question: do we really need authentication among microservices. And I have no idea the answer. I did read some tutorials on SOA, microservices, and how to add authentication among the services. But I did not have too many ideas <strong>why we need authentication/authorization between microservices? Any use cases where they are required? Any use cases where they are not required?</strong> Any potential risk without authentication/authorization? </p>
  
  <p>Any comments welcomed. It is better to give some practical examples. Thanks</p>