What is the mechanism for GitLab connecting Jira?

Hi, Recently, our laboratory want to connect Gitlab with Jira. We have installed Gitlab CE and Jira6.0.1.

We have connected Jira successfully. But when I tried to create issue on Gitlab, it just redirected to Jira simply. I think the reason is that our Gitlab is CE version. We should install GitLab EE.

I have read some documents about Gitlab integrating Jira. It said we can do the following things:(http://doc.gitlab.com/ee/integration/jira.html#configuration)
(1)Referencing Jira Issues from GitLab
(2)Closing Jira Issues from GitLab

If we installed GitLab EE, we can do the two listing things above, right? But I did not know the mechanism, So I have two questiongs:
(1) Does Gitlab invoke Jira APIs to get and post data?
(2) I know Gitlab provide APIs, If I create an issue through invoking GitLab API, I am sure that there will be a new issue in GitLab. Will be a new issue in Jira too?

Invoking GitLab API to create an issue —> A new issue in GitLab --??–> A new issue in Jira?

Thanks!! :slight_smile: