What if I don't set timeout when using ajax? Is there a default set?

What if I don't set timeout when using ajax? Is there a default set?

What if I don't set timeout when using ajax? Is there a default set? What's the longest timeout set? Is there a endless ajax request?
$.ajax({
type:"post",
url:"",
data:{},
success:function(html){
}
});
this request will last longer than 30 minutes and I found when the task is over ,it didn't execute the success function? Will it auto shut down when the request lasting too long ?