Visa to Ireland

Hi,

I am in the US (NY) and may need to go to Ireland for a business trip.

Does anyone have any experience/knowledge about obtaining visa to Ireland? I checked Ireland embassy website in the US but still have questions. The main questions are:
- Can I apply the visa in person at NY consulate?
- How long does it take to process?
- What is the valid period of a visa?
- Is photograph required? (Believe it or not, it is not listed as required document on the website.

I appreciate helps from anyone who knows such information.

Thanks,