Question

Leaders from several states of a nation meet once a year to settle common issues. They govern their own states independently, but they work together on issues that affect them all like trade and defense. They do not have a central government that handles these matters or collects taxes. Rather, each member state agrees to this yearly meeting and to follow agreements made there. Yet nothing forces them to keep these agreements other than an interest in maintaining friendly ties with the other members. What type of government arrangement does this nation have?

Confederation
Parliamentary
Federation
Unitary