Mahayana is not a sect at all; it is a vehicle.
Major sectstraditions in Buddhism are usually country or region related. We can distinguish three major branches of Buddhism in the World by what they keep as canon.
- Tibetan, Mongolian, and Russian Buddhism share Tibetan canon.
- Chinese, Japanese, and Korean Buddhism share Chinese canon.
- Sri Lanka, Burma, Thailand, etc share Pali canon.
Some countries mix several aforementioned branches.