What are the advantages of a connectionless service?
The connectionless service has at least one advantage. A connectionless service is simple. The source, destination, and the routers need to deal with each packet individually without considering the relationship between them. This means there are no setup and teardown phases. No extra packets are exchanged between the source and the destination for these two phases.
Disadvantage of the connectionless service:
The connectionless service has at least one disadvantage. The packets may arrive out of order; the upper layer that receive them needs to reorder them.