Last updated on December 27, 2018
I cannot make sense of sending packets of reliable service (TCP) on a lower unreliable service (IP) which in turn sends packets on a layer which provides reliability (Link Layer). Why can't we do away with reliability at link layer as IP is unreliable?
I am taking about the 5 layer model. It is well documented that TCP is a reliable service and IP is best-effort delivery and hence unreliable (ref <a href="http://www.ietf.org/rfc/rfc792.txt" rel="nofollow">RFC 792 - TCP</a>). Also, the data link layer is 'reliable' because of its ARQ mechanism guaranteeing sequential delivery of packets (<a href="http://web.cs.wpi.edu/~cs4514/b98/week3-dll/week3-dll.html" rel="nofollow">ref</a>).