Why is the transport layer not present inside the network?

The transport layer provides additional function to compensate for the limitations and impairments of the network layer, in order to meet requirements (e.g. QoS) of the upper layer. For example in TCP/IP, IP provides only best effort service. To provide the reliable service required by some applications - that is, to compensate for the shortcomings of best effort service - TCP establishes connections and implements flow control and congestion control on an end-to-end basis. Answer Actually, it is, just not through normal tools. Special programming is required to access the upper layers of TCP.