Andrew S. Tanenbaum Edition 5th Exercise 6 Question 35 (Page No. 609)

Question

To address the limitations of IP version 4, a major effort had to be undertaken via
IETF that resulted in the design of IP version 6 and there are still is significant reluctance
in the adoption of this new version. However, no such major effort is needed to
address the limitations of TCP. Explain why this is the case.