Chapter 1

1.1	Calculate the maximum number of class A, B, and C network IDs.
A:	The value is 2 ⁷ “ 2 (126) plus 2 ¹⁴ - 2 (16,382) plus 2 ²¹ “ 2 (2,097,150) for a total of 2,113,658. We subtract 2 in each calculation since a network ID of all zero bits or all one bits is invalid.
1.2	Fetch the file `nsfnet/statistics/history.netcount` using anonymous FTP (Section 27.3) from the host `nic.merit.edu` . This file contains the number of domestic and foreign networks announced to the NSFNET infrastructure. Plot these values with the year on the x-axis and a logarithmic y-axis with the total number of networks. The maximum value for the y-axis should be the value calculated in the previous exercise. If the data shows a visual trend, extrapolate the values to estimate when the current addressing scheme will run out of network IDs. (Section 3.10 talks about proposals to correct this problem.)
A:	Figure D.1 shows a plot of the values through August 1993. Figure D.1. Number of networks announced to NSFNET. The dashed line estimates that the maximum number of networks will be reached in the year 2000, if the exponential growth continues.
1.3	Obtain a copy of the Host Requirements RFC [Braden 1989a] and look up the robustness principle that applies to every layer of the TCP/IP protocol suite. What is the reference for this principle?
A:	"Be liberal in what you accept, and conservative in what you send."