Guidelines for grading PS3:

Problem 1. 

-- 1 point for attempting

-- 2 points for getting correct number of fragments at destination

-- 1 point for making sure that IP headers are taken into account in
each fragment

-- 1 point for making sure that data in each fragment is a multiple of
8

-- 0.5 point for each correct offset (there are 7 fragments, do not
give any points for correctness of fragment with offset 0 -- so this
comes to 3 points in all)

Problem 2.

-- Note that there is no one correct answer

-- 6 points for part (a)

-- 2 points for part (b)

Part (a):

-- 1 point for attempting

-- 1 point for ensuring that all address start with 200.10.10

-- 2 points for making sure that the number of address assigned to
each network, as indicated by the subnet number and subnet mask is
indeed the appropriate number

-- 2 points for ensuring that any two distinct subnet numbers remain
distinct when the longer one is truncated to the length of the shorter
one (you may give partial credit here)

Part (b):

-- 1 point for a reasonable attempt

-- 1 point for a plausibly correct answer

Problem 3.

-- 1 point for attempting

-- 2 points if the tables have the correct format

-- deduct 0.5 points (up to a maximum of 5 points) for an incorrect
or missing table entry

Problem 4.

(a) 1 point for attempting.  3 points for saying that NAT does not
have any entries corresponding to WAN side connection initiation.
Appropriate partial credit (2-3 points) otherwise.

(b) 1 point for attempting.  3 points for saying that Bernard knows
Arnold's IP address and hence can initiate a connection.  Appropriate
partial credit (2-3 points) otherwise.

Problem 5.

-- 3 points for a reasonable attempt

-- deduct a 1/4 point (up to a max of 6) for each incorrect entry

-- round score up the nearest half-point

Problem 6.

-- 3 points for a reasonable attempt.

-- deduct a 1/4 point (up to a max of 6) for each incorrect entry

-- round score up the nearest half-point