CS217A : Homework 2

CS217A : Homework 2 Problem 1

Problem 1

(1 Point) What are the three private IPv4 address blocks allocated for NAT purpose?

Hint: see RFC 1918.

Problem 2

(1 Point) Suppose a TCP packet passes through a NAT box, and the source IP address is changed from

10.0.0.1 to 1.2.3.4 (but the port number is unchanged). What are the additional fields that need to be

modified by the NAT box in the TCP and IP headers?

Problem 3

(1 Point) What unit is IPv6 Hop Limit field measured in (choose ONE answer)?

a. Seconds

b. Minutes

c. Hop-count

Why is it different from the definition of the TTL field in IPv4?

Problem 4

(1 Point) In IPv6, fragments with a length that is not a multiple of 8 but that also have the M bit set must

be discarded. Why is that?

Problem 5

(1 Point) Why does IPv6 header not have an “Internet Header Length (IHL)” field as in IPv4?

Problem 6

(1 Point) In SCTP (RFC 4960), what is the difference between an “idle” connection and an “inactive”

connection?

Problem 7

(1 Point) How many messages are needed to start-up an SCTP connection? List them in the order as they

appear in a real handshake process.

Problem 8

(1 Point) How does SCTP protect itself against synchronization attacks (similar to SYN flooding attacks

in TCP)?

Problem 9

(1 Point) In SCTP, associations may include multiple IP addresses. How is SCTP supposed to handle

fragmentation if the addresses have different PMTUs?

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CS217A : Homework 2 Problem 10

Problem 10

(1 Point) SCTP Chunk format contains a field “Type”, e.g. DATA chunk has Type = 0. Could you explain

why TCP does not have such a type field in the header to indicate what is carried in the TCP segment?

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