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(a) Explain the purpose of the following
fields within the IP Header Format. [4]
(i) Fragmentation flags
(ii) Time to live
(iii) Service type
(iv) Identification
Fragmentation flags: used to assemble the
packets (1 mark)
Time to live: used to prevent packet from circulating around the network
forever (1 mark)
Service type: used to specify the service required by the application,
could be combination of reliability and speed (1 mark)
Identification: used when the packets are divided further (1 mark)
(b) In terms of network service, explain
what type of service the Internet Protocol provides. [2]
- Connectionless service: no notation of
a connection between hosts (1
mark)
- Unreliable service: no guarantee that a packet will be delivered
(1 mark)
(c) Identify and explain the two basic
types of routing provided by the Internet
Protocol, with an suitable example for each. [6]
- Direct routing (1 mark): if the destination
address for the packet is on
the same network, the router uses direct routing (1 mark), example
MAC protocol (1 mark)
- Indirect routing (1 mark): if the destination address for the packet
is
on the different network, the router uses indirect routing (1 mark),
example shortest path routing (1 mark)
Explanations should be full in order to receive full marks. Give credit
for valid alternative answers.
(d) Following are the examples of IP
addresses. Identify to which IP address class they belong to. Explain
your answer. [3]
1. 160.50.50.50
2. 64.25.25.25
3. 208.75.75.75
1. 160.50.50.50
2. 64.25.25.25
3. 208.75.75.75
1. Class B, decimal 160 in binary is 1010
0000, Class B address starts
with binary 10 (1 mark)
2. Class A, decimal 64 in binary is 0100 0000, Class A address starts
with binary 0 (1 mark)
3. Class C, decimal 208 in binary is 1101 0000, Class C address starts
with binary 110 (1 mark)
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