Question
Consider the following statements about the routing protocols, Routing Information Protocol (RIP) and Open Shortest Path First (OSPF) in an IPv4 network.
I: RIP uses distance vector routing
II: RIP packets are sent using UDP
III: OSPF packets are sent using TCP
IV: OSPF operation is based on link-state routing
Which of the statements above are CORRECT?
Official answer and solution
- Official answer
- C
- From
- Official GATE 2017 answer key
Solution
Verify the routing algorithm and transport protocol used by RIP and OSPF in IPv4 networks.
Analyze the four statements:
- Statement I: RIP uses the Bellman-Ford distance vector routing algorithm where hop count is used as the routing metric (maximum 15 hops). This statement is CORRECT.
- Statement II: RIP operates at the application layer and encapsulates its routing update messages directly into UDP datagrams using destination port 520. This statement is CORRECT.
- Statement III: OSPF does not use a transport layer protocol such as TCP or UDP; instead, OSPF packets are encapsulated directly into IP datagrams with IP protocol number 89. Thus, Statement III is INCORRECT.
- Statement IV: OSPF is based on Dijkstra's shortest-path first (SPF) link-state routing algorithm. This statement is CORRECT.
Statements I, II, and IV are correct, which corresponds to option C.
C
Assuming that because BGP uses TCP (port 179), OSPF also uses TCP. OSPF runs directly over IP (protocol 89).
The answer is the one in the official GATE answer key. The solution is this site's own explanation.
Source
- Paper
- GATE 2017 Computer Science and Information Technology (CS) Session 2
- Question
- 9 of 65, printed as CS Q.9
- Section
- Computer Science and Information Technology
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