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Consider the following statements about the routing protocols. Routing Information Protocol (RIP) and Open Shortest Path First (OSPF) in an $\textsf{IPv4}$ network.

1. RIP uses distance vector routing
2. RIP packets are sent using UDP
3. OSPF packets are sent using TCP
4. OSPF operation is based on link-state routing

Which of the above statements are CORRECT?

1. I and IV only
2. I, II and III only
3. I, II and IV only
4. II, III and IV only

### 1 comment

The above is taken from kurose & Ross.

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Statement $1$ is CORRECT because RIP is one of the Oldest DVR(Distance Vector Routing) Protocols which employ the hop count as a routing metric.

Statement $2$ is CORRECT because RIP uses the UDP as its transport protocol with port no $520.$

Statement $3$ is INCORRECT because OSPF doesnot use a transport protocol such as UDP or TCP but encapsulates its data directly into IP Packets.

Statement $4$ is CORRECT because OSPF is a routing protocol which uses Link State Routing(LSR) and works within a single Autonomous System.

PS:

OSPF needs to perform reliable multicasting because it needs to talk to multiple possible neighbors on the same network segment. Now, TCP does not support multicast and UDP is not reliable Therefore, OSPF implements its own transport mechanism that allows both for reliability (acknowledgements and retransmissions of lost segments) and multicasting, bypassing both TCP and UDP.

Hence, Option C is CORRECT.

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4 4 9

u are right!!! need explanation for this...

why it is like RIP doesn't need reliability but OSPF needs ??

• Open Shortest Path First (OSPF) is a unicast routing protocol developed by a working group of the Internet Engineering Task Force (IETF).

great explanation sir!🙌
we all know RIP->Distance vector

so 1 and 4 sure correct .

now agian RIP is used in UDP as in UDP 520 port

so 2 is also correct

so  1,2,4 correct

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i)RIP uses distance vector routing, hence this is correct option .

ii)RIP is implemented as a process that uses the services of UDP on the well port number 520.so this is also correct.

iii)OSPF is implemented as a program in network layer,using service of the IP for propagation.but in option it is given TCP.hence wrong.

iv)OSPF is based on Link State Routing protocol.hence correct.

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### 1 comment

.this is what u meant OSPF runs directly on top of IP; it does not use TCP or User Datagram Protocol (UDP). OSPF performs its own error correction by means of checksums in its packet header and LSA
1. RIP uses distance vector routing (True)
2. RIP packets are sent using UDP(True)
3. OSPF packets are sent using TCP(False because it doesn't require TCP or UDP it directly added in IP Datagram)
4. OSPF operation is based on link-state routing(True).
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