GATE CSE 2003 | Question: 27

Question

Which of the following assertions is FALSE about the Internet Protocol (IP)?

• A. It is possible for a computer to have multiple IP addresses
• B. IP packets from the same source to the same destination can take different routes in the network
• C. IP ensures that a packet is discarded if it is unable to reach its destination within a given number of hops
• D. The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way

Comments

it should be of 2 marks.

---

How computer can have multiple ips???

I studied that computer is assigned a unique ip address

---

@mahendrapatel a computer can have multiple IP addresses . 

Suppose the computer is at a network , 
If the same computer is moved to another network then it will be assigned a different IP address . 

---

but having multiple ips at a time isn't possible, right?

Answer 1

In computer networking, source routing, also called path addressing, allows a sender of a packet to partially or completely specify the route of the packet takes through the network. In contrast, in non-source routing protocols, routers in the network determine the path based on the packet's destination.

http://en.wikipedia.org/wiki/Source_routing

Answer is D.

Comments

Different NICs can lead to different mac addresses as well?

---

Yes

---

@Roh yes NIC is the hardware component containing your MAC address

Answer 2

Option-D

1. The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way
2. Bcz in strict source routing or lose source routing path is set by the source not by router and main task of router is to check outgoing path with the help of forwording table inside it.

Comments

Source decides entire route for a packet that is Strict source routing ... Then how is routing table helping it ??

---

source decided routes for packet that is actually SSR

Answer 3

The correct answer is Option D.

Let’s go option wise

Option A). Yes it is possible for the  computer to have multiple addresses, assumed that the computer using DHCP protocol so new IP addresses each time when its connected to network.

hence option A is True.

Option B). IP packets can take different path from same  source to same destination, as IP is connection less based protocol packet have authority to take different path to reach the destination.

hence option B is also True.

Option C).In IP header there is a field known as Time to Live field, this field is limit for packet which says that number of intermediate router can packets traverse, it’s value is decremented by 1 when it passes one intermediate router, and when this field reaches 0 then the packet has been discarded by the router.

But when this field becomes 0 when packets receiving at destination then it will not get discarded, it has been accepted by the destination.

hence IP ensures a packet is discarded if it is not reaching the destination within a given number of hops(Intermediate Router).

hence option C is also True.

Option D).

In IP header’s option field, there is an option known as Strict Source Routing(SSR) it tells the packet to follow the route that has mentioned in this field, means packet has to traverse those router which is mentioned in it , if packet reaches the destination and it has not been traversed all the router as mentioned in SSR field then that packet get discarded even it reaches the correct destination, and this field is set by Source only.

So , it is incorrect that packet source cannot route the packet.

hence option D is False.

Answer 4

• A. It is possible for a computer to have multiple IP addresses. True: A computer with multiple network interface cards, can have more than one IP.
• B. IP packets from the same source to the same destination can take different routes in the network. True: this is the characteristics of packet switching.
• C. IP ensures that a packet is discarded if it is unable to reach its destination within a given number of hops. True: If TTL expires packet will be discarded.
• D. The packet source cannot set the route of an outgoing packets; the route is determined only by the routing tables in the routers on the way. False: Using source routing a sender can specify the route of an outgoing packets.