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The intermediate routers between source and destination do not need the following info in the IP header;


b)Identification number

c)Source IP

d)IP version

e)None of these
asked in Computer Networks by Active (1.9k points)
edited by | 92 views

@Sambhrant Maurya

What is the answer the given?

i am thinking it is Option A?

But i didn't have to explanation it, can you Post the answer?

The answer given is none of these.

1 Answer

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Yes, Protocol, Identification number, Source IP and Version, all are required by the intermediate routers. 

Identification number is required due to fragmentation done my the intermediate routers. In case of MTU size is less than the size of the packet, so here identification number is required in fragments. 

Protocol, Source IP and version are also necessary to process and send the packets correctly.

answered by Active (1.6k points)
why Protocol required?
The value of Protocol field indicates the transport-layer protocol at the destination to which the data portion of this IP datagram will be passed i.e. TCP or UDP
yes, why intermediate router need it?

for setting the value, if fragmentation occurs?
router having it's own buffer and assume that buffer is entirely full ,

and now  for a incoming packet, which doesn't have any space in the buffer to kep this IP datagram

therefore it has to be discarded that's congestion , because of congestion the packet is going to be discarded but before discarding it it's better if this router is going to see what type of packet is present inside this Ip datagram ,

if inside the IP datagram , I have a TCP packet , TCP is reliable protocol , then don't discarded it , then inside the buffer see the packets which is not belonging to TCP (i:e UDP , ICMP , IGMP) , then router discarded one of them and place TCP packet inside it


What you want to convey from above matter?


see the packets which is not belonging to TCP

What happens if none of the packets are found? it discard the that IP packet and sent ICMP packet.

Because incase of heavy traffic or congestion packets are discarded based on the protocol
In Kurose & Ross it's written, "TCP runs only in the end systems and not in the intermediate network elements(routers). In fact intermediate routers are completely oblivious to TCP connections; they see datagrams, not connections." . Does it not mean routers are not aware of the protocol used?

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