Computer-Networks
October 9, 2023NTA-UGC-NET 2021 Dec & 2022 June Paper-2
October 9, 2023Computer-Networks
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Question 37
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Consider three IP networks A, B and C. Host HA in network A sends messages each containing 180 bytes of application data to a host HC in network C. The TCP layer prefixes a 20 byte header to the message. This passes through an intermediate network B. The maximum packet size, including 20 byte IP header, in each network is:
A : 1000 bytes
B : 100 bytes
C : 1000 bytes
The network A and B are connected through a 1 Mbps link, while B and C are connected by a 512 Kbps link (bps = bits per second).
Assuming that the packets are correctly delivered, how many bytes, including headers, are delivered to the IP layer at the destination for one application message, in the best case? Consider only data packets.
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200
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220
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240
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260
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Question 37 Explanation:
Application data is 180 bytes. TCP layer add 20 bytes to it and passes to IP layer,
data for IP layer becomes 200 byte. HA send packet by adding 20 byte of IP header. So total size of IP packet is 220 bytes. Since, maximum packet size for packet in network A is 1000 bytes, there will be no fragmentation at network A. IP Layer at Network B removes IP header and receive 200 bytes of data. Network B has Maximum packet size 100 bytes including 20 byte IP header, network B divide data in 80 bytes fragments and add 20 byte of IP header to it.
Data will be divided in three packets as:
First packet: 80 bytes + 20 byte of header
Second packet: 80 bytes + 20 byte of header
Third packet: 40 bytes + 20 byte of header
Note: Defragmentation (grouping of fragments) is done only at destination.
HC will receive total 260 bytes including header.
data for IP layer becomes 200 byte. HA send packet by adding 20 byte of IP header. So total size of IP packet is 220 bytes. Since, maximum packet size for packet in network A is 1000 bytes, there will be no fragmentation at network A. IP Layer at Network B removes IP header and receive 200 bytes of data. Network B has Maximum packet size 100 bytes including 20 byte IP header, network B divide data in 80 bytes fragments and add 20 byte of IP header to it.
Data will be divided in three packets as:
First packet: 80 bytes + 20 byte of header
Second packet: 80 bytes + 20 byte of header
Third packet: 40 bytes + 20 byte of header
Note: Defragmentation (grouping of fragments) is done only at destination.
HC will receive total 260 bytes including header.
Correct Answer: D
Question 37 Explanation:
Application data is 180 bytes. TCP layer add 20 bytes to it and passes to IP layer,
data for IP layer becomes 200 byte. HA send packet by adding 20 byte of IP header. So total size of IP packet is 220 bytes. Since, maximum packet size for packet in network A is 1000 bytes, there will be no fragmentation at network A. IP Layer at Network B removes IP header and receive 200 bytes of data. Network B has Maximum packet size 100 bytes including 20 byte IP header, network B divide data in 80 bytes fragments and add 20 byte of IP header to it.
Data will be divided in three packets as:
First packet: 80 bytes + 20 byte of header
Second packet: 80 bytes + 20 byte of header
Third packet: 40 bytes + 20 byte of header
Note: Defragmentation (grouping of fragments) is done only at destination.
HC will receive total 260 bytes including header.
data for IP layer becomes 200 byte. HA send packet by adding 20 byte of IP header. So total size of IP packet is 220 bytes. Since, maximum packet size for packet in network A is 1000 bytes, there will be no fragmentation at network A. IP Layer at Network B removes IP header and receive 200 bytes of data. Network B has Maximum packet size 100 bytes including 20 byte IP header, network B divide data in 80 bytes fragments and add 20 byte of IP header to it.
Data will be divided in three packets as:
First packet: 80 bytes + 20 byte of header
Second packet: 80 bytes + 20 byte of header
Third packet: 40 bytes + 20 byte of header
Note: Defragmentation (grouping of fragments) is done only at destination.
HC will receive total 260 bytes including header.
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