Multiple choice

Consider three IP networks A, B and C. Host HA in network A send 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.

  1. 200

  2. 220

  3. 240

  4. 260
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

At A Data + Header = 200 bytes. This would require only 1 packet of N/W A At B 200 bytes of payload from network A is packed in 80 payload + 20 header packet. This would require 20+80 20 + 80 20+40 Packets total 260 bytes. These are transferred to C

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