Which statement best describes a key difference in IPv6 fragmentation support compared to IPv4?
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A. B. C. D. E.E.
IPv6 was designed with a number of improvements over IPv4, and one of these was in regards to fragmentation support. Fragmentation is the process of breaking a packet into smaller fragments to ensure that it can be transmitted across networks with different MTUs. IPv6 addresses fragmentation in a different way than IPv4. The key difference between IPv6 fragmentation support and IPv4 fragmentation support is that IPv6 relies on Path MTU Discovery (PMTUD) to avoid the need for fragmentation, whereas IPv4 relies on fragmentation.
Option A states that in IPv6, IP fragmentation is no longer needed because all Internet links must have an IP MTU of 1280 bytes or greater. This statement is true in the sense that IPv6 requires that all links support a minimum MTU of 1280 bytes, which is larger than the 576 byte minimum required by IPv4. However, this statement does not fully describe the difference between IPv6 and IPv4 fragmentation support.
Option B states that in IPv6, PMTUD is no longer performed by the source node of an IP packet. This statement is false. In IPv6, PMTUD is still performed by the source node of an IP packet.
Option C states that in IPv6, IP fragmentation is no longer needed since all nodes must perform PMTUD and send packets equal to or smaller than the minimum discovered path MTU. This statement is true. In IPv6, all nodes are required to perform PMTUD, which allows them to determine the smallest MTU along the path between the source and destination. The nodes then send packets that are equal to or smaller than this minimum MTU, which avoids the need for fragmentation.
Option D states that in IPv6, PMTUD is no longer performed by any node since the don't fragment flag is removed from the IPv6 header. This statement is false. PMTUD is still performed in IPv6, even though the "don't fragment" flag is not present in the IPv6 header.
Option E states that in IPv6, IP fragmentation is performed only by the source node of a large packet, and not by any other devices in the data path. This statement is true. In IPv6, if a node needs to send a packet that is larger than the path MTU, it must fragment the packet at the source. No other devices in the data path are allowed to fragment the packet.
In summary, the correct answer is option C, which states that in IPv6, IP fragmentation is no longer needed since all nodes must perform PMTUD and send packets equal to or smaller than the minimum discovered path MTU.