15.4.4 Packet Size And Fragmentation
Every communication network has a maximum packet size that it can carry efficiently. This limit is known as the Maximum Transmission Unit (MTU).
If a packet is larger than the MTU supported by the next network, it must either be fragmented into smaller packets or transmitted in a different form. IPv4 permits fragmentation by routers, when necessary, although this increases processing overhead and may reduce performance.
IPv6 simplifies router operation by requiring fragmentation to be performed only by the source host. Intermediate routers therefore forward packets without performing fragmentation, improving forwarding efficiency in high-speed networks.
Where possible, modern communication systems avoid fragmentation by selecting packet sizes that are compatible with the smallest MTU along the communication path.
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