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ipethernetpackets

Larger packets than Ethernet frame can handle

IPv4 and IPv6 allow packets of up to 65,535 bytes. Ethernet frames supposedly only allows payloads of up to 1522 bytes.

How does this work? There are no sequence numbers in Ethernet frames to ensure order, which makes recreating a larger IP packet from Ethernet frames difficult...

Solution

  • Several points in bullet form:

    1. IP packets can be fragmented (see IP Fragmentation): the fragmentation and reassembly of IP datagrams is specified within IP.
    2. The layer encapsulating IP for a given flow may not necessarily be Ethernet from end to end (or even at all, see GRE)
    3. Path MTU is a means of determining the Maximum Transmission Unit for a given flow.
    4. Within a network, Jumbo Frames may be enabled to increase the ethernet frame size to 9000.