Interpacket gap

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Ethernet devices must allow a minimum idle period between transmission of Ethernet packets known as the interpacket gap (IPG), interframe spacing, or interframe gap (IFG).[1] A brief recovery time between packets allows devices to prepare for reception of the next packet. The standard minimum interpacket gap is 96 "bit times" (the time it takes to transmit 96 bits of raw data on the medium), which is

Some adapter manufacturers design their adapters with a smaller interpacket gap for higher data transfer rates, which can lead to a high rate of collisions. An example is Intel EtherExpress 100B.[2]

Smaller IPG are possible on repeaters towards the DTE (Data terminal equipment) and MII (Media Independent Interface) into the MAC (Media Access Control), that is when the packet is received by a node. This is to account for variable network delays, added preamble bits, and clock tolerances.

On reception, some interpacket gaps may be smaller due to variable network delays, clock tolerances, and the presence of repeaters.[1]

  • For 40/100 Gigabit Ethernet received IPG can be reduced to a period of 8 bit times (1 byte).
  • For 10 Gigabit Ethernet received IPG can be reduced to a period of 40 bit times (5 bytes).
  • For gigabit Ethernet received IPG can be reduced to a period of 64 bit times (8 bytes).
  • For Fast Ethernet received IPG reduction is not specified. Standard is 96 bit times (12 bytes).
  • For Ethernet received IPG can be reduced to a period of 47 bit times.

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