Interpacket Gap

Inter- Packet Gap ( IPG abbr, even Interframe Spacing IFS interframe gap IFG ) refers to computer networks at the minimum time interval between two packets transmitted on the transmission medium. There are several reasons for maintaining this minimum distance; this can be both a technical nature (eg, Ethernet ) and a consequence of the underlying network protocol ( eg WLAN standards IEEE 802.11).

Ethernet

The minimum waiting time between two transmitted Ethernet packets is basically 96 bit times, for example at 10 Mbit / s 9.6 microseconds. Upon receipt, it is possible that shorter breaks occur:

  • With 40/100 Gigabit Ethernet minimal length of 8 bit (1 byte)
  • 10 Gigabit Ethernet minimum of 40 bit times ( 5 bytes )
  • Gigabit Ethernet minimal 64 bit times ( 8 bytes)
  • With Fast Ethernet no shorter break is defined, default is 96 bit times ( 12 bytes )
  • Ethernet at minimal 47 bit times

WLAN according to IEEE 802.11

The WLAN standard there are several different interframe spacings of different lengths. These are used to allow priorities for various types of data frames, and transmitting stations.

A distinction

  • SIFS (Short Inter Frame Spacing ): The amount of time before sending an acknowledgment frame ( ACK ), "Clear to Send" package ( CTSs ) or a polling response must be passed. In particular, since the reception of each regular unicast data frame needs to be confirmed by ACK, it is the SIFS to the most commonly used forthcoming Inter Frame Spacing.
  • PIFS ( Point Coordination Function Interframe Spacing ): The time indicated by the point coordinator (eg, the access point ) must be passed before sending PCF information.
  • DIFS (Distributed Coordination Function Interframe Spacing ): The time that must have elapsed before sending a regular data frame.
  • EIFS (Extended Inter- Frame Spacing ): The time that must have elapsed before sending after a collision is detected.

It is SIFS < PIFS < DIFS < EIFS.

Typical values ​​for the media access control in wireless networks are available for SIFS in the range of 10 microseconds and DIFS to 50 microseconds.

Credentials

  • Network architecture
Polling (computer science)
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