Editing Interpacket gap

{{Short description|Pause between sending network packets}}
{{Use American English|date = March 2019}}

In [[computer networking]], the '''interpacket gap''' ('''IPG'''), also known as '''interframe spacing''', or '''interframe gap''' ('''IFG'''), is a pause which may be required between [[network packet]]s or [[network frame]]s. Depending on the [[physical layer]] protocol or [[line code|encoding]] used, the pause may be necessary to allow for receiver [[clock recovery]], permitting the receiver to prepare for another packet (e.g. powering up from a low-power state) or another purpose. It may be considered as a specific case of a [[guard interval]].

==Ethernet==
[[Ethernet]] devices must allow a minimum idle period between transmission of [[Ethernet packet]]s<!-- intentional redirect -->.<ref name="802.3" /> A brief recovery time between packets allows devices to prepare for reception of the next packet. While some physical layer variants literally transmit nothing during the idle period, most modern ones continue to transmit an idle pattern signal. The standard minimum interpacket gap for transmission is 96 [[bit time]]s (the time it takes to transmit 96 bits of data on the medium). The time is measured from the end of the [[frame check sequence]] of one frame to the start of the [[Preamble (communication)|preamble]] for the next.{{Ref RFC|1242|notes=no|rp=5}}

During data reception, some interpacket gaps may be smaller due to variable network delays, clock tolerances (all speeds), and the presence of repeaters (10&nbsp;Mbit/s only).

{| class="wikitable"
|+Ethernet IPG<ref name="802.3">{{cite web|title= IEEE 802.3 ''4.4.2 MAC parameters''| url= https://ieeexplore.ieee.org/browse/standards/get-program/page/series?id=68 | access-date=2022-02-19}}</ref>
!Ethernet variant
!Minimum transmitted IPG
!Minimum received IPG
|-
|[[Classic Ethernet|10 Mbit/s Ethernet]]
|{{val|9.6|ul=us}}
|{{val|4.7|u=us}} (47 bit times)
|-
|[[Fast Ethernet|100 Mbit/s (Fast) Ethernet]]
|{{val|0.96|u=us}}
|{{val|0.96|u=us}} (96 bit times)<ref>IEEE 802.3 Annex 27A ''Repeater delay consistency requirements''</ref>{{dubious|Minimum IPG for Fast Ethernet|date=November 2021}}
|-
|[[Gigabit Ethernet]]
|{{val|96|ul=ns}}
|{{val|64|u=ns}} (64 bit times)
|-
|[[2.5GBASE-T and 5GBASE-T|2.5 Gigabit Ethernet]]
|{{val|38.4|u=ns}}
|{{val|16|u=ns}} (40 bit times)
|-
|[[2.5GBASE-T and 5GBASE-T|5 Gigabit Ethernet]]
|{{val|19.2|u=ns}}
|{{val|8|u=ns}} (40 bit times)
|-
|[[10 Gigabit Ethernet]]
|{{val|9.6|u=ns}}
|{{val|4|u=ns}} (40 bit times)
|-
|[[25 Gigabit Ethernet]]
|{{val|3.84|u=ns}}
|{{val|1.6|u=ns}} (40 bit times)
|-
|[[40 Gigabit Ethernet]]
|{{val|2.4|u=ns}}
|{{val|200|ul=ps}} (8 bit times)
|-
|[[50 Gigabit Ethernet]]
|{{val|1.92|u=ns}}
|{{val|160|u=ps}} (8 bit times)
|-
|[[100 Gigabit Ethernet]]
|{{val|0.96|u=ns}}
|{{val|80|u=ps}} (8 bit times)
|-
|[[200 Gigabit Ethernet]]
|{{val|0.48|u=ns}}
|{{val|40|u=ps}} (8 bit times)
|-
|[[400 Gigabit Ethernet]]
|{{val|0.24|u=ns}}
|{{val|20|u=ps}} (8 bit times)
|}

Some manufacturers design adapters transmitting with a smaller interpacket gap for slightly higher data transfer rates. That can lead to data loss when mixed with standard adaptors.<ref>{{cite web |url=http://www.wildpackets.com/resources/compendium/ethernet/interframe_gap |title=Interframe Gap and Spacing |publisher=[[WildPackets]] |accessdate=2015-03-20}}</ref><ref>{{cite web | title = Intel EtherExpress 100B - High rate of collisions on 100-megabit networks | url = http://support.microsoft.com/kb/315237 | publisher = Microsoft co | accessdate = 2010-01-16 | archive-date = 2010-01-30 | archive-url = https://web.archive.org/web/20100130172830/http://support.microsoft.com/kb/315237 | url-status = dead }}</ref>

==Fibre Channel==
For [[Fibre Channel]], there is a sequence of [[Fibre Channel network protocols#Primitives|primitives]] between successive [[Fibre Channel frame|frames]], sometimes called ''interframe gap'' as well. The minimum sequence consists of six primitives, <code>IDLE|IDLE|R_RDY|R_RDY|IDLE|IDLE</code>.<ref>FC-PH REV 4.3, June 1, 1994, Clause 17.1 ''Frame Transmission''</ref> Each primitive consists of four channel words of 10 bits each for [[8b/10b encoding|8b/10b encoded]] variants (1–8&nbsp;Gbit/s), equivalent to four data bytes.<ref>FC-PH REV 4.3, June 1, 1994, Table 25 ''Primitive Signals''</ref>

==References==
{{Reflist}}

[[Category:Ethernet]]