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 packets or
network frames. Depending on the
physical layer
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip.
The ...
protocol or
encoding
In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...
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
In telecommunications, guard intervals are used to ensure that distinct transmissions do not interfere with one another, or otherwise cause overlapping transmissions. These transmissions may belong to different users (as in TDMA) or to the same ...
.
Ethernet
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
devices must allow a minimum idle period between transmission of
Ethernet packet
In computer networking, an Ethernet frame is a data link layer protocol data unit and uses the underlying Ethernet physical layer transport mechanisms. In other words, a network packet, data unit on an Ethernet link transports an Ethernet frame ...
s.
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
Bit time is a concept in computer networking. It is defined as the time it takes for one bit to be ejected from a network interface controller (NIC) operating at some predefined standard speed, such as 10 Mbit/s. The time is measured betwe ...
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
A frame check sequence (FCS) is an error-detecting code added to a frame in a communication protocol. Frames are used to send payload data from a source to a destination.
Purpose
All frames and the bits, bytes, and fields contained within ...
of one frame to the start of the
preamble
A preamble is an introductory and expressionary statement in a document that explains the document's purpose and underlying philosophy. When applied to the opening paragraphs of a statute, it may recite historical facts pertinent to the subj ...
for the next.
During data reception, some interpacket gaps may be smaller due to variable network delays, clock tolerances (all speeds), and the presence of repeaters (10 Mbit/s only).
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.
Fibre Channel
For
Fibre Channel
Fibre Channel (FC) is a high-speed data transfer protocol providing in-order, lossless delivery of raw block data. Fibre Channel is primarily used to connect computer data storage to servers in storage area networks (SAN) in commercial data cen ...
, there is a sequence of
primitives between successive
frames
A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent.
Frame and FRAME may also refer to:
Physical objects
In building construction
*Framing (co ...
, sometimes called ''interframe gap'' as well. The minimum sequence consists of six primitives,
IDLE, IDLE, R_RDY, R_RDY, IDLE, IDLE. Each primitive consists of four channel words of 10 bits each for
8b/10b encoded variants (1–8 Gbit/s), equivalent to four data bytes.
[FC-PH REV 4.3, June 1, 1994, Table 25 ''Primitive Signals'']
References
{{Reflist
Ethernet