Short Interframe Space is the small time interval between the data frame

Data frame

In computer networking and telecommunication, a frame is a digital data transmission unit or data packet that includes frame synchronization, i.e. a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits...

 and its acknowledgment

Acknowledgment

Acknowledgment may refer to:*Acknowledgment , a statement of gratitude for assistance in producing a work...

. SIFS are found in IEEE 802.11 networks. They are used for the highest priority transmissions enabling stations with this type of information to access the radio link first. This value is fixed per PHY

PHY

PHY is an abbreviation for the physical layer of the OSI model.An instantiation of PHY connects a link layer device to a physical medium such as an optical fiber or copper cable. A PHY device typically includes a Physical Coding Sublayer and a Physical Medium Dependent layer. The PCS encodes and...

 and is calculated in such a way that transmitting station will be able to switch back to receive mode and be capable of decoding the incoming packets. Examples of information which will be transmitted after the SIFS has expired include ACK (acknowledgement) and CTS (Clear To Send) messages.
A SIFS duration is a constant value and it depends on the amendments.

Standard	SIFS (μs)
IEEE 802.11b	10
IEEE 802.11a	16
IEEE 802.11g	10

See also

• DIFS - DCF Interframe Space
  DIFS
  In the DCF protocol, a station has to sense the status of the wireless medium before transmitting. If the medium is continuously idle for DCF Interframe Space duration, only then it is supposed to transmit a frame...
  
  
• RIFS - Reduced Interframe Space
  Reduced Interframe Space
  Reduced Interframe Space is one of the new feature introduced in IEEE 802.11n to improve its efficiency. It is used as an alternative for SIFS in some scenarios....
  
  
• PCF - Point Coordination Function
  Point Coordination Function
  Point coordination function is a Media Access Control technique used in IEEE 802.11 based WLANs. It resides in a point coordinator also known as Access Point , to coordinate the communication within the network. The AP waits for PIFS duration rather than DIFS duration to grasp the channel...