IrLAP

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IrLAP is the protocol of the data link layer of the IrDa interface . IrLAP is based on the half-duplex protocols HDLC and SDLC .

One of the most important features is the concept of primary and secondary stations. The primary station (exactly one) is responsible for the connection. With so-called point-to-point connections there is only one single secondary station, with point-to-multipoint connections (which, however, have only been provided theoretically so far, but are not used in the currently used IrLAP protocol versions), however, there can be several give secondary station.

All transmissions go to or from the primary station, direct connections between secondary stations are not possible. In principle, each station can take on the role of the primary, provided it is able to do so due to the implementation. The primary station is determined when the connection is established and remains so until the connection is disconnected. This fact remains hidden behind the IrLAP service primitives, so that it does not play a role in their description.

IrLAP uses most of the HDLC standard frame formats. There are unnumbered U-frames, supervisory S-frames and information I-frames. U-frames are used for functions such as connection establishment and disconnection or searching for other devices (discovery). I-frames are used to transfer information from one station to another and S-frames are used to support the transmission of information, for example to explicitly confirm a data packet (I-frames can also implicitly confirm other I-frames) or for flow control.

IrLAP also contains functions for establishing and disconnecting connections with agreement on the quality of the connection (transmission rate, timeout times, etc.), for determining the addresses of devices within range and for resolving address conflicts.

literature

  • Uwe Hansmann, Lothar Merk, Martin S. Nicklous, Thomas Stober: Pervasive Computing Handbook. Springer Verlag, Berlin / Heidelberg 2001, ISBN 978-3-662-04320-2 .
  • RK Ghosh: Wireless Networking and Mobile Data Management. Springer Nature Pte Ltd, Singapore 2017, ISBN 978-981-10-3940-9 .
  • JK Petersen: The Telecommunications Illustrated Dictionary. Second Edition, CCR Press, Boca Raton 2002, ISBN 0-8493-1173-X .

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