Access method (network)
The media access in networks is determined via the access method . In the OSI model , this is understood to mean communication between the physical layer (layer 1 = bit transmission layer) and the MAC layer (layer 2a = part of the security layer).
The access procedure regulates which station, ie which data terminal is allowed to transmit which amount of data to whom at which point in time.
In the LAN, it is important to determine how the stations and network components involved access the network cable. Controlling access and the associated transmission of suitable data within a defined framework are among the main tasks of the MAC layer. In connection with the MAC layer, one does not usually speak of network cables, but of transmission media.
Known access methods
CSMA / CD (Carrier Sense Multiple Access / Collision Detection)
This is the best-known and also the oldest access method for shared media operations. It covers the procedures for
- Activity monitoring and multiple access ( CSMA )
- with collision detection (CD).
CSMA / CD was standardized by the IEEE working group, as were the further developments:
- IEEE 802.3 for the Ethernet ,
- IEEE 802.3u for Fast Ethernet,
- IEEE 802.3z for Gigabit Ethernet.
Further access methods based on CSMA are: CSMA / CA and CSMA / CR .
While chance plays a decisive role in the CSMA / CD method, the class of token-passing methods is a controlled access method. By assigning a transmission permit, it is ensured that exactly one data terminal device gets access to the network and is allowed to transmit at a certain time. The right to send is passed on from data terminal to data terminal with a token circulating in the network (a token for the transmission authorization).
Token passing has been standardized by the IEEE working group in two variants:
- IEEE 802.4 for token bus
- IEEE 802.5 for Token-Ring
- Dirk Larisch: The beginners' seminar on network technology. 3rd edition, hjr-Verlag, Heidelberg 2010, ISBN 978-3-8266-7515-7 .
- Rüdiger Schreiner: Computer Networks. From the basics of function and application, 4th edition, Carl Hanser Verlag, Munich 2012, ISBN 978-3-446-43117-1 .
- Rainer Egewardt: PC knowledge for IT professions . Hardware - Operating Systems - Network Technology, 2nd edition, Friedrich Vieweg & Sohn Verlag, Wiesbaden 2002, ISBN 978-3-528-15739-5 .
- Peter Welzel: Remote data transmission. Introductory basics for communication between open systems, Springer Fachmedien, Wiesbaden 1986, ISBN 978-3-663-00129-4 .
- Klaus Dembowski: Local Networks. Handbook of complete network technology, Addison-Wesley Verlag, Munich 2007, ISBN 978-3-8273-2573-0 .
- Klaus-Dieter Thies: Elementary introduction to local networks and distributed systems, SHAKER Verlag, Aachen 2014, ISBN 978-3-8440-3005-1
- IEEE 802.3 standards
- Access procedures in networks (accessed on August 4, 2017)
- Process automation technology communication networks (accessed on August 4, 2017)
- Token-Ring Access Procedure (accessed August 4, 2017)
- Access procedure CSMA / CD CSMA / CA (accessed on August 4, 2017)