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The mac layer
The document summarizes key aspects of the MAC (Media Access Control) layer. It discusses how the MAC layer provides MAC addressing using unique identifiers for each device and provides multiple access to allow multiple devices to share the same communication channel. It describes different multiple access protocols like random access, CSMA, polling, and channelization methods including FDMA, TDMA, and CDMA that control how devices access and share the channel.
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The mac layer
- 1. The MAC layer Guidedby: Presented by: Mr. Atma Prakash Mohd Waseem CS-3rd Year
- 4. Functions To provideMAC Addressing. To provide Multiple Access.
- 5. MAC Addressing A MAC address is a unique serial number. Once a MAC address has been assigned to a particular network interface (typically at time of manufacture), that device should be uniquely identifiable amongst all other network devices in the world. This guarantees that each device in a network will have a different MAC address (analogous to a street address).
- 6. Multiple Access The channel access control mechanisms provided by the MAC layer are also known as a multiple access protocol. This makes it possible for several stations connected to the same physical medium to share it.
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- 8. Random Access In random access or contention methods, no station is superior to another station and none is assigned the control over another. No station permits, or does not permit, another station to send. At each instance, a station that has data to send uses a procedure defined by the protocol to make a decision on whether or not to send. This decision depends on the state of the medium (idle or busy). In other words, each station can transmit when it desires on the condition that it follows the predefined procedure, including the testing of the state of the medium.
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- 10. CSMA/CA There are threestrategies to avoid a collision: Interframe Space (IFS) Contention Window Acknowledgment
- 11. Controlled Access In controlled access, the stations consult one another to find which station has the right to send. A station cannot send unless it has been authorized by other stations. We discuss three popular controlled- access methods.
- 12. Polling All dataexchanges must be made through a primary device. If the primary wants to receive data, it asks if the others want to send: this is poll function. If the primary wants to send data, it tells the secondary to get ready to receive: this is called select function.
- 13. Channelization Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between different stations. In this section, we discuss three channelization protocols: FDMA, TDMA, and CDMA.
- 14. FDMA In frequency-division multiple access, the available bandwidth is divided into frequency bands. Each station is allocated a band to send its data.
- 15. TDMA In time-division multiple access, the stations share the bandwidth of the channel in time. Each station is allocated a time slot during which it can send data.
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