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CATA protocol in Computer Network

  • Last Updated : 10 Jul, 2020

Collision Avoidance Time Allocation (CATA) Protocol is a Contention Based MAC Protocols with Reservation which is based on dynamic topology dependent transmission scheduling. In this, time is broken into frames, every frame is divided into slots, and each slots is divided into 5 mini-slots. Initial four mini-slots are control ones, CMS, just fifth is utilized for information transmission, DMS, and it is longer than CMS.

The advantage of CATA is that it can perform broadcast, multicast, and uni-cast form of transmissions at same time without any difficulty. Its significant disadvantage is misuse of data transfer capacity due to control mini slots. Saving four mini slots spaces in each slots decreases accessible transfer speed reserved for transmission of information packets.

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CATA has two basic principles :

  1. The receiver of a flow must give information to other potential source nodes about reservation of slot, and interference in slot.
  2. Negative acknowledgements are used for reservation request and control packet transmission.

Working :

  1. CMS1 is employed to supply a “busy tone” to senders making an attempt to establish transmissions. each node that receives information throughout DMS of this slot sends a slot reservations packet (SR) in CMS1, that causes noise or is received by its neighbor nodes and prevents them from making an attempt to order this slot.
  2. In addition, each node that sends information throughout DMS of this slot sends a call for participation to send (RTS) packet throughout CMS2.
  3. This action causes interference to all or any neighboring nodes that didn’t hear SR of receiver node in CMS1 and are attempting to hold slot.
  4. The sender and receiver node stay quiet during CMS3 and sender sends a not to send (NTS) parcel during CMS4.
  5. With this technique CATA guarantees that after an effective reservation, a similar slot in next frame will remain collision free until message transmission is finished and end of reservation, killing all uncovered and concealed terminal issues.
  6. For situation a node needs to reserve a spot for multicast or broadcast transmission, it sends a RTS during CMS2.
  7. In event that planned receivers got RTS accurately, they stay quiet during CMS3 and CMS4 else they send a NTS at CMS4 as a negative recognition to planned multicast or broadcast reservation.
  8. The sender node of multicast or broadcast RTS finds that reservation is failed either in event that it gets a NTS or commotion (because of numerous NTS) during CMS4.
  9. Else it can begin transmitting information in DSM of present slot and in a similar slot in all ensuing outlines until end of message and ending of reservation.
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