What are asynchronous protocol and synchronous protocol ?
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Answer:
here's ur answer dude
Explanation:
Asynchronous, power-saving protocols implicitly synchronize themselves on every data transmission, but synchronous protocols explicitly synchronize themselves before sending any actual data packets. Several methods for time synchronization exist [167,216]167216.
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Explanation:
10.2.2.3 Performance problems
The buffered protocol does not always outperform the synchronous protocol. In some cases, the buffered protocol is slower than the synchronous protocol. Figure 10.5 illustrates such a case, where the buffers are not ready to receive messages immediately. After three attempts at message transmission, the sender successfully sends its data to the receiver. However, the synchronous protocol needs to send data only once, after which the receiver can trigger the retry procedure immediately when buffers are available. The buffered protocol has two other disadvantages. First, this protocol may introduce a large amount of network traffic, which would increase network contention and consequently result in performance degradation. Second, the buffered protocol should send the confirmation message to the sender to release the sending buffer after the activation of the retry mechanism. This process may also degrade performance because of the additional message transmission and delayed sending buffer release.
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Figure 10.5. Performance problems. (a) Synchronous protocol. (b) Buffered protocol.
Smart Object Hardware and Software
Jean-Philippe Vasseur, Adam Dunkels, in Interconnecting Smart Objects with IP, 2010
11.3.3 Synchronous Duty Cycling
Although asynchronous, power-saving protocols such as LPL are useful in their simplicity, their performance can be improved by making them synchronous. Synchronous protocols are built on explicit time synchronization. Asynchronous, power-saving protocols implicitly synchronize themselves on every data transmission, but synchronous protocols explicitly synchronize themselves before sending any actual data packets. Several methods for time synchronization exist [167,216]167216.
With time synchronization, a synchronous protocol can reduce the time that the protocol has to keep the radio switched on reducing the overall power consumption. One example of a time-synchronized, power-saving protocol is TSMP [196]. TSMP is the basis of the two industrial sensor network standards WirelessHART and ISA100a. In addition to providing a long lifetime by switching the radio off as often as possible, TSMP also achieves high reliability by constantly switching the physical radio frequency on which packets are sent. The network is centrally managed so that the entire network is scheduled by a network manager (a small server located next to the network). TSMP is designed for industrial use and is not intended to be suitable for people- or home-centric smart objects applications.
In TSMP, all nodes are time synchronized within 50 μs. Time is divided into slots that are 10 ms long. In every slot, a node is either listening, potentially transmitting (if the node has data to transmit), or sleeping. When listening, the node listens for a short while at the beginning of the 10 ms time slot. If a node is transmitting in the time slot, the transmission will start within 100 μs. Thus, the receiver does not need to keep its radio on for longer than 100 μs every 10 ms in those time slots it is able to receive a packet.
The time-synchronized process is shown in Figure 11.23. The sender only needs to send a very short synchronization byte before sending its packet, because the receiver can quickly determine if there is a packet transmitted or not.
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Figure 11.23. With a time-synchronized protocol such as TSMP, nodes need shorter on-times because they know exactly when the sender potentially transmits reducing power consumption.
A Novel Requirements Metamodel for Automotive Electronic Network Design
Dra.Liliana Díaz-Olavarrieta, Dr.David Báez-López, in Fieldbus Systems and Their Applications 2005, 2006
5.2 Safety-Critical Protocols
An important consideration to match a protocol to the application is if the protocol is apt to implement a safety-critical fault tolerant application. There is a general opinion that time-triggered protocols are better suited than event-triggered protocols for safety-critical applications, given the deterministic nature of synchronous protocols needed to guarantee fault tolerance in safety-critical applications (Kopetz, 2003). In this respect, the only protocols which are currently accepted as fault-tolerant for safety-critical applications in 2005 are: TTP and SAFEBus™, (used in the avionics and automotive industries), SPIDER (non-commercial), and FlexRay (Rushby, 2001).
In what follows, we present in more detail the properties of the requirements for IVN networks in each of the four meta-model perspectives: user, application, CBD process, and industry context.
Federated Identity Technologies
Derrick Rountree, in Federated Identity Primer, 2013