No matter whether it is in wired network communication or in wireless network communication, in order to ensure effective data transmission between a data receiver and a data sender, flow control needs to be performed, so as to prevent overflow of data received by the data receiver because the amount of received data exceeds the processing capability of the data receiver or because of the storage space limitation of the data receiver, and to enable the data sender to reasonably determine, according to the processing capability of the data receiver, the speed of sending data, thereby effectively utilizing resources.
In various communication protocols, flow control mechanisms are concerned. For example, in an Interlaken protocol, an in-band flow control mechanism and an out-of-band flow control mechanism are provided. The Interlaken protocol is an optimized interconnection protocol developed by Cisco and Cortina in order to implement high bandwidth and reliable packet transmission. The protocol uses multiple serial links to establish a logical connection between components, and utilizes multiple information channels, the back pressure capability and the data integrity protection to improve the performance of communication equipment.
In the in-band flow control mechanism of the Interlaken protocol, the 40th bit to the 55th bit of a Burst control word and an Idle control word may be used to transfer in-band flow operation information, that is, flow operation information of information channels, so flow operation information of at most 16 information channels may be transferred once. When the number of the information channels is greater than 16 (assume that only information about the flow control at the information channel level is transmitted in a band), a first control word is used to transmit the flow operation information of 16 information channels of the first group, a second control word is used to transmit the flow operation information of 16 information channels of the second group, and so forth. After transmission of the flow operation information of information channels of the last group is completed, that is, after transmission of the flow operation information of the information channels is completed, transmission begins from the flow operation information of the 16 information channels of the first group again.
In a transmitted data stream, the proportion of a control word is generally far less than that of the data payload, and the refresh period of the control word is long. For the transmission of flow operation information of a certain information channel, in the worst case, that is, in the case that when the flow operation information of the information channel is updated, the moment of sending the flow operation information of the information channel is missed, the flow operation information of the information channel can be sent out in a next round only after waiting for the completion of sending the flow operation information of the information channel. When the number of the information channels is increased, the time required for the completion of sending the flow operation information of the information channels is increased, so that the delay for updating the flow operation information of the same information channel is increased.
Therefore, the flow operation information is transferred circularly according to a fixed sequence, the delay for updating the flow operation information of the same information channel is long, and it is difficult to update the flow operation information in time. Even if the flow operation information is not updated, the flow operation information occupies the control word transmission bandwidth, so that the transmission efficiency of the flow operation information of the information channel is further reduced.