The NAB provides data buffering protection against a small number of TCP connections consuming an undue number of internal buffers or service time, where such consumption could degrade service to other TCP connections. This data buffering protection applies to ingress and egress TCP connections on the P-7500 system.
If the NAB detects that a backlog of at least 5k buffers has built up in the system’s message processing stage, and there is received data ready for processing on more than one TCP connection, the NAB gives a higher service priority to TCP connections that have been recently sending data to the NAB at a lower-than-average rate over TCP connections than to those that have been recently sending data to the NAB at a higher-than-average rate.
While this data buffering protection applies to all TCP connections, it is most typically used against clients that are sending data to the NAB at a rate that is disproportionately consuming NAB resources.
If the NAB detects that a backlog of at least 10k buffers has built up in the system’s message processing stage, the NAB momentarily defers service of all ingress TCP data, to limit the ingress data rate to a level that the P-7500 can service.
In either case, when the NAB stops servicing ingress TCP data on some or all TCP connections, the peer TCP client limits its sending rate and, if necessary, applies back pressure to the sending client application.
If the NAB detects that more than 70% of its allotted egress buffers are in use, and there are some TCP connections which have had backlogged egress data more than 88% of the time in at least the preceding minute, those TCP connections are disconnected and their buffers are freed.
While this protection applies to all TCP connections, it is most typically used against clients that are unable to process the volume of data sent to them as a result of their subscriptions.