A mapper's requests have the potential to trigger non-trivial amounts of network traffic originating from the responders. If the requests are carried out too frequently, they could contribute to network congestion. Therefore, the mapper is required to charge the responder to enable it to send out Ethernet frames at the mapper's request during topology discovery. The charge requirement spaces out the requests, mitigating Denial of Service attacks or inadvertent flooding.
Charging involves sending special frames to the responder to build up the charge. Only after enough charge has been accumulated can the mapper request the responder to carry out a topology test. Once the responder has verified that it has enough charge, it consumes the charge and fulfills the topology test.
Section 126.96.36.199 summarizes frames used during charging.
Section 188.8.131.52 summarizes how charge is tracked by responders.
Responders perform the following actions when receiving a Charge frame or Emit frame:
1) Accumulating charge from the frame (section 184.108.40.206).
2) Determining the charge requirements for the request (section 220.127.116.11).
3) Consuming charge (section 18.104.22.168).
4) Sending out frames.