1 unaware of this sends configure request frame f 1 to node 2 to request four class service flow control node 2 refuses the request by transmitting a return configure nak frame f 2 frame f 2 contains a flow control option with parameters that would be acceptable to node 2 e g simple flow control with a suggested pause time the pause time could for instance correspond to the available transmit buffer space that node 2 could use to buffer frames during a pause node 1 transmits a new configure request frame f 3 including the simple flow control parameters received in frame f 2 node 2 accepts the options of frame f 3 by returning a configure ack frame f 4 node 2 also negotiates simple flow control for its end of the link as shown in frames f 5 and f 6 in similar fashion to the previous example fig1 c illustrates an lcp option negotiation session where node 2 either does not recognize or refuses to participate in flow control node 1 unaware of this sends configure request frame f 1 to node 2 to request simple flow control node 2 returns configure reject frame f 2 repeating the flow control option to inform node 1 that it will not accept any flow control option unless node 1 wants to drop.