<html><head></head><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:16px"><div id="yui_3_16_0_1_1448118027073_3073">Dears all;</div><div id="yui_3_16_0_1_1448118027073_3156"><br></div><div id="yui_3_16_0_1_1448118027073_3246">How I can use the Interest Nack in the ndnSIM 2.1 for notifying the problems of forwarding to the nodes in downstream?</div><div id="yui_3_16_0_1_1448118027073_3245"><br></div><div id="yui_3_16_0_1_1448118027073_3244">Best regards<br></div><div id="yui_3_16_0_1_1448118027073_3243"> <br></div></div></body></html>