forwarding/l2_learning: add some comments
forwarding/l2_learning: add some comments

xAKLx/pox,denovogroup/pox,andiwundsam/_of_normalize,MurphyMc/pox,kulawczukmarcin/mypox,pthien92/sdn,MurphyMc/pox,xAKLx/pox,waltznetworks/pox,chenyuntc/pox,diogommartins/pox,kpengboy/pox-exercise,waltznetworks/pox,diogommartins/pox,denovogroup/pox,waltznetworks/pox,kulawczukmarcin/mypox,kavitshah8/SDNDeveloper,MurphyMc/pox,noxrepo/pox,kavitshah8/SDNDeveloper,pthien92/sdn,jacobq/csci5221-viro-project,xAKLx/pox,xAKLx/pox,chenyuntc/pox,kulawczukmarcin/mypox,VamsikrishnaNallabothu/pox,kpengboy/pox-exercise,waltznetworks/pox,noxrepo/pox,PrincetonUniversity/pox,xAKLx/pox,VamsikrishnaNallabothu/pox,diogommartins/pox,carlye566/IoT-POX,denovogroup/pox,adusia/pox,denovogroup/pox,jacobq/csci5221-viro-project,noxrepo/pox,VamsikrishnaNallabothu/pox,adusia/pox,kavitshah8/SDNDeveloper,PrincetonUniversity/pox,carlye566/IoT-POX,chenyuntc/pox,jacobq/csci5221-viro-project,carlye566/IoT-POX,pthien92/sdn,denovogroup/pox,adusia/pox,carlye566/IoT-POX,andiwundsam/_of_normalize,chenyuntc/pox,kpengboy/pox-exercise,kpengboy/pox-exercise,PrincetonUniversity/pox,adusia/pox,MurphyMc/pox,kpengboy/pox-exercise,VamsikrishnaNallabothu/pox,pthien92/sdn,diogommartins/pox,PrincetonUniversity/pox,kulawczukmarcin/mypox,VamsikrishnaNallabothu/pox,jacobq/csci5221-viro-project,kulawczukmarcin/mypox,carlye566/IoT-POX,PrincetonUniversity/pox,diogommartins/pox,adusia/pox,waltznetworks/pox,chenyuntc/pox,andiwundsam/_of_normalize,kavitshah8/SDNDeveloper,pthien92/sdn,andiwundsam/_of_normalize,jacobq/csci5221-viro-project,MurphyMc/pox,noxrepo/pox