Program to look at network traffic/activity

is there a program that allows me to look at exactly what program is using my wireless connection?

every 30 seconds i get a lag spike and i am thinking its a piece of software using my connection to look for something...an update or maybe something else. so my thought is if i could find a program that told me what system process is using bandwidth i could look at that and it would tell me what program is utilizing my wireless connection every 30 seconds.

good idea? any help is appreciated