The serial number is in the bind file, and it tells the DNS servers that the information has changed. Incrementing the serial number is like incrementing a version.
Oh, and it's "propAgation" (for you and a few others). ;-)
So the DNS looks at the SN to tell whether it needs...
...to go through the pain of propagating a new list?
jb4 "So don't pay attention to the approval ratings that say 68% of Americans disapprove of the job this man is doing. I ask you this, does that not also logically mean that 68% approve of the job he's not doing? Think about it. I haven't." — Stephen Colbert, at the White House Correspondent's Dinner 29Apr06
jb4 "So don't pay attention to the approval ratings that say 68% of Americans disapprove of the job this man is doing. I ask you this, does that not also logically mean that 68% approve of the job he's not doing? Think about it. I haven't." — Stephen Colbert, at the White House Correspondent's Dinner 29Apr06