(1) (
Autonomous
System
Number) A unique identifier of an autonomous system on the Internet. Of the 65 thousand ASNs available, more than 30 thousand have been assigned to ISPs and NSPs. ISPs usually have only one ASN, but NSPs may have more than one. ASNs are maintained in the Routing Arbiter Database (RADB). See
autonomous system,
ISP and
NSP.
(2) (
Advance
Ship
Notice) A notice sent by the vendor to the customer indicating what merchandise has been shipped. It enables the receiver to identify a package's contents electronically without having to open it.