A device or software application that enables the user to analyze the performance of network data so as to ensure that the network and its associated hardware/software are operating within network specifications.
Source(s):
NIST SP 800-82 Rev. 2
from
The Automation, Systems, and Instrumentation Dictionary
Software that can reassemble streams from individual packets and decode communications that use various protocols.
Source(s):
NIST SP 800-86