Visitor Identification Methods   Urchin has five different
methods for identifying visitors and sessions, depending on
available information. Of these, the patent-pending Urchin
Traffic Monitor (UTM) is a highly accurate system that was
specifically designed to identify unique visitors, sessions,
exact paths, and return frequency behavior. There are a number
of visitor loyalty and client reports that are only available
when using the UTM System. The UTM System is easy to install and
is highly recommended for all businesses.  In addition to the
UTM System, Urchin can use IP addresses, User-Agents, Usernames,
and Session-IDs to identify sessions. The following table
compares the abilities of each of the five identification
techniques:  AbilityIP OnlyIP+User-AgentUsername Session ID UTM 
Identifies non-proxied sessions XXX XX Identifies some proxied
sessions XX XX Uniquely identifies each session XX Defeats
session IP proxying XX Defeats most provider caching XX Defeats
browser caching X Uniquely identifies visi