Dynamic addressing is commonly used; a mobile endpoint is assigned an IP address when it connects to a wireless access point or a cellular network using a protocol such as DHCP. This address is often not a routable IP address, being assigned from a pool of locally defined IP addresses that are not routable. NAT maps a locally defined address to a routable IP address, often at an edge router (e.g. FIG. 1, 120a, 120c). When this happens, the end user system does not know the IP address that it uses on the IP-based network. If the system detects an anomalous condition, the system may probe the network to determine the effective IP address that is assigned to the system for use on the IP-based network (as opposed to the unrouteable local IP address assigned to the system) and use that IP address in its metrics comparisons. Probing for the effective IP address may be performed making a query to the edge router, or by the well-known technique of making a connection to a system beyond the edge router and determining the IP address presented during that connection request. Whatever method is used, the endpoint system is now in possession of its effective IP address, and may use that information in its subsequent calculations. Note that the probing need only be performed periodically by the system, as the effective IP address will not change while an IP session is maintained.

Alternatively or in addition, the system may determine the location of the endpoint device using external means (such as GPS or cell tower triangulation). This location may be mapped to a location that is used to determine an appropriate effective IP address, for example if one cannot be otherwise determined.