The present invention provides a method that includes accessing a first identifier associated with an idle mobile unit having a first session with a first subnet and a second identifier associated with a second subnet and determining whether the idle mobile unit has moved from the first subnet to the second subnet based on first portions of the first and second identifiers. The method also includes determining whether the first and second subnets are included in a first plurality of subnets based on second portions of the first and second identifiers and selecting one of a plurality of call session transfer techniques for transferring the first session from the first subnet to the second subnet based on whether the first and second subnets are included in the first plurality of subnets.