A system for performing stateful Diameter routing with Diameter routing agents that use different mechanisms to achieve stateful routing, the system comprising: a plurality of Diameter signaling routing nodes, each node having access to at least one of a plurality of databases for maintaining state information, wherein at least some of the plurality of nodes are configured to be members of a first group; and wherein each member of the first group is configured to use a first mechanism to achieve stateful routing with other members of the first group, and to use a second mechanism to achieve stateful routing with nodes that are not members of the first group, wherein a first member of the first group is further configured to operate as a mated pair with a node that is not a member of the first group, and wherein the first node is configured to: receive a Diameter request to establish a first session for a subscriber; determine whether its database contains state information associated with the subscriber; upon a determination that its database contains state information associated with the subscriber, process the Diameter request according to the state information associated with the subscriber; upon a determination that its database does not contain state information associated with the subscriber, determine whether the mate's database contains state information associated with the subscriber; upon a determination that the mate's database contains state information associated with the subscriber, retrieve the state information from the mate, process the Diameter request according to the state information associated with the subscriber, and store in its database the state information received from the mate; upon a determination that the mate's database does not contain state information associated with the subscriber, create state information associated with the subscriber, process the Diameter request according to the created state information, and store the created state information in its database. a plurality of Diameter signaling routing nodes, each node having access to at least one of a plurality of databases for maintaining state information, wherein at least some of the plurality of nodes are configured to be members of a first group; and wherein each member of the first group is configured to use a first mechanism to achieve stateful routing with other members of the first group, and to use a second mechanism to achieve stateful routing with nodes that are not members of the first group, wherein a first member of the first group is further configured to operate as a mated pair with a node that is not a member of the first group, and wherein the first node is configured to: receive a Diameter request to establish a first session for a subscriber; determine whether its database contains state information associated with the subscriber; upon a determination that its database contains state information associated with the subscriber, process the Diameter request according to the state information associated with the subscriber; upon a determination that its database does not contain state information associated with the subscriber, determine whether the mate's database contains state information associated with the subscriber; upon a determination that the mate's database contains state information associated with the subscriber, retrieve the state information from the mate, process the Diameter request according to the state information associated with the subscriber, and store in its database the state information received from the mate; upon a determination that the mate's database does not contain state information associated with the subscriber, create state information associated with the subscriber, process the Diameter request according to the created state information, and store the created state information in its database. receive a Diameter request to establish a first session for a subscriber; determine whether its database contains state information associated with the subscriber; upon a determination that its database contains state information associated with the subscriber, process the Diameter request according to the state information associated with the subscriber; upon a determination that its database does not contain state information associated with the subscriber, determine whether the mate's database contains state information associated with the subscriber; upon a determination that the mate's database contains state information associated with the subscriber, retrieve the state information from the mate, process the Diameter request according to the state information associated with the subscriber, and store in its database the state information received from the mate; upon a determination that the mate's database does not contain state information associated with the subscriber, create state information associated with the subscriber, process the Diameter request according to the created state information, and store the created state information in its database.