ly allocated by the sending node. 5.3.1 Existing Solutions Problems The 3GPP standards do not specify how the packet core should be implemented; they only specify the network entities (SGSN, etc.), the functions each network entity should provide, and the interfaces and protocols by which the network entities communicate. Most implementations of the packet core use servers or pools of servers dedicated to a specific network entity. For example, a pool of servers may be set up to host SGSNs. When additional signaling demand requires extra capacity, an additional SGSN instance is started on the server pool, but when demand is low for the SGSN and high for, for example, the HSS, the HSS servers will be busy while the SGSN servers may remain underutilized. In addition, server pools that are underutilized will still consume power and require cooling even though they are essentially not doing any useful work. This results in an additional expense to the operator. An increasing trend in mobile networks is for managed services companies to build and run mobile operator networks, while the mobile operator itself handles marketing, billing, and customer relations. Mobile operator-managed service companies may have contracts with multiple competing operators in a single geographic region. A mobile operator has a reasonable expectation that the signaling and data traffic for their network is kept private and that isolation is maintained between the traffic for their network and for that of their competitors, even though their network and their competitors' networks may be managed by the same managed service companies. The implementation technology described earlier requires the managed services company to maintain a completely separate server pool and physical signaling network for each mobile operator under contract. The result is that there is a large duplication of underutilized server capacity, in addition to additional power and cooling requirements, between the operators. The packet core architecture also contains litt