1. A network device comprising: plurality of execution units; plurality of session initiation protocol (SIP) processes comprising: a SIP transport process; a SIP location server process; and a plurality of SIP core processes, the SIP transport process executing on a first one of the execution units and communicating with at least a portion of the SIP core processes through an inter-processor communication mechanism, the SIP location server Process executing on a second one of the execution units and communicating with the at least a portion of the SIP core processes through the inter-processor communication mechanism, wherein the SIP transport process receives an ingress SIP packet, transforms the ingress SIP packet to a corresponding message, and delivers the corresponding message to one of the plurality of SIP core processes; and wherein the one of the plurality of SIP core processes modifies the corresponding message to include a next hop destination and delivers the modified message to the SIP transport process; and wherein the SIP transport process transforms the modified message into an egress SIP packet for transmission outside the network device, each of the SIP core processes executing on a different remaining one of the execution units.