Method for achieving high-availability of itineraries in a real-time network scheduled packet routing system

A method for scheduling real time data across a network comprising the steps of:

• identifying a set of possible paths across a network to satisfy a request;
• using predetermined graph traversal methods to search the identified set for available packet handling appointments until an available appointment path is found, or until predetermined halting criteria are reached, wherein said search includes, for each path from said identified set, examining appointment slots along said path to determine if at least one complete path can be traversed using available appointments having an acceptable cumulative phase-shift;
• until either a complete path is determined or said identified set of possible paths is exhausted;
• and if said identified set of possible paths has been exhausted without determining at least one complete path then rejecting said request;
• whereby search of said set of possible paths is constrained according to criteria derived from link utilization, network topology, and availability;
• wherein said phase-shift is a difference, measured across each switching and transmission element between communicating endpoints, in a dimension selected from one or more of:
• frequency, flow mass, time-frequency, flow type, packet type, and packet mass, and wherein said phase shift is not related to packet jitter;
• configuring said available appointment path, if one was found;
• and
• rejecting said request if said halting criteria are reached.

An apparatus for forwarding packets at precise times in a packet switching system comprised of:

• a set of connected routers;
• each router configured for precise switching using packet ingress time on a port to index entries in a forwarding table;
• said entries containing forwarding information including egress port and egress time for each scheduled packet flow;
• and wherein the router will transmit each scheduled packet on said egress port at the egress time indexed by the ingress time for said flow;
• where said forwarding table entries are populated according to a network scheduling algorithm in which phase shift between said ingress time and said egress time is limited according to predetermined criteria influenced by system utilization and tolerance for delay in said flow, wherein said phase-shift is a difference, measured across each switching and transmission element between communicating endpoints, in a dimension selected from one or more of:
• frequency, flow mass, time-frequency, flow type, packet type, and packet mass, wherein said phase shift is not related to packet jitter.