Method for achieving high-availability of itineraries in a real-time network scheduled packet routing system
First Claim
1. A method for scheduling real time data across a network comprising the steps of:
- collecting information about network topology including path information and appointment information;
using said path information to identify a set of possible paths across a network to satisfy a connection request;
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, 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;
until either a complete path is determined or said identified set of possible paths is exhausted;
publishing an itinerary to each path element if said at least one complete path has been determined;
orrejecting said connection request if said identified set of possible paths has been exhausted without determining at least one complete path.
18 Assignments
0 Petitions
Accused Products
Abstract
A system using scheduled times for transmission at each link guarantees bandwidth for transmitting data across a packet network. A scheduling agent determines availability of data paths across a network according to pre-selected criteria and real-time network topology information. Precise schedules are determined for transmission and reception appointments for data packets to traverse each link and switch in the network including compensation for transmission delays and switch latencies, resulting in a fixed packet flow itinerary for each connection. Itineraries are communicated to schedule-aware switches and endpoints and appointment times are reserved for transmission of the scheduled data packets. Scheduled packets arriving at each switch are forwarded according to their predetermined arrival and departure schedules, rather than their headers or contents, relieving the switches from making real-time routing decisions. Any unscheduled transmission times remain available for routing of unscheduled packets according to their IP headers. Real-time transmission of data can be guaranteed in each scheduled path, and schedule selection criteria may be adjusted according to network utilization and tolerable setup delay and end-to-end delay.
-
Citations
16 Claims
-
1. A method for scheduling real time data across a network comprising the steps of:
-
collecting information about network topology including path information and appointment information; using said path information to identify a set of possible paths across a network to satisfy a connection request; 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, 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;until either a complete path is determined or said identified set of possible paths is exhausted; publishing an itinerary to each path element if said at least one complete path has been determined;
orrejecting said connection request if said identified set of possible paths has been exhausted without determining at least one complete path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. 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. - View Dependent Claims (11)
-
-
12. 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. - View Dependent Claims (13, 14, 15, 16)
-
Specification