Synchronised data delivery

• US 20030021231A1
• Filed: 08/30/2002
• Published: 01/30/2003
• Est. Priority Date: 03/17/2000
• Status: Active Grant

• Current Assignee: Paul A. Evans
• Original Assignee: Paul A. Evans
• Inventors: Evans, Paul A
• Granted Patent: US 7,385,933 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04L 12/1881 with schedule organisation, e.g. priority, sequence management
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 43/0835 One way packet loss
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 43/10 Active monitoring, e.g. heartbeat, ping or trace-route
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A data distribution system provides capability for synchronised delivery of data elements to each of a set of receivers. In the system, a number of forwarding computers are linked together in a predetermined configuration by a communications network. An originating forwarding computer receives a data element from a source and forwards it to one or more predetermined destination forwarding computers of the system for delivery to receivers. Each forwarding computer operates a cyclical monitoring process to measure at least one characteristic known to contribute to delay in transferring a data element between forwarding computers, calculating the maximum expected delay for each cycle. On forwarding a data element, an originating forwarding computer calculates a prescribed time for delivery to a receiver by a destination forwarding computer taking account of the maximum expected delay at that time, writing the prescribed delivery time into the data element being forwarded. The system is adaptive to varying network performance in maintaining synchronised delivery.

Claims

1. A forwarding apparatus for use in a data distribution system comprising a plurality of forwarding apparatuses, linked by a communications network, for forwarding data elements from a source of data elements to one or more receivers accessible to forwarding apparatus of the system, said forwarding apparatus having:

an input for receiving a data element to be forwarded;

timer means;

monitoring means for monitoring at least one predetermined characteristic contributive to delay in transferring a data element between forwarding apparatuses of the system and to periodically output data indicative of the contribution to delay due to each said monitored characteristic;

calculating means operable to calculate, from an output of the monitoring means, a maximum expected delay in transferring a data element from said forwarding apparatus to a destination forwarding apparatus for delivery to a receiver and thereby to calculate, at a time indicated by the timer means, a current prescribed time for delivery of the data element to a receiver by said destination forwarding apparatus; and

forwarding means operable to write into a received data element a current prescribed time for delivery as calculated by said calculating means, and to forward the received data element.

2. A forwarding apparatus according to claim 1, wherein said calculation means are operable to calculate a maximum expected delay in respect of a predetermined probability that the delay in forwarding a data element from said forwarding apparatus to a destination forwarding apparatus of the system will exceed the maximum expected delay.

3. A forwarding apparatus according to either one of the preceding claims, further provided with synchronisation means for synchronising the timing means with timing means of the destination forwarding apparatus.

4. Apparatus according to any preceding claim, comprising a computer.