Communications protocol

• US 20060064622A1
• Filed: 10/30/2003
• Published: 03/23/2006
• Est. Priority Date: 11/13/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Moridi, Said, Fisher, Andrew J
• Granted Patent: US 7,296,207 B2
• Time in Patent Office: Days
• US Class Current: 714/758
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method of communicating datagrams between terminals (nodes) of a communications system. In systems operating over unreliable media redundancy check data (136) can be included in a datagram for use in verifying the integrity of the datagram when received (112) by a terminal; satisfactory receipt of the datagram can be confirmed by the receiving terminal issuing (128) a response datagram to the originating terminal, for example an acknowledgement. The present invention utilises the redundancy check data (116) of a received original datagram (which redundancy check data includes information on the identity of the originating terminal and the content of the datagram) in the generation (122) of new redundancy check data for the acknowledgement (or other type of response) datagram. The originating terminal receives (130) and processes (134, 138) the response datagram in conjunction with its own local record of the redundancy check data (136) of the original datagram. In this way, the present invention ensures the response datagram is compact in size whilst enabling the originating terminal not only to verify (138) the integrity of the response datagram but also to recognise (140) the response datagram as being the response to the original datagram.

Claims

1. A method of communicating datagrams between terminals of a communication system, wherein each datagram comprises redundancy check data used to verify datagram integrity, the method comprising the steps of:

generating a first datagram comprising message data and first redundancy check data, which first redundancy check data is computed in dependence on the message data;

sending the first datagram from a first terminal to a second terminal;

verifying the integrity of the first datagram;

generating a second datagram which comprises second redundancy check data, which second redundancy check data is computed in dependence on response data and first redundancy check data;

sending the second datagram from the second terminal to the first terminal;

verifying the integrity of the second datagram;

and, in the case where the integrity of the second datagram is confirmed, identifying that the second datagram is the response to the first datagram.

2. A method according to claim 1 wherein the step of verifying the integrity of the first datagram comprises the steps of:

calculating third redundancy check data in dependence on the message data;

comparing third redundancy check data with first redundancy check data; and

determining the integrity of the first datagram in dependence on the comparison.

3. A method according to claim 1 wherein the step of verifying the integrity of the second datagram comprises the steps of:

calculating fourth redundancy check data in dependence on the response data and first redundancy check data;

comparing fourth redundancy check data with second redundancy check data; and

determining the integrity of the second datagram in dependence on the comparison.

4. A method according to claim 1 wherein computing second redundancy check data comprises the steps of:

initialising a first redundancy check data generator in dependence on the first redundancy check data;

applying response data to the redundancy check data generator; and

determining second redundancy check data in dependence on the value of the first redundancy check data generator.

5. A method according to claim 1, wherein the step of verifying the integrity of the second datagram comprises the steps of:

initialising a second redundancy check data generator in dependence on the first redundancy check data;

applying response data of the second datagram and second redundancy check data to the generator, which response data was that used to compute the second redundancy check data; and

determining the integrity of the second datagram in dependence on the value of the second redundancy check data generator.

6. A method according claim 1, wherein the second datagram further comprises the response data.

7. A communications system comprising a plurality of terminals, wherein each terminal employs the method of claim 1.

9. A terminal for use in the communications system according to claim 7, the terminal comprising:

a first port operable to receive a datagram from another terminal;

a processor operable to;

decode a received datagram;

compute redundancy check data;

compare redundancy check data; and

generate a datagram;

a first store operable to store program code instructions;

a second store operable to store redundancy check data;

a second port operable to send datagrams to another terminal; and

a third port operable to exchange data with a host application.

10. A terminal according to claim 9, in which the first store is non-volatile.

11. A terminal according to claim 9, further comprising a redundancy check data generator.

8. (canceled)

12. (canceled)

13. (canceled)