Method for transmitting high-priority packets in an IP transmission network

• US 7,558,269 B2
• Filed: 08/11/2003
• Issued: 07/07/2009
• Est. Priority Date: 02/24/2003
• Status: Active Grant

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Le Pennec, Jean-Francois, Galand, Claude, Giroir, Didier F.
• Primary Examiner(s): Rao; Seema S
• Assistant Examiner(s): Wong; Xavier
• Application Number:
  US10/638,898
• Publication Number:
  US 20050175013A1
• Time in Patent Office: 2,157 Days
• Field of Search: 370/395.42, 370/395.4, 370/389, 370/395.1, 370/395.41
• US Class Current: 370/395.42
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2408 for supporting different services, e.g. a differentiated services [DiffServ] type of service
• CPC Class Codes: H04L 47/2416 Real-time traffic
• CPC Class Codes: H04L 47/245 using preemption

Abstract

Method for transmitting high-priority packets in an IP transmission network based upon the Internet Protocol (IP) wherein low-priority packets or fragments of packets are transmitted between a sender and a receiver and at least a high-priority packet can be transmitted from the sender to the receiver by pre-emption of a low-priority packet or a fragment of packet. the method comprises in the sender, the steps of determining whether a low-priority packet or fragment of packet is being transmitted from the sender to the receiver when a high-priority packet has to be transmitted, setting to 1 a reserved bit within the IP header of the high-priority packet used as a pre-emption indicator if a low-priority packet or fragment of packet is currently transmitted, transmitting the high-priority packet with the pre-emption indicator set to 1 from the sender to the receiver, and resuming the transmission of the low-priority packet or fragment of packet at the end of transmission of the high-priority packet.

Claims

1. A method performed by a packet transmitter for transmitting high priority packets in an Internet Protocol (IP) based transmission network wherein low-priority packets or fragments of packets are transmitted between a transmitter and a receiver and wherein high priority packets pre-empt low-priority packets, the method comprising the steps, performed by the transmitter, of:

determining whether a low-priority packet or a fragment of a low-priority packet is being transmitted from the transmitter to the receiver when a high-priority packet requires transmission;

activating a reserved bit within the IP header of the high-priority packet, as a pre-emption indicator, and suspending transmission of said low-priority packet or fragment of a low-priority packet, in the event that a low-priority packet or a fragment of a low-priority packet is being transmitted;

transmitting the high-priority packet having the pre-emption indicator activated; and

restarting the transmission of the low-priority packet or the fragment of the low-priority packet after having transmitted the high-priority packet,

wherein the reserved bit is within the IP header as a packet start indicator in each low-priority packet or fragment,

wherein the reserved bit used as a packet start indicator is set to a first binary value in a first segment of a low-priority packet or fragment being transmitted, the reserved bit being reset to a second binary value when a high-priority packet requires transmission and a low-priority packet or fragment is pre-empted,

and wherein the reserved bit is within the flag field within the IP header of a packet.

2. The method of claim 1, wherein the pre-emption indicator is not activated in the event that no low-priority packet or fragment is being transmitted when the high-priority packet is transmitted.

3. The method of claim 1 further comprising the step of transmitting a sweep packet when no high-priority packet requires transmission after a low-priority packet or fragment has been transmitted, the sweep packet being a packet without data indicating that the previous transmission of a low-priority packet or fragment has been completed.

4. A method performed by a receiver that receives high priority packets from an Internet Protocol (IP) based transmission network, wherein low-priority packets or fragments of packets are transmitted between a transmitter and the receiver, wherein high priority packets pre-empt low-priority packets and wherein each of the packets includes an header that includes at least a Flags field and a Type-of-Service field that is different from said Flags field, the method comprising the steps, performed by the receiver, of:

determining whether a high-priority packet has been received by the receiver;

determining whether a reserved bit within the IP header of the high-priority packet has been activated, the reserved bit being a bit within said Flags field within the IP header of the packet;

waiting for reception of a new packet if the reserved bit has been activated, the activated reserve bit indicating that the high-priority packet has pre-empted a low-priority packet; and

determining whether the reserved bit used as a packet start indicator has been activated when the packet being received by the receiver is a low-priority packet or fragment, the low-priority packet or fragment being a segment to be appended to the received low-priority packet or fragment if the packet start indicator is inactive.

5. The method according to claim 4, wherein a previously received low-priority packet or fragment is delivered to the upper layer when the reserved bit used as a pre-emption indicator has been activated in the high-priority packet, and wherein an inactivated pre-emption indicator indicates that the transmission of the previously received low-priority packet or fragment has been completed.

6. The method of claim 5, wherein the received low-priority packet or fragment is delivered to the upper layer when the reserved bit used as a packet start indicator is active, indicating that the reception of the previously received low-priority packet or fragment has been completed.

7. The method of claim 6, further comprising the step of determining whether the packet being received is a sweep packet without data, the sweep packet indicating that the transmission of a low-priority packet or fragment has been completed.

8. The method of claim 7, wherein the step of determining whether the packet being received is a low-priority packet or a high-priority packet is determined by said Type-of-Service field within the IP header of the received packet.

9. The method of claim 8, wherein the high-priority packet is a voice packet and the low-priority packet or fragment is a data packet or fragment.