In-Band Quality-of-Service Signaling to Endpoints that Enforce Traffic Policies at Traffic Sources Using Policy Messages Piggybacked onto DiffServ Bits

• US 20080144502A1
• Filed: 12/19/2006
• Published: 06/19/2008
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Deterministic Networks, Inc. (Gilat Satellite Networks Limited)
• Inventors: Keith, Seith K., Jackowski, Steven J.
• Granted Patent: US 7,983,170 B2
• Time in Patent Office: Days
• US Class Current: 370/235
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/12 Avoiding congestion; Recovering from congestion
• CPC Class Codes: H04L 47/26 using explicit feedback to the source, e.g. choke packets
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 47/35 by embedding flow control information in regular packets, e.g. piggybacking
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
• CPC Class Codes: H04L 69/167 Adaptation for transition between two IP versions, e.g. between IPv4 and IPv6 translation of Internet protocol [IP] addresses H04L61/2503
• CPC Class Codes: H04W 28/0289 Congestion control load shedding arrangements in network planning H04W16/08; performing reselection for handling the traffic H04W36/22; wireless traffic scheduling H04W72/12
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

IP packets are scheduled at source devices such as cell phones on a private network that connect to the Internet at an edge device. A private traffic controller by the edge device detects pre-Internet congestion on the private network. The private traffic controller uses in-band piggybacked signaling of policy changes by intercepting return packets to the source devices and modifying bits such as DSCP bits in the header. Source traffic controllers in the source devices read the modified DSCP bits and implement specified policy changes, dropping or delaying packets at the source device before transmission. Congestion on RF links from cell phones is reduced by the source traffic controllers dropping packets before transmission. The source device limits or drops future packets in response to the policies signaled by the DSCP bits. Rather than indicate the existing packet'"'"'s priority, private DSCP bits signal policy changes to the source device.

Claims

1. A source-traffic control system comprising:

a central traffic controller that comprises;

a network-status receiver that receives a network status from a network monitor;

a policy activator, responsive to the network status from the network-status receiver, for generating a policy-change message that indicates a policy change;

an encoder, activated by the policy activator, for generating a coded message from the policy-change message;

a return packet modifier, coupled to intercept a return packet to a source device, the return packet modifier writing the coded message from the encoder into the return packet to generate a modified return packet to the source device;

a plurality of source traffic controllers on a plurality of source devices, wherein a source traffic controller on the source device comprises;

a source network receiver that receives the modified return packet;

a source signaling protocol module that reads and decodes the coded message from the modified return packet;

a source policy agent that implements the policy change indicated by the policy-change message encoded by the coded message and decoded by the source signaling protocol module; and

a source packet filter, on the source device, that prevents transmission of packets from the source device in response to the policy change when the policy change indicates a reduction in transmission bandwidth available to the source device;

whereby transmission bandwidth is reduced by in-band signaling of the policy change sent to the source traffic controller in the modified return packet.

2. The source-traffic control system of claim 1 wherein the network-status receiver

receives the network status from the network monitor for a private network that is separate from and connected to an Internet,

whereby pre-Internet network status is monitored and controlled.

3. The source-traffic control system of claim 2 wherein the private network comprises private links between the plurality of source devices and an edge device;

wherein the network status indicates congestion or increased latency on the private links;

wherein the central traffic controller generates the policy-change message to adjust a status of the private links using the source devices,

whereby the network status indicates the status of the private links.

4. The source-traffic control system of claim 3 wherein the private network is connected to the Internet by the edge device;

wherein the central traffic controller is coupled to the edge device;

wherein the return packet modifier intercepts return packets from a server on the Internet to the source device after the return packets pass through the edge device,

whereby the return packets are intercepted by the edge device.

5. The source-traffic control system of claim 4 wherein the central traffic controller further comprises:

the network monitor that generates the network status that is sent to the network-status receiver;

wherein the network monitor and the central traffic controller are coupled to the edge device and are separated from the source devices by the private links.

6. The source-traffic control system of claim 3 wherein the private network comprises a wireless network;

wherein the private links comprise radio-frequency (RF) links and the source devices comprise wireless devices,

wherein the source packet filter prevents transmission of packets over the RF links in response to the policy change when the policy change indicates a reduction in transmission bandwidth available to the source device;

whereby the source traffic controllers are installed on the wireless devices.

7. The source-traffic control system of claim 6 wherein the wireless devices comprise cell phones that generate Internet Protocol (IP) packets that are transmitted over the RF links and filtered by the source packet filter on the cell phones in response to the policy change.

8. The source-traffic control system of claim 3 wherein the return packet is an Internet Protocol (IP) packet;

wherein the coded message is encoded into differentiated-services code-point (DSCP) bits in a header of the return packet.

9. The source-traffic control system of claim 8 wherein the coded message is encoded using undefined or unused encodings of the DSCP bits, the undefined or unused encodings not being

wherein the DSCP bits are used by a Differentiated Services protocol that signals a priority of the return packet to a Quality-of-Service (QoS) router;

wherein the return packet modifier alters the DSCP bits to signal the policy change to the source traffic controller;

wherein the return packets do not increase in size when the DSCP bits are encoded to signal the policy change,

whereby the DSCP bits are used for in-band and piggybacked signaling of policy changes to source devices.

10. The source-traffic control system of claim 3 wherein the central traffic controller further comprises:

a sequencer for sending the policy-change message to the source traffic controller as a plurality of coded messages in a plurality of return packets,

whereby the policy-change message is sent using a sequence of return packets.

11. The source-traffic control system of claim 10 wherein the central traffic controller further comprises:

an acknowledgement receiver that detects an acknowledgement message from the source traffic controller in a request packet generated by the source device;

wherein the acknowledgement message acknowledges receipt of the policy-change message by the source traffic controller.

12. The source-traffic control system of claim 3 wherein the return packet further comprises server data generated by a server on the Internet in response to a request packet generated by the source device.

13. A computer-implemented method for controlling packet traffic on a private network that is connected to an Internet at an edge device comprising:

routing a request packet generated by a source device and transmitted over the private network through the edge device toward a server on the Internet;

receiving a return packet generated by the server in response to the request packet;

modifying header bits in the return packet to generate a modified return packet that contains a policy message in the header bits;

routing the modified return packet over the private network to the source device;

receiving the modified return packet at the source device and reading the header bits to extract the policy message as a received policy message;

adjusting a traffic policy on the source device in response to the received policy message;

wherein adjusting the traffic policy comprises;

dropping outbound packets generated by the source device and not transmitting the outbound packets over the private network when the received policy message indicates a policy of blocking all outbound packets from the source device;

comparing outbound packets generated by the source device to a criteria and dropping or delaying outbound packets that match the criteria, wherein the criteria is indicated by the received policy message when the received policy message indicates a policy of selective-criteria blocking some outbound packets from the source device; and

transmitting all outbound packets generated by the source device over the private network when the received policy message indicates a policy of allowing all outbound packets from the source device;

whereby packets are dropped or delayed at the source device in response to piggybacked signaling in the header bits of the modified return packet.

14. The computer-implemented method of claim 13 wherein transmitting all outbound packets comprises transmitting packets over a radio-frequency link between the source device and a base station connected to the edge device,

wherein dropping outbound packets comprises not transmitting packets over the radio-frequency link between the source device and the base station connected to the edge device,

whereby packets are dropped by source devices before transmission over radio-frequency links.

15. The computer-implemented method of claim 14 further comprising:

monitoring the private network for congestion;

generating the policy message in response to a change in congestion on the private network,

whereby the policy message is generated in response to congestion on the private network.

16. The computer-implemented method of claim 13 wherein modifying header bits in the return packet to generate the modified return packet comprises modifying Differentiated Services Code Point (DSCP) bits in an Internet Protocol (IP) header for the return packet.

17. A computer-program product comprising:

a computer-usable medium having computer-readable program code means embodied therein for controlling traffic on private links, the computer-readable program code means in the computer-program product comprising;

private traffic monitor means for monitoring status of a private network that includes the private links to source devices;

private traffic controller means, responsive to status from the private traffic monitor means, for adjusting traffic policies of source devices that are connected to the private links;

return packet interceptor means for intercepting a return packet to a source device generated by a server on a public network in response to a request packet generated by the source device;

return packet modifier means for modifying the return packet to generate a modified return packet that contains a policy message from the private traffic controller means;

wherein the policy message causes the source device to implement a traffic-controlling policy by;

dropping outbound packets generated by the source device and not transmitting the outbound packets over the private network when the policy message indicates a policy of blocking all outbound packets from the source device;

comparing outbound packets generated by the source device to a criteria and dropping or delaying outbound packets that match the criteria, wherein the criteria is indicated by the policy message when the policy message indicates a policy of selective-criteria blocking some outbound packets from the source device; and

transmitting all outbound packets generated by the source device over the private network when the policy message indicates a policy of allowing all outbound packets from the source device;

whereby packets are dropped or delayed at the source device in response to in-band signaling in the modified return packet.

18. The computer-program product of claim 17 wherein the computer-readable program code means further comprises:

source traffic controller means, operating on the source device, for extracting the policy message from the modified return packet received by the source device, and for implementing the traffic-controlling policy,

whereby the source traffic controller means is signaled by the private traffic controller means with the policy message in the modified return packet.

19. The computer-program product of claim 18 wherein the source traffic controller means further comprises:

first filter means for dropping outbound packets generated by the source device and not transmitting the outbound packets over the private network when the policy message indicates a policy of blocking all outbound packets from the source device;

compare means for comparing outbound packets generated by the source device to a criteria and for dropping or delaying outbound packets that match the criteria, wherein the criteria is indicated by the policy message when the policy message indicates a policy of selective-criteria blocking some outbound packets from the source device; and

passing means for transmitting all outbound packets generated by the source device over the private network when the policy message indicates a policy of allowing all outbound packets from the source device;

whereby packets are dropped or delayed at the source device in response to in-band signaling in the modified return packet.

20. The computer-program product of claim 18 wherein the return packet modifier means further comprises:

Differentiated Services Code Point (DSCP) writer means for writing an encoded policy message to DSCP bits in a header of the return packet to generate the modified return packet; and

policy encoder means for generating the encoded policy message from the policy message.