Improving access to congested networks

• US 6,345,038 B1
• Filed: 05/12/1998
• Issued: 02/05/2002
• Est. Priority Date: 05/12/1998
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Selinger, Craig Richard
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): DUONG, FRANK
• Application Number:
  US09/078,140
• Time in Patent Office: 1,365 Days
• Field of Search: 370/229, 370/230, 370/231, 370/235, 370/236, 370/252, 370/253, 370/468, 370/477, 370/395, 370/395.2, 370/395.21
• US Class Current: 370/230
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/11 Identifying congestion
• CPC Class Codes: H04L 47/15 in relation to multipoint traffic arrangements for broadcast or multicast in data networks H04L12/18
• CPC Class Codes: H04L 47/2433 Allocation of priorities to traffic types
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04L 47/70 Admission control; Resource allocation
• CPC Class Codes: H04L 47/745 Reaction in network
• CPC Class Codes: H04L 47/765 triggered by the end-points
• CPC Class Codes: H04L 47/788 Autonomous allocation of resources
• CPC Class Codes: H04L 47/805 QOS or priority aware
• CPC Class Codes: H04L 47/822 Collecting or measuring resource availability data

Abstract

For a station in a data communication network having a predefined limit of congestion for handling data immediately undergoing transmission through the station, a system for improving service given to network users requesting new access services to support new transmissions through the same station while the predefined congestion limit is exceeded. This system contains: a first element for determining when the predefined limit is exceeded by existing data transmissions through the station; and a second element, responsive to requests for new access services that are received while the predefined limit is being exceeded for: concurrently processing the request for new service and reducing the quality of service (QoS) to selected users. The reductions in QoS generally have the effects of reducing the speed/priority of handling of data being transmitted to or from the selected users, and of freeing up of sufficient bandwidth to accommodate the requested new access services. The system includes a third element for restoring/upgrading QoS, to users whose QoS has been reduced, when bandwidth usage subsides to a level allowing for such restoration. This latter level is sufficiently less than the congestion limit to provide a hysteresis effect that delays actions by the third element sufficiently to prevent successive actions of said second and third elements from producing unstable fluctuations in the operation of the station. Arrangements are disclosed for applying the invention in a cable television network environment and in private network environments serving a single business enterprise such as a banking institution.

Claims

1. For a station providing network access services to multiple users of a data communication network, said station having a predefined limit of congestion for handling data concurrently undergoing transmission through said station, a system for improving access to said network for users requesting new access services when said predefined limit of congestion is exceeded due to services currently being provided at said station;

said system comprising;

a first element for producing mutually exclusive first and second indications representing states of congestion at said station in respect to data undergoing transmission through said station for users of said network currently receiving said network access services;

said first indication being activated only when said predefined limit of congestion is exceeded by said data undergoing transmission;

said second indication being activated when said data undergoing transmission is at a level less than said predefined congestion limit; and

a second element for controlling delivery of said network access services to users of said network;

said second element being responsive to said first indications and coinciding requests by users of said network for new access services for concurrently;

enabling new access services to be provided in response to said requests, and

a. causing a reduction in the rate of transmission of data currently undergoing transmission through said station;

said reduction being sufficient to enable said station to effectively handle both all of the data currently undergoing transmission through said station and data newly transferred to said station in response to acceptance of said requests;

said second element being responsive to said second indications to increase the rate of transmission of data to which said reduction in the rate of transmission has been applied; and

activation of said second indication being timed relative to deactivation of said first indication in a manner ensuring that successive reductions and increases in said rate of transmission of data occur in a manner consistent with stable and efficient operation of said station.

2. A system for improving network access in accordance with claim 1, wherein said data to which said reduction and increase are applied is data of selected current users of said station'"'"'s services;

which selected users may be less than all of the users currently receiving said services.

3. A system in accordance with claim 2 wherein said selected users of said station services are selected by said second element in accordance with predetermined criteria.

4. A system in accordance with claim 3 wherein said predetermined criteria are based on Quality of Service (QoS) normally allocated to and expected by respective selected users when said predefined congestion limit is not currently exceeded.

5. For a station providing network access services to multiple users of a data communication network, said station having a predefined limit of congestion for handling data concurrently undergoing transmission through said station, a system for improving access to said network for users requesting new access services when said predefined limit of congestion is exceeded due to services currently being provided at said station;

said system comprising;

a first element for producing mutually exclusive first and second indications representing states of congestion at said station in respect to data undergoing transmission through said station for users of said network currently receiving said network access services;

said first indication being activated only when said predefined limit of congestion is exceeded by said data undergoing transmission;

said second indication being activated when the rate of handling of said data undergoing transmission is at a level less than a rate associated with said predefined limit of congestion; and

a second element for controlling delivery of said network access services to users of said network;

said second element being responsive to said first indications and coinciding requests by users of said network for new access services for concurrently;

b. enabling new access services to be provided in response to said requests, and

c. causing a reduction in the rate of transmission of data currently undergoing transmission through said station;

said reduction being sufficient to enable said station to effectively handle both all of the data currently undergoing transmission through said station and data newly transferred to said station in response to acceptance of said requests;

said second element being responsive to said second indications to increase the rate of transmission of data to which said reduction in the rate of transmission had previously been applied;

activation of said second indication being effectively timed relative to deactivation of said first indication in a manner ensuring stable operation of said station; and

wherein said station has a predefined restoration limit different from said predefined congestion limit, said predefined restoration limit being used to control activation of said second indication and being associated with a level of data traffic that is discretely less than the level of data traffic associated with said predefined congestion limit, and wherein said first and second indications are respectively activated only when the rate of handling of said data undergoing transmission is respectively greater than the rate of data handling associated with said predefined congestion limit and less than a predetermined rate associated with said predefined restoration limit;

the difference between said predefined congestion and restoration limits being sufficient to produce a hysteresis effect ensuring that successive decreases and increases in rates of transmission of said data currently undergoing transmission are consistent with stable and efficient operation of said station.

6. A system for improving network access in accordance with claim 5, wherein said network includes a cable television distribution network, said station is located at a head end control center of said cable television network, and said users of access services at said station are users of said cable television network having cable modems that are linked directly to said head end control centers for transmitting data to and from said station in synchronism with variations in rates of data transmission applied by said second element to data transmitted for respective said users.

7. A system for improving access to a cable network in accordance with claim 6 wherein:

said station at said head end control center is adapted to provide said directly linked cable modems of said users with signals indicating variations in data transfer rate applied to data currently being transmitted for respective users; and

said cable modems of said respective users are adapted to respond to said signals indicating rate variations to synchronize to revised rates of transmission indicated by said signals.

8. A system in accordance with claim 7 wherein said data currently undergoing transmission is transmitted through routes extending through stations remote from said head end center, and said user cable modems have associated therewith means enabling respective modems to provide respective remote stations with signals indicating said variations in data transfer rate when said signals indicating variations in data transfer rate are provided to respective user modems by said station at said head end center;

said signals provided to said remote stations enabling said remote stations to synchronize to respective revised rates of transmission of data being sent by respective users.

9. A system in accordance with claim 5 wherein said station is part of a private network serving a business enterprise.

10. A system in accordance with claim 9 wherein said private network includes a virtual private network embedded within a public network.

11. A system in accordance with claim 10 wherein said public network is the Internet.

12. For a station providing network access services to multiple users of a data communication network, said station having a predefined limit of congestion for handling data concurrently undergoing transmission through said station, a method of improving access to said network for users requiring new access services when said congestion limit is exceeded due to services currently being provided at said station;

said method comprising;

producing mutually exclusive first and second indications representing states of said station in respect to data currently undergoing transmission through said station;

said first indication being produced only when said predefined limit of congestion is exceeded by said data currently undergoing transmission, and said second indication being produced only when said data currently undergoing transmission is at a level discretely below said predefined congestion limit; and

allowing for new access services to be provided to said users, while said congestion limit is exceeded by the level of said data currently undergoing transmission, by;

a. reducing the rate of transmission handling of a selected portion of said data currently undergoing transmission when said first indication is produced; and

b. increasing the rate of transmission handling of said selected portion of data currently undergoing transmission when said second indication is produced following a deactivation of said first indication;

wherein activation of said second indication is effectively timed relative to deactivation of said first indication in a manner ensuring stable operation of said station.

13. A method of improving network access in accordance with claim 12 comprising:

selecting, as said portion of data, data currently being transmitted by selected users of said station.

14. A method in accordance with claim 13, wherein users of said station are normally guaranteed various different levels of quality of service (QoS) when said first indication is not produced, wherein said selected users are chosen as a function of their respective normally guaranteed levels of QoS, and wherein said step of reducing the rate of transmission handling effectively reduces QoS levels currently being provided to said selected users.

15. For a station providing network access services to multiple users of a data communication network, said station having a predefined limit of congestion for handling data concurrently undergoing transmission through said station, a method of improving access to said network for users requiring new access services when said congestion limit is exceeded due to services currently being provided at said station;

said method comprising;

producing mutually exclusive first and second indications representing states of said station in respect to data currently undergoing transmission through said station;

said first indication being produced only when said predefined limit of congestion is exceeded by said data currently undergoing transmission, and said second indication being produced only when said data currently undergoing transmission is at a level discretely below said predefined limit of congestion; and

allowing for new access services to be provided to said users, while said congestion limit is exceeded by the level of said data currently undergoing transmission, by;

c. reducing the rate of handling of at least a portion of said data currently undergoing transmission when said first indication is produced; and

d. increasing the rate of transmission of said portion of data currently undergoing transmission when said second indication is produced;

wherein activation of said second indication is effectively timed relative to deactivation of said first indication in a manner ensuring stable operation of said station; and

wherein said station is adapted to interact with said selected users to maintain synchronism between said selected users and said station when said rates of transmission are reduced and increased.

16. A method in accordance with claim 15 wherein said data currently undergoing transmission is routed through other stations remote from said station, and said station is adapted to maintain synchronism between said selected users and said other remote stations when said rates of transmission are reduced and increased.

17. A method in accordance with claim 16 wherein said station is located at a head end center of a cable television network supplying television signals to users of said station.

18. A method in accordance with claim 15 wherein said station is located at a transmission distribution node of a private network serving a business enterprise, and said station is maintained by said enterprise.