Constant bit rate transport in a contention based medium access control

Abstract

In a two way cable system that includes a controller and a plurality of user terminals, a method of granting rights for upstream data transmission from the user terminals includes processing contention requests to generate contention grants and maintaining a list of connections, each connection having specified therefor a predetermined bit rate. The controller sends a downstream data stream to the user terminals and receives an upstream data stream from the user terminals. The downstream data stream includes a plurality of grant fields, and the upstream data stream includes upstream data slots and upstream control slots. The method further includes scheduling preemptive grants for upstream data slots using selected fields of the plurality of grant fields so as to provide preemptive grants for upstream data transport at a bit rate specified for each connection, sending to the user terminals a data transmission grant in a grant field of the plurality of grant fields for which a preemptive grant is scheduled, and sending to the user terminals a data transmission grant in a grant field of the plurality of grant fields in which a contention grant is pending and no preemptive grant is scheduled.

What is claimed is:  
     
       1. A method employed in a two way communications system comprising a controller and a plurality of user terminals, the two way communications system capable of carrying information flows and bursts of data of the plurality of user terminals, the controller transmitting downstream information to the plurality of user terminals on at least one downstream channel, the plurality of user terminals transmitting upstream information to the controller on at least one shared upstream channel of a shared communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, at least one media access control mechanism being used to resolve contention for transmission on the at least one shared upstream channel, an upstream information transmission of at least one first user terminal of the plurality of user terminals capable of colliding on the at least one shared upstream channel with an upstream information transmission of at least one second user terminal of the plurality of user terminals, the method comprising the steps of:
 processing a reservation request that solicits a first grant of at least one first upstream time slot to carry a requested burst of data, the requested burst of data having a requested burst size of finite amount; 
 maintaining a list of at least one information flow, the list of at least one information flow being associated with at least one service parameter; 
 scheduling a second grant of at least one second upstream time slot, the scheduling being based at least upon a first entry in the list of the at least one information flow and the at least one service parameter, the second grant being scheduled to provide a first information flow with a quality of service indicated by the at least one service parameter, the first information flow being associated with the first entry in the list of at least one information flow; 
 sending notice of the first grant to the plurality of user terminals responsive to the reservation request that solicits the first grant, the notice of the first grant indicating an allocation of the at least one first upstream time slot to carry a granted burst of data, the granted burst of data having a granted burst size and comprising a finite amount of data; and 
 sending notice of the second grant to the plurality of user terminals responsive to the scheduling of the second grant, the notice of the second grant indicating an allocation of the at least one second upstream time slot to carry data that is at least part of the first information flow. 
 
     
     
       2. The method of  claim 1 , wherein the at least one second upstream time slot is allocated to meet a specified bit rate. 
     
     
       3. The method of  claim 1 , wherein the at least one first upstream time slot is not allocated to any information flow associated with at least one entry in the list of at least one information flow and is utilized to carry data that is independent from data carried by each information flow associated with at least one entry in the list of at least one information flow. 
     
     
       4. The method of  claim 1 , wherein maintaining the list of at least one information flow further comprises the steps of:
 monitoring at least one message that carries information flow signaling; and 
 modifying the list of at least one information flow responsive to the at least one message that carries information flow signaling. 
 
     
     
       5. The method of  claim 4 , wherein the at least one message that carries information flow signaling comprises at least one information element that signals the at least one service parameter. 
     
     
       6. The method of  claim 4 , wherein the at least one message that carries information flow signaling is communicated using at least one protocol selected from the group consisting of: Q.2931, Q.931, Q.932, and Q.933. 
     
     
       7. The method of  claim 4 , wherein the modifying step further comprises the steps of:
 creating the first entry in the list of at least one information flow responsive to establishment of the first information flow, the establishment signaled by the at least one message that carries information flow signaling; and 
 deleting the first entry in the list of at least one information flow responsive to termination of the first information flow, the termination signaled by the at least one message that carries information flow signaling. 
 
     
     
       8. The method of  claim 4 , wherein the at least one message that carries information flow signaling is communicated upstream from the plurality of user terminals to the controller by being carried in the upstream time slots. 
     
     
       9. The method of  claim 4 , wherein the upstream time slots comprise a first type of upstream time slots and a second type of upstream time slots, the first type of upstream time slots limited to carrying reservation requests, and the second type of upstream time slots capable of carrying data that is not limited to reservation requests. 
     
     
       10. The method of  claim 9 , wherein the controller dynamically varies how many of the first type of upstream time slots exist relative to how many of the second type of upstream time slots exist in a specified amount of time. 
     
     
       11. The method of  claim 9 , wherein the first type of upstream time slots are upstream control mini-slots. 
     
     
       12. The method of  claim 9 , wherein the second type of upstream time slots are upstream data slots. 
     
     
       13. The method of  claim 12 , wherein the at least one message that carries information flow signaling is communicated upstream from the plurality of user terminals to the controller by being carried in upstream data slots. 
     
     
       14. The method of  claim 4 , wherein the list of at least one information flow comprises a list of at least one committed connection. 
     
     
       15. The method of  claim 9 , wherein the at least one first user terminal generates a first reservation request transmission in at least one third upstream time slot, wherein the at least one second user terminal generates a second reservation request transmission in the at least one third upstream time slot, and wherein the first reservation request transmission of the at least one first user terminal has a reservation request collision with the second reservation request transmission of the at least one second user terminal. 
     
     
       16. The method of  claim 15 , wherein the at least one first user terminal and the at least one second user terminal perform a contention resolution. 
     
     
       17. The method of  claim 15 , wherein the at least one third upstream time slot is of the first type of upstream time slots. 
     
     
       18. The method of  claim 15 , wherein the reservation request and the first grant are at least part of a reservation mode media access control (MAC) mechanism. 
     
     
       19. The method of  claim 15 , wherein the granted burst size is less than the requested burst size. 
     
     
       20. The method of  claim 15 , wherein the at least one first user terminal generates a first upstream data transmission in at least one fourth upstream time slot, wherein the at least one second user terminal generates a second upstream data transmission in the at least one fourth upstream time slot, and wherein the first upstream data transmission of the at least one first user terminal has a data collision with the second upstream data transmission of the at least one second user terminal. 
     
     
       21. The method of  claim 20 , wherein the at least one fourth upstream time slot is of the second type of upstream time slots. 
     
     
       22. The method of  claim 20 , wherein the second type of upstream time slots are upstream data slots. 
     
     
       23. The method of  claim 20 , wherein the data collision of the first upstream data transmission with the second upstream data transmission results from the at least one first user terminal and the least one second user terminal contending for the fourth upstream time slot as at least part of an immediate mode media access control (MAC) mechanism. 
     
     
       24. The method of  claim 23 , wherein the immediate mode media access control (MAC) mechanism allows at least two user terminals of the plurality of user terminals to attempt to transmit in an upstream data time slot. 
     
     
       25. The method of  claim 15 , wherein the quality of service indicated by the at least one service parameter is used to implement at least one class of service. 
     
     
       26. The method of  claim 25 , wherein the at least one class of service is at least one selection from the group consisting of constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       27. The method of  claim 15 , wherein the two way communications system is a cable system. 
     
     
       28. The method of  claim 1 , wherein the first information flow occurs from a committed connection. 
     
     
       29. The method of  claim 1 , wherein the shared communications medium is at least part of a cable television (CATV) networking environment. 
     
     
       30. The method of  claim 1 , wherein the shared communications medium is at least part of a local area network (LAN). 
     
     
       31. The method of  claim 1 , wherein at least one of the plurality of user terminals is a cable modem. 
     
     
       32. The method of  claim 1 , wherein the quality of service indicated by the at least one service parameter is used to implement at least one class of service. 
     
     
       33. The method of  claim 32 , wherein the at least one class of service is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       34. The method of  claim 32 , wherein the at least one class of service is defined by the ATM Forum (Asynchronous Transfer Mode Forum). 
     
     
       35. The method of  claim 1 , wherein the at least one service parameter comprises at least one bit rate. 
     
     
       36. The method of  claim 1 , wherein the at least one service parameter comprises at least one jitter requirement. 
     
     
       37. The method of  claim 1 , wherein the at least one service parameter comprises at least one transit delay requirement. 
     
     
       38. The method of  claim 1 , wherein the two way communications system is a cable system. 
     
     
       39. The method of  claim 1 , wherein the controller is a head-end device. 
     
     
       40. The method of  claim 1 , wherein the upstream time slots comprise a first type of upstream time slots and a second type of upstream time slots, the first type of upstream time slots limited to carrying reservation requests, and the second type of upstream time slots capable of carrying data that is not limited to reservation requests. 
     
     
       41. The method of  claim 40 , wherein the controller dynamically varies how many of the first type of upstream time slots exist relative to how many of the second type of upstream time slots exist in a specified amount of time. 
     
     
       42. The method of  claim 40 , wherein the first type of upstream time slots are upstream control mini-slots. 
     
     
       43. The method of  claim 40 , wherein the second type of upstream time slots are upstream data slots. 
     
     
       44. The method of  claim 40 , wherein the at least one first user terminal generates a first reservation request transmission in at least one third upstream time slot, wherein the at least one second user terminal generates a second reservation request transmission in the at least one third upstream time slot, and wherein the first reservation request transmission of the at least one first user terminal has a reservation request collision with the second reservation request transmission of the at least one second user terminal. 
     
     
       45. The method of  claim 44 , wherein the at least one first user terminal and the at least one second user terminal perform a contention resolution. 
     
     
       46. The method of  claim 44 , wherein the at least one third upstream time slot is of the first type of upstream time slots. 
     
     
       47. The method of  claim 44 , wherein the reservation request and the first grant are at least part of a reservation mode media access control (MAC) mechanism. 
     
     
       48. The method of  claim 40 , wherein the at least one first user terminal generates a first upstream data transmission in at least one fourth upstream time slot, wherein the at least one second user terminal generates a second upstream data transmission in the at least one fourth upstream time slot, and wherein the first upstream data transmission of the at least one first user terminal has a data collision with the second upstream data transmission of the at least one second user terminal. 
     
     
       49. The method of  claim 48 , wherein the at least one fourth upstream time slot is of the second type of upstream time slots. 
     
     
       50. The method of  claim 48 , wherein the data collision of the first upstream data transmission with second upstream data transmission results from the at least one first user terminal and the least one second user terminal contending for the first upstream time slot as at least part of an immediate mode media access control (MAC) mechanism. 
     
     
       51. The method of  claim 50 , wherein the immediate mode media access control (MAC) mechanism allows at least two user terminals of the plurality of user terminals to attempt to transmit in an upstream data time slot. 
     
     
       52. The method of  claim 1 , wherein the granted burst size is less than the requested burst size. 
     
     
       53. The method of  claim 1 , wherein the notice of the first grant comprises a first identifier associated with at least one user terminal of the plurality of user terminals. 
     
     
       54. The method of  claim 53 , wherein the first identifier is a user terminal identifier. 
     
     
       55. The method of  claim 53 , wherein the requested burst size represents a requested number of the upstream time slots and wherein the granted burst size represents a granted number of the upstream time slots. 
     
     
       56. The method of  claim 55 , wherein the notice of the first grant further comprises an indication of a starting upstream time slot for transmission and an indication of the granted number of the upstream time slots that are allocated in the first grant. 
     
     
       57. The method of  claim 55 , wherein the granted number of the upstream time slots is less than the requested number of the upstream time slots. 
     
     
       58. The method of  claim 1 , wherein the notice of the second grant comprises a second identifier associated with at least one user terminal of the plurality of user terminals. 
     
     
       59. The method of  claim 58 , wherein the second identifier is a connection identifier. 
     
     
       60. The method of  claim 58 , wherein the notice of the second grant further comprises an indication of a starting upstream time slot for transmission and an indication of a number of the upstream time slots that are allocated in the second grant. 
     
     
       61. The method of  claim 1 , wherein the first information flow is associated with a third identifier. 
     
     
       62. The method of  claim 61 , wherein the third identifier is a connection reference. 
     
     
       63. The method of  claim 1 , wherein the reservation request comprises a first identifier associated with at least one user terminal of the plurality of user terminals. 
     
     
       64. The method of  claim 63 , wherein the first identifier is a user terminal identifier. 
     
     
       65. The method of  claim 1 , wherein a single user terminal of the plurality of user terminals generates a first upstream data transmission as at least part of the first information flow, wherein the single user terminal generates a second upstream data transmission as at least part of at least one second information flow, the at least one second information flow being associated with a second entry in the list of at least one information flow, the first information flow and the at least one second information flow both being active and multiplexed over the shared communications medium. 
     
     
       66. The method of  claim 65 , wherein the first information flow provides a first class of service and the at least one second information flow provides a second class of service. 
     
     
       67. The method of  claim 66 , wherein the first class of service and the second class of service are each at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       68. The method of  claim 66 , wherein the first class of service is different from the second class of service. 
     
     
       69. A controller in a two way communications system comprising the controller and a plurality of user terminals, the two way communications system capable of carrying information flows and bursts of data of the plurality of user terminals, the controller transmitting downstream information to the plurality of user terminals on at least one downstream channel, the plurality of user terminals transmitting upstream information to the controller on at least one shared upstream channel of a shared communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, at least one media access control mechanism being used to resolve contention for transmission on the at least one shared upstream channel, an upstream information transmission of at least one first user terminal of the plurality of user terminals capable of colliding on the at least one shared upstream channel with an upstream information transmission of at least one second user terminal of the plurality of user terminals, the controller comprising:
 logic configured to process a reservation request that solicits a first grant of at least one first upstream time slot to carry a requested burst of data, the requested burst of data having a requested burst size of finite amount; 
 logic configured to maintain a list of at least one information flow, the list of at least one information flow being associated with at least one service parameter; 
 logic configured to schedule a second grant of at least one second upstream time slot, the scheduling being based at least upon a first entry in the list of the at least one information flow and the at least one service parameter, the second grant being scheduled to provide a first information flow with a quality of service indicated by the at least one service parameter, the first information flow being associated with the first entry in the list of at least one information flow; 
 logic configured to sending send notice of the first grant to the plurality of user terminals responsive to the reservation request that solicits the first grant, the notice of the first grant indicating an allocation of the at least one first upstream time slot to carry a granted burst of data, the granted burst of data having a granted burst size and comprising a finite amount of data; and 
 logic configured to sending send notice of the second grant to the plurality of user terminals responsive to the scheduling of the second grant, the notice of the second grant indicating an allocation of the at least one second upstream time slot to carry data that is at least part of the first information flow. 
 
     
     
       70. The controller of  claim 69 , wherein the at least one second upstream time slot is allocated to meet a specified bit rate. 
     
     
       71. The controller of  claim 69 , wherein the at least one first upstream time slot is not allocated to any information flow associated with at least one entry in the list of at least one information flow and is utilized to carry data that is independent from data carried by each information flow associated with at least one entry in the list of at least one information flow. 
     
     
       72. The controller of  claim 69 , wherein the logic configured to maintain the list further comprises:
 logic configured to monitor at least one message that carries information flow signaling; and 
 logic configured to modify the list of at least one information flow responsive to the at least one message that carries information flow signaling. 
 
     
     
       73. The controller of  claim 72 , wherein the at least one message that carries information flow signaling comprises at least one information element that signals the at least one service parameter. 
     
     
       74. The controller of  claim 72 , wherein the at least one message that carries information flow signaling is communicated using at least one protocol selected from the group consisting of: Q.2931, Q.931, Q.932, and Q.933. 
     
     
       75. The controller of  claim 69 , wherein the first information flow occurs from a committed connection. 
     
     
       76. The controller of  claim 69 , wherein the shared communications medium is at least part of a cable television (CATV) networking environment. 
     
     
       77. The controller of  claim 69 , wherein the shared communications medium is at least part of a local area network (LAN). 
     
     
       78. The controller of  claim 69 , wherein at least one of the plurality of user terminals is a cable modem. 
     
     
       79. The controller of  claim 69 , wherein the quality of service indicated by the at least one service parameter is used to implement at least one class of service. 
     
     
       80. The controller of  claim 79 , wherein the at least one class of service is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       81. The controller of  claim 79 , wherein the at least one class of service is defined by the ATM Forum (Asynchronous Transfer Mode Forum). 
     
     
       82. The controller of  claim 69 , wherein the at least one service parameter comprises at least one a bit rate. 
     
     
       83. The controller of  claim 69 , wherein the at least one service parameter comprises at least one jitter requirement. 
     
     
       84. The controller of  claim 69 , wherein the at least one service parameter comprises at least one transit delay requirement. 
     
     
       85. The controller of  claim 69 , wherein the two way communications system is a cable system. 
     
     
       86. The controller of  claim 69 , wherein the upstream time slots comprise a first type of upstream time slots and a second type of upstream time slots, the first type of upstream time slots limited to carrying reservation requests, and the second type of upstream time slots capable of carrying data that is not limited to reservation requests. 
     
     
       87. The controller of  claim 86 , wherein the controller dynamically varies how many of the first type of upstream time slots exist relative to how many of the second type of upstream time slots exist in a specified amount of time. 
     
     
       88. The controller of  claim 69 , wherein the at least one first user terminal generates a first reservation request transmission in at least one third upstream time slot, wherein the at least one second user terminal generates a second reservation request transmission in the at least one third upstream time slot, and wherein the first reservation request transmission of the at least one first user terminal has a reservation request collision with the second reservation request transmission of the at least one second user terminal. 
     
     
       89. The controller of  claim 69 , wherein the at least one first user terminal generates a first upstream data transmission in at least one fourth upstream time slot, wherein the at least one second user terminal generates a second upstream data transmission in the at least one fourth upstream time slot, and wherein the first upstream data transmission of the at least one first user terminal has a data collision with the second upstream data transmission of the at least one second user terminal. 
     
     
       90. The controller of  claim 69 , wherein the granted burst size is less than the requested burst size. 
     
     
       91. The controller of  claim 69 , wherein a single user terminal of the plurality of user terminals generates a first upstream data transmission as at least part of the first information flow, wherein the single user terminal generates a second upstream data transmission as at least part of at least one second information flow, the at least one second information flow being maintained by the at least one first user terminal, the first information flow and the at least one second information flow both being active and multiplexed over the shared communications medium. 
     
     
       92. The controller of  claim 91 , wherein the first information flow provides a first class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR), and wherein the at least one second information flow provides a second class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       93. A method employed in a two way communications system comprising a controller and a plurality of user terminals, the two way communications system capable of carrying information flows and bursts of data of the plurality of user terminals, the controller transmitting downstream information to the plurality of user terminals on at least one downstream channel, the plurality of user terminals transmitting upstream information to the controller on at least one shared upstream channel of a shared communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, at least one media access control mechanism being used to resolve contention for transmission on the at least one shared upstream channel, an upstream information transmission of at least one first user terminal of the plurality of user terminals capable of colliding on the at least one shared upstream channel with an upstream information transmission of at least one second user terminal of the plurality of user terminals, the method comprising the steps of:
 sending a reservation request that solicits a first grant of at least one first upstream time slot to carry a requested burst of data, the requested burst of data having a requested burst size of finite amount; 
 maintaining a first information flow, the first information flow being associated with at least one service parameter, the first information flow having a quality of service indicated by the at least one service parameter; 
 receiving notice of the first grant from the controller responsive to the reservation request that solicits the first grant, the notice of the first grant indicating an allocation of the at least one first upstream time slot to carry a granted burst of data, the granted burst of data having a granted burst size and comprising a finite amount of data; and 
 receiving notice of a second grant from the controller responsive to the controller scheduling of a second grant, the notice of the second grant indicating an allocation of the at least one second upstream time slot to carry data that is at least part of the first information flow. 
 
     
     
       94. The method of  claim 93 , wherein the two way communications system is a cable system. 
     
     
       95. The method of  claim 93 , wherein the quality of service indicated by the at least one service parameter is used to implement at least one class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       96. The method of  claim 93 , wherein the at least one service parameter is at least one selection from the group consisting of: at least one bit rate, at least one jitter requirement, and at least one transit delay requirement. 
     
     
       97. The method of  claim 93 , wherein maintaining the first information flow further comprises the steps of:
 monitoring at least one message that carries information flow signaling; and 
 modifying a status of the first information flow responsive to the at least one message that carries information flow signaling. 
 
     
     
       98. The method of clam  93 , wherein the upstream time slots comprise a first type of upstream time slots and a second type of upstream time slots, the first type of upstream time slots limited to carrying reservation requests, and the second type of upstream time slots capable of carrying data that is not limited to reservation requests. 
     
     
       99. The method of  claim 98 , wherein the controller dynamically varies how many of the first type of upstream time slots exist relative to how many of the second type of upstream time slots exist in a specified amount of time. 
     
     
       100. The method of  claim 93 , wherein the at least one first user terminal generates a first reservation request transmission in at least one third upstream time slot, wherein the at least one second user terminal generates a second reservation request transmission in the at least one third upstream time slot, and wherein the first reservation request transmission of the at least one first user terminal has a reservation request collision with the second reservation request transmission of the at least one second user terminal. 
     
     
       101. The method of  claim 93 , wherein the at least one first user terminal generates a first upstream data transmission in at least one fourth upstream time slot, wherein the at least one second user terminal generates a second upstream data transmission in the at least one fourth upstream time slot, and wherein the first upstream data transmission of the at least one first user terminal has a data collision with the second upstream data transmission of the at least one second user terminal. 
     
     
       102. The method of  claim 93 , wherein the granted burst size is less than the requested burst size. 
     
     
       103. The method of  claim 93 , wherein a single user terminal of the plurality of user terminals generates a first upstream data transmission as at least part of the first information flow, wherein the single user terminal generates a second upstream data transmission as at least part of at least one second information flow, the at least one second information flow being maintained by the at least one first user terminal, the first information flow and the at least one second information flow both being active and multiplexed over the shared communications medium. 
     
     
       104. The method of  claim 103 , wherein the first information flow provides a first class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR), and wherein the at least one second information flow provides a second class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       105. A method employed in a two way communications system comprising a controller and a plurality of user terminals, the two way communications system capable of carrying information flows and bursts of data of the plurality of user terminals, the controller transmitting downstream information to the plurality of user terminals on at least one downstream channel, the plurality of user terminals transmitting upstream information to the controller on at least one shared upstream channel of a shared communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, at least one media access control mechanism being used to resolve contention for transmission on the at least one shared upstream channel, an upstream information transmission of at least one first user terminal of the plurality of user terminals capable of colliding on the at least one shared upstream channel with an upstream information transmission of at least one second user terminal of the plurality of user terminals, the method comprising the steps of:
 maintaining a first information flow, the first information flow being associated with at least one service parameter, the first information flow having a quality of service indicated by the at least one service parameter; 
 receiving notice of a first grant from the controller responsive to the controller scheduling of the first grant, the first grant message indicating an allocation of at least one first upstream time slot to carry data that is at least part of the first information flow; and 
 disregarding notice of a second grant from the controller, the notice of the second grant indicating the allocation of a second grant of at least one second upstream time slot to the at least one second user terminal, the second grant generated by the controller responsive to the at least one second user terminal sending a reservation request that solicits the second grant to carry a requested burst of data, the requested burst of data having a requested burst size of finite amount. 
 
     
     
       106. The method of  claim 105 , wherein the two way communications system is a cable system. 
     
     
       107. The method of  claim 105 , wherein the quality of service indicated by the at least one service parameter is used to implement at least one class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR). 
     
     
       108. The method of  claim 105 , wherein the at least one service parameter is at least one selection from the group consisting of: at least one bit rate, at least one jitter requirement, and at least one transit delay requirement. 
     
     
       109. The method of  claim 105 , wherein maintaining the first information flow further comprises the steps of:
 monitoring at least one message that carries information flow signaling; and 
 modifying a status of the first information flow responsive to the at least one message that carries information flow signaling. 
 
     
     
       110. The method of  claim 105 , wherein the upstream time slots comprise a first type of upstream time slots and a second type of upstream time slots, the first type of upstream time slots limited to carrying reservation requests, and the second type of upstream time slots capable of carrying data that is not limited to reservation requests. 
     
     
       111. The method of  claim 110 , wherein the controller dynamically varies how many of the first type of upstream time slots exist relative to how many of the second type of upstream time slots exist in a specified amount of time. 
     
     
       112. The method of  claim 105 , wherein the at least one first user terminal generates a first reservation request transmission in at least one third upstream time slot, wherein the at least one second user terminal generates a second reservation request transmission in the at least one third upstream time slot, and wherein the first reservation request transmission of the at least one first user terminal has a reservation request collision with the second reservation request transmission of the at least one second user terminal. 
     
     
       113. The method of  claim 105 , wherein the at least one first user terminal generates a first upstream data transmission in at least one fourth upstream time slot, wherein the at least one second user terminal generates a second upstream data transmission in the at least one fourth upstream time slot, and wherein the first upstream data transmission of the at least one first user terminal has a data collision with the second upstream data transmission of the at least one second user terminal. 
     
     
       114. The method of  claim 105 , wherein the granted burst size is less than the requested burst size. 
     
     
       115. The method of  claim 105 , wherein a single user terminal of the plurality of user terminals generates a first upstream data transmission as at least part of the first information flow, wherein the single user terminal generates a second upstream data transmission as at least part of at least one second information flow, the at least one second information flow being maintained by the at least one first user terminal, the first information flow and the at least one second information flow both being active and multiplexed over the shared communications medium. 
     
     
       116. The method of  claim 115 , wherein the first information flow provides a first class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (UBR), and wherein the at least one second information flow provides a second class of service that is at least one selection from the group consisting of: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR), and unspecified bit rate (LJBR). 
     
     
       117. A method for scheduling data transmissions, wherein the method is employed in a two-way communications system comprising a controller and a plurality of stations, the two-way communications system capable of carrying information flows and bursts of data of the plurality of stations, the controller transmitting downstream information to the plurality of stations on at least one downstream channel, the plurality of stations transmitting upstream information to the controller on at least one shared upstream channel of the communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, the method comprising:
 processing a request for recurring time slots that includes soliciting a first grant of at least one first upstream time slot the at least one shared upstream channel of the communications medium, the at least one shared upstream channel capable of carrying an upstream transmission from a first station, the transmission capable of colliding with an upstream transmission from at least one second station, the time slots for carrying bursts of data having a burst size of finite amount;   scheduling a plurality of unsolicited upstream transmission grants comprising a second grant of at least one second upstream timeslot, the scheduling being based at least upon a first entry in a list of at least one information flow and at least one service parameter, the second grant being scheduled to provide a first information flow with a quality of service indicated by the at least one service parameter, the first information flow being associated with the first entry in the list of at least one information flow;   sending notice of the first grant to the plurality of stations responsive to the request for recurring time slots, the notice of the first grant indicating an allocation of the at least one first upstream time slot to carry a granted burst of data, the granted burst of data having a granted burst size and comprising a finite amount of data; and   sending notice of the second grant to the plurality of stations responsive to the scheduling of the second grant, the notice of the second grant indicating an allocation of the at least one second upstream time slot to carry data that is at least part of the first information flow.   
     
     
       118. The method of claim 117, further comprising: sending a response to the request for the recurring time slots. 
     
     
       119. The method of claim 117, further comprising: receiving the request for recurring time slots in the upstream channel. 
     
     
       120. The method of claim 117, further comprising: maintaining a collection of information flows, the collection of information flows being associated with at least one service parameter. 
     
     
       121. The method of claim 117, further comprising: sending the plurality of unsolicited upstream transmission grants, the grants meeting the requested quality of service of the first information flow defined by the at least one service parameter. 
     
     
       122. The method of claim 121, further comprising: receiving the bursts of data on the upstream channel responsive to at least one of the plurality of unsolicited grants. 
     
     
       123. The method of claim 117, wherein upon determining that additional information in excess of the burst size is required to be sent: processing a supplemental upstream data request. 
     
     
       124. The method of claim 123, wherein the supplemental upstream data request is transmitted within a previously scheduled data burst. 
     
     
       125. The method of claim 123, further comprising: scheduling at least one supplemental upstream transmission grant responsive to the supplemental upstream data request. 
     
     
       126. The method of claim 125, further including: transmitting the at least one supplemental grant responsive to the supplemental upstream data request. 
     
     
       127. The method of claim 126, further comprising: receiving at least one supplemental burst of data on the upstream channel responsive to the at least one supplemental grant. 
     
     
       128. The method of claim 117, wherein the communications medium is at least part of a cable television networking environment. 
     
     
       129. The method of claim 117, wherein the bursts of data are carried in anyone of ATM cells or packets. 
     
     
       130. The method of claim 117, wherein the bursts of data comprise anyone of digitized voice or digitized video. 
     
     
       131. The method of claim 117, wherein the information flow is from a local area network (LAN). 
     
     
       132. A controller in a two-way communications system comprising a controller and a plurality of stations, the two-way communications system capable of carrying information flows and bursts of data of the plurality of stations, the controller transmitting downstream information to the plurality of stations on at least one downstream channel, the plurality of stations transmitting upstream information to the controller on at least one shared upstream channel of the communications medium, the bandwidth of the at least one shared upstream channel being divided into upstream time slots, the upstream time slots capable of carrying reservation requests and data, the controller comprising:
 logic configured to process a request for recurring time slots that includes soliciting a first grant of at least one first upstream time slot in the at least one shared upstream channel of the communications medium, the at least one shared upstream channel capable of carrying an upstream transmission from a first station, the transmission capable of colliding with an upstream transmission from at least one second station, the time slots for carrying bursts of data having a burst size of finite amount;   logic configured to schedule a plurality of unsolicited upstream transmission grants comprising a second grant of at least one second upstream timeslot, the scheduling being based at least upon a first entry in a list of at least one information flow and at least one service parameter, the second grant being scheduled to provide a first information flow with a quality of service indicated by the at least one service parameter, the first information flow being associated with the first entry in the list of at least one information flow;   logic configured to send notice of the first grant to the plurality of stations responsive to the request for recurring time slots, the notice of the first grant indicating an allocation of the at least one first upstream time slot to carry a granted burst of data, the granted burst of data having a granted burst size and comprising a finite amount of data; and   logic configured to send notice of the second grant to the plurality of stations responsive to the scheduling of a second grant, the notice of the second grant indicating an allocation of the at least one second upstream time slot to carry data that is at least part of the first information flow.   
     
     
       133. The controller of claim 132, further comprising: logic configured to send a response to the request for the recurring time slots. 
     
     
       134. The controller of claim 132, further comprising: logic configured to receive the request for recurring time slots in the upstream channel. 
     
     
       135. The controller of claim 132, further comprising: logic configured to maintain a collection of information flows, the collection of information flows being associated with at least one service parameter. 
     
     
       136. The controller of claim 132, further comprising: logic configured to send the plurality of unsolicited upstream transmission grants, the grants meeting the requested quality of service of the first information flow defined by the at least one service parameter. 
     
     
       137. The controller of claim 136, further comprising: logic configured to receive the bursts of data on the upstream channel responsive to at least one of the plurality of unsolicited grants. 
     
     
       138. The controller of claim 132, further comprising: logic configured to process a supplemental upstream data request upon determining that additional information in excess of the burst size is required to be sent. 
     
     
       139. The controller of claim 138, wherein the supplemental upstream data request is transmitted within a previously scheduled data burst. 
     
     
       140. The controller of claim 138, further comprising: logic configured to schedule at least one supplemental upstream transmission grant responsive to the supplemental upstream data request. 
     
     
       141. The controller of claim 140, further including: logic configured to transmit the at least one supplemental grant responsive to the supplemental upstream data request. 
     
     
       142. The controller of claim 141, further including: logic configured to receive at least one supplemental burst of data on the upstream channel responsive to the at least one supplemental grant. 
     
     
       143. The controller of claim 132, wherein the communications medium is at least part of a cable television networking environment. 
     
     
       144. The controller of claim 132, wherein the bursts of data are carried in ATM cells or packets. 
     
     
       145. The controller of claim 132, wherein the bursts of data comprise anyone of digitized voice or digitized video. 
     
     
       146. The controller of claim 132, wherein the information flow is from a local area network (LAN).