Method for providing integrated packet services over a...

Details Method for providing integrated packet services over a... Method for providing integrated packet services over a...

1999-03-25

2003-05-13

Ton, Dang (Department: 2661)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S230000, C370S395400, C370S412000, C370S447000, C370S468000

Reexamination Certificate

active

06563829

ABSTRACT:

1. BACKGROUND OF THE INVENTION
The invention relates in general to the field of computer network communications and, more particularly, to a method for fairly allocating transmission bandwidth in a shared-media packet-switched network.
1.1 Introduction
As originally designed and implemented, cable television (CATV) systems used only coaxial cable between a head-end controller, or distribution station, and the customer. Newer cable systems tend to be hybrids of fiber optics and coaxial cable; optic fiber being used for long distance distribution and coax being used for the last few thousand feet into individual customer sites.
FIG. 1
shows a hybrid fiber-coax (HFC) system
100
comprising a head-end controller
105
connected via one or more fiber optic links
110
to a fiber-to-coax conversion unit
115
which, in turn, feeds a coaxial cable distribution network
120
running into a number of individual user or customer sites (e.g., homes
125
). Cable television systems with this general type of hardware layout are fairly typical in the art today.
Cable systems originally provided uni-directional transfer of programming from the head-end controller
105
to the customer
125
. With the growth of computer networks and a desire to provide a real-time interactive services to the customer, the need for an efficient means to provide two-way communication over an existing HFC network type network exists. A number of services providers currently furnish two-way services over cable. In these services there is generally a modestly high bandwidth link from the head-end controller to the user site. However, the link in the other direction, from the user's site to the network, is through conventional dial-up facilities such as a modem or an integrated services and data network (ISDN) connection, which commonly have a much lower bandwidth than the head-end-to-user-site link. Such systems allow the customer to quickly download material from the network into their local machine (e.g., a personal computer or, more generally, a terminal equipment), but does not readily permit the user to originate any significant transmissions.
One way of enabling customers to originate significant transmissions is to permit them to use the cable system, which has a comparatively high bandwidth, for such transmissions. Within existing HFC networks, providing customers with the ability to transmit data upstream requires service providers (those organizations that operate head-end stations) to reserve sections of cable spectrum, i.e., bandwidth, for data services, and also to provide a mechanism for allocating that bandwidth to upstream users. As shown in
FIG. 2
, reserved bandwidth can be used to create virtual downstream
200
and upstream
205
channels. In this manner downstream and upstream data is (frequency) multiplexed over a single physical transmission cable
120
between one or more customer sites (via terminal equipment
210
such as a cable modem or a television set-top box) and a head-end controller
105
via a fiber-to-coax conversion unit
115
.
FIG. 3
is a block diagram of a generic communication network
300
comprising a bandwidth allocation unit (BAU)
305
, a physical communications network
310
, and a plurality of network access units (NAUs)
315
. Like to head-end controller
105
, a bandwidth allocation unit is responsible for allocating downstream bandwidth (i.e., transmission from or through a bandwidth allocation unit
305
toward a network access unit
315
or customer/user site) and upstream bandwidth (i.e., transmission from a network access unit
315
or customer/user site toward a bandwidth allocation unit
305
) over the network
310
. In particular, a bandwidth allocation unit
305
is responsible for processing requests for transmission bandwidth from network access units
315
(such as, for example, a user's terminal equipment
210
). A network access unit
315
can be, for example, a terminal equipment
210
such as a personal computer located at a customer's site.
1.2 Some Useful Definitions
The following alphabetical list of definitions and accompanying discussion, regarding various aspects of network characteristics and bandwidth allocation, are provided for the benefit of the reader.
ATM. Asynchronous Transfer Mode, which generally refers to a very specific telecommunications “protocol,” discussed at the end of Section 1.3.
Authorization. Permission issued by a bandwidth allocation unit (BAU) to either a single network access unit (NAU) or a group of network access units that grants or permits use of the network access unit to bandwidth allocation unit (i.e., upstream) transmission resource during a specific time period. The case of the bandwidth allocation unit issuing permission to a single network access unit is called a “directed grant,” when permission is issued to multiple network access units it is called a “contention grant.” Authorizations are “use it or lose it.” See also the discussion of Grant, below.
Bandwidth Allocation Unit (BAU). The collection of those bandwidth allocation functions co-located within a head-end controller responsible for the scheduling and allocation of transmission resources for both the downstream and the upstream channels of the shared media.
Class of Service. Even though the quality of service (QoS, see below) requirements of users may vary over a continuous spectrum of values, a network can only handle a restricted set of QoS classes corresponding to specific objective values of the relevant network performance parameters.
The ITU (International Telecommunications Union) specifies the following QoS classes in Recommendation I.371.
1. Deterministic Bit Rate (DBR): Traffic conformance is based on peak cell rates (PCR) and is characterized by low cell delay variation (CDV) and low cell loss ratio (CLR).
2. Statistical Bit Rate (SBR): Traffic conformance is based on a sustainable cell rate (SCR), a burst size and a PCR and is characterized by a medium to large CDV and low CLR.
3. Available Bit Rate (ABR): Traffic conformance is based on dynamic feedback of the actual capacity available within the network. Sources may always send at a signaled
egotiated minimum cell rate (MCR) and must never send at more than the PCR. This service type is characterized by large CDV, variable CTD, and low CLR.
The ATM Forum has adopted the ITU's classes and has further added the following service classes.
1. Deterministic bit rate is designated as constant bit rate (CBR).
2. Statistical bit rate is designated as variable bit rate (VBR).
3. Real-Time Variable Bit Rate (rt-VBR): Traffic conformance is based on a sustainable rate, a burst size and a peak rate. This service is characterized by a low CDV and low CLR.
4. Unspecified Bit Rate (UBR): Traffic conformance is based on the peak cell rate and can have potentially very large CDV and CLR.
The IETF (Internet Engineering Task Force) has defined the following service classes.
1. Real-Time: Traffic conformance is based on a token bucket with a sustainable rate, and a bucket size; peak rate is assumed to be the line rate. Real-time services are characterized by low packet delay variation and very low packet loss.
2. Predictive: Traffic conformance is based on a token bucket with a sustainable rate and a bucket size; peak rate is assumed to be the line rate. Predictive services' are characterized by medium packet delay variation and low (but larger than that of real-time) packet loss.
3. Best Effort: No traffic conformance. Characterized by large packet delay variation and a potentially large packet loss.
FIFO. First-In, First-Out, a method of managing a queue of items, referred to at the end of Section 1.3.
Flow. For the purposes of this document, a flow is a set of packets traversing a network or subnetwork all of which are covered by the same request for control of quality of service. At a given network element a flow may consist of the packets from a single application session, or it may be an aggregation comprising the combined data traffic from a number of application ses

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