Mitsubishi Electric Research Laboratories, Inc.

Mitsubishi Electric Information Technology Center America, Inc.

Juniper Networks, Inc.

Mitsubishi Electric Information Technology Center America, Inc (ita)

Qin Zheng

John H Howard

Randy B Osborne

Hugh C Lauer

Steven R Willis

Chia Shen

Frank Kastenholz

Eric S Crawley

Abhijit Ghosh

Harufusa Kondoh

According to one embodiment, the invention is directed to a facility for providing Asynchronous Transfer Mode (ATM) and Internet Protocol (IP) Quality of Service (QoS) features in a digital communication node. The facility includes a plurality of logical input ports, a plurality of logical output ports, ATM switching elements, IP routing elements and QoS elements. The switching and forwarding elements transfer ATM data cells and IP data packets from the logical input ports to the logical output ports. The QoS elements prioritize, schedule and flow control the transfer of data, based at least in part on ATM QoS features associated with the ATM data cells and on IP QoS features associated with the IP data packets.

Quality of service facility in a device for performing IP forwarding and ATM switching

In an ATM network, a traffic management system is provided to allow simple nd effective implementation of rate-based available bit rate, or ABR, flow control at ATM switches, with the subject system using an innovative queue length based approach to calculate the cell rate that a source system can use to send cells. In one embodiment, the cell rate is calculated as an exponential function of the cell queue length at a switch, and the rate value is carried back to a source system via resource management, or RM, cells. The exponential rate calculation function provides a large stability region for a network for better flow control performance than other systems, with the subject system being easy to implement in ATM switches.

Queue length based ABR flow control system

In a cell switched network such as an ATM network, a connection admission ntrol system is provided to establish connections which guarantee user requested end-to-end cell transmission delay bounds. The subject system uses, a bit stream approach to model the worst case cell generation pattern of a connection and provides mechanisms to construct new bit streams after the original ones are delayed, multiplexed, demultiplexed, or filtered within a network. Given arriving bit streams at a queueing point, a system is provided to obtain the worst-case cell queueing delay which is used to check if a connection can be established with the requested delay bounds. In one embodiment, the subject system uses the CBR/VBR traffic models as defined in the ATM Forum Traffic Management Specification Version 4.0 to derive the worst-case bit stream for a connection and calculates the worst case queueing delay based on the conventional static priority First In First Out, or FIFO, cell transmission scheduling at switches. The subject invention provides a simple and efficient way to support real-time CBR/VBR services as defined by the ATM Forum over existing ATM networks without requiring a sophisticated cell transmission scheduling mechanism at switches.

Bit stream based connection admission control system

In an ATM network interface controller, a traffic management system is provided to allow implementation of available bit rate, or ABR, flow control by an external processor and the use of a new ABR controller within the traffic management system which provides functions that enable an external processor to control the flow control behavior of the network interface controller. The ABR controller accesses an external memory to control the flow of cells injected into the network. In one embodiment, the subject system uses a traffic shaper to control cell transmission rates, submits requests to an external memory which are processed by an external processor, and reads data from an external memory to adjust cell transmission rates and/or generates Resource Management, or RM, cells. More particularly, in one embodiment, the traffic shaper uses a timing chain approach enhanced with a delay queue which is capable of delaying transmission of i cell for a long period of time, thus being able to accurately control a wide range of cell transmission rates for multiple cell streams independently. The subject system submits requests to an external memory when it receives an RM cell, sends an RM cell, or when reaching a cell transmission limit, initiates processing by an external processor. An external processor communicates with the subject system by writing data into an external memory. The subject system reads data from the memory and determines what cell to send, how long it should be delayed before sending a next cell, thus allowing an external processor to easily control the behavior of an ATM network interface controller to implement a wide variety of flow control schemes.

Traffic shaping and ABR flow control

A switch for digital communication networks includes a queuing system cape of implementing a broad class of scheduling algorithms for many different applications and purposes, with the queuing system including both a tag-based primary queue which contain ATM cells organized by priority and a secondary queue which contains ATM cells which are not yet scheduled for transmission and which are organized by virtual channel. A queuing decision module is provided to determine in which queue an incoming ATM cell should be deposited. A requeuing module operates when an event occurs that unblocks a particular virtual channel. The requeuing module, on occurrence of such an event, accesses the secondary queue to obtain another cell, to assign it priority and to move it to the primary queue. The queuing decision module, along with a virtual channel table, can be used easily to block virtual channels when necessary. The combination of queues also allows for round robin scheduling.

ATM local area network switch with dual queues

In an ATM network, a traffic shaping system is provided with a number of timing subchains each having slots at which cells are queued and each having a pointer to specify the readout of cells at a slot. The system eliminates the necessity for providing large numbers of slots for low data rate traffic while at the same time accommodating high data rate transmission by moving pointers for low data rate traffic at slower rates than pointers for higher data rates. In one embodiment, this is accomplished by increasing the time scale for slots far away from the current time by moving the time pointer increasingly slower for ever more distant slots. When a pointer is at a slot, cells queued at this slot are moved to a slot in the next prior subchain, with cells in the top subchain transmitted when selected by the associated pointer.

Traffic shaping system using two dimensional timing chains

A system for controlling traffic in a digital communication network to avoid data loss due to congestion utilizes both credit-based and rate-based traffic control approaches within a common framework, and adjusts the rate at which data is transmitted from a source in accordance with feedback in a form of credit values from a destination reflecting the ability of the network to transmit data and the destination to receive data. In one embodiment, the destination receives the information about network congestion, and, knowing its own capacity to receive more data, generates a credit in the form a numeric value which is fed back to the source so that the source adjusts its transmission rate to avoid data loss due to congestion in the network.

Credit/rate-based system for controlling traffic in a digital

A system is provided for generating the minimum synchronous bandwidth allocation h.sub.i for token ring networks in which this minimum bandwidth allocation is utilized by the node to request appropriate synchronous bandwidth reservation from the network manager. This permits the synchronous bandwidth allocation h.sub.i to be set dependent upon the minimum message generation period, T, the maximum message transmission time, C, the requested message delivery delay bound, d, and the target token rotation time of the network, TTRT. The system is not limited to d=T as is common in prior systems, but rather accommodates any value of d. As a result, the system is both simpler to implement, and covers many more applications having different message delivery time constraints. The calculation of h.sub.i is done by ensuring that the time that a node is allowed to transmit messages in the worst-case is no smaller than the time that the node needs to satisfy the message delivery time constraints.

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Belmont, MA, United States of America

Qin Zheng