Multiplex communications – Pathfinding or routing – Store and forward
Reexamination Certificate
1999-03-15
2003-03-25
Zimmerman, Brian (Department: 2635)
Multiplex communications
Pathfinding or routing
Store and forward
C370S252000, C370S412000
Reexamination Certificate
active
06539026
ABSTRACT:
BACKGROUND OF THE INVENTION
A typical data communications network includes many hosts interconnected by various data communication devices. The data communication devices can be routers, bridges, switches, access servers, gateways, hubs, proxy servers, repeaters and so forth which exchange data over an interconnection of data links. The data links may be physical cables or may be provided using wireless communication mechanisms. The network allows data to propagate between sending and receiving hosts. The sending and receiving hosts are often general purpose computer systems such as personal computers, workstations, minicomputers, mainframes and the like, or the hosts may be dedicated devices such as web-site kiosks, facsimile servers, video servers and so forth. Each host couples to one or more of the data communications devices that form the network.
Various physical data communications connection mechanisms allow hosts to interconnect with the network. Physical data communications connection mechanisms such as modems, transceivers, network interface cards, fiber optic cards, ports or other hardware devices allow data to be transferred at various maximum and minimum data transfer rates to and from the hosts. For example, certain hosts may have high-speed network interfaces which provide physical connections to the network at high data rates such as fractional T
1
, T
1
, E
1
or higher, while other hosts may use an inexpensive modem that provides a maximum data transfer rate of 56.6 kilobits per second (Kbps) to and from the network.
Depending upon the specific use or application running on a host, different levels of service (i.e., data transfer rates) may be required for data transmitted to and from the host. For example, hosts that-connect or subscribe to networks using high speed connection mechanisms such T
1
cards generally expect to be provided with, and often pay a premium for the ability to send and receive data at T
1
data rates. Other hosts may not require such high data transfer rates and therefore only subscribe to the network and pay for the capability to transfer data at lower data transfer rates.
Since connections or data traffic flows from multiple hosts with potentially different data rates are frequently switched, routed or transferred through the same data communication devices in a network such as the Internet, the data communications devices must provide a way to distinguish the different data flows or connections requiring different levels of service (i.e., different data rates). Once distinguished, the data communications devices must be able to service each connection or flow at its prescribed level of service. Thus, data transmitted over a T
1
link must generally be transported,through the network at T
1
speeds, while data from a slower link should at least be transferred through the network at a minimum subscription rate. Management of the various delay requirements associated with data having differing levels of service is a well known problem associated with data communications devices in modern networks.
The problem of delay management also stems from the various types of data that can be transmitted through a network between sending and receiving hosts. For example, modem data, facsimile data, video data, voice data or other data types may all be transmitted using packets, cells, frames or another mechanism over a commonly shared network medium. Each of these data types may have certain Quality of Service (QoS) requirements with respect to how quickly that data must be transferred through the network.
Video and voice data, for instance, generally must be transferred in real-time over a network so that a receiving host can correctly reconstruct a video or voice signal from the data. If real-time transmission is not provided and the data is delayed too long in the network, the viewer or listener at the receiving host may experience drops outs or degraded service. Conversely, many types of modem data transmissions such as e-mail communications, for example, typically have no specific bandwidth, QoS, or delay requirements to be met as the data is propagated through the network. In between these two extremes, data such as facsimile data may require adherence to certain minimum protocol delay or quality of service requirements which do not rise to the demands of real-time transmission but which also cannot allow for significant delays in transmission.
Other examples of delay management can arise when certain data communication protocols require data to be delivered according to certain delay attributes. An example of this is the use of specialized protocols for remote sensing and process control applications, where data must be exchanged in a timely manner to correctly operate equipment in response to a stimulus. Whether delay requirements are due to varying data transmission rates, different data types, specialized protocols requiring minimum QoS levels or other concerns, the data communications devices in a network are generally responsible for managing the delay of data as it propagates through the network.
Various prior art schemes have been developed to allow a data communications device to handle the transfer of data at differing levels of service. Most involve providing separate data queues for the different types of data or different levels of service and use a weighted round-robin or other type of queue servicing algorithm or de-queuing mechanism to remove data for transmission from the various queues at different rates. For example, a high priority queue may be serviced twice as often as a low priority queue, thus allowing twice as much high priority data to propagate through the device. In this manner, prior art systems attempt to control delay and priority of data passing through the network using separate delay control mechanisms for each type of data.
SUMMARY OF THE INVENTION
Embodiments of the present invention relate to delay management, scheduling and controlling the delay of data passing through a data communications device in a data communications network. More specifically, the invention relates to a unique and flexible queuing, storage and delay scheduling mechanism that allows a delay scheduling process to delay data having various attributes.
According to one aspect of the invention, a delay manager apparatus and method are provided to schedule delays of data in a data communications device. The apparatus includes an input for receiving unscheduled data and a delay controller which includes a predetermined number of storage locations. The apparatus and method involve managing the delay of data in the data communications device by configuring a predetermined number of the storage locations. to store data passing through the data communications device, with each storage location having an associated delay.
A data scheduler is provided and is coupled to the input to receive the unscheduled data. The data scheduler determines a delay associated with the unscheduled data and deposits the unscheduled data into one of the predetermined number of storage locations in the delay controller. The selected storage location has a predetermined associated delay that generally corresponds to the delay associated with the unscheduled data. The delay controller includes a delay control processor which adjusts the associated delay over time of data deposited in each of the predetermined number of storage locations. A transmission buffer is coupled to the delay controller, and transmits data deposited into a storage location that has an associated delay equal to a predetermined delay transmit value. In this manner, the invention imposes delays on data passing through a data communications device.
Preferably, the delay manager also includes a policy controller coupled to the data scheduler and the delay controller. The policy controller receives a network policy which defines delay categories for data passing through the data communications device. The policy controller analyzes the network policy and provides control commands to the data sche
Chapin & Huang , L.L.C.
Chapin, Esq. Barry W.
Zimmerman Brian
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