Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1999-07-21
2004-08-03
Lee, Andy (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C709S226000
Reexamination Certificate
active
06771661
ABSTRACT:
BACKGROUND OF THE INVENTION
A typical data communications network includes many hosts interconnected by various data communication devices. The data communications devices can be routers, bridges, switches, access servers, gateways, hubs, concentrators, proxy servers, repeaters and so forth which exchange data over an interconnection of data links. The data links may be physical connections or may be provided using wireless communication mechanisms. The network allows data to propagate between various applications that execute on the hosts. The hosts are often general purpose computer systems such as personal computers, workstations, minicomputers, mainframes and the like, or the hosts may be more special purpose computer systems or dedicated devices such as web-site kiosks, facsimile or email servers, video servers, audio servers, and so forth. Each computer host couples either physically or via wireless data link to one or more of the data communications devices that form the network. By way of example, many businesses provide a network of computer hosts to allow employees of the business to exchange data, communicate and generally carry out the functions of the business.
Various physical or hardware data communications connection mechanisms allow the hosts to interconnect with the network. Physical data communications connection mechanisms can include modems, transceivers, network interface cards, fiber optic cards, ports and other hardware devices which allow data to be transferred at various data transfer rates (i.e., bandwidths) to and from the hosts and between the data communications devices. For example, certain hosts on a business network may have high-speed network interfaces which provide connections to the network at high data transfer rates such as fractional-T1, T1, E1 or higher, while other hosts may use inexpensive modems or network interface cards that provide much slower maximum data transfer rates to and from the network.
Depending upon a specific use of a host or group of hosts in a network, which often depends on an application running on the host(s), data traveling across portions of the network may require different levels of data service (i.e., data transfer rates or network bandwidth). For example, a backup server (e.g., a high powered computer containing large amounts of data storage) on a typical network used in a business may require a high speed connection to the network to perform nightly backups of data stored on each employee computer. The backup server may, for example, be connected to a fiber optic backbone in the network which offers very high speed data transfer rates. The high speed offered by the fiber optic backbone may allow, for example, data from many employee computers to be simultaneously backed-up by the backup server thus allowing completion of the data backup process for each employee computer before the start of the next business day.
As another example in the business network setting, certain employee computers which rely heavily on data communications applications may require high speed connections to the business network, while other employee computers used, for example, for administrative purposes, may only require low speed network connections. Employees such as engineers using the high speed data communications computers may require high speed network access, while administrative employees using administrative computers may only require minimal network access with low data transfer rates. Within the network itself however, the various data communications devices such as routers, switches and hubs, which channel the data across the network between computer hosts (either during nightly backups, or during the day for employee communications) must be able to distinguish and properly transmit the different flows of data from hosts that require different levels or qualities of data transfer service.
Since many connections, sessions or data traffic flows (i.e., data associated with an end-to-end application or stream) from multiple hosts with potentially different data rates are frequently switched, routed or transferred through the same data communication devices in a network, the data communications devices must provide a way to establish, allocate or reserve the bandwidth requirements for each flow, session, or connection. Once the bandwidth is allocated, the devices must distinguish the different data flows or connections requiring the different levels of service (i.e., different data rates or bandwidth requirements). Once distinguished, the data communications devices must service each connection or flow at its prescribed level of service. For example, if T1 data rates are required for the backup server, the data communications devices must identify and transport backup data through the network at T1 speeds, while other data that may also be present on the network is transferred at some other data rate, such as a “best-effort-only” data rate. Management of the various data transmission and propagation requirements associated with data having differing levels of service is a well known problem associated with data communications devices in modem networks.
Various bandwidth allocation or reservation protocols have been developed for use in modem networks to provide guaranteed Quality of Service (QoS) or controlled end-to-end delays for transmitted data. These protocols allow applications that exchange data between sending and receiving hosts (e.g., employee computers and the backup server) to establish reservations of bandwidth over the network for the various services required by the applications. One such protocol is called RSVP, which stands for the Resource ReSerVation Protocol.
As its name implies, computer hosts can use RSVP to request a specific QoS from the network on behalf of an application data stream. When a host needs bandwidth, the host transmits an RSVP bandwidth reservation request message on the network along the path of the session of data communications. RSVP processes in each data communications device in the network propagate the request through the network to each data communications device (e.g., router, switch, hub) or node that the network uses to transport the session data. At each node, the RSVP process for that node attempts to make a resource (i.e. bandwidth) reservation for the stream specified in the RSVP request at that moment in time. As bandwidth is successfully reserved in each node on the network path from sending host to receiving host, the data associated with the session of data communications can use the reserved network bandwidth, while other data streams are excluded from using the reserved bandwidth resources. In other words, the QoS (e.g., data rate or allocated bandwidth) for that stream is generally guaranteed since the bandwidth is reserved in each node for use by that particular stream (e.g., backup data) and no other. When the sending and receiving hosts no longer require the use of the reserved bandwidth, the hosts mutually agree to release the reserved bandwidth via a series of RSVP un-reserve (i.e., tear-down) protocol messages sent to each data communications device on the path of the reserved data. The data communications devices receive the RSVP un-reserve (tear-down) messages and release the formerly reserved bandwidth resources, allowing these resources to be used for the transfer of other data.
FIG. 1
illustrates a typical architecture and data flow of a prior art data communications device
100
configured to use RSVP. Traditionally, to make a resource reservation in the data communications device
100
(e.g. a router), an RSVP process
101
executing on the device
100
receives an RSVP request (not shown) from a host and communicates this request to two local decision modules, admission control
102
and policy control
103
. Admission control
102
determines whether the device
100
has sufficient available resources (e.g., buffer capacity, processor and I/O bandwidth) to supply the requested QoS. Policy control
103
determines whether a user, host or applicatio
Chawla Hamesh
Waclawsky John G.
Chapin & Huang LLC
Chapin, Esq. Barry W.
Cisco Technology Inc.
Lee Andy
LandOfFree
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