Multiplex communications – Fault recovery
Reexamination Certificate
1999-05-27
2002-11-26
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Fault recovery
C370S409000, C709S228000, C710S108000
Reexamination Certificate
active
06487168
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data communications networks and more particularly relates to a system for establishing static/permanent Switched Virtual Circuits (SVCs) in a connection oriented network such as an Asynchronous Transfer Mode (ATM) network.
BACKGROUND OF THE INVENTION
Asynchronous Transfer Mode
Currently, there is a growing trend to make Asynchronous Transfer Mode (ATM) networking technology the base of future global communications. ATM has already been adopted as a standard for broadband communications by the International Telecommunications Union (ITU) and by the ATM Forum, a networking industry consortium.
ATM originated as a telecommunication concept defined by the Comite Consulatif International Telegraphique et Telephonique (CCITT), now known as the ITU, and the American National Standards Institute (ANSI) for carrying user traffic on any User to Network Interface (UNI) and to facilitate multimedia networking between high speed devices at multi-megabit data rates. ATM is a method for transferring network traffic, including voice, video and data, at high speed. Using this connection oriented switched networking technology centered around a switch, a great number of virtual connections can be supported by multiple applications through the same physical connection. The switching technology enables bandwidth to be dedicated for each application, overcoming the problems that exist in a shared media networking technology, like Ethernet, Token Ring and Fiber Distributed Data Interface (FDDI). ATM allows different types of physical layer technology to share the same higher layer—the ATM layer.
ATM uses very short, fixed length packets called cells. The first five bytes, called the header, of each cell contain the information necessary to deliver the cell to its destination. The cell header also provides the network with the ability to implement congestion control and traffic management mechanisms. The fixed length cells offer smaller and more predictable switching delays as cell switching is less complex than variable length packet switching and can be accomplished in hardware for many cells in parallel. The cell format also allows for multi-protocol transmissions. Since ATM is protocol transparent, the various protocols can be transported at the same time. With ATM, phone, fax, video, data and other information can be transported simultaneously.
ATM is a connection oriented transport service. To access the ATM network, a station requests a virtual circuit between itself and other end stations, using the signaling protocol to the ATM switch. ATM provides the User Network Interface (UNI) which is typically used to interconnect an ATM user with an ATM switch that is managed as part of the same network.
SVC Traffic Analysis
Networks that are connection oriented typically have two stages for connecting network users from point to point. The first stage in the establishment of the connection utilizes some form of signaling mechanism and in the second stage, data is transferred via the connection established in the first stage.
An example of such as connection oriented network is an ATM network. In the first stage, virtual connections are created using a complicated signaling/routing protocol such as Q.SAAL, Q.93, IISP, and/or PNNI between peer network nodes along the connection path to provide network users a service for establishing a connection to another network user. This connection is termed a Switched Virtual Connection (SVC) and, once created, is used as the data path between the users that have been connected.
The connection originator uses the signaling protocol to convey the service details it is requesting the network to provide, e.g., destination address (i.e. the called address), calls of service, traffic descriptor, protocol which is to be used by the virtual connection, network transit, etc. In addition, the originator provides information about itself, in particular, its own address (i.e. the calling address).
Once the network receives the request from the originator user, it attempts to find a route to the destination that has sufficient resources to fulfill the specific characteristic requirements of the request as provided by the originating user. If the network finds a satisfactory route with the necessary resources to establish the connection, and if the called user also has sufficient resources to establish the connection, the connection is then established. Once the route is established, data can flow between source and destination over the connection.
Such a network may carry another type of connection known as a Permanent Virtual Circuit (PVC) which is typically established under manual management control. The service provided by PVCs and SVCs are the same, with the difference being their method of establishment.
The signaling/routing protocol used typically consumes a high percentage of computation resources in a node. This makes the connection establishment process slow. PVCs, as an alternative to SVCs are set via management in a manual fashion on each network node along the path. The PVC connections are typically stored in the system memory within the nodes making up the connection and are re-established in the event one or more portions of the connection fail. The connections are re-established and restored automatically, quickly and without the overhead of the signaling and routing protocol.
In the course of network operations, SVCs may be constantly created and torn down. SVC connections may be created very quickly and last for a relatively short lifetime duration, i.e., hundreds of milliseconds, seconds, etc., before being removed. In many networks today, however, SVCs serve to connect well known services located in the network to well known clients also connected to the network. These connections are utilized as permanent connections, as they are established and may not be taken down for days, weeks, and months. In many cases, SVCs are established on a permanent basis, whereby they are never taken down and remain up until a network failure occurs.
For example, in LAN Emulation (LANE) and MPOA protocols, which are client/server based protocols, all clients must connect to the server and, once connected, can connect to each other. The connection to the server, however, is permanent, i.e., it is made once and never taken down for reasons other than a network failure, notwithstanding the fact that it was established as an SVC and not a PVC. If these client/server connections go down, they all must be re-established before clients can communicate with each other.
In many instances, it is necessary to rebuild and re-establish network SVC connections from scratch. Such instances include but are not limited to (1) when the topology of a network changes, (2) when a portion of a network is disconnected and connected again, (3) when clients are disconnected and connected again, or (4) when servers are disconnected and connected again. The re-establishment of these connections may involve hundreds, thousands and even tens of thousands or more connections, depending on he size and topology of the network. In most cases, it involves a very large number of connections to recreate, thus consuming a large amount of resources and a long time to complete. The entire reconnection process may consume from a few minutes or many tens of minutes even for very fast networks. Typically, the bottleneck is the signaling protocol between the switches, while the routing algorithm and associated protocol consumes somewhat fewer resources than the signaling. The hardware configuration of the switching fabric within the switch is the least time consuming and occurs relatively quickly since it is mostly a hardware operation.
It would therefore be desirable to have a connection mechanism that could be utilized by a network to create static SVCs, i.e., permanent SVCs, that would be recreated automatically by the nodes along the path in the event the SVC goes down as during a link or node failure.
SUMMARY OF THE INVENTION
The present inve
3Com Corporation
Ho Duc
Hsu Alpus H.
Zaretsky Howard
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