Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Reexamination Certificate
1998-05-28
2001-01-30
Chan, Eddie P. (Department: 2751)
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
C711S118000, C711S154000, C370S395430
Reexamination Certificate
active
06182193
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data communications networks and more particularly relates to a signaling cache suitable for use on network switches such as Asynchronous Transfer Mode (ATM) switches.
BACKGROUND OF THE INVENTION
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.
Asynchronous Transfer Mode
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.
More information on ATM networks can be found in the book “ATM: The New Paradigm for Internet, Intranet and Residential Broadband Services and Applications,” Timothy Kwok, Prentice Hall, 1998.
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.
ATM Signaling
An ATM network is basically divided into two types of entities: users and network element (namely switches). Users can be stations directly connected to the ATM network, edge devices connected to the ATM network, etc. Users request that connections to other users be established using a signaling process. The signaling process occurs between the user and the ATM switch it is connected to via a User to Network Interface (UNI). The switches communicate between themselves via a Network to Network Interface (NNI).
When the user desires to establish a connection, it constructs a request message which includes all the information necessary for establishing the call. In addition, a call reference number is generated which is associated with that particular call. If in the future, the user desires to establish a call to the same destination and having similar call characteristics, the same request message is constructed again but this time a different call reference number is generated.
The ATM switch receiving the request message (termed a SETUP message) functions to parse the message and analyze its contents. The destination is read from the message and a route to the destination is calculated. In addition, resources are allocated using Connection Admission Control (CAC) functions which determine whether a virtual circuit (VC) connection request should be accepted or rejected. The same call request generated previously is then forwarded toward the destination but with a different call reference number. Note that the call reference number is allocated by the local originator of the call request message. Each hop along the route is the local originator for the next hop switch on the call route.
A disadvantage of this scheme is that the processor in the call control portion of the network device on both the user side and the network side may be called on to process essentially the same call request many times. Although the originator of the call requests a call having the same call characteristics but with different call reference numbers, the user device and the ATM switch on the network side perform the same processing again and again regardless of the fact that the processing results are the same.
This is very wasteful in terms of time and processing resources. A case may arise whereby a large amount of calls need to be setup on a periodic basis. For example, the eight o'clock problem arises when large numbers of users log onto the network at the same time. In this case, large numbers of connections are required to be established at the same time. This overburdens the edge devices and results in processing and call establishment delays.
SUMMARY OF THE INVENTION
The present invention overcomes the problems and disadvantages of the prior art by providing a signaling cache suitable for use in any network that utilizes signaling in establishing calls. The signaling cache functions to store the processing results in a cache memory that were obtained in response to the first signaling request message having a particular set of characteristics. Anytime thereafter, if a signaling request having the same characteristics is received, the signaling process is bypassed and the results are fetched from the cache memory. Note that one skilled in the telecommunication arts can apply the present invention to other related processes such routing, resource allocation, etc.
In accordance with the present invention, each switch along the call route functions to perform signaling processing only once for each unique call request. The results of the signaling processing are stored in a cache memory to enable re-use in the event a call request is that matches a previously and processed call request. Signaling processing is performed for each request message having a particular set of characterics, e.g., a set of IEs having a particular value. Anytime thereafter, when a signaling request having the same characteristics is received, the signaling process is bypassed and the results fetched from the cache memory. The signaling cache of the present invention can be applied to other related processes including routing, resource allocation, etc.
There is provided in accordance with the present invention a caching system for use in network devices for reducing the processing burden of call request messages received by a second network device from a first network device, the caching system comprising a first cache in the first network device, the first cache for storing a plurality of first cache indexes, each first cache index having a call group data set associated therewith, a second cache in the second network device, the second cache for storing a plurality of second cache indexes, each second cache index having processing results data and a plurality of third cache indexes associated therewith, means for generating and storing in the cache, a first cache index for each call request having a unique call group value, and for sending the first cache index with the call request to the second network device, means for determining whether the call request has been previously received and if so, retrieving the processi
3Com Corporation
Chan Eddie P.
Kim Hong
Weitz David J.
Wilson Sonsini Goodrich & Rosati
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