Abstract: A network monitoring system and method for analyzing network traffic is provided. This network monitoring system and method employ flow monitoring to analyze the traffic flow inside a switching device. All message packets entering the switching device are filtered and then sampled. After message packets are sampled, the switching device generates reporting packets containing network information related to the sampled packets. These reporting packets are then transmitted to a monitor server for analysis. Generally, the monitor server is coupled to a number of the switching devices so that the overall performance of the network can be gathered and presented to the users.

Abstract: An admission control system for a server including an admission controller that receives a stream of messages from one or more clients targeted for the server. The admission controller relays to the server the messages in the stream that correspond to a number of sessions already underway between the clients and the server. The admission controller also relays to the server the messages in the stream that do not correspond to sessions already underway if a hybrid and predictive admission control strategy using information provided by a resource monitor indicates that additional sessions can be handled by the server. The admission controller defers the messages otherwise.

Abstract: A session based resource control system for a server including a resource controller that receives a stream of arriving messages from one or more clients targeted for the server. The resource controller relays to the server the messages and a corresponding resource share for each message as a stream of resource allocated messages. The resource share is based on the resource rate for that session as determined by a resource monitor. The server then processes each message in accordance with its resource share and generates a stream of completed messages. The objective is for the resource control system to achieve fairness whenever there is contention for resources between or amongst the sessions.

Abstract: A session based resource control system for a server including a resource controller that receives a stream of arriving messages from one or more clients targeted for the server. The resource controller relays to the server the messages and a corresponding resource share for each message as a stream of resource allocated messages. The resource share is based on the resource rate for that session as determined by a resource monitor. The server then processes each message in accordance with its resource share and generates a stream of completed messages. The objective is for the resource control system to achieve fairness whenever there is contention for resources between or amongst the sessions.

Abstract: A network monitoring system having a router for generating flow records and a monitor device for filtering flow records, extracting internet address information of the remote hosts from the flow records and performing active tests on selected remote hosts. For at least some data packets, the router sends a flow record of the data packet to the monitor. Each flow record contains address, port, and subnet information of the filtered data packet. Based on the information provided by the flow records, the monitor can perform active tests on the selected remote hosts.

Abstract: A system for and method of sending network problem information along a communication path of a network having an unknown configuration and inaccessible components including a first device for observing network problems and a second device for relieving network problems. Upon observation of a problem, the first device generates and sends an enhanced loopback test message to the source of the problem. The enhanced loopback test contains information regarding the source and the nature of the problem. The second device, being along the path of the loop between the first device and the source, receives the problem information and responds by reducing the problem as appropriate.

Abstract: The network monitoring system includes a monitor device coupling to a network switch through a mirror port interface of the network switch. The network switch supports a number of regular port interfaces connected to different network components and the mirror port connected to the monitor device. The mirror port mirrors all network traffic of any selected regular port interfaces of the network switch. When the monitor device receives a data packet from the network switch, the monitor device extracts the network address information from such as the source and destination address from the data packet. The monitor device then examines internal lookup tables to determine whether there are corresponding physical port interface for the network address information. If the corresponding physical port interfaces for the network address information are not available in the lookup table, the monitor device interrogates the network switch for the corresponding physical port interface.

Abstract: An admission control system for a server including an admission controller that receives a stream of messages from one or more clients targeted for the server. The admission controller relays to the server the messages in the stream that correspond to a number of sessions already underway between the clients and the server. The admission controller also relays to the server the messages in the stream that do not correspond to sessions already underway if a hybrid and predictive admission control strategy using information provided by a resource monitor indicates that additional sessions can be handled by the server. The admission controller defers the messages otherwise.

Abstract: An admission control system for a server including an admission controller that receives a stream of messages from one or more clients targeted for the server. The admission controller relays to the server the messages in the stream that correspond to a number of sessions already underway between the clients and the server. The admission controller also relays to the server the messages in the stream that do not correspond to sessions already underway if a hybrid and predictive admission control strategy using information provided by a resource monitor indicates that additional sessions can be handled by the server. The admission controller defers the messages otherwise.

Abstract: This disclosure provides a transparent load direction mechanism between multiple host computers that enables continued processing of client requests notwithstanding failure of individual host computers. A client computer system is provided with two URLs for a given web site, including a primary URL and a reference URL; the reference URL is the generic address for the web site, and is used for bookmarks and URL display, e.g., "www.website.com;" the primary URL is used for actual communication with an assigned one of several parallel servers which service the web site, i.e., "www.website4.com." The client computer normally directs communications to the assigned server, but if a failure condition is detected, i.e., server "website4" goes off-line, the reference URL is used for re-entry to the web site and a new server assigned to service the client computer (i.e., "www.website2.com").

Abstract: This disclosure provides for admission control with multiple classes of service and priority processing. An admission control system preferably admits incoming messages which are part of a session-in progress. As to messages representing new sessions, the admission control system admits such messages on the basis of priority or class assigned to them, or otherwise discriminates between messages stored in a message queue based on priority. In a preferred embodiment, if server resources become strained, the admission control system can defer messages in order of lowest priority or if allocated class resources have been exceeded. In one embodiment, messages are assigned different status for two web site providers paying for different levels of service available, such that as server resources become stretched, one web site will receive better quality of service than the second web site.

Abstract: This disclosure provides for admission control having enhanced quality of service. A server-resident admission control system implements measurement-based admission control to determine whether a requested web site is available to process a new session. If the site is not available, based upon current resources and defined load parameters, the server-based system determines when the associated server can later provide preferred access to the client, and transmits to the client an indication of that time, together with a key. One example uses a downloaded web page to automatically cause a client browser to later automatically access the host, and to display a message indicating that the client has preferred access together with a countdown time. As an alternative, a program file can be stored on the client which is effective to launch the client's web browser and to direct access to the particular host at the appointed time, irrespective of whether the client's browser is active.

Abstract: A method for operating a computer system having a plurality of software modules which interact with each other by sending and receiving messages. The computer includes a user interface which receives commands from a user and displays information to the user in response to those commands. The computer system is characterized by a latency time defined to be the time between the issuance of a command by the user and the receipt of information specified in the command. The messages received by at least one of the modules include messages for that module and messages that are to be passed to other modules. In the present invention, at least one of the modules is provided with code for recognizing a Latency Event which includes a message for that module that would not normally be received by that module if the computer system had a latency time of zero. This code also contains code for storing information specifying that a Latency Event was received by that module.

Abstract: A network analysis method is applied to traffic data collected in respect of a network of the type comprising a plurality of logical segments each with a plurality of nodes. The method involves processing the traffic data by preferentially removing traffic associated with nodes identified as acting as global servers, and using the remaining traffic to identify nodes acting as local servers. Upon the local servers being identified, the network analysis method carries out further processing to make suggestions as to whether any of these local servers should be moved to another logical segment and as to whether it would be worthwhile splitting a segment between two associated local servers.

Abstract: By sampling the initial result of a query to the database, thereby producing a sampled result which is substantially smaller than the initial result, the sampled result is easier to analyse statistically and is easier to transmit across a communications medium such as a network.

Abstract: In order to monitor the status of a system in the form of a communications network, such as a computer local area network (LAN) 10 or an SS7 telecommunications signalling network, measurements are made of various operating parameters for each domain (S1 . . . S14) or segment of the network. The measurements for each parameter are scaled in accordance with a respective piecewise-linear scaling function (300) for that parameter, so that all scaled measurements for all parameters have values in a range from 0 to 3, values of 1 and 2 corresponding to threshold values T.sub.1 and T.sub.2 of interest. An extreme scaled value, such as the maximum or minimum value, is selected for each parameter, and plotted on a respective one of multiple radially-extending axes (301-306), each of which is associated with a respective parameter. The plotted values are connected to form a polygonal figure (309).

Abstract: In order to monitor the status of a system in the form of a communications network, such as a computer local area network (LAN) 10 or an SS7 telecommunications signalling network, measurements are made of various operating parameters for each domain (S1 . . . S14) or segment of the network. The measurements for each parameter are scaled in accordance with a respective piecewise-linear scaling function (300) for that parameter, so that all scaled measurements for all parameters have values in a range from 0 to 3, values of 1 and 2 corresponding to threshold values T.sub.1 and T.sub.2 of interest. An extreme scaled value, such as the maximum or minimum value, is selected for each parameter, and plotted on a respective one of multiple radially-extending axes (301-306), each of which is associated with a respective parameter. The plotted values are connected to form a polygonal figure (309).

Abstract: A network analysis method for use in relation to a network having a plurality of entities, each with associated traffic, involves an analysis task comprising the steps of monitoring the network to collect data on entity traffic for a period of network operation, analyzing this data in respect of an entity operational characteristic by which the entities may be ordered into a ranking, forming an end set of at least one entity at one end of said ranking, and storing the identity of the or each entity making up that end set.

Abstract: In packet-based networks (10), it is often desired to test communications between two specific stations (11, 12). This can generally be effected from a first one of the stations (11) by requesting the other station (12) to `loop-back` a test packet sent from the first station. The first station (11), on receiving back the test packet, can thereby ascertain that not only is communication with the other station (12) possible, but it can also measure the round trip time. However, more complex characteristics of the transmission path between the stations (11, 12) are not ascertainable in this manner. The transmission of a predetermined sequence of packets permits such characteristics to be determined by observing the effect of the network (10) on the sequence considered as a whole. Thus by varying packet size in a sequence, characteristics such as bandwidth, propagation delay, queuing delay and the network's internal packet size can be derived.

Abstract: A method is provided for ascertaining topology features of a network comprising a plurality of sub-networks, spanning devices interconnecting the sub-networks, and stations operative to source and/or sink traffic to/from the sub-networks. The traffic is in the form of discrete message packets each including source and destination information. Traffic on each of the sub-networks is monitored by a respective monitoring device and a partial traffic matrix is built up for each sub-network. These partial traffic matrices are then analyzed by a central processing station to determine, for example, the association of stations within the with sub-networks, and the interconnection of sub-networks by spanning devices.