Storage and display of historical LAN traffic statistics
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 07/642610, filed on the same date as this application, of Peter C. Notess, entitled Remote LAN Segment Traffic Monitor, and it is related to application Ser. No. 07/642604 filed on the same date as this application, of Peter C. Notess, entitled Maintaining Historical LAN Traffic Statistics, all owned by a common entity. 
     FIELD OF THE INVENTION 
     This invention relates to Computer Systems and more particularly to communications over Local Area Networks within Computer Systems. Even more particularly, the invention relates to collecting statistics on communications traffic being sent over a Local Area Network. 
     BACKGROUND OF THE INVENTION 
     Local area networks (LANs) are designed for high speed data transfer between computers in close proximity. A typical LAN is less than a mile in length, usually within a single building, and transfers data at ten megabits per second. LANs often connect to many computers, and a segment of a LAN may interconnect to other LAN segments forming a network. In order to optimize performance and to isolate errors that occur on a LAN, the data being sent over the LAN needs to be monitored. 
     One way of monitoring the performance of a LAN is to examine all the packets sent on the LAN, classify them into types, and keep records of how many of each type has been sent over a period of time. To monitor the performance of the LAN over time, these statistical records need to be kept and updated periodically to determine how they have changed during the last time interval. 
     Most local area networks have a person assigned to the function of network manager. One of the responsibilities of the network manager is to monitor a LAN to assess performance and isolate errors. The network manager needs to be able to monitor LAN segment traffic on several segments of the LAN and view data from each segment simultaneously. This often cannot be done if the manager needs to attach an instrument to a remote LAN segment, because of the difficulty of finding the LAN cable used by the segment, and the difficulty in finding a location for attaching the instrument. Therefore, a network manager needs to be able to collect statistics from a remote LAN segment and transfer these statistics to a management node, where the statistics are kept for a historical record. 
     One prior art solution to this problem is an instrument called the HP LANProbe. This is a specialized instrument which connects to a LAN segment, collects data from the LAN segment, and transfers this data to a personal computer workstation which displays the data. The personal computer workstation can communicate with many different remote LAN probes. Although the LAN probe instrument maintains some statistical history, it is very limited in duration. Another disadvantage of this solution is that the personal computer can communicate with and display statistics from only one LANProbe at a time, forcing comparative analysis to be done manually. Another disadvantage to this solution is that a dedicated LANProbe instrument must be purchased for each LAN segment to be monitored. 
     Another solution is the traffic program that runs on SUN microsystems workstations. This program allows a remote SUN workstation to gather the statistics and then have these statistics displayed on a local SUN workstation. This system, however, does not keep historical data so the network manager must actually be running the tool at the time data needs to be viewed. Another disadvantage of this solution is that the remote collection point of the statistics must also be a workstation from the same manufacturer. 
     Because of the speeds at which a LAN operates, and the variety of different record types sent over the LAN, there can be a sizable amount of date to save for each sampling of statistics. Also, the sampling rates need to be reasonably fast to get a detailed picture of the LAN operation. The network manager is forced to trade off between sampling slowly enough to cover the desired time interval in the allotted disk space versus sampling often enough to get the desired level of detail. Furthermore, when displaying this data, there are times when the available data needs to be displayed in as much detail as possible, such as for fault diagnosis, and other times when it should be displayed with less detail, such as for trend analysis. 
     There is need in the art then for a system to collect data from several remote LAN segments, and collect this data into a management node for viewing. There is also a need in the art for correlating the data from the various remote nodes onto a single display. Still another need is to combine historical data in a manner that reduces the amount of storage space necessary to retain the data while still retaining the peak sample information of the original data. Yet another need is to display the information on a display that allows easy display of historical data with an ability to show various time windows and resolutions. 
     SUMMARY OF THE INVENTION 
     It is an aspect of the present invention to monitor a local area network (LAN) to collect statistics on the network. 
     It is another aspect of the invention to monitor one or more remote segments of the LAN to collect statistics remotely. 
     Another aspect is to collect and display the remote statistics simultaneously at a single node. 
     Still another aspect is to collect statistics in each of a plurality of remote nodes, send the statistics to a management node where they are correlated and displayed. 
     A further aspect is to display the statistics in a manner that allows viewing of the statistics to start at a user defined point in time. 
     A still further aspect is to display the statistics in a manner that allows viewing of a user defined amount of time. 
     A further aspect is to display the statistics in a manner that allows a user defined resolution of the display. 
     The above and other aspects of the invention are accomplished in a system for collecting and displaying statistical data for a plurality of local area networks, that collects the statistical data in several remote nodes which are each attached to a local area network. The statistical data is transferred to a management node where it is stored in a history file and displayed in a variety of ways. 
     The data is obtained in the remote nodes by using a promiscuous LAN driver that intercepts all records on the LAN, even traffic that is intended for other nodes. These records are sent to a collector process where statistics are accumulated into a shared memory area. An agent process reads the statistics from the shared memory and transfers them to an archiver process in the management node. The archiver process writes the statistics to a history file, compressing the older data in the history file to prevent the file from growing too large. 
     Several display processes running currently in the management node display the history data in various ways, updating the displays in a dynamic, real time, mode. Each time the history file is compressed, the display processes detect the compression and dynamically switch from reading the original file to reading the compressed file. The trend display allows the user to dynamically select the point in time of the data to be displayed, the amount of data displayed at that point, and the resolution of the graph displaying the data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features, and advantages of the invention will be better understood by reading the following more particular description of the invention, presented in conjunction with the following drawings, wherein: 
     FIG. 1 shows an overall block diagram of the system of the present invention; 
     FIG. 2 shows a block diagram of the remote node of FIG. 1; 
     FIG. 3 shows a block diagram of the management node of FIG. 1; 
     FIG. 4 shows a flowchart of the collector process of FIG. 1; 
     FIG. 5 shows a flowchart of the parse packet routine called from FIG. 4; 
     FIG. 6 shows a flowchart of the agent process of FIG. 1; 
     FIG. 7 shows a flowchart of the archiver process of FIG. 1; 
     FIG. 8 shows a flowchart of the interrupt handler of the archiver process of FIG. 7; 
     FIG. 9 shows a flowchart of the load gauge display process of FIG. 1; 
     FIG. 10 shows a screen display for the load gauge process; 
     FIG. 11 shows a flowchart of the traffic distribution display process of FIG. 1; 
     FIG. 12 shows a screen display for the traffic distribution process; 
     FIG. 13 shows a flowchart of the trend display module; 
     FIG. 14 shows a flowchart of the record data accumulation process called from FIG. 13; and 
     FIG. 15 shows a screen display for the trend display module. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description is of the best presently contemplated mode of carrying out the present invention. This description is not to be taken in a limiting sense but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined by referencing the appended claims. 
     FIG. 1 shows an overall block diagram of the system of the present invention. The invention includes several software modules which can run on a multi-tasking operating system, typically the HP-UX operating system. The invention also includes the ability to use many types of statistical collection systems, including work stations, dedicated instruments, or other network elements present in a local area network. Referring now to FIG. 1, a remote node 100 collects statistics which are sent over a communications network 122 to a management node 102. Within the remote node 100, a LAN driver software module 104 receives information from a local area network 103. The LAN driver 104 transfers all the data records (called traffic) received on the LAN 103 to a collector software module 106. The collector module 106 analyzes all the traffic received from the LAN driver 104 and forms statistics based on this traffic. These statistics are then stored in a shared memory 108. The collector 106 and the LAN driver 104 run continuously in the remote node 100 to collect the statistics and store them into the shared memory 108. 
     When requested by the management node 102, an agent software module 110 reads statistics from the shared memory and transfers them over a communications link 122 to an archiver software module 112 within the management node 102. The communications link 122 and the LAN 103 may be the same communications link. The archiver module 112 stores the statistics into a historical file 114. The archiver module 112 also compresses the historical data. Several display modules 116, 118, and 120 display the data from the historical file 114 in various ways. The trend display module 116 displays trends in the historical information, the traffic distribution display module 118 shows how the various record types on the LAN are distributed, and the load gauge display 120 provides an indication of the amount of traffic on the LAN at a given point in time. 
     FIG. 2 shows a block diagram of the remote node 100. Referring now to FIG. 2, a remote node 100 contains a processing element 202 which is connected to other elements of the system over a system bus 204. A keyboard 206 allows a user of the remote node 100 to input data and graphics display 208 allows data to be displayed for the user. A disk 210 contains software and data for use on the remote node 100 and a LAN interface 212 provides the hardware interface to the local area network 103. The LAN interface 212 is used by the LAN driver 104 to obtain data from the LAN 103. A memory 214 contains the software modules and shared memory of the remote node 100. A communications interface 216 is used to send statistical data from this node to the management node over communications link 122. The interface 216 is only necessary if the node 100 does not use the LAN 103 to send the statistical data to the management node 102. The keyboard 206, display 208, and disk 210 would not need to be included in the computer system 100 if the node 100 will not be used for purposes other than collecting LAN statistics. That is, the node 100 may be an independent statistical collection computer system, or the statistical collection system may exist within a node that is also used for other purposes. 
     FIG. 3 shows a block diagram of the hardware of the management node 102. Referring now to FIG. 3, the management node 102 contains a processing element 302, which communicates to other elements of the system over a system bus 304. A keyboard 306 allows the user of the management node, such as the network manager, to input information into the node, and a graphics display 308 allows the statistical information collected by the system to be displayed to the network manager. A disk 310 contains the history file 114, and a LAN interface 312 allows the management node to also connect to a local area network for either communication to the remote nodes or for collecting LAN statistics within the management node itself. A memory 314 contains the archiver module 112 as well as the various display modules, indicated by display module 318 and display module 320. 
     FIG. 4 shows a flow chart of the collector process 106 of FIG. 1. Referring now to FIG. 4, after entry, block 402 opens the LAN driver 104. The LAN driver software 104 is a standard local area network interface module modified only to return all records sent over the LAN, not just to return records for this particular node. This modification allows the collector software to collect statistics for all nodes connected to the local area network, not just the node in which it resides. 
     After opening the LAN driver software, block 403 creates a shared memory key for access to shared memory. Block 404 then creates a shared memory segment (108 of FIG. 1) and associates the shared memory key with the shared memory segment. The agent process 110, described below, uses the same shared memory key to allow it to access the shared memory 108. Block 406 then sets up a series of signal handlers, to allow the collector process to handle all interrupts that might occur while it is collecting data. Block 408 then calls the LAN driver software 104 to turn it into promiscuous mode, where it will collect all records transmitted on the LAN. Prior to being set into this promiscuous mode, the LAN driver software would ignore records not intended for this particular node. Block 410 then stores the time of day in shared memory so that the agent process 110 will know the time at which collection of data was started. 
     Block 412 waits until a buffer of data is available from the LAN driver 104 and it then reads the buffer. Block 414 calls FIG. 5 to process the packets of data in the buffer and assemble the statistics. After return from FIG. 5, block 414 transfers back to block 412 to read the next buffer. This loop continues until the collector process is canceled by the user of the system. The collector process does not terminate by itself, but must be canceled by the user of the system. 
     FIG. 5 shows a flow chart of the parse packet routine called from FIG. 4. After entry block 502 determines whether there are more packets available in the buffer passed from FIG. 4. If there are more packets available, block 502 transfers to block 504 which gets the next packet that was collected from the LAN driver module 104. Block 506 then updates the packet count and byte counts in the shared memory 108. The shared memory 108 contains a counter for the total number of packets transmitted across the LAN 103, and also a counter for the total number of bytes from all the packets. Block 508 then determines the packet length and updates counters for various lengths. The collector process 106 maintains separate counters for packets having lengths of up to sixty four (64) bytes, sixty five (65) to one hundred forty (140) bytes, one hundred forty one (141) to five hundred twelve (512) bytes, five hundred thirteen (513) to twelve hundred (1200) bytes, and a counter for packets larger than twelve hundred (1200) bytes. These counters are used to display data in the traffic distribution display described below. 
     Block 510 then updates broadcast or multicast counters in shared memory if the packet is for a broadcast or multicast record. Block 512 then determines whether the packet is for an ETHERNET local area network or for an IEEE 802.3 local area network. If the packet is for an ETHERNET local area network, block 512 transfers to block 514 which updates a set of ETHERNET counters depending upon whether the packet is an IP, ICMP, TCP, UDP, or ARP packet. If the packet is for an IEEE 802.3 network, block 512 transfers to block 516 which updates a set of IEEE 802.3 counters depending on whether the packet is a IP packet, ICMP, TCP, or UDP packet. After updating these counters control transfers back to block 502 to process the next packet in the buffer. After all packets in the buffer have been processes, block 502 returns to FIG. 4. 
     FIG. 6 shows a flow chart of the agent process 110 of FIG. 1. The agent process 110 is responsible for copying the statistics from the shared memory 108 and returning those statistics to an archiver process in a management node. This is accomplished when the archiver process from the management node requests the statistics be collected. Therefore, the flow chart of FIG. 6 is entered when a request is received from an archiver process. Referring now to FIG. 6, after entry, block 602 creates a shared memory key for accessing the shared memory 108. This key must be identical to the key created by the collector process 106, as described above with respect to FIG. 4. Block 604 points to the shared memory and block 605 waits for a request for the data from the management node. When a request is received, block 606 determines whether the shared memory is valid. The shared memory will be valid if the collector process is currently running but may be invalid if the collector process has been canceled. If the shared memory is not valid, block 606 transfers to block 608 which detaches shared memory and then block 610 tries to reattach shared memory to obtain a different area. If the collector process has been stopped and restarted, it may be collecting data into a new shared memory area, and block 610 attempts to reattach to the new shared memory area. Block 610 then transfers to block 612 which determines whether the new area is valid and if the shared memory area is valid, control transfers to block 616. If the new memory area is not valid, block 612 transfers to block 614 which sends an error indicator back to the archiver process and returns. 
     If the shared memory area is valid, control transfers to block 616 which gets the current time of day. Block 618 then copies the shared memory data to a requestor buffer so that it can be sent back to the requesting archiver process. Block 620 then copies the time of day to the requestor buffer. Since the collector process placed the statistics collection start time of day into shared memory, and the agent process returns the time of day that the statistics were collected, the archiver process can compute the duration for this set of statistics. After the data and time of day have been placed into the requestor buffer, block 622 returns the buffer to the requestor and then transfers to block 605 to wait for the next request. 
     FIG. 7 shows a flow chart of the archiver process 112 of FIG. 1. Referring now to FIG. 7, after entry, block 702 gets the name of the history log file from the parameter list. Block 704 then creates a name, based on the history log file name, to use for compressing the log file. Block 706 determines whether the data for the log file will be transferred from a remote node or from the shared memory of the management node. If the data will be from a remote node, block 706 transfers to block 708 which creates a link to the remote node. After linking to the remote node, or if data will be obtained from the shared memory of the local node, block 706 transfers to block 710 which sets up the signal handler to handle interrupts, and it also sets up a periodic interrupt, typically one per second, which determines the periodic sample rate. Block 712 then points to memory shared with the interrupt handler in order to access the compress flag, and block 714 determines whether there is a need to compress the history file. If there is a need to compress the history file, block 714 transfers to block 716 which performs the compression. FIG. 7 then loops while checking for the need to compress the history log file, while the interrupt handler receives data and stores in the history file. Once per hour the interrupt handler will set a flag indicating a need to compress, block 714 will detect this need and perform the compression. 
     FIG. 8 shows a flow chart of the interrupt handler for the archiver process 112. This flow chart is entered periodically (as set up by block 710 of FIG. 7) to obtain data from the remote node or shared memory of the management node. Referring now to FIG. 8, after entry, block 802 determines whether an hour has passed since the last compression of the history file. If at least one hour has passed, block 802 transfers to block 804 which sets a flag in shared memory to indicate to FIG. 7 that file compression is needed. After setting the indicator in memory or if less than one hour has passed, control transfers to block 806 which determines whether data is being collected from a remote node. If data is being collected from a remote node, block 806 transfers to block 808 which sends a request to the remote node for the data. Block 809 then waits for the data to arrive, and after the data arrives, block 809 transfers to block 812. 
     If data is being obtained from the local node, block 806 transfers to block 810 which gets a snapshot of the local data in the shared memory of the management node. Block 812 then determines whether the data has changed since the last snapshot and, if not, block 812 simply returns. If data has changed since the last snapshot, block 812 transfers to block 814 which writes a new record to the history file. 
     FIG. 9 shows a flow chart of the load gauge display process 120 of FIG. 1. This process resides in memory of the management node and runs concurrently with the archiver process and the other display processes. Referring now to FIG. 9, after entry, block 902 opens the history log file, block 903 seeks to the last record in the file, and block 904 gets the last record from the file. Block 906 then re-computes the moving average to account for the data just read and block 908 determines whether the peak data just read is larger than the stored peak for the display. If the peak data just read is larger, block 908 transfers to block 910 which stores this new peak data for the display. Control then transfers to block 914 which displays the load gauge data on the display, as shown and described with respect to FIG. 10 below. Block 914 then transfers to block 916 which determines whether the history file has changed since the last read. If the file has not changed since the last read, block 916 transfers back to itself, therefore, block 916 simply waits until a new record has been written to the history file. In this manner, the load gauge display is dynamically updated to a user watching the display screen of the management node. 
     When the history file changes, block 916 transfers to block 920 which determines whether the file size of the history file has been truncated to the length of an integer in the current system, typically four (4) bytes. When the archiver process compresses the history file, it does so by copying the current history file to a new history file during the compression. After the compression is complete, the archiver process reduces the length of the current history file to the length of an integer, and in this integer it places the number of records removed from the new history file. This number is then used to locate the original record position in the new file. Therefore, if the history file length has been reduced to the length of an integer value, the load gauge process of FIG. 9 knows that a compression has occurred and transfers to block 924 to close the current history file and reopen the new history file to access the current data. If the file size is not equal to an integer, the history file has not been compressed so block 920 transfers to block 904 which reads the new data, computes new averages and peak values and then transfers back to 914 to display these new values. 
     FIG. 10 shows a screen display for displaying the load gauge data collected and displayed by FIG. 9. Referring now to FIG. 10, a load gauge display 1002 shows three different information values which are accumulated by the process of FIG. 9. The solid bar 1004 shows the load over the last sampling interval. The hollow arrow 1006 shows the peak data and the solid arrow 1008 shows the moving average of the data over the last one minute. All this data is displayed on a quadratic scale 1009. 
     The example display shown in FIG. 10 is for a windows environment, therefore, graphic display buttons 1010, 1012, and 1014 are available to allow the user to close the display, reset the accumulated values, or reconfigure the load gauge display process, respectively. 
     FIG. 11 shows a flow chart of the traffic distribution process 118 of FIG. 1. The traffic distribution process 118 runs concurrently with the archiver process and the other display processes within the management node. Referring now to FIG. 11, after entry, block 1102 opens the history log file, block 1103 seeks to the last record in the file, and block 1104 reads the last record from the log file. Block 1106 then computes the average percentages, and block 1108 computes the percentages for the record lengths over the last ten seconds. Block 1112 then displays the traffic distribution data on a display, which is shown in FIG. 12 and described below. Block 1114 then determines whether the history file has changed since the last read and, if not, block 1114 simply waits for the file to change. In this manner, the traffic distribution display is a real time display and dynamically updates the display on the management node. When the history file changes, block 1114 transfers to block 1118 which determines whether the file size of the history file has been reduced to the length of an integer value. As discussed above with respect to FIG. 9, this reduction in length occurs when the archiver process compresses the history file. If the length has been reduced, block 1118 transfers to block 1122 which reopens the history file in order to access the new, compressed, history file. If the file size is not equal to an integer, block 1118 transfers to block 1104 which reads the last record, computes the new percentages, and then transfers back to block 1112 to display the new percentages. 
     FIG. 12 shows an example display for the traffic distribution data collected and displayed by the process of FIG. 11. Referring now to FIG. 12, a traffic distribution display 1202 contains five gauge displays similar to the gauge display of FIG. 10. Each of the five gauge displays of FIG. 12 shows a distribution for one of the record lengths accumulated in the process of FIG. 11. Within each of the gauge displays, the vertical bar shows the percentage of packets of the indicated length that have occurred in the last ten seconds, and the arrowhead shows the percentage of packets of that length that have occurred since the date and time indicated on the left side of the display. For example, the bar 1204 shows the percentage of packets of length Twelve Hundred One (1201) bytes to Fifteen Hundred Eighteen (1518) bytes that have occurred in the last ten seconds and the arrowhead 1206 shows the percentage of packets of length Twelve Hundred One (1201) to Fifteen Hundred Eighteen (1518) since the date and time indicated on the left side of the display. 
     FIG. 13 shows a flow chart of the trend display module 116 of FIG. 1. This module shows the data from the history file 114 displayed in a manner that allows the user to control the time for which the data is displayed, that is, the user may easily select any point within the history file for the data to display; the user may select the amount of data displayed around the point in history, that is the user might choose to display one day, one week, etc.; and the user may select the resolution of the data being displayed. An example of data being displayed by the trend display module 116 will be described below with respect to FIG. 15. 
     Referring now to FIG. 13, after entry, block 1302 opens the history log file for display. Block 1304 gets the history slider information from the windowing system (see HISTORY slider control 1502 of FIG. 15), and computes the end point in the file for the history display. The history slider always controls the last data in the file to be displayed, and when positioned at the right end of the horizontal bar (see FIG. 15) the most current data will be displayed and dynamically updated as new data becomes available. Block 1306 then gets the zoom slider information from the windowing system (see ZOOM control 1504 of FIG. 15) and computes the start point in the file. The zoom slider controls the amount of data being displayed at any one time, therefore, in conjunction with the history slider which defines the end point of the data, the zoom is used to compute the starting point of the data from the history file. Block 1308 then gets the resolution slider (see RESOLUTION control 1506 of FIG. 15) and computes the amount of time being displayed per display interval on the display. Block 1310 then resets counters to start accumulating the data for the first point on the display and block 1311 moves the file pointer of the history file so that it points to the record containing data for the first point to be displayed. Block 1312 then gets the next history record to be processed. Block 1314 calls FIG. 14 to process the history file record and display any data points included in the record. Block 1316 determines if there are more records to be processed and if there are it transfers control back to 1312 to get the next record. If there are no more records to be processed at this time, block 1316 transfers to block 1318 which determines whether any of the three sliders, that is the HISTORY slider, ZOOM slider, or RESOLUTION slider (FIG. 15) have changed. If any of the sliders have changed, block 1318 transfers to block 1304 to update the sliders and get new information. If none of the sliders have changed, block 1318 transfers to block 1319 to determine if the history slider has been set to &#34;NOW&#34;. If the history slider has been placed in the &#34;NOW&#34; position (see FIG. 15) the trend display will update the display dynamically as new data is placed into the history file. Therefore, if the slider is in the &#34;NOW&#34; position, block 1319 transfers to block 1320, otherwise it transfers to block 1318 to loop. Block 1320 checks the history file to determine if the file has changed since the file was last read. If the file has not changed, block 1320 transfers back to 1318 and waits for new data or a slider change. If the file has changed, block 1320 goes to block 1322 which gets the file size of the history file. Block 1324 then determines whether the file size of the history file is the same as the size of an integer data value on the computer node 102. 
     When the archiver process 112 (FIG. 1), compresses the history file, it creates a new file and copies the compressed data to the new file. After the copy is complete, it puts the number of changes made into the original history file as an integer value, and it truncates the old file to the length of a single integer value. Therefore, if the file size of the history file is equal to the length of an integer, the file has been compressed and block 1324 transfers to block 1326 which reopens the history file to point to the new, compressed, history file and obtain new data. After reopening the history file, block 1326 transfers back to block 1322 to repeat the process until a file having a size larger than an integer is found. When the file size is not equal to an integer, block 1324 transfers to block 1312 to process the new history file. 
     FIG. 14 shows a flow chart of the process record and display data process called from FIG. 13. This flow chart will process one record of data from the history file, and accumulate that data for display as a data point. If an entire data point is assembled while processing the record, the flow chart of FIG. 14 will display the data point and start the accumulation of the next data point. Referring now to FIG. 14, the variable TIME will be used to determine whether all the data for a data point has been collected. After entry, block 1404 then determines whether the starting time for the data point being collected is less than the starting time of the record being processed. If the point starting time is less than the record starting time, block 1404 transfers to block 1406 which determines whether the ending time for the data point being accumulated is less than or equal to the starting time of the record being processed. If the ending time of the data point is less than or equal to the record start time, no data from this record applies to the point being collected, therefore, block 1410 sets the value of time to the total time of the point, which will cause this point to be displayed and accumulation of data for the next point to be started. Block 1411 then adds TIME to the point start time and block 1412 determines whether the value of TIME is greater than or equal to the total time being accumulated for the point. If TIME is greater than the point time, block 1412 transfers to block 1414 which displays the point and resets the counters for the next point. 
     If the end time of the point being accumulated is greater than the record start time, some of the record applies to the data point, therefore, block 1406 transfers to block 1408 which sets TIME to the time between the start of the point and the start of the record. Block 1408 then transfers to block 1411 to continue processing. This causes the first part of a point to be skipped since no data is available for it. 
     If the starting time for the point is greater than or equal to the record starting time, block 1404 transfers to block 1416. Block 1416 determines whether the starting time of the point is greater than or equal to the ending time of the record. If the point start time is greater than or equal to the record end time, then this record is completely processed and block 1416 returns to FIG. 13. 
     If the start time of the point is less than the record end, some data within this record needs to be processed and block 1416 transfers to block 1418 which determines whether the end time of the point being accumulated is less than or equal to the record end time. If the point end time is less than or equal to the record end time, then this record contains all the remaining data for the point so block 1418 transfers to block 1420 which sets the value of TIME to the entire time for this point, which will cause the point to be displayed after the data is accumulated. Block 1420 then transfers to block 1424 which adds the appropriate data from this record to the data being accumulated for the point and then transfers to block 1411 which accumulates data and displays the point. 
     If the point end time is greater than the record end time, then the remaining portion of this record needs to be processed so block 1418 transfers to block 1422 which sets the variable TIME to the remaining time of this record. Block 1424 then adds the record data to the point data and transfers to block 1411 which adds the time to the point start time. Block 1412 then determines if the value of the variable time is greater than or equal to the time for this point, and if it is, block 1412 transfers to block 1414 which displays the points and resets the counters for the next point being accumulated. 
     FIG. 15 shows a diagram of a screen display for the trend module 116 of FIG. 1. Referring now to FIG. 15, a HISTORY slider display 1502 allows a user of the trend module to determine the time of the data within the history file that will be displayed. Specifically, slider 1502 determines the end time of the data to be displayed. Moving the slider icon 1503 to the left (this movement is done using a pointing device such as a mouse within the windowing system environment of the present invention) causes earlier data to be displayed, and moving the slider 1503 to the right causes later data to be displayed. Moving the slider 1503 all the way to the right causes the most current data to be displayed, and will cause the display to be dynamically updated as additional data is placed into the history file. 
     A ZOOM slider 1504 allows a user to set the amount of data to be displayed at the time. Moving the slider icon 1505 to the right will cause less data to be displayed and moving the slider 1505 to the left will cause more data to be displayed. RESOLUTION slider 1507 determines the amount of data intervals to be displayed in the graph. Moving the slider 1506 to the left displays less resolution, that is data is &#34;smoothed&#34; more before being displayed and fewer display intervals are shown on the graph, and moving the slider 1506 to the right shows more resolution, that is, more data display intervals are displayed on the graph. 
     Line chart 1508 shows an example of data being displayed. Scale 1510 shows the resolution of data on the y-axis, and scale 1512 shows the resolution of data on the x-axis. Dot 1514 indicates that the packet/message rates are being shown. A user could use a pointing device to fill in dot 1516 to cause the system to shows kilobyte data rates. 
     Having thus described a presently preferred embodiment of the present invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and circuitry and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the present invention. The disclosures and the description herein are intended to be illustrative and are not in any sense limiting of the invention, more preferably defined in scope by the following claims.