Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of network traffic generation and more particularly to the field of network traffic generation for different scales of operation. 
     2. Description of the Related Art 
     Traffic generation for packet switched networks refers to the injection of artificially generated packet streams into a target network with a traffic pattern according to a stochastic specification or trace. Typically, traffic generation supports the testing of a network application or an underlying network under exemplary load conditions to determine application or network response characteristics to the load. Synthetic traffic generation based upon a stochastic specification enables the creation of arbitrary workloads for a network, while trace-based traffic generation allows for the reproduction of a known traffic pattern. Notably, traffic generation facilitates the testing and study of the performance characteristics of a network application or system without incurring the substantial cost of hard and soft equipment and human testers that otherwise would be required. 
     Network traffic is known to be bursty in nature. Traffic burstiness has been defined as the tendency of data packets to arrive in bursts, with the inter-packet arrival time within the burst being much smaller than the average inter-packet arrival time. Bursty traffic can have a significant effect on the queuing delays and response times of a network application or network system. As such, an appropriate measure of burstiness can serve as an important traffic parameter describing the variability in load intensity and packet arrival rate in a network system. 
     Bursty network traffic historically has been characterized as Poisson distributed and the modeling, analysis and the design parameters of traffic generation systems tend to abide by this assumption. Notwithstanding, recent studies indicate that network traffic not only is bursty in nature, but also network traffic has been found to be self-similar in nature. Self-similarity as described in the seminal paper, Leland, Taqqu, Willinger and Wilson,  On the Self - Similar Nature of Ethernet Traffic , in IEEE/ACM Transactions on Networking, vol. 2, no. 1 (February 1994), is a process displaying structural similarities across a wide range of scales of a specific dimension. In other words, the reference structure repeats itself over a wide range of scales of diverse dimensions (geometrical, or statistical, or temporal), and the statistics of the process do not change with the change. 
     Burstiness in self-similar network traffic most often has been modeled according to a Markov modulated Poisson process (MMPP). The MMPP model describes two exponentially distributed states: idle and bursty. The transition from the idle state to the bursty state in the MMPP model depends upon the size of the required bursts which can be constant or exponentially distributed. To produce network traffic according to the MMPP model, one need only specify three parameters: interpacket gap (IPG), packet size and the size of the burst. A fourth, optional parameter can be specified as a “spread” to increase the variability of the generated data as it is well known in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention address deficiencies of the art in respect to traffic generation for self-similar network traffic and provide a novel and non-obvious method, system and computer program product for multi-scale network traffic generation. In one embodiment of the invention, a network traffic generation method can be provided. The method can include defining multiple, different scales in an n-state MMPP model to accommodate a full characteristic response of a modeled traffic scenario by comparing in the transition matrix a random probability distribution to the transition window to determine the state. The method further can include establishing a transition window for each of the scales and determining a state through the transition window for selected ones of the scales. Finally, the method can include computing an inter-packet time according to the determined state for each of the selected ones of the scales and generating and transmitting packets for the selected ones of the scales utilizing a correspondingly computed inter-packet time. 
     In another embodiment of the invention, a network traffic generation data processing system can be provided. The system can include an MMPP model and a packet scheduler coupled to the MMP model. The system further can include a data store of transition windows defined for different defined scales and traffic generation parameter computing logic. The traffic generation parameter computing logic can include program code enabled to compute traffic generation parameters for different scales according to respective states identified within different transition windows in the data store for the different scales. Finally, the system can include a packet transmitter coupled to the packet scheduler. 
     Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. The embodiments illustrated herein are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown, wherein: 
         FIG. 1  is a pictorial illustration of a computer communications network configured with a multi-scale, multi-window network traffic generator; 
         FIG. 2  is a schematic illustration of a multi-scale, multi-window network traffic generator; 
         FIG. 3  is a block diagram illustrating a multi-scale, multi-window network traffic generator; and, 
         FIG. 4  is a flow chart illustrating a process for the multi-scale, multi-window generation of network traffic. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention provide a method, system and computer program product for multi-scale, multi-window network traffic generation. In accordance with an embodiment of the present invention, a multi-scale, multi-window network traffic generator can simulate the self-similar characteristics of an inter-arrival time distribution for packets simulated for arrival across multiple time scales. The traffic generator can operate upon an adapted, n-state MMPP model with transition windows to identify state transitions in each of the time scales. Specifically, each of the transition windows can map a gap between multiple scales of a self-similar inter-packet time distribution to facilitate the selection of parameter values when generating packets within a particular time scale. 
     In illustration,  FIG. 1  is a pictorial illustration of a computer communications network configured with a multi-scale, multi-window network traffic generator. The system can include one or more client computing devices  120  coupled to a server host  110  over a computer communications network  130 . The server host  110  can include a multi-scale, multi-window network traffic generator  140  configured to generate packets  170  emulating the self-similar nature of network traffic. An application  150  further can be coupled to the server host  110  (or to another server host) and an application monitor  160  can monitor the performance characteristics of the application  150  in response to the packets  170  of the network traffic generated by the multi-scale, multi-window network traffic generator  140 . 
     The multi-scale, multi-window network traffic generator  140 , as shown in  FIG. 2 , can include a control point  210  coupled to each of an MMPP model  240 , parameter computation logic  220  and a packet transmitter  260 . The MMPP model  240  in turn can be coupled to a packet scheduler  250  also coupled to the transmitter. The MMPP model  240  can include a multiplicity of states, each calibrated to represent a scale range in a time range. Each state can be exponentially distributed with transition probabilities for transitioning from an idle state to a burst state, and from a burst state to an idle state. 
     The transition probabilities can be organized into a probability transition matrix and when provided a desired traffic pattern, the matrix can produce a selected one of the transition windows  230  for use generating real-time network traffic. In this regard, the parameter computation logic  220  can compute an inter-arrival time for each of the burst of bursts that varies from one burst of bursts to the next. In this regard, multiple transition windows  230  can be provided as τ i =[ρ min   i ,ρ max   i+1 ], each iteration of the multiple transition windows  230  providing for three possible cases: (1) ρ i &gt;ρ min   1  in consequence of which a packet is to be generated with an inter-packet time in the bursty state; (2) ρ i &lt;ρ max   2  in consequence of which a packet is to be generated with an inter-packet time in the idle state; and ρ max   2 &lt;ρ i &lt;ρ min   1 —the gap between two states within the transition window in consequence of which no packet is to be generated. 
     Thus, each of the transition windows  230  can generate packets with an inter-packet time distribution determined by the parameters μ 1 , μ 2 , . . . , μ n  corresponding to each of the states P 1 , P 2 , . . . P n  where μ is the mean parameter and P is the distribution for a burst of bursts. Each burst of bursts can be scheduled within the packet scheduler  250  for a different scale of self-similar traffic and transmitted by the transmitter  260  into the target network. Thereafter, the pattern of burst of bursts can repeat for the number of scales selected. 
     In more particular illustration,  FIG. 3  is a block diagram illustrating a multi-scale, multi-window network traffic generator. As shown in  FIG. 3 , the traffic generator can include a burst generator  320  driven from a spread generator  310  which provides for variability within a packet burst  340 . A burst window generator  330  further can be provided that can define the duration (width) of a packet burst  340 . Finally, one or more idle state generators  350 A,  350 B,  350 N can provide one or more idle state generators  360 A,  360 B,  360 N that provide idle state gaps for n-scales of long-range dependent traffic in a packet burst  340 . More importantly, each of the idle state generators  360 A,  360 B,  360 N provide the mean parameters with some variability included for realism and the probability distribution for the packet burst  340 . 
     In even yet further illustration,  FIG. 4  is a flow chart illustrating a process for the multi-scale, multi-window generation of network traffic. Beginning in block  405 , a first scale can be selected for processing. In block  410 , a transition window can be defined for the scale. In decision block  415 , if additional scales remain to be processed, in block  420  a next scale can be selected for processing an a new transition window can be established for the next scale. This portion of the process can repeat until a set of transition windows have been established for the desired set of scales. Thereafter, the process can continue through block  425 . 
     In block  425 , a scale within the set of scales can be selected for processing. In block  430 , a window can be retrieved for the selected scale and in block  435 , a state can be determined according to the retrieved window. Thereafter, in block  440 , the packet generation parameters can be generated for the determined state and in block  445 , a burst of bursts can be generated utilizing the parameters. Finally, in block  450  the burst of bursts can be transmitted and in decision block  455 , if the process has not completed, in decision block  460  it can be determined whether to change scale. If so, a new scale can be selected in block  425  and the process can repeat through block  430 . When no additional traffic is to be generated, the process can terminate in block  465 . 
     Embodiments of the invention can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, and the like. Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. 
     For the purposes of this description, a computer-usable or computer readable medium can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD. 
     A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters.

Technology Category: 5