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MTSW-107-09-L-D-006-RA

来源:LM317 Electronics Components编辑:FLIR时间:2021-06-15 15:05:00

This is indicated in Figure 3.

SysML is designed to work with two evolving interoperability standards: the OMG XMI 2.1 model interchange format and the ISO AP233 data interchange standard. Either of these, said Artisan's Moore, could transfer high-level design information expressed in a SysML modeling tool into a hardware design tool.

But will any such links be forged? As of now, the providers of SysML tools come from the embedded-software world. EDA vendors have shown little interest in UML or awareness of SysML. If SysML is going to bridge software hardware, it's up to interested companies like ST, IBM and Lockheed-Martin to do much of the construction.

MTSW-107-09-L-D-006-RA

Layer 7 Load Balancing Mechanisms In the previous section, we covered the HTTP protocol in detail. You now understand the URLs, methods, and cookies. In Layer 7 load balancing, the SLB device proxies the client's TCP connection and receives the HTTP request. The SLB device buffers the client request and parses through it. The load balancer can perform many functions while inspecting the HTTP header. Following are some of the key mechanisms that can be used in Layer 7 load balancing:

HTTP Methods-Based Load Balancing The SLB device can definitely inspect the HTTP method used by the client and make appropriate load-balancing decisions. For instance, the SLB device can be configured to distribute GET and POST methods to separate server farms. The SLB device can easily drop DELETE method calls to prevent hackers from deleting web content.

HTTP URL-Based Load Balancing The SLB device can inspect the HTTP URL and make appropriate load-balancing decisions. The device can distribute requests based on access content or application to different server farms. For example, all .cgi requests can be sent to servers optimized for request processing and computation, while all static content requests (.htm, .gif, and so on) can be sent to servers with a lot of disk space. Similarly, server management can be eased up by keeping separate server farms for /sports/* and /news/*. Figure 4-8 shows how a Layer 7 load-balancing device can be used to inspect HTTP requests and distribute client requests based on content type.

MTSW-107-09-L-D-006-RA

Figure 4-9 shows how a Layer 7 load-balancing device can be used to inspect HTTP requests and distribute client requests based on the applications being accessed.

MTSW-107-09-L-D-006-RA

HTTP Cookie-Based Load Balancing The SLB device can make a load-balancing decision based on the clients’ cookies. This is vital for applications, such as Web Logic, which uses multiple cookies to provide client session redundancy.

The correlator system is based on the hardware developed for the Caltech- OVRO Broadband Reconfigurable Array (Cobra). The Cobra correlator was used for processing the 4-GHz bandwidth received from the six 10-meter antennas in the Caltech-OVRO array.

The correlator system comprises analog subsystems (noise source and downconverters) and digital subsystem (the digitizer and correlator boards). The analog components are controlled by Linux. The digital components are controlled by a Linux CompactPCI host in each CPCI crate, and the digitizer and correlator boards each contain a DSP for real-time processing.

Most modern correlator systems are a hybrid of analog filtering/downconversion and digital correlation. Commercial digitizers exist in the 1-Gsample/second to 4-Gsample/s range, with custom samplers available at higher frequencies. The higher the sampler frequency, the more bits/second the correlator system must process.

The commercial samplers used in the Carma correlator operate at 1 Gsample/s. This selection was based in part on the fact that when the data is parallelized to a lower clock frequency, the resulting digital data bus width is compatible with the chosen FPGA and cabling technology. The choice of sampling frequency then specifies the bandwidth that the downconverters must produce. With a 1-Gample/s frequency, the downconverter bandwidth must be 500 MHz or less, located at either baseband or at a compatible aliasing band.

Millimeter observing can be classified into two bandwidth regimes: wide-bandwidth continuum observing and spectral line observing. A continuum correlator needs to cover as much bandwidth as possible (ideally, the full receiver output bandwidth). The Carma downconverters accept a 1- to 5-GHz intermediate-frequency band and produce an output signal within the 500-MHz to 1-GHz band.

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