Protocol Analyzers

In the course of designing new or upgrading an old network often occurs the need for quantitative measurement of some characteristics of the network such for example, as the intensity of the flow of data over network lines, delays, arise at different stages of packet processing, reaction time to requests this or that kind, the frequency of occurrence of certain events and other characteristics.

For these purposes may be used various means, and above all - monitoring tools in the control systems network. Some measurements on the network can be performed in a built-in operating system software products, but more sophisticated means of investigation is the the network protocols analyzer. The analysis process includes the capture of circulating packets in the network of a particular network protocol, and studying the contents of these packages. Based on the results of the analysis, it is possible to optimize the network performance and troubleshooting. It is obvious that in order to be able to draw any conclusions on the effect of a change in the network, you must perform protocol analysis, both before and after making changes. Protocol analyzers can be divided into two main classes - the hardware and software. The hardware protocol analyzers are separate dedicated device, equipped with special network card and appropriate software. Used network interface card and software must comply with network technology. Apparatus analyzer connected to the network just like a regular computer. The distinction is that the analyzer can take all the data packets transmitted by network, while the usual station - just addressed to it.

Program analyzers are specialized software that is installed on a conventional computer. For its work program analyzers use hardware resources.

The software (SW) of the analyzer (and apparatus and programm) consists of a kernel that supports the work of the network adapter. In addition, delivered a number of decoding procedures aimed at certain protocol, for example, IPX. In the structure of software of apparatus analyzers and some program may also contain an expert system that can deliver user recommendations about what experiments should be carried out in these situations that may mean certain measurements, how to eliminate certain types of the network failures.

Today, the telecommunication market has a wide selection of both software and hardware protocol analyzers, but they all have several key components:

- User interface - the interface allows the user to: show results of traffic analysis, to obtain instantaneous and averaged statistical evaluation of network performance, monitor the occurrence of critical situation (network congestion) to produce decoding of packets at various levels and to represent the contents of packages. in an understandable form.

- Capture Buffer - buffers of different analyzers characterized by volume. Buffer can be located on an installed network card (apparatus analyzers), or for him may be given a place in memory of one of the computers in the network (software analyzers). If the buffer is located on network card, then its management is carried out in hardware, and due to this input rate increases. However, this leads to the increase the cost of analyzer. In the case of a small volume of buffer part of the information will be lost, and analysis would be impossible. The buffer size determines thepossibility of analyzing by more or less representative samples of captured data.

- Filters - can manage the process of data capture, and thus saves buffer space. Depending on the value of certain packet's fields given in the form of filtering conditions, the packet is either ignored, or written to the capture buffer. Using filters significantly speeds up and simplifies the analysis, as it excludes the view of unwanted packets.

- Switches - are some conditions specified by the operator of thebeginning and termination of the capture of data from the network. Such conditions can be performance of manual commands to start and stop the capture process, time of day, the duration of the capture process, the occurrence of certain values ​​in frames of data. The switches can be used in conjunction with filters, allowing more detailed analysis, as well as productive use of
limited amount of the capture buffer.

- Search - Some protocol analyzers allow you to automate viewing information in the buffer, and find in it data corresponding to criteria.

Дата добавления: 2014-12-27