CA
1. COMPUTER ASSOCIATES: Computer Associates International, the world's leading software suppliers.
2. CERTIFICATE AUTHORITY: a neutral certification body, the use of digital certificates (DIGITAL CERTIFICATE) generate a digital signature (DIGITAL SIGNATURE) with the public and private key (PUBLIC-KEY/PRIVATE-KEY) to verify and prove the user's identity.
Cable Modem Network
Access to cable TV (CABLE TV) coaxial cable (COXIAL CABLE) lines transmit data modem (MODEM). Because cable television wiring area is very broad, and the use of coaxial cable network than the telephone line to provide a higher bandwidth ( BANDWIDTH), making use of CABLE MODEM to connect to the Internet (INTENET) looks like a good choice, but there are still some technical problems to overcome. For example, the traditional cable TV company from the 4th to the viewing room of the home in households one-way transmission of information can not be heard from the user side, in addition to the broadband modem via Ethernet links, can provide full-time online service, but because Ethernet is a shared media, the transmission speed must be regarded as location using a cable modem broadband Internet access number, as well as network sharing and other security concerns caused by
CACHE
CACHE is a kind of memory or disk access speed up the device, you can copy the information on the slow drive to the fast disk read and write actions to improve system response speed.
Its principle of operation is to use a faster storage device to keep a slow storage device from which to read the information and copy, when it is necessary to save the body from the slower read and write data, CACHE can be made to read and write actions first to complete the installation quickly, so make the system respond more quickly.
For example, access memory (RAM) drive faster than the speed of very large, so we can be a part of main memory to retain as a disk CACHE, whenever a disk read demands put just read a copy of the information on the CACHE memory, if the system continue to ask to read or write the same data or the same sector (sector), the system directly from the memory in the CACHE section for reading and writing action, such a system on the disk access speed feels much faster.
Similarly, the static random access memory (SRAM) than the dynamic random access memory (DRAM) read and write speed, the use of these static random access memory as a dynamic memory CACHE, also can improve the efficiency of read and write.
SRAM memory to replace DRAM does not use all the reason is because the cost of SRAM is much higher than DRAM.
CACHE problem is the use of the information contained in written CACHE immediately write back if you do not really storage, a power failure or other accidents, but will lead to data loss; if so every time the data write back to the real storage, but also CACHE can be made to play a function of speed reading, not speed up the write speed, in such a situation makes the CACHE way to write is divided into two categories:
1. Write-Through: every time a write will write data to the real storage.
2. Write-Back: experience writing does not necessarily write-back, only records within the CACHE and will be marked as a copy of the information has been changed (dirty), and other systems are available or wait until some time after the data write-back the real storage, this is take a little risk in exchange for efficiency.
As the system does not often read and write only to repeat the same one region, the use of two separate CACHE performance is usually better than using only a set, which is called 2-Ways Associate, Similarly, the use of four groups of CACHE is called 4ways Associate , but more groups CACHE will make the algorithm relatively complex.
CACHE performance according to the use of algorithms are good or bad, the unit commonly used measure hit rate (hits), the higher hit rate better.
The new CPU also has built-in CACHE, called LEVEL 1 (L1) cache, since the same time with the CPU clock operation, than on the motherboard of the LEVEL 2 (L2) CACHE provide faster access performance.
Caching
Caching is a technology can reduce the network bandwidth can be the number of frequent access to the information copied and stored in the cache server, thus reducing network and backbone network transmission on the amount of data.
As the increase in the number of Internet content much faster than network bandwidth, Caching growing in importance, but also telecom operators and Internet content provider (ICP) in response to lack of bandwidth and transmission speed is too slow, and we want to meet user needs solution.
As the website must be between the server and the browser to complete two trips a "shuttle run" (Round Trip Process), when the real-time video or multimedia content delivery, delay time of network access will be more to the more serious.
Caching principle of operation mainly in server-side and client network between the structure, add a number of intermediate endpoints, the user is frequently used, or frequent access to the information placed on the intermediate endpoint, when the user needs view or access, the endpoint can be obtained directly from the intermediary, without having to connect to remote server-side, thus able to reduce network transmission time and bandwidth, relative to enhance user satisfaction.
The industry's widespread use of cache technology is many forms, including Replication Relationships and Proxy Relationships two categories. Planting is also a lot of industry-based caching techniques, the development of content delivery network (CDN; Content Delivery Network) solution. |
