4
UTP CAT3 and CAT4 were used for a quite limited time since the emergence of 100Base-TX networks meant a quick shift to CAT5. By the year 2000, moves to gigabit (1000Base-TX) Ethernet LANs created a need for another specification, CAT5e. CAT5e is now being superseded by CAT6 cable and there is a developing standard for CAT7.
Specifications for Cat3, Cat4, Cat5, Cat5e, Cat6, and Cat7 Cables
It might seem that CAT5 and CAT5e are the same. Pretty much they are, the CAT5e specification simply included some additional limits over the CAT5 specification. The reality is that most CAT5 cable is in fact CAT5e cable just not certified as such. Here is a comparison of those extra specifications.
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6
其實(shí)是標(biāo)準(zhǔn)要求不同,超五類包含了雙工應(yīng)用的要求。五類電纜只會(huì)采用二對(duì)銅芯作傳輸,一對(duì)作為發(fā)出訊息;另一對(duì)用作接收訊息。而快速以太網(wǎng)則需要利用四對(duì)銅芯作數(shù)據(jù)傳輸,所以需要采用提供四對(duì)銅芯傳輸?shù)某孱愲娎|。超五類電纜提供一系列的測(cè)試標(biāo)準(zhǔn),如提供四對(duì)銅芯傳輸,而其中會(huì)特別針對(duì)遠(yuǎn)端串?dāng)_的性能表現(xiàn),以確保網(wǎng)絡(luò)可支持千兆網(wǎng)運(yùn)行,而超五類電纜強(qiáng)調(diào)累加功率性能表現(xiàn),以提高電纜性能的穩(wěn)定性。
具體表現(xiàn)為兩者在衰減的要求是一樣的,對(duì)于近端串音以及回波損耗的要求超五類高于五類。
PS-NEXT(相鄰線對(duì)綜合近端串?dāng)_) ELFEXT(等電平遠(yuǎn)端串音) PS-ELFEXT(等效遠(yuǎn)端串?dāng)_衰減) Delay Skew(延時(shí))等體現(xiàn)雙工要求的數(shù)據(jù)則只適用于超五類線。
實(shí)際上提出超五類的要求就是因?yàn)樵瓉淼奈孱愐笠呀?jīng)無法滿足現(xiàn)在網(wǎng)絡(luò)增長的需要或者說五類電纜支持更高速的傳輸協(xié)議。只有超五類的電纜才能保證視頻通話、在線電影的高速增長的網(wǎng)絡(luò)要求!
[zhaogy2006 在 2009-1-16 15:30:47 編輯過]
