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ディレイ・スキュー
データ・ケーブルの4対のワイヤーは撚りが異なるため、全体の長さが異なる。このため、4対の信号がレシーバーに到着する時刻が異なる。この時間差を遅延スキューと呼びます。詳しくはこちらをご覧ください。
伝搬遅延とは、信号がリンクの一方の端からもう一方の端まで移動するのにかかる時間のことである。遅延スキューとは、遅延の差のことで、データ・ケーブルの4対を伝わる信号がレシーバーに到達する時間差のこと。
Gigabit Ethernet and the faster Ethernet versions divide the total data stream into four streams that travel along one wire pair each and transmit one fourth of the total data rate. The four data signals travel along the data cable simultaneously and the receiver combines them again to one. To make this work, the four signals have to arrive at the receiver almost at the same time. As the wire twist differs from one pair to another, the lengths of the pairs differ too and because of this the signals cannot arrive at exactly the same time at the receiver. The difference in time is called delay skew.
Trouble-shooting tips if delay skew tests fail
Typical cause of the problem | This might help |
Horizontal cable too long | Cut the cable (if possible) |
Patch cord too long | Use shorter patch cords |
Consolidation point cable too long | Use shorter consolidation point cable |
Pair twists differ too much | Cut the cable, replace cable |
Cable defective (material defect) | Replace cable |
Typical causes of delay skew problems and what might help to solve them.
Contact
Dirk Träger
