Corporate switches are more expensive than switches for home and SOHO.Using a company's network requires functions not available at home or SOHO.Let's focus on the typical additional functions of such a company switch. |
Function that houses multiple Ethernet
Now, the keywords are listed like Ethernet, Ethernet, and UTP cables.Of the UTP standards, 10GBASE-T supports only the total double communication, but the standard up to Gigabit supports both "Semi-double communication (CSMA/CD)" and "total double communication".Therefore, considering the communication mode,
Seven exists.
Depending on the company, the old and slow devices introduced more than 10 years ago and the new and fast devices may be mixed in the LAN.In particular, switches for companies need to respond to the latest standards as soon as possible, but do not cut off the old standards, but to support more communication modes.However, if there are seven communication modes, it is extremely likely that some of them will be mixed in LANs with hundreds of terminals.
Even if the switch is compatible with multiple communication modes, if the administrator must set the communication mode for each port, the burden on the administrator will increase each time the Ethernet standard increases.In this case, if all communication mode devices can be connected to one switch and communicating with each other, the cost of the device and the load on the administrator will be reduced.
For this reason, "Auto-Negotiation) has appeared.Auto -negotiation is a mechanism that exchanges information between devices corresponding to multiple communication modes and automatically sets the optimal communication mode (Fig. 1).
Figure 1 Autonagocation that automatically recognizes standards and communication mode
Switches with an auto -negotiation function know the communication mode supported by the connection partner and select the fastest communication mode supported by both sides.
また、同じ速度で複数の選択肢があった場合には、より低い品質のケーブルで動作する通信モードが選択される。さらに、後述する「PAUSEフレーム」によるフロー制御の可否や、100BASE-T2や1000BASE-Tのマスター／スレーブの情報※1なども交換し、それぞれの機能の動作を最適化する。
※1：マスターとスレーブ 1Gbpsの1000BASE-Tでは、通信に送信側と受信側のどちらか一方の周波数を使用する。自身の周波数を提供する側を「マスター」、相手に合わせる側を「スレーブ」と呼ぶ。The printer purchased a few years ago is compatible with 10BASE-T, 3 years ago PC is compatible with 100BASE-TX, and the server introduced this year is surprisingly common.In this case, if all ports install a switch corresponding to the auto-negotiation of 10BASE-T/100BASE-TX/1000Base-T, the switch will automatically adjust the appropriate communication mode.
(Next page, following "Flow control that absorbs speed difference")
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