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Published on: July 01, 2009
Type of content: WHITE PAPER
Format: Unknown
Length: 8 pages
Price: FREE

Overview:
The Ethernet physical layer is typically implemented in a chip called PHY. In the old days each PHY can handle only one port. Today there are PHY chips that each chip can handle multiple ports and supports both the copper and optical media. For example, see PHY chips from Broadcom or Marvell. Also, the PHY may be integrated as part of a larger chip that has other functionalities such as the MAC layer, or even as part of the CPU chip.

Most users of Ethernet and Gigabit Ethernet pay little attention to how the physical layer works. From a user's perspective, typically the parameters that involve configuring the PHY are enabling or disabling auto-negotiation, setting up the auto-negotiation advertisement parameters such as the speed, duplex and flow control, or forcing them to certain values if auto-negotiation is disabled. There are obviously a lot more parameters in the PHY that can be configured, such as enabling or disabling automatic MDI crossover (AUTO-MDIX), the LED modes etc, but most of them are handled by the device driver and are invisible to the user.

Read this paper to learn about common Ethernet technologies for the copper medium and different tapping methods.