Physical Coding Sublayer

Description

• Data Link Layer
• * LLC
• * MAC
• ** RS - This sublayer processes PHY Local/Remote Fault messages and handles DDR conversion
• PHY Layer
• * PCS - This sublayer determines when a functional link has been established, provides rate difference compensation, and performs coding such as 64b/66b encoding and scrambling/descrambling
• * PMA - This sublayer performs PMA framing, octet synchronization/detection, and scrambling/descrambling
• * PMD - This sublayer consists of a transceiver for the physical medium

  Specifications

10 Mbit/s Ethernet

• Classic Ethernet uses Manchester code in the Physical signaling sublayer, encoding each bit as a high-low or low-high transition.

  Fast Ethernet

• 100BASE-X for fiber and twisted pair copper encodes data nibbles to five-bit code groups.

  Gigabit Ethernet

• 1000BASE-X for fiber and 150 Ω balanced copper uses 8b/10b encoding with a symbol rate of 1.25 GBd.
• 1000BASE-T for twisted pair copper splits the data into four lanes and uses four-dimensional, five-level Trellis modulation with PAM-5 and a symbol rate of 125 MBd.

  2.5 and 5 Gigabit Ethernet

• 2.5GBASE-T and 5GBASE-T use the same encoding as 10GBASE-T slowed by a factor of four or two, respectively.

  10 Gigabit Ethernet

• 10GBASE-R is the serial encoded PCS using 64b/66b encoding that allows for Ethernet framing at a rate of 10.3125 Gbit/s. This rate does not match the rate 9.953 Gbit/s used in SONET and SDH and is not supported over a WAN based on SONET or SDH.
• 10GBASE-X uses 8b/10b encoding over four lanes at 3.125 GBd each and is used for 10GBASE-LX4, 10GBASE-CX4, and 10GBASE-KX4.
• 10GBASE-W defines WAN encoding for 10GbE. It uses 64/66b encoding and lowers the MAC rate to 9.95 Gbit/s, so that is compatible with SONET STS-192c data rates and SDH VC-4-64 transmission standards when wrapped into a SONET frame.
• 10GBASE-T for twisted pair copper splits the data into four lanes and uses 64B/65B encoding, scrambling, and 128 double-square checkerboard encoding with PAM-16 generated at 800 MBd.

  25 Gigabit Ethernet

• 25GBASE-R uses the same 64b/66b encoding as 10GBASE-R with a speed-up to 25.78125 GBd.

  40/100 Gigabit Ethernet

• 40GBASE-R and 100GBASE-R use 64b/66b encoding over multiple lanes of 10.3125 GBd or 25.78125 GBd each. These lanes – four for 40 Gbit/s, four or ten for 100 Gbit/s per direction – are either transmitted separately over short distance or together with coarse wavelength division multiplexing on long distance fiber.