Contents

Physical coding sublayer

The Ethernet PCS sublayer is at the top of the Ethernet physical layer (PHY). The hierarchy is as follows:

• Data link layer (Layer 2)
  • Logical link control (LLC) sublayer
  • Medium access control (MAC) sublayer
    • Reconciliation sublayer (RS) – This sublayer processes PHY local/remote fault messages and handles DDR conversion
• PHY Layer (Layer 1)
  • Physical coding sublayer (PCS) – This sublayer determines when a functional link has been established, provides rate difference compensation, and performs coding such as 64b/66b encoding and ${\displaystyle x^{58}+x^{39}+1}$ scrambling/descrambling
  • Physical medium attachment (PMA) sublayer – This sublayer performs PMA framing, octet synchronization/detection, and ${\displaystyle x^{7}+x^{6}+1}$ scrambling/descrambling
  • Physical medium dependent (PMD) sublayer – This sublayer consists of a transceiver for the physical medium

Specifications[edit]

10 Mbit/s Ethernet[edit]

• Classic Ethernet uses Manchester code in the Physical signaling sublayer (PLS), encoding each bit as a high-low (logical zero) or low-high transition (logical one).^[2]

Fast Ethernet[edit]

• 100BASE-X for fiber (100BASE-FX) and twisted pair copper (100BASE-TX) encodes data nibbles to five-bit code groups (4B5B).^[3]

Gigabit Ethernet[edit]

• 1000BASE-X for fiber and 150 Ω balanced copper (twinaxial) uses 8b/10b encoding with a symbol rate of 1.25 GBd.^[4]
• 1000BASE-T for twisted pair copper splits the data into four lanes and uses four-dimensional, five-level (quinary) trellis modulation with PAM-5 and a symbol rate of 125 MBd.^[5]

2.5 and 5 Gigabit Ethernet[edit]

• 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[edit]

• 10GBASE-R (LAN) 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 (LAN/WAN) uses 8b/10b encoding over four lanes at 3.125 GBd each and is used for 10GBASE-LX4 (single-mode and multi-mode fiber), 10GBASE-CX4 (twinax), and 10GBASE-KX4 (backplane).^[6]
• 10GBASE-W (WAN) 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 (DSQ128) checkerboard encoding with PAM-16 generated at 800 MBd.^[7]

25 Gigabit Ethernet[edit]

• 25GBASE-R uses the same 64b/66b encoding as 10GBASE-R with a speed-up to 25.78125 GBd.^[8]

40/100 Gigabit Ethernet[edit]

• 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 (-LR).^[9]

See also[edit]

• PHY-Level Collision Avoidance

References[edit]

• Barbieri, Alessandro. "10 GbE and Its X Factors" (PDF). Packet: Cisco Systems Users Magazine. 17 (3): 25–28. Archived from the original (PDF) on 2011-06-08. Retrieved 2007-12-31.

External links[edit]

• IEEE 802.3 Meeting
• Ethernet 1000BASE-X PCS/PMA Technology Basics

• Category

Commons