Physical Coding Sublayer

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The Physical Coding Sublayer (PCS) further helps to define physical layer specifications for 10 gigabit ethernet after having been broken down into their Physical Media Dependent Sublayer or PMD. Each sublayer places the 10GBASE standards into either LAN or WAN specifications.

Physical Coding Sublayer (PCS) Specifications:

10GBASE-R (LAN) is the serial encoded PCS that allows for Ethernet framing at a rate of approximately 10.3 Gbit/s (MAC= 10,000 Gbit/s, overhead= 64 B/66 B effective rate= 10,000 * 66/64= 10,312.5 - see also 64B/66B encoding). 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) uses similar coding methods as 10GBASE-R but is only used in the definition of 10GBASE-LX4. This is mainly due to the fact that LX4 operates on both single and multimode fibers, giving it a unique set of specifications as defined in its PMD.

10GBASE-W (WAN) defines WAN encoding for 10GbE, it encodes the frames so that they are compatible with SONET STS-192c data rates and SDH VC-4-64 transmission standards allowing for 10 Gbit/s transmission across a WAN. It does this by wrapping the 64 B/66 B payload into a SONET frame, making the effective rate 9.95 Gbit/s.

Works Cited: Barbieri, Alessandro. “10 GbE and Its X Factors.” Packet: Cisco Systems Users Magazine Third Quarter 2005 Vol. 17, No. 3: 25 – 28.