10 Gigabit Ethernet
Unlike previous Ethernet standards, 10GbE defines only full-duplex point-to-point links which are generally connected by network switches; shared-medium CSMA/CD operation has not been carried over from the previous generations of Ethernet standards[1] so half-duplex operation and repeater hubs do not exist in 10GbE.
Over the years the Institute of Electrical and Electronics Engineers (IEEE) 802.3 working group has published several standards relating to 10GbE.
PHY modules are not specified in an official standards body but by multi-source agreements (MSAs) that can be negotiated more quickly.
[15][16] When choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size (form factor).
The newest module standard is the enhanced small form-factor pluggable transceiver, generally called SFP+.
Based on the small form-factor pluggable transceiver (SFP) and developed by the ANSI T11 fibre channel group, it is smaller still and lower power than XFP.
[17][15] SFP+ modules do only optical to electrical conversion, no clock and data recovery, putting a higher burden on the host's channel equalization.
XFI and SFI use a single lane data channel and the 64b/66b encoding specified in IEEE 802.3 Clause 49.
[16] There are two basic types of optical fiber used for 10 Gigabit Ethernet: single-mode (SMF) and multi-mode (MMF).
The advantage of MMF is that it can be driven by a low cost Vertical-cavity surface-emitting laser (VCSEL) for short distances, and multi-mode connectors are cheaper and easier to terminate reliably in the field.
They are lower cost than other optical solutions because the manufacturer can match the electronics to the required length and type of cable.
[citation needed] 10GBASE-SR ("short range") is a port type for multi-mode fiber and uses 850 nm lasers.
[24][30] MMF has the advantage over SMF of having lower cost connectors; its wider core requires less mechanical precision.
DFB lasers are more expensive than VCSELs but their high power and longer wavelength allow efficient coupling into the small core of single-mode fiber over greater distances.
Some 10GBASE-LRM transceivers also allow distances up to 300 metres (980 ft) on standard single-mode fiber (SMF, G.652), however this is not part of the IEEE or MSA specification.
[34] To ensure that specifications are met over FDDI-grade, OM1 and OM2 fibers, the transmitter should be coupled through a mode conditioning patch cord.
It uses four separate laser sources operating at 3.125 Gbit/s and Coarse wavelength-division multiplexing with four unique wavelengths around 1310 nm.
Downstream delivers serialized data at a line rate of 10.3125 Gbit/s in a point to multi-point configuration.
It uses the XAUI 4-lane PCS (Clause 48) and copper cabling similar to that used by InfiniBand technology with the same SFF-8470 connectors.
[43] Like 10GBASE-CX4, DA is low-power, low-cost and low-latency with the added advantages of using less bulky cables and of having the small SFP+ form factor.
SFP+ direct attach today is tremendously popular, with more ports installed than 10GBASE-SR.[40] Backplane Ethernet, also known by the name of the task force that developed it, 802.3ap, is used in backplane applications such as blade servers and modular network equipment with upgradable line cards.
802.3ap implementations are required to operate over up to 1 metre (39 in) of copper printed circuit board with two connectors.
It also defines an optional layer for forward error correction, a backplane autonegotiation protocol and link training for 10GBASE-KR where the receiver tunes a three-tap transmit equalizer.
This operates over a single backplane lane and uses the same physical layer coding (defined in IEEE 802.3 Clause 49) as 10GBASE-LR/ER/SR.
[40] 10GBASE-T, or IEEE 802.3an-2006, is a standard released in 2006 to provide 10 Gbit/s connections over unshielded or shielded twisted pair cables, over distances up to 100 metres (330 ft).
The line encoding used by 10GBASE-T is the basis for the newer and slower 2.5GBASE-T and 5GBASE-T standard, implementing a 2.5 or 5.0 Gbit/s connection over existing category 5e or 6 cabling.
10GBASE-T1 is for automotive applications and operates over a single balanced pair of conductors up to 15 m long, and is standardized in 802.3ch-2020.
The WAN PHY can drive maximum link distances up to 80 km depending on the fiber standard employed.
It also uses a WAN interface sublayer (WIS) defined in clause 50 which adds extra encapsulation to format the frame data to be compatible with SONET STS-192c.
