10 gigabit Ethernet
From Wikipedia, the free encyclopedia
10 gigabit Ethernet or 10GbE is the most recent (as of 2006) and fastest of the Ethernet standards. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s, ten times as fast as gigabit Ethernet. 10GbE over fiber and InfiniBand "like" copper cabling are specified by the IEEE 802.3-2005 standard. 10GbE over twisted pair has been released under the IEEE 802.3an amendment.
10 gigabit Ethernet abandons half duplex links and repeaters (and the CSMA/CD that goes with them) in favor of a system of purely full duplex links connected by switches as was already the normal practice with gigabit ethernet.
As of 2007 10 gigabit Ethernet is very new, and it remains to be seen which of the standards will gain commercial acceptance. The 10 gigabit Ethernet standard encompasses a number of different physical layer (PHY) standards.
Contents |
[edit] Fibre
[edit] LAN PHY
The most common optical variety is referred to as LAN PHY, used for connecting directly between routers and switches. Although called LAN, this can be used with 10GBase-LR and -ER up to 80 km. LAN PHY uses a line rate of 10.3 Gbit/s and a 64B/66B encoding.
[edit] 10GBASE-SR
10GBASE-SR ("short range") is designed to support short distances over deployed multi-mode fiber cabling, it has a range of between 26 m and 82 m depending on cable type. It also supports 300 m operation over new, 50um 2000 MHz·km multi-mode fiber (using 850 nm).
[edit] 10GBASE-LRM
10GBASE-LRM, also known as 802.3aq, is a newly ratified standard[1] which supports distances up to 220 m on FDDI-grade 62.5 µm multi-mode cable originally installed in the early 1990s for FDDI and 100BaseFX networks.
[edit] 10GBASE-LR
10GBASE-LR is a Long Range Optical technology delivering serialized 10 gigabit Ethernet via over 1300 nm single-mode fiber via IEEE 802.3 Clause 49 64B-66B Physical Coding Sublayer (PCS).
Optical transceivers are interconnected with a host device, by either an IEEE 802.3 Clause 48 8B-10B 4 channel parallelized bridge or another Clause 49 bridge. (XENPAKs, X2s, and XPAKs use the Clause 48 conversion and XFPs use a straight Clause 49). LR optical cabling is used to interconnect transceivers at a distance spaced at 10km, but it can often reach distances of up to 25km with no data loss.
[edit] 10GBASE-ER
10GBASE-ER ("extended range") supports distances up to 40 km over single-mode fiber (using 1550 nm).
[edit] 10GBASE-ZR
Recently, several manufacturers have introduced 80-km-range ER pluggable interfaces under the name 10GBASE-ZR. This 80km PHY is not specified within the IEEE 802.3ae standard and manufacturers have created their own specifications based upon the 80km PHY described in the OC-192/STM-64 SDH/SONET specifications.
It is not yet known whether or not a specific specification will be added to cover the ZR PHY.
[edit] 10GBASE-LX4
10GBASE-LX4 uses coarse wavelength division multiplexing to support ranges of between 240 m and 300 m over deployed multi-mode cabling. This is achieved through the use of four separate laser sources operating at 3.125 Gbit/s in the range of 1300nm on unique wavelengths. This standard also supports 10 km over single-mode fiber.
[edit] WAN PHY
10GBASE-SW, 10GBASE-LW and 10GBASE-EW are varieties that use the WAN PHY, designed to interoperate with OC-192/STM-64 SDH/SONET equipment using a light-weight SDH/SONET frame running at 9.953 Gbit/s. WAN PHY is used when an enterprise user wishes to transport 10G Ethernet across telco SDH/SONET or previously installed wave division multiplexing systems without having to directly map the Ethernet frames into SDH/SONET. The WAN PHY variants correspond at the physical layer to 10GBASE-SR, 10GBASE-LR and 10GBASE-ER respectively, and hence use the same types of fiber and support the same distances. There is no WAN PHY standard corresponding to 10GBASE-LX4 and 10GBASE-CX4 since the original SONET/SDH standard requires a serial implementation.
[edit] Copper
[edit] 10GBASE-CX4
10GBASE-CX4 — also known by its working group name 802.3ak — transmits over 4-lanes in each direction over copper cabling similar to the variety used in InfiniBand technology. It is designed to work up to a distance of 15 m (49 feet). This technology has the lowest cost per port of all 10Gb interconnects, at the expense of range. Each device capable of supporting a 10GbE module uses some MSA (Multi-Source Agreement) to provide the actual module connectivity within the device to the outside connector. XENPAK, X2, and XPAK connectors all fit into a standard MSA pinout. CX4 modules exist at least in the XENPAK and X2 variety, and possible XPAK, although the smaller size makes this configuration more difficult. Each lane of the copper carries 3.125 gigahertz of signaling bandwidth. It is the job of the 802.3ae Clause 48 protocol to manage and synchronize the data flowing between these 4 channels; this functionality is maintained in the PCS. Compare to 10GBASE-R devices, which use the Clause 49 protocol. Clause 48 uses an 8 to 10 bit conversion to accommodate better line signaling, but Clause 49 uses a 64 to 66 bit conversion for this accommodation, which leaves the actual overhead for signaling much tighter than the Clause 48.
[edit] 10GBASE-Kx
Backplane Ethernet — also known by its working group name 802.3ap — is used in backplane applications such as blade servers and routers/switches with upgradable line cards. Kx implementations are required to operate in an environment comprising up to 40 inches of copper printed circuit board with two connectors. The standard provides for two different implementations: 10-GBASE-KR and 10GBASE-KX4. 10GBASE-KR uses the same coding as the 10GBASE-LR/ER/SR. It also defines an optional layer of Forward Error Correction and an autonegotiation protocol for setting the level of preemphasis based equalization. 10Gbase-KX4 is virtually identical with 10GBase-CX4. Implementations of both variants of 802.3ap are supposed to be backwards compatible with 1000Base-X serial implementations through autonegotiation.
[edit] 10GBASE-T
 |
Please help improve this article by expanding this section. Further information might be found on the talk page or at requests for expansion. Please remove this message once the section has been expanded. This article has been tagged since January 2007. |
10GBASE-T, or IEEE 802.3an-2006, is a newly released standard to provide 10 gigabit/second connections over conventional unshielded or shielded twisted pair cables.[2]
[edit] Connectors
10GBASE-T calls for the use of RJ-45 connectors already widely used with Ethernet. This is seen as a major advantage toward acceptance of this standard. (IEEE 802.3an in conjunction with ISO/IEC 11801-2002)
[edit] Cables
The 10GBASE-T standard uses Category 6, or Category 7 cable. An augmented Category 6 or "6a" cable specification, designed to reduce crosstalk between UTP cables (formally known as "alien crosstalk"), is currently under development. This would allow 10GBASE-T deployment at the full 100 meters distance specified for LAN wiring. (Source: IEEE 802.3an Objectives)
10GBASE-T will work over shorter distances with existing Category 6 cabling (up to about 56 meters), with the possibility of longer distances (up to 100 meters) for new 6a cable installations designed for 10GBase-T.
[edit] Electrical characteristics
The 802.3an standard defines the wire-level modulation for 10GBASE-T as a Tomlinson-Harashima Precoded (THP) version of pulse-amplitude modulation with 16 discrete levels (PAM-16), encoded in a two-dimensional checkerboard pattern known as DSQ128. Several proposals were considered for wire-level modulation, including PAM with 12 discrete levels (PAM-12), 10 levels (PAM-10), or 8 levels (PAM-8), both with and without Tomlinson-Harashima Precoding (THP). PAM-5 is what is used in the older 1000BASE-T gigabit Ethernet standard.
