HP ProCurve Tech Brief: 10-Gigabit Ethernet Cabling

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IEEE 802.3ak/10GBASE-CX4
Approved in February 2004, 10GBASE-CX4 is a low-cost
10-GbE solution intended for copper cabling with
short-distance connectivity that makes it ideal for
wiring closet and data center connectivity. The first 10-
GbE copper cabling standard, 10GBASE-CX4 provides
immediate advantages with its affordability and wide
availability.
The CX4 standard transmits 10-GbE over four channels
using twin-axial cables. The cables were derived from
InfiniBand connectors and cable, but the CX4
standards committee defined the cables to be tighter in
electrical specifications. Therefore, longer-length
(>10 m) InfiniBand cables will not necessarily work for
CX4 applications and it is recommended that networks
use only cables that are designed to meet IEEE 802.3ak
specifications when using CX4.
Another aspect of the CX4 cable is the rigidity and
thickness of the cable. The longer the cable length
used, the thicker the cable will be. CX4 cables start at
30 American Wire Gauge (AWG) for short lengths to 24
AWG thickness for a full 15 m. CX4 cables must also be
factory terminated to meet defined specifications, so
they should be ordered to length.
IEEE 802.3an/10GBASE-T
Proposed in November 2002, 10GBASE-T is the latest
10-GbE standard for use with unshielded twisted pair
(UTP) style cabling. The goal of this copper standard,
ratified in June 2006, is to approximate RJ-45
connectivity of 100 m. It is intended to improve the
performance and distance of copper cabling at a cost
that is lower or similar to fiber.
Category 5 (Cat 5) and Category 6 (Cat 6) are the most
common cabling systems being installed today, but Cat
5 is not capable of meeting the bandwidth and
crosstalk demands of 10-GbE’s higher transmission
speeds. In a large percentage of installations, cabling
will need to be modified to support it. To meet the
needs of 10-GbE, a Telecommunications Industry
Association (TIA) subcommittee for cabling
specifications is working to provide additional
specifications that will help vendors create sufficient
cabling.
The defined cabling standard is Category 6A (Cat 6A),
which is designed with existing Cat 6 cable but
measured and specified to higher frequencies. In
addition to Cat 6A, 10GBASE-T will operate on Category
7 (Cat 7) cables.
Optical media converters
Optical media converters have traditionally been used
in converting Ethernet LAN copper transmission to
fiber-optic cabling for the express purpose of
extending the copper distance past 100 m. More of an
implementation tactic than cabling standard, optical
media converters provide a way to utilize existing
copper and support low-cost fiber transmission. In
many cases, fiber can extend 100 Mb transmission over
100 km and 1000 Mb transmission up to 70 km.
IEEE 802.3 cabling cost and distance considerations
Highest cost
Lowest cost
Distance
ER 40 km
LR 10 km
SR 300 m
CX4 + OMC 300 m
CX4 15 m