Specifications

Chapter 1 Understanding Networking and IP Addressing
Introduction to Networking
Niagara Release 2.3
Niagara Networking & Connectivity Guide Revised: May 22, 2002
1–7
Network Cabling The transmission medium used to support network communications is an extensive
subject. There are issues that define the best type of cable suited for different
signaling rates, different physical and electrical environments, and various
architectural requirements and limitations. The key is to strike an acceptable balance
between performance, cost, and capacity.
Coaxial Cable
Coaxial cable contains a single, solid or stranded wire, inner conductor surrounded
by an outer conductor surrounded by an outer conductor and shield of braided wire
mesh or foil. The conductor and the shield are separated from each other by a layer
of insulation, and the entire cable is wrapped in another layer of insulating material.
Because the conductor and the shield share the same axis, the medium is called
coaxial, or coax for short. Coaxial cable generally provides better protection from
electromagnetic interference (EMI) than twisted pair cabling, but it is more
expensive and tougher to work with.
Some network standards are compatible with more than one type of cable. Ethernet,
for instance, can use either thick or thin coaxial cable. The thicker cable, called thick
Ethernet or 10Base5—the 5 refers to a maximum segment distance of 500
meters—can reliably carry signals over greater distances than thin Ethernet, also
called 10Base2, which can only stretch up to 185 meters. With 10Base2, a 50-ohm
terminator is mounted at the host, whereas with 10Base5 the terminator is mounted
on the cable. ThickNet cable tends to be more expensive than ThinNet cable and it
uses RG-11 connectors, whereas ThinNet cable uses BNC connectors.
Twisted Pair Cable
Twisted pair cable has two insulated copper wires that are twisted around each other
to reduce EMI (referred to as crosstalk). Twisted pair cable has been used for years
in the telephone industry, so the technology and standards for this type of cable are
well established. However, many standard telephone cables are not twisted pair and
are inadequate for most network applications.
Although twisted pair cable is often unshielded, some products use shields to reduce
the cable's susceptibility to EMI. When a distinction must be made, twisted pair cable
may be referred to as either UTP (unshielded twisted pair) or STP (shielded twisted
pair). STP is capable of handing more data at greater speed and is more resistant to
outside interference.
The majority of new wiring installations use Category 5 UTP wire in order to be able
to run faster network technologies. Categories 1 through 5 are based on the
EAI/TIA-568 standard.
Table 1-1 Cable categories.
Category Cable Type Application
1UTPAnalog voice
2 UTP Digital voice (1 Mbps data)
3 UTP, STP 16 Mbps data
4 UTP, STP 20 Mbps data
5 UTP, STP 100 Mbps data