Brochure/Catalogue

FO (Fibre-optic cables)
Fibre-optic cables provide an alternative transmission
medium to copper. A distinction is made between pure
glass bres (GOF: multimode/singlemode), combined bres
(PCF/HCS) and plastic bres (POF). They are primarily used
because of their insensitivity to electromagnetic interference,
but also, in the case GOF, on account of the signicantly
longer cable lengths compared to copper.
The bres are usually dened according to the core/
sheathing diameter in microns (µm):
GOF/MM: 50/125 or 62.5/125
GOF/SM: 9/125
PCF: 200/230
POF: 980/1000
Conventional bre-optic connector standards include SC
Duplex, SC-RJ, LC Duplex and ST (also BFOC).
Forwarding
The process whereby frames are relayed from one port to
another in the switch.
Frame
A frame is a data transmission frame on the link layer
(layer 2 in the OSI model), which includes the header and
trailer information that the bits transmission layer requires
for transmission. All frame formats together form the start
delimiter of a frame, the destination and source address
(destination and source address), the data itself and an
errorchecking device (a frame check sequence). A maximum
of 1500 bytes, with VPN-information of 1524 bytes of
payload data per packet are possible in the Ethernet.
Full Duplex Operation
In full duplex operation or duplex operation both
communications partners can communicate bi-directionally
at the same time.
Gigabit Ethernet
A version of Ethernet operating at a data transmission rate of
1000 Mbps.
Hub
A hub is a data communications facility (DCE) that makes it
possible to connect three or more devices in a star topology.
Modern Ethernet installations hardly use hubs any more
but use switches for this purpose because of the higher
network output that occurs as a result and the predictable
transmission times.
IEEE
Association of American Engineers dealing with norm
issues.
IGMP snooping
A switch equipped with IGMP (Internet Group Multicast
Protocol) snooping can check whether join requests for a
multicast group occur behind the ports. If this is the case,
the port concerned is accepted in the forward table for this
group. This reduces the load on the network because the
switch does not ood all ports with multicast trafc.
Jabber
The jabber messaging protocol is a method in Ethernet
networks that prevents a station from occupying the
transmission medium for longer than permitted. The
jabber function is an element of the IEEE 802.3 standard
and provides an interrupt mechanism with which a MAU
(Medium Attachment Unit) is interrupted during the
transmission process when this transmits data on the cable
for longer than 30 ms, or the standard dened packet length
of 1518 bytes is exceeded. SQE (Signal Quality Error) signals
are sent to the terminal equipment at the same time as
the interruption and these cause the terminal equipment
to terminate the data transfer. An error function in which
a network component continuously sends meaningless
signals to the network is also known as a jabber.
LAN
(Local Area Network) local network e.g. within a building.
Link Integrity Test
This test ensures that the Ethernet link is connected
properly and that the signals are transmitted correctly. This
can be helpful but does not guarantee that the link is fully
functional.
Link Layer
The link layer in the OSI reference model.
Link Pulse
The NLP pulse is a recognition pulse that is transmitted
from 10Base-T-stations to 100Base-T stations for auto-
negotiation. The NLP is a periodic pulse with an interval of
16 +/– 8ms.
LLDP – Link Layer Discovery Protocol
LLDP is a layer-2 protocol in compliance with the
IEEE-802.1AB standard. It denes the possibilities for
exchanging information with neighbouring devices.
Information is periodically sent from supported devices
to all devices on the network. Neighbouring devices
which support LLDP are then able to receive this data
independently.
Glossary
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Technical appendix
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