APPENDIX A: GLOSSARY
This appendix defines terms associated with switching technology.
10BASE-T
The IEEE specification for 10 Mbps Ethernet over Category 3, 4, or 5 twisted-pair cable.
100BASE-FX
The IEEE specification for 100 Mbps Fast Ethernet over fiber-optic cable.
100BASE-TX
The IEEE specification for 100 Mbps Fast Ethernet over Category 5 twisted-pair cable.
1000BASE-SX
The IEEE specification for 1000 Mbps Gigabit Ethernet over fiber-optic cable.
1000BASE-T
The IEEE specification for 1000 Mbps Gigabit Ethernet over Category 5 twisted-pair cable.
Auto-negotiation
A feature that allows twisted-pair ports to advertise their capabilities for speed, duplex and flow control. When
connected to a port that also supports auto-negotiation, the link can automatically configure itself to the optimum
setup.
Auto Uplink
A feature that allows twisted-pair ports to sense if a normal (MDI-X) or uplink (MDI) connection is necessary and
make the right link. It adjusts for straight-through or crossover cables.
Backbone
The part of a network used as a primary path for transporting traffic between network segments.
Bandwidth
The information capacity, measured in bits per second that a channel could transmit. Bandwidth examples include
10 Mbps for Ethernet, 100 Mbps for Fast Ethernet, and 1000 Mbps (I Gbps) for Gigabit Ethernet.
Baud
The signaling rate of a line, that is, the number of transitions (voltage or frequency changes) made per second.
Also known as line speed.
Broadcast
A packet sent to all devices on a network.
Broadcast storm
Multiple simultaneous broadcasts that typically absorb all the available network bandwidth and can cause a
network to fail. Broadcast storms can be due to faulty network devices or network loops.
Capacity planning
Determining whether current solutions can satisfy future demands. Capacity planning includes evaluating potential
workload and infrastructure changes.
Class of Service
A term to describe treating different types of traffic with different levels of service priority. Higher priority traffic gets
faster treatment during times of switch congestion
Collision
A term used to describe two colliding packets in an Ethernet network. Collisions are a part of normal Ethernet
operation, but a sudden prolonged increase in the number of collisions can indicate a problem with a device,
particularly if it is not accompanied by a general increase in traffic.
End station
A computer, printer, or server that is connected to a network.
Ethernet
A LAN specification developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks
transmit packets at a rate of 10 Mbps.
Fast Ethernet
An Ethernet system that is designed to operate at 100 Mbps.
Gigabit Ethernet
An Ethernet system that is designed to operate at 1000 Mbps (1 Gbps).
Fault isolation
A technique for identifying and alerting administrators about connections (such as those associated with switch
ports) that are experiencing congestion or failure, or exceeding an administrator-defined threshold.
Forwarding
The process of sending a packet toward its destination using a networking device.
Filtering
The process of screening a packet for certain characteristics, such as source address, destination address, or
protocol. Filtering is used to determine whether traffic is to be forwarded, and can also prevent unauthorized access
to a network or network devices.
Flow control
A congestion- control mechanism. Congestion is caused by devices sending traffic to already overloaded port on a
switch. Flow control prevents packet loss and temporarily inhibits devices from generating more traffic until the
period of congestion ends.
Full-duplex
A system that allows packets to be transmitted and received at the same time and, in effect, doubles the potential
throughput of a link.
Half-duplex
A system that allows packets to transmitted and received, but not at the same time. Contrast with full duplex.
IEEE
Institute of Electrical and Electronics Engineers. This American organization was founded in 1963 and sets
standards for computers and communications.
IETF
Internet Engineering Task Force. An organization responsible for providing engineering solutions for TCP/IP
networks. In the network management area, this group is responsible for the development of the SNMP protocol.
IGMP
Internet Group Management Protocol, the standard for IP multicasting in the Internet. IGMP is used to establish
host memberships in multicast groups on a single network. (See IP multicast)
IP
Internet Protocol. IP is a layer 3 network protocol that is the standard for sending data through a network. IP is part
of the TCP/IP set of protocols that describe the routing of packets to addressed devices.
IP address
Internet Protocol address. A unique identifier for a device attached to a network using TCP/IP. The address is
written as four octets separated with periods (full-stops), and is made up of a network section, an optional subnet
section and a host section.
IP multicast
Sending data to distributed servers on a multicast backbone. For large amounts of data, IP Multicast is more
efficient than normal Internet transmissions, because the server can broadcast a message to many recipients
simultaneously. Unlike traditional Internet traffic that requires separate connections for each source-destination
pair, IP multicasting allows many recipients to share the same source. This means that just one set of packets is
transmitted for all the destinations.
LAN
Local Area Network. A network of end stations (such as PCs, printers, servers) and network devices (hubs and
switches) that cover a relatively small geographic area (usually not larger than a floor or building).
Load balancing
The ability to distribute traffic across various ports of a device, such as a switch, to provide efficient, optimized
traffic throughout the network.
Loop
An event that occurs when two network devices are connected by more than one path, thereby causing packets to
Page 15 of 19
