Browsing: O
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OAM cell |
Operation, Administration, and
Maintenance cell. ATM Forum specification for cells used to
monitor virtual circuits. OAM cells provide a virtual circuit-level
loopback in which a router responds to the cells, demonstrating that
the circuit is up, and the router is operational.
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OARnet |
Ohio Academic Resources
Network. Internet service provider that connects a number
of U.S. sites, including the Ohio supercomputer center in Columbus,
Ohio.
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object instance |
Network management term referring to
an instance of an object type that has been bound to a value.
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OC |
Optical Carrier.
Series of physical protocols (OC-1, OC-2, OC-3, and so on), defined
for SONET optical signal transmissions. OC signal levels put STS
frames onto multimode fiber-optic line at a variety of speeds. The
base rate is 51.84 Mbps (OC-1); each signal level thereafter
operates at a speed divisible by that number (thus, OC-3 runs at
155.52 Mbps). See also
SONET,
STS-1,
and STS-3c.
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octet
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8 bits. In networking, the term octet is often used (rather than byte) because some machine architectures employ bytes that are not 8 bits long.
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ODA |
Open Document Architecture.
ISO standard that specifies how documents are represented and
transmitted electronically. Formally called Office Document
Architecture.
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ODI |
Open Data-Link Interface.
Novell specification providing a standardized interface for NICs
(network interface cards) that allows multiple protocols to use a
single NIC. See also
NIC
(network interface card).
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OEMI channel |
See
block
multiplexer channel.
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Office Document Architecture |
See
ODA.
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Ohio Academic Resources Network |
See
OARnet.
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OIM |
OSI Internet Management.
Group tasked with specifying ways in which OSI network management
protocols can be used to manage TCP/IP networks.
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OIR |
Online insertion and removal.
Feature that permits the addition, replacement, or removal of
interface processors in a Cisco router without interrupting the
system power, entering console commands, or causing other software
or interfaces to shut down. Sometimes called hot swapping.
See also power-on
servicing.
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ONC |
Open Network Computing.
Distributed applications architecture designed by Sun Microsystems,
currently controlled by a consortium led by Sun. The NFS protocols
are part of ONC. See also
NFS.
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ones density |
Scheme that allows a CSU/DSU to
recover the data clock reliably. The CSU/DSU derives the data clock
from the data that passes through it. In order to recover the clock,
the CSU/DSU hardware must receive at least one 1 bit value for every
8 bits of data that pass through it. Also called pulse density.
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online insertion and removal |
See
OIR.
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on-the-fly packet switching |
See
cut-through
packet switching. |
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open architecture |
Architecture with which third-party
developers can legally develop products and for which public domain
specifications exist.
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open circuit |
Broken path along a transmission
medium. Open circuits will usually prevent network communication.
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Open Data-Link Interface |
See
ODI.
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Open Document Architecture |
See
ODA.
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Open Network Computing
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See
ONC.
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Open Shortest Path First |
See
OSPF.
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Open System Interconnection |
See
OSI. |
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Open System Interconnection reference
model |
See
OSI
reference model.
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oper account |
One of the four default user accounts
that are created in the factory on each LightStream 2020 ATM switch.
The oper account is for general users. Its default interface is the
CLI.
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Operation, Administration, and
Maintenance cell |
See
OAM
cell.
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Option |
One currently defined: maximum TCP
segment size.
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Optical Carrier |
See
OC.
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optical fiber |
See
fiber-optic
cable.
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Organizational Unique Identifier |
See
OUI.
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oscillation |
Secondary signal on top of the 60-Hz
waveform. It has a magnitude that ranges from 15 % to 100 % of the
normal voltage carried on the power line. See
surge,
spike,
and sag.
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| OSI |
Open System Interconnection.
International standardization program created by ISO and ITU-T to
develop standards for data networking that facilitate multivendor
equipment interoperability.
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OSI Internet Management |
See
OIM.
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OSINET |
International association designed to
promote OSI in vendor architectures.
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OSI
Presentation Address |
Address used to locate an OSI Application entity. It consists of an OSI Network Address and up to three selectors, one each for use by the transport, session, and presentation entities.
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OSI reference model |
Open System Interconnection
reference model. Network architectural model developed by
ISO and ITU-T. The model consists of seven layers, each of which
specifies particular network functions such as addressing, flow
control, error control, encapsulation, and reliable message
transfer. The highest layer (the application layer) is closest to
the user; the lowest layer (the physical layer) is closest to the
media technology. The next to lowest layer are implemented in
hardware and software, while the upper five layers are implemented
only in software. The OSI reference model is used universally as a
method for teaching and understanding network functionality. Similar
in some respects to
SNA.
See application
layer,
data
link layer,
network
layer,
physical
layer,
presentation
layer,
session
layer, and
transport
layer.
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OSPF |
Open Shortest Path First.
Link-state, hierarchical IGP routing algorithm proposed as a
successor to RIP in the Internet community. OSPF features include
least-cost routing, multipath routing, and load balancing. OSPF was
derived from an early version of the ISIS protocol. See also
Enhanced
IGRP,
IGP,
IGRP,
IS-IS,
and RIP.
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OUI |
Organizational Unique
Identifier. The 3 octets assigned by the IEEE in a block of
48-bit LAN addresses.
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outframe
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Maximum number of outstanding frames
allowed in an SNA PU 2 server at any time.
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out-of-band
signaling |
Transmission using frequencies or
channels outside the frequencies or channels normally used for
information transfer. Out-of-band signaling is often used for error
reporting in situations in which in-band signaling can be affected
by whatever problems the network might be experiencing. Contrast
with in-band
signaling.
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