This glossary was written and prepared by Blair Bergum of  DNSnews.net
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OCx

Optical Carrier Levels (x), are the transmission levels for transmitting data over optical communication lines. The base rate is OC-1, which supports 51.94 Mbps.

OC-1

Optical Carrier Level-1, transmits digital signals on optical fiber at 51.94 Mbps. Also known as a DS3. See also DS3.

OC-3

Optical Carrier Level-3 transmits digital signals on optical fiber at fractional speeds of 60-155.52 Mbps (burstable speeds from 0-60 Mbps, and full bandwidth speeds of 155.52 Mbps) An OC-3 equals three DS-3's.

OC-12

Optical Carrier Level-12, transmits digital signals on optical fiber at fractional speeds of 140-622.08 Mbps (burstable speeds of 0-140 base speed, and up to 622.08 Mbps, and full bandwidth speeds of 622.08 Mbps). An OC-12 equals twelve DS-3's.

OC-24

Optical Carrier Level-24 transmits digital signals on optical fiber at 1.244 Gbps. An OC-24 equals 24 DS-3's.

OC-48

Optical Carrier Level-48, transmits digital signals on optical fiber at 2.488 Gbps. An OC-48 equals 48 DS-3's.

OC-192

Optical Carrier Level-192, transmits digital signals on optical fiber at 10 Gbps. An OC-192 equals 192 DS-3's.

octet

an octet is eight bits in length, and thus the word octet for eight. An octet is synonymous with a byte.

ODBC

Open Database Connectivity, is an open API for accessing a database.

ODI

Open Data-Link Interface, is a software interface so various protocols can share the same drivers and adapters in a server. ODI conforms to the OSI standard model. See also OSI.

OIA

Office of International Affairs

OIRA

Office of Information and Regulatory Affairs of the United States of America.

OMB

Office of Management and Budget of the United States of America.

on-demand streaming

content is stored and cached in files and is pre-loaded into edge servers.

one tier model

websites that store their data in the same file directory as the host's operating system (OS). See also two tier model and three tier model.

Open Database Connectivity

see ODBC.

Open Data-Link Interface

See ODI.

Open Systems Interconnection

See OSI.

open TLD’s

see unsponsored TLD’s.

optical fiber

is a fiber optic cable transmits data by transmitting light pulses on a glass or plastic wire.

OS

Operating System, is the software that allows computers and servers to operate and receive instructions from users.

OSI

Open Systems Interconnection, is a communications reference model developed to provide a guideline so enhanced telecommunication specifications and standards could be developed from this reference model. OSI was developed in 1983 and officially adopted by the ISO.

The OSI model describes seven layers involved in the communication of two end users on a network. These layers are as follows:

1) Physical Layer: includes the physical cabling media.

2) Data Link Layer: includes SLIP, PPP, 802.2 SNAP, or Ethernet II.

3) Network Layer: includes Internet Protocol ver 4 or ver 6.

4) Transport Layer: includes TCP or UDP Protocols.

5) Session Layer: includes POP/25, 532, 80, 20/21, 23, 53, 161/162, and RPC Portmapper.

6) Presentation Layer: includes POP/SMTP, Usenet, HTTP, FTP, Telnet, DNS, SNMP, and NFS.

7) Application Layer: includes E-mail, Newsgroups, Web Applications, File Transfers, Host Sessions, Directory Services, Network Management, and File Services.

Layers 1 through 3 are categorized as the "Lower Layers" and Layers 4 through 7 are categorized as the "Upper Layers".