Terms used as applied to Data (and some Voice) Transmission over Copper Wire

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OC-1 (Optical Carrier Level-1) - Optical Signal (running on FIBER) that has been converted <typically> from DSX links. 28 DS1's combine to make one OC-1 channel (appx. 50Mbps)

See: SONET, DS-x

OC-3 (Optical Carrier Level-3) -- 3 each OC-1 channels combine to make an OC-3 channel (approx. 155Mbps)

OC-12 (Optical Carrier Level-12) -- 4 each OC-3 channels combine to make an OC-12 channel (approx. 620Mbps)See: DS-x and OC-x

OC-48 (Optical Carrier Level-48) -- 4 each OC-12 channels combine to make an OC-48 channel (approx. 2.48Ghz) Used for Long hauls between major network hubs.

OpenView -- System Network Management Tool developed by Hewlett Packard. May be used for LAN, Wan and Hardware management via SNMP Agents. Other top programs: TME(IBM); CA-Unicenter(Computer Associates).

OPTIS (Overlapped PAM Transmission with Interlocking Spectra) -- OPTIS is the 16 level PAM (Pulse Amplitude Modulation) line coding technique adopted for the ANSI T1E1.4 "HDSL2" standard. A central component of the OPTIS standard proposal is a spectrally-shaped waveform that attempts to not interfere with existing 2B1Q, T1(AMI), HDSL or ADSL (Asymmetric Digital Subscriber Line) services, while providing good performance even in worst case environments containing a mixture of other signals. CAP/QAM and OPTIS have been the only modulations that have been able to make the claim. Network service providers will be able to install OPTIS (HDSL2) equipment without being required to upgrade or redesign their cable plant. OPITS is targeted to provide full T1 or E1 over a single pair with the same reach as two pair HDSL - approximately 12,000ft.

OSI (Open Systems Interconnection) -- OSI is a standard model for the functional layering of a communications system. Currently, it is Recommendation X.200 of the CCITT (the international telecommunications standards-making body). Although many existing hardware and software products have been developed on a slightly different model, the OSI model is generally respected as the standard to aspire to in building future products.

OSI has a seven layer model:

  • Layer 1 - The physical Layer: This layer conveys the bit stream through the network at the electrical and mechanical level.
  • Layer 2 - The link (or data-link) layer: This layer provides error control and synchronization for the physical level and performs bit-stuffing for strings of 1's in excess of 5.
  • Layer 3 - The network layer: This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level).
  • Layer 4 - The transport layer: This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error checking.
  • Layer 5 - The session layer: This layer manages the establishment of a continuing series of requests and responses between the applications at each end.
  • Layer 6 - The presentation layer: A layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text).
  • Layer 7 - The application layer: The layer at which a user and a computer interface to a network view a message or data request or response.

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Copyright 1997-2008 Floyd Kling 
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