OADM
Optical Add & Drop Multiplexer

OC
Optical Carrier

ODBC
Open Database Computing Driver

OEIC
Opto-Electronic Integrated Circuit

OLA
Optical Line Amplification

OLTP
Online Transaction Processing

OLTS
Optical Loss Test Sets

O-MSP
Optical Multiplex Section Protection

ONI
Optical Network Interface

OPC
Originating Point Code

OPX
Off-Premises Extension

OSI
Open Systems Interconnection
The OSI Layers
      7) Application
      6) Presentation
      5) Session
      4) Transport
      3) Network
      2) Data Link
      1) Physical

   Comment:
   Network architecture developed by the International Standards Organization.

   Physical
   Responsible for the transmission of unstructured bit streams over a physical
  network.  This covers the mechanical, electrical and procedural characteristics
  required to establish, maintain and deactivate physical links. This level defines electrical
  and mechanical characteristics, and interfaces between network medium and network
  devices.

  Data Link
   Controls physical layer data flow. Responsible for the error free transmission and
  establishing logical connections between workstations. This is achieved by packaging
  raw bits from the physical layer into blocks of data - frames - and sending these frames
  with the necessary synchronization, error control and flow control.

  Network
   Addresses and routes packets. Responsible for addressing and control functions -
  routing, necessary to move data though the network. This covers establishing,
  maintaining and terminating connections including packet switching, routing, data
  congestion, re-assembly of data and translation of logical addresses to physical
  addresses.

  Transport
   Manage network layer connections Provides reliable packet delivery mechanism.
  Responsible for reliable, transparent transfer of data between end points. Providing
  end-to-end recovery and flow control, it deals with packet handling, repackaging of
  messages, dividing messages into smaller packets and error handling.

  Session
   Manages user sessions Reports upper-layer errors. Responsible of support connection
  between sessions, administrative tasks and security. Providing the control structure for
  communication between applications, it establishes, manages and terminates
  connections - sessions - between co-operating applications.

  Presentation    
  Specifies architecture-independent data transfer format. Encodes and decodes data;
  Encrypts and decrypts data; Compresses data. Responsible for meaningful transfer of
  data. Performing generally useful transformation on data to provide a standardized
  application interface and common communications services. It also provides services
  such as encryption, text compression and reformatting.

   Application
   Provides interface to end-user processes. Provides standardized services to
  applications. Responsible for the interaction with the operating system and providing
  interface to the system- eg. FTP, Telnet, SMTP, Serving as a window for application to
  access network services, it handles general network access, flow control, error
  recovery and file transfers.

   
   NETWORK PROTOCOL LAYERS

OSI-RM
OSI Reference Model

OSI-TP
OSI Transaction Processing

OSI/CS
OSI Communication Subsystem

OSI/FS
OSI File Services - IBM ¨

OSIE
OSI Environment - ISO

OSPF
Open Shortest Path First
Link state, hierarchical IGP routing algorithm proposed as a successor to RIP in the
Internet community. OSPF's feature include least-cost routing, multipath routing, and
load balancing. OSPF was derived from an early version of OSI's IS IS protocol.

OUNI
Optical User Network Interface

OUTWATS
Outgoing Wide-Area Telephone Service