In the Extreme Networks implementation, each field replaceable component contains a system odometer counter in EEPROM.

On modular switches, using the CLI, you can display how long each following individual component has been in service:
  • chassis
  • MSMs
  • I/O modules
  • power controllers

On standalone switches, you display the days of service for the switch.


Orthogonal frequency division multiplexing, a method of digital modulation in which a signal is split into several narrowband channels at different frequencies. OFDM is similar to conventional frequency division multiplexing (FDM). The difference lies in the way in which the signals are modulated and demodulated. Priority is given to minimizing the interference, or crosstalk, among the channels and symbols comprising the data stream. Less importance is placed on perfecting individual channels. 
OFDM is used in European digital audio broadcast services. It is also used in wireless local area networks.


Object identifier.

option 82

This is a security feature that you configure as part of BOOTP/DHCP. Option 82 allows a server to bind the client's port, IP address, and MAC number for subscriber identification.


Open Systems Interconnection. OSI is an ISO standard for worldwide communications that defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, down through the presentation, session, transport, network, data link layer to the physical layer at the bottom, over the channel to the next station and back up the hierarchy.

OSI Layer 2

At the Data Link layer (OSI Layer 2), data packets are encoded and decoded into bits. The data link layer has two sub-layers:
  • The Logical Link Control (LLC) layer controls frame synchronization, flow control and error checking.
  • The Media Access Control (MAC) layer controls how a computer on the network gains access to the data and permission to transmit it.

OSI Layer 3

The Network layer (OSI Layer 3) provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, inter-networking, error handling, congestion control and packet sequencing.

OSI reference model

The seven-layer standard model for network architecture is the basis for defining network protocol standards and the way that data passes through the network. Each layer specifies particular network functions; the highest layer is closest to the user, and the lowest layer is closest to the media carrying the information. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer and ultimately to the end user or program. This model is used worldwide for teaching and implementing networking protocols.


Open Shortest Path First. An interior gateway routing protocol for TCP/IP networks, OSPF uses a link state routing algorithm that calculates routes for packets based on a number of factors, including least hops, speed of transmission lines, and congestion delays. You can also configure certain cost metrics for the algorithm. This protocol is more efficient and scalable than vector-distance routing protocols. OSPF features include least-cost routing, ECMP routing, and load balancing. Although OSPF requires CPU power and memory space, it results in smaller, less frequent router table updates throughout the network. This protocol is more efficient and scalable than vector-distance routing protocols.


OSPFv3 is one of the routing protocols used with IPV6 and is similar to OSPF.


Organizational(ly) Unique Identifier. The OUI is the first 24 bits of a MAC address for a network device that indicate a specific vendor as assigned by IEEE.