Glossary
Network Layer
Level 3 of the seven level OSI reference model defined by ISO. This layer provides the routing of data through the network based on global addresses. Typical examples are IP and X.25.
Nibble
A nibble is four bits.
NRZI (Non-Return to Zero Invert)
Level 1 encoding mechanism in which a binary state is represented by a change of the level 1 signal condition. The other binary state is represented by a continuation of the level 1 signal. In wide area networking, the most common implementation of NRZI encoding is an option in IBM’s SDLC. In this case, a 0 is represented by a change in the level 1 signal. A binary 1 is represented by a continuation of the signal. In conjunction with a bit oriented level 2 link protocol, proper clocking may be derived by the receiver independent of DCE clocking.
Object
Any device that can be monitored or controlled by use of the SNMP protocol.
Octet
8 bits considered as a transmission element. Octets in general are not equivalent to user’s data bytes. “Octet” is more general than “Byte,” allowing for smaller elements to be contained (1 bit fields, 2 bit fields, and so forth.)
Octet
The common term used for a collection of 8 bits is a byte. In some cases, the term used is an octet. Although many people use these terms interchangeably, there are a few differences. The bits of a byte are normally numbered from 0 to 7. The bits of an octet are generally numbered from 1 to 8. While the 4th bit of both a byte and an octet are the same, bit 4 of each is a different bit.
OSI
Open Systems Interconnect. The 7 level communications structure promoted by ISO.
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