1. Information that is delivered as a unit among peer entities of a network and that may contain control information, address information, or data.
2. In layered systems, a unit of data that is specified in a protocol of a given layer and that consists of protocol-control information of the given layer and possibly user data of that layer.

The first octet of the packet header that identifies the protocol used to transport the frame. [T1.509-1995]

In open systems architecture, the distribution of network protocol among the various layers of the network. [From Weik '89]

In a communications system, the collection of hardware, software, firmware, or any combination of these, that is required or used to convert the protocols used in one network to those used in another network. [From Weik '89]

1. The queries and replies among communications equipment to determine the respective capabilities of each end of the communications link.
2. For layered systems, information exchanged between entities of a given layer, via the service provided by the next lower layer, to coordinate their joint operation.

1. A pre-production, functioning specimen(s) that is the first of its type, typically used for the evaluation of design, performance, and/or production potential.
2. A model suitable for evaluation of design, performance, and production potential. [JP 1-02]

1. In telecommunications, the setting in place and configuring of the hardware and software required to activate a telecommunications service for a customer; in many cases the hardware and software may already be in place and provisioning entails only configuration tasks such as creating (or modifying) a customer record in a database and associating it with the service(s) and service… (Read More →)

1. See firewall.
2. [An] Application acting on behalf of another application or system in responding to protocol requests. [INFOSEC-99]
3. An entity in a system that acts on behalf of another entity in invoking some operation [ECMA138]

A program that deals with external servers on behalf of internal clients. Proxy clients talk to proxy servers, which relay approved client requests to real servers, and relay answers back to clients.

Network Performance, Reliability, and Quality of Service Committee