Basics of PPL

Excel’s Programmable Protocol Language (PPL) provides the ability to easily access and modify software operations on a per PPL component basis, giving the user full control over call processing. The PPL software load resides on system cards and consists of a state machine engine, default protocol state machines (*.ppl files) and atomic function/event libraries (*.exl files).

A PPL protocol is an association of a state/event table and a primitive table. The state machine engine uses the tables to drive PPL objects through various states in response to internal or external events.

You can customize protocols using the PPL Composer application, which provides a graphical representation of PPL state machines. Protocol variants can be developed easily by modifying default protocols that can be obtained from the Excel protocol library.

PPL protocols are independent of switch system software, allowing for the creation of new protocols without upgrading system software. This allows for quick changes required to manage network signaling variants. Protocols are created with high-level Atomic Functions (AF), abstracting the user from detailed implementation logic.

Multiple protocols can be defined for each PPL component and selectively assigned to each object being managed.

You should familiarize yourself with the following terms and acronyms used throughout this manual. Each is discussed in more detail within the manual.

PPL state machines use symbols to represent states, atomic functions, and events. These correspond to standard Specification and Description Language (SDL) symbols as shown in the figure below The PPL symbol for a state that is internal is denoted with an "I" in front of the "S".

See Programmable Protocol Language.

PPL. Excel feature allowing support of custom protocols, designed through a graphical interface tool. Protocol is defined by associating a State Event Table with a Primitive Table. See State Machine.

In PPL, a condition that, when met, drives a state machine (PPL Component) from one state to another, by invoking an associated Primitive. In PPL files, an Event is marked by an arrow and text.

See Atomic Function.

AF. A predefined PPL software routine that performs a single, simple task, such as "Transmit Line Signaling" or "Allocate Digit Buffer." It is composed of standard software interrupts, calls, and data formats used by applications. Each AF has two values named "Arguments." AFs 1-50 are generic, and apply to all PPL components. AFs 51 and above apply to specific components. An AF is called "Atomic" because it is the smallest useful unit in PPL.

Protocol layer of the CSP.

Call processing layer of the CSP.

Application layer of the CSP.

A computer, attached to the Excel platform through an RS-232 or Ethernet link, from which you run the telecommunications application that controls the Excel platform.

A programmable software component that uses PPL state machines that can be modified with the PPL Tool.

A system object that is controlled by a PPL state machine such as a channel, an ISDN D channel, or an SS7 link. Allows externally programmed custom protocols in Excel’s switching software, via GUI.

See Integrated Services Digital Network.

See Signaling System Number Seven.

Group of one or more Atomic Functions that allow multiple actions (tests) to be initiated in response to a PPL event for a channel. See Programmable Protocol Language.

The condition of a component at a given instant. The current "context" of a PPL object, such as Idle, Seizing, Answered. In PPL files, a State is represented by a circle.

A State Machine defines the events (functions) required to drive a channel from one state to another through a graphical interface tool. A State Machine is configured and managed using API Messages or the PPL Tool. Based on the occurrence of an Event, a State Machine drives each channel through its Protocol Tables. It creates one state from another, invoked by an event. Processing is complete when a "normal" state is reached. "Wait" and "Stable" are normal states.

AF	Atomic Function. A state machine software routine which normally performs one independent task.
*.ppl	File extension for PPL protocol data file used by the PPL Composer application.
Event	A condition that, when met, drives a state machine from one state to another.
*.exl	File extension for files containing the atomic function/event library for a PPL component.
INS	In Service
L3	Layer 3 (Network Signaling Protocol Layer)
L3P	Layer 3 Plus (interface between L3 and L4)
L4	Layer 4 (Call Processing Layer)
L5	Layer 5 (Host Application Layer)
OOS	Out of Service
PPL	Programmable Protocol Language. An Environment which allows for different software components within Excel’s switching platforms to be externally programmed and downloaded by the host application.
PPL Component	A programmable software component that uses PPL state machines that can be modified with the PPL Composer.
PPL Object	A system object that is controlled by a PPL state machine such as a channel, an ISDN D channel, or an SS7 link.
Primitive	A list of atomic functions invoked by a particular event.
Primitive Table	A list of all primitives used in a particular state machine.
Protocol	A state machine comprised of a state/event table and a primitive table.
State	The current "context" of a PPL object, such as Idle, Seizing, Answered.
State/Event Table	A table of all states used in a state machine and their associated events/primitives.