Specification Methodology. Andy Reid, BT

Transcription

1 Specification Methodology Andy Reid, BT

2 Background Many systems, including telecommunications systems are specified and interconnected functional blocks Underpinned by formal mathematics of systems engineering theory and automata theory However, there are the following difficulties Tend to exclusively specification which generally do not include any specification of behaviour. Methods of representing abstract views tend to apply to the design phase of a system and cannot be defined after a system is operational. There is no well-established method for representing the process of deploying, activating, and the operating a virtual function. Commonly used techniques for specification do not directly address these requirements Modelling techniques such as UML have developed with data centric constructs increasingly embedded in the language Modelling techniques, even BPMN and SysML, have become ever more focussed on the design (ie coding) phase at the expense of the operational phase Need a technique which is Natural and easy extension of current techniques Capable of supporting and defining virtualisation Capable of supporting abstract, even abstract implemented while run time operational Deductive rather than assertive Mathematically sound and robust

3 Virtualisation Key Specification Requirement Virtualisation of functional blocks results in Division of a functional block between a host function and a virtualised network function Creation of a new container interface between host and VFB Division of the interface between an infrastructure interface and a virtualised interface. The virtualised functional block (VFB) is not a functional block independent of it host function The container interface is not an interface between functional blocks equivalent to other. al al Virtualised Infrastructure al Virtualised al al virtualisation Virtualised Container s Infrastructure al Virtualised al al Bloak

4 Basic Construction of Virtual s ports ports A Compound B Binding A B C Compound Port assigned to constructed function (marked as in use for the context of the compound function) A Constructed function C B Port assigned to constructed function (marked as in use for the context of the compound function)

5 The Basic Mechanism Virtual function dynamic State Configured State = virtual function Container Transfer function transfer function Generic al Partitioning of to create container interface Virtual function dynamic Virtual function dynamic Configured State = virtual function Container Virtual /State function transfer function virtual Configured State = virtual function Virtual function Container Virtual /State function transfer function virtual transfer function transfer function Formation of transfer function for virtual function ed virtual function Note: functional block may be distributed, parallel, and concurrent

6 Virtualisation a Recursive, Unifying Construct Outward recursion as well as inward recursion Virtual function dynamic State Configured = virtual function Container transfer function Every functional block is a virtual functional block Everything is always a configuration of a host Completely unifying construct Process, object, network, connection, CPU, storage, etc, are all virtual functional blocks

7 Virtual Abstract Domain Specific Language Run-Time Abstraction The VFB is, by nature, abstract Every viable abstract function is a virtual function Every (abstract) VFB can be implemented on a wide variety of hosts functions virtual Virtual function dynamic Configured State = virtual function Virtual function Container Virtual /State function transfer function transfer function virtual Domain specific languages (DSLs) Every container interface defines a configuration language a domain specific language (DSL) The run time of every DSL is a host function DSLs are layered as VFBs are layered Virtual function dynamic Configured State = virtual function Container transfer function

8 Absolute Specification and Relative Specification al Equivalence, Π-Calculus VFB can have a formal, precise, absolute specification value range, output value range, value range, transition transfer function (pure logic specification) VFB can have formal, precise, specification relative to host VFB, ie its defining configuration running code, reference implementation Need to establish equivalence Conformance testing (the practical and every day solution) Formal methods (difficult to scale and implement) Mathematical definition of equivalence strong bi-similarity Need to create ante hoc and/or post hoc equivalence Ante hoc formal sub-sets of VFB specification Post hoc translation interpreter, script, compiler Should have equivalence to π-calculus new is equivalent to reconfiguration in host VFB

9 Shannon Information Kolmogorov Information Shannon Information Four separate sets of Shannon Information virtual Virtual function dynamic Configured State = virtual function Container virtual transfer function Kolmogorov Information Defined as The complexity of an output signal (assumes no input) Measured by Length of shortest programme to create output Applies to Configurable transfer functions virtual Kolmogorov Information Virtual function dynamic Configured State = virtual function Container /State transfer function virtual

10 Application eg ETSI NFV ISG VI Container VM and Virtual Net Container s Compute Container s Infrastructure Network Domain

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