Overview: Software System Architecture Software System Test

1. Overview:Software System ArchitectureSoftware System Test Mike O’Dell Based on an earlier presentation by Bill Farrior, UTA, modified by Mike O’Dell

2. What is System Design? • A progressive definition of how a system will be constructed: • Guiding principles/rules for design (Meta-architecture) • Top-level structure, design abstraction (Architecture Design) • Details of all lowest-level design elements (Detailed Design) CSE 4317

3. What is Software Architecture? • A critical bridge between what a system will do/look like, and how it will be constructed • A blueprint for a software system and howit will be built • An abstraction: a conceptual model of what must be done to construct the software system • It is NOT a specification of the details of the construction CSE 4317

4. What is Software Architecture? • The top-level breakdown of how a system will be constructed: • design principles/rules • high-level structural components • high-level data elements (external/internal) • high-level data flows (external/internal) • Discussion: Architectural elements of the new ERB CSE 4317

5. System Architecture Design Process • Define guiding principles/rules for design • Define top-level components of the system structure (“architectural layers”) • Define top-level data elements/flows (external and between layers) • Deconstruct layers into major functional units (“subsystems”) • Translate top-level data elements/flows to subsystems CSE 4317

6. Layers/Services: application: supporting network applications ftp, smtp, http transport: host-host data transfer tcp, udp network: routing of datagrams from source to destination ip, routing protocols link: data transfer between neighboring network elements E.g., Ethernet, 802.11 WLAN physical: bits “on the wire” application transport network link physical Layer Example: The Internet Protocol Stack Architecture 1: Introduction

7. ICMP protocol • error reporting • router “signaling” • IP protocol • addressing conventions • datagram format • packet handling conventions • Routing protocols • path selection • RIP, OSPF, BGP routing table Subsystem Example: The Internet Network Layer Transport layer: TCP, UDP Network layer Link layer Physical layer 4: Network Layer

8. (PCF) (DCF) 1-2 Mbps Infrared, or 2.4-2.5 GHz Freq. hopping or DSSS (1997) 54 Mbps 5-6 GHz OFDM 802.11a (1999) 11 Mbps 2.4-2.5 GHz DSSS 802.11b (2000) 54/108 Mbps 2.4-2.5 GHz OFDM 802.11g/g+ (2003) 248 Mbps (2x2) 2.4/5 GHz MIMO w/ spacial mpx 802.11n (2008) Subsystem Example: IEEE 802.11 Architecture (Link Layer) Polling mode CSMA/CA mode 6: Wireless and Mobile Networks

9. duration depends on MAC load type duration depends on network condition MAC frame: Control, management , data + headers(size depends on frame load and type) PCF: Point Coordination Function (asynchronous, connectionless access) DCF: Distributed Coordination Function (connection oriented access) DIFS: DCF Inter Frame Space (minimum delay for asynchronous frame access) PIFS: PCF Inter Frame Space (minimum poll timing interval) SIFS: Short IFS (minimum timing for high priority frame access as ACK, CTS, MSDU…) MSDU: MAC Service Data Unit Reference: W. Stallings: Data and Computer Communications, 7th ed IEEE 802.11 MAC (Detailed Design) Timing in Basic Access 6: Wireless and Mobile Networks

10. Criteria for a Good Architecture(The Four I’s) • Independence – the layers are independent of each other and each layer’s functions are internally-specific and have little reliance on other layers. Changes in the implementation of one layer should not impact other layers. • Interfaces/Interactions – the interfaces and interactions between layers are complete and well-defined, with explicit data flows. • Integrity – the whole thing “hangs together”. It’s complete, consistent, accurate… it works. • Implementable – the approach is feasible, and the specified system can actually be designed and built using this architecture. CSE 4317

11. How do you Document a Software Architecture? • Describe the “rules” : meta-architecture • guiding principles, vision, concepts • key decision criteria • Describe the layers • what they do, how they interact with other layers • what are they composed of (subsystems) CSE 4317

12. How do you Document a Software Architecture? • Describe the data flows between layers • what are the critical data elements • provider subsystems (sources) and consumer subsystems (sinks) • Describe the subsystems within each layer • what does it do • what are its critical interfaces of the subsystem, within and external to its layer • what are its critical interfaces outside the system CSE 4317

13. Final Thoughts – Verification System Definition DDS: Detailed Design Specification SRD: System Requirements ADS: Architecture Specification Implementation MAP: All Module Interfaces & Interactions MAP: All Subsystem & Layer Interfaces & Interactions MAP: All Specified Requirements MAP: All Modules System Validation Test Integration Test Unit Test Component Test (a.k.a. Function Test) System Verification CSE 4317

14. Final Thoughts – Verification • Unit Test: verifies that EVERY module (HW/SW) specified in the DDS operates as specified. • Component/Function Test: verifies integrity of ALL inter-module interfaces and interactions. • Integration Test:verifies integrity of ALL inter-subsystem interfaces and interactions. • System Verification Test: verifies ALL requirements are met. CSE 4317