diff --git a/README.md b/README.md
index e1a78ac..f8a7754 100644
--- a/README.md
+++ b/README.md
@@ -104,8 +104,27 @@ This project is licensed under the MIT License - see the [LICENSE](LICENSE) file
 ```
 timpani/
 ├── README.md                    # This file - main project overview
+├── doc/                         # 📚 Comprehensive documentation
+│   ├── README.md               # Documentation guide
+│   ├── architecture/           # Architecture documentation
+│   │   ├── HLD/               # High-Level Design
+│   │   │   ├── timpani_system_design_document.md
+│   │   │   └── timpani_rust_grpc_architecture.md
+│   │   └── LLD/               # Low-Level Design
+│   │       ├── timpani-o/     # Orchestrator components (10 docs)
+│   │       └── timpani-n/     # Node executor components (10 docs)
+│   ├── features/              # Feature & Requirements
+│   │   ├── timpani_features.md
+│   │   └── requirements/timpani_requirements.md
+│   ├── docs/                  # Implementation guides
+│   │   ├── api.md
+│   │   ├── getting-started.md
+│   │   └── developments.md
+│   └── contribution/          # Contribution guidelines
+│       ├── coding-rule.md
+│       └── guidelines-en.md
 ├── sample-apps/
-│   ├── README.md               # Sample applications documentation
+│   └── README.md               # Sample applications documentation
 ├── timpani-n/
 │   ├── README.md               # C implementation: Node executor
 │   ├── README.CentOS.md       # CentOS setup guide
diff --git a/doc/README.md b/doc/README.md
index e1b96b4..bcb1f8e 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -8,7 +8,7 @@
 **Document Information:**
 - **Issuing Author:** Eclipse timpani Team
 - **Configuration ID:** timpani-doc-index
-- **Document Status:** Published
+- **Document Status:** Draft
 - **Last Updated:** 2026-05-13
 
 ---
@@ -17,6 +17,7 @@
 
 | Version | Date | Comment | Author | Approver |
 |---------|------|---------|--------|----------|
+| 0.0b | 2026-05-13 | Added HLD section with system design and gRPC architecture | LGSI-KarumuriHari | - |
 | 0.0a | 2026-05-13 | Initial documentation guide | Eclipse timpani Team | - |
 
 ---
@@ -38,10 +39,16 @@ This documentation provides a comprehensive guide to the timpani project's migra
 ### 1️⃣ **Architecture Documentation**
 📁 [`architecture/`](architecture/)
 
-System architecture, communication protocols, and high-level design documentation.
+System architecture, communication protocols, and design documentation.
 
-- [timpani Architecture](architecture/timpani_architecture.md) - Overall system architecture
-- [gRPC Architecture](architecture/grpc_architecture.md) - Communication layer design
+#### High-Level Design (HLD) Documents
+📁 [`architecture/HLD/`](architecture/HLD/)
+
+System-level architecture and technology integration documentation.
+
+**System Architecture:**
+- [timpani System Design Document](architecture/HLD/timpani_system_design_document.md) - Overall system architecture, components, deployment
+- [timpani gRPC Integration Architecture](architecture/HLD/timpani_rust_grpc_architecture.md) - D-Bus → gRPC migration, communication flow, performance
 
 #### Low-Level Design (LLD) Documents
 📁 [`architecture/LLD/`](architecture/LLD/)
@@ -76,11 +83,25 @@ Component-level LLD documents comparing legacy C/C++ with Rust implementations.
   - 10: Data Structures
   - [README](architecture/LLD/timpani-n/README.md) - Component overview & migration status
 
-**🔍 Focus:** Understand system architecture and component-level AS-IS vs WILL-BE comparisons
+**🔍 Focus:**
+- **HLD:** System-level architecture, technology stack, deployment patterns
+- **LLD:** Component-level AS-IS vs WILL-BE comparisons, implementation details
+
+---
+
+### 2️⃣ **Feature Specifications & Requirements**
+📁 [`features/`](features/)
+
+System feature breakdown and requirements documentation.
+
+- [timpani Feature Specification](features/timpani_features.md) - Feature breakdown with mermaid diagrams, 3-level feature tables
+- [timpani Requirements Specification](features/requirements/timpani_requirements.md) - Functional and non-functional requirements
+
+**🔍 Focus:** Understand system capabilities, feature mapping, and requirement traceability
 
 ---
 
-### 2️⃣ **Implementation Documentation**
+### 3️⃣ **Implementation Documentation**
 📁 [`docs/`](docs/)
 
 Detailed developer guides, APIs, and development workflows.
@@ -95,7 +116,7 @@ Detailed developer guides, APIs, and development workflows.
 
 ---
 
-### 3️⃣ **Contribution Guidelines**
+### 4️⃣ **Contribution Guidelines**
 📁 [`contribution/`](contribution/)
 
 Development standards, coding rules, and workflow guidelines.
@@ -111,39 +132,47 @@ Development standards, coding rules, and workflow guidelines.
 
 ```mermaid
 graph TD
-    subgraph "1. Architecture Phase"
-        A1[System Architecture<br/>timpani_architecture.md]
-        A2[gRPC Architecture<br/>grpc_architecture.md]
+    subgraph "1. Features & Requirements"
+        F1[Feature Specification<br/>features/timpani_features.md]
+        F2[Requirements Specification<br/>features/requirements/timpani_requirements.md]
+    end
+
+    subgraph "2. High-Level Architecture"
+        HLD1[System Design Document<br/>HLD/timpani_system_design_document.md]
+        HLD2[gRPC Integration Architecture<br/>HLD/timpani_rust_grpc_architecture.md]
     end
 
-    subgraph "2. Component LLD"
-        H1[timpani-o LLD<br/>10 Components]
-        H2[timpani-n LLD<br/>10 Components]
-        H3[AS-IS vs WILL-BE<br/>Comparisons]
+    subgraph "3. Component LLD"
+        LLD1[timpani-o LLD<br/>10 Components]
+        LLD2[timpani-n LLD<br/>10 Components]
+        LLD3[AS-IS vs WILL-BE<br/>Comparisons]
     end
 
-    subgraph "3. Implementation Phase"
+    subgraph "4. Implementation Phase"
         I1[API Documentation]
         I2[Getting Started]
         I3[Development Guide]
         I4[Project Structure]
     end
 
-    subgraph "4. Quality Assurance"
+    subgraph "5. Quality Assurance"
         Q1[Coding Standards]
         Q2[Review Process]
         Q3[Release Guide]
     end
 
-    A1 --> H1
-    A1 --> H2
-    A2 --> H1
-    A2 --> H2
+    F1 --> F2
+    F2 --> HLD1
+    F2 --> HLD2
+    HLD1 --> LLD1
+    HLD2 --> LLD1
+    HLD1 --> LLD2
+    HLD2 --> LLD2
 
-    H1 --> H3
-    H2 --> H3
+    LLD1 --> LLD3
+    LLD2 --> LLD3
 
-    H3 --> I1
+    LLD3 --> I1
     I1 --> I2
     I2 --> I3
     I3 --> I4
@@ -152,8 +181,9 @@ graph TD
     Q1 --> Q2
     Q2 --> Q3
 
-    style A1 fill:#e3f2fd
-    style H3 fill:#e8f5e8
+    style F1 fill:#fff9c4
+    style HLD1 fill:#e3f2fd
+    style LLD3 fill:#e8f5e8
     style I1 fill:#fff3e0
     style Q3 fill:#f3e5f5
 ```
@@ -166,12 +196,17 @@ graph TD
 eclipse_timpani/
 ├── doc/                          # 📚 All documentation (YOU ARE HERE)
 │   ├── README.md                 # This file
-│   ├── architecture/             # Architecture & LLD documentation
-│   │   ├── timpani_architecture.md
-│   │   ├── grpc_architecture.md
+│   ├── architecture/             # Architecture documentation
+│   │   ├── HLD/                  # High-Level Design documents
+│   │   │   ├── timpani_system_design_document.md
+│   │   │   └── timpani_rust_grpc_architecture.md
 │   │   └── LLD/                  # Low-Level Design documents
-│   │       ├── timpani-o/        # timpani-o component LLDs
-│   │       └── timpani-n/        # timpani-n component LLDs
+│   │       ├── timpani-o/        # timpani-o component LLDs (10 docs)
+│   │       └── timpani-n/        # timpani-n component LLDs (10 docs)
+│   ├── features/                 # Feature & Requirements
+│   │   ├── timpani_features.md
+│   │   └── requirements/
+│   │       └── timpani_requirements.md
 │   ├── docs/                     # Implementation guides
 │   │   ├── api.md
 │   │   ├── getting-started.md
@@ -196,10 +231,12 @@ eclipse_timpani/
 
 ## 🔍 Development Checklist
 
-### Step 1: Architecture Review
-- [ ] System architecture documentation is complete and accurate
-- [ ] gRPC architecture addresses all communication requirements
-- [ ] Component boundaries are clearly defined
+### Step 1: High-Level Architecture Review
+- [ ] HLD: System design documentation is complete and accurate
+- [ ] HLD: gRPC architecture addresses all communication requirements
+- [ ] HLD: Technology stack and deployment patterns documented
+- [ ] Feature specifications with mermaid diagrams reviewed
+- [ ] Requirements (FR/NFR) traceability established
 
 ### Step 2: Component LLD Review
 - [ ] AS-IS architecture accurately reflects legacy implementation (C/C++)
@@ -230,9 +267,9 @@ eclipse_timpani/
 - Consult [GitHub Issues](https://github.com/eclipse-timpani/timpani/issues)
 
 ### For Architecture Clarifications
-- Refer to [timpani Architecture](architecture/timpani_architecture.md)
-- Review [gRPC Architecture](architecture/grpc_architecture.md)
-- Check component LLDs in [LLD/timpani-o/](architecture/LLD/timpani-o/) or [LLD/timpani-n/](architecture/LLD/timpani-n/)
+- **HLD:** Review [System Design Document](architecture/HLD/timpani_system_design_document.md) or [gRPC Architecture](architecture/HLD/timpani_rust_grpc_architecture.md)
+- **Features:** Check [Feature Specification](features/timpani_features.md) or [Requirements](features/requirements/timpani_requirements.md)
+- **LLD:** Check component LLDs in [LLD/timpani-o/](architecture/LLD/timpani-o/) or [LLD/timpani-n/](architecture/LLD/timpani-n/)
 
 ### For Development Queries
 - Review architecture documentation: `architecture/` → `LLD/` → `docs/`
diff --git a/doc/architecture/timpani_rust_grpc_architecture.md b/doc/architecture/HLD/timpani_rust_grpc_architecture.md
similarity index 80%
rename from doc/architecture/timpani_rust_grpc_architecture.md
rename to doc/architecture/HLD/timpani_rust_grpc_architecture.md
index 968c016..f209f73 100644
--- a/doc/architecture/timpani_rust_grpc_architecture.md
+++ b/doc/architecture/HLD/timpani_rust_grpc_architecture.md
@@ -8,8 +8,8 @@
 **Document Information:**
 - **Issuing Author:** Eclipse timpani Team
 - **Configuration ID:** timpani-arch-grpc
-- **Document Status:** Published
-- **Last Updated:** 2026-05-13
+- **Document Status:** Draft
+- **Last Updated:** 2026-05-14
 
 ---
 
@@ -17,6 +17,8 @@
 
 | Version | Date | Comment | Author | Approver |
 |---------|------|---------|--------|----------|
+| 0.0c | 2026-05-14 | Updated legend color scheme: gRPC communication links styled with orange (#f57c00) | LGSI-KarumuriHari | - |
+| 0.0b | 2026-05-13 | Added diagram legends highlighting timpani-o and timpani-n scope | LGSI-KarumuriHari | - |
 | 0.0a | 2026-05-13 | Initial gRPC architecture documentation | Eclipse timpani Team | - |
 
 ---
@@ -110,11 +112,11 @@ graph TB
     TimpaniO <-->|"D-Bus libtrpc<br/>(custom serialization)"| Node2
     TimpaniO <-->|"D-Bus libtrpc<br/>(custom serialization)"| NodeN
 
-    style Pullpiri fill:#e1f5ff
-    style TimpaniO fill:#ffe1e1
-    style Node1 fill:#e1ffe1
-    style Node2 fill:#e1ffe1
-    style NodeN fill:#e1ffe1
+    style Pullpiri fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style TimpaniO fill:#ffe1e1,stroke:#d32f2f,stroke-width:3px
+    style Node1 fill:#e1ffe1,stroke:#388e3c,stroke-width:3px
+    style Node2 fill:#e1ffe1,stroke:#388e3c,stroke-width:3px
+    style NodeN fill:#e1ffe1,stroke:#388e3c,stroke-width:3px
 ```
 
 **Issues:**
@@ -143,16 +145,29 @@ graph TB
         NodeN["Node N<br/>timpani-n<br/>(gRPC Client)"]
     end
 
+    subgraph Legend[" "]
+        L1["timpani-o (Our Scope)"]
+        L2["timpani-n (Our Scope)"]
+        L3["gRPC Communication (Our Scope)"]
+        L4["External Systems"]
+    end
+
     Pullpiri <-->|"gRPC<br/>SchedInfoService<br/>FaultService"| TimpaniO
     TimpaniO <-->|"gRPC/HTTP2<br/>NodeService"| Node1
     TimpaniO <-->|"gRPC/HTTP2<br/>NodeService"| Node2
     TimpaniO <-->|"gRPC/HTTP2<br/>NodeService"| NodeN
 
-    style Pullpiri fill:#e1f5ff
-    style TimpaniO fill:#ffd4a3
-    style Node1 fill:#c8e6c9
-    style Node2 fill:#c8e6c9
-    style NodeN fill:#c8e6c9
+    style Pullpiri fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style TimpaniO fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style Node1 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style Node2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style NodeN fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style L2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L3 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style L4 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+
+    linkStyle 0,1,2,3 stroke:#f57c00,stroke-width:3px,color:#f57c00
 ```
 
 **Improvements:**
@@ -210,6 +225,13 @@ graph TB
         SchedLoopN --> BPFN
     end
 
+    subgraph Legend[" "]
+        L1["timpani-o (Our Scope)"]
+        L2["timpani-n (Our Scope)"]
+        L3["gRPC Communication (Our Scope)"]
+        L4["External Systems"]
+    end
+
     SchedInfoClient -->|"gRPC :50051<br/>AddSchedInfo"| SchedInfoSvc
     FaultServer <-->|"gRPC :50052<br/>NotifyFault"| TimpaniO
 
@@ -217,11 +239,31 @@ graph TB
     NodeClient2 <-->|"gRPC :50051<br/>NodeService"| NodeSvc
     NodeClientN <-->|"gRPC :50051<br/>NodeService"| NodeSvc
 
-    style PullpiriSystem fill:#e1f5ff
-    style TimpaniO fill:#ffd4a3
-    style Node1 fill:#c8e6c9
-    style Node2 fill:#c8e6c9
-    style NodeN fill:#c8e6c9
+    style PullpiriSystem fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style SchedInfoClient fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style FaultServer fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style TimpaniO fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style SchedInfoSvc fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style GlobalSched fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style NodeSvc fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style Node1 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style Node2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style NodeN fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style NodeClient1 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style SchedLoop1 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style BPF1 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style NodeClient2 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style SchedLoop2 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style BPF2 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style NodeClientN fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style SchedLoopN fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style BPFN fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style L1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style L2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L3 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style L4 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+
+    linkStyle 8,9,10,11,12 stroke:#f57c00,stroke-width:3px,color:#f57c00
 ```
 
 ### Layer Diagram
@@ -250,6 +292,13 @@ graph TD
         Kernel["Linux Kernel<br/>• sched_setscheduler<br/>• sched_setaffinity<br/>• eBPF subsystem<br/>• POSIX timers"]
     end
 
+    subgraph Legend[" "]
+        L1["timpani-o (Our Scope)"]
+        L2["timpani-n (Our Scope)"]
+        L3["gRPC Communication (Our Scope)"]
+        L4["External Systems"]
+    end
+
     Pullpiri --> Services
     HTTP2 --> TimpaniO
     HTTP2 --> TimpaniN
@@ -257,10 +306,24 @@ graph TD
     TimpaniN --> Kernel
     WorkloadApps -.->|scheduled by| TimpaniN
 
-    style AppLayer fill:#e3f2fd
-    style gRPCLayer fill:#fff3e0
-    style BusinessLayer fill:#f1f8e9
-    style OSLayer fill:#fce4ec
+    style AppLayer fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style Pullpiri fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style WorkloadApps fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style gRPCLayer fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style Services fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style Tonic fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style HTTP2 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style BusinessLayer fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style TimpaniO fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style TimpaniN fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style OSLayer fill:#fce4ec,stroke:#c2185b,stroke-width:2px
+    style Kernel fill:#fce4ec,stroke:#c2185b,stroke-width:2px
+    style L1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style L2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L3 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style L4 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+
+    linkStyle 0,1,2,3,4 stroke:#f57c00,stroke-width:3px,color:#f57c00
 ```
 
 ---
diff --git a/doc/architecture/timpani_architecture.md b/doc/architecture/HLD/timpani_system_design_document.md
similarity index 73%
rename from doc/architecture/timpani_architecture.md
rename to doc/architecture/HLD/timpani_system_design_document.md
index d9c9251..b9f8d63 100644
--- a/doc/architecture/timpani_architecture.md
+++ b/doc/architecture/HLD/timpani_system_design_document.md
@@ -3,13 +3,13 @@
 * SPDX-License-Identifier: MIT
 -->
 
-# timpani System Architecture
+# timpani System Design Document
 
 **Document Information:**
 - **Issuing Author:** Eclipse timpani Team
 - **Configuration ID:** timpani-arch-system
-- **Document Status:** Published
-- **Last Updated:** 2026-05-13
+- **Document Status:** Draft
+- **Last Updated:** 2026-05-14
 
 ---
 
@@ -17,15 +17,13 @@
 
 | Version | Date | Comment | Author | Approver |
 |---------|------|---------|--------|----------|
+| 0.0c | 2026-05-14 | Updated diagram legends with consistent color scheme across all diagrams | LGSI-KarumuriHari | - |
+| 0.0b | 2026-05-13 | Added diagram legends highlighting timpani-o and timpani-n scope | LGSI-KarumuriHari | - |
 | 0.0a | 2026-05-13 | Initial system architecture documentation | Eclipse timpani Team | - |
 
 ---
 
-**Document Version:** 1.0
-**Last Updated:** May 12, 2026
-**Status:** Living Document
 
----
 
 ## System Overview
 
@@ -63,6 +61,13 @@ graph TB
         E2[Fault Manager]
     end
 
+    subgraph Legend[" "]
+        L1["timpani-o (Our Scope)"]
+        L2["timpani-n (Our Scope)"]
+        L3["Communication Layer"]
+        L4["External Systems"]
+    end
+
     O1 --> O2
     O1 --> O3
     O4 --> O1
@@ -78,10 +83,24 @@ graph TB
     N2 --> E1
     N4 --> O6
 
-    style O1 fill:#e3f2fd
-    style N1 fill:#e8f5e9
-    style O6 fill:#fff3e0
-    style N6 fill:#fff3e0
+    style O1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style O2 fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style O3 fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style O4 fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style O5 fill:#e3f2fd,stroke:#1976d2,stroke-width:2px
+    style N1 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style N2 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style N3 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style N4 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style N5 fill:#e8f5e9,stroke:#388e3c,stroke-width:2px
+    style O6 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style N6 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style E1 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style E2 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style L1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style L2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L3 fill:#fff3e0,stroke:#f57c00,stroke-width:2px
+    style L4 fill:#f5f5f5,stroke:#757575,stroke-width:2px
 ```
 
 ---
@@ -197,13 +216,25 @@ graph LR
         FM[Fault Manager]
     end
 
+    subgraph Legend[" "]
+        L1["timpani-o (Our Scope)"]
+        L2["timpani-n (Our Scope)"]
+        L3["External Systems"]
+    end
+
     N1 <-->|gRPC<br/>:50054| TO
     N2 <-->|gRPC<br/>:50054| TO
     TO <-->|gRPC| FM
 
-    style TO fill:#e3f2fd
-    style N1 fill:#e8f5e9
-    style N2 fill:#e8f5e9
+    style TO fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style N1 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style N2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style A1 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style A2 fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style FM fill:#f5f5f5,stroke:#757575,stroke-width:2px
+    style L1 fill:#e3f2fd,stroke:#1976d2,stroke-width:3px
+    style L2 fill:#e8f5e9,stroke:#388e3c,stroke-width:3px
+    style L3 fill:#f5f5f5,stroke:#757575,stroke-width:2px
 ```
 
 ---
diff --git a/doc/docs/structure.md b/doc/docs/structure.md
index 5b39d9b..87fe499 100644
--- a/doc/docs/structure.md
+++ b/doc/docs/structure.md
@@ -9,7 +9,7 @@
 **Document Information:**
 - **Issuing Author:** Eclipse timpani Team
 - **Configuration ID:** timpani-doc-structure
-- **Document Status:** Published
+- **Document Status:** Draft
 - **Last Updated:** 2026-05-13
 
 ---
@@ -18,6 +18,7 @@
 
 | Version | Date | Comment | Author | Approver |
 |---------|------|---------|--------|----------|
+| 0.0b | 2026-05-13 | Added HLD section and features/requirements documentation | LGSI-KarumuriHari | - |
 | 0.0a | 2026-05-13 | Initial structure documentation | Eclipse timpani Team | - |
 
 ---
@@ -39,11 +40,16 @@ timpani/
 ├── doc/
 │   ├── README.md                    # Documentation guide
 │   ├── architecture/
-│   │   ├── timpani_architecture.md  # System architecture
-│   │   ├── grpc_architecture.md     # gRPC design
+│   │   ├── HLD/                     # High-Level Design documents
+│   │   │   ├── timpani_system_design_document.md
+│   │   │   └── timpani_rust_grpc_architecture.md
 │   │   └── LLD/                     # Low-Level Design documents
 │   │       ├── timpani-o/           # timpani-o component LLDs (10 docs)
 │   │       └── timpani-n/           # timpani-n component LLDs (10 docs)
+│   ├── features/
+│   │   ├── timpani_features.md      # Feature specification
+│   │   └── requirements/
+│   │       └── timpani_requirements.md  # FR/NFR requirements
 │   ├── contribution/
 │   │   ├── coding-rule.md
 │   │   └── guidelines-en.md
@@ -171,11 +177,17 @@ timpani_rust/
 
 The `doc/` directory contains all project documentation:
 
-- **architecture/**: System architecture and LLD component documents
-  - `timpani_architecture.md`: Overall system design
-  - `grpc_architecture.md`: Communication layer design
-  - `LLD/timpani-o/`: 10 component LLD documents (AS-IS vs WILL-BE)
-  - `LLD/timpani-n/`: 10 component LLD documents (AS-IS vs WILL-BE)
+- **architecture/**: System architecture documentation
+  - **HLD/**: High-Level Design documents
+    - `timpani_system_design_document.md`: Overall system architecture, components, deployment
+    - `timpani_rust_grpc_architecture.md`: D-Bus → gRPC migration, communication flow, performance
+  - **LLD/**: Low-Level Design component documents
+    - `timpani-o/`: 10 component LLD documents (AS-IS vs WILL-BE)
+    - `timpani-n/`: 10 component LLD documents (AS-IS vs WILL-BE)
+
+- **features/**: Feature specifications and requirements
+  - `timpani_features.md`: Feature breakdown with mermaid diagrams, 3-level feature tables
+  - `requirements/timpani_requirements.md`: Functional and non-functional requirements (FR/NFR)
 
 - **docs/**: Implementation and developer guides
   - `api.md`: gRPC services and Rust APIs
@@ -194,9 +206,9 @@ The `doc/` directory contains all project documentation:
 
 | Component | Legacy | Rust | Status | Documentation |
 |-----------|--------|------|--------|---------------|
-| **timpani-o** | C++ | Rust | ✅ Complete | [LLD/timpani-o/](../architecture/LLD/timpani-o/) |
-| **timpani-n** | C | Rust | 🔄 Partial | [LLD/timpani-n/](../architecture/LLD/timpani-n/) |
-| **Communication** | D-Bus | gRPC | ✅ timpani-o, ⏸️ timpani-n | [grpc_architecture.md](../architecture/grpc_architecture.md) |
+| **timpani-o** | C++ | Rust | ✅ Complete | [HLD](../architecture/HLD/timpani_system_design_document.md), [LLD/timpani-o/](../architecture/LLD/timpani-o/) |
+| **timpani-n** | C | Rust | 🔄 Partial | [HLD](../architecture/HLD/timpani_system_design_document.md), [LLD/timpani-n/](../architecture/LLD/timpani-n/) |
+| **Communication** | D-Bus | gRPC | ✅ timpani-o, ⏸️ timpani-n | [gRPC Architecture](../architecture/HLD/timpani_rust_grpc_architecture.md) |
 
 ---
 
diff --git a/doc/features/requirements/timpani_requirements.md b/doc/features/requirements/timpani_requirements.md
new file mode 100644
index 0000000..e2887d9
--- /dev/null
+++ b/doc/features/requirements/timpani_requirements.md
@@ -0,0 +1,631 @@
+<!--
+* SPDX-FileCopyrightText: Copyright 2026 LG Electronics Inc.
+* SPDX-License-Identifier: MIT
+-->
+
+# timpani System Requirements Specification
+
+**Document Information:**
+- **Issuing Author:** LGSI-KarumuriHari(Eclipse timpani Team)
+- **Configuration ID:** timpani-req-spec
+- **Document Status:** Draft
+- **Last Updated:** 2026-05-14
+
+---
+
+## Revision History
+
+| Version | Date | Comment | Author | Approver |
+|---------|------|---------|--------|----------|
+| 0.0c | 2026-05-14 | Added gPTP time synchronization requirement (Milestone 3) | LGSI-KarumuriHari | - |
+| 0.0b | 2026-05-13 | Expanded functional and non-functional requirements | LGSI-KarumuriHari | - |
+| 0.0a | 2026-02-24 | Initial requirements specification | Eclipse timpani Team | - |
+
+---
+
+## Table of Contents
+
+1. [Introduction](#introduction)
+2. [Functional Requirements](#functional-requirements)
+3. [Non-Functional Requirements](#non-functional-requirements)
+4. [Requirements Traceability Matrix](#requirements-traceability-matrix)
+
+---
+
+## Introduction
+
+This document specifies the functional and non-functional requirements for the Eclipse timpani distributed real-time task orchestration framework. timpani consists of two primary components: timpani-o (global orchestrator) and timpani-n (node executor), designed to provide deterministic real-time task execution across distributed systems.
+
+### Scope
+
+This requirements specification covers:
+- Real-time task scheduling and execution
+- Distributed node coordination and communication
+- Fault detection and recovery mechanisms
+- System monitoring and observability
+- Configuration and deployment management
+
+---
+
+## Functional Requirements
+
+### FR-1: Real-Time Scheduling
+
+#### FR-1.1: Task Scheduling Algorithms
+**Requirement:** The system SHALL support multiple real-time scheduling algorithms.
+- **FR-1.1.1:** Support Rate Monotonic (RM) priority assignment
+- **FR-1.1.2:** Support Earliest Deadline First (EDF) scheduling
+- **FR-1.1.3:** Support SCHED_DEADLINE Linux scheduling policy
+- **FR-1.1.4:** Provide schedulability analysis using Liu & Layland bounds
+
+**Priority:** High
+**Component:** timpani-o (Global Scheduler)
+
+#### FR-1.2: Hyperperiod Calculation
+**Requirement:** The system SHALL calculate hyperperiod for periodic task sets.
+- **FR-1.2.1:** Compute Least Common Multiple (LCM) of all task periods
+- **FR-1.2.2:** Validate hyperperiod against maximum supported value
+- **FR-1.2.3:** Store hyperperiod information for schedule validation
+
+**Priority:** High
+**Component:** timpani-o (Hyperperiod Manager)
+
+#### FR-1.3: CPU Utilization Analysis
+**Requirement:** The system SHALL analyze CPU utilization for schedulability.
+- **FR-1.3.1:** Calculate per-task CPU utilization (WCET/Period)
+- **FR-1.3.2:** Compute total system utilization
+- **FR-1.3.3:** Verify utilization against schedulability bounds
+- **FR-1.3.4:** Reject schedules exceeding utilization limits
+
+**Priority:** High
+**Component:** timpani-o (Scheduler Utilities)
+
+---
+
+### FR-2: Task Management
+
+#### FR-2.1: Task Definition
+**Requirement:** The system SHALL support comprehensive task specification.
+- **FR-2.1.1:** Define task period (minimum 1ms, maximum 10s)
+- **FR-2.1.2:** Define task deadline (≤ period)
+- **FR-2.1.3:** Define worst-case execution time (WCET)
+- **FR-2.1.4:** Define task priority (1-99 for SCHED_DEADLINE)
+- **FR-2.1.5:** Define CPU affinity constraints
+
+**Priority:** High
+**Component:** timpani-o (Data Structures), timpani-n (Task Manager)
+
+#### FR-2.2: Task Lifecycle Management
+**Requirement:** The system SHALL manage complete task lifecycle.
+- **FR-2.2.1:** Initialize tasks with specified parameters
+- **FR-2.2.2:** Activate tasks at scheduled release times
+- **FR-2.2.3:** Track task execution state (ready, running, completed, missed)
+- **FR-2.2.4:** Terminate tasks on completion or system shutdown
+- **FR-2.2.5:** Handle task preemption and context switching
+
+**Priority:** High
+**Component:** timpani-n (Task Manager, RT Scheduler)
+
+#### FR-2.3: Task Isolation
+**Requirement:** The system SHALL provide task isolation mechanisms.
+- **FR-2.3.1:** Assign tasks to specific CPU cores via affinity masks
+- **FR-2.3.2:** Prevent interference between tasks on different cores
+- **FR-2.3.3:** Support mixed-criticality task sets
+
+**Priority:** Medium
+**Component:** timpani-n (RT Scheduler)
+
+---
+
+### FR-3: Communication
+
+#### FR-3.1: gRPC Communication
+**Requirement:** The system SHALL implement gRPC-based communication.
+- **FR-3.1.1:** Provide SchedInfoService for workload submission (timpani-o)
+- **FR-3.1.2:** Provide NodeService for schedule distribution (timpani-o)
+- **FR-3.1.3:** Implement gRPC client for schedule retrieval (timpani-n)
+- **FR-3.1.4:** Use Protocol Buffers for message serialization
+- **FR-3.1.5:** Support asynchronous RPC calls using Tokio runtime
+
+**Priority:** High
+**Component:** timpani-o (gRPC Server), timpani-n (gRPC Client)
+
+#### FR-3.2: Legacy D-Bus Support
+**Requirement:** The C implementation SHALL support D-Bus communication (replaced in Rust).
+- **FR-3.2.1:** Provide libtrpc interface for C-based timpani-n
+- **FR-3.2.2:** Support D-Bus method calls for schedule retrieval
+- **FR-3.2.3:** Maintain backward compatibility with C implementation
+
+**Priority:** Low (Legacy)
+**Component:** timpani-n (libtrpc Client)
+
+#### FR-3.3: Fault Reporting
+**Requirement:** The system SHALL report fault events to orchestrator.
+- **FR-3.3.1:** Detect deadline miss events
+- **FR-3.3.2:** Report deadline misses to Pullpiri via gRPC FaultService
+- **FR-3.3.3:** Include task ID, node ID, timestamp, and miss count
+- **FR-3.3.4:** Support batch reporting for multiple faults
+
+**Priority:** High
+**Component:** timpani-o (Fault Client)
+
+---
+
+### FR-4: Node Management
+
+#### FR-4.1: Node Configuration
+**Requirement:** The system SHALL manage node hardware specifications.
+- **FR-4.1.1:** Load node configurations from YAML files
+- **FR-4.1.2:** Specify CPU count, memory, and architecture per node
+- **FR-4.1.3:** Validate node configuration against hardware capabilities
+- **FR-4.1.4:** Support dynamic node addition (hot-plug)
+
+**Priority:** High
+**Component:** timpani-o (NodeConfigManager)
+
+#### FR-4.2: Schedule Distribution
+**Requirement:** The system SHALL distribute schedules to execution nodes.
+- **FR-4.2.1:** Send computed schedules to timpani-n nodes via gRPC
+- **FR-4.2.2:** Include task parameters, release times, and affinity
+- **FR-4.2.3:** Support incremental schedule updates
+- **FR-4.2.4:** Confirm schedule receipt and activation
+
+**Priority:** High
+**Component:** timpani-o (Node Service), timpani-n (Schedule Receiver)
+
+#### FR-4.3: Node Synchronization
+**Requirement:** The system SHALL synchronize execution across nodes.
+- **FR-4.3.1:** Coordinate simultaneous schedule activation
+- **FR-4.3.2:** Provide synchronization barriers for distributed tasks
+- **FR-4.3.3:** Handle clock skew between nodes (< 1ms tolerance)
+
+**Priority:** Medium
+**Component:** timpani-o (Node Service), timpani-n (Main Controller)
+
+---
+
+### FR-5: Monitoring and Observability
+
+#### FR-5.1: eBPF Monitoring
+**Requirement:** The system SHALL provide kernel-level monitoring via eBPF.
+- **FR-5.1.1:** Monitor scheduler events using tracepoints (schedstat.bpf.c)
+- **FR-5.1.2:** Monitor signal delivery timing (sigwait.bpf.c)
+- **FR-5.1.3:** Collect scheduling latency and context switch data
+- **FR-5.1.4:** Transfer monitoring data via BPF ring buffers
+
+**Priority:** Medium
+**Component:** timpani-n (BPF Monitoring)
+
+#### FR-5.2: Deadline Miss Detection
+**Requirement:** The system SHALL detect and report deadline violations.
+- **FR-5.2.1:** Monitor task completion times against deadlines
+- **FR-5.2.2:** Generate deadline miss events with timestamp and task ID
+- **FR-5.2.3:** Log deadline misses for post-mortem analysis
+- **FR-5.2.4:** Trigger fault recovery mechanisms on repeated misses
+
+**Priority:** High
+**Component:** timpani-n (Signal Handler, BPF Monitoring)
+
+#### FR-5.3: Performance Metrics
+**Requirement:** The system SHALL collect performance metrics.
+- **FR-5.3.1:** Measure end-to-end schedule activation latency
+- **FR-5.3.2:** Track CPU utilization per task and per core
+- **FR-5.3.3:** Measure communication latency (gRPC call duration)
+- **FR-5.3.4:** Export metrics in Prometheus format (future)
+
+**Priority:** Low
+**Component:** timpani-o, timpani-n (Monitoring Layer)
+
+---
+
+### FR-6: Configuration Management
+
+#### FR-6.1: Command-Line Interface
+**Requirement:** The system SHALL provide CLI configuration.
+- **FR-6.1.1:** Parse command-line arguments using Clap (Rust) or getopt (C)
+- **FR-6.1.2:** Support configuration file path specification
+- **FR-6.1.3:** Provide --help and --version options
+- **FR-6.1.4:** Validate all configuration parameters
+
+**Priority:** Medium
+**Component:** timpani-o, timpani-n (Configuration Manager)
+
+#### FR-6.2: YAML Configuration
+**Requirement:** The system SHALL support YAML-based configuration.
+- **FR-6.2.1:** Parse YAML files using serde_yaml (Rust)
+- **FR-6.2.2:** Define node hardware specifications in YAML
+- **FR-6.2.3:** Define default task parameters in YAML
+- **FR-6.2.4:** Support environment variable substitution
+
+**Priority:** Medium
+**Component:** timpani-o (NodeConfigManager)
+
+#### FR-6.3: Configuration Validation
+**Requirement:** The system SHALL validate all configuration inputs.
+- **FR-6.3.1:** Verify parameter ranges (period, deadline, WCET)
+- **FR-6.3.2:** Check for conflicting settings
+- **FR-6.3.3:** Provide meaningful error messages for invalid config
+- **FR-6.3.4:** Apply default values for optional parameters
+
+**Priority:** Medium
+**Component:** timpani-o, timpani-n (Configuration Manager)
+
+---
+
+### FR-7: Fault Tolerance
+
+#### FR-7.1: Error Handling
+**Requirement:** The system SHALL implement structured error handling.
+- **FR-7.1.1:** Use Result<T, E> types for error propagation (Rust)
+- **FR-7.1.2:** Define specific error types for each failure mode
+- **FR-7.1.3:** Log errors with context and stack traces
+- **FR-7.1.4:** Provide recovery hints in error messages
+
+**Priority:** High
+**Component:** timpani-o (Error Handling)
+
+#### FR-7.2: Graceful Degradation
+**Requirement:** The system SHALL degrade gracefully under failure.
+- **FR-7.2.1:** Continue operation with reduced node count
+- **FR-7.2.2:** Reschedule tasks from failed nodes
+- **FR-7.2.3:** Maintain critical task execution during partial failures
+- **FR-7.2.4:** Retry failed gRPC calls with exponential backoff
+
+**Priority:** Medium
+**Component:** timpani-o (Global Scheduler, Node Service)
+
+#### FR-7.3: Shutdown Handling
+**Requirement:** The system SHALL support graceful shutdown.
+- **FR-7.3.1:** Handle SIGTERM and SIGINT signals
+- **FR-7.3.2:** Complete in-flight tasks before shutdown
+- **FR-7.3.3:** Clean up system resources (timers, file descriptors)
+- **FR-7.3.4:** Notify connected nodes of shutdown
+
+**Priority:** Medium
+**Component:** timpani-o, timpani-n (Signal Handler, Main Controller)
+
+---
+
+### FR-8: Timer Management
+
+#### FR-8.1: POSIX Timers
+**Requirement:** The system SHALL use POSIX timers for periodic activation.
+- **FR-8.1.1:** Create timers using timer_create() with CLOCK_MONOTONIC
+- **FR-8.1.2:** Configure timer periods using timer_settime()
+- **FR-8.1.3:** Deliver timer signals (SIGALRM) for task activation
+- **FR-8.1.4:** Support timer resolution ≤ 1ms
+
+**Priority:** High
+**Component:** timpani-n (Timer Manager)
+
+#### FR-8.2: Timer Synchronization
+**Requirement:** The system SHALL synchronize timers across tasks.
+- **FR-8.2.1:** Align task release times to hyperperiod boundaries
+- **FR-8.2.2:** Minimize jitter in timer delivery (< 100μs)
+- **FR-8.2.3:** Handle timer overruns gracefully
+
+**Priority:** Medium
+**Component:** timpani-n (Timer Manager)
+
+---
+
+### FR-9: Time Synchronization (gPTP)
+
+#### FR-9.1: IEEE 802.1AS Protocol Support
+**Requirement:** The system SHALL support gPTP (generalized Precision Time Protocol) for distributed time synchronization.
+- **FR-9.1.1:** Implement IEEE 802.1AS-2020 time synchronization protocol
+- **FR-9.1.2:** Support both grandmaster and slave clock roles
+- **FR-9.1.3:** Synchronize system clocks across all timpani-n nodes
+- **FR-9.1.4:** Maintain time synchronization accuracy ≤ 1 microsecond
+- **FR-9.1.5:** Support PTP over Ethernet (Layer 2)
+
+**Priority:** High (Milestone 3)
+**Component:** timpani-n (Time Sync Manager), timpani-o (Clock Coordinator)
+
+#### FR-9.2: Clock Synchronization
+**Requirement:** The system SHALL maintain synchronized clocks across distributed nodes.
+- **FR-9.2.1:** Synchronize CLOCK_REALTIME across all nodes
+- **FR-9.2.2:** Compensate for network propagation delays
+- **FR-9.2.3:** Handle clock drift correction automatically
+- **FR-9.2.4:** Detect and report synchronization failures
+- **FR-9.2.5:** Support fallback to NTP when gPTP unavailable
+
+**Priority:** High (Milestone 3)
+**Component:** timpani-n (Time Sync Manager)
+
+#### FR-9.3: Synchronized Task Activation
+**Requirement:** The system SHALL coordinate task activation using synchronized time.
+- **FR-9.3.1:** Use gPTP-synchronized time for schedule activation
+- **FR-9.3.2:** Align task release times across nodes within 10 microseconds
+- **FR-9.3.3:** Validate time synchronization before schedule execution
+- **FR-9.3.4:** Reject schedules if synchronization quality insufficient
+
+**Priority:** High (Milestone 3)
+**Component:** timpani-n (RT Scheduler, Time Sync Manager)
+
+#### FR-9.4: Time Synchronization Monitoring
+**Requirement:** The system SHALL monitor time synchronization quality.
+- **FR-9.4.1:** Measure clock offset between nodes
+- **FR-9.4.2:** Track synchronization accuracy over time
+- **FR-9.4.3:** Report synchronization degradation events
+- **FR-9.4.4:** Provide time synchronization status via gRPC API
+
+**Priority:** Medium (Milestone 3)
+**Component:** timpani-o (Monitoring), timpani-n (Time Sync Manager)
+
+---
+
+## Non-Functional Requirements
+
+### NFR-1: Performance
+
+#### NFR-1.1: Latency
+**Requirement:** The system SHALL meet strict latency requirements.
+- **NFR-1.1.1:** Schedule computation latency < 100ms for 100-task workload
+- **NFR-1.1.2:** gRPC call latency < 10ms (median), < 50ms (p99)
+- **NFR-1.1.3:** Task activation jitter < 100μs
+- **NFR-1.1.4:** Deadline miss detection latency < 1ms
+
+**Measurement:** Benchmark testing, production monitoring
+**Priority:** High
+
+#### NFR-1.2: Throughput
+**Requirement:** The system SHALL support high workload throughput.
+- **NFR-1.2.1:** Handle ≥ 1000 tasks per hyperperiod
+- **NFR-1.2.2:** Support ≥ 100 concurrent gRPC connections
+- **NFR-1.2.3:** Process ≥ 10 schedule updates per second
+
+**Measurement:** Load testing
+**Priority:** Medium
+
+#### NFR-1.3: Resource Efficiency
+**Requirement:** The system SHALL minimize resource consumption.
+- **NFR-1.3.1:** timpani-o memory usage < 100MB for 1000-task workload
+- **NFR-1.3.2:** timpani-n memory usage < 50MB baseline
+- **NFR-1.3.3:** CPU overhead < 5% during steady-state execution
+- **NFR-1.3.4:** Binary size < 10MB (stripped, release build)
+
+**Measurement:** Resource profiling
+**Priority:** Medium
+
+---
+
+### NFR-2: Scalability
+
+#### NFR-2.1: Node Scalability
+**Requirement:** The system SHALL scale to multiple execution nodes.
+- **NFR-2.1.1:** Support ≥ 10 timpani-n nodes per timpani-o instance
+- **NFR-2.1.2:** Support ≥ 32 CPU cores per node
+- **NFR-2.1.3:** Maintain sub-100ms scheduling latency with 10 nodes
+- **NFR-2.1.4:** Support dynamic node addition/removal
+
+**Measurement:** Scalability testing
+**Priority:** High
+
+#### NFR-2.2: Task Scalability
+**Requirement:** The system SHALL scale to large task sets.
+- **NFR-2.2.1:** Support ≥ 1000 tasks per node
+- **NFR-2.2.2:** Support ≥ 10,000 tasks across distributed system
+- **NFR-2.2.3:** Maintain O(n log n) scheduling complexity
+- **NFR-2.2.4:** Support task periods from 1ms to 10s
+
+**Measurement:** Benchmark testing
+**Priority:** Medium
+
+---
+
+### NFR-3: Reliability
+
+#### NFR-3.1: Availability
+**Requirement:** The system SHALL provide high availability.
+- **NFR-3.1.1:** Target 99.9% uptime for timpani-o (< 9 hours downtime/year)
+- **NFR-3.1.2:** Recover from transient failures within 5 seconds
+- **NFR-3.1.3:** Continue operation with up to 30% node failures
+- **NFR-3.1.4:** Provide health check endpoints (gRPC health checking)
+
+**Measurement:** Availability monitoring
+**Priority:** High
+
+#### NFR-3.2: Fault Tolerance
+**Requirement:** The system SHALL tolerate common failure modes.
+- **NFR-3.2.1:** Handle network partition without data loss
+- **NFR-3.2.2:** Recover from crashed gRPC connections automatically
+- **NFR-3.2.3:** Detect and report node failures within 5 seconds
+- **NFR-3.2.4:** Maintain schedule consistency during failures
+
+**Measurement:** Chaos engineering, fault injection testing
+**Priority:** High
+
+#### NFR-3.3: Data Integrity
+**Requirement:** The system SHALL ensure data correctness.
+- **NFR-3.3.1:** Validate all Protocol Buffer messages
+- **NFR-3.3.2:** Verify schedule consistency across nodes
+- **NFR-3.3.3:** Detect and reject corrupted configurations
+- **NFR-3.3.4:** Use checksums for critical data structures
+
+**Measurement:** Data validation testing
+**Priority:** High
+
+---
+
+### NFR-4: Maintainability
+
+#### NFR-4.1: Code Quality
+**Requirement:** The system SHALL maintain high code quality.
+- **NFR-4.1.1:** Achieve ≥ 80% code coverage for unit tests
+- **NFR-4.1.2:** Pass all Clippy lints (Rust) with zero warnings
+- **NFR-4.1.3:** Follow Eclipse timpani coding standards
+- **NFR-4.1.4:** Document all public APIs with rustdoc/doxygen
+
+**Measurement:** Static analysis, test coverage reports
+**Priority:** Medium
+
+#### NFR-4.2: Logging and Debugging
+**Requirement:** The system SHALL provide comprehensive logging.
+- **NFR-4.2.1:** Use structured logging (tracing crate for Rust)
+- **NFR-4.2.2:** Support configurable log levels (ERROR, WARN, INFO, DEBUG, TRACE)
+- **NFR-4.2.3:** Include timestamps, component names, and context in logs
+- **NFR-4.2.4:** Rotate log files to prevent disk exhaustion
+
+**Measurement:** Log quality review
+**Priority:** Medium
+
+#### NFR-4.3: Modularity
+**Requirement:** The system SHALL maintain modular architecture.
+- **NFR-4.3.1:** Separate concerns into distinct layers (Interface, Core, Data, Storage)
+- **NFR-4.3.2:** Use dependency injection for component coupling
+- **NFR-4.3.3:** Minimize circular dependencies
+- **NFR-4.3.4:** Support component replacement without system redesign
+
+**Measurement:** Architecture review, dependency analysis
+**Priority:** Medium
+
+---
+
+### NFR-5: Portability
+
+#### NFR-5.1: Platform Support
+**Requirement:** The system SHALL support multiple platforms.
+- **NFR-5.1.1:** Support x86_64, aarch64, and armhf architectures
+- **NFR-5.1.2:** Support Ubuntu 20.04+, CentOS 8+, and Fedora 35+
+- **NFR-5.1.3:** Require Linux kernel ≥ 5.10 for eBPF support
+- **NFR-5.1.4:** Support RT_PREEMPT and PREEMPT_RT kernel patches
+
+**Measurement:** Cross-platform testing
+**Priority:** High
+
+#### NFR-5.2: Build System
+**Requirement:** The system SHALL support reproducible builds.
+- **NFR-5.2.1:** Use Cargo for Rust components (Cargo.toml, Cargo.lock)
+- **NFR-5.2.2:** Use CMake for C components with version ≥ 3.16
+- **NFR-5.2.3:** Provide Docker-based build environments
+- **NFR-5.2.4:** Support cross-compilation for target architectures
+
+**Measurement:** Build verification
+**Priority:** Medium
+
+---
+
+### NFR-6: Security
+
+#### NFR-6.1: Authentication
+**Requirement:** The system SHALL support secure authentication (future).
+- **NFR-6.1.1:** Support TLS for gRPC connections
+- **NFR-6.1.2:** Validate client certificates
+- **NFR-6.1.3:** Implement token-based authentication
+- **NFR-6.1.4:** Rotate credentials periodically
+
+**Measurement:** Security audit
+**Priority:** Low (Future Enhancement)
+
+#### NFR-6.2: Input Validation
+**Requirement:** The system SHALL validate all external inputs.
+- **NFR-6.2.1:** Sanitize all configuration file inputs
+- **NFR-6.2.2:** Validate Protocol Buffer message contents
+- **NFR-6.2.3:** Reject malformed gRPC requests
+- **NFR-6.2.4:** Limit input sizes to prevent DoS
+
+**Measurement:** Fuzz testing
+**Priority:** Medium
+
+---
+
+### NFR-7: Compliance
+
+#### NFR-7.1: Licensing
+**Requirement:** The system SHALL comply with open-source licensing.
+- **NFR-7.1.1:** Use MIT license for all Eclipse timpani code
+- **NFR-7.1.2:** Include SPDX headers in all source files
+- **NFR-7.1.3:** Document third-party dependencies and licenses
+- **NFR-7.1.4:** Use cargo-deny for license compliance checking
+
+**Measurement:** License audit
+**Priority:** High
+
+#### NFR-7.2: Documentation
+**Requirement:** The system SHALL provide comprehensive documentation.
+- **NFR-7.2.1:** Maintain architecture documentation
+- **NFR-7.2.2:** Provide LLD documents for all components
+- **NFR-7.2.3:** Include API reference documentation
+- **NFR-7.2.4:** Provide user guides and tutorials
+
+**Measurement:** Documentation review
+**Priority:** Medium
+
+---
+
+## Requirements Traceability Matrix
+
+### timpani-o Requirements Mapping
+
+| Requirement ID | Feature (Level 2) | Component (Level 3) | Verification Method |
+|----------------|-------------------|---------------------|---------------------|
+| FR-1.1 - FR-1.3 | Core Processing Layer | Global Scheduler, Scheduler Utils | Unit tests, benchmarks |
+| FR-1.2 | Core Processing Layer | Hyperperiod Manager | Unit tests |
+| FR-2.1 | Data Management Layer | Task Converter | Unit tests |
+| FR-3.1 | Interface Layer | gRPC Server | Integration tests |
+| FR-3.3 | Interface Layer | Fault Client | Integration tests |
+| FR-4.1 | Core Processing Layer | NodeConfigManager | Unit tests |
+| FR-4.2 | Interface Layer | gRPC Server (NodeService) | Integration tests |
+| FR-6.2 | Data Management Layer | Configuration Loader | Unit tests |
+| FR-7.1 | Core Processing Layer | Error Handling | Unit tests |
+| NFR-1.1 - NFR-1.3 | All layers | All components | Performance tests |
+| NFR-3.1 - NFR-3.3 | All layers | All components | Reliability tests |
+
+### timpani-n Requirements Mapping
+
+| Requirement ID | Feature (Level 2) | Component (Level 3) | Verification Method |
+|----------------|-------------------|---------------------|---------------------|
+| FR-2.1 - FR-2.3 | Execution Layer | Task Manager, RT Scheduler | Unit tests, integration tests |
+| FR-3.1 | Communication Layer | gRPC Client | Integration tests |
+| FR-3.2 | Communication Layer | libtrpc Client | Integration tests (C) |
+| FR-4.2 | Communication Layer | Schedule Receiver | Integration tests |
+| FR-5.1 | BPF Monitoring | Scheduler Monitoring, Signal Monitoring | System tests |
+| FR-5.2 | Execution Layer | Signal Handler | System tests |
+| FR-6.1 | Core Layer | Configuration Manager | Unit tests |
+| FR-7.3 | Core Layer | Main Controller, Signal Handler | System tests |
+| FR-8.1 - FR-8.2 | Execution Layer | Timer Manager | Unit tests, timing tests |
+| FR-9.1 - FR-9.4 | Time Synchronization | Time Sync Manager, Clock Coordinator | System tests, timing tests |
+| NFR-1.1 | All layers | All components | Latency benchmarks |
+| NFR-5.1 | All layers | All components | Cross-platform tests |
+
+---
+
+## Verification and Validation
+
+### Test Coverage Requirements
+
+- **Unit Tests:** ≥ 80% code coverage for all Rust modules
+- **Integration Tests:** Cover all gRPC service interfaces
+- **System Tests:** Validate end-to-end workflows
+- **Performance Tests:** Verify NFR-1 (latency, throughput, resource usage)
+- **Reliability Tests:** Verify NFR-3 (fault injection, chaos testing)
+- **Portability Tests:** Verify NFR-5 (multi-platform builds)
+
+### Acceptance Criteria
+
+A release is considered acceptable when:
+1. All priority=High functional requirements are implemented and verified
+2. All priority=High non-functional requirements meet specified targets
+3. Test coverage ≥ 80% for Rust code
+4. Zero critical or high-severity bugs remain open
+5. All documentation is up-to-date
+
+---
+
+## Related Documentation
+
+- [timpani Feature Specification](../timpani_features.md)
+- [timpani Architecture](../../architecture/timpani_architecture.md)
+- [timpani-o LLD Documents](../../architecture/LLD/timpani-o/)
+- [timpani-n LLD Documents](../../architecture/LLD/timpani-n/)
+
+---
+
+## References
+
+1. Eclipse timpani Project Documentation
+2. IEEE 830-1998: Software Requirements Specification
+3. Real-Time Systems Design and Analysis (Klein et al.)
+4. Liu & Layland: Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment
+5. gRPC Best Practices and Performance Guidelines
diff --git a/doc/features/timpani_features.md b/doc/features/timpani_features.md
new file mode 100644
index 0000000..ad2706e
--- /dev/null
+++ b/doc/features/timpani_features.md
@@ -0,0 +1,229 @@
+<!--
+* SPDX-FileCopyrightText: Copyright 2026 LG Electronics Inc.
+* SPDX-License-Identifier: MIT
+-->
+
+# timpani Feature Specification
+
+**Document Information:**
+- **Issuing Author:** LGSI-KarumuriHari(Eclipse timpani Team)
+- **Configuration ID:** timpani-feature-spec
+- **Document Status:** Draft
+- **Last Updated:** 2026-05-14
+
+---
+
+## Revision History
+
+| Version | Date | Comment | Author | Approver |
+|---------|------|---------|--------|----------|
+| 0.0c | 2026-05-14 | Removed implementation status section  | LGSI-KarumuriHari | - |
+| 0.0b | 2026-05-13 | Added system block diagram and feature breakdown table | LGSI-KarumuriHari | - |
+| 0.0a | 2026-02-24 | Initial feature specification | Eclipse timpani Team | - |
+
+---
+
+## Table of Contents
+
+1. [System Overview](#system-overview)
+2. [Feature Breakdown Table](#feature-breakdown-table)
+3. [Feature Descriptions](#feature-descriptions)
+
+---
+
+## System Overview
+
+Eclipse timpani is a distributed real-time task orchestration framework consisting of three main components:
+
+- **timpani-o (Orchestrator):** Global scheduler that manages workloads across multiple nodes
+- **timpani-n (Node Executor):** Local executor that runs time-triggered tasks with real-time guarantees
+- **sample-apps:** Sample applications and workload generators for testing and demonstration
+
+**Note:** For detailed system block diagrams and component architecture, please refer to the [High-Level Design (HLD) documents](../architecture/HLD/).
+
+---
+
+## Feature Breakdown Table
+
+The following table shows the 3-level feature breakdown for Eclipse timpani system components.
+
+### Table 1: timpani System Features
+
+| Level 1 | Level 2 | Level 3 | Descriptions |
+|---------|---------|---------|--------------|
+| **timpani-o**<br/>(Global Orchestrator) | **Interface Layer** | D-Bus Server (replaced) | Legacy D-Bus interface replaced by gRPC for node communication |
+| | | gRPC Server | Modern gRPC service endpoint on port 50054 for Pullpiri and node communication |
+| | | Fault Client | gRPC client for reporting deadline misses and fault events to Pullpiri orchestrator |
+| | **Core Processing Layer** | SchedInfoService impl | Implementation of gRPC SchedInfo service for receiving and processing workload schedules |
+| | | Hyperperiod Manager | Calculates LCM of task periods for hyperperiod determination and schedule validation |
+| | | Global Scheduler | Allocates tasks to nodes and CPUs using real-time scheduling algorithms (Rate Monotonic, EDF) |
+| | | NodeConfigManager | Loads and manages node hardware specifications from YAML configuration files |
+| | **Data Management Layer** | Task Converter | Converts between Protocol Buffer task representations and internal scheduling data structures |
+| | | SchedInfo Map | Manages mapping and storage of scheduling information for active workload sets |
+| | | Scheduler Utils | Provides feasibility checks, Liu & Layland bounds, and CPU utilization calculations |
+| | **Storage Layer** | Schedule State | Maintains current scheduling state and task allocations across nodes |
+| | | HyperPeriod Info | Stores calculated hyperperiod information for periodic task sets |
+| | | Node Config Files | YAML configuration files containing node hardware specifications and capabilities |
+| **timpani-n**<br/>(Node Executor) | **BPF Monitoring** | Scheduler Monitoring | eBPF program (schedstat.bpf.c) tracks scheduler events via tracepoints |
+| | | Signal Monitoring | eBPF program (sigwait.bpf.c) monitors signal delivery and deadlines |
+| | | BPF Ring Buffer | Kernel-to-userspace data transfer for monitoring statistics |
+| | **Core Layer** | Main Controller | Program entry point, coordinates initialization and main execution loop |
+| | | Configuration Manager | CLI parsing with Clap, configuration validation, defaults management |
+| | | Context Structure | Global runtime state management (internal.h) |
+| | **Execution Layer** | Task Manager | Task list management, activation scheduling, state tracking |
+| | | RT Scheduler | CPU affinity assignment, RT priority configuration, sched_setattr() syscalls |
+| | | Timer Manager | POSIX timer management, periodic activation timing |
+| | | Signal Handler | SIGALRM handling, task signal delivery, shutdown signal processing |
+| | **Communication Layer** | libtrpc Client | Legacy D-Bus communication client for timpani-o integration |
+| | | gRPC Client (Rust) | Modern gRPC client implementation for schedule retrieval and sync |
+| | | Schedule Receiver | Receives workload schedules from timpani-o orchestrator |
+| | **System Interface** | Linux Scheduler | Integration with SCHED_DEADLINE real-time scheduling policy |
+| | | CPU Affinity Control | CPU core assignment and affinity management for tasks |
+| | | POSIX Timers | Timer_create, timer_settime for periodic task activation |
+| **sample-apps**<br/>(Workload Generator) | **Workload Library** | libttsched | Time-triggered scheduling library for sample applications |
+| | | Task Primitives | Task initialization, execution, and termination functions |
+| | **Sample Applications** | Periodic Tasks | Configurable periodic workload generators with CPU burn loops |
+| | | Aperiodic Tasks | Event-driven workload generators for mixed-criticality testing |
+| | | Multi-threaded Apps | Parallel execution workloads for multi-core testing |
+| | **Testing Tools** | WCET Analyzer | Worst-Case Execution Time measurement and analysis tools |
+| | | Workload Profiler | CPU utilization and response time profiling utilities |
+| | | Deadline Monitor | Deadline miss detection and reporting for validation |
+| | **Build System** | CMake Configuration | Cross-compilation support for x86_64, aarch64, armhf |
+| | | Docker Support | Containerized build environments (Ubuntu, CentOS) |
+| | | Integration Scripts | Automated build and test execution scripts |
+
+---
+
+## Feature Descriptions
+
+### timpani-o (Global Orchestrator)
+
+#### Interface Layer
+The interface layer provides external communication endpoints for the global orchestrator. The legacy D-Bus protocol has been replaced by modern gRPC for improved performance and type safety.
+
+**Key Features:**
+- **D-Bus Server (replaced)**: Legacy interface that has been replaced by gRPC in the Rust implementation
+- **gRPC Server**: Modern high-performance RPC server on port 50054 using Tonic framework
+- **Fault Client**: Reports deadline misses and fault events to Pullpiri orchestrator
+
+#### Core Processing Layer
+The core processing layer implements the main scheduling logic and workload management functionality.
+
+**Key Features:**
+- **SchedInfoService impl**: Implements gRPC service for receiving workload schedules from Pullpiri
+- **Hyperperiod Manager**: LCM calculation for periodic task sets and schedule validation
+- **Global Scheduler**: Rate Monotonic (RM) and Earliest Deadline First (EDF) task allocation algorithms
+- **NodeConfigManager**: YAML-based node specification loading and hardware capability management
+
+#### Data Management Layer
+Handles data transformation, mapping, and utility functions for scheduling operations.
+
+**Key Features:**
+- **Task Converter**: Protocol Buffer to internal data structure conversion and validation
+- **SchedInfo Map**: Efficient mapping and lookup of scheduling information for active workloads
+- **Scheduler Utils**: Liu & Layland schedulability bounds, feasibility analysis, and utilization calculations
+
+#### Storage Layer
+Manages persistent and runtime state storage for scheduling information.
+
+**Key Features:**
+- **Schedule State**: Current task allocations, node assignments, and execution state
+- **HyperPeriod Info**: Calculated LCM values and hyperperiod metadata for task sets
+- **Node Config Files**: YAML configuration files with node hardware specifications (CPU, memory, architecture)
+
+### timpani-n (Node Executor)
+
+#### BPF Monitoring
+Provides kernel-level monitoring of scheduler events and signal delivery using eBPF technology.
+
+**Key Features:**
+- **Scheduler Monitoring**: Tracks scheduling latency and context switches
+- **Signal Monitoring**: Monitors signal delivery timing for deadline detection
+- **BPF Ring Buffer**: High-performance kernel-to-userspace data transfer
+
+#### Core Layer
+Central coordination and configuration management for the node executor.
+
+**Key Features:**
+- **Main Controller**: Initialization, event loop, shutdown coordination
+- **Configuration Manager**: Command-line parsing, validation, defaults
+- **Context Structure**: Global state, task lists, runtime information
+
+#### Execution Layer
+Manages task lifecycle, real-time scheduling, and timer-based activation.
+
+**Key Features:**
+- **Task Manager**: Task creation, activation, completion tracking
+- **RT Scheduler**: SCHED_DEADLINE policy, CPU affinity, priority assignment
+- **Timer Manager**: POSIX timer management for periodic activation
+- **Signal Handler**: SIGALRM processing, graceful shutdown
+
+#### Communication Layer
+Handles communication with timpani-o orchestrator.
+
+**Key Features:**
+- **libtrpc Client** (Legacy): D-Bus-based RPC client
+- **gRPC Client** (Rust): Modern gRPC implementation
+- **Schedule Receiver**: Workload schedule retrieval and parsing
+
+#### System Interface
+Low-level integration with Linux kernel scheduling and timing facilities.
+
+**Key Features:**
+- **Linux Scheduler**: SCHED_DEADLINE integration for real-time guarantees
+- **CPU Affinity**: Core assignment for task isolation
+- **POSIX Timers**: Timer_create/timer_settime for periodic activation
+
+### sample-apps (Workload Generator)
+
+#### Workload Library
+Provides reusable components for creating test workloads.
+
+**Key Features:**
+- **libttsched**: Time-triggered scheduling primitives
+- **Task API**: Initialization, execution, cleanup interfaces
+- **Configuration**: Period, deadline, WCET specification
+
+#### Sample Applications
+Pre-built workload generators for testing and demonstration.
+
+**Key Features:**
+- **Periodic Tasks**: Fixed-period CPU-bound workloads
+- **Aperiodic Tasks**: Event-driven sporadic workloads
+- **Multi-threaded**: Parallel execution patterns
+
+#### Testing Tools
+Analysis and validation utilities for real-time performance.
+
+**Key Features:**
+- **WCET Analyzer**: Execution time measurement and statistics
+- **Workload Profiler**: CPU usage and timing analysis
+- **Deadline Monitor**: Deadline miss detection and logging
+
+#### Build System
+Cross-platform build and deployment infrastructure.
+
+**Key Features:**
+- **CMake**: Multi-architecture build configuration
+- **Docker**: Reproducible build environments
+- **CI/CD Integration**: Automated testing and validation
+
+---
+
+## Related Documentation
+
+- [timpani Architecture](../architecture/timpani_architecture.md)
+- [timpani-o LLD Documents](../architecture/LLD/timpani-o/)
+- [timpani-n LLD Documents](../architecture/LLD/timpani-n/)
+- [timpani Requirements](requirements/timpani_requirements.md)
+- [API Documentation](../docs/api.md)
+
+---
+
+## References
+
+1. Eclipse timpani Project Documentation
+2. Real-Time Systems Design Patterns
+3. Liu & Layland Schedulability Analysis
+4. eBPF Programming Guide
+5. gRPC Protocol Documentation