# WIA-COMM-014 PHASE 1 — Data Format Specification **Standard:** WIA-COMM-014 **Phase:** 1 — Data Format **Version:** 1.0 **Status:** Stable **Source:** synthesized from the original `PHASE-1-DATA-FORMAT.md` (quarter 1 of 4) --- # WIA-COMM-014: CDN Specification v1.0 > **Standard ID:** WIA-COMM-014 > **Version:** 1.0.0 > **Published:** 2025-12-26 > **Status:** Active > **Authors:** WIA Communication Research Group --- ## Table of Contents 1. [Introduction](#1-introduction) 2. [CDN Architecture](#2-cdn-architecture) 3. [Edge Caching Strategies](#3-edge-caching-strategies) 4. [Origin Shielding](#4-origin-shielding) 5. [Cache Invalidation](#5-cache-invalidation) 6. [HTTP/2 and HTTP/3](#6-http2-and-http3) 7. [TLS/SSL Termination](#7-tlsssl-termination) 8. [DDoS Protection](#8-ddos-protection) 9. [Load Balancing](#9-load-balancing) 10. [Video Streaming Optimization](#10-video-streaming-optimization) 11. [Dynamic Content Acceleration](#11-dynamic-content-acceleration) 12. [Multi-CDN Strategies](#12-multi-cdn-strategies) 13. [Analytics and Monitoring](#13-analytics-and-monitoring) 14. [Major CDN Providers](#14-major-cdn-providers) 15. [Implementation Guidelines](#15-implementation-guidelines) 16. [References](#16-references) --- ## 1. Introduction ### 1.1 Purpose This specification defines the Content Delivery Network (CDN) standard, covering edge caching, content distribution, security, and performance optimization for global content delivery. ### 1.2 Scope The standard covers: - Edge network architecture and caching strategies - Origin protection and shielding mechanisms - Modern protocol support (HTTP/2, HTTP/3/QUIC) - Security features (DDoS, WAF, TLS) - Performance optimization techniques - Multi-CDN orchestration ### 1.3 Philosophy **弘익人間 (Benefit All Humanity)** - CDNs democratize access to fast, secure content delivery, enabling equal digital experiences worldwide regardless of geographic location. ### 1.4 Terminology - **CDN**: Content Delivery Network - **PoP**: Point of Presence - **Edge Node**: Server at edge location - **Origin**: Source server hosting original content - **TTL**: Time To Live (cache duration) - **Purge**: Cache invalidation/clearing - **Anycast**: Network addressing routing to nearest node - **TTFB**: Time To First Byte - **Cache Hit Ratio**: Percentage of requests served from cache --- ## 2. CDN Architecture ### 2.1 Network Topology ``` Global CDN Architecture: ┌─────────────────────────────────────────────────────┐ │ Global DNS / Anycast │ │ (Route to nearest edge location) │ └─────────────────┬───────────────────────────────────┘ │ ┌───────────┼───────────┐ │ │ │ ┌─────▼─────┐ ┌──▼──────┐ ┌──▼──────┐ │ NA Region │ │ EU Region│ │ APAC │ │ 50 PoPs │ │ 60 PoPs │ │ 70 PoPs │ └─────┬─────┘ └──┬──────┘ └──┬──────┘ │ │ │ ┌─────▼──────────▼────────────▼─────┐ │ Origin Shield │ │ (Intermediate Cache) │ └────────────────┬───────────────────┘ │ ┌───────▼────────┐ │ Origin Server │ │ (Source Data) │ └────────────────┘ ``` ### 2.2 Edge Node Components **Hardware:** - 10-100 Gbps network interfaces - 256 GB - 1 TB RAM for caching - NVMe SSDs for hot content - HDDs for cold content **Software:** - Nginx, Varnish, or custom proxy - Cache management system - Real-time analytics - Security filtering (WAF, DDoS) ### 2.3 Anycast Routing **BGP Anycast Implementation:** ``` 1. All edge locations announce same IP prefix 2. BGP routing selects nearest path 3. User request routed to closest PoP 4. Automatic failover if PoP unavailable ``` **Benefits:** - Reduced latency (geographic proximity) - DDoS mitigation (traffic distribution) - Automatic load balancing - High availability (no single point of failure) --- ## 3. Edge Caching Strategies ### 3.1 Cache Classification **Static Content:** ``` Assets: CSS, JS, Images, Fonts, Videos TTL: 1 day - 1 year Cache-Control: public, max-age=31536000, immutable Versioning: Use URL fingerprinting (/v1.2.3/app.js) ``` **Dynamic Content:** ``` Assets: HTML, API responses TTL: 60 seconds - 5 minutes Cache-Control: public, max-age=60, s-maxage=300 Vary: Accept-Encoding, Accept-Language, Cookie ``` **Personalized Content:** ``` Assets: User-specific data TTL: 0 (no-cache) or micro-caching (1-5s) Cache-Control: private, no-store Vary: Cookie, Authorization ``` ### 3.2 Cache Headers **Standard HTTP Cache Headers:** ```http Cache-Control: public, max-age=3600, s-maxage=7200, stale-while-revalidate=86400 Expires: Thu, 01 Jan 2026 00:00:00 GMT ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4" Last-Modified: Wed, 21 Oct 2025 07:28:00 GMT Vary: Accept-Encoding, Accept-Language ``` **CDN-Specific Headers:** ```http CDN-Cache-Control: max-age=7200 Surrogate-Control: max-age=3600 Cloudflare-CDN-Cache-Control: max-age=14400 ``` ### 3.3 Cache Key Design **Base Cache Key:** ``` scheme://host/path?query ``` **Custom Cache Key Components:** ``` - URL path and query string - Accept-Encoding (gzip, br, deflate) - Accept-Language (en, es, fr) - Device type (mobile, desktop, tablet) - Geographic location (country, region) - Custom headers ``` **Example:** ``` cache-key = sha256( url + accept-encoding + accept-language + device-type ) ``` ### 3.4 Stale Content Handling **Stale-While-Revalidate:** ```http Cache-Control: max-age=600, stale-while-revalidate=86400 Behavior: - Serve stale content (up to 24h old) - Asynchronously fetch fresh content - User gets instant response - Next user gets fresh content ``` **Stale-If-Error:** ```http Cache-Control: max-age=600, stale-if-error=86400 Behavior: - If origin returns error (500, 502, 503) - Serve stale cached content (up to 24h) - Prevents showing errors to users ``` --- ## 4. Origin Shielding ### 4.1 Architecture ``` ┌─── Edge PoP 1 ├─── Edge PoP 2 User Requests ────┼─── Edge PoP 3 ──► Origin Shield ──► Origin Server ├─── Edge PoP 4 └─── Edge PoP 5 Without Shield: 5 requests to origin With Shield: 1 request to origin (from shield) ``` ### 4.2 Benefits **Origin Load Reduction:** - 90-95% reduction in origin requests - Prevents origin overload during traffic spikes - Reduces bandwidth costs **Improved Cache Hit Ratio:** - Edge PoPs share cache via shield - Shield acts as mega-cache - Higher probability of cache hit **Enhanced Security:** - Origin IP hidden from public - Shield provides additional firewall - Reduced attack surface ### 4.3 Configuration **Shield Location Selection:** ``` Criteria: 1. Geographic proximity to origin 2. Network latency (<10ms to origin) 3. Bandwidth capacity (10+ Gbps) 4. Redundancy (multiple shield locations) Example: Origin: us-east-1 (Virginia) Primary Shield: us-east-1 (same region) Backup Shield: us-west-1 (California) ``` **Shield Cache Policy:** ```json { "originShield": { "enabled": true, "location": "us-east-1", "ttl": 3600, "gracePeriod": 300, "maxStale": 86400 } } ``` --- ## Annex E — Implementation Notes for PHASE-1-DATA-FORMAT The following implementation notes document field experience from pilot deployments and are non-normative. They are republished here so that early adopters can read them in context with the rest of PHASE-1-DATA-FORMAT. - **Operational scope** — implementations SHOULD declare their operational scope (single-tenant, multi-tenant, federated) in the OpenAPI document so that downstream auditors can score the deployment against the correct conformance tier in Annex A. - **Schema evolution** — additive changes (new optional fields, new error codes) are non-breaking; renaming or removing fields, even in error payloads, MUST trigger a minor version bump. - **Audit retention** — a 7-year retention window is sufficient to satisfy ISO/IEC 17065:2012 audit expectations in most jurisdictions; some regulators require longer retention, in which case the deployment policy MUST extend the retention window rather than relying on this PHASE's defaults. - **Time synchronization** — sub-second deadlines depend on synchronized clocks. NTPv4 with stratum-2 servers is sufficient for most deadlines expressed in this PHASE; PTP is recommended for sites that require deterministic interlocks. - **Error budget reporting** — implementations SHOULD publish a monthly error-budget summary (latency p95, error rate, violation hours) in the format defined by the WIA reporting profile to facilitate cross-vendor comparison without exposing tenant-specific data. These notes are not requirements; they are a reference for field teams mapping their existing operations onto WIA conformance. ## Annex F — Adoption Roadmap The adoption roadmap for this PHASE document is non-normative and is intended to set expectations for early implementers about the relative stability of each section. - **Stable** (sections marked normative with `MUST` / `MUST NOT`) — semantic versioning applies; breaking changes require a major version bump and at minimum 90 days of overlap with the prior major version on all WIA-published reference implementations. - **Provisional** (sections in this Annex and Annex D) — items are tracked openly and may be promoted to normative status without a major version bump if community feedback supports promotion. - **Reference** (test vectors, simulator behaviour, the reference TypeScript SDK) — versioned independently of this document so that mistakes in reference material can be corrected without amending the published PHASE document. Implementers SHOULD subscribe to the WIA Standards GitHub release notifications to track promotions between these tiers. Comments on the roadmap are accepted via the GitHub issues tracker on the WIA-Official organization. The roadmap is reviewed at every minor version of this PHASE document, and the review outcomes are recorded in the version-history table at the start of the document. ## Annex G — Test Vectors and Conformance Evidence This annex describes how implementations capture and publish conformance evidence for PHASE-1-DATA-FORMAT. The procedure is non-normative; it standardizes the shape of evidence so that auditors and downstream integrators can compare implementations without re-running the full test matrix. - **Test vectors** — every normative requirement in this PHASE has at least one positive vector and one negative vector under `tests/phase-vectors/phase-1-data-format/`. Implementations claiming conformance MUST run all vectors in CI and publish the resulting pass/fail matrix in their compliance package. - **Evidence package** — the compliance package is a tarball containing the SBOM (CycloneDX 1.5 or SPDX 2.3), the OpenAPI document, the test vector matrix, and a signed manifest. Signatures use Sigstore (DSSE envelope, Rekor transparency log entry) so that downstream consumers can verify provenance without trusting a private CA. - **Quarterly recheck** — implementations re-publish the evidence package every quarter even if no source change occurred, so that consumers can detect environmental drift (compiler updates, dependency updates, OS updates) without polling vendor changelogs. - **Cross-vendor crosswalk** — the WIA Standards working group maintains a crosswalk that maps each vector to the equivalent assertion in adjacent industry programs (where one exists), so an implementer that already certifies under one program can show conformance to PHASE-1-DATA-FORMAT with reduced incremental effort. - **Negative-result reporting** — vendors MUST report negative results with the same fidelity as positive ones. A test that is skipped without recorded justification is treated by auditors as a failure. These conventions are intended to make conformance evidence portable and machine-readable so that adoption of PHASE-1-DATA-FORMAT does not require bespoke auditor tooling. ## Annex H — Versioning and Deprecation Policy This annex codifies the versioning and deprecation policy for PHASE-1-DATA-FORMAT. It is non-normative; the rules below describe the policy that the WIA Standards working group commits to when amending this PHASE document. - **Semantic versioning** — major / minor / patch components follow Semantic Versioning 2.0.0 (https://semver.org/spec/v2.0.0.html). Major bump indicates a backwards-incompatible change to a normative requirement; minor bump indicates new normative requirements that do not break existing implementations; patch bump indicates editorial changes only (clarifications, typo fixes, formatting). - **Deprecation window** — when a normative requirement is removed or altered in a backwards-incompatible way, the prior major version is maintained in parallel for at least 180 days. During the parallel window, both major versions are marked Stable in the WIA Standards registry and either may be cited as "WIA-conformant". - **Sunset notification** — deprecated major versions enter a 12-month sunset window during which the WIA registry marks the version as Deprecated. The deprecation entry includes a migration note pointing to the replacement requirement(s) and an explanation of why the change was made. - **Editorial errata** — patch-level errata are issued without a deprecation window because they do not change normative behaviour. Errata are tracked in a public errata register and each entry is signed by the WIA Standards working group chair. - **Implementation changelog mapping** — implementations SHOULD publish a changelog mapping each PHASE version they support to the specific build, container digest, or SDK version that satisfies the version. This allows downstream auditors to verify version conformance without re-running the entire test matrix on every release. The policy is reviewed at the same cadence as the PHASE document and any changes to the policy itself are tracked in the version-history table at the start of the document. ## Annex I — Interoperability Profiles This annex describes how implementations declare interoperability profiles for PHASE-1-DATA-FORMAT. The profile mechanism is non-normative and exists so that deployments of varying scope (single tenant, regional cluster, federated network) can advertise the subset of normative requirements they satisfy without misrepresenting partial conformance as full conformance. - **Profile manifest** — every implementation publishes a profile manifest in JSON. The manifest enumerates the normative requirement IDs from this PHASE that are satisfied (`status: "supported"`), partially satisfied (`status: "partial"`, with a reason field), or excluded (`status: "excluded"`, with a justification). The manifest is signed using the same Sigstore key used for the SBOM in Annex G. - **Federation profile** — federated deployments publish an aggregated manifest summarizing the union and intersection of member-implementation profiles. The aggregated manifest is consumed by directory services so that callers can route a request to the least common denominator profile required for an interaction. - **Backwards-profile compatibility** — when a deployment migrates from one profile to a wider profile, the prior profile manifest remains valid and signed for the deprecation window defined in Annex H. This preserves audit traceability for auditors evaluating long-term interoperability. - **Profile registry** — the WIA Standards working group maintains a public registry of named profiles. Common deployment shapes (e.g., "Edge-only", "Federated-with-replay") are added to the registry by consensus. Registry entries are immutable; new shapes are added under new names rather than amending existing entries. - **Profile versioning** — profile names are versioned with the same Semantic Versioning rules described in Annex H. A deployment that advertises `WIA-P1-DATA-FORMAT-Edge-only/2` is asserting conformance with the second major version of the named profile, not the second deployment of an unversioned profile. The profile mechanism is intentionally lightweight; it is meant to make real deployment shapes visible without forcing every deployment to satisfy every normative requirement. ## Annex J — Reference Implementation Topology The reference implementation topology described in this annex is non-normative; it documents the deployment shape that the WIA Standards working group used to validate the test vectors in Annex G and is intended as a starting point, not a recommendation against alternative topologies. - **Single-tenant edge** — one runtime per organization, no shared state. Used for early-pilot deployments where conformance evidence is published manually. Sufficient for PHASE-1-DATA-FORMAT validation when the organization signs the manifest itself. - **Multi-tenant gateway** — one shared runtime serves multiple tenants via header-based isolation. Typically backed by a rate-limited gateway (Envoy or NGINX) and a shared OAuth 2.1 identity provider. The manifest is per-tenant; the runtime publishes a federation manifest that aggregates tenant manifests. - **Federated mesh** — multiple runtimes peer to one another and publish their manifests to a directory service. Each peer signs its own manifest; the directory service signs the aggregated index. This is the topology used by cross-organization deployments that need to compose conformance. - **Air-gapped batch** — no network connection between the runtime and the directory service. The runtime emits a signed evidence package on each batch and the operator transports the package via out-of-band channels. This is the topology used by regulators that prohibit live connectivity from sensitive environments. Implementations declare their topology in the manifest (see Annex I). A topology change MUST be reflected in a new manifest signature; the prior topology's manifest remains valid for the deprecation window described in Annex H to preserve audit traceability.