ITU-T X.805 - Security Architecture for End-to-End Communications Dim7-Availability-Network-Resources-Information-Authorized-Access-No-Service-Denial: ITU-T X.805 Security Dimension 7 - Availability + Network Resources + Information Accessible to Authorized Users + Denial-of-Service Prevention + Resilience + Redundancy + Disaster Recovery + Business Continuity + DDoS Mitigation

Security Dimension 7 Availability per X.805 Clause 6.7: Availability ensures that there is no denial of authorized access to network elements + stored information + information flows + services and applications due to events impacting the network. Availability protects against any factor that may interrupt or disrupt the legitimate use of network resources including human-caused threats + natural disasters + system failures + and accidental events. (1) Availability Categories: (a) Service Availability (uptime as percentage); (b) Network Element Availability; (c) Information Availability; (d) Workload Availability (recovery time objective RTO + recovery point objective RPO); (e) Connectivity Availability. (2) Availability Threats: (a) Denial of Service (DoS); (b) Distributed DoS (DDoS) - Volumetric + Protocol + Application Layer; (c) Hardware failures; (d) Software bugs + crashes; (e) Natural disasters (flood + fire + earthquake + hurricane); (f) Power outages; (g) Network outages; (h) Supply chain disruptions; (i) Cyber-attacks (ransomware + wiper malware); (j) Configuration errors + Human errors; (k) Capacity exhaustion; (l) Cooling failures; (m) Telecommunications failures. (3) Availability Mechanisms: (a) Redundancy (active-active + active-passive + N+1 + 2N + 2N+1); (b) High Availability (HA) clusters (Pacemaker + Keepalived + AWS Auto Scaling + Kubernetes); (c) Load Balancing (Layer 4 + Layer 7 + GSLB Global Server Load Balancing); (d) Failover (Hot + Warm + Cold standby); (e) Geographic distribution (Multi-Region + Multi-AZ + CDN); (f) Anycast + IP failover; (g) BGP multi-homing + multipath; (h) Auto-scaling (horizontal + vertical); (i) Capacity planning + traffic engineering; (j) Network resilience (SDN + MPLS-TE + FRR Fast Reroute); (k) Container orchestration (Kubernetes + Docker Swarm) self-healing. (4) Disaster Recovery (DR) and Business Continuity (BC): (a) Business Impact Analysis (BIA); (b) DR Plan (DRP) per ISO 22301 BCMS + ISO 27031 + NIST SP 800-34; (c) RTO Recovery Time Objective + RPO Recovery Point Objective + MTPD Maximum Tolerable Period of Disruption; (d) DR Site (Hot/Warm/Cold); (e) Backup + Restore (3-2-1 rule + immutable + air-gapped); (f) Disaster Recovery as a Service (DRaaS); (g) Tabletop exercises + chaos engineering; (h) Crisis Management + Emergency Response. (5) DDoS Mitigation: (a) On-prem DDoS appliances + Arbor Networks + A10 + Radware; (b) Cloud DDoS protection (AWS Shield Advanced + Azure DDoS Protection + Google Cloud Armor + Cloudflare + Akamai); (c) Anycast-based scrubbing; (d) BGP FlowSpec + RTBH Remote Triggered Blackhole; (e) DNS-based redirect + scrubbing; (f) Rate limiting + traffic shaping + ACL filtering; (g) Captcha + JavaScript challenges for App Layer; (h) Threat intelligence + reputation lists. (6) Availability per X.805 Layers: (a) Infrastructure - redundant power + cooling + connectivity + N+1 + 2N hardware; (b) Services - service redundancy + IMS HA + AAA HA + DNS HA + 5G UPF dual-homing; (c) Applications - application HA + microservices resilience + circuit breakers + retry/backoff. (7) Availability per X.805 Planes: (a) Management - OAM HA + redundant management network; (b) Control - signalling HA + redundant routing + BGP graceful restart + NSF Non-Stop Forwarding; (c) End-User - subscriber service HA + Call Continuity (VoLTE + EPS Fallback) + IMS HA. (8) Telecom Carrier Availability: (a) 5-Nines (99.999%) - 5.26 minutes/year downtime; (b) 5G URLLC Ultra-Reliable Low-Latency Communication 99.9999%; (c) Telco BSS/OSS HA; (d) PSTN/E911 emergency call availability; (e) CALEA + lawful intercept availability. (9) Cloud Availability: (a) Multi-AZ + Multi-Region deployment; (b) Auto-recovery + Auto-Scaling; (c) Spot Instance + Reserved Instance mix; (d) AWS Well-Architected Framework Reliability Pillar; (e) Azure Well-Architected Reliability; (f) Google Cloud Architecture Framework Reliability. (10) Threats Mitigated per X.805 Table 1: (a) Destruction (Y); (b) Interruption (Y). (11) Standards: (a) ISO 22301 BCMS; (b) ISO 27031 BC for ICT; (c) NIST SP 800-34 Contingency Planning; (d) NIST SP 800-53 CP family + SC-5 DoS Protection + SI-7 Boundary Protection; (e) ITU-T E.800 Quality of Service; (f) ITU-T X.1314 Botnet-Mitigation; (g) ETSI TS 102 165 Threat Analysis (TVRA); (h) NERC CIP-008 + CIP-009; (i) GSMA Network Equipment Security Assurance Scheme NESAS; (j) 3GPP TS 33.501 5G Security + TS 22.261 5G Service Requirements. (12) Modern Evolution: (a) Chaos Engineering (Netflix Chaos Monkey + Gremlin + Litmus); (b) Site Reliability Engineering (SRE) + Error Budgets; (c) Observability (Metrics + Logs + Traces + OpenTelemetry); (d) Quantum-Resistant Resilience for cryptographic infrastructure; (e) Edge Computing for low-latency availability; (f) 5G Network Slicing for tailored availability. Coordinates with X.805 Layer 1/2/3 + Plane 1/2/3 + Threats Destruction/Interruption + Security Dimension 1 Access Control + ISO 22301 + ISO 27031 + NIST SP 800-34 + 800-53 CP + ETSI TS 102 165 + ITU-T E.800 + 3GPP 5G + GSMA NESAS + AWS Shield + Cloudflare + Akamai. ITU-T X.805 Security Dimension 7 Availability applies.