CDN Architecture & Components 5 — Questions and Answers
Question 1: What role does an 'Internet Exchange Point' (IXP) play in CDN infrastructure?
- It is a government body that regulates CDN pricing
- It is a physical facility where CDNs and ISPs interconnect to exchange traffic directly (Correct answer)
- It is a type of CDN edge server optimized for video
- It is a protocol for synchronizing cache state between PoPs
Correct answer: It is a physical facility where CDNs and ISPs interconnect to exchange traffic directly
IXPs are neutral facilities enabling CDNs to peer with many ISPs under one roof, reducing latency and transit costs.
Question 2: Which CDN architecture concept describes placing edge servers inside an ISP's own network to eliminate the last-mile hop?
- Embedded CDN / ISP-hosted PoP (e.g., Netflix Open Connect) (Correct answer)
- Reverse proxy clustering
- Anycast scrubbing
- Multi-CDN mesh networking
Correct answer: Embedded CDN / ISP-hosted PoP (e.g., Netflix Open Connect)
Embedded CDNs install appliances directly inside ISP networks so content travels zero hops over the public internet to reach subscribers.
Question 3: What is 'prefetching' in the context of CDN cache warming?
- Removing expired objects from cache before they are requested
- Proactively fetching and caching content at edge nodes before user demand arrives (Correct answer)
- Pre-computing TLS certificates for anticipated domains
- Loading DNS records into edge resolvers before traffic spikes
Correct answer: Proactively fetching and caching content at edge nodes before user demand arrives
Cache warming via prefetch pushes anticipated objects to edge nodes ahead of a live event or product launch so the first user request is a cache hit.
Question 4: In CDN health monitoring, what is an 'active health check' as opposed to a 'passive' one?
- Active checks analyze historical traffic logs; passive checks send live probes
- Active checks send synthetic probe requests to origins/edges on a schedule; passive checks infer health from real user traffic failures (Correct answer)
- Active checks run only during business hours; passive checks run 24/7
- Active checks require a paid CDN tier; passive checks are free
Correct answer: Active checks send synthetic probe requests to origins/edges on a schedule; passive checks infer health from real user traffic failures
Active health checks proactively test endpoints at intervals, enabling failure detection even when no real users are sending traffic.
Question 5: What is the purpose of a CDN's 'WAF' (Web Application Firewall) component at the edge?
- To accelerate TLS handshakes using hardware acceleration
- To inspect and block malicious HTTP traffic (SQLi, XSS, etc.) before it reaches the origin (Correct answer)
- To compress responses using Brotli or gzip at the edge
- To route traffic between CDN PoPs based on latency
Correct answer: To inspect and block malicious HTTP traffic (SQLi, XSS, etc.) before it reaches the origin
An edge WAF applies rule-based and ML-driven inspection to HTTP requests, filtering attacks at the CDN layer before they can harm the origin.
Question 6: What distinguishes a 'pull CDN' from a 'push CDN'?
- A pull CDN fetches content from origin on demand; a push CDN requires the operator to proactively upload content to edge nodes (Correct answer)
- A pull CDN uses HTTP; a push CDN uses FTP only
- A push CDN is always faster than a pull CDN
- A pull CDN caches only images; a push CDN caches all file types
Correct answer: A pull CDN fetches content from origin on demand; a push CDN requires the operator to proactively upload content to edge nodes
Pull CDNs are lazy — they populate caches on first request; push CDNs require explicit content uploads, giving operators precise control over what is cached.
Question 7: Which metric best measures the effectiveness of a CDN cache in reducing origin load?
- Time to First Byte (TTFB)
- Cache Hit Ratio (CHR) (Correct answer)
- DNS lookup time
- TCP connection establishment time
Correct answer: Cache Hit Ratio (CHR)
Cache Hit Ratio is the percentage of requests served from cache without contacting the origin; a higher CHR means less origin load.
CDN Architecture & Components 5
What role does an 'Internet Exchange Point' (IXP) play in CDN infrastructure?