---
title: "Short note: Proxy CDN"
subject: "Internet and Intranet"
chapter: 4
key: "semester_8/internet_and_intranet:note-proxy-cdn"
source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/note-proxy-cdn
site: BCT Engineering
---

# Short note: Proxy CDN

Internet and Intranet · Chapter 4: HTTP and the Web Services

- Asked in: 2071 Bhadra, 4 marks
- Video: [Proxy vs Reverse Proxy (Real-world Examples)](https://www.youtube.com/watch?v=4NB0NDtOwIQ) — ByteByteGo
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/internet_and_intranet/note-proxy-cdn
- Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-4

## Question

Write a short note on Proxy CDN.

## Short answer

A proxy server is a user-side cache reducing bandwidth and latency for outgoing requests. A CDN is a globally distributed system of edge servers that replicates content and directs users to the nearest node via DNS, improving speed and offloading origin servers.

## Answer

A **proxy server** (web cache) is an intermediate server between clients and origin web servers. Clients are configured to send their HTTP requests to the proxy; if it has a fresh copy it returns it, otherwise it fetches the object from the origin, stores a copy and returns it. Benefits: shorter response time, less Internet bandwidth, lower load on origin servers, plus access control, content filtering and logging. Freshness is checked with conditional GET. Examples: Squid, Microsoft ISA/TMG.

A **Content Distribution Network (CDN)** is a network of geographically spread servers that replicate the content of content providers close to users (Akamai, Cloudflare). The CDN's DNS directs each user to the nearest or least-loaded edge server, so objects arrive faster and the origin server is protected from overload.

```text
 Users --> [Proxy cache] --> Internet --> [CDN edge] --> Origin
           (user side:                    (content side)
            inside ISP/company)
```

**Difference in position**
- A **forward proxy** is installed by the user's organisation and is shared by its own users for all sites.
- A **CDN** is installed by (or for) the content owner and serves only its customers' content, to everyone.

A **reverse proxy** at the server side works like a one-site CDN node: it caches, balances load and terminates SSL for the origin servers.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does a proxy cache do when it has a fresh copy of the requested object?
   A. Forwards the request to the origin anyway
   B. Returns the stored copy without contacting the origin
   C. Redirects the client to the nearest CDN
   D. Rejects the request
   Answer: B. A hit is served from the proxy's cache, saving time and bandwidth; only on a miss does it fetch from the origin. (Key point: Proxy operation)

2. How does a CDN direct a user to a suitable server?
   A. Its DNS directs the user to the nearest or least-loaded edge server
   B. The user must pick a server manually
   C. The browser caches every site locally
   D. The origin server forwards all traffic itself
   Answer: A. CDN DNS returns the address of an edge server near the user or lightly loaded, speeding delivery and shielding the origin. (Key point: CDN request routing)

3. Who installs a forward proxy, compared with a CDN?
   A. Forward proxy by the content owner; CDN by the user's organisation
   B. Both are installed by the user's ISP only
   C. Forward proxy by the user's organisation for its own users; CDN by or for the content owner for its customers' content
   D. Both are installed by the content owner
   Answer: C. A forward proxy is on the user side and serves all sites; a CDN is on the content side and serves only its customers' content. (Key point: Position difference)

4. Which description fits a reverse proxy?
   A. A server at the client side that filters outgoing requests
   B. A DNS server that rotates addresses
   C. A router that blocks ports
   D. A server-side node that caches, balances load and terminates SSL, like a one-site CDN node
   Answer: D. A reverse proxy sits in front of origin servers and acts like a one-site CDN node. (Key point: Reverse proxy)