---
title: "Short note: Proxy load balancing"
subject: "Internet and Intranet"
chapter: 5
key: "semester_8/internet_and_intranet:note-proxy-load-balancing"
source: https://www.bctengineer.com/q/semester_8/internet_and_intranet/note-proxy-load-balancing
site: BCT Engineering
---

# Short note: Proxy load balancing

Internet and Intranet · Chapter 5: Designing Internet Systems and Servers

- Asked in: 2074 Bhadra, 4 marks; 2073 Magh, 4 marks (asked 2 times)
- Video: [Proxy vs Reverse Proxy vs Load Balancer | Simply Explained](https://www.youtube.com/watch?v=xo5V9g9joFs) — TechWorld with Nana
- 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-load-balancing
- Whole chapter: https://www.bctengineer.com/md/semester_8/internet_and_intranet/chapter-5

## Question

Write a short note on Proxy load balancing.

## Short answer

Proxy load balancing spreads requests across a proxy array to avoid overload and improve availability. Methods include DNS round robin, hardware load balancer, hash-based CARP, redundant arrays, and ICP. Benefits are faster responses, higher hit ratio, scalability, fault tolerance, bandwidth savings, and easier maintenance.

## Answer

**Proxy load balancing** means spreading client web requests across several proxy (cache) servers so that no single proxy is overloaded, while keeping response time low and service available if one fails. The proxies form a **proxy array** that appears to clients as one logical proxy.

**Methods**
- **DNS round robin:** one name maps to many proxy IPs, used in turn. Simple, not load or failure aware.
- **Hardware / layer 4-7 switch:** spreads connections by round robin or least connections and monitors the health of proxies.
- **Hash-based array (CARP):** the URL hash picks one proxy, so each object is cached once and the total cache adds up.
- **Redundant array:** objects are held in more than one proxy so a failure causes no cache loss.
- **ICP hierarchy:** proxies query siblings before the origin.

```text
 Clients --> [Load balancer / PAC] --> [P1][P2][P3] --> Internet
```

**Benefits:** faster responses, higher cache hit ratio, scalability (add proxies as demand grows), fault tolerance, less WAN bandwidth use, and easier maintenance.

**Tools:** Squid with CARP or cache peers, WCCP-capable routers, HAProxy.

## Check yourself

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

1. What is the aim of proxy load balancing?
   A. To give each user a separate cache
   B. To remove the need for an origin server
   C. To spread requests so no single proxy is overloaded and service stays available
   D. To block websites
   Answer: C. Requests are shared over a proxy array so response time stays low and a failure does not stop service. (Key point: Purpose)

2. What extra capability does a hardware layer 4-7 switch have over DNS round robin?
   A. It monitors proxy health and can use least connections
   B. It stores objects itself
   C. It hashes the URL only
   D. It needs no hardware
   Answer: A. The switch can spread by round robin or least connections and detects failed proxies. (Key point: Layer 4-7 switch)

3. What is the benefit of a redundant array?
   A. Larger total cache
   B. Fewer proxies needed
   C. A proxy failure causes no cache loss because objects are held in more than one proxy
   D. No need for load balancing
   Answer: C. Objects stored in several proxies survive a failure, at the cost of effective cache size. (Key point: Redundant array)

## Related in Internet and Intranet

- [Proxy array load balancing types for big ISP](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aproxy-array-lb-mechanisms-isp) — Internet and Intranet, chapter 5
- [Proxy load balancing benefits; non-redundant array](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aproxy-lb-benefits-non-redundant) — Internet and Intranet, chapter 5
- [RADIUS; proxy load balancing with CARP](https://www.bctengineer.com/question.md?key=semester_8%2Finternet_and_intranet%3Aradius-proxy-lb-carp) — Internet and Intranet, chapter 5