What IP Prefixes Measure — And Why 100,000 Is a Big Deal

When I first read that Singtel has ~100,000 IPv4 prefixes while Simba has ~40, the number itself meant nothing. What does a “prefix” even measure? And why would a Singapore ISP have more prefixes than Malaysia’s TM (10,000) or Indonesia’s Telkom (10,000)?

What Is a Prefix?

A prefix is a block of IP addresses that a network owns and announces to the internet via BGP.

Think of it like telephone number ranges:

A small ISP might own one prefix: 192.0.2.0/24 — that’s 256 IP addresses
A large ISP might own thousands of prefixes across many countries
Each prefix is a block they can route traffic to without going through a middleman

The notation 192.0.2.0/24 means “the 256 addresses from 192.0.2.0 to 192.0.2.255.”

Why More Prefixes = Bigger Network

When an ISP has many prefixes, it means:

They own more IP address space — they acquired it early or bought it
They have more customers — each customer or facility needs IP blocks
They are present in more locations — different countries, data centres, submarine cable landing stations
They peer directly with more networks — instead of buying transit, they exchange traffic directly

Why Does Small Singapore Have Such a Big ISP?

This is the counterintuitive part. Singapore has 5.6 million people. Malaysia has 34 million. Indonesia has 280 million. Yet Singtel has 10x the prefixes of TM or Telkom.

The reason: Singtel is not just a local ISP. It’s a regional transit provider. Those 100K prefixes include:

IP space for Singtel’s own customers in Singapore
IP space for the submarine cables Singtel owns or co-owns
IP space for wholesale transit customers across Southeast Asia
IP space for data centres and infrastructure Singtel operates globally

Malaysia’s TM and Indonesia’s Telkom primarily serve their domestic markets. Singtel, by historical accident and deliberate government strategy, became the region’s backbone carrier.

The Practical Impact

More prefixes means:

Fewer hops to reach destinations (direct peering)
Better redundancy (more paths available)
Better peering leverage (content providers want to connect directly)

But for you, the end user in Singapore, loading google.com at 4ms latency — none of this matters. The route is already optimal.

Prefixes as a Proxy for Network Quality

Prefix count isn’t a perfect metric. A network could announce many small prefixes and look bigger than it is (prefix hijacking used to be a problem). But combined with AS rank (which measures how central a network is to internet routing), it’s a decent proxy for network size and importance.

On the CAIDA AS rank, Hurricane Electric (AS6939) sits at #6 globally with 210,000 prefixes and connections to ~7,700 other networks. Singtel doesn’t crack the top tier — it’s a large regional player, not a global backbone.