Internet Exchange Points (IXPs) Explained
Understand how Internet Exchange Points work, why they reduce latency and transit costs, and how networks peer at IXPs.
What Is an Internet Exchange Point?
An Internet Exchange Point (IXP) is a physical location where multiple networks connect their routers to exchange traffic directly, rather than routing through third-party transit providers.
Without IXP:
Network A -> Transit Provider -> Transit Provider -> Network B
($$$ per Mbps, higher latency)
With IXP:
Network A -> IXP switch fabric -> Network B
(free or low-cost, lower latency)
Why IXPs Exist
IXPs solve two fundamental problems:
- Cost -- Transit bandwidth costs money (typically $0.50-5 per Mbps/month). Peering at an IXP is usually free or flat-fee, regardless of traffic volume.
- Latency -- Direct interconnection at an IXP eliminates unnecessary hops through transit networks.
How IXPs Work Physically
An IXP is essentially a large Layer 2 switching fabric in a data center:
| Component | Purpose |
|---|---|
| Switch fabric | High-capacity Ethernet switches (100GE/400GE) |
| Peering LAN | A shared VLAN where members connect |
| Route server | Optional BGP route server for multilateral peering |
| Colocation | Rack space for member routers |
Each member connects a router to the IXP switch fabric and establishes BGP sessions with other members.
Peering Types at IXPs
Bilateral Peering
Two networks negotiate a direct BGP session between their routers:
AS 13335 (Cloudflare) <--BGP session--> AS 32934 (Facebook)
Bilateral peering requires negotiation and is typically used between large networks that exchange significant traffic.
Route Server (Multilateral) Peering
The IXP operates a route server that acts as a BGP intermediary:
AS 13335 -> Route Server -> AS 32934
-> AS 16509
-> AS 20940
One BGP session to the route server gives you routes from all participants. This dramatically simplifies setup for smaller networks.
Largest IXPs by Traffic
| IXP | Location | Peak Traffic | Members |
|---|---|---|---|
| DE-CIX Frankfurt | Germany | 14+ Tbps | 1,100+ |
| AMS-IX | Netherlands | 12+ Tbps | 900+ |
| LINX | London | 8+ Tbps | 950+ |
| Equinix IX | Global (30+ locations) | Varies | 2,000+ |
| IX.br (PTT) | Brazil | 25+ Tbps | 2,500+ |
Joining an IXP
Requirements to join most IXPs:
- Own an ASN -- You need your own Autonomous System Number.
- Own IP space -- At least a /24 IPv4 or /48 IPv6 prefix.
- Physical presence -- A router in the IXP's data center (or a remote peering service).
- IRR records -- Maintain up-to-date routing registry entries.
- Agree to peering policy -- Most IXPs require open peering (accept peering requests from any member).
Impact on Internet Architecture
IXPs are critical infrastructure. In regions with strong IXPs, local traffic stays local:
- Before IXPs in Africa: Traffic between two ISPs in the same city routed through Europe.
- After KIXP (Kenya), NAPAfrica (South Africa): Traffic stays in-country, reducing latency from 200ms to 5ms.
IXPs also improve resilience -- if a transit provider fails, direct peering paths at the IXP continue to work.