PNI vs public IXP peering
PNI is a dedicated 1:1 link between two networks; public peering exchanges traffic over a shared IXP fabric. We compare cost, capacity, control and use cases.
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PNI (Private Network Interconnect) is a dedicated point-to-point link connecting two autonomous networks directly. Public peering exchanges traffic with many networks at once over a shared internet exchange (IXP) fabric. Both rely on BGP and serve the same goal, namely direct traffic exchange that bypasses paid transit, but they differ in how they connect physically, their cost model, the capacity available and the degree of control you have over the path.
| Aspect | PNI (private peering) | Public peering (IXP) |
|---|---|---|
| Medium | A dedicated cross-connect | The exchange's shared fabric |
| Who you exchange with | One network | Many members over a single port |
| Entry cost | Higher: a port and cross-connect per pair | Lower: one port, many partners |
| Capacity | Dedicated and predictable | Shared with traffic to other members |
| Fault isolation | Complete, a problem affects one pair | An exchange fault hits many sessions at once |
| Session setup | Individual arrangements with the partner | Often through route servers |
| When it pays off | When traffic with one network is large and steady | At the start and for scattered traffic |
How each connection works
In public peering you connect a single port to the IXP's shared layer 2 fabric and, through that one interface, establish BGP sessions with dozens or hundreds of other members, often via a route server. A PNI is a separate cross-connect or VLAN dedicated to a single pair of networks. The whole port and its capacity are reserved for traffic between you and one partner. The difference comes down to resource sharing: public peering splits one port across many neighbours, while a PNI dedicates an entire port to one.
- Public peering: one IXP port, many BGP sessions, optionally via a route server.
- PNI: a dedicated cross-connect or VLAN, one BGP session with one partner.
- Public peering scales the number of neighbours, while PNI scales capacity to one neighbour.
- A PNI requires both sides to agree on the cost and location of the link.
Cost and capacity
Public peering has a low entry cost: you pay for one IXP port (typically 1G, 10G or 100G) and a membership fee, then exchange traffic with many networks at no per-session charge. A PNI incurs the cost of a cross-connect and often a longer circuit, but it removes contention for the shared fabric's capacity. Once traffic to a single partner steadily approaches half of your IXP port capacity or exceeds a few Gbps, a PNI usually works out cheaper per bit and gives you guaranteed, unshared throughput.
Control, quality and fault isolation
A PNI gives you full control over the 1:1 link: you know the exact capacity budget, can engineer traffic precisely and never compete for bandwidth or MAC-address table space with other members. A fault or misconfiguration by a neighbour on the shared IXP fabric can affect your whole port, whereas a PNI isolates the two of you from the rest. Public peering offers large leverage in return: a single session with a route server gives instant reach to hundreds of networks, which would be inefficient to replicate with separate PNIs.
- Choose public peering for many partners with small to medium volume.
- Choose a PNI for single partners that generate large, steady traffic.
- A PNI isolates you from faults and errors of other IXP fabric members.
- Public peering lowers the entry barrier and speeds up adding neighbours.
- A common threshold to migrate to a PNI is a few Gbps to one network.
PNI and public peering on the AS202520 SkyPass network
At AS202520 SkyPass the two models complement each other. Through our peering services and ports at Polish IXPs (THINX, TPIX, WRIX and 1-IX) you establish public peering with many networks at once using those exchanges' route servers. When traffic to a specific partner grows, we provision a dedicated PNI over a cross-connect at our Warsaw and Wrocław PoPs and take that volume off the shared fabric. We also offer remote IXP access, so you can reach public peering without your own presence in the colocation facility.
Frequently asked questions
How is PNI different from public peering in one sentence?
A PNI is a dedicated 1:1 link between two networks, while public peering exchanges traffic with many networks over a shared IXP fabric on a single port.
When is it worth moving from public peering to a PNI?
When traffic to a single partner steadily approaches half of your IXP port capacity or exceeds a few Gbps. A PNI then usually becomes cheaper per bit and gives guaranteed, unshared throughput.
Does a PNI require a route server?
No. A PNI is a single BGP session directly with one partner. Route servers belong to public peering, where one session gives reach to the routes of many IXP members at once.
Will another IXP member's outage affect my PNI?
No. A PNI runs over a separate cross-connect or VLAN and is isolated from the shared layer 2 fabric, so problems with other IXP members do not touch that link.