Transit vs Peering: What's the Difference?
Learn the difference between Internet transit and peering — how networks interconnect, who pays, what each one reaches, and why it matters when you run your own ASN.
Introduction
When you get your own ASN and start announcing prefixes, you hit a question that has nothing to do with technology and everything to do with money and policy:
How does my network actually connect to the rest of the Internet?
The answer comes down to two arrangements: transit and peering. Most interconnections between independent networks are built on one or both. Understanding the difference is the line between paying for bandwidth you don't need and building a network that is both more cost-efficient and faster.
Transit provides reachability to the global Internet — you pay an upstream provider, they carry your traffic everywhere.
Peering exchanges traffic directly between two networks — usually settlement-free, reaching only each other's networks and customers.
If you've read What Is an ASN?, you know networks identify each other by ASN and exchange routes through BGP. Transit and peering are the two commercial and technical agreements that sit behind those route exchanges.
The Short Version: A Delivery Analogy
Imagine two ways to send a package:
- Transit is like hiring a delivery company. You pay them, and they deliver your package anywhere in the world, because they have relationships with every other delivery network.
- Peering is like two neighbors agreeing to hand-deliver each other's mail directly. No postage changes hands — but it only works for mail between the two of them (and their own households).
To reach the rest of the world, the neighbors still need the delivery company. That single analogy captures the whole relationship between transit and peering.
Here is the same relationship drawn as a network topology:
Internet
▲
Transit Provider
▲
Your Network
│
────────── IXP ──────────
▲ ▲
Peer A Peer B
Your network reaches the whole Internet up through a transit provider, and reaches specific peers across an Internet Exchange. Transit and peering are the two kinds of arrows in this picture.
What Is Transit?
Transit is when you pay an upstream network (a transit provider) to carry your traffic to the entire Internet.
In BGP terms, your transit provider announces routes to you — depending on the service, this may be a default route, a full routing table, or another agreed routing policy. A default route means: "Send me everything you don't have a more specific route for, and I'll get it to the rest of the Internet."
Key properties:
- You are a customer. The provider sells you reachability; you pay.
- You reach everything. Through the provider's own network, its transit relationships, and its peering, you can reach the whole Internet.
- It works immediately. One transit relationship and you're globally reachable.
- It costs money, typically per port or per megabit, every month.
A network that buys transit but peers with no one still has full Internet access. Transit is the floor; peering is the optimization built on top of it.
Read BGP Basics for how these routes are actually exchanged between ASNs.
What Is Peering?
Peering is when two networks interconnect directly to exchange traffic destined for each other's networks — and they usually do it settlement-free, meaning no money changes hands.
This model is called bill-and-keep: each network carries the other's traffic without charging, because both benefit symmetrically. Settlement-free peering is the norm, but not universal — paid peering exists when one side gains disproportionately.
Peering happens in two forms:
- Public peering at an Internet Exchange Point (IXP) — a shared switching fabric where many networks connect once and can peer with any other member. Well-known examples include DE-CIX (Frankfurt), LINX (London), and AMS-IX (Amsterdam).
- Private peering (PNI) — a direct physical link between two networks, used when traffic between them is heavy enough to justify a dedicated connection.
Key properties:
- You are a peer, not a customer. The relationship is horizontal.
- You reach only the peer (and its customers). A peer announces its own prefixes and those of its customers — not the entire Internet.
- It is often settlement-free, or occasionally paid peering when one side gains disproportionately.
- It's faster and more resilient for that traffic — a more direct routing path often reduces latency, although latency ultimately depends on routing policy and network topology, not hop count alone.
Transit vs Peering: The Core Differences
| Dimension | Transit | Peering |
|---|---|---|
| Relationship | Provider / customer | Peer / peer |
| Who pays | You pay the provider | Usually no one (settlement-free) |
| Reach | Entire Internet | Only the peer's network + its customers |
| Setup | One transit relationship, immediate global reach | Requires agreement + physical interconnect |
| Path | Through provider's upstreams | Direct between the two networks |
| Typical use | Baseline global reachability | Offload heavy mutual traffic, cut latency |
Put another way:
Customer ──pays──▶ Transit ──▶ Whole Internet
───────────────────────────────────────────
Peer ──exchanges──▶ Direct link ──▶ Specific network
The first path is a purchase that reaches everywhere. The second is a partnership that reaches one neighbor directly.
Transit buys you everywhere; peering buys you a direct, free lane to one neighbor.
Public Peering vs Private Peering
Not all peering looks the same. The two forms serve different scales:
| Dimension | Public Peering (IXP) | Private Peering (PNI) |
|---|---|---|
| Where | Shared switch fabric at an IXP | Dedicated physical link between two networks |
| Setup | One port → many potential peers | One cross-connect → one peer |
| Best for | Connecting to many networks efficiently | High-volume traffic between two specific networks |
| Cost | IXP port fee + membership | Cross-connect + fiber cost |
| Scalability | High — peer with anyone on the fabric | Low — each new peer needs a new physical link |
| Examples | DE-CIX, LINX, AMS-IX, Equinix IX | Direct Netflix–ISP interconnects |
Most networks start with public peering at an IXP — one port opens access to dozens or hundreds of potential peers. Private peering comes later, when a single relationship generates enough traffic to justify its own physical link.
Why Networks Peer Instead of Just Buying Transit
If transit reaches everything, why bother peering at all? Three reasons:
1. Cost. Traffic that flows heavily between two networks is expensive if it all rides paid transit. Peering that same traffic settlement-free can reduce the transit costs you'd otherwise pay for it — though an IXP port, a cross-connect, and the operational upkeep are themselves costs to weigh.
2. Performance. A direct peer link avoids the path going up through a transit provider and back down. A more direct routing path often reduces latency and jitter — noticeable for real-time services like VoIP, gaming, and video conferencing.
3. Control and resilience. Peering gives you an independent path to popular destinations. If your transit provider has an outage, peered routes still flow. This is the same path-diversity thinking behind anycast — giving every destination more than one way to be reached.
A Common Myth: "Peering Means Free Internet"
It doesn't. This is the single most misunderstood point in network interconnection.
Peering only carries traffic between you and the peer (and its customers). It does not give you access to the rest of the Internet. To reach networks you haven't peered with — which is most of them — you still need transit.
Peering is offloading, not replacing. You peer to handle the traffic you share with specific large neighbors directly; you keep transit for everything else. A network that drops transit and relies only on peering simply can't reach most of the Internet.
This is also why large "Tier 1" networks can operate without buying transit: they have enough settlement-free peering with each other to cover the entire Internet among themselves. Everyone below that tier still pays for transit to reach the parts their peering doesn't cover.
Network Tiers at a Glance
| Tier | Pays for Transit? | Peers With | Example |
|---|---|---|---|
| Tier 1 | No — reaches the whole Internet through settlement-free peering alone | Other Tier 1s | AT&T, NTT, Lumen, GTT |
| Tier 2 | Yes — buys transit from Tier 1s, but also peers widely | Tier 1s, other Tier 2s, customers | Most regional ISPs, CDNs, cloud providers |
| Tier 3 | Yes — buys transit, typically has limited or no peering | Upstream transit providers only | Small ISPs, enterprises with their own ASN |
Most networks with their own ASN operate at Tier 2 or Tier 3 — they buy transit for global reach and add peering where the traffic justifies it. You don't need to be Tier 1 to benefit from peering; you just need enough mutual traffic to make the direct path worthwhile.
What This Means for Your Own ASN
When you sponsor an ASN and announce your own prefixes, the practical path is straightforward:
- Buy transit from one or two providers. This is your baseline — full reachability, immediately. Two providers give you the resilience of having more than one path to the world. If you're just starting out, read How to Get Your Own ASN for the full setup process.
- Peer at IXPs. Once you have real traffic volume, connect to a local IXP and peer with the networks you exchange the most traffic with. This cuts cost and latency on your heaviest flows.
- Tune with BGP policy. Use communities and Local Preference to decide which provider is primary, which peers to prefer, and how to steer traffic — the same controls covered in BGP Basics.
- Protect your routes. As you add transit and peering sessions, make sure your prefix announcements are secured with RPKI so no one hijacks the routes you've worked to establish.
You don't need peering on day one. You need transit on day one. Peering is the supplement you add once there's enough traffic to make the direct lanes worth the operational effort — and once you do, your network is both lower-cost and better performing than transit alone.
FAQ
Is peering always free?
Usually, yes — settlement-free peering is the norm between networks of comparable size. But "paid peering" exists when one side derives much more value and agrees to pay for the interconnection. The default assumption, though, is no money changes hands.
Do I need my own ASN to peer?
Yes, in practice. Peering is an arrangement between Autonomous Systems, identified by ASN. To peer, you announce your own prefixes via BGP — which requires an ASN. You can still use peered networks as a customer without holding one, but you can't be a peer yourself.
Can a small network get peering?
Absolutely. Internet Exchange Points have open membership — a small network can connect to a shared fabric and peer with much larger ones. The barrier is operational (configuring BGP sessions, maintaining the connection), not size. Many IXPs offer low-cost ports specifically designed for smaller networks.
Does peering replace transit?
No. Peering only reaches the peer's network and its customers. You still need transit for the rest of the Internet. Peering offloads heavy mutual traffic; it doesn't replace global reachability. A network without transit can only reach its peers — which is a tiny fraction of the Internet.
What is a Tier 1 network?
A Tier 1 network is one that can reach the entire Internet through settlement-free peering alone — it pays no one for transit. Tier 1s achieve this by peering with each other to cover the whole global routing table collectively. The exact number of Tier 1 networks changes over time as the industry consolidates and new networks grow.
Is an IXP the same as a peer?
No. An IXP is the infrastructure (a shared switch fabric) where many networks physically meet. Peering is the agreement you make with individual networks at that IXP. One IXP connection can lead to dozens of peering relationships — the IXP provides the meeting place, not the relationship itself.
Can I peer without an IXP?
Yes. Two networks can establish private peering (PNI) — a direct physical link between them — with no exchange in between. High-volume interconnections (like Netflix and a major ISP) are often private for exactly this reason: when traffic is heavy enough, a dedicated link is cheaper and more reliable than routing through shared fabric.
How does transit pricing work?
Transit is typically priced per megabit per second (Mbps) at a committed data rate, with burst above the commit charged at a higher variable rate. Larger commitments get lower per-Mbps pricing. Some providers also offer flat-rate ports at lower speeds. Prices vary by region — major European Internet hubs are generally among the most competitive transit markets, due to the dense concentration of networks at exchanges like DE-CIX and AMS-IX.
Conclusion
Transit and peering are the two ways independent networks connect, and the difference is really a difference in relationship. Transit is a purchase: you pay a provider to carry your traffic everywhere. Peering is a partnership: two networks exchange their own traffic directly, usually for free.
Neither replaces the other. Transit is the floor — full reachability, available the moment you connect. Peering is the complement — a faster, more resilient direct path to the specific neighbors you exchange the most traffic with. Most real networks run both: transit for the world, peering for the heavy hitters.
For anyone running their own ASN, the practical path is simple. Start with transit from one or two providers for baseline reach and resilience. Add peering at Internet Exchange Points once the traffic justifies it. Understand the difference between the two, and you'll build a network that is both lower in transit cost and better performing than transit alone would ever give you.
Key Takeaways
- Transit is a purchase: you pay a provider for reachability to the entire Internet.
- Peering is a partnership: two networks exchange their own traffic, usually settlement-free.
- Peering reaches only the peer's network and its customers — not the whole Internet. Peering offloads; it doesn't replace transit.
- IXPs are shared fabric where many networks meet and peer; PNIs are direct links between two.
- Public peering (IXP) scales to many peers from one port; private peering (PNI) is for high-volume single relationships.
- Run both: transit for baseline global reach, peering to offload heavy traffic and cut latency.
In One Sentence
Transit buys reachability to the Internet. Peering exchanges traffic directly with another network.
Continue Reading
- What Is an ASN? A Complete Beginner's Guide — the network identity you need before you can buy transit or peer.
- BGP Basics: How the Internet Learns Where to Send Traffic — the protocol that makes transit and peering route exchanges possible.
- How to Get Your Own ASN — the step-by-step path from zero to announcing your own prefixes.
- What Is RPKI? Securing BGP Route Advertisements — protect the transit and peering routes you advertise from hijacking.
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