Backbone capacity numbers like 10G, 100G, 400G and “multi‑terabit” are everywhere in network marketing, but they are often poorly explained. They sound powerful, yet it is not always clear what they mean in practice or whether they represent real, usable capacity across the network. Understanding these numbers and how they fit together helps you choose providers, compare offers, and see through vague “massive backbone” language.
How 10G, 100G and 400G Build a Backbone
Modern backbones are built from standard‑speed building blocks: 10G, 100G and 400G circuits. Each circuit is like a lane on a highway. The total capacity between two locations is the sum of all those lanes and how they are combined and protected.
- 10G circuits are still widely used for smaller interconnects, edge links and legacy equipment.
- 100G circuits are the workhorse for many regional backbones and data‑center‑to‑data‑center links.
- 400G circuits and above are used to move very large volumes of traffic between major hubs.
A “400G backbone” between two sites can mean very different things: one unprotected 400G link, four 100G links bundled as 400G, or several 400G links for 800G, 1.2 Tbit/s or 1.6 Tbit/s total. The headline number alone does not tell you how many circuits there are, how they are arranged, or how the network behaves if something fails.
Typical circuit uses
| Circuit speed | Common uses |
|---|---|
| 10G | Smaller interconnects, access/edge, legacy |
| 100G | Regional backbone, DC‑to‑DC, larger customers |
| 400G | Core backbone, major hubs, high‑density paths |
The Gap Between Optical and IP Capacity
Capacity numbers get more confusing when optical and IP layers are mixed together. The optical layer might support, for example, 1.6 Tbit/s of wavelength capacity between two data centers, composed of several 100G or 400G waves. The IP layer on top may currently use only a portion of that, such as 400G or 800G of lit IP links.
This distinction matters. Optical capacity describes how much traffic the fiber and DWDM system could carry if fully equipped. IP capacity describes how much routed traffic can actually move between those sites right now. A provider can correctly claim “1.6 Tbit/s optical backbone” between locations, while only running 400G of live IP capacity there today. The remaining headroom is useful, but it is potential capacity, not current throughput.
Capacity layers at a glance
| Layer | What the number describes |
|---|---|
| Optical | Total possible 10G/100G/400G “waves” on the fiber |
| IP | Live routed links (e.g. 4 × 100G = 400G IP) |
Reading 10G, 100G, 400G and Multi‑Tbit Claims
Many public backbone claims are technically correct but incomplete. To make sense of “100G backbone”, “400G core”, or “multi‑Tbit global network”, you need to translate them into concrete details: how many circuits, which speeds, where they run, and how they are protected.
When you see a capacity claim, useful clarifying questions include:
- Is this the capacity of one link, one path between two sites, or the whole network?
- How many 10G, 100G and 400G circuits make up that figure?
- Is this optical capacity, lit IP capacity, or a mix?
- Is the capacity protected (with diverse paths or redundant circuits) or a single point of failure?
Claim vs what you should ask
| Claim on a website | What you should clarify |
|---|---|
| “400G backbone in Region X” | Single 400G link, 4 × 100G, or multiple 400G? |
| “1.6 Tbit/s between DCs” | Optical vs IP; what’s lit now vs headroom? |
| “Multi‑Tbit global backbone” | Aggregate of all links or per‑region figures? |
By asking how many 10G, 100G and 400G links exist, how they are grouped, and how they are protected, you turn a marketing headline into something you can actually compare between providers.
Why Backbone Capacity and Speeds Matter for Real Traffic
Backbone capacity, and the way 10G, 100G and 400G links are used, directly affects performance, reliability and growth. When there is enough headroom, the network can absorb traffic spikes, maintenance and failures without pushing links into congestion. When capacity is tight or poorly distributed, even modest shifts in traffic can cause packet loss or latency spikes that users notice immediately.
For customers, a well‑built backbone means:
- More stable performance at peak times
- Room to increase bandwidth commits without constant redesign
- Better resilience when a 10G, 100G or 400G circuit fails, because others can take over
It also allows providers to introduce new services, like higher‑speed customer waves or additional IP transit, without running the backbone at the edge of its limits.
Evaluating Providers Beyond the Headline Number
To judge a network, the presence of 10G, 100G and 400G links and multi‑Tbit numbers is just the starting point. You also want to understand how those circuits are arranged, what redundancy exists, and how the provider operates the network day‑to‑day.
Key areas to examine:
- Topology: Are there diverse paths between major data centers, or does most traffic depend on a single route?
- Redundancy: Are critical paths built from multiple 10G/100G/400G links with failover, or from one big unprotected link?
- Headroom policy: Does the provider keep clear utilization targets on its 10G/100G/400G circuits, or run them close to full and upgrade only when there are problems?
A provider that talks clearly about where 10G, 100G and 400G are used, how they scale to multi‑Tbit capacities, and how they handle failures is usually easier to trust than one that only quotes a single large number.
Turning Backbone Numbers Into Real Decisions
Once you understand what 10G, 100G, 400G and multi‑Tbit claims mean, you can make better decisions about where to place infrastructure, which networks to trust for latency‑sensitive workloads, and how much room you really have to grow. Instead of chasing the biggest headline capacity, you can focus on how the backbone is built and whether it matches your performance and reliability expectations.
If you are evaluating connectivity options or planning new deployments and want to talk through how 10G, 100G, 400G waves and backbone capacity translate into real‑world performance for your applications, reach out at sales@shifthosting.com to start a deeper discussion.
