Blog post
Teams running Internet-dependent services know the frustration: an outage hits a specific ISP, a BGP hijack reroutes traffic in one region, or a CDN degrades for users on certain networks. If you're only monitoring from a cloud provider or a handful of data centers, you won't see it until customers start complaining.
The root cause is structural. The Internet is a patchwork of thousands of independent networks (ISPs, data centers, backbones, wireless carriers, and more), all connected through peering and transit agreements. Monitoring from just one layer of that stack leaves blind spots across the rest. That layered architecture is what we call the Internet Stack.
The Internet Stack
This article breaks down the five types of synthetic monitoring agents (backbone, wireless, last-mile, cloud, and BGP), where each one sits in the Internet Stack, and why each matters for catching problems that single-vantage-point monitoring misses. It's also why Catchpoint, a LogicMonitor company, built a Global Agent Network spanning 3,000+ agents across 395 providers in 105 countries and 346 cities: covering every layer requires that kind of reach. First, let's look at how the Internet actually connects end to end.
Why multiple vantage points are key
The Internet isn't a single cloud. You can't just tap into one place and see it all. It's tens of thousands of independent networks (ISPs, data centers, wireless carriers) stitched together by peering and transit deals. In a peering arrangement, two networks exchange traffic for free. In a transit relationship, one network pays another to carry its traffic. Peering keeps traffic local; transit carries it farther afield.
Because each network makes its own choices about peering and transit, you need monitoring agents at many points to see what's happening. A performance hiccup in one ISP's peering location might not show up at a different ISP's vantage point. That's why we place agents in dozens of key networks, so you won't miss an issue that affects only a slice of the Internet.
A map of how thousands of networks (Autonomous Systems) peer and buy transit around the world. Source
Why tiers matter
All those peering and transit agreements naturally sort networks into tiers:
- Tier 1: These are large global networks that peer with each other and don't need to buy any transit to reach any corner of the Internet. They're considered the backbone of the Internet, as they typically carry long-distance traffic. While the networks in this group have changed since the beginning of the Internet, the group has remained relatively stable, including providers such as Lumen, AT&T, Cogent, Verizon, Orange, GTT, NTT, and Telxius. This category includes large traditional telecom providers that have served their domestic markets for many years.
- Tier 2: Regional providers that both peer and buy transit. The scale of operations and the type of services they provide (IP transit, Ethernet, or dark fiber wavelengths) dictate the number of peering connections and transit providers. Most networks fall into this category if they peer at one or more Internet exchange points and have two or more upstream providers.
- Tier 3: Smaller, local ISPs (often single-homed) that feed to an upstream provider. They show you what your end users see on a residential or localized network.
Putting agents in each tier matters because a Tier 1 network will have more visibility into global events (total or partial outages, backbone congestion, etc.) compared to a regional Tier 2 or a local Tier 3 network. On the other hand, localized outages affecting a limited number of providers in a particular geographic area won't be easily observed unless you have visibility from one of the affected networks.
Why single-homed Tier 1/Tier 2 connectivity matters
Now that we know how networks sort into tiers, let's look at how those tiers influence the way we connect our agents.
Many data centers, hosting providers, and managed service providers typically use multiple upstream ISPs (Tier 1 and Tier 2) to create a single, aggregated connection to the Internet. This connectivity, normally offered as a service, is often called blended bandwidth or multihoming.
Multihoming improves redundancy because traffic can be rerouted if one ISP goes down or has packet loss or congestion. It also improves performance because different ISPs may offer better latency to different geographies.
For Internet Performance Monitoring (IPM), however, using multihomed agents instead of single-homed Tier 1/Tier 2 carriers introduces variability in your monitoring data, making it harder to identify and troubleshoot the issues affecting performance.
Here's why more than 96% of our backbone agents use single-homed Tier 1/Tier 2 connectivity instead of blended bandwidth:
- Path consistency: A consistent Tier 1 upstream path reduces variability, making anomalies and degradations easier to detect and attribute.
- Backbone visibility: Tier 1 visibility is essential to observe how the core Internet behaves in relation to routing anomalies, BGP hijacks, or backbone congestion.
- Performance stability: With blended connectivity, routes may change dynamically based on load-balancing or pricing strategies (for example, BGP-based traffic engineering), affecting performance results.
Now that you understand how and why we choose single-homed Tier 1/Tier 2 connectivity, let's look at each of our five synthetic agent types. We'll explain where we place them, how we build them, and what visibility each one gives you.
Backbone agents
Backbone agents give you a "core-of-Internet" vantage point to catch global outages, BGP hijacks, and CDN-level issues no other agent can see.
We place backbone agents in Tier 1 or Tier 2 ISPs worldwide, selecting carriers by:
- Geography and market importance (global connectivity hubs)
- CAIDA ASRank & APNIC eyeball data (to cover the most interconnected networks)
Each backbone agent runs as a server cluster in a carrier-neutral data center with dedicated IP transit. Carrier neutrality ensures multiple international and domestic carriers via cross-connects, while colocating servers in one facility reduces colocation costs. In emerging markets (for example, parts of Africa or China) where neutral data centers are scarce, we may host clusters in carrier-owned facilities as a last resort.
Connectivity diagram of backbone agents at a data center facility
Measuring performance and availability from backbone agents is critical for:
- Experience Level Objective (XLO) measurements: Validate service performance when source and target share the same ISP.
- CDN performance and validation: Ensure fast, reliable content delivery across the backbone.
- Competitive benchmarking: Compare your service to peers in the same Tier 1/2 networks.
- Peering and ISP monitoring: Detect routing changes, BGP anomalies, or unexpected transit behavior.
- Geo-based DNS validation: Confirm DNS resolution speed and correctness from the core network.
Public cloud agents
Cloud agents give you visibility right inside public-cloud data centers, so you can catch platform-specific issues before they impact users.
To date, Catchpoint runs 280+ cloud agents across every key availability region in AWS, Azure, Google, Oracle, Alibaba, Tencent, Akamai Compute, and OVH.
Measuring performance and availability to and from cloud agents is essential if you're hosting applications in the cloud or using any of their computing products. Cloud agents allow your SRE teams to preemptively detect performance degradations on public clouds that can affect how your users experience your applications and services.
Wireless agents
Wireless agents simulate real-world cellular conditions, giving you a true picture of how your applications perform on 3G/4G/5G networks.
We place wireless agents using AWS Wavelength and independent carriers in the US, Canada, Japan, Germany, Korea, India, and the UK (for example, Verizon, KDDI, BT, T-Mobile 5G, AT&T 5G).
Running wireless tests alongside backbone tests lets you compare mobile experience to core-network performance, so you can spot issues like packet loss or DNS slowdowns that only affect cellular users.
Last-mile agents
Last-mile agents live in real homes, giving you a true end-user view of broadband performance.
Our last-mile agents run on small customer-premise devices that connect to a residential ISP. Use these agents to troubleshoot ISP-specific issues (like throttling, DNS failures, or regional outages) that only affect subscribers on a particular network.
Enterprise agents
Enterprise agents give you visibility into your own network, from branch offices to data centers to edge locations.
Enterprise agents are deployed within your organization's infrastructure. That includes office networks, private data centers, retail locations, or edge devices. These agents help you monitor internal applications, APIs, and services with the same level of granularity you get for external traffic. Combined with our Global Agent Network, enterprise agents complete the picture, giving you visibility from both outside-in and inside-out.
BGP agents
BGP agents watch the real-time routing table, so you can catch hijacks, leaks, or unexpected path changes that threaten your service.
We maintain a route collector infrastructure that processes real-time routing data from 1,700+ BGP agents with the goal of monitoring BGP activity and detecting issues such as route hijacks and leaks.
In addition to using RIPE RIS and RouteViews datasets, we operate our own private collector infrastructure, which includes agreements to receive data from 330+ BGP agents from 100 unique networks.
If you share your own BGP sessions with our private collectors, you'll gain even deeper insights in your portal, so you see exactly how routing anomalies affect your prefixes.
Wrapping it up
When we're asked, "Why build a network of over 3,000 agents in 105 countries and 346 cities?" the simple answer is that today's Internet isn't one giant cloud but a patchwork quilt of independent networks.
By spreading our agents across every layer of the Internet Stack, we can reveal problems at the moment they start, whether it's a routing change in a distant backbone, a subtle slowdown in a public cloud region, or a local ISP hiccup affecting a handful of homes.
This broad visibility matters because whenever something goes wrong, you know exactly where to look. The effort we put into building and maintaining such a diverse network is what helps prevent those 3 a.m. wake-up calls, keeps war rooms from spinning up, and protects your users' experience no matter where they connect.
LogicMonitor's unified platform brings together LM Envision for infrastructure observability, LM Internet Performance Monitoring for Internet-layer visibility, and Edwin AI for intelligence and action. Together, they give teams the context they need to move from reactive troubleshooting to proactive, autonomous operations.
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