# IPT vs DIA vs dedicated line for China

Internet transit, dedicated internet access and private lines are three ways to carry Latin America–China traffic. Each buys a different path, capacity model and responsibility boundary: public transit shares the internet, DIA gives committed access, and a private line carries point-to-point capacity for internal use.

- Transit buys reachability, DIA buys office-grade access, private lines buy named-point capacity.

- Filing and transfer steps are scoped with counsel; this page is not legal advice.

- IP transit is sold as a committed rate with a BGP session; a private line is fixed capacity between two named points.

- Light in fiber travels at about 200,000 km/s, so 1,000 km of path adds roughly 5 ms one-way.

## The three in one minute

IP transit, dedicated internet access (DIA) and a private line are different products. They are not tiers of one pipe, and extra bandwidth on one does not turn it into another.
IP transit buys reachability. You connect to an upstream, receive a BGP session and a routing table, and pay for a committed rate with some burst. The upstream's peering and the congested points between you and the destination decide the rest. [DIA](/en/resources/glossary/dia/) buys a business-grade on-ramp: symmetric bandwidth, static addresses, a local loop and a contract that covers the access circuit. It ends at the public internet like any other access service. A private line buys fixed capacity between two named points, handed off as Ethernet (IEPL) or as legacy time-division capacity (IPLC), and it does not connect to the public internet. The [IP transit](/en/resources/glossary/ipt/) entry covers the base product, and [IEPL](/en/resources/glossary/iepl/) and [IPLC](/en/resources/glossary/iplc/) cover the two private-line handoffs.
Ask what sits at the demarcation point. A BGP session and a routing table mean transit. An Ethernet port with a public address and a default route mean access. An Ethernet port that reaches only one distant port means a private line.

### The three products side by side

|  | IP transit | DIA | Private line |
| --- | --- | --- | --- |
| What you buy | Reachability through an upstream | Committed internet access | A circuit between two named points |
| Capacity model | Committed rate with burst; shared path | Committed access rate; shared internet beyond the handoff | Fixed capacity set by the port and the transport |
| Responsibility ends | At the handoff to your network | At the handoff to your network | At the far-end port |
| Fit | Platforms that serve many networks | Offices and branches that need internet | Plants, sites and internal traffic between two locations |

A private line does not become internet access at the far end, and DIA does not reserve capacity across the public internet.

### One physical path, three responsibility boundaries

A schematic, not a map: the local loop, the international segment, the border handoff and the domestic leg. The product you buy decides where the provider's responsibility ends.

Alt: Four segments in a row: local loop, international transit, border handoff and domestic leg, with the handoff marked.

The diagram shows four segments and no real geography. IP transit hands off at a peering or upstream boundary and leaves the public path to reach the destination. DIA adds a committed access circuit and a local loop, then joins the public internet. A private line continues to a named port at the far end. The marked border handoff is where the responsibility model changes, not a cable landing or a carrier facility.

| Item | Value | Note |
| --- | --- | --- |
| First state · 1 | Local loop |  |
| First state · 2 | International transit |  |
| First state · 3 | Border / handoff |  |
| First state · 4 | Domestic leg |  |

Source: ITU-T G.8011: Ethernet service characteristics (https://www.itu.int/rec/T-REC-G.8011)

## Choosing from Latin America

From Latin America the choice follows the traffic. An office that needs email, SaaS and video calls wants DIA or a business internet service with a local loop and a backup path. A content or platform business that serves users in China wants IP transit, because it needs full-table reach and the ability to influence the path through peering and routing policy. A factory, mine or logistics site that exchanges telemetry or bulk files with a Chinese headquarters wants a private line between two named locations.
Most estates use a mix: DIA at the office, transit at the platform edge, private lines for the plant. The [route selector](/en/china/which-route/) turns those answers into a shortlist. The quote should name the handoff and the local loop for each site.
Geography shapes the shortlist. A site far from a carrier hotel may need a longer local loop before international capacity begins. A country with limited terrestrial diversity may need a satellite or microwave backup for the local loop, even when the international path is diverse.

## What each option buys

Read a quote by what is being sold. Transit sells a committed rate, a BGP session and a routing table. Ask whether you get the full table or a partial table with a default route, and how many prefixes the upstream will accept from you. DIA sells an access circuit with a committed rate, a handoff type, static addresses and a local loop. Ask whether the loop is included, whether the circuit is symmetric, and what the backup option is. A private line sells fixed capacity between two named demarcation points. Ask for the handoff (E1, STM-N, 1000BASE-LX or 10GBASE-LR), the committed rate, the protection option and the local loop at each end.
All three can run over the same fiber. The difference is what the contract covers at the demarcation point. Transit scales by adding capacity or peers. DIA scales by upgrading the access circuit. Private lines scale in steps set by the port and the transport, and each new site is a new circuit.

## Latency and the physics floor

Latency between Latin America and China is set first by distance. Light in fiber travels at about 200,000 km/s, so every 1,000 km of path adds roughly 5 ms one-way, or 10 ms round trip. A great-circle path of 16,000 km therefore has a round-trip floor near 160 ms before any equipment, queuing or detour is counted. Real cable paths are longer than the great circle. No product can go below that floor. A good path avoids unnecessary detours, congestion and extra hops.
Use the [fiber latency floor](/en/tools/fiber-latency/) tool to compare city pairs on physics alone, then ask for measured figures for the route you are buying. Do not compare a transit quote with a private-line quote on latency alone: they are measured between different endpoints.

The tool uses distance and a path factor. It does not measure a live route.

[Open the tool](/en/tools/fiber-latency/?src=learn-china-connectivity-options-latam&scenario=mexico-shanghai&pathFactor=1.5)

## What to check before you buy

Ask where the handoff is, who provides the local loop, and what the demarcation point is. Ask whether the quoted capacity is committed or burstable, and what happens when you exceed it. Ask for the route diversity option and whether the backup path shares a conduit or a physical entry point with the primary. Ask how the provider tests the circuit at turn-up: a throughput and latency test with a written result is more useful than a verbal assurance.
Ask what the escalation path is and who answers at each end. If the traffic crosses into mainland China, ask how the provider scopes the cross-border line approval and ICP filing, and take legal advice on your own obligations; this page is not legal advice. The [compliance primer](/en/china/compliance/) explains the concepts, and [China routing explained](/en/resources/learn/china-routing-explained/) covers the three parts of a China-bound path.

Answer four questions about the traffic. The selector returns a product, not a price.

## Common mistakes

Buying transit for interactive traffic and expecting private-line behavior is the first mistake. Buying a private line for general internet access is the second: it is point-to-point capacity, not an on-ramp. Forgetting the local loop is the third, because it can be the slowest part of delivery and the least visible line in the quote. Comparing latency figures measured between different city pairs or with different test methods is the fourth. Assuming that a cross-border circuit removes local filing or data-transfer obligations is the fifth; it does not. Ordering the cheapest handoff and then discovering that the site's router accepts a different interface is the sixth.
Write the handoff, the loop and the test into the order. Keep that list with the contract and the acceptance record.

### Before the order

- [ ] Name the product: transit, DIA or private line. — The demarcation point tells you which one you are buying.
- [ ] Name the handoff and the local loop at each end.
- [ ] Ask for the committed rate and the burst behavior.
- [ ] Ask for the test at turn-up and the acceptance record.
- [ ] Ask who owns escalation at each end.
- [ ] Scope China filing with counsel before you sign.

This list is a buying aid, not legal advice.

### Check what you learned

**A quote offers a BGP session and a full routing table. Which product is it?**

IP transit. The BGP session and the table are the handoff; DIA gives an access port and a default route, and a private line gives a port that reaches one distant port.

**The measured round-trip time is close to the fiber floor. What does that tell you?**

The path is not adding much detour. The remaining delay is distance, so check application round trips and queueing before buying more bandwidth.

**A provider says a private line removes the filing question. Is that right?**

No. A private line changes the path and the responsibility boundary. Cross-border approval and ICP filing depend on the traffic and the entity. Scope them with counsel.

## FAQ

**Can we just use the office internet?**

For browsing and SaaS, yes. For plant telemetry and bulk transfer, scope dedicated capacity instead.

**Do we need a private line or is transit enough?**

If your traffic is public internet traffic to and from many networks, transit is the right tool. If it moves between two named sites and must not touch the public internet, a private line is. Many companies need both.

**What is the difference between IEPL and IPLC?**

Both are point-to-point international private lines. IPLC is the legacy time-division circuit; IEPL hands off Ethernet at each end. The [IEPL vs IPLC explainer](/en/resources/learn/iepl-vs-iplc/) covers the choice in detail.

**Can we start small and grow?**

Yes, within the steps the port and the transport allow. Ask for the upgrade path and the lead time for the next port size before you sign, so growth does not become a new procurement cycle.

**Does a private line fix latency?**

No. It removes some sources of variability and gives you a defined path, but distance still sets the floor. Ask for measured round-trip figures for your city pair, not a general claim.

**Is a cross-border circuit compliant?**

Cross-border lines into mainland China may require approval and are generally for internal company use; ICP filing applies when the site is hosted on servers or a CDN inside mainland China. Scope this with counsel. This page is general information, not legal advice.

## Sources

- [IETF RFC 4271: BGP exchanges network reachability between Autonomous Systems](https://datatracker.ietf.org/doc/html/rfc4271) — Accessed: 2026-10-19
- [ITU-T G.8011: Ethernet service characteristics](https://www.itu.int/rec/T-REC-G.8011) — Accessed: 2026-10-19
- [ITU-T G.652: characteristics of a single-mode optical fibre and cable](https://www.itu.int/rec/T-REC-G.652) — Accessed: 2026-10-19
- [ITU-T G.654: characteristics of a cut-off shifted single-mode optical fibre and cable](https://www.itu.int/rec/T-REC-G.654) — Accessed: 2026-10-19

Updated: 2026-10-19