Choisir fixed bandwidth when you need a set service rate and predictable bandwidth charges. Choose burstable bandwidth when your traffic usually runs below its occasional peaks, extra capacity is available under the plan, and you can accept changes in the bill.
If your service must handle a certain rate during busy hours, start with the capacity the provider commits to deliver. A burstable plan can include guaranteed bandwidth at its base rate, with extra capacity available above that rate under separate terms.
The decision comes down to three questions. What rate can you count on? How fast can the connection go? Which traffic measurements affect the bill?
Fixed vs Burstable Bandwidth at a Glance
| What to compare | Fixed-rate bandwidth | Bandwidth with a burst option |
|---|---|---|
| Purchased rate | Set in the service order | Usually includes a base rate or billing commitment |
| Speed above the purchased rate | Typically capped at the configured service rate | May rise to a stated burst ceiling |
| Capacity during congestion | Depends on the scope of the written guarantee | Depends on the guarantee for the base rate and the policy for extra capacity |
| Monthly bandwidth charge | Predictable when the bandwidth component has a flat price | May include overage under the billing method in the agreement |
| Best fit | Steady demand, tight budgets, or workloads with a firm minimum rate | Occasional peaks, flexible jobs, or services that can adapt if burst capacity falls |
| Main risk | Traffic can queue or drop if demand exceeds the configured rate | Extra capacity may be unavailable or cost more than expected |
Treat the table as a starting point. Ask the provider whether “fixed” refers to the service rate, its monthly price, or both. For example, Cologix describes a fixed bandwidth option with a cap and a separate burstable option that measures excess usage under its contract. See the Cologix service agreement in the references.
What Do Fixed, Guaranteed, and Peak Bandwidth Mean?
Fixed bandwidth
Fixed bandwidth is a service provisioned at a set rate. If you buy a fixed 500 Mbps service on a 1 Gbps port, the physical interface can run at 1 Gbps while the service enforces a lower rate. The rate listed on the port and the rate purchased for the service describe different things.
A flat bandwidth charge makes budgeting easier. Check whether the quote also lists a transfer allowance, setup fee, or other charges.
Guaranteed bandwidth
Guaranteed bandwidth is the rate the provider commits to under specified conditions. The contract may call it the committed information rateou CIR. Check which endpoints and traffic directions the guarantee covers, how the provider measures performance, and what remedy applies.
Read the billing commitment separately. A quote may use commit to describe the minimum amount you pay each month. Ask the provider to state the capacity commitment and minimum billed rate in separate lines.
Peak bandwidth
Peak bandwidth can mean the highest rate the provider configures or the highest rate you measure. Some service agreements call the configured ceiling the peak information rateou PIR.
For example, suppose a service uses a 10 Gbps port, has a 5 Gbps configured burst ceiling, and reaches 4 Gbps during a test. Those three numbers describe the interface, the service limit, and the measured result. An application may achieve a lower rate because of the network route, the remote endpoint, storage speed, or CPU load.
How Does Burstable Bandwidth Work?
Suppose you buy a service with a 1 Gbps committed rate, un 5 Gbps burst ceiling, et un 10 Gbps port. Normal traffic fits within the 1 Gbps rate. During a software release, the service may let traffic use more capacity, up to 5 Gbps, under the provider’s burst policy.
Ask what happens if demand rises above the ceiling. The service may queue packets, drop them, or apply another rate policy. Queued traffic can take longer to arrive. Dropped packets can require retransmission and slow down transfers. For a live stream, test what viewers experience when traffic approaches the service limit.
Also ask whether burst capacity depends on spare network capacity or a time limit. Best effort means the provider attempts to carry the traffic without a stated performance guarantee for that portion of the service. If the workload must run at 3 Gbps during a busy period, plan around capacity covered at that rate.
Cloud network bursting uses different rules
Some cloud instances can burst above a baseline using network credits. For example, AWS documents that some EC2 instances spend network I/O credits above their baseline and return to that baseline when the credits run out. AWS describes that extra capacity as best effort. Credit rules govern available performance. A percentile charge, where offered by a carrier or host, governs the invoice. See the AWS network bandwidth documentation in the references.
How Does 95th-Percentile Bandwidth Billing Work?
Some providers use the 95th percentile to bill bandwidth. In one common model, the provider samples traffic at regular intervals, sorts the readings from highest to lowest, and removes the highest 5%. The highest remaining reading determines the billable rate.
If the agreement includes a base charge and bills only the amount above the commitment, use this formula:
Monthly bandwidth charge = base charge + max(0, billable Mbps − committed Mbps) × overage price per Mbps
Use the provider’s method to calculate billable Mbps. One service may calculate a percentile for each direction and use the larger result. Another may pick the larger direction for each interval before it sorts the readings. Those methods can produce different results if uploads and downloads peak at different times. For multiple ports, confirm whether the provider combines the readings before calculating the percentile or bills each port separately. See the Console Connect, Rackspace, and Zenlayer documentation in the references.
Same 4 Gbps peak, different bill
Consider a fictional 30-day billing period with one traffic direction, a complete set of 8,640 five-minute samples, and these terms:
- Committed rate of 1 Gbps, or 1,000 Mbps.
- Base charge of $500 per month.
- Overage price of $0.40 per Mbps above the commitment.
- Percentile rule that removes the 432 highest samples.
| Traffic pattern | Highest measured rate | 95th-percentile rate | Example monthly charge |
|---|---|---|---|
| 400 samples at 4 Gbps, all others at 1 Gbps | 4 Gbps | 1 Gbit/s | $500 |
| 500 samples at 4 Gbps, all others at 1 Gbps | 4 Gbps | 4 Gbps | $1,700 |
In the first case, all 400 peak readings fall inside the 432 readings the provider removes. In the second case, 68 readings at 4 Gbps remain. The bill includes 3,000 Mbps of overage, which adds $1,200.
The 432 five-minute intervals add up to 36 hours in this example. The calculation ranks readings from across the month. Several separate spikes can occupy those top spots, and a longer event can leave high readings in the billable set. Check how the provider handles partial months, missing readings, and rounding before modeling your own bill.
When does fixed bandwidth cost less?
Suppose a suitable fixed-rate quote costs $900 per month. Under the fictional burstable terms, the two quotes tie at a 2 Gbps billable rate.
1,000 Mbps + ($900 − $500) ÷ $0.40 per Mbps = 2,000 Mbps
Below 2 Gbps, the burstable example costs less. Above 2 Gbps, the fixed example costs less. This comparison covers the bandwidth charges shown. Include setup fees, port charges, minimum terms, and other applicable fees when comparing real quotes.
Check service fit before using the result. If the $900 fixed offer caps throughput below the rate your application needs, its lower bill does little for a release that has to finish by morning.
How Do Transfer Quotas and Unmetered Bandwidth Fit In?
A bandwidth rate tells you how fast data can move. A transfer allowance tells you how much data the plan includes over a billing period. Gbps and Mbps measure rate. GB and TB measure volume.
An sans contrôle offer generally means the plan does not charge by the amount of transfer covered by that policy. The service can still have a port limit, a configured rate, or conditions on its use. A fixed rate can come with a transfer quota or with unmetered transfer. Leaseweb’s documentation shows why buyers should check which metering method applies to each service.
As a quick quote check, put these details on separate lines:
| Quote detail | Example | What it tells you |
|---|---|---|
| Port speed | 10 Gbit/s | Interface speed |
| Service commitment | 1 Gbit/s | Rate or billing commitment, depending on the terms |
| Burst ceiling | 5 Gbps | Highest configured rate for bursts |
| Transfer policy | 100 TB per month | Volume included during the period |
| Overage basis | Per TB or per Mbps | Unit used to calculate extra charges |
The values in this table illustrate how to read an offer. Ask the provider which fields apply and whether different charges can apply in the same billing period.
Which Bandwidth Plan Fits Your Workload?
Start with the traffic that must move on time. Then identify the work you can slow down, schedule later, or serve through another system.
| Workload | Which option to assess first | Why |
|---|---|---|
| Continuous video delivery | Fixed or committed capacity sized for viewing hours | Regular demand needs a rate the service can support throughout the viewing window |
| Software release or patch distribution | Burstable service with a workable fallback | A release may create a short spike. Repeated spikes can raise the billable rate |
| Nightly backups | Fixed capacity sized for the backup window, or bursting if timing is flexible | Moving or pacing a job can reduce overlap with customer traffic |
| E-commerce or SaaS | A committed rate sized for critical traffic | A sale or recurring busy period may make extra capacity a requirement |
| Colocation or IP transit | Compare both quotes using the same port measurements | Direction rules, aggregation, and recurring fees can change the result |
For example, transferring 1 TB of data in two hours requires about 1.11 Gbps of average payload throughput using decimal units, before protocol overhead, retries, or other traffic. A 1 Gbps cap falls short even under ideal conditions. You can buy more capacity, extend the backup window, or reduce the amount of data sent. A burstable plan can fit if it can sustain the required rate for the window and the billing terms fit your budget.
For daily traffic, review at least a complete billing cycle when records are available. Include past launch days, backup windows, and other known busy periods. Keep billing samples for cost estimates and use finer measurements to check short spikes that can affect users.
How to Compare Fixed and Burstable Bandwidth Quotes
- Record the port speed, committed rate, and burst ceiling. Ask for separate numbers for upload and download if the service uses different limits.
- Read the service agreement. Check where the capacity commitment applies and what happens above it during congestion.
- Confirm the billing unit. Identify the flat monthly charge, transfer quota, percentile charge, or applicable combination.
- Request the measurement rules. Ask about the sample interval, direction, port aggregation, rounding, and overage rate.
- Model both quotes with the same traffic data. Include a normal month and a month with more release traffic or larger backups.
- Check your cost controls. Ask whether usage alerts, rate caps, or changes to the commitment are available. An alert helps you act. A configured cap changes what traffic can pass.
- Test the route and workload. Measure sustained throughput from representative endpoints. Check errors and response times under load, and confirm that both ends can handle the target rate.
If a provider advertises “up to 10 Gbps,” ask for the rate it commits to, the conditions for reaching the advertised ceiling, and the rate at which extra charges can begin.
Questions fréquemment posées
Can guaranteed bandwidth also be burstable?
Yes. A plan can guarantee a base rate within the scope of its service agreement and offer extra capacity above it. Ask which part of the service has a capacity commitment and what terms apply to the burst.
Does a 10 Gbps port guarantee 10 Gbps throughput?
A 10 Gbps port describes the interface speed. Check the service’s committed and configured rates, then test the application across a representative route. Throughput can depend on the remote endpoint, concurrent traffic, and how the workload sends or receives data.
Is fixed bandwidth the same as unmetered bandwidth?
Fixed bandwidth describes a set service rate in this guide. Unmetered bandwidth describes a transfer policy. A plan can offer both, such as a fixed-rate service that does not charge per TB for covered traffic.
Does every burstable plan use 95th-percentile billing?
Billing depends on the service agreement. Some providers use 95th-percentile billing for burstable services. Other products describe burst performance separately from transfer charges or base pricing.
How much can I burst before paying extra?
Under a base-plus-overage percentile plan, the bill depends on the rate that remains after the provider applies its sampling rules. The size and frequency of the bursts, the billing direction, and the committed rate all affect the result.
Can I lower my bill by moving backups to another time?
Possibly. Moving a backup may reduce the sampled rate if it stops overlapping with other busy traffic. A move may have little effect if the backup still creates the same high readings by itself. Compare both schedules using the provider’s billing method.
References and Data Sources
- Cologix. Canada Master Services Agreement and Schedules. Fixed and burstable IP bandwidth terms.
- Console Connect. Internet On-Demand Help. Committed rates, burst limits, and percentile billing.
- Leaseweb. Network Metering and Billing. Transfer metering, percentile billing, and aggregation.
- Rackspace. How Rackspace Bills for Bandwidth. Description of a percentile method that selects the larger direction at each interval.
- Zenlayer. Bandwidth Cluster Billing. Regional aggregation and commitment examples.
- Amazon Web Services. Amazon EC2 Instance Network Bandwidth. Baseline rates and network burst credits.
Recommended Next Steps
Write down your sustained rate, peak rate, and longest expected burst. Then compare quotes against the traffic your service must handle and the highest monthly bill you can accept.
If you are sizing a dedicated server, share your traffic history and required capacity with us. We can discuss the port, transfer terms, and available configurations for your deployment. Compare Atal Networks’ 10 Gbps dedicated servers