Committed Information Rate (CIR) is the data rate that a provider’s bandwidth profile treats as conforming for a circuit or virtual connection, usually stated in Mbps or Gbps and measured over a defined interval. Traffic at or below the CIR is “in profile,” and providers generally give it better treatment than excess traffic, typically up to a defined point in their network. A CIR is not by itself a promise of zero loss or congestion-proof delivery: how in-profile traffic is treated under congestion, and any latency, loss or availability commitments, depend on the provider and must be set out in the SLA or order. Traffic above the CIR may still get through if capacity allows, but it is typically the first to be dropped, slowed or marked down. The term dates from frame relay and is now used across Ethernet, dedicated internet and cloud connection services.
At a glance
- CIR is the part of your bandwidth the provider’s profile treats as conforming; anything above it is best effort.
- It applies within the provider’s network up to a defined point, not the whole path to every application.
- It is not a performance guarantee on its own: latency, loss, availability, congestion treatment, measurement points and remedies belong in the SLA or order.
- On some dedicated internet circuits the CIR equals the port speed; on burstable and Ethernet services it is often lower.
- Voice, video and critical transactions belong within the CIR; backups and updates can use the excess.
What problem it solves
Networks carry a mix of traffic: calls, video meetings, payment systems, cloud apps, backups and updates. When a link or the provider’s network gets busy, something has to wait or be dropped. On a best-effort service, all of your traffic competes on equal terms with everyone else’s, and performance becomes unpredictable.
A CIR turns part of your bandwidth into a planned quantity. Providers generally engineer and prioritize their networks so that in-profile traffic fares better than excess or best-effort traffic when shared links are busy, which lets you size the commitment around the applications that must keep working. How well that holds up is provider-specific, so the CIR is only half the picture: the SLA or order has to state the latency, loss and availability targets, how congestion is handled, where performance is measured and what remedies apply if they’re missed.
How it works
Where you’ll see it.
- Dedicated internet access. Many providers commit the full purchased speed; burstable plans commit a lower rate on a larger port.
- Carrier Ethernet. Point-to-point and multipoint services such as EVPL define a bandwidth profile per virtual connection: CIR and committed burst size, plus an excess rate and excess burst size for traffic forwarded only if capacity allows.
- Private WAN and MPLS. Commitments may be set per site and per class of service.
- Cloud and data center connections. Private links to cloud providers are typically sold at a set rate per connection.
- Broadband. Usually best effort with no CIR.
How it’s enforced. Providers typically use a token bucket. Allowance builds at the CIR, and traffic spends it, up to the committed burst size. Traffic that fits is in profile. Traffic that doesn’t is marked as excess or dropped, depending on the service. On your side, shaping traffic to the CIR at your router smooths spikes into a short delay instead of loss.
How it relates to class of service. Many services let you split the CIR between classes, for example a slice reserved for voice. That only works if your markings are honored end to end, from your LAN through your router to the provider’s network. Pair the CIR with quality of service (QoS) so the right traffic uses the committed capacity.
When it matters for buyers
- Comparing quotes. Two “500 Mbps” offers can differ: one commits 500 Mbps, the other commits 100 Mbps on a 500 Mbps port. Ask for the CIR as a number.
- Sizing for real-time traffic. Work out how much voice, video and transaction traffic must keep working at the busiest hour, in both directions, and make sure the CIR covers it.
- Burstable circuits. If you regularly run above the CIR, compare a higher commitment with the cost of burst usage, which may be billed by 95th percentile.
- Shared networks. Broadband and other heavily oversubscribed services generally have no CIR, which is why they cost less. They make good secondary links.
- SLAs. The CIR alone doesn’t promise performance. Check that the SLA or order states latency, loss and availability targets, how in-profile traffic is treated under congestion, where these are measured, what remedies apply, and whether they cover only in-profile traffic.
Our dedicated internet access page explains how committed circuits are quoted and compared.
Questions to ask vendors
- What is the committed rate, in each direction, and what is the port speed?
- Over what interval is the CIR measured, and what committed and excess burst sizes apply?
- Up to what point in your network does the commitment apply?
- What happens to traffic above the CIR: dropped, marked down or delayed?
- Can the CIR be divided between classes of service, and are our markings honored?
- What latency, packet-loss and availability commitments apply to traffic within the CIR, where are they measured, and what remedies apply if you miss them?
- How is in-profile traffic treated if your network is congested?
- Can we raise the CIR mid-term, how fast, and does it restart the contract?
How it differs from port speed
Port speed, sometimes called access speed, is the physical speed of the connection the provider hands you, such as 1 Gbps. CIR is the rate the provider’s bandwidth profile treats as conforming. They can be the same, as on many dedicated internet circuits, or the CIR can be much lower, as on burstable and Ethernet services where you can send at port speed but only the committed portion is treated as in profile. When a quote states one speed, ask which of the two it is.
Problems this helps with
- Paying for a fast circuit that still slows down at busy times
- Not knowing which part of our bandwidth the provider has actually committed to
- Calls and video breaking up when the network is busy
- Comparing quotes where one speed means different things
