MetricSplit › Guides › Increase bandwidth or restrict traffic
How to decide: increase bandwidth or restrict traffic
When a WAN link is full, the first option on the table is usually more bandwidth. Often a cheaper fix exists. Work through these steps in order; each one either solves the problem or tells you why you need the next.
1. Confirm the link is really full, and in which direction
Look at how full it runs at its busiest business-hours moments, per direction: the 95th percentile of 5-minute readings over at least a week. If it is under 60% in both directions, the slowness is probably not this link. Over 85% in one direction means users feel it there. (Why daily averages mislead.)
2. Look for room at the same site
If the site has a second link with room at the same moments, moving traffic onto it is the cheapest fix: no purchase needed. Check the result: if both links together would run under 85%, rebalancing solves it. If the site would still run above 60% even balanced, rebalance now and plan an upgrade.
3. Find out what is filling it
Break the busy moments down by application: business traffic, neutral traffic such as updates, backups and sign-in, and non-business traffic such as streaming and social media. Work out how full the link would be without the non-business part at those moments.
- If limiting non-business applications brings the link under 85%, restrict is the fix. Schedule what can wait (large updates, backups) outside business hours.
- If the link is still over 85% with the non-business part removed, restricting won't be enough: the business needs the room.
Restricting traffic doesn't lower the bill on its own: you still pay for the same link. It frees room, and that room is worth money when it avoids an upgrade.
4. Check the failure case
If the site has two links, check whether one could carry the whole site at its busiest moment if the other failed. A site can be fine day to day and still lose service when a link fails. That is a separate decision, about resilience rather than daily load, and it may justify an upgrade on its own.
5. Upgrade the right link, in the right direction
Increase bandwidth when rebalancing and restricting can't bring the link under 85%, or when even a rebalanced site would still run above 60%. Size the upgrade from the direction that is full: an upload bottleneck needs more upload.
A quick decision table
| What you find | Decision |
|---|---|
| Another link at the site has room | Rebalance |
| Non-business traffic is the difference between over and under 85% | Restrict |
| Still over 85% after both, or over 60% even balanced | Upgrade (and rebalance now) |
| The link carries almost nothing | Check the flow export, then price a smaller plan |
MetricSplit makes this decision for every circuit
It measures every WAN circuit per direction, classifies the traffic, checks the cheapest fix first and gives each circuit a decision with the evidence: rebalance, right-size, restrict or upgrade. Once you've entered your circuit prices, each decision shows its cost.