# What real problems does an SD-WAN overlay solve that a decent ISP + firewall doesn't already cover?

I'm getting pressure to justify adding another network vendor into our stack when we already pay for a business-grade ISP connection with an uptime SLA and have failover built into our firewall. My finance team is asking me to justify what we would be paying for that we don't already have? For those of you running an SD-WAN overlay like Bigleaf on top of your existing ISP and firewall — what specific problems did it solve that your ISP's SLA or your firewall's failover didn't catch?

##### Post Metadata
- Posted at: about 1 month ago
- Net upvotes: 3


## Comments
### Comment 1

Fair question for finance to ask, and it deserves a specific answer rather than a general "reliability" pitch — so here are the three actual gaps, mapped directly against the two things you already have.

Your ISP's uptime SLA measures whether the circuit is passing traffic, not whether it's passing traffic well. A circuit can hit 99.9% availability and still be delivering packet loss, jitter, or latency spikes that make VoIP calls choppy and video freeze — none of which counts against the SLA, because the SLA isn't measuring quality in the first place. This is the gap that shows up as "the ISP says everything's fine but our calls are still bad," and it's invisible to both the SLA and a standard speed test.

Your firewall's built-in failover covers a different gap than you might expect — it handles the "primary circuit is down, switch to backup" part fine, but most firewall-based failover assigns a new public IP when it switches circuits. Any session tied to the old IP — an active VoIP call, a VPN tunnel, a cloud app mid-session — gets dropped, not because the failover failed, but because the IP changed underneath it. So "we have failover" and "our sessions survive failover" are two different claims, and it's worth checking which one your setup actually delivers before assuming it's covered.

The third gap is traffic prioritization, and it's the one people usually don't think to ask about at all: without real QoS enforcement, a VoIP call and a background file sync or software update are just competing equally for the same bandwidth. Neither your ISP nor a standard firewall does much to guarantee the call wins that competition automatically.

Concretely, what an overlay like Bigleaf adds on top of what you already have is a combination of continuous circuit monitoring, intelligent load balancing, and QoS that work together to keep cloud applications performing the way the business expects. Bigleaf detects circuit degradation your SLA may not capture, automatically steers traffic across the best available path, preserves active sessions with same-IP failover, and prioritizes real-time traffic so calls and critical apps do not lose to bulk transfers. That out-of-the-box, “it just works” model is a Bigleaf benefit that a decent ISP and firewall simply do not provide—and it translates into business value Finance can care about: less downtime, fewer revenue-impacting disruptions, and less lost staff productivity when connectivity problems would otherwise slow teams down.

Resources that might help make the case internally:

How It Works - https://www.bigleaf.net/platform/how-it-works/ — the mechanism behind all three gaps above.

Bigleaf vs. Failover - https://www.bigleaf.net/blog/bigleaf-vs-failover/ — goes deeper on the SLA-and-firewall-failover gap specifically.

Cost of Downtime Calculator - https://www.bigleaf.net/resources/cost-of-downtime-calculator/ — useful for putting a number on the first gap, which tends to be the one finance actually wants quantified.

##### Comment Metadata
- Posted at: about 1 month ago
- Author title: Digital Marketing Manager




## Related Product
[Bigleaf Networks](https://www.g2.com/products/bigleaf-networks/reviews)

## Related Category
[SD-WAN](https://www.g2.com/categories/sd-wan)

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