CFP2 vs. QSFP28 For Your 100G Needs


CFP2 vs. QSFP28: Which Transceiver Should You Choose on Your Path to 100G?

So you want to add more 100G capabilities to your network, right? If you answered yes, (and we’re betting you did,) you’re not alone--according to a recent IHS Infonetics report, 100G will account for more than 50% of the data center fiber transceiver market by 2019. 

A big part of improving your 100G capabilities is choosing the right transceiver modules. For many, the choice boils down to either the older CFP models or the newer, smaller form factor QSFP. (To keep things simple, we’ll be comparing the CFP2 and the QSFP28 specifically in this blog.)

At a high level, the comparison is fairly simple: the QSFP28 is smaller, more convenient, and generally more cost effective. But QSFP28s struggle with long haul connections, and currently may not be the best choice to enable 100G connectivity from data center to data center or for other multiple km connection needs.

For longer distances, the CFP2 shines, reliably delivering multi-channel 100G connectivity across more than 1000km. Unfortunately, that long haul low attenuation comes at a price--CFP2s are notoriously bulky and power-hungry.

So the choice is simple, right? Use QSFP28 for local 100G connections and CFP2 for 100G long haul. Well, not exactly--the decision is much more complicated and nuanced than that.

Let’s dive in and take a more holistic look at the comparison. Make sure your gloves are tied tight and you’ve got your boxing (not boxer) shorts on, ‘cause it’s rumble time. And our main event is the CFP2 vs. the QSFP28.

CFP2 vs. QSFP28 Round 1: Form factor

This one isn’t exactly fair, as the newer QSFP28 was designed from the ground up to be smaller and more convenient than the CFP2. But let’s have a look at the numbers and see just how much smaller it is--and why that matters.

The QSFP28 is the smallest form factor 100g transceiver on the market. Overall, the QSFP28 is nearly 80% smaller than the CFP2.

That size difference gives you a significant advantage in port density, allowing you to do more in smaller spaces and with less equipment.

It’s also worth noting that the QSFP28 is the same size as the older 40G QSFP+. So if you’re already using QSFP+, you can make the upgrade without needing to reconfigure everything.

“But wait,” you yell at your screen, to the confusion and dismay of everyone around you, “that’s not a fair comparison! If we’re going to talk about form factor, shouldn’t we be looking at the smaller CFP4 instead?!” That’s a good point, and please calm down, you’re scaring the children.

Despite being ¼ the size of the original CFP, the CFP4 is still about 66% larger than the QSFP28.

“But wait again!” you shout. Dude, we can hear you. “Isn’t the CFP8 smaller, and capable of 400G connectivity?”

While the CFP8 does enable 400G connectivity (for a price), it’s actually larger than the CFP4, only slightly smaller than the CFP2, and still way bigger than the QSFP28. 

Winner: QSFP28

CFP2 vs. QSFP28 Round 2: Power consumption

Power consumption is an important factor in any hardware decision, as it has a direct--sometimes severe--impact on your budget, your network configuration, and your overall bandwidth capabilities. So when it comes to sucking up your juice, which of these transceivers will have the lowest impact?

The CFP2, as with most 100G transceivers, has a power consumption of between 6W and 24W, depending on how heavily it’s used. That’s not too shabby. But…

The QSFP28 generally operates at less than 3.5W. We checked with Screech and his friendly robot Kevin from Saved by the Bell, and they both assured us that 3.5 is less than 6.

This fight is starting to get ugly. But we have a feeling the CFP2 still has a few punches left in the tank.

Winner: QSFP28

CFP2 vs. QSFP28 Round 3: Channel function

The QSFP28 supports a 4-channel setup. Each lane is capable of carrying up to 28G Ethernet(4x28G).

But here’s where the CFP2 uses its larger size to its advantage. The CFP2 supports a 10-channel setup divided into 10G signals (10x10G). While that does mean it takes more connections to get to 100G, that versatility gives you more connectivity options, making it easier to mix and match your old and new equipment and create a best-of-breed solution.

Looks like this fight may not be an easy knockout afterall.

Winner: CFP2

CFP2 vs. QSFP28 Round 4: Cost

Every source we found stated that QSFP28 is the cheaper option. That led us to the next logical question: “Ok, but how much cheaper is it?” But we couldn’t find a definitive answer.

Some sources claimed QSFP28 was a little cheaper, some a lot, but none gave a specific figure. That’s probably because the cost difference will heavily depend on how you use the transceiver--in most applications, QSFP28 will be significantly cheaper, but as you try to pump it for more bandwidth and distance, the cost difference shrinks.

Winner: QSFP28

CFP2 vs. QSFP28 Round 5: Application

Speaking of upgrades, if you’re sitting on a wad of cash you can pump directly into a network-wide 100G boost, the QSFP28 will make it comparably easy to do so.

But if you had that much money, you’d probably be wolfing down macadamia nut cookies and pretending to like poi while lounging on a Hawaiian beach. More likely, you’re looking to upgrade your network in pieces, blending old and new architecture along the way.

And since there’s no magic switch that will take you directly from whatever you currently have to pure 100G, you’re probably going to continue to use slower bandwidth components in some parts of your network--perhaps for a long time to come.

That’s another area where the CFP2 has a slight edge over the QSFP28. Again, the QSFP28 only offers four channels, while the CFP2 has ten. That can make CFP2s more versatile and useful as the 100G “stepping stone” many parts of your network will likely require.

Winner: CFP2

CFP2 vs. QSFP28 Round 6: Distance

Like with form factor, this one is simply no contest. If you need long haul connections with low attenuation, the CFP2 is the obvious choice over the QSFP28.

That’s not to say the QSFP28 can’t offer some degree of long haul connectivity, though. The QSFP28 comes in two models: the aptly named short-range SR4 and the equally aptly named long-range LR4. The SR4 can maintain 100G up to 100 meters; the LR4 goes up to 10km.

But even the QSFP28-LR has nothing on the CFP2 when it comes to going the distance. CFP2 modules offer DWDM Coherent technology, enabling multi-channel connectivity of more than 1000km.

There’s a catch, though, because isn’t there always? Using CFP2 for these long haul connections can put serious power, size, and cost constraints on your network, and as such should probably be mixed and matched with other components--including, perhaps, some QSFP28s--for use in long distance connectivity.

Caveats aside, when looking solely at the numbers, CFP2 beats QSFP28 at low attenuation over long distance--10 times over.

Winner: CFP2

CFP2 vs. QSFP28 Overall Winner: Wait, it’s a draw?!

If we’re weighing each round equally, our contest ends in a 3-3 draw. But don’t start booing and demanding your money back just yet.

Let’s take a side-by-side look at both transceivers:


QSFP28 wins

CFP2 wins


Form factor



QSFP28 is 84% smaller

Power consumption



QSFP28: 3.5W

CFP2: 6W - 24W

Channel function



QSFP28: 4-channel

CFP2: 10-channel




QSFP28 is generally cheaper




QSFP28: 4-channel

CFP2: 10-channel




CFP2 goes 10X longer


So QSFP28 won in form factor, power consumption, and cost, while CFP2 won in channel function, application, and distance.

But let’s look at the margins of victory here--QSFP28 won form factor and power consumption in a landslide, and only narrowly lost out to CFP2 in channel function and application (which many could argue are basically the same thing.) Cost was hard to determine, and the only area where CFP2 won big was distance. And while it can go much further than QSFP28, CFP2 is not an ideal long haul solution on its own due to issues of power, size, and cost.

Also, the categories in which QSFP28 won are arguably more important than those won by CFP2. So if we abandoned our barely applicable and now seriously overplayed boxing analogy and took the time to apply some kind of “importance weight” to these rounds, the overall results would change.

Considering those factors, plus the fact that draws are stupid, we’re going to go ahead and make a judgment call.

Your winner, by way of split-decision:

The QSFP28!!

Ding ding, grab the mic, tell Adrian we did it, and head home.

(Unless you have long haul needs, then the CFP2 probably wins. Sometimes. See, we told you it was complicated.)

Get the best of both worlds with Terabit Systems

Something that isn’t complicated: The team at Terabit Systems specializes in providing quality refurbished networking equipment—as well as industry leading customer service— to clients worldwide. Our catalog features both CFP2 and QSFP28 transceivers and so much more.  Email us or call +1 (415) 230-4353 to speak to a Terabit representative for a quote today.



August 13, 2019