Comcast Upgrades Gigabit Pro from 3Gbps to 6Gbps!

Seems like I just wrote one of these articles, doesn’t it? It was only back in September 2021 when my Gigabit Pro connection received an upgrade from 2Gbps to 3Gbps, now, Comcast has officially bumped all Gigabit Pro customers up to 6Gbps!

Once I began hearing more rumors on Reddit, I investigated and found that Comcast’s support articles had been quietly upgraded to indicate that all Gigabit Pro customers would receive an upgrade to 6Gbps.

Since late last year, I have enjoyed speeds of “3Gbps+1Gbps” on my two handoffs. The service provides a 2Gbps fiber hand-off (10G fiber, rate limited to 3G), and a 1Gbps ethernet hand-off. Both circuits were able to be used simultaneously, as I demonstrated briefly at the end of my installation article.

With the upgrade in place, I now seem to have a “6Gbps+1Gbps” symmetrical service!

It’s genuinely hard to find a speedtest.net server that can do this connection justice. This test was run to Comcast’s own speedtest server.

I wanted to see if the 10% over-provisioning typical of Comcast’s fiber in the past was still in effect, speedtest.net seemed to top out for me at around 6200Mbps, but I was occasionally seeing some higher numbers on my router.

I set out to test the connection more thoroughly, which was not an easy task. I used multi-gig servers from 4 different datacenter locations to complete some iperf tests.

I was having some trouble getting the inbound and outbound maxed out at the same time, so for the sake of the most accurate test of “what is the rate limiting set to?”, I decided to test both directions of traffic flow separately.

Transmitting at full speed on both lines does indicate a 10% over-provisioning, and the ability to use both uplinks simultaneously for a total throughput of around 7Gbps.
Throughput during the test is a bit inconsistent, but this is likely just due to how difficult this test is to run. A lot of factors on the outside Internet make achieving this speed all the time difficult.
Receiving at full speed on both lines also works as expected, although for me, the receive test was a bit less consistent and harder to keep the bandwidth at expected levels. This is again most likely due to external factors, not how Comcast is rate limiting the connection.
You can see here that throughput during this test is a lot more inconsistent, even on the gigabit uplink, which is likely indicating some congestion coming from my test servers more than anything else.

Interestingly, in the tests you can see that the upload (TX) test was much more stable and consistent than the download (RX) test. It’s difficult to say for sure where the fluctuations are coming from, but the servers I was testing with or the networks they are connected to may have some capacity constraints. Datacenter traffic tends to be heavy outbound, so there is likely more free available inbound bandwidth at datacenters (for me to transmit to them), resulting in a smoother test.

I may re-conduct these tests again in the future if I gain access to faster servers to test with. For the time being, the results are still very impressive, and I have to comment Comcast for pushing the envelope with this, even though I suspect the only reason they did it is to give a petty jab at AT&T who just rolled out a 5Gbps residential fiber plan themselves.

In any case, I look forward to never maxing this connection out except when trying to stress test and speed test! 😉 Even the 3Gbps connection was basically impossible to fully utilize given the limitations of the servers you’re connecting to.

6Gbps is even pushing the limitations of a lot of common computer hardware (like SATA III disk drives which have a 6Gbps interface speed). It’s crazy to think that my Internet connection is capable of transferring data faster than most consumers currently are able to read\write data to a SATA SSD.

It will definitely be a long time before these speeds are needed by any residential customer, but I’m still quite pleased to have them now!

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