Slow Internet Speed with TC Gen 5 and Time Warner Modem

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Slow Internet Speed with TC Gen 5 and Time Warner Modem

I am using the 3TB Gen 5 Time Capsule and Time Warner Cable Modem. Recently TWC increased the internet download speed to 300 Mbps. Using the TWC Speed Test I am getting around 95 not only when using TWC Wi-Fi but also when my iMac is connected to the TC directly over ethernet. I do get close to 300 Mbps when TWC Modem is connected directly to iMac over ethernet. I'm surprised that the WI-Fi speed is around one third, but more surprised that the speed is also one-third when connected over ethernet. I don't understand how the TC and TWC modem work together. My use of the TC Wi-Fi rather then TWC Modem Wi-Fi was recommended by Apple Support when they helped me set up the TC about six months ago. I'm not sure what I should be expecting. TWC replaced the cable Modem so that isn't the culprit. TWC also said to achieve the 300 speed the Modem needs to be connected directly over ethernet to the computer. There may be a configuration issue or lack of understanding on my part. Any help in sorting this out would be appreciated.

iMac (Retina 4K, 21.5-inch, Late 2015), OS X El Capitan (10.11.4)

Posted on Apr 28, 2016 1:29 PM

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Answer 1

i2 Author

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105 points

Apr 28, 2016 1:32 PM in response to i2

correction: Using the TWC Speed Test I am getting around 95 not only when using TC Wi-Fi but also when my iMac is connected to the TC directly over ethernet.

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Answer 2

Apr 28, 2016 4:51 PM in response to i2

It sounds like the TC WAN port is running slow. This is not unusual issue.

Apple have removed all the functionality from airport utility and command line in El Capo to help us diagnose the problem.

Do you have a computer running older OS or even windows?? Using the older utility will give more info.

What modem do you have from TWC??

Is the TC working as router?

Do you know if your area is IPv6? If so you really must use it to get the best speed.

IPv6 setup follow this instruction sheet.. which is for comcast but also works (so I have been told for TWC).

http://mydeviceinfo.xfinity.com/download.php?file_id=35

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Answer 3

i2 Author

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Apr 28, 2016 5:57 PM in response to LaPastenague

LaPastenague, thanks for your response. I am using a late 2015 iMac (21.5”, 4K Retina) running El Capitan 10.11.4. The Time Warner modem is an Ariss TG1672GF2.

The TC is running as a router and is set up as follows-

iPv6:Link-local only

Router Mode: Off (Bridge Mode)

The TC was configured this way by Apple Tech Support when the iMac would not connect to Time Machine although the Wi-Fi and internet operation were normal. So maybe this fixed the Time Machine connection problem but was not ideal for the best internet speed? I didn’t check any of this at the time when the Time Warner internet speed was only 50 Mbps.

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Answer 4

Apr 28, 2016 6:52 PM in response to i2

The TC is running as a router and is set up as follows-

iPv6:Link-local only

Router Mode: Off (Bridge Mode)

Just a quick note to mention that I'm sure that LaPastenague is going to point out that despite what you might think........the TC is NOT running as a router......since the "Off" in Bridge Mode means that routing is turned "Off".

IF....the TC were running as a router....the Router Mode setting would be DHCP and NAT.

But, don't change that, since you will have a Double NAT error if you do.

Wait for more instructions from LaPastenague.

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Answer 5

Apr 28, 2016 7:15 PM in response to Bob Timmons

As Bob says.. bridge on the TC, means the main modem is also your router.

Please login to your arris and turn on its wireless and check the speed direct from the arris.

Let me also suggest you plug the cable from the ARRIS modem to the LAN port of the TC instead of WAN.. in bridge that will work better in many cases than using the WAN port.. at least then plugged in by ethernet to the TC and wireless off the iMac should get full speed.. if not something is major wrong with the TC.

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Answer 6

i2 Author

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105 points

Apr 30, 2016 11:02 AM in response to LaPastenague

I tried your suggestion plugging the Modem into the TC LAN port instead of the WAN port but got the same result. I also ran several comparison tests. I found that a direct Enet connection to the iMac from the Arris modem achieves approx 350Mbps BUT only 94 from the TC. This was a surprising result. Wi-Fi direct from Arris and TC is around 94 when both are running in 2.4GHz band. In the 5GHz band the Arris and TC were generally the same around 94.

Any idea why the direct connect to the iMac speed is so different between the Arris and the TC?

Is such a large speed drop from 350Mbps on Arris modem Enet to 94 on Wi-Fi to be expected? I know there are a lot of factors influencing the network speed but I’m not sure where to look next or should I just live with a direct connect from the Arris modem to the iMac. In practical terms the Time Warner internet speed boost to 300Mbps actually increased my speed from around 40 to 94 which is an improvement.

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Answer 7

Apr 30, 2016 2:31 PM in response to i2

Something is very wrong if the speed drops so much.. there is no good reason I can see for the ethernet speed to be so low on the TC.

Please do some screenshots and post them.. I need to see the whole setup of the TC.

So I need the summary and at least the Internet, wireless and network tab from the TC.

In bridge mode and with the arris router connected to a LAN port the TC is effectively working as a switch.. to drop the speed so much suggests faulty ethernet cables. Or the actual switch in the TC is faulty which would be unusual.

I want you do do the testing with new short patch cables.. Cat6 grade. (2 or 3M max length).

You might need to move everything together.

You will not have noticed a bad cable before but once you exceed 100mbit you need proper gigabit cables.

Wireless is always a different kind of problem.

Again I need you to post your screenshots so I can actually see what your wireless link speed is like.

Hold the option key and click on the wireless fan.. that will give me the info about the wireless link..

I finally have a computer that can link at full speed wireless from AC airport.

As you can see my link speed is 1053Mbps.. you need somewhere around that kind of link to get actual throughput of 300mbps real world.

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Answer 8

i2 Author

Level 1

105 points

May 3, 2016 4:51 AM in response to LaPastenague

You are spot-on about a bad cable. I changed the cable from the Arris modem to TC to a CAT 6 (only had a 30 ft cable but will get a short one) and speeds improved to between 220 and 350Mbps (from 95) with direct enet from TC to iMac connection. WiFi speeds are much better but I'm not sure if further improvements are possible. I am doing more testing and also working on screenshots and will pass them on in the next few days. I turned off the Arris WiFi radios thinking they may be causing interference with TC WiFi but didn't see much difference.

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Answer 9

May 3, 2016 1:31 PM in response to i2

Great to hear..

It is most frustrating when apple have removed all the required info from the airport utility to actually discover the cause of these issues.. in a normal router GUI it takes a few seconds to see the link speed on an ethernet port.. and it would even show by different color on the LED. Simplicity is fine but when things fail.. having full diagnostic info is essential to track down the fault.

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Answer 10

i2 Author

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105 points

May 6, 2016 3:33 PM in response to LaPastenague

Results with 3 foot CAT 6 cable between Arris modem and TC LAN or WAN port is same as I reported in previous post. Speed varies by time of day and test server (Speakeasy) but typically190-220MBps on automatic 2.4GHz/5GHz dual channels and 200-250MBps on 5GHz channel. I hope these are the screenshots you requested.

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Answer 11

May 6, 2016 3:48 PM in response to i2

The short cable is just for convenience .. but a long standard and working properly Cat6 cable of 30 or 300 feet is no different to one of 3 feet.

Your screenshots are great.

Using AC wireless you have a speed of 585Mbps so you should achieve near enough to 300Mbps over wireless with that all things running well.. although it can drop to much lower speed under actual transfer conditions.

Your connection to 2.4ghz is 195Mbps and it is impossible to do better than 100Mbps over that connection.. that is why you need to force the connection to 5ghz.

The link speed is always halved due to wireless being half-duplex.. and actual throughput then depends on lots of factors and can easily halve again.. on a bad day.

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Answer 12

i2 Author

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105 points

May 6, 2016 3:53 PM in response to LaPastenague

Thanks for helping me understand this (a least a little...). And the CAT 6 cable allowed a considerable speed increase.

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Answer 13

i2 Author

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105 points

May 8, 2016 9:15 AM in response to LaPastenague

I have the Odyssey 5GHz channel only and the Odyssey dual band enabled. But when I select 5GHz only WiFi it chooses 802.11.ac and then restart the iMac, dual band WiFi Odyssey is used with 2.4GHz 802.11n mode. I really don't understand why this happens. I thought I was forcing the 5GHz band. Also why doesn't the dual band automatically go to 5GHz 802.11ac not 2.4GHz 802.11.n where the Tx Rate is better.

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Answer 14

May 8, 2016 1:35 PM in response to i2

Also why doesn't the dual band automatically go to 5GHz 802.11ac not 2.4GHz 802.11.n where the Tx Rate is better.

Signal is the design winner.. wifi connects to the stronger signal not the best data rate.

Your naming has to be different..

Did you go to wireless options and change the name of 5ghz.. if not please do that.. Include the 5ghz in the name.. call it Odd5ghz

Then you can select it and never lose it. Otherwise it is just standard dual band.

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Answer 15

i2 Author

Level 1

105 points

May 8, 2016 6:31 PM in response to LaPastenague

I first tried to just add hyphen between "Odyssey" and "5GHz" to change the name, but after a restart the dual band came back. Then *** you suggested I changed it to something that didn't contain the text "Odyssey" and it was retained. This is curios since the software must be looking for text that contains any string matching the dual band name Odyssey. So all is well and I thank you again for helping me set up and understand (somewhat) the WiFi configuration needed for the increased speed that Time Warner now provides. I don't expect many Mac users with Time Capsules are able to take advantage of this because Time Warner doesn't explain how to configure the TC. They expect customers to use the Arris modem for WiFi.

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