Wireless router -- which one?

Short version: What dual-band router has QoS to deal with "buffer bloat" problem? I think queuing algorithm is called "fq_codel" or something. Long version: My current router is Asus RT-N66U. I didn't have problem with stock firmware. But, after upgrading to the latest firmware this weekend, I'm experiencing "bufferbloat" problem. When I download a large file (eg. ISO file), I can't browse or send emails or anything, until the download is finished or terminated. Right now, I'm using my previous router TP-LINK TL-WDR4300 with DD-WRT. But, its 5GHz band is flaky, and it needs frequent reboot. The very reason why I replaced it in the first place. So, it's time for a new router. I'm looking at Asus or Linksys. Any recommendation based on what you have or what you've heard? -- William

| From: William Park via talk <talk@gtalug.org> | My current router is Asus RT-N66U. I didn't have problem with stock | firmware. But, after upgrading to the latest firmware this weekend, I'm | experiencing "bufferbloat" problem. When I download a large file (eg. | ISO file), I can't browse or send emails or anything, until the download | is finished or terminated. What does "latest firmware" mean? Which firmware? dd-wrt? Asus' own? I'm assuming that the bandwidth bottleneck is between your modem and your ISP. I guess your wireless LAN might have lower bandwidth than your broadband connection, but that doesn't happen often. I'm also assuming that you are just using a simple transport for the ISO, not bittorrent. I don't remember the details of how bufferbloat works, but it seems to me that the most obvious thing is that the problem is on the sending side, not receiving. That suggests that the buffering problem is on the other side of the wire from you. It's not impossible for your side to moderate the flow from upstream. It could delay ACKs. I don't remember that bufferbloat-avoiding code does that. | What dual-band router has QoS to deal with "buffer bloat" problem? | I think queuing algorithm is called "fq_codel" or something. I don't think the bufferbloat is related to QoS.

On 22/08/16 10:01 AM, D. Hugh Redelmeier via talk wrote:
| From: William Park via talk <talk@gtalug.org>
| My current router is Asus RT-N66U. I didn't have problem with stock | firmware. But, after upgrading to the latest firmware this weekend, I'm | experiencing "bufferbloat" problem. When I download a large file (eg. | ISO file), I can't browse or send emails or anything, until the download | is finished or terminated.
What does "latest firmware" mean? Which firmware? dd-wrt? Asus' own?
I'm assuming Asus, as he said it was originally stock. Bufferbloat happens where a slower link meets a faster one, and the symptoms are indeed insane latency when doing anything that has to pass through the same buffer as a bulk transfer. Any the XX-WRT router OSs will have a recent fq_codel, and the team (Dave Taht, and fiends) are working on similar problems in wi-fi. If the Asus router says it has fq_codel, check and see if you can move the bulk transfer to a wired interface. Ditto if you use DD-WRT and friends. Wi-fi is sorta "fe-fi-fo-fum, I smell the bloat of a bufferman" (;-)) --dave -- David Collier-Brown, | Always do right. This will gratify System Programmer and Author | some people and astonish the rest davecb@spamcop.net | -- Mark Twain

On 08/22/2016 01:37 PM, David Collier-Brown via talk wrote:
Bufferbloat happens where a slower link meets a faster one, and the symptoms are indeed insane latency when doing anything that has to pass through the same buffer as a bulk transfer.
TCP should detect the slow transfer and back down the transmit rate. When buffers overflow, they're supposed to drop packets.

On 22/08/16 02:05 PM, James Knott via talk wrote:
On 08/22/2016 01:37 PM, David Collier-Brown via talk wrote:
Bufferbloat happens where a slower link meets a faster one, and the symptoms are indeed insane latency when doing anything that has to pass through the same buffer as a bulk transfer. TCP should detect the slow transfer and back down the transmit rate. When buffers overflow, they're supposed to drop packets.
--- Talk Mailing List talk@gtalug.org https://gtalug.org/mailman/listinfo/talk
*We* know that, but people doing routers don't. They coded to never drop packets, and added massive buffering to support that. Net result? They broke TCP. --dave -- David Collier-Brown, | Always do right. This will gratify System Programmer and Author | some people and astonish the rest davecb@spamcop.net | -- Mark Twain

On 08/22/2016 02:49 PM, David Collier-Brown via talk wrote:
*We* know that, but people doing routers don't. They coded to never drop packets, and added massive buffering to support that. Net result? They broke TCP.
I have a good book "Computer Networks" by Andrew Tanenbaum and David Wtherall that describes what's supposed to happen. Perhaps those people writing the router software should invest in a copy or two. ;-)

| From: David Collier-Brown via talk <talk@gtalug.org> | On 22/08/16 02:05 PM, James Knott via talk wrote: | > On 08/22/2016 01:37 PM, David Collier-Brown via talk wrote: | > > Bufferbloat happens where a slower link meets a faster one, and the | > > symptoms are indeed insane latency when doing anything that has to | > > pass through the same buffer as a bulk transfer. | > TCP should detect the slow transfer and back down the transmit rate. Yeah. That should be detected by lack of timely ACKs. | > When buffers overflow, they're supposed to drop packets. | *We* know that, but people doing routers don't. They coded to never drop | packets, and added massive buffering to support that. Net result? They broke | TCP. Am I right that if the bottleneck is beyond his demark, and it the flow is predominantly inbound, code on his own router cannot affect the problem? Well, perverse code could: for example send ACKs for packets not yet seen.

On 08/22/2016 04:07 PM, D. Hugh Redelmeier via talk wrote:
Am I right that if the bottleneck is beyond his demark, and it the flow is predominantly inbound, code on his own router cannot affect the problem? Well, perverse code could: for example send ACKs for packets not yet seen.
I suppose, but where would the bottleneck be? His connection to the ISP is likely the slowest link, with his local LAN faster. Perhaps he should fire up Wireshark and take a look. Also, is it in fact "buffer bloat"? Or just a poorly performing router? Given replacing it cleared the problem, that's what I'd suspect. With Wireshark, he can look at all the traffic, examine the TCP details, watch for ACKs. etc.

| From: James Knott via talk <talk@gtalug.org> | Also, is it in fact "buffer bloat"? Or just a poorly performing | router? Given replacing it cleared the problem, that's what I'd suspect. That was where I was going. | With Wireshark, he can look at all the traffic, examine the TCP details, | watch for ACKs. etc. Yes. But lots of trees hide the forrest.

On Mon, Aug 22, 2016 at 10:01:37AM -0400, D. Hugh Redelmeier via talk wrote:
| From: William Park via talk <talk@gtalug.org>
| My current router is Asus RT-N66U. I didn't have problem with stock | firmware. But, after upgrading to the latest firmware this weekend, I'm | experiencing "bufferbloat" problem. When I download a large file (eg. | ISO file), I can't browse or send emails or anything, until the download | is finished or terminated.
What does "latest firmware" mean? Which firmware? dd-wrt? Asus' own?
I mean the vendor's firmware. -- William

On Sun, Aug 21, 2016 at 08:23:22PM -0400, William Park via talk wrote:
Short version:
What dual-band router has QoS to deal with "buffer bloat" problem? I think queuing algorithm is called "fq_codel" or something.
Long version:
My current router is Asus RT-N66U. I didn't have problem with stock firmware. But, after upgrading to the latest firmware this weekend, I'm experiencing "bufferbloat" problem. When I download a large file (eg. ISO file), I can't browse or send emails or anything, until the download is finished or terminated.
Right now, I'm using my previous router TP-LINK TL-WDR4300 with DD-WRT. But, its 5GHz band is flaky, and it needs frequent reboot. The very reason why I replaced it in the first place.
So, it's time for a new router. I'm looking at Asus or Linksys. Any recommendation based on what you have or what you've heard?
I am very happy with my WRT1900ACv2 (aka WRT1900ACS) running LEDE. Lots of ram, lots of CPU, decent ports on it, good amount of flash. -- Len Sorensen
participants (5)
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D. Hugh Redelmeier
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David Collier-Brown
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James Knott
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lsorense@csclub.uwaterloo.ca
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William Park