decimalator Posted January 17, 2015 Share Posted January 17, 2015 I just upgraded my Internet package with Comcast from the basic 25 Mbps up to their 105 Mbps, the fastest they offer in my area. As a part of that, I had them replace my modem as well. Shouldn't be an issue with the modem not supporting the higher speeds. Anyways, speedtest.net shows about 50-58 Mbps, so I was a bit perturbed. After awhile I called their support and they assured me I was set to 105 Mbps. I tried their speedtest.comcast.net interface and their IPv4 tests gave about the same response that speedtest.net did, about 57 Mbps. But then it ran an IPv6 test as well and I got 122 Mbps! I haven't tried bypassing the Netduma to see whether there is an impact there, I want to avoid my IP address changing -- I do a lot of consulting and it is a PITA to have to request access to client systems every time my IP address changes. I found this, which seems to describe the issue I'm having. While it seems to be an issue with Comcast specifically, if manually mangling the packets to adjust DSCP values works around the problem, it would be great if there were an option for this hidden away somewhere in the WAN settings. Comcast is one of the major US ISPs, although it will probably only affect users with > 50 Mbps service. http://forums.comcast.com/t5/Home-Networking-Router-WiFi/IPv4-Traffic-Slow-Native-IPv6-Full-Speed/td-p/1822405 Link to comment Share on other sites More sharing options...
Guest Netduma_Iain Posted January 17, 2015 Share Posted January 17, 2015 This is FASCINATING we've seen some really weird things go on recently with some customers. To the point I was 99% sure the ISP was doing some weird throttling, but diff serve makes total sense. This is very simple to do, but I think I'll have to speak to our lawyer first. I'm almost sure its fine because the EULA says we can't be help responsible for costs incurreced. But basically the issue with messing with stuff like that is the ISP could charge different rates for different services. So if a user changes it they could have a hefty bill at the end of the month. Obivously we don't want to be responsible for that. For my own personal use: Yevgeniy: I ran into your blog post "Got slow download but fast upload speeds over wireless? Here's a fix." I have some info you may find useful. This happened to me too when I moved to Comcast - but I had DSL running in parallel. The Comcast traffic had this problem but the DSL did not. Also, it affected my Linksys router when it had stock firmware *and* after switching to DD-WRT. Clearly the traffic itself was at issue, so I broke out the packet sniffer. *All* inbound Comcast traffic (Internet --> client) was tagged with a DSCP value of 8 (Class Selector 1). The DSL traffic had a DSCP value of 0. So Comcast is tagging all traffic to be treated a certain way by QoS: "Priority," which sounds good but is actually the second-*lowest* possible. WMM, itself a QoS technique, apparently de-prioritizes (drops?) based on the Comcast-supplied value. Turning off WMM worked around it - but since WMM is part of the 802.11n spec, I wanted root cause. Judiciously replacing that set-by-Comcast DSCP value does the trick. So between my Linksys router and both ISPs, I had a Netscreen firewall. It lets me set DSCP values by policy - so I told it to match the DSL (DSCP 0). This yielded great improvement. However, I was still not getting full speed so even a zero value was not the best for > DSL rates. I set the DSCP value to 46 (Expedited Forwarding) and bingo, up to 20Mbps, almost full provisioned speed (25Mbps). Why only download issues? Because the only Comcast-tagged packets are the inbound ones: Internet --> you, including those big data packets. When uploading, yes, you get sent ACK packets and such - but they are tiny connection-control packets. I imagine WWM weirds out on them too, but you (usually) wouldn't notice when doing multi-Mbps speed tests. I am still trying to udnerstand WMM, but this was a big find, and I was lucky to have a firewall that let me packet-tweak. Hope you find the info useful. Link to comment Share on other sites More sharing options...
Evandadda Posted January 17, 2015 Share Posted January 17, 2015 I just upgraded my Internet package with Comcast from the basic 25 Mbps up to their 105 Mbps, the fastest they offer in my area. As a part of that, I had them replace my modem as well. Shouldn't be an issue with the modem not supporting the higher speeds. Anyways, speedtest.net shows about 50-58 Mbps, so I was a bit perturbed. After awhile I called their support and they assured me I was set to 105 Mbps. I tried their speedtest.comcast.net interface and their IPv4 tests gave about the same response that speedtest.net did, about 57 Mbps. But then it ran an IPv6 test as well and I got 122 Mbps! I haven't tried bypassing the Netduma to see whether there is an impact there, I want to avoid my IP address changing -- I do a lot of consulting and it is a PITA to have to request access to client systems every time my IP address changes. I found this, which seems to describe the issue I'm having. While it seems to be an issue with Comcast specifically, if manually mangling the packets to adjust DSCP values works around the problem, it would be great if there were an option for this hidden away somewhere in the WAN settings. Comcast is one of the major US ISPs, although it will probably only affect users with > 50 Mbps service. http://forums.comcast.com/t5/Home-Networking-Router-WiFi/IPv4-Traffic-Slow-Native-IPv6-Full-Speed/td-p/1822405 Curious which modem did they issue you? I have the Comcast branded Arris TG862G. I'm in the DC area with Comcast Xfinity and have the upgraded speed as well. Last speedtest I had 180 down/40 up on IPv4. Just received my Netduma this morning so I havent had a chance to install on my network. Link to comment Share on other sites More sharing options...
Guest Netduma_Iain Posted January 17, 2015 Share Posted January 17, 2015 Thanks for purchasing Evandadda! Hope you love it, let us know how you get on please Link to comment Share on other sites More sharing options...
Evandadda Posted January 17, 2015 Share Posted January 17, 2015 Thanks Iain. Looking forward to setting it up tonight and will provide my feedback Link to comment Share on other sites More sharing options...
decimalator Posted January 22, 2015 Author Share Posted January 22, 2015 Curious which modem did they issue you? I have the Comcast branded Arris TG862G. I'm in the DC area with Comcast Xfinity and have the upgraded speed as well. Last speedtest I had 180 down/40 up on IPv4. Just received my Netduma this morning so I havent had a chance to install on my network. I think it was the TG862G as well. Regular speedtest.net shows just IPv4 speeds, which are about 55-57 / 10-12. comcast.speedtest.net shows both IPv4 and IPv6 speeds, which IPv6 being about 120-125 / 10-12. Any updates on whether a toggle for adjusting DSCP values is feasible? Or access to login and set it myself without your knowledge or consent? ;-) Link to comment Share on other sites More sharing options...
Guest Netduma_Iain Posted January 22, 2015 Share Posted January 22, 2015 Decimalator it will not be accessible in next release(hopefully tomorrow). Grab me when I have sometime free and I'll do it for your router alone after I've released .7 Link to comment Share on other sites More sharing options...
iAmMoDBoX Posted January 23, 2015 Share Posted January 23, 2015 Decimalator it will not be accessible in next release(hopefully tomorrow). Grab me when I have sometime free and I'll do it for your router alone after I've released .7 I have comcast as well, do you think that could be the same problem I'm having with wonky speeds? Link to comment Share on other sites More sharing options...
Guest Netduma_Iain Posted January 23, 2015 Share Posted January 23, 2015 Not sure mate will need to look into it Link to comment Share on other sites More sharing options...
mr.victor Posted January 27, 2015 Share Posted January 27, 2015 Wow, I just read this topic and tried for myself since I also have comcast. My results were on IPV4: 60down 20up. IPV6 was 120 down, 20up. Looks like i'm in the same boat. Link to comment Share on other sites More sharing options...
decimalator Posted January 27, 2015 Author Share Posted January 27, 2015 Wow, I just read this topic and tried for myself since I also have comcast. My results were on IPV4: 60down 20up. IPV6 was 120 down, 20up. Looks like i'm in the same boat. I think it will be pretty common once more of us Yankees start jumping onboard, as Comcast is the largest ISP over here. It will only get bigger if their deal to buy Time Warner Cable goes through. Iain, I'm available any evening from about 8pm Pacific time until about midnight Pacific time if you want to use me as a guinea pig for testing manipulating DSCP. @decimalator on Twitter is probably the easiest way to get ahold of me Link to comment Share on other sites More sharing options...
Guest Netduma_Iain Posted January 28, 2015 Share Posted January 28, 2015 Hi mate, just going to release .7 soon. Then I'd love to give it a go. Like I said its not very difficult at all, we're talking 5 lines of code I reckon. Link to comment Share on other sites More sharing options...
Marvin Posted January 28, 2015 Share Posted January 28, 2015 Hi mate, just going to release .7 soon. Then I'd love to give it a go. Like I said its not very difficult at all, we're talking 5 lines of code I reckon. I would like to get in on this once you have something ready to go, please. Link to comment Share on other sites More sharing options...
A7Legit Posted January 28, 2015 Share Posted January 28, 2015 Adjusting DSCP values sounds like a nice option to have in .8... Link to comment Share on other sites More sharing options...
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