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| Intermittent Speed/Latency/Connectivity issues Hello everyone,
I've been browsing the forum for a few days now - what a wealth of information! I thought I'd share my situation and see if anybody can offer some insight. First, some background.
This all started around the beginning of January. My Motorola SB5101 modem was disconnecting a few times a day. I called Comcast, who checked my signal levels, said it was probably a bad modem.
I replace my SB5101 with a Linksys CM100. Problem continues. Comcast dispatches a tech. Tech arrives, checks line levels, all are in spec. He was very professional and explained that my area was in the midst of a DOCSIS 3 rollout. He also claimed that nobody in management was acknowledging the issue, but he's seeing alot of connection issues with his recent service calls. A few weeks later, this irons out. I switch back to the SB5101 modem, in hopes of returning the CM100.
The dropped connection issues are no longer occurring, however, I seem to be having some weird latency/speed issues. I'm posting both because I'm not sure if they may be related. Transfer speeds are excellent and consistent, no complaints there. However, page loads are awful. It will sometimes take 20-30 seconds just to load a page on Google news. Other times, less than a second. Firefox shows "Waiting for site.com" (with whatever site is being accessed at the time) This is not site-specific. The FAQ indicates this may be a DNS issue, so I tried some different DNS servers, but none resolve, or even help, the problem. This issue can also be observed on a site with lots of pictures, say a gallery on webshots. The entire site loads in a few seconds, except a few thumbnails, which load 20-30 seconds after the rest of the page, or time out and display broken images. If this were a DNS issue, wouldn't the IP for the site already be resolved and cached? Similarly, I could be browsing a site, one page loads quickly, the next page on the same site takes 30+ seconds, or even times out.
This issue occurs on multiple computers, multiple browsers, and even multiple operating systems, so I don't think it's specific to any of them.
I have tried swapping routers, and tried running directly to the computer from the cable modem, but did not notice any difference.
I have tried describing the issues to Comcast tech support, and while they have definitely made efforts to be helpful, I don't think they understand the issue. Most of the phone techs check signal levels and run a line quality test, which usually come back fine. Beyond that, they don't often have further suggestions aside from sending out another tech.
Below, smokeping indicates some packet loss - perhaps this is useful information?
Below is the information requested by the site:
1) Your location: City and State
Downingtown, PA
2) A description of the problem.
See above.
3) Is the issue intermittent, constant or does it occur at a specific time of day?
Intermittent, does not occur at any specific time.
4) Your modem make, model & firmware version.
Motorola SB5101
Software Version: SB5101N-2.7.2.0-GA-00-NOSH
Hardware Version: 1
MIB Version: II
GUI Version: 1.0
Config file d11_m_sb5101_silverpboost_c01.cm
I have also experienced the same issues with a Linksys CM100. I have a second SB5101 brand new in the box I can try if anybody thinks it worthwhile.
5) Describe any home networking if applicable. (i.e. routers, hubs, adapters, etc.)
Linksys WRT54GL v1.1 router running Tomato firmware. I have also tried a Linksys WRT54G running DD-WRT and stock firmware. I have also tried running CAT-5 directly from the modem to the computer.
6) List any firewall and/or anti-virus software you have installed. Include what version you have.
Varies depending on computer. On my PC, Symantec Corporate 10.1.7.7000 through my college.
Speed test results from a few days ago using Firefox 3:
»www.speedtest.net/result/404715117.png
Modem Signal Levels:
Downstream Value
Frequency 717000000 Hz
Signal To Noise Ratio 37.8 dB
Power Level -3.4 dBmV
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
Upstream Value
Channel ID 5
Frequency 34200000 Hz
Power 48.4 dBmV
Modem Log Entries:
Nothing of interest aside from:
Started Unicast Maintenance Ranging - No Response received - T3 time-out
Occurs every 3 days or so, but I understand this may be normal.
Cables and Splitters:
There is about 50ft of RG-6 with a messenger wire running from the pole to the grouding block. Another 50 ft. length of RG-6 runs from the grounding block to the cable entry point. There's a 5-6 ft length of RG-59 which goes trough the basement wall. That's all Comcast's wiring. Then starts my wiring. From there, there is a 1Ghz splitter. From the splitter to the cable modem is about 30ft of RG-6Q (quad shield)
• Post a trace route to the server you're having issues with. Use PingPlotter for the best results.
The issue is not site-specific, so I'm not sure this would be helpful. If it is, let me know.
• Smokeping results:
I have copied them to my website, as it seemed they are only stored on dslreports for a limited time
»www.yyonline.org/misc/CA1_last_10800.png
»www.yyonline.org/misc/CA1_last_108000.png
»www.yyonline.org/misc/CA2_last_10800.png
»www.yyonline.org/misc/CA2_last_108000.png
»www.yyonline.org/misc/NY_last_10800.png
»www.yyonline.org/misc/NY_last_108000.png
»/r3/smokeping.···9c6eb714
• Line quality test:
»/linequality/nil/2487358
I wasn't sure what info might be useful, so I tried to post everything I could. I'm a software developer, so I'm very well-versed when it comes to computers in general, but advanced networking is a bit over my head. I'd really appreciate any insight you might be able to share here. We've had comcast for about 7 years now, and this is the first time I've ever found their service less than reliable. I'm hoping someone can point me in the right direction. | |
| An update -
Turns out this was DNS related. Comcast assigns 3 DNS servers. Turns out the first one was really slow resolving names. If I manually enter the second as the DNS, pages loads fly. Pages that were taking 20-30 seconds to load now load in 3! I really noticed this on news sites, where many names get resolved. Seems some news sites have different servers for text, images, comments, etc. (ie, images.site.com, comments.site.com, etc.) Throw a few banner ads in the mix, and that's alot of names to resolve.
I thought this wasn't a DNS issue, as I tried using OpenDNS for a few days. For me at least, it seems OpenDNS wasn't any faster than the original Comcast DNS.
So...Two questions remain.
First, Is there any good way to tell Comcast one of their DNS servers is slowing down page loads? Techs seem to get annoyed when people call in "knowing" what the problem is. I can relate to this, as I work in tech support for a living. Still, if there is an issue, it should be fixed.
Second, regarding the smokeping tests... I'm in PA, so the NY test rarely shows any loss. The CA test shows some occasional packet loss. Does anybody know if a small amount of packet loss is normal or acceptable with the smokeping tests? | |
 ThrowDemsOutIf you can't convince 'em, confuse 'emPremium
join:2002-03-03
Mullica Hill, NJ
kudos:4
1 edit | I've seen occasional issues recently. Slow DNS to both some Comcast DNS servers and OpenDns server. And some web sites slow down at different times, including dslreports.
I ran thru many different diagnostics and tools and came to the conclusion that Comcast is experiencing congestion in some routers on some paths on a sporadic basis. Whether this is related to their maintenance work as they rollout Docsis 3 or not is the question I would have. But it is possible that as they modify their systems they are experiencing congestion on some paths thru the internet.
I didn't bother pursuing this through Comcast Support because you can never get to the real network engineers that can discuss and solve these types of problems. Level 1 & 2 CSRs just can't do anything but open a ticket and then you never hear what solved or didn't solve a problem.
I will say that the last 2 days have been slowdown free and all we can do is hope for the best as system wide changes are being done.
P.S.>> here is a Q&A and some code put together by someone here at dslreports that can test DNS lookup delays to multiple DNS servers at 1 shot:
»SBC DSL FAQ »How do I test DNS lookup latency with ns_bench?
--
My BLOG .. .. Internet News .. .. My Web Page | |
| reply to yyonline
I'm having the SAME exact problem.
So how do I go about changing my DNS? And which address?
I live in Chicago, btw. | |
| reply to yyonline
Hi, I'm in Chicago as well experiencing the exact same issues described by yyonline. Downloads and gaming have no problems, it's just the web browsing waiting to resolve host thing. As yyonline said, it doesn't matter the browser, OS, time of day, or website. It just randomly does it. Its been happening for the past few days. At first I would just reboot the router and modem and it would go back to normal. But just yesterday I tried that again and ended up having to re-configure my router settings over the phone with Belkin just to get back online hah =p
So is it for sure the DNS stuff that will solve this problem? If so some instructions on how to do this would be GREATLY APPRECIATED! Thanks. | |
 koitsuPremium,MVM
join:2002-07-16
Mountain View, CA
kudos:13 | reply to yyonline
said by yyonline:Second, regarding the smokeping tests... I'm in PA, so the NY test rarely shows any loss. The CA test shows some occasional packet loss. Does anybody know if a small amount of packet loss is normal or acceptable with the smokeping tests? Whatever that tool is (smokeping), it's horrendous. The graphs tell me very little, and are nearly impossible to read (I love all the blurring, and it isn't image compression since you're using PNG). I don't know how you put up with that.
To answer your question: "it depends". I don't know how smokeping works, so I don't know if it's similar in methodology to that of WinMTR, mtr, or traceroute.
If the tool attempts to send a packet (of any type; TCP, UDP, or ICMP) to a router at each hop between you and the destination, then yes, some of those hops are very likely to show packet loss due to ICMP de-prioritisation. This does not mean the packet you sent the destination is being dropped or de-prioritised -- only the individual hops (to routers) along the way. This is completely normal in this day and age, which is sad, because it makes troubleshooting a pain in the rear; I cannot tell you how many times I've had to argue with peering providers when they try to use the ICMP de-prio excuse at incorrect/inappropriate times.
If smokeping simply sends an ICMP packet to the destination (e.g. does not operate like WinMTR, mtr, or traceroute), and you're seeing packet loss there, then that also "could" be normal -- some IP stacks of servers will discard excessive numbers of ICMP packets if received, others can be configured to drop a certain percentage of traffic of any type (ICMP is common).
Honestly, it would be much more beneficial if you could use a tool like PingPlotter (which requires some configuration changes to be effective) or WinMTR and see if there's an increase in packet loss at a specific hop that "trickles down" through further hops.
Miscellaneous:
Your modem signal levels look okay, except for your upstream power, which is a little on the high side.
"Started Unicast Maintenance Ranging - No Response received - T3 time-out" messages that recur are normal. Most of us see this sort of thing regularly. If you see FEC framing loss, or "broadcast maintenance" messages, those will indicate loss of frame (cable sync loss).
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer. | | |
|
marcy
join:2009-02-11
Burbank, IL | reply to yyonline
nintendonick
comcosttoomuch
I am in the area too,
install PingPlotter and share your graphs
BTW
2morrow I will have a tech. guy at house... I will see if it helped my problem
| |
 NyQuil Kid8f The Nyquil Kid
join:2001-01-06
Brick, NJ | reply to yyonline
Count me in as well - Brick NJ area. HTTP requests are very slow to resolve; I too attempted to use OpenDNS and didn't really work well. While I am unfamiliar with the terminology, I think the issue is only with http traffic - not sure if FTP/BitTorrent/etc protocols are being impacted.
[8F] The NyQuil Kid
--
[8F] The NyQuil Kid comes into town not looking for trouble...n00bz gang up, but he ain't seein' double,...pulls and draws, his deagles two...n00bz litter the ground you know it's true. | |
| reply to marcy
@marcy, Is this what you are talking about? Never used this program before so I'm not quite sure what to do. | |
koitsuPremium,MVM
join:2002-07-16
Mountain View, CA
kudos:13 | reply to yyonline
With regards to PingPlotter, you need to change the following configuration items for the tool to become more useful:
Main screen, bottom left:
- Change "Trace Interval" from 15 seconds to 1 second
- Change "Samples to include" from 10 to 0 (which will appear as "All")
Main screen, section bar area (where Hop, PL%, IP, etc. are shown):
- Right click and choose Customise View...
- Enable "Err", "Min", "Max"
Optional:
Main screen, "Edit" menu, "Options...", "Packet" sub-menu
- Change "Packet Type" to "UDP Packets" or "TCP Packets"
(I can explain the circumstances why you would want to change this, but the important part people need to know is that all this does is change the outbound packet to the destination that induces ICMP-based responses (which is how the hop list gets created) -- just realise that this will not alleviate ICMP de-prioritisation on routers -- but it might allow you to actually reach the final hop)
Other things to be aware of:
- You can also right-click on the graphs (at the bottom) and change the duration view (how much probe data to show)
- You can right-click on a hop and choose "Show this timeline graph" to graph it at the bottom of the page
With this setup, let the tool run for about 30-40 minutes if possible, especially during the time you're seeing the problem. Then post a screen shot. 
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer. | |
koitsuPremium,MVM
join:2002-07-16
Mountain View, CA
kudos:13 | reply to comcosttoomuch
said by comcosttoomuch :
@marcy, Is this what you are talking about? Never used this program before so I'm not quite sure what to do.
Just noting this here: the packet loss you see a hop #11 is completely normal. That is router ICMP de-prioritisation as I described.
If that packet loss "trickled down" through hops #12 onwards, that would be an indication of the router at hop #11 having an issue (or a physical network interface on the router having a problem, cable/fibre cut, etc...) | |
marcy
join:2009-02-11
Burbank, IL | reply to yyonline
create few tags for tracing like google.com yahoo.com etc
and change Graph time = .... you have here 60seconds let us see at least 30 mins | |
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