Diagnosing intermittent connectivity problems

September 23, 2008 9:03 AM

I'm experiencing intermittent periods (several hours every couple of days) where web pages are extremely slow to load and/or hang while partially loaded. How do I figure out what's causing the problem and fix it, ideally without wasting a lot of time on the phone with my ISP?

Specs:
Mac OS X 10.4.11
Firefox 3.0.1 (Safari 3.1.2 and iTunes 8.0 are also affected)
Netgear mr814v2 wireless router with 64 bit WEP encryption
Motorola SB5120 cable modem
Comcast internet service

Thanks for any clues, Internet superfriends!

posted by ottereroticist to computers & internet (11 comments total)

One problem could be that cable internet is shared over multiple people across your node. Is there any pattern to the slowness? For instance, does it slow down around 5 or 6 pm when people get off from work?
posted by nitsuj at 9:17 AM on September 23, 2008

Run a traceroute when the problem is occurring to identify exactly where the delay is happening. You'll know then if it's your ISP, your router, etc.
posted by COD at 9:26 AM on September 23, 2008

COD, this is what I get when I run traceroute with the address of the cable modem as the argument (is that the right thing to do?):

traceroute to 192.168.100.1 (192.168.100.1), 64 hops max, 40 byte packets
1 192.168.100.1 (192.168.100.1) 10.502 ms 5.234 ms 9.012 ms

So what does that tell me?
posted by ottereroticist at 9:57 AM on September 23, 2008

You are better of doing an traceroute to google or your DNS server (Don't know how to get the IP of that under OSX) or to the website that you trying to access. You could also try to bypass the wireless, in case somebody nearby is on an wireless phone causing interference.
posted by Ferrari328 at 10:23 AM on September 23, 2008

I'm using Comcast in the North Shore / Boston MA area. I saw lots of similar slowdowns; they seemed to be from using Comcast's DNS (the default DNS). I switched to OpenDNS, which seems much faster- I don't have those same hiccups. DNS is what maps names to IP addresses; Comcast's DNS seems to get saturated and sporadically slows down. It's free, so if you are ok with the privacy issue (link below), it may be worth trying it out.

OpenDNS site (describes how to set up your machine to use it)

Wikipedia Article on Privacy Concerns (since they aggregate your DNS info and redirect bad links, there is a potential privacy issue that you should be aware of before using their service.)
posted by jenkinsEar at 10:25 AM on September 23, 2008

I see this problem all the time with people's Macs at home. It's most definitely a DNS issue. It is always solved by setting your DNS server to a known good DNS server, like 4.2.2.2. To do that, go to Apple menu>System Preferences>Network. Then select your Airport connection, click Configure, then look at the TCP/IP tab. Enter 4.2.2.2, hit enter, then enter 4.2.2.3 on the second line. Then click Apply Now. You may have to restart your web browser for the change to be evident.

I think this is less of a problem with a specific DNS provider and more of a problem with certain wireless routers' ability to properly share correct DNS information with Macs. I usually see this issue in houses where the wired computers or Windows machines have no problems, but the wireless Mac is painfully slow.
posted by MonsieurBon at 10:48 AM on September 23, 2008

Whoops, it should have read, "[Go to the DNS field,] enter 4.2.2.2, hit enter, then enter 4.2.2.3 on the second line."
posted by MonsieurBon at 10:49 AM on September 23, 2008

Hey, awesome! I tried OpenDNS and saw a marked and immediate improvement. Do you think I can get these same results by using 4.2.2.2 instead of OpenDNS? I don't love the ad-infested page OpenDNS shows you if you type a bad URL.
posted by ottereroticist at 10:55 AM on September 23, 2008

OpenDNS is fast because they do a lot of caching, and they have distributed servers around the world. This is pretty expensive, so that's why they have all those ads.

The 4.2.2.2 DNS service seems to be either GTE or Verizon; ISP DNS services tend to be pretty good (except for Comcast's), so you may get lucky- it partly depends on your network location. It's probably worth a shot.
posted by jenkinsEar at 11:19 AM on September 23, 2008

They also said "and/or hang while partially loaded."

I'm not super techie, but if the DNS server has already provided the route, how/why would it slow a partially loaded page ??

If it were a Windows setup I'd suggest bot infection. Computer slows as it and the rest of the network send a gazillion spam emails (to me). But macs are ok I think ?
posted by Xhris at 2:10 PM on September 23, 2008

@xhris- many sites are composed of an HTML file served from one server, while a content distribution network (like akamai) or static caching server provides the images, flash movies, and other rich content. Once the HTML arrives, the browser then has to look up the IP addresses of any other referenced sites within the page. This looks like a partial hang to the end user if the ISP's DNS servers are slow.

I'm usually reluctant to suggest malware on Macs or *Nix machines; the OS is designed better in this regard. Even Vista seems to be doing a much more credible job these days, now that UAC is kicking in.
posted by jenkinsEar at 8:53 PM on September 23, 2008