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I'm trying to diagnose some internet speed issues on my MacBook. It's happening everywhere I use the internet -- at home (Comcast), at work, at my favorite cigar store. (All are wireless.)

At first, when it was home, I thought it was my service, as my XBox 360 was also exhibiting some internet speed issues. I bounced the router, and the 360 was fine -- but the Mac was not. (Plus, once I got the machine to work and the cigar shop today, it's still exhibiting the behavior.)

The behavior itself is odd -- once a host seems to be found, speed is no longer an issue. (In other words, download speeds themselves are fine -- but getting the request to the server is the issue.)

My gut reaction is that I'm having a DNS issue.

Any troubleshooting advice?

EDIT

On the advice of Josh, I tried a Speakeasy test. Once the site resolved, the speed here at the cigar store was reliably 20+mbps up and 3+mbps down. I expect my home environment to be similar when I get back tonight. As stated above, the issue isn't the download speed itself -- it's the resolution. I may try Am1rr3zA's advice of setting my own DNS if this continues to be an issue. Still soliciting other ideas, however!

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if you think it's from your DNS set other DNS service provider for yourelf. like 4.2.2.4 or 4.2.2.3 – Am1rr3zA Sep 21 '09 at 23:04
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2 Answers

up vote 2 down vote accepted

What does a speed test from somewhere like speakeast.net say? Are the results consistent?

EDIT 1: If you think it's DNS, open the terminal and type: dig www.google.com (replacing www.google.com with the hostname to check. When the results come back look for the line: Query time: ** msec. What is the output?

EDIT 2: Since DNS doesn't seem to be the issue, how does raw HTTP seem to work? In the terminal, try:

HOST=www.google.com
time echo -e "GET / HTTP/1.1\nHOST: $HOST\n\n"|nc $HOST 80

and let's see how long that takes. (Obviously just change HOST= to the hostname to check)

FINAL EDIT: For other people having the same issue, see the comments. The issue turned out to be erroneous DNS servers listed in the network configuration.

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Consistently high -- once I finally make it to their site. :) – John Rudy Sep 21 '09 at 23:30
Try testing DNS speed, see my revised answer. – Josh Sep 21 '09 at 23:35
Now that was enlightening. Results I considered perfectly fine -- 25, 40 msecs. Odd since I'm still exhibiting the behavior in-browser. (And it's not just Firefox 3.5 -- I also see it in Safari, NetNewsWire and Nambu. Hmmm. I'd almost say browser add-on, but I have none for the WebKit-based stuff, and it's affected too ... ) – John Rudy Sep 22 '09 at 2:20
I am just troubleshooting bit by bit... please see EDIT 2... :-) – Josh Sep 22 '09 at 2:27
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You didn't quite hit the answer, but I'm giving you the accept for all the troubleshooting. Turns out it actually was DNS. I'd been signed into my work network all day Friday, and the DNS & search domains from there persisted. Being inaccessible anywhere else -- even the their wireless network, sans VPN -- they caused the issue. I noted their addresses & removed those two DNS servers and the search domain, and everything's back to normal! Thank you again for the help. For the next guy, can you mention to check the DNS page for errant servers, log and remove them and try? – John Rudy Sep 22 '09 at 12:01
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You might try disabling IPv6 if you have it enabled; some networks and routers still have various problems with it. The setting is in System Preferences » Network » Advanced » TCP/IP » Configure IPv6.

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Thanks for the advice, but no change. – John Rudy Sep 22 '09 at 11:43
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