DSL connection spotty and slow after security update

Question

I updated both the latest security patch and firmware for my Intel Mac Mini a few days ago, and since then have had notably slower DSL internet service. Frequent time-outs in locating servers etc. Skype connection is much much worse than before the update(s).
Anyone have similar experience and/or suggestions?
Mac Mini 1.66 Intel Core Duo   Mac OS X (10.4.8)  

Answer 1

There are two distinct problems that can occur with internet connections, giving two different symptoms.
If, for example, you click on a link or enter a URL in a browser and it takes ages to start the process of loading the page, but once started it loads reasonably well, the issue is with the DNS lookup. On the other hand, if the browser finds the page and looks ready to start loading it pretty quickly, but then takes ages to render the page, the problem is far more likely to be an issue with data timing out.
In the situation where there is an apparent delay in locating servers, the problem is most likely related to the DNS settings in the system. DNS (Domain Name Service) is the means by which the system translates the addresses we find easy to remember and work with (such as www.yahoo.com) to the numbering system the internet itself uses (such as 69.147.11.210 in the case of yahoo). When you send your system off looking for an internet resource by name such as yahoo.com, it first checks with whatever DNS server you have told it to use, what the IP number is, and if that DNS server is slow to respond, the process of accessing the page/resource will appear to hang, sometimes for many seconds.
You can test is the system has a DNS issue by opening a browser and typing http://69.147.11.210 and hitting enter. This should, after a very brief pause, load the Yahoo home page. If doing it this way gives you a markedly faster page access time than usual, go to your network preference pane and open the ethernet configuration (if using ethernet - the airport for wifi or modem for dialup) and in the DNS servers section, manually enter the DNS server addresses used by your ISP. There are usually two or three and they may be listed in the ISP's help pages on the internet, in the documentation that they sent, or in your router.
Actually any valid DNS server IP addresses will do, so you can actually doa search for DNS server addresses and use any that you find. Bear in mind of course that a DNS server in your own locality, or region will be likely to be quicker to respond than a DNS server on the other side of the world... though not always!
Give that a try if the problem is with the system accessing a page to begin with.
If it's that the page loads very slowly once started, the first thing to do is clear the browser's caches (in safari, try 'reset safari' which sets it back to first-used state), which can often help. After that it may be necessary to delve into the depths of the system's IP configuration since some ISPs don't seem to have particularly Mac-friendly service configurations.