Capacity Planning
Capacity Planning |
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It is important to consider both server-side and client-side bandwidth when choosing your server’s network connection(s). If your server connects only to an intranet, this question may be moot, except when planning a major upgrade; but if your site connects to the Internet, there are many possible types and speeds of network connection. The speed you require depends on the amount and type of traffic your site generates. The 5-KB static Web page discussed in the section on traffic earlier in this section is representative of many short, text-only pages, but relatively few Web pages contain only text. In the worst case, a page containing a substantial number of graphic elements can require one GET request per graphic. These requests add up quickly and have an impact on performance.
Web pages are increasingly being built as applications, and as a result are more processor-intensive. This by itself does not necessarily have much effect on bandwidth requirements. Content, however, does have an effect. Streaming multimedia, for example, is inherently bandwidth-intensive, and unless you can guarantee that your server will have only a small number of users on a high-speed intranet, you may find that spikes in user volume will easily overwhelm your network bandwidth capacity. Pages that perform extensive lookups in a database, on the other hand, may put a heavy load on the link from the Web server to the database server (and may place a really heavy load on the number of CPUs in the server computer for the database). However, these pages will not place much demand on the link from the Web server to the intranet or Internet, unless the returned datasets are quite large.
IIS 5.0 automatically determines the size of any objects (such as text, files, or graphics) on a static page and the size of the page itself. When the client issues a GET request, the server uses a “Content-Length” header entry to report the size of the requested object or page. This HTTP 1.1 header entry has minimal cost in terms of overhead, and allows the browser to determine approximately how long the active connection will be used, thus affecting the browser’s connection strategy. A browser such as Microsoft® Internet Explorer creates a new connection only when an existing one is “blocked.” If the order of requests is such that larger .gif files are downloaded first, or if the connection speed is slow, more connections may be necessary.