Recent browser have added an optimisation that enables the browser to resolve all the DNS names that appear inside a visited HTML page while the browser displays the HTML page. This can speed up the retrieval of the next link on which the user will click. Unfortunately, on websites that contain a large number of different hostnames on each page (e.g. pointers to homepages of users who have posted comments), this may lead to a large number of DNS requests for each HTML page retrieved.

The root servers of the Domain Name Systems are highly redundant. This redundancy is important to ensure that the root DNS service continues to be provided even if one of the DNS root servers fails. These servers are well maintained and fail rarely. However, on October 1st, the H instance of the root DNS servers maintained by the US Army failed.

First part

• recordings in MPEG4 format
• recordings in Quicktime format

Second part