[Swprograms] [BBC explains The BBC News website - under the bonnet

[Daniel Say <say@xxxxxx>]

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Subject: BBC NEWS | Magazine | The BBC News website - under the bonnet
X-URL: http://news.bbc.co.uk/1/hi/magazine/4606719.stm

   [11]Low Graphics version | [12]Change edition

Last Updated: Friday, 3 June, 2005, 11:10 GMT 12:10 UK

   The BBC News website - under the bonnet
   By Kevin Hinde
   Head of technical development, BBC News website

   The BBC News website serves 3 million users and 24 million page
   impressions every day. We try to make sure that the site is available
   for everyone round the clock.

   This is particularly important on big news events, when the site comes
   under its heaviest loads. On the day of the UK election results this
   year we had 4.3 million users and just over 50 million page
   impressions.

   The technology which serves the site is designed to be as simple as
   possible. The simpler the site, the cheaper it is to run. There are
   fewer elements which can malfunction on big days; and there are fewer
   parts which can be compromised by someone trying to gain unauthorised
   access.

   Unlike other sites which carry advertising, we do not receive more
   revenue the more people use our site, so it is important that we are
   able to serve as many people as possible and keep costs low.

   We have a number of web servers ("server farms") in London and New
   York. These two cities are both excellent hubs connecting many
   different networks on the internet, and they are far enough apart so
   that if there were a major disaster in either city we could continue
   serving web pages from the other location.

   The Domain Name System (DNS) is the Internet's method of translating
   domain names, like "news.bbc.co.uk" into computer addresses. We use a
   modified DNS server which is able to balance requests for web pages
   evenly over all of the web servers we run.

   Users from the UK are sent to the London server farm, which is paid
   for from licence fee money. International users go to the New York
   server farm, which is mostly funded by the grant-in-aid from the
   British government, which pays for the BBC world service.

   You can see an overview of our network [44]here.

   We "peer" with most internet service providers (ISPs) in the UK.
   "Peering" means that we agree to exchange traffic between our network
   and the ISP network without charge. The ISP benefits because their
   customers are able to download BBC content more quickly; the BBC
   benefits because it is able to reach almost all of the internet users
   in the UK without incurring massive bandwidth charges.

   The servers themselves are running Apache web server software on
   either the Linux or Solaris operating system. They are configured so
   that the web server software and the operating system run only the
   minimum number of modules and add-ons to do what we need.

   At the top of every BBC News webpage is a "change edition" link. We
   have two editions of the site; the same stories are available on both,
   but there is a different emphasis on the index pages. For example, the
   UK edition might lead with a story about UK interest rates where the
   international edition would have a story about the European
   parliament.

   If you click on the "change edition" link the web server sends a small
   file, called a "cookie", which is stored on your machine. The next
   time you visit our site, your web browser sends the cookie back to us
   the server reads the cookie and returns the correct edition.

   The first time a reader comes to the website, they won't have a
   cookie. In that case, the web server just sends the UK edition to
   readers who come to the UK server farm, and the International edition
   to everyone else. Apart from that, there is no connection between the
   edition which is served and the server farm it is served from - users
   in the UK can get the International edition and vice versa.

   The web pages themselves use a technique called Server Side Include
   (SSI) to provide a dynamic view of the contents of the site. When a
   reader requests a web page, the web server reads the page and looks
   for SSI instructions, which tell the web server to replace that part
   of the page with the contents of a file.

   For example, most stories have an "other stories in this section" box
   on the right-hand-side. The contents of this box come from an SSI
   instruction, so the reader always sees an up-to-date list of current
   stories, even if the story itself has not changed.

   To squeeze the maximum possible performance from our web servers, we
   have moved the picture files to a different set of servers
   ("newsimg.bbc.co.uk"). The image servers do not need any of the
   modules to process SSIs or decide which edition to serve, so they can
   be minimally configured.

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