http:www.bmas.ja.net

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The Bandwidth Management Advisory Service - BMAS

• http//www.bmas.ja.net
• Ingrid Evans George Neisser
• Manchester Computing
• University of Manchester
• ingrid.evans_at_man.ac.uk
• George.Neisser_at_mcc.ac.uk

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Background to BMAS

• Recent years have witnessed growth in
• Dynamic Web content.
• Multimedia and real-time applications.
• Expansion of JANET user base to include FE
  colleges.

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Advisory Requirement Identified

• In recognition of the changing types of web
  traffic, UKERNA carried out a survey in 2002
  amongst academic institutions.
• The following conclusions were drawn
• There is a general need for web caching.
• There is a need for generic advice.
• An Invitation to tender was issued Summer 2002.
• Manchester Loughborough awarded contract.

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BMAS

• BMAS Remit to deliver leading-edge
  state-of-the-art advice to UK academic
  institutions on how to maximise the efficiency of
  their bandwidth resource utilisation
• Staffed by the former JWCS team.
• Plenty of experience.
• Will expand to include new and on coming
  bandwidth management techniques and technologies.

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What is Bandwidth Management?

• In general terms, Bandwidth Management is the
  control and monitoring of your network bandwidth
  allocation to get best use out of said link.
• Bandwidth Management can encompass various
  techniques and policies
• Your requirements will depend on numbers of
  users, work profiles, teaching and research
  programmes, connection capacity etc, etc.

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How does bandwidth management affect me?

• As a Web Manager you may want wonder how
  bandwidth management affects you.

• Consider the following
• Dear Web manager, we would like streaming media
  incorporated onto our web pages

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How else does bandwidth management affect me?

• Did you know that making your site cacheable will
  make it load more quickly for your visitors and
  reduce load on your server?

If a site loads quickly people will revisit.
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Any other points about bandwidth management?

• What about data compression? Compression
  techniques could also help to enhance your site
  visitors experience by making your site load
  quickly.

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Time to sit and think a while..

• Wed now like you to divide into groups and spend
  about 5 -10 minutes discussing how you have
  implemented bandwidth management techniques on
  your website.
• If you do not think think that you have
  implemented any techniques, then consider how
  bandwidth management might affect your website.

• Think about

• Streaming media, and its implications for your
  site.

• Also, discuss the known advantages of caching.

• Consider image file formats too and how they
  might impact on bandwidth.

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Ways to enhance your website using bandwidth
management techniques

• Why, and how to, make your site cacheable.
• Bandwidth isnt a problem on campus.

• Maybe, but what about external visitors and
  distance learning etc? Most people at home still
  use dial-up.

A cached website will be returned to the user
from a much nearer location than the site of
origin thus making it load quicker.
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How to make your site cacheable

• Add HTTP headers
• HTTP headers give control over how browser and
  proxy caches handle your web objects.
• Not seen in HTML as they are sent by the server
  before the HTML.

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What do HTTP headers do?

• Cache control headers can be quite specific and
  control freshness, bypass of the cache etc with
  the settings such as
• Max-age (seconds)
• Public
• No-cache
• Must-revalidate

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What else can you do to make your site cacheable?

• Refer to objects consistently using the same URL

• Use a common library of images

• Make caches store images and pages that dont
  change often by specifying a far off Expires
  header

• If a resource changes (in particular a
  downloadable file), change its name

• Dont change files unnecessarily to avoid falsely
  young Last modified dates. Only copy files to
  the server which have actually changed as opposed
  to copying the entire site.

• Use cookies only where necessary as they are
  difficult to cache.

• Minimise use of SSL

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Writing cache-aware scripts - hints and tips.

• When using scripting, dont POST if possible.
  POST method is almost impossible to cache. GET is
  preferred

• Dont embed user specific information in the URL

• Dont assume that all requests from a user are
  from the same host as caches can work together in
  a variety of infrastructure

• Generate Content-Length response headers. This
  allows for the response of the script to be used
  in a persistent connection and allows the client
  to request multiple objects on one TCP/IP
  connection thus making the site seem much faster.

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Keeping your visitors happy! How about reverse
caching?

• Reverse caching and http-acceleration can
  directly benefit web managers

• Reverse caches can offload the delivery of static
  content from your web server.

• Requests to web sites are intercepted by
  reverse-proxy caches with held objects being
  returned to the requestor as if from the original
  web site.

• Using http-acceleration can make a proxy server
  act as an output buffer for dynamic web content.

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Reverse proxy caching advantages

• Simpler and faster than web servers

• Can be preloaded with content

• Can be set to automatically retrieve updated
  content.

• Possible to have multiple reverse proxies as they
  can communicate via ICP (Internet cache protocol)

• Can act as defence against hackers as they are
  another layer' between the outside world and
  your data.

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Reverse proxy caching advantages

• Can improve server performance whilst adding web
  site traffic surge protection.

• Some high-end reverse proxy cache devices have
  features which can distribute, as opposed to
  store, multimedia formats such as Apple
  QuickTime, Windows Media or Real Network's G2
  format.

• This distribution of multimedia from the network
  edge as opposed to the web server, can
  drastically reduce server and network bandwidth
  load

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Reverse proxy caching - not to be confused with

• Prefetching or web acceleration
• There is some debate as to whether the practice
  of prefetching or web acceleration actually ends
  up generating more web traffic in the end!

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More details about reverse proxy and
http-acceleration

• See
• http//www.nwfusion.com/reviews/2000/0410revtrend.
  html
• For more details about implementing caches and
  advanced cache features re multimedia.
• Brian Davidson's excellent caching site at
  http//www.web-caching.com/mnot_tutorial/how.html
  
• Also Chapter 13 of Strategies for Web Hosting
  and Managed Services by Doug Kaye - Wiley
  Computer Publishing 2002

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What about dynamic content such as streaming
media?

• Streaming media is becoming much more widely used
  as a teaching aide and for distance learning.

Why should that affect you?
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What about dynamic content such as streaming
media?

• You may have been asked to incorporate streaming
  media into your website.

• New advancements in HTML-like languages mean that
  complex integrated media can be generated. Video
  can be used in conjunction with text and
  Powerpoint to provide interactive media using the
  SMIL language (Synchronised Multimedia
  Integration Language)

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What about bandwidth and streaming media?

• Being aware of some of the issues with these
  components means that you should be able to
  maintain a fast, efficient website, even if you
  are using dynamic media.

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Streaming media points for consideration

• There are various software solutions available
  which will generate streaming content. The big 3
  are
• Real Networks Server
• Apple QuickTime
• Windows Media Server
• Each software package has its advantages and
  disadvantages.

Remember from the outset to consider the number
of users who will be viewing your media, and at
what bit rate
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The importance of bit rate

• When encoding media files, they should be
  optimised for the speed of the recipients
  connection .
• This is especially important if you think that a
  lot of your content will be viewed out of campus
  (i.e. via dial up). Files which are not optimised
  in this way may result in poor quality for your
  visitors and more load on your webserver
  generated by visitors trying to view the files on
  your server.

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The importance of bit rate

• Another consideration with bit rate is the fact
  that some file formats, such as Apples
  QuickTime, work better with a higher bit rate of
  1000Kbps.

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Web server v streaming server

• If you only have a few streaming media files,
  then loading streaming server software onto your
  website should suffice.

• If however, you wish to include

• A lot of streaming content

• Files which stream at different speeds (for
  visitors in different locations)

• Complex integrated media

You should possibly consider a dedicated
streaming server. This will also relieve load
from your web server .
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A word about complex integrated media.

• Files generated in this way such as those created
  using the SMIL language, have their media divided
  into components which are then streamed
  separately, but viewed as one file by the
  visitor.
• This process obviously has bandwidth implications

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Streaming media recommendations

• Consider your audience from the outset and what
  THEIR bit rate will be

• Choose appropriate streaming software taking into
  consideration performance over various bit rates

• Think about how much streaming media will be
  included on your website. If there is a lot, you
  may be better off with a dedicated streaming
  server

• Will integrated media be used? If so, think about
  bandwidth usage for these types of files

• If you run streaming media from your web server,
  perhaps you should consider a viewing policy
  limited by user groups, location or time

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Bandwidth Management techniques - data
compression

• As a web master you will probably be responsible
  for developing a web policy and overseeing the
  upload of pages from many different sources.

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Bandwidth Management techniques - data
compression

• Encouraging your contributors to be aware of data
  compression can reduce bandwidth consumption and
  make your WebPages load more quickly.

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Bandwidth Management techniques - data
compression

• Its a simple solution but when used on a large
  site, data compression can prevent slow downloads
  and thus reduce visitors waiting time.

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What do we mean by data compression?

• In a web management context were primarily
  referring to image compression using a variety of
  formats such as JPEG, GIF, PNG etc.

• File format features
• JPEG - A lossy compressor which produces very
  small file sizes
• GIF - A lossless compressor. Can incorporate
  transparency into an image.
• PNG - Lossless compressor can be used as patent
  free replacement for GIF. Can also incorporate
  transparency

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So where do I come in?

• Encourage your contributors to use one of the
  aforementioned image file formats

• Persuade them not to use large file formats such
  as Bitmap (.bmp)

• Images should not be anymore than a couple of
  centimetres squared in size. If larger, or more
  detailed images are required or where there are a
  few images, encourage the use of thumbnails. The
  Tucows site at http//tucows.mirror.ac.uk/index.ht
  ml has a lot of thumbnail software listed.

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So where do I come in?

• Resolution is an important factor. Do not use
  images for the web that have been specifically
  created for print. Such images will have an
  unnecessarily high resolution which will increase
  file size dramatically whilst monitors only have
  a resolution of 72 ppi.

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A lot to take in!

• If you take some bandwidth management techniques
  into consideration, your website will load
  quickly, and your visitors will see a high
  quality website

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A lot to take in!

• Remember the following points
• Make your website cacheable by

• Use of HTTP headers

• Reverse caching

• http-acceleration

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Dont forget

• Think about the implications of using streaming
  media

• Consider which streaming server software is best
  for you

• Decide how much streaming media will be used now
  and in the near future

• Assess what your streaming media users bit rate
  will be.

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And another thing!

• Theres also data compression

• Use compressed image file formats such as JPEG,
  GIF and PNG

• Encourage use of thumbnails where appropriate.

• Encourage use of smaller, more widely spaced
  images.

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You dont get away that easily..

• Wed like you to search on the web and see what
  you can find on the subject of Bandwidth
  Management that is applicable to you.
• Try http//www.zdnet.com
• http//www.bravenet.com
• http//www.w3c.org - info re image compression
• http//www.web-caching.com/ - info re reverse
  caching etc

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Finally.

• Do visit our website at http//www.bmas.ja.net
• Or email us at support_at_bmas.ja.net
• You can call us on [phone]
• Keep revisiting our website as our content will
  continue to increase.

• Its good bye from me

And its goodbye from him