Bandwidth design issues

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Bandwidth design issues

• Bandwidth in the corporate design process
• Preamble/anecdotes about bandwidth
• A problem and a blessing
• Fixed or flexible bandwidth
• Broadband method of communication has high
  bandwidth
• Analysis and design of bandwidth
• Bandwidth management
• Summary
• Practical and individual review of assignment
  progress

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Bandwidth

• What is it?
• The need for bandwidth
• Dedicated bandwidth or shared bandwidth?
• Calculating it
• QoS
• Related to the assignment

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Preamble bandwidth world

• Bandwidth forecasts evidence from recent
  studies (see computing.co.uk) shows large growth
  in bandwidth between now and 2010
• Due to bandwidth hungry applications
• Increased information systems use
• Do we need the extra bandwidth?
• On campus bandwidth?
• Off campus bandwidth?
• Equipment 1gbit switches almost the norm
  whether you need it or not
• 10Gbps, 100Gbps connections or do we
  accelerate/efficiently use what we have already
  got? e.g. see story about Britannia Airlines in
  early Nov and their use of intranet accelerators

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What is Bandwidth?

• Bandwidth has a general meaning of how much
  information can be carried in a given time period
  usually a second) over a wired or wireless
  communications link.
• More technically, bandwidth is the width of the
  range of frequencies that an electronic signal
  occupies on a given transmission medium.
• Any digital or analog signal has a bandwidth.
•  Ultimate constraint is the physical ability of
  the medium (cable/air/optical fibre) and speed of
  emitter/detector electronics

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A bandwidth definition?

• The range of frequencies, expressed in Kilobits
  per second, that can pass over a given data
  transmission channel within a network. The
  bandwidth determines the rate at which
  information can be sent through a channel - the
  greater the bandwidth, the more information that
  can be sent in a given amount of time
• Usually measured in bits-per-second.
• A full page of English text is about 16,000 bits.
  A 56Kbs modem can easily move 16,000 bits in less
  than one second.
• Source Searchnetworking
• A more palatable definition measurement of the
  amount of data transmitted over the network in a
  fixed amount of time through a pipeline

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Bandwidth - Corporate overview

• It is general accepted design practice for
  bandwidth to be thought about
• It is useful to think about requirements before
  implementation why? Discuss (and then see next
  slide)
• A business wants value for money and a bandwidth
  which is effective for the needs
• So as you will see it is a case of predicting
  bandwidth usage an exact bandwidth fit never
  happens it is a question of best offered
  service

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To understand bandwidth

• It is a resource and hence it is necessary to
  understand due to impact on
• Performance
• Cost overestimating our requirements could cost
  money carriers factor in banding rates
• Resiliency
• It follows that an understanding of the
  corporations environment is therefore advisable

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Technology overview

• Consumption of bandwidth in a consistent manner
  over time using technology which includes
• Bandwidth aggregators
• Multiplexing used by the ISPs/data centres
• Complex need to use available bandwidth
  efficiently by combining traffic from different
  users and of various types
• Dense Wave Division Multiplexing (DWDM) see
  tutorial sheet
• Multiprotocol Label Switching (MLPS)
• Augments routers with labels which can route
  traffic around failures, congestion and
  bottlenecks
• See slide later on

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Bandwidth examples

• Big bandwidth
• Mega bits per second
• Small bandwidth
• Kilo bits per second
• Remember well discussing connectivity we may mean
  end to end connection but to get there various
  devices exist along the swim
• Bandwidth may vary on the journey
• There may be bandwidth bottlenecks

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Bandwidth how to analyse it

• Initial thoughts can include
• Find out the traffic load caused by the various
  applications that are running across the network
• Data on the network type of data/volume
• Find out the traffic behaviour,
  i.e.bursty/talkative etc
• Internet traffic is bursty (sporadic)
• Environment of the business 9 5pm? 24hr?
• Peak and troughs
• Need to consider future proofing and performance

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How much bandwidth?

• To make a quantitative attempt at this is
  required although if it not a perfect science
  some qualitative factors may be relevant
• Factors to consider include
• The number of users
• It is accepted that the more users you have the
  more potential bandwidth a business will need
• Example on next slide which shows that utilizing
  your connection has a clear impact on the amount
  of bandwidth needed.

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Bandwidth amount

• The figures below demonstrate how much bandwidth
  would be needed to support a given number of
  users FOR SIMPLE WEB ACCESS ONLY. This figure
  does not factor in other common user applications
  such as email, or messaging, and does not account
  for any external access such as servers or remote
  VPN access.192 kbps 1-10 users384 kbps 10-20
  users768 kbps 20-35 users1088 kbps 35-50
  users1536 kbps/1.54 Mbps 50-70 users
• Source Dell Corporation
• Or if an average web page size of 50k, 100,000
  downloads of that page each month would require
  5Gb of bandwidth

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How much bandwidth?

• Other factors to consider include
• Type of applications
• With this in mind, you should take into
  consideration the type of applications the
  business will be/is running and how much
  bandwidth they will require
• It is question of finding out how greedy some
  application are compared to one another
• Applications which use more than just text to
  transmit will have more volume and are more
  complicated

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How much bandwidth?

• Other factors include
• Reliability
• If mission-critical and a need the full bandwidth
  of the line, a dedicated circuit
• For example, (Fractional T1 or T1) T1 circuits
  are dedicated, meaning that you will have access
  to the full bandwidth of the circuit without
  reconnecting, dialing-up, or sharing the line
  with any other users
• Non mission-critical work, Shared bandwidth
• For example, a DSL bandwidth is shared, meaning
  that you will have access to up to a certain
  level of bandwidth, but this will vary over time
  and is dependent on the overall usage of the
  network

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Tools

• Tools on the market vary
• On the Internet Speed test tools (see next slide)
  which indicate the performance
• Network performance commands on LANs e.g. netperf
  or tccp
• Both the above deal with as is
• For evaluation of to be i.e. how much bandwidth
  to specify initially we recommend a spreadsheet
  estimating approach based on experience
• Attempt the cost out what is called the Duty
  Cycle which is the statistical proportion of
  time for which the traffic is produced e.g.
  100kbps data rate system which has a dedicated
  cycle of 20 consumes an average of 20kbps over
  time

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Calculation of bandwidth

• This is difficult you can ask the Guest Speaker
  how he does it.
• We need an estimate of total usage of each of the
  relevant media for transmission
• You are attempting to derive traffic volumes
• And take into account the carrier medium

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How to estimate bandwidth?

• Build a spreadsheet model which includes
• Demand
• Bandwidth devices
• Bandwidth bottlenecks
• Costs
• At a later date the actual can be compared to the
  estimate
• From experience the more bandwidth means of
  course more money!

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Spreadsheet estimating process

• Design lifecycle what you have do for the
  assignment!
• Determine forms of traffic
• Estimate the required bandwidth for each
• Aggregate the bandwidth according the carrier
  type
• Build in contingency
• Investigate the available products to supply
• Recommend a selection of products using a
  selection criteria which can include
• Value added services, cost, ease of use
• Investigate necessary equipment
• Security, backup, maintenance considerations

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Other considerations

• Access to the Internet from
• External access
• Internal access from the Internal network
• So devices such as ISDN link and modem, ISDN to
  Ethernet converter running to an Ethernet switch
  will need thinking about
• Routers running firewalls may also be another
  consideration as security has a latency overhead

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Calculation of network traffic

• Need to find out the stated data rate of the
  network link
• Most LANs operate at 10 Mbps
• I am assuming here an Ethernet LAN
• Most WANs are much slower operating in the range
  of ?????

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Optimisation Solutions

• Minimising bandwidth usage
• Cisco IOS Multiprotocol Label Switching (MPLS)
• fuses the intelligence of routing with the
  performance of switching and provides significant
  benefits to networks with a pure IP architecture
  as well as those with IP and ATM or a mix of
  other Layer 2 technologies
• MPLS technology is key to scalable virtual
  private networks (VPNs) and end-to-end quality of
  service (QoS), enabling efficient utilization of
  existing networks to meet future growth and rapid
  fault correction of link and node failure. The
  technology also helps deliver highly scalable,
  differentiated end-to-end IP services with
  simpler configuration, management, and
  provisioning for both Internet providers and
  subscribers
• Source Cisco
• Easynet ISP offer this approach

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Optimisation Solutions

• Gatekeeper bandwidth management
• A device which can throttle bandwidth on demand
• A number on the market including Cisco

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Bandwidth management (related)

• Techniques of interest
• Web site cacheable will make it load more
  quickly for visitors and reduce load on server
• Add HTTP headers
• File formats and Data compression make site
  load more quickly
• Steaming media

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Summary

• Bandwidth is a corporate resource
• Needs to be specified and managed
• Conserved
• Used effectively
• Providing the right bandwidth profile is
  important at the start of use
• Adjusting to requirements over time is important
  to recognise at the start