Estimate of Research Bandwidth for the EBONE Backbone 
     
     
                               Phil Jones 
                            3 September 1992
     
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     0. Contents
     
          1. Introduction 
          2. Background 
          3. Data 
          4. Estimates
          5. Postscript
     

 1. Introduction
     
    The Ebone Management Committee requested that EAT provide estimates
    of what the speeds of the EBONE backbone links should be to be close
    to estimated requirements. This is expressed as a single figure.
     
 2. Background

    EAT members were very concerned that the background to the estimates
    was clearly stated lest the estimates be misinterpreted.

    Concerns have been expressed that large estimates would be
    undervalued, for example they might appear unrealistic in financial
    terms, or in comparison with what is available at the time of
    writing (or indeed reading). This paper addresses this view by:
 
      - drawing attention to it here;
      - documenting the background and assumptions behind the estimates.
     
    It has to be pointed out that estimates are, of course, made with
    varying degrees of certainty. Some of the factors affecting the
    accuracy of estimates would be:

      - the effect of Parkinson's law (variant of); 
      - the fact that projecting traffic to the future is significantly
        more difficult where the resources involved are being used at
        saturation of near-saturations levels. This is because the
        potential increase in usage is constrained by the lack of
        available resource;
      - the effect of future events (e.g. connection of additional
        networks to the Ebone or upgraded (or degraded) links.
     
    There will be loads and linkspeeds at which EBONE will be scarcely
    viable, especially for interactive traffic. There are those that
    think that EBONE is close to that already.
     
    There are (as at August 1992) those who think that the arrangements
    for inter-continental access to and from Ebone that are in place at
    the time of writing strongly militate against good estimates of the
    EBONE backbone speeds. Issues that some considers relevant here are:

      -  the lack of inter-continental resources overall;
      -  the lack of inter-continental resources belonging to the EBONE
         consortium;
      -  the technical difficulties involved in backing up 
         inter-continental links;
      -  the difficulties involved in sharing inter-continental links
         (see RFC1346);
      -  the fact that multiple agencies are involved in the arrangements 
         at both ends of almost all such links.
     
    In making the estimates, the intention is to come with a single
    figure for the whole EBONE backbone, effectively an estimates for an
    EBONE pentagon where all links are at the same speed, and assuming
    five EBS's installations configured in a pentagon as planned for
    release as a resilient EBONE in September 1992.
     
 3. Data (Assumed)
     
    Sum of the speeds of RBS connections at the EBS installations as
    follows:
     
        Stockholm      3   Mbps
        Amsterdam      3   Mbps
        Geneva        10   Mbps
        Montpellier    2.5 Mbps
        London         4   Mbps
                     ------------
                      22.5 Mbps
     
    Notes:

      - this takes the connections of the RBS to a given EBS via routers
        on the same LAN to represent a total connectivity of 2 Mbps;
      - it would be valuable to see the calculations redone based on the
        bids for connectivity for Ebone93.
     
 4. Estimates
     
    Three estimates are provided assuming:
     
      a) that the backbone speed should be half the total of RBS access
         speeds: 11 Mbps;
     
      b) that the backbone speed should be equal to the highest of the
         total access speeds at the five EBS installations: 10 Mbps;
     
      c) gut feeling, which is 3 Mbps. (Note that this is roughly an order
         of magnitude greater that that currently available).
     
 5. Postscript (Written Later)
     
    My thanks to Bernhard Stockman for his help with this paper.
    Apologies are due for the delay in the publication of the paper.
    This was due to the pressure of other work on both Bernhard and the
    author. The results were provided in a written report distributed to
    the Ebone Management Committee for its meeting in September 1992,
    and the background explained to the committee at the time by the the
    author.
     
    Other, much more sophisticated, analysis could be made of the
    requirements on a network, e.g. by more detailed analysis of the
    usage or by other means (e.g. surveys of the customers requesting
    estimates of requirements). For example, consideration of the usage
    of the original Ebone pentagon could have been done based on the
    source and destination RBS' of the traffic. Based on these, one
    could have estimated the value of:

      - upgrading the five links on the original Ebone backbone;
      - installing one or more of the five possible cross-connections on
        the Ebone original backbone;
      - installing a further EBS in any one of of number of possible
        locations around Europe.

    The author's view (expressed at the Ebone Management Committee and
    to the EAT) is this should have been done before the decision was
    taken to install a sixth EBS.