Comments

[bmanning () ISI EDU]

                        A commentary on
                "A Routing Design for ATM NAPS"
                        
                        Bill Manning
                        bmanning () isi edu
  
                        23 August 1994
  
  Abstract:
        Attempts to clarify the important points in this document and proposes
        an alternative that can be deployed in a reasonable timeframe.
  
  Commentary:
  
        This is an interesting and useful paper. It covers what was current
        technology in 2q94 and points out one of several methods for 
        supporting ATM in the context of a Routing Registry/Route Server.  
        Several clever approaches were used to overcome gaps in standards 
        implementation by vendors.
  
        The approach indicated in section two of the MERIT paper is a common 
        approach that was generally approved in both the NANOG meeting and a 
        NAP participant meeting that was held during the Toronto IETF.

        The difficulties with the RFC 1490 approach were listed in the 
        Toronto meeting.  I list them here:
  
                There is no clear migration path from this approach to
                a more correct/robust implementation using RFC 1577
                encapsulation over native ATM (OC3c).

                There are additional points of failure and additional costs
                with the requirement for an ADSU.

                The listed approach requires manual configuration.

                This appears to lock the NAP into a top speed of 45Mbps
                or DS3 speeds.

        In addition to these weaknesses, there were a number of assumptions
        regarding specific hardware implementations of ATM protocols (use
        of a very small selection of vendors and limited interfaces) and 
        the ability and/or willingness of the attaching ISPs to work toward
        a more elegant, cheaper, robust solution at the possible expense of 
        some time while vendors address the implementation gaps.
  
        Questions on the desirability of a native media support with RFC 1577
        support were posted to the IP-ATM wg of the IETF and the 
        email response was affirmative in recommending an approach with
        RFC 1483/1577 over AAL5 with LLC/SNAP coding.
        A brief review of the European PNO pilots seems to indicate that
        this is the desired approach in that arena too.
  
        Even the vendors who were not invited to either meeting have expressed
        an interest in fixing these problems in the near term, where near term
        is the next 2 to 6 months.

        So, I suggest the MERIT paper should not be viewed as the only or 
        desired method of connecting to an ATM NAP.  It should be carefully read
        as the documentation of a successful experiment.

--bill
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