rfc1686.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

      to specific users and achieve some degree of customer lock-in. The
      information providers will be able to optimize the placement and
      distribution of their servers, based on either point-to-point
      streams or on multicasting to selected subgroups. The ability of
      IPng to dynamically specify the network routing would be an
      attractive feature that will facilitate the flexible offering of
      network services.

   3.9  Topological flexibility

      It is hard to predict what the topology of the future Internet
      will be. The current model developed in response to a specific set
      of technological drivers, as well as an open administrative
      process reflecting the non-commercial nature of the sector. The
      future Internet will continue to integrate multiple administrative
      domains that will be deployed by a variety of network operators.
      It is likely that there will be more "gateway" nodes (at the
      headends or even at the fiber nodes, for instance) as local and
      regional broadband networks will provide connectivity for their
      users to the global Internet.

   3.10 Applicability

      The future broadband networks that will be deployed, by both the
      cable industry and other companies, will integrate a diversity of
      applications. The strategies of the cable industry are to reach
      the homes, as well as schools, business, government and other
      campuses. The applications will focus on entertainment, remote
      education, telecommuting, medical, community services, news
      delivery and the whole spectrum of future information networking
      services. The traffic carried by the broadband networks will be
      dominated by real-time video and audio streams, even though there



Vecchi                                                         [Page 10]

RFC 1686     A Cable Television Industry Viewpoint on IPng   August 1994


      will also be an important component of traffic associated with
      non-time-critical services such messaging, file transfers, remote
      computing, etc. The value of IPng will be measured as a general
      internetworking technology for all these classes of applications.
      The future market for IPng could be much wider and larger than the
      current market for IP, provided that the capabilities to support
      these diverse interactive multimedia applications are available.

      It is difficult to predict how pervasive the use of IPng and its
      related technologies might be in future broadband networks. There
      will be extensive deployment of distributed computing
      capabilities, both for the user applications and for the network
      management and operation support systems that will be required.
      This is the area where IPng could find a firm stronghold,
      especially as it can leverage on the extensive IP technology
      available. The extension of IPng to support video and audio real-
      time applications, with the required performance, quality and cost
      to be competitive, remains a question to be answered.

   3.11 Datagram service

      The "best-effort", hop-by-hop paradigm of the existing IP service
      will have to be reexamined if IPng is to provide capabilities for
      resource reservation or flows. The datagram paradigm could still
      be the basic service provided by IPng for many applications, but
      careful thought should be given to the need to support real-time
      traffic with (soft and/or hard) quality of service requirements.

   3.12 Accounting

      The ability to do accounting should be an important consideration
      in the selection of IPng. The future broadband networks will be
      commercially motivated, and measurement of resource usage by the
      various users will be required. The actual billing may or may not
      be based on session-by-session usage, and accounting will have
      many other useful purposes besides billing. The efficient
      operation of networks depends on maintaining availability and
      performance goals, including both on-line actions and long term
      planning and design. Accounting information will be important on
      both scores. On the other hand, the choice of providing accounting
      capabilities at the IPng level should be examined with a general
      criterion to introduce as little overhead as possible. Since
      fields for "to", "from" and time stamp will be available for any
      IPng choice, careful examination of what other parameters in IPng
      could be useful to both accounting and other network functions so
      as to keep IPng as lean as possible.





Vecchi                                                         [Page 11]

RFC 1686     A Cable Television Industry Viewpoint on IPng   August 1994


   3.13 Support of communication media

      The generality of IP should be carried over to IPng. It would not
      be an advantage to design a general internetworking technology
      that cannot be supported over as wide a class of communications
      media as possible. It is reasonable to expect that IPng will start
      with support over a few select transport technologies, and rely on
      the backwards compatibility with IP to work through a transition
      period. Ultimately, however, one would expect IPng to be carried
      over any available communications medium.

   3.14 Robustness and fault tolerance

      Service availability, end-to-end and at expected performance
      levels, is the true measure of robustness and fault-tolerance. In
      this sense, IPng is but one piece of a complex puzzle. There are,
      however, some vulnerability aspects of IPng that could decrease
      robustness. One general class of bugs will be associated with the
      change itself, regardless of any possible enhancement in
      capabilities. The design, implementation and testing process will
      have to be managed very carefully. Networks and distributed
      systems are tricky. There are plenty of horror stories from the
      Internet community itself to make us cautious, not to mention the
      brief but dramatic outages over the last couple of years
      associated with relatively small software bugs in the control
      networks (i.e., CCS/SS7 signaling) of the telephone industry, both
      local and long distance.

      A second general class of bugs will be associated with the
      implementation of new capabilities. IPng will likely support a
      whole set of new functions, such as larger (multiple?) address
      space(s), source routing and flows, just to mention a few.
      Providing these new capabilities will require in most cases
      designing new distributed algorithms and testing implementation
      parameters very carefully. In addition, the future Internet will
      be even larger, have more diverse applications and have higher
      bandwidth. These are all factors that could have a multiplying
      effect on bugs that in the current network might be easily
      contained. The designers and implementers of IPng should be
      careful. It will be very important to provide the best possible
      transition process from IP to IPng. The need to maintain
      robustness and fault-tolerance is paramount.

   3.15 Technology pull

      The strongest "technology pull" factors that will influence the
      Internet are the same that are dictating the accelerated pace of
      the cable, telephone and computer networking world. The following



Vecchi                                                         [Page 12]

RFC 1686     A Cable Television Industry Viewpoint on IPng   August 1994


      is a partial list: higher network bandwidth, more powerful CPUs,
      larger and faster (static and dynamic) memory, improved signal
      processing and compression methods, advanced distributed computing
      technologies, open and extensible network operating systems, large
      distributed database management and directory systems, high
      performance and high capacity real-time servers, friendly
      graphical user interfaces, efficient application development
      environments. These technology developments, coupled with the
      current aggressive business strategies in our industry and
      favorable public policies, are powerful forces that will clearly
      have an impact on the evolution and acceptance of IPng. The
      current deployment strategies of the cable industry and their
      partners do not rely on the existence of commercial IPng
      capabilities, but the availability of new effective networking
      technology could become a unifying force to facilitate the
      interworking of networks and services.

   3.16 Action items

      We have no suggestions at this time for changes to the
      directorate, working groups or others to support the concerns or
      gather more information needed for a decision. We remain available
      to provide input to the IPng process.

4.  Security Considerations

   No comments on general security issues are provided, beyond the
   considerations presented in the previous subsection 3.4 on network
   security.

5.  Conclusions

   The potential for IPng to provide a universal internetworking
   solution is a very attractive possibility, but there are many hurdles
   to be overcome. The general acceptance of IPng to support future
   broadband services will depend on more than the IPng itself. There is
   need for IPng to be backed by the whole suite of Internet technology
   that will support the future networks and applications. These
   technologies must include the adequate support for commercial
   operation of a global Internet that will be built, financed and
   administered by many different private and public organizations.

   The Internet community has taken pride in following a nimble and
   efficient path in the development and deployment of network
   technology. And the Internet has been very successful up to now. The
   challenge is to show that the Internet model can be a preferred
   technical solution for the future. Broadband networks and services
   will become widely available in a relatively short future, and this



Vecchi                                                         [Page 13]

RFC 1686     A Cable Television Industry Viewpoint on IPng   August 1994


   puts the Internet community in a fast track race. The current process
   to define IPng can be seen as a test of the ability of the Internet
   to evolve from its initial development - very successful but also
   protected and limited in scope  - to a general technology for the
   support of a commercially viable broadband marketplace.  If the
   Internet model is to become the preferred general solution for
   broadband networking,  the current IPng process seems to be a
   critical starting point.

6.  Author's Address

   Mario P. Vecchi
   Time Warner Cable,
   160 Inverness Drive West
   Englewood, CO 80112

   Phone: [phone]
   Fax: [phone]
   EMail: [e-mail]
































Vecchi                                                         [Page 14]