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Summary of Internet Architecture Discussion 1991-01-08

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Internet Activities Board

Summary of Internet Architecture Discussion

January 8-9, 1991


    The Internet Activities Board (IAB) met with the Internet Engineering Steering Group (IESG) on January 8-9, 1991 at the USC Information Sciences Institute in Marina del Rey, CA. The meeting devoted the afternoon of the first day and the morning of the second day to an extended discussion of the future directions for Internet architecture. This document reports on this architecture discussion, which was led by Dave Clark. The minutes of the rest of the meeting are reported elsewhere.


    The first afternoon was spent trying to define the problems to be solved. Clark began the discussion with a presentation of his view of the key issues; his slides are reproduced in Appendix A. Each of his topic slides (7-12) were then discussed in turn.

    2.1 The Multi-Protocol Internet [Slide 7]

      The discussion began by setting a timeframe for evolution of the Internet and the TCP/IP protocol suite. This timeframe determines the importance of several issues, in particular routing and addressing. It was accepted that OSI is not yet here, and the general feeling was that it will not be for some time. A question: does OSI lead or follow current technology? Alternative scenarios were:

      1. OSI and TCP/IP both live forever,

      2. TCP/IP fades,

      3. OSI fades,

      4. Next Generation replaces both.

      Debate ensued over the merit of evolving two protocol suites in tandem; some advocated friendly competition, while others called it a waste of effort which could lead to the demise of both.

      One alternative discussed was to redirect IAB/IETF efforts to emphasize OSI, devoting all our resources to making OSI a reality. Such actions could include profiling standards, merging standards, and fixing broken OSI standards. However, it was observed that the IAB can only have direct influence over protocols that it controls; an effort based on profiling other protocols is not likely to be successful.

      Here is a sample of comments on this topic, lightly paraphrased:

      • “The answer will come from the grass roots; people won’t switch unless the old suite breaks or the new one has more features”.
      • “Are we asking the wrong question? We’re facing really heterogeneous networks, and must include variety in our thinking”.
      • “The IAB can exert more leadership over the (only) suite that it controls”.
      • “Even productive competition may be a diversion of effort; we may be getting too complex”.
      • “If the goal is interoperation, the world must agree on the protocol basis; right now that means TCP/IP”.
      • “I prefer TCP/IP because
      • prefer the [development and standardization] process [of the IAB/IETF]”.
      • “I am sympathetic to the concern about dilution of effort, but
      • doubt that there is really a tradeoff; it will be different people”.

      The concensus most nearly supported the continuation of parallel development of both TCP/IP and OSI suites.

    2.2 Routing and Addressing [Slide 8]

      The problems of routing and addressing may be strongly affected by the rise of commercial common carrier networks. Some of the scaling and topology problems we experience today will look different as access control and topology become important aspects of the interconnection of commercial service providers.

      The target size of the Internet is an important consideration. One viewpoint expressed was that commercial common carriers will dominate, so we only have to wait for them to solve our problems of routing and addressing. However, the more widely held viewpoint was that, while the topology may eventually be whatever the common carriers give us, we cannot count on their providing us the complete service we want. The Internet must be seen as a large and diverse system, and the evolving architecture must be able to deal with combined public/private Internet with a very large address space.

      Currently there are many different grades of service, rather than one uniform service. It was suggested that a package transportation service is a better service analogy than the telephone system. Thus, the telephone system offers a homogeneous service, while planes, ships, trains all transport packages but offer different grades of service. Such a diverse infrastructure is needed in internetting.

      It seemed likely that some policy-based routing will be necessary.

      If we assume that the Internet architecture will continue in use indefinitely, then we need flexibility.

      Multicast was a controversial topic. Currently there are no applications available that can make use of its facilities. However, there are some future uses of multicast, including routing, mailing lists, and mass distributions.

    2.3 Getting BIG [Slide 9]

      Getting big presents several obstacles. The IAB’s past X.500 deployment planning effort was discussed as an example of the problems that can arise. The problem was partly that X.500 is an international standard, hard to adapt.

      It was suggested that testing new services like X.500 in the Internet can be very valuable, but it is possible only when there is government funding: “For success in applications testing, you need to find a sugar daddy”. We need more tools for applications — IPC, RPC, authentication — but unfortunately funding for applications development is largely missing. It is important to distinguish research from infrastructure development.

    2.4 Dealing with Divestiture [Slide 10]

      A number of points were made.

      • The introduction of commercial services and the need for accounting will impact the protocols.

      • We need to develop a variety of means for measurement and accounting; pricing can be determined later.

      • Charging may lead to protocol changes to minimize costs, and the consequences are unpredictable.

      • There is no difference in the mechanics of accounting information collection between a connection-oriented and a connectionless network. However, billing on a per-packet basis in a datagram network could lead to very high overhead.

      • There is a need for authentication, to prevent fraud.

      • The ability to share a common link between two or more administrations is needed.

    2.5 New Services [Slide 11]

      Video is an important new service. Video is defined here as a point to point frame-oriented delay-sensitive service. There is a need to do this in a few years, just ahead of the 200MIPs multimedia workstation.

      Distributed computing and transaction protocols need to be developed. There is an authentication problem in an operating system when a transaction just appears at a host. One problem with running real distributed applications in the Internet has been the need to set up a lot of configuration information at each end.

      It was also observed that even so simple a distributed application as the DNS does not work very well, so we need to do a lot more work on distributed application tools.

    2.6 Security [Slide 12]

      We need more sophistated models of authentication.

      Application relays make it hard to build new applications.


    It was intended that the second part of the discussion would home in on some solutions. However, the group was far from a concensus on most issues. Therefore, the time was spent in detailed viewpoint presentations by a number of the participants.

    3.1 Vint Cerf

      Cerf opened with a list of assertions about the future of the Internet.

      1. It is less important that a particular technical prediction actually occurs than it is that the architecture makes it POSSIBLE.

      2. All technologies are eventually overtaken by new ones. Must accomodate PEAK requirements, and must also be prepared for some technologies to linger long past their peak.

      3. The number of “terminations” (e.g., IP addresses) per person varies from .001 to 1000.

      4. Total terminations ~ P/4 * 3 * 10, where P = number of persons = 250M, 3 corresponds to home + 2 workers, and the last factor of 10 is for safety. Implies terminations ~ 2*10**9 for US, 36*10**9 for the world.

        Note that the phone system has extremely high fan-out, Internet fan-out is much lower. Can (will? should?) this change?

      5. The routing problem is a function of the number of networks and the topology (hierarchy). Suppose we separate HOST# from NET#, and place NET# into a hierarchical structure with provision for “break-out”. Would 32 bits of NET# be enough to cover the administrative overhead of delegated assignment of address space?



        where NET# is hierarchical, and HOST# is perhaps globally unique.

        [Debate on this was postponed.]

      6. Hosts incapable of supporting DNS and other core requirements must ultimately be abandoned to their fate (when can we stop catering to them?). Backward compatibility need not be absolute; a rational window of new and old technology should be defined.

        Within each protocol suite, there must be a “central, core” set of protocols that defines the network architecture.

        The question was raised: At what level should multi-protocols exist: IP, Mail, Postscript?

      Cerf continued with a proposed list of requirements, and attempted to gather from the group a general sense of agreement or uncertainty about each one (noted in square brackets).

      1. Must support more than one protocol suite operating concurrently.

        It is NOT required that they interwork with each other. Some common applications might be usefully interworked.

        [Much discussion].

      2. Must be able to accomodate transmission bandwidths 2.4Kbps (?) to over 10 Gbps.

        [Not universal agreement; perhaps lower end should be increased.]

      3. Must accomodate new switching and transmission media wherever possible (e.g., SMDS; ISDN; BISDN; Frame Relay; optically- switched networks; color-multiplexed, tuned-laser nets, and radio technology).


      4. Must accomodate an address space for 36*10**9 terminations, 1*10**9 networks.


        [Needs debate]

      5. Must accomodate private and public network components.


      6. Must support (at least, not inhibit) collection of statistics for accounting, billing.

        [Agreed: need example billing and reconciliation scenarios, and need reverse charging. Need debate: IP “charge code” option, authenticable charge codes. Question: in what level of architecture do these features show up??]

      7. Must support administratively-restricted connectivity.

        May be at different layers.

        • Security constraints (IPSO)

        • Closed/partially open “user groups”

        • DNS “tailoring” (non-uniform configuration)?

        • Router configuration tables (e.g., NSFNET configuration)

        [Needs discussion.]

      8. Must support several classes of service.

        (Pick a few to start, e.g., “guaranteed bandwidth”, “bounded delay”, and figure out how they might work. What if not supportable by all networks?)

        [General agreement]

      9. Must provide for end-to-end authenticated and/or secure (private) communication.

        • Application level, so that authentication/privacy survives across application-level relay.
        • Transport level?
        • SNMP
        • Routing Protocols
        • DNS/X.500?
        • Playback-immune authentication

        [General agreement]

      10. Support host mobility.

        Initiate communications FROM “mobile” host

        => temporary binding of IP address (PPP, SLIP). EASY CASE (?).

        Receive communications when mobile (or at destination)
        => dynamic tracking of mobile address. HARD!
        Would dynamic name/address binding suffice?
        How to authenticate DNS update?
        Delay and responsiveness?

        (Some network technologies make it easy).

        [Timescale is an issue. Maybe not at high speed? (Rate of change of connectivity is the big issue). What about military applications?]

    3.2 Christian Huitema

      Huitema saw the biggest problem in the Internet as one of getting big, or rather, “getting wide”. Topology is moving to multiple backbones and multiple registries.

      To scale to the sizes we are considering, a fully dynamic routing process is impossible. What is needed is a directory of address to network translations and routing info. Flooding of routing information should be replaced by a route server, which can either hold pre-computed routes or compute routes as needed.

    3.3 Noel Chiappa

      Security is the key to the future evolution of the Internet. The solution to this problem will dictate the architecture of the rest of the system.

    3.4 Bob Hinden

      Hinden commented on each of the topic slides.

      1. Multi-Protocol Internet

        It would be nice to have one protocol suite, but we must live with both TCP/IP and OSI.

        A useful strategy might be to feed TCP/IP protocol developments into OSI process (e.g., BGP -> IDRP).

      2. Routing and Addressing

        • Need 1 to 2 orders of magnitude growth.

        • Addresses should be identifiers, logically distinct from routes.

        • We will have to impose a hierarchical structure to handle growth. A 3-tier topology (backbone, regional, private) is sufficient, but it must provide for arbitrary interconnections.

        • Policy: Source controlled. Backbone, regional, private networks will support distinct policies (where they provide parallel service).

        • Mobile host support would be desirable.

        • Multicasting will not be useful until there are real applications.
      3. Getting Big

        Applications are badly needed.

        • Make email good enough for commerce.
        • Desktop conferencing with video.
        • Bulletin board paradigm: it is powerful and should be exploited more.
        • Information collection (Knowbots?)
        • Video retrieval and libraries.
        • Distributed simulation.
      4. Divestiture

        • Does not believe common carriers will provide universal service (“the Cheriton conjecture”); we will still need to do internetting.

        • Need accounting, not billing.
      5. New Services

        Video is very important.

      6. Security

        The network needs to protect itself: control protocols need security.

        The network should provide an authentication service. All other security needed by an application can be end-to-end.

    3.5 Russ Hobby

      Hobby emphasized the need for new applications. Tools are needed for building distributed applications, including RPC and standard presentation formats. Both personal communication and “virtual computer” applications need work. There is a pressing need to recruit a set of experts and secure funding for them.

    3.6 Joyce Reynolds

      Reynolds enumerated a list of needed user services. There is a need to international coordination and for more publicity. A network information services infrastructure and yellow pages are needed. Issues of copyright and intellectual property need to be explored.

    3.7 Dave Crocker

      Crocker identified the need for upper layer development. There is a missing skill set in the IETF, presentation and applications development. There is a need to begin hiding the complexity of the network.

    3.8 Tony Lauck

      Lauck presented many points.

      1. Architecture is more than the protocols, it is addressing.

      2. Relays are a necessary evil, because of history, pragmatics, and especially corporate security policies. Better Internet security will result in fewer relays. The IAB should work to limit the growth of relays.

      3. There is not chance to constrain the development of multiple protocol suites; they are here today. Beware of problems of testing interoperability, with exponential combinations at various layers.

      4. The size of the Internet is not a big issue. 10**9? 10**11? 10**12?

      5. In large networks, addresses, routes, and topology must be related for reasonable performance — log(n) vs. n. Hierarchy is sub-optimal, but at least it is possible, and will allow the construction of large networks.

      6. Policy routing is all solutions with no questions.

      7. Support for mobile hosts is needed, to make them more useful for personal work.

      8. Multicast has marginal value, could be dangerous.

      9. Phase out fragmentation, it’s a mistake in IP that OSI copied.

      10. The network should support devices ranging from small thermostats to large supercomputers.

      11. Charging is important because without it there is little motivation to develop new applications. The ban on commercial use also restricts innovation.

      12. Must have controls for limited sharing of links. Hard problem is to keep this simple.

      13. Transaction processing standards are complex and farther along in OSI.

      14. Distributed processing is coming (slowly) in OSI. We should work with existing efforts in these applications.

      15. End node cannot be the only point for security. Mis- configuration is a real danger and the Internet should be able to defend itself.

      16. Global authentication is most important part of distributed processing.

    3.9 Ross Callon

      Callon discussed the coexistence of multiple protocol suites, starting from a series of questions:

      1. What is meta-architecture for a multi-protocol Internet?

      2. Does the concept of a “pure suite” exist? For example, the Internet includes other defacto standards like NFS and Postscript.

      3. Might it make sense to fill the holes in one suite using protocols from another suite?

      4. This does not break the notion of distinct TCP/IP and OSI protocol suites, but it might be a good idea to break it.

      The idea of merely sharing the links and letting the rest of the protocol stack be different defeats interoperability. He proposed to chip away at the differences by sharing: routing, user agents, directories (DNS-X.500 merge), mail protocols (SMTP exchange of X.400 format), ODA and RDI, and EDI. This sharing would unify the architecture, save some effort, and enhance interoperability.

    3.10 Lyman Chapin

      The Internet will change with the introduction of commercial carriers.

      A multi-protocol-suite Internet is currently a necessity, although this is not best architectural choice. OSI efforts really need the input of the IETF community. There is the very real possibility that the IETF can have profound impact on the course of OSI protocols.

      Chapin summarized the possibilities in the following diagram:

               _______                    |
              |  TCP  |---------------------->
              |_______|         |         |
                          ______|____     |
                         |"new stuff"|    |  "Future"
                         |___________|    |
                                |         |
               _______          V         |
              |  OSI  |---------------------->
              |_______|                   |

    3.11 Steve Kent

      Kent offered ideas on the internet security architecture.

      1. Do we put security in only the endpoints? “Hosts will always be the best defense or the weakest link”.

      2. Site administrators erect perimeter defenses; architecture needs to include them. Now that hosts are being managed by users, managers are increasingly unable to administer individual computers, so they use using perimeter defense.

      3. Need both end security services and also some functions in intermediate system, e.g., accounting and billing.

      4. Security is ultimately linked to routing and addressing.

      5. He dislikes application level relays, and there are also some security problems. Where does security go in the protocol stack? In the application there is too much duplication, and presentation syntax is a problem if security is in the applications.

      6. Global authentication would be a Good Thing.


    Clark led a final high-level wrap up. He saw three alternative futures:

    1. Relays dominate the world. X.400 becomes the only ubiquitous protocol, while IP/CLNP are used only locally. X.400 and X.500 become generalized to accommodate other applications.

      Clark rejects this as the “only” solution.

    2. Commercial carriers dominate. Routing is handled entirely inside the common carriers; this is the “Cheriton Conjecture”.

      We must accept this as an ultimate possibility.

    3. Heterogeneity dominates. Can it be global?

    The group felt a need to build a future that accommodates these diverse visions, even if the complex solution ends up not being needed. The IAB is in a position to influence the future, and should work towards the preferable outcomes.

    The IAB felt that vision 1 is a nightmare. However, it will exist to a limited extent, so application level gateways should be architected into the system. Vision 2 is a possibility the IAB must deal with. Vision 3 is the most general, and constitutes the basis for a plan.

    Further discussion is needed, and the IAB planned an “architectural summit”. There was lots of interest in an architecture summit. Participation will be limited to the IAB and IESG and all participants should come prepared with papers. This is tentatively scheduled for June 11-13, 1991.

APPENDIX A: Dave Clark Introduction

    Slide 1




    IAB/IESG — Jan 1990


    David D. Clark

    Slide 2



    • Establish a common frame of understanding for IAB, IESG and the Internet community.

    • Understand the set of problems to be solved.

    • Understand the range of solutions open to us.

    • Draw some conclusions, or else “meta-conclusions”.

    Slide 3


    We have two different goals:

    • Make it possible to build “The Internet”
    • Define a protocol suite called Internet

    Claim: These goals have very different implications. The protocols are but a means, though a powerful one.

    Claim: If “The Internet” is to succeed and grow, it will require specific design efforts. This need will continue for at least another 10 years.

    Claim: Uncontrolled growth could lead to chaos.

    Claim: A grass-roots solution seems to be the only means to success. Top-down mandates are powerless.

    Slide 4


    1) The problem space and the solution space.

    2) A set of specific questions — discussion.

    3) Return to top-level questions — discussion.

    4) Plan for action — meta discussion.

    Try to separate functional requirements from technical approach.

    Understand how we are bounded by our problem space and our solution space.

    Is architecture anything but protocols?

    Slide 5


    Routing and addressing:

      How big, what topology, and what routing model?

    Getting big:

      User services, what technology for host and nets?

    Divestiture of the Internet:

      Accounting, controlling usage and fixing faults.

    New services:

      Video? Transactions? Distributed computing?


      End node or network? Routers or relays?

    Slide 6


    How far can we migrate from the current state?

    • Can we change the IP header (except to OSI)?
    • Can we change host requirements in mandatory ways?
    • Can we manage a long-term migration objective? – Consistent direction vs. diverse goals, funding.

    Can we assume network-level connectivity?

    • Relays are the wave of the future (?)
    • Security a key issue; along with conversion.
    • Do we need a new “relay-based” architecture?

    How “managed” can/must “The Internet” be?

    • Can we mandage or constrain connectivity?

    What protocols are we working with? One or many?

    Slide 7


    “Making the problem harder for the good of mankind.”

    Are we migrating, interoperating, or tolerating multiple protocols?

    • Not all protocol suites will have same range of functionality at the same time.
    • “The Internet” will require specific functions.

    Claim: Fundamental conflict (not religion or spite):

    • Meeting aggressive requirements for the Internet
    • Dealing with OSI migration.

    Conclusion: One protocol must “lead”, and the others must follow.

    When do we “switch” to OSI?

    Consider every following slide in this context

    Slide 8


    What is the target size of “The Internet”?

    • How do addresses and routes relate?
    • What is the model of topology?
    • What solutions are possible?

    What range of policy routing is required?

    • BGP and IDRP are two answers. What is the question?
    • Fixed classes, or variable paths?
    • Source controlled routing is a minimum.

    How seamless is the needed support for mobile hosts?

    • New address class, rebind to local address, use DNS?

    Shall we push for Internet multicast?

    Slide 9


    (Addressing and routing was on previous slide…)

    What user services will be needed in the next 10 years?

    • Can we construct a plan?
    • Do we need architectural changes?

    Is there a requirement for dealing better with ranges in speed, packet sizes, etc.

    • Policy to phase out fragmentation?

    What range of hosts (things != Unix) will we support?

    Slide 10


    The Internet is composed of parts separately managed and controlled.

    What support is needed for network charging?

    • No architecture implies bulk charges and re-billing, pay for lost packets.
    • Do we need controls to supply billing id or routing?

    Requirement: we must support links with controlled sharing. (Simple form is classes based on link id.)

    • How general?

    Is there an increased need for fault isolation? (I vote yes!)

    • How can we find managerst to talk to?
    • Do we need services in hosts?

    Slide 11


    Shall we support video and audio? Real time? What %?

    • Need to plan for input from research. What quality?
    • Target date for heads-up to vendors.

    Shall we “better” support transactions?

    • Will TCP do? VMTP? Presentation? Locking?

    What application support veneers are coming?

    • Distributed computing — will it actuall happen?
    • Information networking?

    Slide 12


    Can we persist in claiming the end-node is the only line of defense?

    • What can we do inside the network?
    • What can ask the host to do?

    Do we tolerate relays, or architect them?
    Can find a better way to construct security boundaries? Do we need global authentication?

    Do we need new host requirements:

    • Logging.
    • Authentication.
    • Management interfaces.
      • Phone number or point of reference.