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Network Working Group C. Partridge Request for Comments: 1726 BBN Systems and Technologies Category: Informational F. Kastenholz

                                                          FTP Software
                                                         December 1994
                  Technical Criteria for Choosing
                   IP The Next Generation (IPng)

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.


 This document was submitted to the IPng Area in response to RFC 1550.
 Publication of this document does not imply acceptance by the IPng
 Area of any ideas expressed within.  Comments should be submitted to
 the mailing list.  This RFC specifies
 criteria related to mobility for consideration in design and
 selection of the Next Generation of IP.

Table of Contents

1.        Introduction. . . . . . . . . . . . . . . . . . . . . . .  2
2.        Goals . . . . . . . . . . . . . . . . . . . . . . . . . .  3
3.        Note on Terminology . . . . . . . . . . . . . . . . . . .  4
4.        General Principles. . . . . . . . . . . . . . . . . . . .  4
  4.1     Architectural Simplicity. . . . . . . . . . . . . . . . .  4
  4.2     One Protocol to Bind Them All . . . . . . . . . . . . . .  4
  4.3     Live Long . . . . . . . . . . . . . . . . . . . . . . . .  5
  4.4     Live Long AND Prosper . . . . . . . . . . . . . . . . . .  5
  4.5     Co-operative Anarchy. . . . . . . . . . . . . . . . . . .  5
5.        Criteria. . . . . . . . . . . . . . . . . . . . . . . . .  6
  5.1     Scale . . . . . . . . . . . . . . . . . . . . . . . . . .  7
  5.2     Topological Flexibility . . . . . . . . . . . . . . . . .  8
  5.3     Performance . . . . . . . . . . . . . . . . . . . . . . .  9
  5.4     Robust Service. . . . . . . . . . . . . . . . . . . . . . 10
  5.5     Transition. . . . . . . . . . . . . . . . . . . . . . . . 12
  5.6     Media Independence. . . . . . . . . . . . . . . . . . . . 13
  5.7     Unreliable Datagram Service . . . . . . . . . . . . . . . 15
  5.8     Configuration, Administration, and Operation. . . . . . . 16
  5.9     Secure Operation. . . . . . . . . . . . . . . . . . . . . 17
  5.10    Unique Naming . . . . . . . . . . . . . . . . . . . . . . 18
  5.11    Access. . . . . . . . . . . . . . . . . . . . . . . . . . 19
  5.12    Multicast . . . . . . . . . . . . . . . . . . . . . . . . 20

Partridge and Kastenholz [Page 1] RFC 1726 IPng Technical Criteria December 1994

  5.13    Extensibility . . . . . . . . . . . . . . . . . . . . . . 21
  5.13.1  Algorithms. . . . . . . . . . . . . . . . . . . . . . . . 22
  5.13.2  Headers . . . . . . . . . . . . . . . . . . . . . . . . . 22
  5.13.3  Data Structures . . . . . . . . . . . . . . . . . . . . . 22
  5.13.4  Packets . . . . . . . . . . . . . . . . . . . . . . . . . 22
  5.14    Network Service . . . . . . . . . . . . . . . . . . . . . 22
  5.15    Support for Mobility. . . . . . . . . . . . . . . . . . . 24
  5.16    Control Protocol. . . . . . . . . . . . . . . . . . . . . 25
  5.17    Private Networks. . . . . . . . . . . . . . . . . . . . . 25
6.        Things We Chose Not to Require. . . . . . . . . . . . . . 26
  6.1     Fragmentation . . . . . . . . . . . . . . . . . . . . . . 26
  6.2     IP Header Checksum. . . . . . . . . . . . . . . . . . . . 26
  6.3     Firewalls . . . . . . . . . . . . . . . . . . . . . . . . 27
  6.4     Network Management. . . . . . . . . . . . . . . . . . . . 27
  6.5     Accounting. . . . . . . . . . . . . . . . . . . . . . . . 27
  6.6     Routing . . . . . . . . . . . . . . . . . . . . . . . . . 27
  6.6.1   Scale . . . . . . . . . . . . . . . . . . . . . . . . . . 28
  6.6.2   Policy. . . . . . . . . . . . . . . . . . . . . . . . . . 28
  6.6.3   QOS . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
  6.6.4   Feedback. . . . . . . . . . . . . . . . . . . . . . . . . 28
  6.6.5   Stability . . . . . . . . . . . . . . . . . . . . . . . . 28
  6.6.6   Multicast . . . . . . . . . . . . . . . . . . . . . . . . 29
7.       References . . . . . . . . . . . . . . . . . . . . . . . . 29
8.        Security Considerations . . . . . . . . . . . . . . . . . 30
9.        Acknowledgements. . . . . . . . . . . . . . . . . . . . . 30

10. Authors' Addresses. . . . . . . . . . . . . . . . . . . . 31

1. Introduction

 This version of this memo was commissioned by the IPng area of the
 IETF in order to define a set of criteria to be used in evaluating
 the protocols being proposed for adoption as the next generation of
 The criteria presented here were culled from several sources,
 including "IP Version 7" [1], "IESG Deliberations on Routing and
 Addressing" [2], "Towards the Future Internet Architecture" [3], the
 IPng Requirements BOF held at the Washington D.C. IETF Meeting in
 December of 1992, the IPng Working Group meeting at the Seattle IETF
 meeting in March 1994, the discussions held on the Big-Internet
 mailing list (, send requests to join to, discussions with the IPng Area
 Directors and Directorate, and the mailing lists devoted to the
 individual IPng efforts.
 This document presumes that a new IP-layer protocol is actually
 desired. There is some discussion in the community as to whether we
 can extend the life of IPv4 for a significant amount of time by

Partridge and Kastenholz [Page 2] RFC 1726 IPng Technical Criteria December 1994

 better engineering of, e.g., routing protocols, or we should develop
 IPng now.  This question is not addressed in this document.
 We would like to gratefully acknowledge the assistance of literally
 hundreds of people who shared their views and insights with us.
 However, this memo is solely the personal opinion of the authors and
 in no way represents, nor should it be construed as representing, the
 opinion of the ISOC, the IAB, the IRTF, the IESG, the IETF, the
 Internet community as a whole, nor the authors' respective employers.

2. Goals

 We believe that by developing a list of criteria for evaluating
 proposals for IP The Next Generation (IPng), the IETF will make it
 easier for developers of proposals to prioritize their work and
 efforts and make reasoned choices as to where they should spend
 relatively more and less time.  Furthermore, a list of criteria may
 help the IETF community determine which proposals are serious
 contenders for a next generation IP, and which proposals are
 insufficient to the task.  Note that these criteria are probably not
 sufficient to make final decisions about which proposal is best.
 Questions such as whether to trade a little performance (e.g.,
 packets per second routed) for slightly more functionality (e.g.,
 more flexible routing) cannot be easily addressed by a simple list of
 criteria.  However, at minimum, we believe that protocols that meet
 these criteria are capable of serving as the future IPng.
 This set of criteria originally began as an ordered list, with the
 goal of ranking the importance of various criteria.  Eventually, the
 layout evolved into the current form, where each criterion was
 presented without weighting, but a time frame, indicating
 approximately when a specific criterion, or feature of a criterion,
 should be available was added to the specification.
 We have attempted to state the criteria in the form of goals or
 requirements and not demand specific engineering solutions.  For
 example, there has been talk in the community of making route
 aggregation a requirement.  We believe that route aggregation is not,
 in and of itself, a requirement but rather one part of a solution to
 the real problem of scaling to some very large, complex topology.
 Therefore, route aggregation is NOT listed as a requirement; instead,
 the more general functional goal of having the routing scale is
 listed instead of the particular mechanism of route aggregation.
 In determining the relative timing of the various criteria, we have
 had two guiding principles.  First, IPng must offer an internetwork
 service akin to that of IPv4, but improved to handle the well-known
 and widely-understood problems of scaling the Internet architecture

Partridge and Kastenholz [Page 3] RFC 1726 IPng Technical Criteria December 1994

 to more end-points and an ever increasing range of bandwidths.
 Second, it must be desirable for users and network managers to
 upgrade their equipment to support IPng.  At a minimum, this second
 point implies that there must be a straightforward way to transition
 systems from IPv4 to IPng.  But it also strongly suggests that IPng
 should offer features that IPv4 does not; new features provide a
 motivation to deploy IPng more quickly.

3. Note on Terminology

 The existing proposals tend distinguish between end-point
 identification of, e.g., individual hosts, and topological addresses
 of network attachment points.  In this memo we do not make that
 distinction. We use the term "address" as it is currently used in
 IPv4; i.e., for both the identification of a particular endpoint or
 host AND as the topological address of a point on the network. We
 presume that if the endpoint/ address split remains, the proposals
 will make the proper distinctions with respect to the criteria
 enumerated below.

4. General Principles

4.1 Architectural Simplicity

       In anything at all, perfection is finally attained not
       when there is no longer anything to add, but when there
       is no longer anything to take away.
                                        Antoine de Saint-Exupery
 We believe that many communications functions are more appropriately
 performed at protocol layers other than the IP layer.  We see
 protocol stacks as hourglass-shaped, with IPng in the middle, or
 waist, of the hourglass.  As such, essentially all higher-layer
 protocols make use of and rely upon IPng.  Similarly IPng, by virtue
 of its position in the "protocol hourglass" encompasses a wide
 variety of lower-layer protocols.  When IPng does not perform a
 particular function or provide a certain service, it should not get
 in the way of the other elements of the protocol stack which may well
 wish to perform the function.

4.2 One Protocol to Bind Them All

 One of the most important aspects of The Internet is that it provides
 global IP-layer connectivity. The IP layer provides the point of
 commonality among all of the nodes on the Internet. In effect, the
 main goal of the Internet is to provide an IP Connectivity Service to
 all who wish it.

Partridge and Kastenholz [Page 4] RFC 1726 IPng Technical Criteria December 1994

 This does NOT say that the Internet is a One-Protocol Internet. The
 Internet is today, and shall remain in the future, a Multi-Protocol
 Internet.  Multi-Protocol operations are required to allow for
 continued testing, experimentation, and development and because
 service providers' customers clearly want to be able to run protocols
 such as CLNP, DECNET, and Novell over their Internet connections.

4.3 Live Long

 It is very difficult to change a protocol as central to the workings
 of the Internet as IP. Even more problematic is changing such a
 protocol frequently.  This simply can not be done. We believe that it
 is impossible to expect the community to make significant, non-
 backward compatible changes to the IP layer more often than once
 every 10-15 years. In order to be conservative, we strongly urge
 protocol developers to consider what the Internet will look like in
 20 years and design their protocols to fit that vision.
 As a data point, the SNMP community has had great difficulty moving
 from SNMPv1 to SNMPv2.  Frequent changes in software are hard.

4.4 Live Long AND Prosper

 We believe that simply allowing for bigger addresses and more
 efficient routing is not enough of a benefit to encourage vendors,
 service providers, and users to switch to IPng, with its attendant
 disruptions of service, etc.  These problems can be solved much more
 simply with faster routers, balkanization of the Internet address
 space, and other hacks.
 We believe that there must be positive functional or operational
 benefits to switching to IPng.
 In other words, IPng must be able to live for a long time AND it must
 allow the Internet to prosper and to grow to serve new applications
 and user needs.

4.5 Co-operative Anarchy

 A major contributor to the Internet's success is the fact that there
 is no single, centralized, point of control or promulgator of policy
 for the entire network.  This allows individual constituents of the
 network to tailor their own networks, environments, and policies to
 suit their own needs.  The individual constituents must cooperate
 only to the degree necessary to ensure that they interoperate.

Partridge and Kastenholz [Page 5] RFC 1726 IPng Technical Criteria December 1994

 We believe that this decentralized and decoupled nature of the
 Internet must be preserved.  Only a minimum amount of centralization
 or forced cooperation will be tolerated by the community as a whole.
 We also believe that there are some tangible benefits to this
 decoupled nature. For example,
  • It is easier to experiment with new protocols and services and then

roll out intermediate and final results in a controlled fashion.

  • By eliminating a single point of control, a single point of failure

is also eliminated, making it much less likely that the entire

   network will fail.
 * It allows the administrative tasks for the network to be more
   widely distributed.
 An example of the benefits of this "Cooperative Anarchy" can be seen
 in the benefits derived from using the Domain Naming System over the
 original HOSTS.TXT system.

5. Criteria

 This section enumerates the criteria against which we suggest the IP
 The Next Generation proposals be evaluated.
 Each criterion is presented in its own section. The first paragraph
 of each section is a short, one or two sentence statement of the
 criterion.  Additional paragraphs then explain the criterion in more
 detail, clarify what it does and does not say and provide some
 indication of its relative importance.
 Also, each criterion includes a subsection called "Time Frame".  This
 is intended to give a rough indication of when the authors believe
 that the particular criterion will become "important".  We believe
 that if an element of technology is significant enough to include in
 this document then we probably understand the technology enough to
 predict how important that technology will be.  In general, these
 time frames indicate that, within the desired time frame, we should
 be able to get an understanding of how the feature will be added to a
 protocol, perhaps after discussions with the engineers doing the
 development.  Time Frame is not a deployment schedule since
 deployment schedules depend on non-technical issues, such as vendors
 determining whether a market exists, users fitting new releases into
 their systems, and so on.

Partridge and Kastenholz [Page 6] RFC 1726 IPng Technical Criteria December 1994

5.1 Scale

    The IPng Protocol must scale to allow the identification and
    addressing of at least 10**12 end systems (and preferably much
    more).  The IPng Protocol, and its associated routing protocols
    and architecture must allow for at least 10**9 individual networks
    (and preferably more).  The routing schemes must scale at a rate
    that is less than the square root of the number of constituent
    networks [10].
    The initial, motivating, purpose of the IPng effort is to allow
    the Internet to grow beyond the size constraints imposed by the
    current IPv4 addressing and routing technologies.
    Both aspects of scaling are important.  If we can't route then
    connecting all these hosts is worthless, but without connected
    hosts, there's no point in routing, so we must scale in both
    In any proposal, particular attention must be paid to describing
    the routing hierarchy, how the routing and addressing will be
    organized, how different layers of the routing interact, and the
    relationship between addressing and routing.
    Particular attention must be paid to describing what happens when
    the size of the network approaches these limits. How are network,
    forwarding, and routing performance affected? Does performance
    fall off or does the network simply stop as the limit is neared.
    This criterion is the essential problem motivating the transition
    to IPng.  If the proposed protocol does not satisfy this criteria,
    there is no point in considering it.
    We note that one of the white papers solicited for the IPng
    process [5] indicates that 10**12 end nodes is a reasonable
    estimate based on the expected number of homes in the world and
    adding two orders of magnitude for "safety".  However, this white
    paper treats each home in the world as an end-node of a world-wide
    Internet.  We believe that each home in the world will in fact be
    a network of the world-wide Internet.  Therefore, if we take [5]'s
    derivation of 10**12 as accurate, and change their assumption that
    a home will be an end-node to a home being a network, we may
    expect that there will be the need to support at least 10**12
    networks, with the possibility of supporting up to 10**15 end-

Partridge and Kastenholz [Page 7] RFC 1726 IPng Technical Criteria December 1994

 Time Frame
    Any IPng proposal should be able to show immediately that it has
    an architecture for the needed routing protocols, addressing
    schemes, abstraction techniques, algorithms, data structures, and
    so on that can support growth to the required scales.
    Actual development, specification, and deployment of the needed
    protocols can be deferred until IPng deployment has extended far
    enough to require such protocols.  A proposed IPng should be able
    to demonstrate ahead of time that it can scale as needed.

5.2 Topological Flexibility

    The routing architecture and protocols of IPng must allow for many
    different network topologies.  The routing architecture and
    protocols must not assume that the network's physical structure is
    a tree.
    As the Internet becomes ever more global and ubiquitous, it will
    develop new and different topologies. We already see cases where
    the network hierarchy is very "broad" with many subnetworks, each
    with only a few hosts and where it is very "narrow", with few
    subnetworks each with many hosts.  We can expect these and other
    topological forms in the future.  Furthermore, since we expect
    that IPng will allow for many more levels of hierarchy than are
    allowed under IPv4, we can expect very "tall" and very "short"
    topologies as well.
    Constituent organizations of the Internet should be allowed to
    structure their internal topologies in any manner they see fit.
    Within reasonable implementation limits, organizations should be
    allowed to structure their addressing in any manner.  We
    specifically wish to point out that if the network's topology or
    addressing is hierarchical, constituent organizations should be
    able to allocate to themselves as many levels of hierarchy as they
    It is very possible that the diameter of the Internet will grow to
    be extremely large; perhaps larger than 256 hops.
    Neither the current, nor the future, Internet will be physically
    structured as a tree, nor can we assume that connectivity can
    occur only between certain points in the graph.  The routing and
    addressing architectures must allow for multiply connected
    networks and be able to utilize multiple paths for any reason,
    including redundancy, load sharing, type- and quality-of-service

Partridge and Kastenholz [Page 8] RFC 1726 IPng Technical Criteria December 1994

 Time Frame
    We believe that Topological Flexibility is an inherent element of
    a protocol and therefore should be immediately demonstrable in an
    IPng proposal.

5.3 Performance

    A state of the art, commercial grade router must be able to
    process and forward IPng traffic at speeds capable of fully
    utilizing common, commercially available, high-speed media at the
    time.  Furthermore, at a minimum, a host must be able to achieve
    data transfer rates with IPng comparable to the rates achieved
    with IPv4, using similar levels of host resources.
    Network media speeds are constantly increasing.  It is essential
    that the Internet's switching elements (routers) be able to keep
    up with the media speeds.
    We limit this requirement to commercially available routers and
    media.  If some network site can obtain a particular media
    technology "off the shelf", then it should also be able to obtain
    the needed routing technology "off the shelf." One can always go
    into some laboratory or research center and find newer, faster,
    technologies for network media and for routing.  We do believe,
    however, that IPng should be routable at a speed sufficient to
    fully utilize the fastest available media, though that might
    require specially built, custom, devices.
    We expect that more and more services will be available over the
    Internet. It is not unreasonable, therefore, to expect that the
    ratio of "local" traffic (i.e., the traffic that stays on one's
    local network) to "export" traffic (i.e., traffic destined to or
    sourced from a network other than one's own local network) will
    change, and the percent of export traffic will increase.
    We note that the host performance requirement should not be taken
    to imply that IPng need only be as good as IPv4.  If an IPng
    candidate can achieve better performance with equivalent resources
    (or equivalent transfer rates with fewer resources) vis-a-vis IPv4
    then so much the better.  We also observe that many researchers
    believe that a proper IPng router should be capable of routing
    IPng traffic over links at speeds that are capable of fully
    utilizing an ATM switch on the link.

Partridge and Kastenholz [Page 9] RFC 1726 IPng Technical Criteria December 1994

    Some developments indicate that the use of very high speed point-
    to-point connections may become commonplace.  In particular, [5]
    indicates that OC-3 speeds may be widely used in the Cable TV
    Industry and there may be many OC-3 speed lines connecting to
    central switching elements.
    Processing of the IPng header, and subsequent headers (such as the
    transport header), can be made more efficient by aligning fields
    on their natural boundaries and making header lengths integral
    multiples of typical word lengths (32, 64, and 128 bits have been
    suggested) in order to preserve alignment in following headers.
    We point out that optimizing the header's fields and lengths only
    to today's processors may not be sufficient for the long term.
    Processor word and cache-line lengths, and memory widths are
    constantly increasing.  In doing header optimizations, the
    designer should predict word-widths one or two CPU generations
    into the future and optimize accordingly. If IPv4 and TCP had been
    optimized for processors common when they were designed, they
    would be very efficient for 6502s and Z-80s.
 Time Frame
    An IPng proposal must provide a plausible argument of how it will
    scale up in performance.  (Obviously no one can completely predict
    the future, but the idea is to illustrate that if technology
    trends in processor performance and memory performance continue,
    and perhaps using techniques like parallelism, there is reason to
    believe the proposed IPng will scale as technology scales).

5.4 Robust Service

    The network service and its associated routing and control
    protocols must be robust.
    Murphy's Law applies to networking.  Any proposed IPng protocol
    must be well-behaved in the face of malformed packets, mis-
    information, and occasional failures of links, routers and hosts.
    IPng should perform gracefully in response to willful management
    and configuration mistakes (i.e., service outages should be
    Putting this requirement another way, IPng must make it possible
    to continue the Internet tradition of being conservative in what
    is sent, but liberal in what one is willing to receive.

Partridge and Kastenholz [Page 10] RFC 1726 IPng Technical Criteria December 1994

    We note that IPv4 is reasonably robust and any proposed IPng must
    be at least as robust as IPv4.
    Hostile attacks on the network layer and Byzantine failure modes
    must be dealt with in a safe and graceful manner.
    We note that Robust Service is, in some form, a part of security
    and vice-versa.
    The detrimental effects of failures, errors, buggy
    implementations, and misconfigurations must be localized as much
    as possible.  For example, misconfiguring a workstation's IP
    Address should not break the routing protocols.  in the event of
    misconfigurations, IPng must to be able to detect and at least
    warn, if not work around, any misconfigurations.
    Due to its size, complexity, decentralized administration, error-
    prone users and administrators, and so on, The Internet is a very
    hostile environment. If a protocol can not be used in such a
    hostile environment then it is not suitable for use in the
    Some predictions have been made that, as the Internet grows and as
    more and more technically less-sophisticated sites get connected,
    there will be more failures in the network.  These failures may be
    a combination of simple size; if the size of the network goes up
    by a factor of n, then the total number of failures in the network
    can be expected to increase by some function of n.  Also, as the
    network's users become less sophisticated, it can be assumed that
    they will make more, innocent and well meaning, mistakes, either
    in configuration or use of their systems.
    The IPng protocols should be able to continue operating in an
    environment that suffers more, total, outages than we are
    currently used to.  Similarly, the protocols must protect the
    general population from errors (either of omission or commission)
    made by individual users and sites.
 Time Frame
    We believe that the elements of Robust Service should be available
    immediately in the protocol with two exceptions.
    The security aspects of Robust Service are, in fact, described
    elsewhere in this document.

Partridge and Kastenholz [Page 11] RFC 1726 IPng Technical Criteria December 1994

    Protection against Byzantine failure modes is not needed
    immediately.  A proposed architecture for it should be done
    immediately.  Prototype development should be completed in 12-18
    months, with final deployment as needed.

5.5 Transition

    The protocol must have a straightforward transition plan from the
    current IPv4.
    A smooth, orderly, transition from IPv4 to IPng is needed.  If we
    can't transition to the new protocol, then no matter how wonderful
    it is, we'll never get to it.
    We believe that it is not possible to have a "flag-day" form of
    transition in which all hosts and routers must change over at
    once. The size, complexity, and distributed administration of the
    Internet make such a cutover impossible.
    Rather, IPng will need to co-exist with IPv4 for some period of
    time.  There are a number of ways to achieve this co-existence
    such as requiring hosts to support two stacks, converting between
    protocols, or using backward compatible extensions to IPv4.  Each
    scheme has its strengths and weaknesses, which have to be weighed.
    Furthermore, we note that, in all probability, there will be IPv4
    hosts on the Internet effectively forever.  IPng must provide
    mechanisms to allow these hosts to communicate, even after IPng
    has become the dominant network layer protocol in the Internet.
    The absence of a rational and well-defined transition plan is not
    acceptable.  Indeed, the difficulty of running a network that is
    transitioning from IPv4 to IPng must be minimized.  (A good target
    is that running a mixed IPv4-IPng network should be no more and
    preferably less difficult than running IPv4 in parallel with
    existing non-IP protocols).
    Furthermore, a network in transition must still be robust.  IPng
    schemes which maximize stability and connectivity in mixed IPv4-
    IPng networks are preferred.
    Finally, IPng is expected to evolve over time and therefore, it
    must be possible to have multiple versions of IPng, some in
    production use, some in experimental, developmental, or evaluation
    use, to coexist on the network.  Transition plans must address
    this issue.

Partridge and Kastenholz [Page 12] RFC 1726 IPng Technical Criteria December 1994

    The transition plan must address the following general areas of
    the Internet's infrastructure:
       Host Protocols and Software
       Router Protocols and Software
       Security and Authentication
       Domain Name System
       Network Management
       Operations Tools (e.g., Ping and Traceroute)
       Operations and Administration procedures
    The impact on protocols which use IP addresses as data (e.g., DNS,
    distributed file systems, SNMP and FTP) must be specifically
    The transition plan should address the issue of cost distribution.
    That is, it should identify what tasks are required of the service
    providers, of the end users, of the backbones and so on.
 Time Frame
    A transition plan is required immediately.

5.6 Media Independence

    The protocol must work across an internetwork of many different
    LAN, MAN, and WAN media, with individual link speeds ranging from
    a ones-of-bits per second to hundreds of gigabits per second.
    Multiple-access and point-to-point media must be supported, as
    must media supporting both switched and permanent circuits.
    The joy of IP is that it works over just about anything.  This
    generality must be preserved.  The ease of adding new
    technologies, and ability to continue operating with old
    technologies must be maintained.
    We believe this range of speed is right for the next twenty years,
    though we may wish to require terabit performance at the high-end.
    We believe that, at a minimum, media running at 500 gigabits per
    second will be commonly available within 10 years.  The low end of
    the link-speed range is based on the speed of systems like pagers
    and ELF (ELF connects to submerged submarines and has a "speed" on
    the order of <10 characters per second).
    By switched circuits we mean both "permanent" connections such as
    X.25 and Frame Relay services AND "temporary" types of dialup
    connections similar to today's SLIP and dialup PPP services, and

Partridge and Kastenholz [Page 13] RFC 1726 IPng Technical Criteria December 1994

    perhaps, ATM SVCs.  The latter form of connection implies that
    dynamic network access (i.e., the ability to unplug a machine,
    move it to a different point on the network topology, and plug it
    back in, possibly with a changed IPng address) is required. We
    note that this is an aspect of mobility.
    By work, we mean we have hopes that a stream of IPng datagrams
    (whether from one source, or many) can come close to filling the
    link at high speeds, but also scales gracefully to low speeds.
    Many network media are multi-protocol.  It is essential that IPng
    be able to peacefully co-exist on such media with other protocols.
    Routers and hosts must be able to discriminate among the protocols
    that might be present on such a medium.  For example, on an
    Ethernet, a specific, IPng Ethernet Type value might be called
    for; or the old IPv4 Ethernet type is used and the first four
    (version number in the old IPv4 header) bits would distinguish
    between IPv4 and IPng.
    Different media have different MAC address formats and schemes.
    It must be possible for a node to dynamically determine the MAC
    address of a node given that node's IP address.  We explicitly
    prohibit using static, manually configured mappings as the
    standard approach.
    Another aspect of this criterion is that many different MTUs will
    be found in an IPng internetwork.  An IPng must be able to operate
    in such a multi-MTU environment.  It must be able to adapt to the
    MTUs of the physical media over which it operates.  Two possible
    techniques for dealing with this are path MTU discovery and
    fragmentation and reassembly; other techniques might certainly be
    We note that, as of this writing (mid 1994), ATM seems to be set
    to become a major network media technology.  Any IPng should be
    designed to operate over ATM.  However, IPng still must be able to
    operate over other, more "traditional" network media.
    Furthermore, a host on an ATM network must be able to interoperate
    with a host on another, non-ATM, medium, with no more difficulty
    or complexity than hosts on different media can interoperate today
    using IPv4.
    IPng must be able to deal both with "dumb" media, such as we have
    today, and newer, more intelligent, media.  In particular, IPng
    functions must be able to exist harmoniously with lower-layer
    realizations of the same, or similar, functions. Routing and
    resource management are two areas where designers should pay
    particular attention.  Some subnetwork technologies may include

Partridge and Kastenholz [Page 14] RFC 1726 IPng Technical Criteria December 1994

    integral accounting and billing capabilities, and IPng must
    provide the correct control information to such subnetworks.
 Time Frame
    Specifications for current media encapsulations (i.e., all
    encapsulations that are currently Proposed standards, or higher,
    in the IETF) are required immediately.  These specifications must
    include any auxiliary protocols needed (such as an address
    resolution mechanism for Ethernet or the link control protocol for
    PPP).  A general 'guide' should also be available immediately to
    help others develop additional media encapsulations.  Other,
    newer, encapsulations can be developed as the need becomes
    Van Jacobson-like header compression should be shown immediately,
    as should any other aspects of very-low-speed media.  Similarly,
    any specific aspects of high-speed media should be shown

5.7 Unreliable Datagram Service

    The protocol must support an unreliable datagram delivery service.
    We like IP's datagram service and it seems to work very well.  So
    we must keep it.  In particular, the ability, within IPv4, to send
    an independent datagram, without prearrangement, is extremely
    valuable (in fact, may be required for some applications such as
    SNMP) and must be retained.
    Furthermore, the design principle that says that we can take any
    datagram and throw it away with no warning or other action, or
    take any router and turn it off with no warning, and have datagram
    traffic still work, is very powerful.  This vastly enhances the
    robustness of the network and vastly eases administration and
    maintenance of the network.  It also vastly simplifies the design
    and implementation of software [14].
    Furthermore, the Unreliable Datagram Service should support some
    minimal level of service; something that is approximately
    equivalent to IPv4 service.  This has two functions; it eases the
    task of IPv4/IPng translating systems in mapping IPv4 traffic to
    IPng and vice versa, and it simplifies the task of fitting IPng
    into small, limited environments such as boot ROMs.
 Time Frame
    Unreliable Datagram Service must be available immediately.

Partridge and Kastenholz [Page 15] RFC 1726 IPng Technical Criteria December 1994

5.8 Configuration, Administration, and Operation

    The protocol must permit easy and largely distributed
    configuration and operation. Automatic configuration of hosts and
    routers is required.
    People complain that IP is hard to manage.  We cannot plug and
    play.  We must fix that problem.
    We do note that fully automated configuration, especially for
    large, complex networks, is still a topic of research.  Our
    concern is mostly for small and medium sized, less complex,
    networks; places where the essential knowledge and skills would
    not be as readily available.
    In dealing with this criterion, address assignment and delegation
    procedures and restrictions should be addressed by the proposal.
    Furthermore, "ownership" of addresses (e.g., user or service
    provider) has recently become a concern and the issue should be
    We require that a node be able to dynamically obtain all of its
    operational, IP-level parameters at boot time via a dynamic
    configuration mechanism.
    A host must be able to dynamically discover routers on the host's
    local network.  Ideally, the information which a host learns via
    this mechanism would also allow the host to make a rational
    selection of which first-hop router to send any given packet to.
    IPng must not mandate that users or administrators manually
    configure first-hop routers into hosts.
    Also, a strength of IPv4 has been its ability to be used on
    isolated subnets.  IPng hosts must be able to work on networks
    without routers present.
    Additional elements of this criterion are:
  • Ease of address allocation.
  • Ease of changing the topology of the network within a particular

routing domain.

  • Ease of changing network provider.
  • Ease of (re)configuring host/endpoint parameters such as

addressing and identification.

  • Ease of (re)configuring router parameters such as addressing and


Partridge and Kastenholz [Page 16] RFC 1726 IPng Technical Criteria December 1994

  • Address allocation and assignment authority must be delegated as

far 'down' the administrative hierarchy as possible.

    The requirements of this section apply only to IPng and its
    supporting protocols (such as for routing, address resolution, and
    network-layer control).  Specifically, as far as IPng is
    concerned, we are concerned only with how routers and hosts get
    their configuration information.
    We note that in general, automatic configuration of hosts is a
    large and complex problem and getting the configuration
    information into hosts and routers is only one, small, piece of
    the problem.  A large amount of additional, non-Internet-layer
    work is needed in order to be able to do "plug-and-play"
    networking.  Other aspects of "plug-and-play" networking include
    things like: Autoregistration of new nodes with DNS, configuring
    security service systems (e.g., Kerberos), setting up email relays
    and mail servers, locating network resources, adding entries to
    NFS export files, and so on.  To a large degree, these
    capabilities do not have any dependence on the IPng protocol
    (other than, perhaps, the format of addresses).
    We require that any IPng proposal not impede or prevent, in any
    way, the development of "plug-and-play" network configuration
    Automatic configuration of network nodes must not prevent users or
    administrators from also being able to manually configure their
 Time Frame
    A method for plug and play on small subnets is immediately
    We believe that this is an extremely critical area for any IPng as
    a major complaint of the IP community as a whole is the difficulty
    in administering large IP networks.  Furthermore, ease of
    installation is likely to speed the deployment of IPng.

5.9 Secure Operation

    IPng must provide a secure network layer.
    We need to be sure that we have not created a network that is a
    cracker's playground.

Partridge and Kastenholz [Page 17] RFC 1726 IPng Technical Criteria December 1994

    In order to meet the Robustness criterion, some elements of what
    is commonly shrugged off as "security" are needed; e.g., to prevent
    a villain from injecting bogus routing packets, and destroying the
    routing system within the network.  This criterion covers those
    aspects of security that are not needed to provide the Robustness
    Another aspect of security is non-repudiation of origin.  In order
    to adequately support the expected need for simple accounting, we
    believe that this is a necessary feature.
    In order to safely support requirements of the commercial world,
    IPng-level security must have capabilities to prevent
    eavesdroppers from monitoring traffic and deducing traffic
    patterns.  This is particularly important in multi-access networks
    such as cable TV networks [5].
    Aspects of security at the IP level to be considered include:
  • Denial of service protections [6],
  • Continuity of operations [6],
  • Precedence and preemption [6],
  • Ability to allow rule-based access control technologies [6]
  • Protection of routing and control-protocol operations [9],
  • Authentication of routing information exchanges, packets, data,

and sources (e.g., make sure that the routing packet came from a

      router) [9],
    * QOS security (i.e., protection against improper use of network-
      layer resources, functions, and capabilities),
    * Auto-configuration protocol operations in that the host must be
      assured that it is getting its information from proper sources,
    * Traffic pattern confidentiality is strongly desired by several
      communities [9] and [5].
 Time Frame
    Security should be an integral component of any IPng from the

5.10 Unique Naming

    IPng must assign all IP-Layer objects in the global, ubiquitous,
    Internet unique names.  These names may or may not have any
    location, topology, or routing significance.
    We use the term "Name" in this criterion synonymously with the
    term "End Point Identifier" as used in the NIMROD proposal, or as

Partridge and Kastenholz [Page 18] RFC 1726 IPng Technical Criteria December 1994

    IP Addresses uniquely identify interfaces/hosts in IPv4.  These
    names may or may not carry any routing or topology information.
    See [11] for more discussion on this topic.
    IPng must provide identifiers which are suitable for use as
    globally unique, unambiguous, and ubiquitous names for endpoints,
    nodes, interfaces, and the like.  Every datagram must carry the
    identifier of both its source and its destination (or some method
    must be available to determine these identifiers, given a
    datagram).  We believe that this is required in order to support
    certain accounting functions.
    Other functions and uses of unique names are:
  • To uniquely identify endpoints (thus if the unique name and

address are not the same, the TCP pseudo-header should include

      the unique name rather than the address)
    * To allow endpoints to change topological location on the network
      (e.g., migrate) without changing their unique names.
    * To give one or more unique names to a node on the network (i.e.,
      one node may have multiple unique names)
    An identifier must refer to one and only one object while that
    object is in existence.  Furthermore, after an object ceases to
    exist, the identifier should be kept unused long enough to ensure
    that any packets containing the identifier have drained out of the
    Internet system, and that other references to the identifier have
    probably been lost.  We note that the term "existence" is as much
    an administrative issue as a technical one.  For example, if a
    workstation is reassigned, given a new IP address and node name,
    and attached to a new subnetwork, is it the same object or not.
    This does argue for a namespace that is relatively large and
    relatively stable.
 Time Frame
    We see this as a fundamental element of the IP layer and it should
    be in the protocol from the beginning.

5.11 Access

    The protocols that define IPng, its associated protocols (similar
    to ARP and ICMP in IPv4) and the routing protocols (as in OSPF,
    BGP, and RIP for IPv4) must be published as standards track RFCs
    and must satisfy the requirements specified in RFC1310.  These
    documents should be as freely available and redistributable as the
    IPv4 and related RFCs.  There must be no specification-related
    licensing fees for implementing or selling IPng software.

Partridge and Kastenholz [Page 19] RFC 1726 IPng Technical Criteria December 1994

    An essential aspect of the development of the Internet and its
    protocols has been the fact that the protocol specifications are
    freely available to anyone who wishes a copy.  Beyond simply
    minimizing the cost of learning about the technology, the free
    access to specifications has made it easy for researchers and
    developers to easily incorporate portions of old protocol
    specifications in the revised specifications.  This type of easy
    access to the standards documents is required for IPng.
 Time Frame
    An IPng and its related protocols must meet these standards for
    openness before an IPng can be approved.

5.12 Multicast

    The protocol must support both unicast and multicast packet
    transmission.  Part of the multicast capability is a requirement
    to be able to send to "all IP hosts on a given subnetwork".
    Dynamic and automatic routing of multicasts is also required.
    IPv4 has made heavy use of the ability to multicast requests to
    all IPv4 hosts on a subnet, especially for autoconfiguration.
    This ability must be retained in IPng.
    Unfortunately, IPv4 currently uses the local media broadcast
    address to multicast to all IP hosts.  This behavior is anti-
    social in mixed-protocol networks and should be fixed in IPng.
    There's no good reason for IPng to send to all hosts on a subnet
    when it only wishes to send to all IPng hosts.  The protocol must
    make allowances for media that do not support true multicasting.
    In the past few years, we have begun to deploy support for wide-
    area multicast addressing in the Internet, and it has proved
    valuable.  This capability must not be lost in the transition to
    The ability to restrict the range of a multicast to specific
    networks is also important.  Furthermore, it must be possible to
    "selectively" multicast packets. That is, it must be possible to
    send a multicast to a remote, specific portion or area of the
    Internet (such as a specific network or subnetwork) and then have
    that multicast limited to just that specific area.  Furthermore,
    any given network or subnetwork should be capable of supporting
    2**16 "local" multicast groups, i.e., groups that are not
    propagated to other networks.  See [8].

Partridge and Kastenholz [Page 20] RFC 1726 IPng Technical Criteria December 1994

    It should be noted that addressing -- specifically the syntax and
    semantics of addresses -- has a great impact on the scalability of
    the architecture.
    Currently, large-scale multicasts are routed manually through the
    Internet.  While this is fine for experiments, a "production"
    system requires that multicast-routing be dynamic and automatic.
    Multicast groups must be able to be created and destroyed, hosts
    must be able to join and leave multicast groups and the network
    routing infrastructure must be able to locate new multicast groups
    and destinations and route traffic to those destinations all
    without manual intervention.
    Large, topologically dispersed, multicast groups (with up to 10**6
    participants) must be supported.  Some applications are given in
 Time Frame
    Obviously, address formats, algorithms for processing and
    interpreting the multicast addresses must be immediately available
    in IPng.  Broadcast and Multicast transmission/reception of
    packets are required immediately.  Dynamic routing of multicast
    packets must be available within 18 months.
    We believe that Multicast Addressing is vital to support future
    applications such as remote conferencing.  It is also used quite
    heavily in the current Internet for things like service location
    and routing.

5.13 Extensibility

    The protocol must be extensible; it must be able to evolve to meet
    the future service needs of the Internet. This evolution must be
    achievable without requiring network-wide software upgrades.  IPng
    is expected to evolve over time. As it evolves, it must be able to
    allow different versions to coexist on the same network.
    We do not today know all of the things that we will want the
    Internet to be able to do 10 years from now.  At the same time, it
    is not reasonable to ask users to transition to a new protocol
    with each passing decade.  Thus, we believe that it must be
    possible to extend IPng to support new services and facilities.
    Furthermore, it is essential that any extensions can be
    incrementally deployed to only those systems which desire to use
    them. Systems upgraded in this fashion must still be able to
    communicate with systems which have not been so upgraded.

Partridge and Kastenholz [Page 21] RFC 1726 IPng Technical Criteria December 1994

    There are several aspects to extensibility:
 5.13.1 Algorithms
       The algorithms used in processing IPng information should be
       decoupled from the protocol itself.  It should be possible to
       change these algorithms without necessarily requiring protocol,
       datastructure, or header changes.
 5.13.2 Headers
       The content of packet headers should be extensible.  As more
       features and functions are required of IPng, it may be
       necessary to add more information to the IPng headers.  We note
       that for IPv4, the use of options has proven less than entirely
       satisfactory since options have tended to be inefficient to
 5.13.3 Data Structures
       The fundamental data structures of IPng should not be bound
       with the other elements of the protocol.  E.g., things like
       address formats should not be intimately tied with the routing
       and forwarding algorithms in the way that the IPv4 address
       class mechanism was tied to IPv4 routing and forwarding.
 5.13.4 Packets
       It should be possible to add additional packet-types to IPng.
       These could be for, _e._g., new control and/or monitoring
    We note that, everything else being equal, having larger,
    oversized, number spaces is preferable to having number spaces
    that are "just large enough".  Larger spaces afford more
    flexibility on the part of network designers and operators and
    allow for further experimentation on the part of the scientists,
    engineers, and developers.  See [7].
 Time Frame
    A framework showing mechanisms for extending the protocol must be
    provided immediately.

5.14 Network Service

    The protocol must allow the network (routers, intelligent media,
    hosts, and so on) to associate packets with particular service
    classes and provide them with the services specified by those

Partridge and Kastenholz [Page 22] RFC 1726 IPng Technical Criteria December 1994

    For many reasons, such as accounting, security and multimedia, it
    is desirable to treat different packets differently in the
    For example, multimedia is now on our desktop and will be an
    essential part of future networking.  So we have to find ways to
    support it; and a failure to support it may mean users choose to
    use protocols other than IPng.
    The IETF multicasts have shown that we can currently support
    multimedia over internetworks with some hitches.  If the network
    can be guaranteed to provide the necessary service levels for this
    traffic, we will dramatically increase its success.
    This criterion includes features such as policy-based routing,
    flows, resource reservation, network service technologies, type-
    of-service and quality-of-service and so on.
    In order to properly support commercial provision and use of
    Internetwork service, and account for the use of these services
    (i.e., support the economic principle of "value paid for value
    received") it must be possible to obtain guarantees of service
    levels.  Similarly, if the network can not support a previously
    guaranteed service level, it must report this to those to whom it
    guaranteed the service.
    Network service provisions must be secure.  The network-layer
    security must generally prevent one host from surreptitiously
    obtaining or disrupting the use of resources which another host
    has validly acquired.  (Some security failures are acceptable, but
    the failure rate must be very low and the rate should be
    One of the parameters of network service that may be requested
    must be cost-based.
    As far as possible, given the limitations of underlying media and
    IP's model of a robust internet datagram service, real-time,
    mission-critical applications must be supported by IPng [6].
    Users must be able to confirm that they are, in fact, getting the
    services that they have requested.
 Time Frame
    This should be available within 24 months.

Partridge and Kastenholz [Page 23] RFC 1726 IPng Technical Criteria December 1994

5.15 Support for Mobility

    The protocol must support mobile hosts, networks and
    Again, mobility is becoming increasingly important.  Look at the
    portables that everyone is carrying.  Note the strength of the
    Apple commercial showing someone automatically connecting up her
    Powerbook to her computer back in the office.  There have been a
    number of pilot projects showing ways to support mobility in IPv4.
    All have some drawbacks.  But like network service grades, if we
    can support mobility, IPng will have features that will encourage
    We use an encompassing definition of "mobility" here.  Mobility
    typically means one of two things to people: 1) Hosts that
    physically move and remain connected (via some wireless datalink)
    with sessions and transport-layer connections remaining 'open' or
    'active' and 2) Disconnecting a host from one spot in the network,
    connecting it back in another arbitrary spot and continuing to
    work.  Both forms are required.
    Reference [6] discusses possible future use of IP-based networks
    in the US Navy's ships, planes, and shore installations.  Their
    basic model is that each ship, plane and shore installation
    represents at least one IP network.  The ship- and plane-based
    networks, obviously, are mobile as these craft move around the
    world. Furthermore, most, if not all, Naval surface combatants
    carry some aircraft (at a minimum, a helicopter or two). So, not
    only must there be mobile networks (the ships that move around),
    but there must be mobile internetworks: the ships carrying the
    aircraft where each aircraft has its own network, which is
    connected to the ship's network and the whole thing is moving.
    There is also the requirement for dynamic mobility; a plane might
    take off from aircraft carrier A and land on carrier B so it
    obviously would want to "connect" to B's network.  This situation
    might be even more complex since the plane might wish to retain
    connectivity to its "home" network; that is, the plane might
    remain connected to the ship-borne networks of both aircraft
    carriers, A and B.
    These requirements are not limited to just the navy.  They apply
    to the civilian and commercial worlds as well.  For example, in
    civil airliners, commercial cargo and passenger ships, trains,
    cars and so on.

Partridge and Kastenholz [Page 24] RFC 1726 IPng Technical Criteria December 1994

 Time Frame
    The mobility algorithms are stabilizing and we would hope to see
    an IPng mobility framework within a year.

5.16 Control Protocol

    The protocol must include elementary support for testing and
    debugging networks.
    An important feature of IPv4 is the ICMP and its debugging,
    support, and control features.  Specific ICMP messages that have
    proven extraordinarily useful within IPv4 are Echo Request/Reply
    (a.k.a ping), Destination Unreachable and Redirect.  Functions
    similar to these should be in IPng.
    This criterion explicitly does not concern itself with
    configuration related messages of ICMP.  We believe that these are
    adequately covered by the configuration criterion in this memo.
    One limitation of today's ICMP that should be fixed in IPng's
    control protocol is that more than just the IPng header plus 64
    bits of a failed datagram should be returned in the error message.
    In some situations, this is too little to carry all the critical
    protocol information that indicates why a datagram failed.  At
    minimum, any IPng control protocol should return the entire IPng
    and transport headers (including options or nested headers).
 Time Frame
    Support for these functions is required immediately.

5.17 Private Networks

    IPng must allow users to build private internetworks on top of the
    basic Internet Infrastructure.  Both private IP-based
    internetworks and private non-IP-based (e.g., CLNP or AppleTalk)
    internetworks must be supported.
    In the current Internet, these capabilities are used by the
    research community to develop new IP services and capabilities
    (e.g., the MBone) and by users to interconnect non-IP islands over
    the Internet (e.g., CLNP and DecNet use in the UK).
    The capability of building networks on top of the Internet have
    been shown to be useful.  Private networks allow the Internet to

Partridge and Kastenholz [Page 25] RFC 1726 IPng Technical Criteria December 1994

    be extended and modified in ways that 1) were not foreseen by the
    original builders and 2) do not disrupt the day-to-day operations
    of other users.
    We note that, today in the IPv4 Internet, tunneling is widely used
    to provide these capabilities.
    Finally, we note that there might not be any features that
    specifically need to be added to IPng in order to support the
    desired functions (i.e., one might treat a private network protocol
    simply as another IP client protocol, just like TCP or UDP). If
    this is the case, then IPng must not prevent these functions from
    being performed.
 Time Frame
    Some of these capabilities may be required to support other
    criteria (e.g., transition) and as such, the timing of the
    specifications is governed by the other criteria (e.g., immediately
    in the case of transition).  Others may be produced as desired.

6. Things We Chose Not to Require

 This section contains items which we felt should not impact the
 choice of an IPng.  Listing an item here does not mean that a
 protocol MUST NOT do something. It means that the authors do not
 believe that it matters whether the feature is in the protocol or
 not. If a protocol includes one of the items listed here, that's
 cool. If it doesn't; that's cool too. A feature might be necessary in
 order to meet some other criterion.  Our point is merely that the
 feature need not be required for its own sake.

6.1 Fragmentation

 The technology exists for path MTU discovery.  Presumably, IPng will
 continue to provide this technology.  Therefore, we believe that IPng
 Fragmentation and Reassembly, as provided in IPv4, is not necessary.
 We note that fragmentation has been shown to be detrimental to
 network performance and strongly recommend that it be avoided.

6.2 IP Header Checksum

 There has been discussion indicating that the IP Checksum does not
 provide enough error protection to warrant its performance impact.
 The argument states that there is almost always a stronger datalink
 level CRC, and that end-to-end protection is provided by the TCP
 checksum. Therefore we believe that an IPng checksum is not required

Partridge and Kastenholz [Page 26] RFC 1726 IPng Technical Criteria December 1994

6.3 Firewalls

 Some have requested that IPng include support for firewalls.  The
 authors believe that firewalls are one particular solution to the
 problem of security and, as such, do not consider that support for
 firewalls is a valid requirement for IPng.  (At the same time, we
 would hope that no IPng is hostile to firewalls without offering some
 equivalent security solution).

6.4 Network Management

 Network Management properly is a task to be carried out by additional
 protocols and standards, such as SNMP and its MIBs.  We believe that
 network management, per se, is not an attribute of the IPng protocol.
 Furthermore, network management is viewed as a support, or service,
 function. Network management should be developed to fit IPng and not
 the other way round.

6.5 Accounting

 We believe that accounting, like network management, must be designed
 to fit the IPng protocol, and not the other way round.  Therefore,
 accounting, in and of itself, is not a requirement of IPng.  However,
 there are some facets of the protocol that have been specified to
 make accounting easier, such as non-repudiation of origin under
 security, and the unique naming requirement for sorting datagrams
 into classes.  Note that a parameter of network service that IPng
 must support is cost.

6.6 Routing

 Routing is a very critical part of the Internet.  In fact, the
 Internet Engineering Task Force has a separate Area which is
 chartered to deal only with routing issues.  This Area is separate
 from the more general Internet Area.
 We see that routing is also a critical component of IPng.  There are
 several criteria, such as Scaling, Addressing, and Network Services,
 which are intimately entwined with routing.  In order to stress the
 critical nature and importance of routing, we have chosen to devote a
 separate chapter to specifically enumerating some of the requirements
 and issues that IPng routing must address.  All of these issues, we
 believe, fall out of the general criteria presented in the previous

Partridge and Kastenholz [Page 27] RFC 1726 IPng Technical Criteria December 1994

 6.6.1 Scale
    First and foremost, the routing architecture must scale to support
    a very large Internet.  Current expectations are for an Internet
    of about 10**9 to 10**12 networks.  The routing architecture must
    be able to deal with networks of this size.  Furthermore, the
    routing architecture must be able to deal with this size without
    requiring massive, global databases and algorithms.  Such
    databases or algorithms would, in effect, be single points of
    failure in the architecture (which is not robust), and because of
    the nature of Internet administration (cooperative anarchy), it
    would be impossible to maintain the needed consistency.
 6.6.2 Policy
    Networks (both transit and non-transit) must be able to set their
    own policies for the types of traffic that they will admit.  The
    routing architecture must make these policies available to the
    network as a whole.  Furthermore, nodes must be able to select
    routes for their traffic based on the advertised policies.
 6.6.3 QOS
    A key element of the network service criteria is that differing
    applications wish to acquire differing grades of network service.
    It is essential that this service information be propagated around
    the network.
 6.6.4 Feedback
    As users select specific routes over which to send their traffic,
    they must be provided feedback from the routing architecture. This
    feedback should allow the user to determine whether the desired
    routes are actually available or not, whether the desired services
    are being provided, and so forth.
    This would allow users to modify their service requirements or
    even change their routes, as needed.
 6.6.5 Stability
    With the addition of additional data into the routing system
    (i.e., routes are based not only on connectivity, as in IPv4, but
    also on policies, service grades, and so on), the stability of the
    routes may suffer.  We offer as evidence the early ARPANET which
    experimented with load-based routing. Routes would remain in flux,
    changing from one saturated link, to another, unused, link.

Partridge and Kastenholz [Page 28] RFC 1726 IPng Technical Criteria December 1994

    This must not be allowed to happen.  If anything, routes should be
    even more stable under IPng's routing architecture than under the
    current architecture.
 6.6.6 Multicast
    Multicast will be more important in IPng than it is today in IPv4.
    Multicast groups may be very large and very distributed.
    Membership in multicast groups will be very dynamic.  The routing
    architecture must be able to cope with this.
    Furthermore, the routing architecture must be able to build
    multicast routes dynamically, based on factors such as group
    membership, member location, requested and available qualities of
    service, and so on.

7. References

 [1] Internet Architecture Board, "IP Version 7", Draft 8, Work in
     Progress, July, 1992.
 [2] Gross, P., and P. Almquist, "IESG Deliberations on Routing and
     Addressing", RFC 1380, IESG Chair, IESG Internet AD, November
 [3] Clark, D., Chapin, L., Cerf, V., Braden, R., and R. Hobby,
     "Toward the Future Internet Architecture", RFC 1287, MIT, BBN,
     CNRI, USC/Information Sciences Institute, UC Davis, December
 [4] Dave Clark's paper at SIGCOMM '88 where he pointed out that the
     design of TCP/IP was guided, in large part, by an ordered list of
 [5] Vecchi, M., "IPng Requirements: A Cable Television Industry
     Viewpoint", RFC 1686, Time Warner Cable, August 1994.
 [6] Green, D., Irey, P., Marlow, D. and K. O'Donoghue, "HPN Working
     Group Input to the IPng Requirements Solicitation, RFC 1679,
     NSWC-DD, August 1994.
 [7] Bellovin, S., "On Many Addresses per Host", RFC 1681, AT&T Bell
     Laboratories, August 1994.
 [8] Symington, S., Wood, D., and J. Pullen, "Modelling and Simulation
     Requirements for IPng", RFC 1667, Mitre Corporation and George
     Mason University, August 1994.

Partridge and Kastenholz [Page 29] RFC 1726 IPng Technical Criteria December 1994

 [9] Internet Architecture Board, "Report of the IAB Workshop on
     Security in the Internet Architecture, RFC 1636, IAB, June 1994.
[10] Private EMAIL from Tony Li to IPNG Directorate Mailing List, 18
     April 1994 18:42:05.
[11] Saltzer, J., On the Naming and Binding of Network Destinations",
     RFC 1498, M.I.T. Laboratory for Computer Science, August 1993.
[12] Postel, J., "Transmission Control Protocol - DARPA Internet
     Program Protocol Specification", STD 7, RFC 793, DARPA, September
[13] EMAIL from Robert Elz to the Big Internet mailing list,
     approximately 4 May 1994.
[14] Chiappa, N., "Nimrod and IPng Technical Requirements", Work in

8. Security Considerations

 Security is not directly addressed by this memo.  However, as this
 memo codifies goals for a new generation of network layer protocol,
 the security provided by such a protocol is addressed.  Security has
 been raised as an issue in several of the requirements stated in this
 memo.  Furthermore, a specific requirement for security has been

9. Acknowledgements

 The authors gratefully acknowledge the assistance and input provided
 by the many people who have reviewed and commented upon this

Partridge and Kastenholz [Page 30] RFC 1726 IPng Technical Criteria December 1994

10. Authors' Addresses

 Craig Partridge
 BBN Systems and Technologies
 10 Moulton St.
 Cambridge, MA 02138
 Frank Kastenholz
 FTP Software, Inc.
 2 High St.
 North Andover, MA, 01845-2620 USA

Partridge and Kastenholz [Page 31]

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