[Pppext] draft-simpson-isis-ppp-unique-00b

[William Allen Simpson <[e-mail]>]

Sadly, I wasn't paying attention, and didn't notice there was another
IETF meeting coming up.  So, they won't let me post this draft today.

Here it is anyway for your perusal, just in case anybody is interested!

===


INTERNET-DRAFT                                               W A Simpson
                                                               DayDreamer
Intended status: Standards Track                           17 March 2011


              Generation of Unique IS-IS System Identifiers
                    draft-simpson-isis-ppp-unique-00b


Abstract

    The IS-IS routing protocol (Intermediate System to Intermediate
    System, ISO 10589) requires unique System Identifiers at the link
    layer.  A common practice has been to use an existing IEEE 802 MAC
    link-layer address.  When no unique MAC address is available, this
    document specifies automatic generation of identifiers.  It is fully
    interoperable with systems that do not support this extension.

    Additionally, the extension automatically resolves conflicts between
    System Identifiers.

Copyright Notice

    Copyright (c) 2011 IETF Trust and the persons identified as the
    document authors. All rights reserved.

    This document is subject to BCP 78 and the IETF Trust's Legal
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    This document may not be modified, and derivative works of it may not
    be created, except to format it for publication as an RFC or to
    translate it into languages other than English.

Status of this Memo

    This Internet-Draft is submitted in full conformance with the
    provisions of BCP 78 and BCP 79.

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF). Note that other groups may also distribute working
    documents as Internet-Drafts. The list of current Internet-Drafts is
    at http://datatracker.ietf.org/drafts/current.

    Internet-Drafts are draft documents valid for a maximum of six months



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    and may be updated, replaced, or obsoleted by other documents at any
    time. It is inappropriate to use Internet-Drafts as reference
    material or to cite them other than as "work in progress."



                             Table of Contents


      1.     Introduction . . . . . . . . . . . . . . . . . . . . . .   1
         1.1       Terminology  . . . . . . . . . . . . . . . . . . .   1
      2.     Random Generation  . . . . . . . . . . . . . . . . . . .   1
         2.1       PPP Links  . . . . . . . . . . . . . . . . . . . .   2
      3.     Resolving Conflicts  . . . . . . . . . . . . . . . . . .   2
      ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . .   3
      IANA CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . .   3
      OPERATIONAL CONSIDERATIONS  . . . . . . . . . . . . . . . . . .   3
      SECURITY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . .   3
      NORMATIVE REFERENCES  . . . . . . . . . . . . . . . . . . . . .   4
      INFORMATIVE REFERENCES  . . . . . . . . . . . . . . . . . . . .   4
      CONTACTS  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5






























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1.  Introduction

    The System Identifier is 6 octets for OSI end systems, and 7 octets
    for IS-IS routers or pseudonodes.  This identifier is not required to
    be the Destination or Source of any packet.  (See [ISO10589],
    [RFC1195], and [RFC5342] for further details.)

    Typically, IS-IS implementations base the identifier on an existing 6
    octet Media Access Control (MAC) identifier defined for one of its
    link-layer interfaces.  The 48-bit MAC is composed of a 24-bit
    Organizationally Unique Identifier (OUI) followed by a 24-bit Network
    Interface Controller (NIC) specific number.

    Other systems have a configured identifier that is independent of the
    interfaces.


1.1.  Terminology

    The key words "MAY", "MUST, "MUST NOT", "OPTIONAL", "RECOMMENDED",
    "REQUIRED", "SHOULD", and "SHOULD NOT" in this document are to be
    interpreted as described in [RFC2119].



2.  Random Generation

    Some systems have only point-to-point links without any conveniently
    available MAC, and do not have a configured identifier.  This status
    might change dynamically, as hot swap interfaces are added or
    removed.

    In this case, a 48-bit System Identifier MUST be randomly generated.
    (See [RFC4086] for requirements.)

    To mitigate against potential assignment conflicts, this System
    Identifier (considered as a pseudo-MAC) MUST have both the "locally-
    assigned" and "broadcast/multicast" (group) bits set; that is, the
    least significant two bits of the most significant octet are equal to
    0x3.

    The probability of conflict is reduced to a birthday attack of the
    order N/2**23; where N is the number of systems in the same IS-IS
    area.  This is considerably less likely than a duplicate MAC (see
    below), or operating facility destruction by meteor, or an operator's
    death by lightning strike.  [Schneier]





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2.1.  PPP Links

    PPP [RFC1661] links (such as [RFC1377]) already specify negotiation
    of a 32-bit Magic Number.  As currently used in [RFC1663] and
    [RFC1990], every link in a single system MUST have different Magic
    Numbers, and each end of every link between two peers SHOULD have
    Magic Numbers which are unique to those peers.  This protects against
    patch-panel errors in addition to looped-back links.

    An implementation conforming with this specification MUST ensure this
    Magic Number is unique for all local interfaces, and also MUST be
    unique for all negotiated peer interfaces.  Whenever a Magic Number
    has been successfully negotiated, only the most significant 2 octets
    of a pseudo-OUI are randomly generated.  The selected Magic Number is
    appended after the pseudo-OUI.

    To mitigate against potential assignment conflicts, this System
    Identifier (considered as a pseudo-OUI) MUST have both the "locally-
    assigned" and "broadcast/multicast" (group) bits set; that is, the
    least significant two bits of the most significant octet are equal to
    0x3.

    The probability of conflict is considerably less than the wholly
    generated pseudo-MAC (above), as the Magic Number has already been
    determined to be locally unique.  The pseudo-OUI differentiates among
    such PPP-only systems.


3.  Resolving Conflicts

    Field experience has shown that IEEE 802 MAC addresses are frequently
    not unique.  Companies that manufacture more than 16,777,214 devices
    will often reuse the same MAC.

    Also, many companies reuse the same MAC for different product lines,
    or different speeds or types of media.  Some implementations failed
    to correctly convert the MAC to canonical form [RFC2469], resulting
    unintentional conflicts through multi-media bridges.

    If a duplicated MAC is used as a System Identifier within an IS-IS
    area, this leads to the condition colloquially called "LSR War".
    Currently, IS-IS has no method to detect or resolve such conflicts.

    After detecting a conflicting System Identifier in a neighbor, or
    receiving 3 or more IS-IS Hellos and failing to resolve participation
    in an area within 30 seconds, an implementation conforming with this
    specification MUST generate a replacement System Identifier using one
    of the techniques specified above.



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Acknowledgments

    This document parallels text originally in [RFC2153].

    James Carlson, Donald Eastlake, and Dave Katz provided background
    information and helpful comments.


IANA Considerations

    This document has no IANA actions.

    [RFC Editor: please remove this section prior to publication.]


Operational Considerations

    Although the probability of conflict with another System Identifier
    is minuscule, some implementations might not have a sufficient source
    of randomness, and could repeatedly select conflicting values.  An
    implementation conforming with this specification MUST have an option
    to statically configure the System Identifier.  Default 0 (off).

    To mitigate against potential assignment conflicts, this System
    Identifier (considered as a pseudo-MAC) MUST have the "locally-
    assigned" bit set and "broadcast/multicast" (group) bit clear; that
    is, the least significant two bits of the most significant octet are
    equal to 0x2.


Security Considerations

    These mechanisms provide protection against compromised,
    malfunctioning, or misconfigured systems [RFC4593]; spoofing attacks
    are thwarted by quickly renegotiating a replacement System
    Identifier.

    Never-the-less, [RFC5304] increases protection against maliciously
    configured conflicting System Identifiers.












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Normative References

    [ISO10589]  ISO/IEC 10589:2002, "Intermediate system to Intermediate
                system routeing information exchange protocol for use in
                conjunction with the Protocol for providing the
                Connectionless-mode Network Service (ISO 8473)"

    [RFC1195]

    [RFC1377]

    [RFC1661]

    [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, March 1997.

    [RFC4086]   Eastlake, D. (3rd), Schiller, J., and S. Crocker,
                "Randomness Requirements for Security", BCP 106, June
                2005.



Informative References

    [RFC1663]

    [RFC1990]

    [RFC2153]

    [RFC2469]

    [RFC4593]

    [RFC5304]

    [RFC5342]

    [Schneier]












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Author's Address

    Questions about this document can be directed to:

       William Allen Simpson
       DayDreamer
       Computer Systems Consulting Services
       1384 Fontaine
       Madison Heights, Michigan  48071

           [e-mail]








































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