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

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

Includes changes discussed, with changebars.  The internet-draft (sans c)
does not include the changebars.

===


INTERNET-DRAFT                                               W A Simpson
                                                               DayDreamer
Intended status: Standards Track                           29 March 2011


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


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 interface identifier.  When no unique MAC 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
    Provisions Relating to IETF Documents
    (http://trustee.ietf.org/license-info) in effect on the date of
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    to this document.

    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  . . . . . . . . . . . . . . . . . .   4
      SECURITY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . .   4
      NORMATIVE REFERENCES  . . . . . . . . . . . . . . . . . . . . .   5
      INFORMATIVE REFERENCES  . . . . . . . . . . . . . . . . . . . .   5
      CONTACTS  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6






























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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   |
    Media Access Control (MAC) link-layer interface identifier.  The      |
    48-bit MAC is usually 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 or other 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 unique 32-bit Magic Number.  Although only a single interface    |
    negotiation is described in the base document, it has long been       |
    understood [RFC1220] [Simpson1992] [Baker1992] that the term "unique" |
    applies across all local system interfaces.  This protects against    |
    patch-panel errors in addition to looped-back modems, to detect       |
    unexpected loopbacks of a link from an endpoint to itself.            |
    [Simpson1993] [RFC1663] [RFC1717]

    An implementation conforming with this specification MUST have        |
    different Magic Numbers for every link in a single system, and each   |
    end of every link between two peers MUST have Magic Numbers which are |
    unique to those peers.  That is, the Magic Number MUST be unique for  |
    all visible interfaces.                                               |

    Whenever such 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 identifiers 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.




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    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 10 seconds, an implementation conforming with this
    specification MUST generate a replacement System Identifier using one
    of the techniques specified above.                                    +

    The system SHOULD delay generation and transmission of this           +
    replacement System Identifier for a random amount of time between 0   +
    and MAX_GENERATION_DELAY.  Although the randomization range is        +
    specified in units of seconds, the actual randomly-chosen value       +
    SHOULD NOT be in units of whole seconds, but rather in units of the   +
    highest available timer resolution.                                   +

    This reduces the probability of synchronization with advertisements   +
    from other systems in the same IS-IS area.  If a message is received  +
    during the delay indicating the conflict was resolved by another      +
    system, the existing local System Identifier remains unchanged.


Acknowledgments

    This document parallels text originally in [RFC2153] and various      |
    other drafts.

    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.]


















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Operational Considerations


    MAX_GENERATION_DELAY                                                  +
       Default: 1 second.  This is based on an anticipated IS-IS Hello    +
       interval of no more than 4 seconds.                                +

       When Hellos are sent at a greater time interval, this MUST NOT be  +
       greater than interval/2, and SHOULD NOT be greater than            +
       interval/4.                                                        +

    Configurable System Identifier                                        +
       Default 0 (off).  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.

       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]   Callon, R., "Use of OSI IS-IS for routing in TCP/IP and   +
                dual environments", December 1990.

    [RFC1377]   Katz, D., "The PPP OSI Network Layer Control Protocol     +
                (OSINLCP)", November 1992.

    [RFC1661]   Simpson, W., Ed., "The Point-to-Point Protocol (PPP)",    +
                STD 51, July 1994.

    [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

    [Baker1992] Baker, F., "PPP Reliable and Multi-Link Transmission",    +
                Message to PPP Compression List, June 29, 1992.  Message- +
                Id: <[e-mail]>                  +

    [RFC1220]   Baker, F., "Point-to-Point Protocol extensions for        +
                bridging", April 1991.

    [RFC1663]   Rand, D., "PPP Reliable Transmission", July 1994.         |

    [RFC1717]   Sklower, K., Lloyd, B., McGregor, G., and D. Carr, "The   |
                PPP Multilink Protocol (MP)", November 1994.

    [RFC2153]   Simpson, W., "PPP Vendor Extensions", May 1997.           +

    [RFC2469]   Narten, T., and C. Burton, "A Caution On The Canonical    +
                Ordering Of Link-Layer Addresses", December 1998.

    [RFC4593]   Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to  +
                Routing Protocols", October 2006.





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    [RFC5304]   Li, T., and R. Atkinson, "IS-IS Cryptographic             +
                Authentication", October 2008.

    [RFC5342]   Eastlake 3rd, D., "IANA Considerations and IETF Protocol  +
                Usage for IEEE 802 Parameters", BCP 141, September 2008.

    [Schneier]  Schneier, B., "Applied Cryptography", John Wiley & Sons,  +
                1996.  ISBN 0-471-11709-9.                                +

    [Simpson1992]                                                         +
                Simpson, W., "where are we?", Message to IESG and others, +
                April 17, 1992.  Message-Id:                              +
                <[e-mail]>                       +

    [Simpson1993]                                                         +
                Simpson, W., "Re: Simple Multilink Proceedure for PPP -   +
                the document", Message to ietf-ppp and iplpdn mailing     +
                lists, February 21, 1993.  Message-Id:                    +
                <[e-mail]>



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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