[AG-TECH] draft-nickless-ipv4-mcast-unusable-00.txt

Wed Feb 20 15:47:28 CST 2002

I've submitted the attached Internet Draft to IETF (the deadline's coming 
up real soon now for the Minneapolis meeting, right?)

I know this is obvious to a lot of people, but I've been bit by it a couple 
of times now when applications pick an IPv4 group address that maps into 
the  01-00-5E-00-00-XX Ethernet range.  There's even a special error 
message for it on Cisco Catalyst switches.  It would sure be nice to have 
these addresses clearly marked as reserved by IANA, and to have an RFC to 
point people towards when they go select multicast addresses.

Are there any other similarly problematic ranges that I've missed?

We may also want to keep IANA from allocating AS 32768, because that GLOP 
allocation (233.128.0.0/24) is one of the bad address ranges.

=== Draft Follows ===

    Internet Draft                                           B. Nickless
    Document: draft-nickless-ipv4-mcast-unusable-       Argonne National
    00.txt                                                    Laboratory
    Expires: August 2002                                   February 2002

                   IPv4 Multicast Unusable Group Addresses

Status of this Memo

    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
    other groups may also distribute working documents as Internet-
    Drafts.

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

    The list of current Internet-Drafts can be accessed at
         http://www.ietf.org/ietf/1id-abstracts.txt

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Abstract

    Due to the mapping of IPv4 Multicast addresses to Ethernet MAC
    addresses, and the prevalence of IGMP snooping switches, certain
    addresses in the IPv4 Multicast Group Address range 224.0.0.0/4 MUST
    NOT be used.

Table of Contents

    Status of this Memo................................................1
    Abstract...........................................................1
    Conventions used in this document..................................2
    Background.........................................................2
    Group Address Restrictions.........................................2
    IANA Considerations................................................3
    Security Considerations............................................3
    Acknowledgements...................................................3
    References.........................................................3
    Author's Address...................................................3

    Nickless      Informational - Expires August 2002                1
                IPv4 Multicast Unusable Group Addresses  February 2001

Conventions used in this document

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
    document are to be interpreted as described in RFC-2119 [RFC2119].

Background

    IPv4 multicast [MCAST] is an internetwork service that allows IPv4
    datagrams sent from a source to be delivered to one or more
    interested receiver(s).  That is, a given source sends a packet the
    network with a destination address 224/4 CIDR [CIDR] range.  The
    network transports this packet to all receivers (replicated where
    necessary) that have registered their interest in receiving these
    packets.

    [MCAST] describes the mapping of IPv4 Multicast Group addresses to
    Ethernet MAC addresses, as follows:

         An IP host group address is mapped to an Ethernet multicast
         address by placing the low-order 23-bits of the IP address
         into the low-order 23 bits of the Ethernet multicast address
         01-00-5E-00-00-00 (hex).   Because there are 28 significant
         bits in an IP host group address, more than one host group
         address may map to the same Ethernet multicast address.

    Multicast group addresses in the 224.0.0.0/24 range are used for
    local subnetwork control.  This maps to the Ethernet multicast
    address range 01-00-5E-00-00-XX, where XX is 00 through FF.
    Ethernet frames within this range are always processed in the
    control plane of many popular network devices, such as IGMP-snooping
    switches.

Group Address Restrictions

    Because of the many-to-one mapping of IPv4 Multicast Group Addresses
    to Ethernet MAC addresses, it is possible to overwhelm the control
    plane of network devices by sending to group addresses that map into
    the 01-00-5E-00-00-XX (hex) range.

    The following IPv4 Multicast Group Address ranges MUST NOT be used
    in order to avoid overwhelming the control plane of network devices:

    Nickless     Informational - Expires February 2002               2
                IPv4 Multicast Unusable Group Addresses  February 2001

    224.128.0.0/24    225.0.0.0/24    225.128.0.0/24    226.0.0.0/24
    226.128.0.0/24    227.0.0.0/24    227.128.0.0/24    228.0.0.0/24
    228.128.0.0/24    229.0.0.0/24    229.128.0.0/24    230.0.0.0/24
    230.128.0.0/24    231.0.0.0/24    231.128.0.0/24    232.0.0.0/24
    232.128.0.0/24    233.0.0.0/24    233.128.0.0/24    234.0.0.0/24
    234.128.0.0/24    235.0.0.0/24    235.128.0.0/24    236.0.0.0/24
    236.128.0.0/24    237.0.0.0/24    237.128.0.0/24    238.0.0.0/24
    238.128.0.0/24    239.0.0.0/24    239.128.0.0/24

IANA Considerations

    IANA SHALL permanently reserve these IPv4 Multicast Group Address
    ranges.  These group addresses MUST NOT be allocated for any IPv4
    multicast application.

Security Considerations

    Low to moderate multicast traffic levels, using addresses within
    these IPv4 Multicast Group Address ranges, can result in severe
    denial of service on network devices that process frames with
    Ethernet MAC addresses in the 01-00-5E-00-00-XX (hex) range in the
    control plane.

Acknowledgements

    This work was supported by the Mathematical, Information, and
    Computational Sciences Division subprogram of the Office of Advanced
    Scientific Computing Research, U.S. Department of Energy, under
    Contract W-31-109-Eng-38.

References

    [RFC2119] RFC 2119: Key Words for use in RFCs to Indicate
       Requirement Levels.  S. Bradner.  March 1997.

    [MCAST] RFC 1112: Host extensions for IP multicasting. S.E. Deering.
       Aug-01-1989.

    [CIDR] RFC 1519: Classless Inter-Domain Routing (CIDR): an Address
       Assignment and Aggregation Strategy. V. Fuller, T. Li, J. Yu, K.
       Varadhan. September 1993.

Author's Address

    Bill Nickless
    Argonne National Laboratory
    9700 South Cass Avenue #221     Phone:  +1 630 252 7390
    Argonne, IL 60439               Email:  nickless at mcs.anl.gov

    Nickless     Informational - Expires February 2002               3

===
Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252 7390
PGP:0E 0F 16 80 C5 B1 69 52 E1 44 1A A5 0E 1B 74 F7     nickless at mcs.anl.gov