Internet Draft B. Nickless
Document: draft-nickless-ipv4-mcast-unusable- Argonne National
02.txt Laboratory
Expires: December 2003 June 2003
IPv4 Multicast Unusable Group And Source Addresses
1. 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
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The list of Internet-Draft Shadow Directories can be accessed at
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2. Abstract
Some IPv4 multicast datagrams should not be routed, either within an
administrative domain or between administrative domains. A list of
those restrictions is supplied here. These restrictions SHOULD be
respected by IPv4 multicast applications, and included in network
device access control lists.
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3. Table of Contents
1. Status of this Memo.............................................1
2. Abstract........................................................1
4. Conventions used in this document...............................2
5. Background......................................................2
6. Specific (Source,Group) Restrictions............................2
7. Unusable Locally................................................4
8. Unusable Inter-domain...........................................4
9. No Flooding of Knowledge of Active Sources......................5
9. Security Considerations.........................................6
10. Acknowledgements...............................................6
11. References.....................................................6
12. Author's Address...............................................7
4. 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].
5. 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.
Some combinations of Source Address and Group Address SHOULD NOT be
routed for various reasons. This note describes those restrictions
so they can be:
- Avoided by applications, especially those that choose multicast
groups on a random or ad-hoc basis.
- Properly reflected in network device restriction lists.
6. Specific (Source,Group) Restrictions
Following is a list of (Source,Group) ranges that should not be used
or routed in certain circumstances. Each range is associated with a
brief explanation and a cross-reference to a fuller explanation to
be found in following sections of this note.
(*,224.0.1.2/32) SGI-Dogfight Section 8.4
(*,224.0.1.3/32) Rwhod Section 8.5
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(*,224.0.1.22/32) SVRLOC Section 8.4
(*,224.0.1.22/32) Microsoft-DS Section 8.4
(*,224.0.1.35/32) SVRLOC-DA Section 8.5
(*,224.0.1.39/32) CISCO-RP-ANNOUNCE Section 8.5
(*,224.0.1.40/32) CISCO-RP-DISCOVERY Section 8.5
(*,224.0.2.2/32) SUN-RPC Section 8.4
(*,224.77.0.0/16) Norton Ghost Section 8.3
(*,224.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,225.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,225.1.2.3/32) Altiris Section 8.3
(*,225.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,226.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,226.77.0.0/16) Norton Ghost Section 8.3
(*,226.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,227.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,227.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,228.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,228.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,229.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,229.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,230.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,230.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,231.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,231.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,232.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,232.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,232.0.0.0/8) Source-Specific Multicast Section 9.1
(*,233.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,233.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,234.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,234.42.42.42/32) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,234.142.142.42/31) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.44/30) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.48/28) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.64/26) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.128/29) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.136/30) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.140/31) Phoenix/StorageSoft ImageCast Section 8.3
(*,234.142.142.142/32) Phoenix/StorageSoft ImageCast Section 8.3
(*,235.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,235.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,236.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,236.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,237.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,237.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,238.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,238.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,239.0.0.0/8) Administratively Scoped Groups Section 8.1
(*,239.0.0.0/24) Control plane of IGMP snoopers Section 7.1
(*,239.128.0.0/24) Control plane of IGMP snoopers Section 7.1
(10.0.0.0/8,*) Private Address Space Section 8.2
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(127.0.0.0/8,*) Loopback Address Space Section 8.2
(172.16.0.0/12,*) Private Address Space Section 8.2
(192.168.0.0/16,*) Private Address Space Section 8.2
7. Unusable Locally
Multicast datagrams that match the criteria in this section SHOULD
NOT be used, even on local, unrouted subnetworks.
7.1 Groups processed in the control plane of IGMP-snooping switches.
[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.
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.
8. Unusable Inter-domain
Multicast datagrams that match the criteria in this section SHOULD
NOT be routed between administrative domains.
Section 7 (Unusable Locally) is incorporated here by reference.
8.1 Administratively Scoped Addresses
RFC 2366 [ADMIN] defines 239.0.0.0/8 for use within an
administrative domain. As such, datagrams with group addresses that
match 239.0.0.0/8 SHOULD NOT be passed between administrative
domains.
8.2 Private and Loopback IPv4 Addresses
RFC 1918 [PRIVATE] defines certain ranges of IPv4 unicast addresses
that can be used within an administrative domain. Multicast
datagrams are no exception to the rule that datagrams addressed
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within these ranges SHOULD NOT be passed between administrative
domains.
127.0.0.0/8 is widely used for internal host addressing, and is
generally not valid on datagrams passed between hosts.
8.3 Personal Computer Deployment and Control Applications
The Norton Ghost [GHOST], Phoenix/StorageSoft ImageCast [IMCAST],
and Altiris [ALTIRIS] applications are used to duplicate files and
filesystems from servers to clients, and to otherwise maintain
groups of Personal Computers. They are intended to be used on a
local subnet or within an administrative domain, but the default
addresses used by the software are not within the administratively-
scoped range 239.0.0.0/8 (see Section 8.1 above).
8.4 Known Insecure Services
Applications that use certain multicast group addresses have been
demonstrated to be vulnerable to exploitation, leading to serious
security problems.
8.5 Internal Resource Discovery
Applications that use certain multicast group addresses are used to
discover resources within an administrative domain.
9. No Flooding of Knowledge of Active Sources
In the absence of explicit requests by interested receivers,
multicast datagrams that match the criteria in this section SHOULD
NOT be transmitted across administrative domain boundaries.
The knowledge of active sources that match the criteria in this
section SHOULD NOT be passed between administrative domains, for
example through the operation of the Multicast Source Discovery
Protocol (MSDP) [MSDP].
Sections 7 and 8 are incorporated here by reference.
9.1 Source-Specific Multicast
Multicast datagrams addressed within 232.0.0.0/8 (See [IANA]) are
used in the Source-Specific Multicast regime. Interested recipients
request traffic from specific sources using specific group
addresses. Knowledge of active sources is not flooded throughout
the Internet, as it is the responsibility of the application to
discover the active sources.
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9. Security Considerations
Low to moderate multicast traffic levels, using addresses within
these Section 7.1 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.
Interdomain forwarding of multicast traffic generated by certain
multicast applications (see Section 8.3) can result in internal
enterprise data being replicated far beyond that which was intended.
Interdomain forwarding of multicast traffic on certain multicast
groups (see Section 8.4) can lead to compromise of host systems.
10. Acknowledgements
The author relied heavily on a list of problematic groups maintained
by Cisco Systems, especially Beau Williamson and his colleagues.
Jay Ford and Alan Croswell provided references for the Norton Ghost
restriction.
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.
11. 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.
[ADMIN] RFC 2365: Administratively Scoped IP Multicast. D. Meyer.
July 1998.
[PRIVATE] RFC 1918: Address Allocation for Private Internets. Y
Rekhter, B. Moskowitz, D. Karrenberg, G. J. de Groot, E. Lear.
February 1996.
[GHOST] Symantec.
http://service2.symantec.com/SUPPORT/ghost.nsf/docid/
1999033015222425
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[IMCAST] Phoenix Technologies.
http://www.storagesoft.com/products/imagecast
[ALTIRIS] Altiris
http://www.altiris.com/support/docs/altirisexpress/
axtechref41.pdf
[MSDP] Multicast Source Discovery Protocol. Bill Fenner and David
Meyer, Editors. Work in Progress. draft-ietf-msdp-spec-20.txt
[IANA] Internet Assigned Numbers Authority.
http://www.iana.org/assignments/multicast-addresses
12. Author's Address
Bill Nickless
Argonne National Laboratory
9700 South Cass Avenue #221 Phone: +1 630 252 7390
Argonne, IL 60439 Email: nickless@mcs.anl.gov
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