MAGMA WG B. Haberman
Internet-Draft JHU APL
Expires: March 2, 2005 J. Martin
Netzwert AG
September 2004
Multicast Router Discovery
draft-ietf-magma-mrdisc-03
Status of this Memo
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of section 3 of RFC 3667. By submitting this Internet-Draft, each
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RFC 3668.
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This Internet-Draft will expire on March 2, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
The concept of Internet Group Membership Protocol (IGMP) and
Multicast Listener Discovery (MLD) snooping requires the ability to
identify the location of multicast routers. Since snooping is not
standardized, there are many mechanisms in use to identify the
multicast routers. However, this can lead to interoperability issues
between multicast routers and snooping switches from different
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vendors.
This document introduces a general mechanism that allows for the
discovery of multicast routers. This new mechanism, Multicast Router
Discovery (MRD), introduces a standardized means of identifying
multicast routers without a dependency on particular multicast
routing protocols.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3. Multicast Router Advertisement . . . . . . . . . . . . . . . . 5
3.1 Advertisement Configuration Variables . . . . . . . . . . 5
3.1.1 MaxAdertisementInterval . . . . . . . . . . . . . . . 5
3.1.2 MinAdvertisementInterval . . . . . . . . . . . . . . . 5
3.1.3 MaxInitialAdvertisementInterval . . . . . . . . . . . 6
3.1.4 MaxInitialAdvertisements . . . . . . . . . . . . . . . 6
3.1.5 NeighborDeadInterval . . . . . . . . . . . . . . . . . 6
3.2 Advertisement Packet Format . . . . . . . . . . . . . . . 6
3.2.1 Type Field . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2 Advertisement Interval Field . . . . . . . . . . . . . 7
3.2.3 Checksum Field . . . . . . . . . . . . . . . . . . . . 7
3.2.4 Query Interval Field . . . . . . . . . . . . . . . . . 7
3.2.5 Robustness Variable Field . . . . . . . . . . . . . . 7
3.3 IP Header Fields . . . . . . . . . . . . . . . . . . . . . 7
3.3.1 Source Address . . . . . . . . . . . . . . . . . . . . 7
3.3.2 Destination Address . . . . . . . . . . . . . . . . . 7
3.3.3 Time-to-Live / Hop Limit . . . . . . . . . . . . . . . 8
3.3.4 IPv4 Protocol . . . . . . . . . . . . . . . . . . . . 8
3.4 Sending Multicast Router Advertisements . . . . . . . . . 8
3.5 Receiving Multicast Router Advertisements . . . . . . . . 8
4. Multicast Router Solicitation . . . . . . . . . . . . . . . . 9
4.1 Solicitation Packet Format . . . . . . . . . . . . . . . . 9
4.1.1 Type Field . . . . . . . . . . . . . . . . . . . . . . 9
4.1.2 Reserved Field . . . . . . . . . . . . . . . . . . . . 9
4.1.3 Checksum Field . . . . . . . . . . . . . . . . . . . . 10
4.2 IP Header Fields . . . . . . . . . . . . . . . . . . . . . 10
4.2.1 Source Address . . . . . . . . . . . . . . . . . . . . 10
4.2.2 Destination Address . . . . . . . . . . . . . . . . . 10
4.2.3 Time-to-Live / Hop Limit . . . . . . . . . . . . . . . 10
4.2.4 IPv4 Protocol . . . . . . . . . . . . . . . . . . . . 10
4.3 Sending Multicast Router Solicitations . . . . . . . . . . 10
4.4 Receiving Multicast Router Solicitations . . . . . . . . . 11
5. Multicast Router Termination . . . . . . . . . . . . . . . . . 11
5.1 Termination Packet Format . . . . . . . . . . . . . . . . 11
5.1.1 Type Field . . . . . . . . . . . . . . . . . . . . . . 11
5.1.2 Reserved Field . . . . . . . . . . . . . . . . . . . . 11
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5.1.3 Checksum Field . . . . . . . . . . . . . . . . . . . . 11
5.2 IP Header Fields . . . . . . . . . . . . . . . . . . . . . 12
5.2.1 Source Address . . . . . . . . . . . . . . . . . . . . 12
5.2.2 Destination Address . . . . . . . . . . . . . . . . . 12
5.2.3 Time-to-Live / Hop Limit . . . . . . . . . . . . . . . 12
5.2.4 IPv4 Protocol . . . . . . . . . . . . . . . . . . . . 12
5.3 Sending Multicast Router Terminations . . . . . . . . . . 12
5.4 Receiving Multicast Router Terminations . . . . . . . . . 12
6. Protocol Constants . . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1 Normative References . . . . . . . . . . . . . . . . . . . . 15
11.2 Informative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . 17
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1. Introduction
Multicast Router Discovery messages are useful for determining which
nodes attached to a switch have multicast routing enabled. This
capability is useful in a layer-2 bridging domain with snooping
switches. By utilizing MRD messages, layer-2 switches can determine
where to send multicast source data and group membership
messages[1][2]. Multicast source data and group membership Reports
must be received by all multicast routers on a segment. Using the
group membership protocol Query messages to discover multicast
routers is insufficient due to query suppression.
Although MRD messages could be sent as ICMP messages, the group
management protocols were chosen since this functionality is
multicast specific. The addition of this functionality to the group
membership protocol also allows operators to have congruency between
multicast router discovery problems and data forwarding issues.
The capitalized 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
[3].
2. Protocol Overview
Multicast Router Discovery consists of three messages for discovering
multicast routers. The Multicast Router Advertisement is sent by
routers to advertise that IP multicast forwarding is enabled.
Devices may send Multicast Router Solicitation messages in order to
solicit Advertisement messages from multicast routers. The Multicast
Router Termination messages are sent when a router stops IP multicast
routing functions on an interface.
Multicast routers send Advertisements periodically on all interfaces
on which multicast forwarding is enabled. Advertisement messages are
also sent in response to Solicitations. In addition to advertising
the location of multicast routers, Advertisements also convey useful
information concerning group management protocol variables. This
information can be used for consistency checking on the subnet.
A device sends Solicitation messages whenever it wishes to discover
multicast routers on a directly attached link.
A router sends Termination messages when it terminates multicast
routing functionality on an interface.
All MRD messages are sent with an IPv4 TTL or IPv6 Hop Limit of 1 and
contain the Router Alert Option[4][5]. All MRD messages SHOULD be
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rate-limited.
Advertisement and Termination messages are sent to the All-Snoopers
multicast address.
Solicitation messages are sent to the All-Routers multicast address.
Any data beyond the fixed message format MUST be ignored.
3. Multicast Router Advertisement
Multicast Router Advertisements are sent periodically on all router
interfaces on which multicast forwarding is enabled. They are also
sent in response to Multicast Router Solicitation messages.
Advertisements are sent
1. Upon the expiration of a periodic (modulo randomization) timer
2. As a part of a router's start up procedure
3. During the restart of a multicast forwarding interface
4. On receipt of a Solicitation message
All Advertisements are sent as IGMP (for IPv4) or MLD (for IPv6)
messages to the All-Snoopers multicast address. These messages
SHOULD be rate-limited.
3.1 Advertisement Configuration Variables
An MRD implementation MUST support the following variables being
configured by system management. Default values are specified to
make it unnecessary to configure any of these variables in many
cases.
3.1.1 MaxAdertisementInterval
This variable is the maximum time (in seconds) allowed between the
transmissions of Advertisements on an interface. This value MUST be
no less than 4 seconds and no greater than 180 seconds.
Default: 20 seconds
3.1.2 MinAdvertisementInterval
This is the minimum time (in seconds) allowed between the
transmissions of Advertisements on an interface. This value MUST be
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no less than 3 seconds and no greater than MaxAdvertisementInterval.
Default: 0.75 * MaxAdvertisementInterval
3.1.3 MaxInitialAdvertisementInterval
The first Advertisement transmitted on an interface is sent after
waiting a random interval (in seconds) less than this variable. This
prevents a flood of Advertisements when multiple routers start up at
the same time.
Default: 2 seconds
3.1.4 MaxInitialAdvertisements
This variable is the maximum number of Advertisements that will be
transmitted by the advertising interface when MRD starts up.
Default: 3
3.1.5 NeighborDeadInterval
The NeighborDeadInterval variable is the maximum time (in seconds)
allowed to elapse (after receipt of the last valid Advertisement)
before a neighboring router is declared unreachable. This variable
is maintained per neighbor. In order for all devices to have a
consistent state, it is necessary for the MaxAdvertisementInterval to
be configured consistently in all devices on the subnet.
Default: 3 * MaxAdvertisementInterval
3.2 Advertisement Packet Format
The Advertisement message has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Ad. Interval | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Query Interval | Robustness Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.1 Type Field
The Type field identifies the message as an Advertisement. It is set
to X1 (to be assigned by IANA) for IPv4 and X2 (to be assigned by
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IANA) for IPv6.
3.2.2 Advertisement Interval Field
This field specifies the periodic time interval at which
Advertisement messages are transmitted in units of seconds. This
value is set to the configured MaxAdvertisementInterval variable.
3.2.3 Checksum Field
The checksum field is set as follows:
1. For IPv4 it is the 16-bit one's complement of the one's
complement sum of the IGMP message, starting with the Type field.
For computing the checksum, the checksum field is set to 0.
2. For IPv6 it is ICMPv6 checksum as specified in [6].
3.2.4 Query Interval Field
The Query Interval field is set to the Query Interval value (in
seconds) in use by IGMP or MLD on the interface. If IGMP or MLD is
not enabled on the advertising interface, this field MUST be set to
0. Note that this is the Querier's Query Interval (QQI), not the
Querier's Query Interval Code (QQIC) as specified in the IGMP/MLD
specifications.
3.2.5 Robustness Variable Field
This field is set to the Robustness Variable in use by IGMPv2[2],
IGMPv3[7], or MLD[8][9] on the advertising interface. If IGMPv1 is
in use or no group management protocol is enabled on the interface,
this field MUST be set to 0.
3.3 IP Header Fields
3.3.1 Source Address
The IP source address is set to an IP address configured on the
advertising interface. For IPv6, a link-local address MUST be used.
3.3.2 Destination Address
The IP destination address is set to the All-Snoopers multicast
address.
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3.3.3 Time-to-Live / Hop Limit
The IPv4 TTL and IPv6 Hop Limit are set to 1.
3.3.4 IPv4 Protocol
The IPv4 Protocol field is set to IGMP (2).
3.4 Sending Multicast Router Advertisements
Advertisement messages are sent when the following events occur:
1. The expiration of the periodic advertisement interval timer.
Note that it this timer is not strictly periodic since it is a
random number between MaxAdvertisementInterval and
MinAdvertisementInterval.
2. After a random delay less than MaxInitialAdvertisementInterval
when an interface is first enabled, is (re-)initialized, or MRD
is enabled. A router may send up to a maximum of
MaxInitialAdvertisements Advertisements, waiting for a random
delay less than MaxInitialAdvertisementInterval between each
successive message. Multiple Advertisements are sent for
robustness in the face of packet loss on the network.
This is to prevent an implosion of Advertisements. An example of
this occurring would be when many routers are powered on at the same
time. When a Solicitation is received, an Advertisement is sent in
response with a random delay less than MAX_RESPONSE_DELAY. If a
Solicitation is received while an Advertisement is pending, that
Solicitation MUST be ignored.
Changes in the Query Interval or Robustness Variable MUST NOT trigger
a new advertisement, however the new values MUST be used all future
Advertisement messages.
When an Advertisement is sent, the periodic advertisement interval
timer MUST be reset.
3.5 Receiving Multicast Router Advertisements
Upon receiving an Advertisement message, devices validate the message
with the following criteria:
1. The checksum is correct
2. The IP destination address is equal to the All-Snoopers multicast
address
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3. For IPv6, the IP source address is a link-local address
An Advertisement not meeting the validity requirements MUST be
silently discarded and may be logged in a rate-limited manner.
If an Advertisement is not received for a particular neighbor within
a NeighborDeadInterval time interval, then the neighbor is considered
unreachable.
4. Multicast Router Solicitation
Multicast Router Solicitation messages are used to solicit
Advertisements from multicast routers on a segment. These messages
are used when a device wishes to discover multicast routers. Upon
receiving a solicitation on an interface with IP multicast forwarding
and MRD enabled, a router will respond with an Advertisement.
Solicitations may be sent when:
1. An interface is (re-)initialized
2. MRD is enabled
Solicitations are sent to the All-Routers multicast address and
SHOULD be rate-limited.
4.1 Solicitation Packet Format
The Solicitation message has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1.1 Type Field
The Type field identifies the message as a Solicitation. It is set
to Y1 (to be assigned by IANA) for IPv4 and Y2 (to be assigned by
IANA) for IPv6.
4.1.2 Reserved Field
The Reserved field is set to 0 on transmission and ignored on
reception.
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4.1.3 Checksum Field
The checksum field is set as follows:
o For IPv4 it is the 16-bit one's complement of the one's complement
sum of the IGMP message, starting with the Type field. For
computing the checksum, the checksum field is set to 0.
o For IPv6 it is ICMPv6 checksum as specified in [6].
4.2 IP Header Fields
4.2.1 Source Address
The IP source address is set to an IP address configured on the
soliciting interface. For IPv6, a link-local address MUST be used.
4.2.2 Destination Address
The IP destination address is set to the All-Routers multicast
address.
4.2.3 Time-to-Live / Hop Limit
The IPv4 TTL and IPv6 Hop Limit are set to 1.
4.2.4 IPv4 Protocol
The IPv4 Protocol field is set to IGMP (2).
4.3 Sending Multicast Router Solicitations
Solicitation messages are sent when the following events occur:
o After waiting for a random delay less than MAX_SOLICITATION_DELAY
when an interface first becomes operational, is (re-)initialized,
or MRD is enabled. A device may send up to a maximum of
MAX_SOLICITATIONS, waiting for a random delay less than
MAX_SOLICITATION_DELAY between each solicitation.
o Optionally, for an implementation specific event.
Solicitations MUST be rate-limited; the implementation MUST send no
more than MAX_SOLICITATIONS in MAX_SOLICITATION_DELAY seconds.
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4.4 Receiving Multicast Router Solicitations
A Solicitation message MUST be validated before a response is sent.
A router MUST verify that:
o The checksum is correct
o The IP destination address is the All-Routers multicast address
o For IPv6, the IP source address MUST be a link-local address
Solicitations not meeting the validity requirements SHOULD be
silently discarded and may be logged in a rate-limited manner.
5. Multicast Router Termination
The Multicast Router Termination message is used to expedite the
notification of a change in the status of a router's multicast
forwarding functions. Multicast routers send Terminations when
multicast forwarding is disabled on the advertising interface.
5.1 Termination Packet Format
The Termination message has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.1 Type Field
The Type field identifies the message as a Termination. It is set to
Z1 (to be assigned by IANA) for IPv4 and Z2 (to be assigned by IANA)
for IPv6.
5.1.2 Reserved Field
The Reserved field is set to 0 on transmission and ignored on
reception.
5.1.3 Checksum Field
The checksum field is set as follows:
o For IPv4 it is the 16-bit one's complement of the one's complement
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sum of the IGMP message, starting with the Type field. For
computing the checksum, the checksum field is set to 0.
o For IPv6 it is ICMPv6 checksum as specified in [6].
5.2 IP Header Fields
5.2.1 Source Address
The IP source address is set to an IP address configured on the
advertising interface. For IPv6, a link-local address MUST be used.
5.2.2 Destination Address
The IP destination address is set to the All-Snoopers multicast
address.
5.2.3 Time-to-Live / Hop Limit
The IPv4 TTL and IPv6 Hop Limit are set to 1.
5.2.4 IPv4 Protocol
The IPv4 Protocol field is set to IGMP (2).
5.3 Sending Multicast Router Terminations
Termination messages are sent by multicast routers when:
o Multicast forwarding is disabled on an interface
o An interface is administratively disabled
o The router is gracefully shutdown
o MRD is disabled
The sending of Termination messages SHOULD be rate-limited.
5.4 Receiving Multicast Router Terminations
Upon receiving a Termination message, devices validate the message.
The validation criteria is:
o Checksum MUST be correct
o IP destination address MUST equal the All-Snoopers multicast
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address
o For IPv6, the IP source address MUST be a link-local address
Termination messages not meeting the validity requirements MUST be
silently discarded and may be logged in a rate-limited manner.
If the message passes these validation steps, a Solicitation is sent.
If an Advertisement is not received within NeighborDeadInterval, the
sending router is removed from the list of active multicast routers.
6. Protocol Constants
The following list identifies constants used in the MRD protocol.
These constants are used in the calculation of parameters.
o MAX_RESPONSE_DELAY 2 seconds
o MAX_SOLICITATION_DELAY 1 second
o MAX_SOLICITATIONS 3 transmissions
7. Security Considerations
Rogue nodes may attempt to attack a network running MRD by sending
spoofed Advertisement, Solicitation, or Termination messages. Each
type of spoofed message can be dealt with using existing technology.
A rogue node may attempt to interrupt multicast service by sending
spoofed Termination messages. As described in Section 5.4, all
Termination messages are validated by sending a Solicitation message.
By sending a Solicitation, the node will force the transmission of an
Advertisement by an active router.
Spoofed Solicitation messages do not cause any operational harm.
They may be used as a flooding mechanism to attack a multicast
router. This attack can be mitigated through the rate-limiting
recommendation for all MRD messages.
The Multicast Router Advertisement message may allow rogue machines
to masquerade as multicast routers. This could allow those machines
to eavesdrop on multicast data transmissions. Additionally, it could
constitute a denial of service attack to other hosts in the same
snooping domain or sharing the same device port in the presence of
high rate multicast flows.
The technology available in SEND[10] can be utilized to address
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spoofed Advertisement messages in IPv6 networks. IPv6 Multicast
routers in an MRD-enabled network can use SEND-based link-local
addresses as the IPv6 source address for MRD messages. When a switch
receives an initial Advertisement, it can use the information in the
SEND-based address to challenge the router to authenticate itself.
It should be noted that this approach only applies to IPv6 networks.
Another solution which supports both IPv4 and IPv6 is to use IPSec in
Authentication Header mode[11] to protect against attacks by ensuring
that messages came from a system with the proper key. When using
IPSEC, the messages sent to the All-Snoopers address should be
authenticated using AH. For keying, a symmetric signature algorithm
with a single key for routers sending Advertisements. This allows
validation that the MRD message was sent by a system with the key.
It should be noted that this does not prevent a system with the key
from forging a message and it requires the disabling of IPSec's
Replay Protection.
8. IANA Considerations
This document introduces three new IGMP messages. Each of these
messages requires a new IGMP Type value. This document requests IANA
to assign three new IGMP Type values to the Multicast Router
Discovery Protocol:
+-----------+---------------+--------------------------------+
| IGMP Type | Section | Message Name |
+-----------+---------------+--------------------------------+
| X1 | Section 3.2.1 | Multicast Router Advertisement |
| Y1 | Section 4.1.1 | Multicast Router Solicitation |
| Z1 | Section 5.1.1 | Multicast Router Termination |
+-----------+---------------+--------------------------------+
This document also introduces three new MLD messages. Each of these
messages requires a new ICMPv6 Type value. This document requests
IANA to assign three new ICMPv6 Type values from the Informational
range:
+-------------+---------------+--------------------------------+
| ICMPv6 Type | Section | Message Name |
+-------------+---------------+--------------------------------+
| X2 | Section 3.2.1 | Multicast Router Advertisement |
| Y2 | Section 4.1.1 | Multicast Router Solicitation |
| Z2 | Section 5.1.1 | Multicast Router Termination |
+-------------+---------------+--------------------------------+
This document also requires the assignment of an All-Snoopers
multicast address for IPv4. This multicast address should be in the
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224.0.0/24 range since it is used for link-local, control messages.
A corresponding IPv6 multicast address is also requested. Following
the guidelines in [12], the IPv6 multicast address should be
link-local in scope and have a group-ID value equal to the low order
8 bits of the requested IPv4 multicast address.
9. Authors
Brad Cain and Shantam Biswis are the authors of the original
Multicast Router Discovery proposal.
10. Acknowledgements
ICMP Router Discovery [13] was used as a general model for Multicast
Router Discovery.
Morten Christensen, Pekka Savola, Hugh Holbrook, and Isidor Kouvelas
provided helpful feedback on various versions of this document.
11. References
11.1 Normative References
[1] Deering, S., "Host extensions for IP multicasting", STD 5, RFC
1112, August 1989.
[2] Fenner, W., "Internet Group Management Protocol, Version 2",
RFC 2236, November 1997.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Katz, D., "IP Router Alert Option", RFC 2113, February 1997.
[5] Partridge, C. and A. Jackson, "IPv6 Router Alert Option", RFC
2711, October 1999.
[6] Conta, A. and S. Deering, "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC 2463, December 1998.
[7] Cain, B., Deering, S., Kouvelas, I., Fenner, B. and A.
Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, October 2002.
[8] Deering, S., Fenner, W. and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999.
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[9] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004.
[10] Arkko, J., Kempf, J., Sommerfeld, B., Zill, B. and P. Nikander,
"SEcure Neighbor Discovery (SEND)", draft-ietf-send-ndopt-06
(work in progress), July 2004.
[11] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402,
November 1998.
[12] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Addresses", RFC 3307, August 2002.
11.2 Informative References
[13] Deering, S., "ICMP Router Discovery Messages", RFC 1256,
September 1991.
[14] Bradner, S., "Intellectual Property Rights in IETF Technology",
BCP 79, RFC 3668, February 2004.
[15] Daigle, L. and Internet Architecture Board, "IETF ISOC Board of
Trustee Appointment Procedures", BCP 77, RFC 3677, December
2003.
Authors' Addresses
Brian Haberman
Johns Hopkins University Applied Physics Lab
11100 Johns Hopkins Road
Laurel, MD 20723-6099
US
Phone: +1 443 778 1319
EMail: brian@innovationslab.net
Jim Martin
Netzwert AG
An den Treptowers 1
D-12435 Berlin
Germany
Phone: +49.30/5 900 800-180
EMail: jim@netzwert.ag
Haberman & Martin Expires March 2, 2005 [Page 16]
Internet-Draft Multicast Router Discovery September 2004
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