Internet DRAFT - draft-chenwm-magma-igmp-router-info
draft-chenwm-magma-igmp-router-info
Network Working Group Chen Wumao
Internet-Draft Huawei
July 30, 2005
Expires: January 30, 2006
Extend IGMPv3 To Support Router Annoucing Information For Host
<draft-chenwm-magma-igmp-router-info-00.txt>
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
IGMP is used by IPv4 system to report their multicast group
memberships to multicast routers.
This document adds support for router annoucing information, that
is, the ability for a multicast router to annouce information about a
group to host. For example, some hosts may send reports to join a
group that do not exist, so the router would send some message to
inform the hosts.
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1. Requirements notation
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 [RFC2119].
2. Introduction
The IGMP protocol (IGMPv1, IGMPv2, IGMPv3) is used by IPv4 hosts to
report their IP multicast group memberships to its neighboring
multicast routers. It specifies how an IPv4 host could join or leave
multicast groups, and how an Multicast router use IGMP to learn which
groups have members on each of its attached physical or logical
networks.
It is possible that an multicast router can not forward some groups
to some of its attached networks. The reasons may be various. For
example, the group is not exist, or the attached network does not
have the right to access the group, or the bandwidth needed for the
group is too high for the attached network to support. In these
scenarios, the multicast router had better sends some messages to
inform the reasons.
This document specifies a new IGMP message that allows multicast
routers annoucing information to hosts.
3. Meassage Formats
The IGMP protocol (IGMPv1, IGMPv2, IGMPv3) has specified 5 types of
IGMP messages, as following:
Type Number (hex) Message Name
----------------- ------------
0x11 Membership Query
0x12 Version 1 Membership Report
0x16 Version 2 Membership Report
0x22 Version 3 Membership Report
0x17 Version 2 Leave Group
This document discribes a new type of message:
YY Group Information
(to be assigned by IANA)
Similar to Membership Query Message, Group Informations are sent by
multicast router, and have two sub-types:
- General Information, used to annouce informations about the
router to its attached network. Such informations are needed
to learn by any member of any group.
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- Group-Specific Information, used to annouce informations
about a specific group to an attached network. Such
informations are needed to learn by any member of the group.
These two messages are differentiated by the Group Address, as
described in section 3.3 . In this document Group Information
messages are referred to simply as "Information".
Informations have 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 = YY | Resv | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Notes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.1. Resv (Reserved)
The Resv field is set to zero on transmission, and ignored on
reception.
3.2. Checksum
The Checksum field is the 16-bit one's complement of the one's
complement sum of the whole IGMP message (the entire IP payload). For
computing the checksum, the Checksum field is set to zero. When
receiving packets, the checksum MUST be verified before processing a
packet. [RFC-1071]
3.3. Group Address
The Group Address field is set to all zero when sending a General
Information, and set to the IP multicast address being informing when
sending a Group-Specific Information.
3.4. Length
The Length field is the length of the Notes field, measured in
octets. It MUST NOT be set to zero on transmission. Length with zero
value indicates that the message MUST be silently discarded on
reception.
3.5. Notes
The Notes field is used to pass information, and text based.
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3.6. Destination IP Addresses
General Informations are sent with an IP destination address of
224.0.0.1, the all-systems multicast address. Group-Specific
Informations are sent with an IP destination address equal to the
multicast address of interest.
4. Requirement for Multicast Routers
Only the Querier need to send Informations, the other multicast
routers SHOULD keep silent. Routers SHOULD NOT forward Informations.
5. Security Considerations
Information message will not change the status of Querier, so a
forged Information will not creat any security concerns to multicast
routers.
A forged Informatin message sent to a group may pass some fake
information to the hosts which are members of the group. This cause
no protocol problems.
6. IANA Considerations
This document introduces a new IGMP messages, this message requires a
new IGMP Type value. This document requests IANA to assign a new
IGMP Type values to IGMP Protocol:
+-----------+-----------------+--------------------------------+
| IGMP Type | Section | Message Name |
+-----------+-----------------+--------------------------------+
| YY | Section 3 | Group Information Message |
+-----------+-----------------+--------------------------------+
7. References
[RFC-1112] Deering, S., "Host Extensions for IP Multicasting", STD
5, RFC 1112, August 1989.
[RFC-2113] Katz, D., "IP Router Alert Option," RFC 2113, February,
1997.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-2236] Fenner, W., "Internet Group Management Protocol, Version
2", RFC 2236, November 1997.
[RFC-3376] Cain, B., Deering, S., Fenner, B., Kouvelas, I., and
Thyagarajan, A., "Internet Group Management Protocol,
Version 3," RFC3376, October 2002
Chen Wumao Expires January 30,2006 [Page 4]
INTERNET-DRAFT Extend IGMPv3 For Router Annoucing July 2005
Author's Address
Chen Wumao
Huawei Industrial Base
Bantian Longgang
Shenzhen 518129 P.R.C
EMail: Chenwm@huawei.com
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