wdiff draft-ietf-mboned-lightweight-igmpv3-mldv2-00.txt draft-ietf-mboned-lightweight-igmpv3-mldv2-01.txt

MBONED Working Group H. Liu
Internet-Draft W. Cao
Expires: June, December 31, 2007 Huawei Technologies Co., Ltd.
H. Asaeda
Keio University
December 19, 2006
June 29, 2007

Lightweight IGMPv3 and MLDv2 Protocols
<draft-ietf-mboned-lightweight-igmpv3-mldv2-00.txt>
draft-ietf-mboned-lightweight-igmpv3-mldv2-01

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Abstract

This document describes lightweight IGMPv3 and MLDv2 protocols (LW-
IGMPv3 and LW-MLDv2), which simplify the standard (full) versions of
IGMPv3 and MLDv2. The interoperability with the full versions and
the previous versions of IGMP and MLD is also taken into account.

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
[KEYWORDS]. [1].

Table of Contents

1. Introduction ................................................... 2 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Simplification Method Overview ................................. 4 . . . . . . . . . . . . . . . . 6
2.1. Behavior of Group Members ................................. 4 . . . . . . . . . . . . . . . . 6
2.2. Behavior of Multicast Routers ............................. 4 . . . . . . . . . . . . . . 6
3. LW-IGMPv3 Protocol for Group Members ........................... 5 . . . . . . . . . . . . . 8
3.1. Action on Change of Interface State ....................... 5 . . . . . . . . . . . 8
3.2. Action on Reception of a Query ............................ 6 . . . . . . . . . . . . . . 9
3.3. Applicable Group Record Types ............................. 7 . . . . . . . . . . . . . . 10
4. LW-IGMPv3 Protocol for Multicast Routers ....................... 8 . . . . . . . . . . . 12
4.1. Group Timers and Source Timers in the Lightweight
Version ................................ 8 . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Source-Specific Forwarding Rules .......................... 9 . . . . . . . . . . . . . 13
4.3. Reception of Current-State Records ....................... 10 . . . . . . . . . . . . 13
4.4. Reception of Source-List-Change and Filter-Mode-Change
Records ............................... 11 . . . . . . . . . . . . . . . . . . . . . . . . . 14
5. Interoperability .............................................. 12 . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. Interoperation with the Full Version of IGMPv3 ........... 12 . . . . . . 16
5.2. Interoperation with IGMPv1/IGMPv2 ........................ 13 . . . . . . . . . . . . 16
5.2.1. Behavior of Group Members ........................... 13 . . . . . . . . . . . . . . 16
5.2.2. Behavior of Multicast Routers ....................... 13 . . . . . . . . . . . . 17
6. Implementation Considerations ................................. 13 . . . . . . . . . . . . . . . . 18
6.1. Implementation of Source-Specific Multicast .............. 14 . . . . . . . 18
6.2. Implementation of Multicast Source Filter (MSF) APIs ..... 14 . . . 18
7. Security Considerations ....................................... 14 . . . . . . . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References .......................................... 14
9. . . . . . . . . . . . . . . . . . . . 20
8.2. Informative References ........................................ 15 . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property Statement .................................. 16
Disclaimer of Validity ........................................... 16 and Copyright Statement .............................................. 16
Acknowledgment ................................................... 16 Statements . . . . . . . . . . 22

1. Introduction

IGMP version 3 [IGMPv3] [2] and MLD version 2 [MLDv2] [3] implement source filtering capability
capabilities that is are not suported by their earlier versions versions, IGMPv1
[4], IGMPv2 [IGMPv2] [5] and MLDv1 [MLDv1]. [6]. An IGMPv3 or MLDv2 capable host can
tell its upstream router which group it would like to join to its upstream router
with by
specifying which sources it does or does not intend to receive
multicast traffic from. IGMPv3 and MLDv2 add the capability for a
multicast router to also learn which sources are of interest to
neighboring systems, for packets sent to any particular multicast
address.

The INCLUDE and EXCLUDE filter-modes are defined for the host and router parts of the
protocols respectively introduced to support the
source filtering function. If a receiver host wants to receive from specific
sources, it sends an IGMPv3 or MLDv2 report with filter-mode set to
INCLUDE. If the host does not want to receive from some sources, it
sends the a report with filter-mode set to EXCLUDE. A source list for
the given sources shall be included in the report message.

INCLUDE and EXCLUDE filter modes are also defined in a multicast
router to process the IGMPv3 or MLDv2 reports. When a multicast
router receives the report messages from its downstream hosts, it
forwards the corresponding multicast traffic by managing requested
group and source addresses. Group timer timers and source timer timers are used
to maintain the forwarding state of desired group and source. A multicast
router decides its filter-mode, type, and value of the timers groups and
forwarding methods according to the specific rules when sources under
certain filter modes. When a group report message arrives or the a certain timer expires. The
expires, a multicast router then has to
switch its filter-mode under certain conditions. may update the desired or undesired
source lists, reset related timer values, change filter mode, or
trigger group queries. With all of the above factors correlating
with each other, the determination rule becomes rules become relatively complex complex,
as the interface states could be frequently changed.

The multicast filter-mode improves the expressing ability of the multicast receiver.
receiver to express its desires. It is useful to support Source-Specific Source-
Specific Multicast (SSM) [SSM] [7] by specifying interesting source
addresses with INCLUDE mode. However, practical applications do not
use EXCLUDE mode to block sources so very often, because a user or
application usually wants to specify desired source addresses, not
undesired source
addresses to not receive from them. addresses. Even if a user wants to explicitly
refuse traffic from some sources in a group, when other users in the
same shared network have an interest in these sources, the
corresponding multicast traffic is forwarded to the network after
all. network.

This document aims to propose the proposes simplified versions of IGMPv3 and MLDv2, being named
Lightweight IGMPv3 and Lightweight MLDv2 (or LW-IGMPv3 and LW-
MLDv2), LW-MLDv2),
in which EXCLUDE filter-mode that supports to exclude data
come from specified sources is eliminated. Not only are LW-IGMPv3
and LW-MLDv2 are compatible with the standard IGMPv3 and MLDv2, but also
the protocol operations made by data receiver hosts and routers or
switches (performing IGMPv3/MLDv2 snooping) are simplified in the
lightweight protocol protocol, and complicated operations are hence
effectively reduced. Since LW-IGMPv3 and LW-MLDv2 are fully
compatible with the full version of these protocols (i.e. (i.e., the
standard IGMPv3 and MLDv2), hosts or routers that have implemented
the full version do not need to implement or modify anything to
cooperate with LW-IGMPv3/LW-MLDv2 hosts or routers.

2. Simplification Method Overview

The principle is to simplify the host and router parts as much as
possible to improve efficiency, while guaranteeing the interoperability
with the full versions, and introducing no side effects on the
applications.

For convenience, this document mainly discusses IGMPv3 IGMPv3, since MLDv2
inherits the same source filtering mechanism, but this document
additionally shows MLDv2's unique specifications when needed.

2.1. Behavior of Group Members

In the LW-IGMPv3, the same service interface model as that of IGMPv3 is
inherited:

IPMulticastListen ( socket, interface, multicast-address,
filter-mode, source-list )

In the lightweight protocol, EXCLUDE mode on the host part is
preserved only for EXCLUDE (*,G) join, which denotes a non-source-
specific group report (as known as (*,G) join) and is equivalent to
the group membership join triggered by IGMPv2/IGMPv1/MLDv1. The
detailed host operation of LW-IGMPv3/LW-MLDv2 is described in section
3.
Section 4.

2.2. Behavior of Multicast Routers

According to [IGMPv3], router

Router filter-mode is defined to optimize the state description of a group.
group [2]. As a rule, once a member report is in EXCLUDE mode, the
router filter-mode for the group will be set to EXCLUDE. When all
systems cease sending EXCLUDE mode reports, the filter-mode for that
group may transit back to INCLUDE mode. Group timer is used to
identify such transition.

In LW-IGMPv3, member reports carry mainly the hosts primarily send INCLUDE mode
information with requests. The only one
exception for EXCLUDE (*,G), is EXLUDE (*,G) join, which means
including all sources and can also be interpreted by the
router as INCLUDE mode. a request to include all sources. Without the more general
form of EXCLUDE mode report information, requests, it is unnecessary for the router to
maintain the EXCLUDE filter-mode, and the state model for multicast
router can be simplified as:

(multicast address, group timer, (source records))

Here a group timer is kept to represent (*,G) group join. Its basic
behavior is: when a router receives a (*,G) group join, it will set
its group timer, timer and keep the source list for sources specified in the source-specific group
will be kept. As
source records. When the group timer expires, the router may change
to the reception for the listed sources. The definition of the
source record is the same as that of full version.

The elimination of the filter-mode will greatly simplify the router
behavior, e.g. the action on reception of reports and the setting of
the timers. The detailed operation of router operation is described
in section Section 4.

3. LW-IGMPv3 Protocol for Group Members

LW-IGMPv3 uses two sets of messages, i.e., Query and Report messages,
being the same as the full version protocols. Although most of these
message types and corresponding group records are inherited from the
full version protocols, an operation that triggers EXCLUDE (S,G) join
is omitted and the corresponding record types of the Report are
modified on the lightweight protocols.

There are three Group Record Types defined in the full IGMPv3:
Current-State Record noted by MODE_IS_INCLUDE (referred to as IS_IN)
or MODE_IS_EXCLUDE (IS_EX), Filter-Mode-Change Record noted by
CHANGE_TO_INCLUDE_MODE (TO_IN) or CHANGE_TO_EXCLUDE_MODE (TO_EX), and
Source-List-Change Record noted by ALLOW_NEW_SOURCES (ALLOW) or
BLOCK_OLD_SOURCES (BLOCK).

3.1. Action on Change of Interface State

When the state of an interface state of a group member host is changed, a State-
Change
State-Change Report for that interface is immediately transmitted
from that interface. The type and contents of the Group Record(s) in
that Report are determined by comparing the filter mode and source
list for the affected multicast address before and after the change.
While the requirements are the same as the full version for the
computation, in the lightweight version host, the interface state
change rules are simplified due to the reduction of message types.
The contents of the new transmitted report are calculated as follows
(Group Record Types are described in section Section 3.3):

Old State New State State-Change Record Sent
----------- ----------- ------------------------

INCLUDE (A) INCLUDE (B) ALLOW(B-A), BLOCK(A-B)

INCLUDE (A) EXCLUDE () IS_EX() TO_EX()

INCLUDE () EXCLUDE () IS_EX() TO_EX()

EXCLUDE () INCLUDE (B) TO_IN(B)

To cover the possibility of the State-Change Report being missed by
one or more multicast routers, it is retransmitted [Robustness
Variable]-1 more times, at intervals chosen at random from the range
(0, [Unsolicited Report Interval]). (These values are defined in
[IGMPv3, MLDv2].)
[2][3].)

In the full version of IGMPv3, as was done with the first report, the
interface state for the affected group before and after the latest
change is compared, and the report records expressing the difference
are built and merged with the contents of the pending report, to
create the new State-Change report. However, it is optional that a
LW-IGMPv3 host merges with the contents of for the pending report. LW-IGMPv3 host,
this merge operation is optional. If the LW-IGMPv3 host does not
merge with the contents of the pending report, it transmits each
report sequentially. Doing so can greatly simplified the operation
for scheduling the reports.

3.2. Action on Reception of a Query

When a lightweight version host receives a Query, it does not respond
immediately. Instead, it delays its response by a random amount of
time, bounded by the Max Resp Time value derived from the Max Resp
Code in the received Query message [IGMPv3, MLDv2]. [2][3]. The system may receive a
variety of Queries on different interfaces and of different kinds
(e.g., General Queries, Group-Specific Queries, and Group-and-
Source-Specific Group-and-Source-
Specific Queries), each of which may require its own delayed
response.

Before scheduling a response to a Query, the system must first
consider previously scheduled pending responses and in many cases
schedule a combined response. Therefore, the lightweight version
host must be able to maintain the following state:

o A timer per interface for scheduling responses to General Queries.

o A per-group and interface timer for scheduling responses to Group-
Specific and Group-and-Source-Specific Queries.

o A per-group and interface list of sources to be reported in the
response to a Group-and-Source-Specific Query.

LW-IGMPv3 inherits most of the rules that are used to determine if a
Report needs to be scheduled from the full version. The different
point difference
is regarding the simplification of EXCLUDE filter-mode and the type
of Report to schedule as detailed in section Section 3.3.

While it is optional that a LW-IGMPv3 host merges with the contents
of the pending report for unsolicited report (i.e. (i.e., State-Change
report) as mentioned in the previous section, if the received Query
is a Group-and-Source-Specific Query and there is a pending response
for this group with a non-empty source-list, then the group source
list is augmented to contain the list of sources in the new Query and
a single response is scheduled using the group timer as with the full
version host. The new response is then scheduled to be sent at the
earliest
earlier of the remaining time for the pending report and the selected
delay.

3.3. Applicable Group Record Types

Among Group Record Types defined in the full IGMPv3, several record
types are not used in LW-IGMPv3 as some of the processes related to
the filter mode change to the EXCLUDE mode are eliminated and some of
the report messages are converged with a record having null source
address list. All of the record types of report messages used by the
full and lightweight version protocols are shown as follows:

IGMPv3 LW-IGMPv3 Comments
-------- --------- -------------------------------------

IS_EX() IS_EX() TO_EX() Query response for (*,G) join

IS_EX(x) N/A Query response for EXCLUDE (x,G) join

IS_IN(x) ALLOW(x) Query response for INCLUDE (x,G) join

ALLOW(x) ALLOW(x) INCLUDE (x,G) join

BLOCK(x) BLOCK(x) INCLUDE (x,G) leave

TO_IN(x) TO_IN(x) Change to INCLUDE (x,G) join

TO_IN() TO_IN() (*,G) leave

TO_EX(x) N/A Change to EXCLUDE (x,G) join

TO_EX() IS_EX() TO_EX() (*,G) join

where "x" represents a non-null source address list and "()"
represents null source address list. For instance, IS_EX() means a
report whose record type is IS_EX with null source address list.
"N/A" represents not applicable (or no use) because the corresponding
operation should not occur in the lightweight version protocols.

LW-IGMPv3 does not use EXCLUDE filter-mode with a non-null source
address list. And a A multicast router creates the same state when it
receives a report message containing either of IS_EX IS_EX() or TO_EX TO_EX() record
types. Therefore, LW-IGMPv3 integrates the TO_EX IS_EX() operation to with
the
IS_EX TO_EX() operation.

When a LW-IGMPv3 host needs to make a query response for the state of
INCLUDE (x,G) join, the host it makes the a response whose message type is
expressed with ALLOW(x), instead of using the IS_IN record type, for type.
Because the router's processing of the two messages are is completely the
same, the IS_IN(x) type is eliminated for simplification.

A LW-IGMPv3 host does not use EXCLUDE mode, while TO_IN record is
used with the following situation: the host firstly first launches an application
(AP1) that requests INCLUDE (x,G) join, and it sends ALLOW(x). Then the
host launches another application (AP2) that joins (*,G), and it
sends IS_EX(). TO_EX(). In this condition, when AP2 terminates but AP1 keeps
working on the lightweight version host, the host sends a report with
TO_IN(x) record type for [Robustness Variable] times.

4. LW-IGMPv3 Protocol for Multicast Routers

The major difference between the full and lightweight version
protocol
protocols on the router part is that filter-mode is discarded for the lightweight version, as section 2.2 mentioned. Then the IGMP state
maintained by the router for each attached network can be simplified
as:

(multicast address, group timer, (source records))

where the source record includes pairs of source address and its
corresponding source timer. In this model, the version
filter-mode is
omitted discarded and the meaning function of the group timer is redefined to implement
simplified processing.
redefined. The states maintained by the lightweight router are
reduced and the protocol operation is greatly simplified.

4.1. Group Timers and Source Timers in the Lightweight Version

The

A source timer is kept for each source record and it is updated when
the source is present in a received report. It indicates the
validity of the sources and needs to be referred when the router
takes its forwarding decision.

The group timer being used in the full version of IGMPv3 as a
mechanism for
transitioning the router's filter-mode from EXCLUDE to INCLUDE, is
now redefined for the identification of to identify the non-source-
specific non-source-specific receiving states, i.e., (*,G)join. states
maintaining for (*,G) join. Once a group record of IS_EX() is
received, the group timer is used to represent this (*,G) group join.
The expiration of the group timer indicates that there are no
listeners on the attached network for this (*,G) group. Then
if at this moment If there are
unexpired sources (whose source timers are greater than zero), the
router will change to receiving traffic for those sources. The role
of the group timer can be summarized as follows:

Group Timer Value Actions/Comments
------------------ --------------------------------------

G_Timer > 0 All members in this group.

G_Timer == 0 No more listeners to this (*,G) group.
If all source timers have expired then
delete group record. If there are
still source record timers running,
use those source records with running
timers as the source record state.

The operation related to the group and source timers has some
difference compared with the full IGMPv3. In the full version, if a
source timer expires under the EXCLUDE router filter-mode, its
corresponding source record is not deleted until the group timer
expires. They are kept
expires for indicating undesired sources. In the lightweight
version, since there is no need to keep such records for blocking
specific sources, if a source timer expires, its source record should
be deleted immediately, not waiting for the time-out of the group
timer.

4.2. Source-Specific Forwarding Rules

A full version multicast router needs to consult IGMPv3 state
information when it makes decisions on forwarding a datagram from a
source or its upstream router to its attached network. In the full IGMPv3, network, based on the
router filter-mode and source timer are taken as the necessary judging conditions. timer. In LW-
IGMPv3, LW-IGMPv3, because of the
absence of the router filter-mode, the group timer and source timer
could be used for such decisions. The forwarding suggestion made by
LW-IGMPv3 to the routing protocols can
be is summarized as follows:

Group Timer Source Timer Action
------------ ------------------ -----------------------

G_Timer == 0 S_TIMER > 0 Suggest to forward forwarding
traffic from source

G_Timer == 0 S_TIMER == 0 Suggest to stop stopping
forwarding traffic from
source and remove
source record. If there
are no more source
records for the group,
delete group record

G_Timer == 0 No Source Elements Suggest not to forward
traffic from the source

G_Timer > 0 S_TIMER >= 0 Suggest to forward forwarding
traffic from source

G_Timer > 0 No Source Elements Suggest to forward forwarding
traffic from source

4.3. Reception of Current-State Records

When receiving Current-State Records, the LW-IGMPv3 router resets its
group or source timers and updates its source list within the group.
For source-specific group reception state (G_Timer==0), (when G_Timer==0), the
source list includes contains sources to whose traffic will be forwarded by the
router, while in non-
source-specific non-source-specific group reception (G_Timer>0) (when
G_Timer>0), the source list remembers the valid sources to be forwarded receive
traffic from after toggling to source-specific reception state.

The following table describes

Although the action taken by Lightweight host only sends a multicast router
after receiving Current-State Records. The notations have subset of the same
meaning as message of
that in of the full IGMPv3.

Old New
Source version, the LW-router should be able to process as
much messages as possible to be compatible with the full version
host. The following table describes the action taken by a multicast
router after receiving Current-State Records. The notations have the
same meaning as that in the full IGMPv3 protocol.

Old New
Source Source
Group Timer List Report Rec'd List Actions
------------ ------ ------------ ------ -----------

G_Timer == 0 A IS_IN(B) A+B (B)=GMI

G_Timer == 0 A IS_EX() A G_Timer=GMI

G_Timer > 0 A IS_IN(B) A+B (B)=GMI

G_Timer > 0 A IS_EX() A G_Timer=GMI

And the

The above table could be further simplified for the processes that
are completely same for the two values of the G_Timer:

Old New
Source Source
List Report Rec'd List Actions
------ ------------ ------ -----------

A IS_IN(B) A+B (B)=GMI

A IS_EX() A G_Timer=GMI

Without EXCLUDE filter-mode, a router's process on receiving Current-
State Record is simple: when a router receives an IS_IN report, it
appends the reported source addresses to the previous source list
with their source timers set to GMI. Upon receiving an IS_EX()
report, the router sets the non-source-specific receiving states with
GMI by
resetting the group timer value and keeps the previous source list
without modification.

4.4. Reception of Source-List-Change and Filter-Mode-Change Records

On receiving Source-List-Change and Filter-Mode-Change Records, the
LW-IGMPv3 router needs to reset its group and source timers, update
its source list within the group, or trigger group queries. The
queries are sent by the router for the sources that are requested to
be no longer forwarded to a group. The table below describes the
state change and the actions that should be taken.

Old New
Source Source
Group Timer List Report Rec'd List Actions
------------ ------ ------------ ------ -------------

G_Timer == 0 A ALLOW(B) A+B (B)=GMI

G_Timer == 0 A BLOCK(B) A Send Q(G,A*B)

G_Timer == 0 A TO_IN(B) A+B (B)=GMI
Send Q(G,A-B)

G_Timer > 0 A ALLOW(B) A+B (B)=GMI

G_Timer > 0 A BLOCK(B) A Send Q(G,A*B)

G_Timer > 0 A TO_IN(B) A+B (B)=GMI
SendQ(G,A-B)
Send Q(G)

The table could be further simplified by merging duplicate lines:

Old New
Source Source
List Report Rec'd List Actions
------ ------------ ------ ----------------------

A ALLOW(B) A+B (B)=GMI

A BLOCK(B) A Send Q(G,A*B)

A TO_IN(B) A+B (B)=GMI
Send Q(G,A-B)
If G_Timer>0 Send Q(G)

In this table, TO_EX() report is not included because the processing
is exactly the same as that of IS_EX(), as described in the previous
section. Section 5.1 gives the lightweight routers's transformation
behavior between the two messages.

5. Interoperability

LW-IGMPv3/LW-MLDv2 hosts and routers should interoperate gracefully
with the full version protocols [IGMPv3, MLDv2]. [2][3]. Also, LW-IGMPv3/LW-
MLDv2 LW-IGMPv3/LW-MLDv2
hosts and routers should interoperate gracefully with hosts and
routers running IGMPv1/v2 or MLDv1.

5.1. Interoperation with the Full Version of IGMPv3

Eliminating EXCLUDE filter-mode from the full version protocols
simplifies the processes inside the host and router. On the other
hand,

LW-IGMPv3 does not introduce any change on the message format of the
group query and report messages the full version protocols use. Therefore, With
the elimination of the EXLCLUDE filter mode, the LW-IGMPv3 group
member sends a subset of IGMPv3 report messages, which can be
recognized by a multicast router running the full or the lightweight
IGMPv3 protocol on the same LAN.

A LW-IGMPv3 router translates does not process directly IS_EX(x) and TO_EX(x)
records that are used with by the full IGMPv3 but not used with LW-IGMPv3. IGMPv3. When a LW-
IGMPv3 LW-IGMPv3 router
receives these report messages from the full version host, it
translates them to IS_EX() records and makes the
corresponding behavior. behaves accordingly. All
possible record types are compared as follows:

IGMPv3 Report LW-IGMPv3 Equivalent
------------- --------------------

IS_IN(x) IS_IN(x)

IS_EX(x) IS_EX()

TO_IN(x) TO_IN(x)

TO_EX(x) IS_EX()

ALLOW(x) ALLOW(x)

BLOCK(x) BLOCK(x)

5.2. Interoperation with IGMPv1/IGMPv2

The LW-IGMPv3 protocol basically adopts the same Host/Group
Compatibility Mode and keeps Querier Present timers for IGMPv1 and
IGMPv2. Their definition and processing is the same as that of
IGMPv3.

5.2.1. Behavior of Group Members

A host's compatibility mode is determined from the Host Compatibility
Mode variable which can be in one of three states: IGMPv1, IGMPv2 or
IGMPv3. The Host Compatibility Mode of an interface is set to IGMPv2
and IGMPv2 Querier Present is set to Older Version Querier Present
Timeout second (defined in [IGMPv3]) [2]) whenever an IGMPv2 General Query is
received on that interface. The Host Compatibility Mode of an
interface is set to IGMPv1 and IGMPv1 Querier Present is set to Older
Version Querier Present Timeout second whenever an IGMPv1 Membership
Query is received on that interface. Based on the Host Compatibility
Mode variable, a host acts using the IGMPv3, IGMPv2, or IGMPv1
protocol on that interface interface.

While above manner is inherited from the definition of [IGMPv3], LW-
IGMPv3 [2], LW-IGMPv3
may enable to configure the Host Compatibility Mode variable by other
means: when a LW-IGMPv3 host is placed on a link where there are
IGMPv1/IGMPv2 hosts, a host may allow its IGMPv3 report message to be
suppressed by an IGMPv1 or IGMPv2 report message.

5.2.2. Behavior of Multicast Routers

If a LW-IGMPv3 router is on a network where at least one router
running IGMPv1 or IGMPv2 protocols, it is required that the lowest
version of querier must be used. This can be administratively
assured by supporting IGMPv1, IGMPv2 or IGMPv3 compatibility mode.

An LW-IGMPv3 router may be placed on a network where there are hosts
that have not been upgraded to IGMPv3. In order to be compatible
with the older version, the lightweight router should keep a Group
compatibility mode for each group record, and IGMPv1 and IGMPv2 Host
present timers are kept to switch gracefully between different
versions of IGMP.

When Group Compatibility mode is IGMPv2 or IGMPv1, a LW-IGMPv3 router
translates the following IGMPv2 or IGMPv1 messages for that group to
their IGMPv2 or IGMPv1 LW-IGMPv3 equivalents:

IGMP Message LW-IGMPv3 Equivalent
------------- --------------------

v1 Report IS_EX()

v2 Report IS_EX()

v2 Leave TO_IN()

6. Implementation Considerations

The lightweight protocols requires no additional burden procedure on the
implementation of the related protocols or systems, e.g. IGMP/MLD
snooping, multicast routing protocol, and operation of application
sockets, while the processing loads on the switches and routers that
running IGMPv3 (snooping) and multicast routing protocols could may be
greatly decreased.

In the following sections, the implementation related topics aspects are
described for the lightweight version protocols.

6.1. Implementation of Source-Specific Multicast

[IGMP-SSM]

[8] illustrates the requirements of implementation of Source-
Specific Source-Specific
Multicast (SSM) on IGMPv3/MLDv2 hosts and routers. The lightweight
protocol does not impose any bad influences on an SSM application.
The requirements of LW-IGMPv3/LW-MLDv2 for supporting SSM are
illustrated below.

A LW-IGMPv3/LW-MLDv2 host should not send a non-source-specific join,
i.e.
i.e., IS_EX(), and IGMPv2 Leave and MLDv1 Done messages for the
application whose multicast address is in the SSM address range. The
reception of a non-source-specific join with an SSM group address
should indicate an error to the application. The SSM-aware router
will ignore IS_EX() reports with SSM addresses. Other types of
Reports should be processed normally.

6.2. Implementation of Multicast Source Filter (MSF) APIs

Multicast Source Filter (MSF) APIs [MSF] [9] defines (1) IPv4 Basic MSF
API, (2) IPv4 Advanced MSF API, (3) Protocol-Independent Basic MSF
API, and (4) Protocol-Independent Advanced MSF API.

According to the MSF APIs definition, a LW-IGMPv3 host should
implement at least one of IPv4 Basic MSF API and Protocol-Independent
Basic MSF API, and a LW-MLDv2 host should implement Protocol-
Independent Basic MSF API. Other APIs, IPv4 Advanced MSF API and
Protocol-Independent Advanced MSF API, are optional to implement in
LW-IGMPv3/LW-MLDv2 host.

7. Security Considerations

The security consideration is considerations are the same as that of the full version
of IGMPv3/MLDv2.

8. References

8.1. Normative References

[KEYWORDS]

[1] Bradner, S., "Key words for use in RFCs to indicate requirement levels,"
levels", RFC 2119, March 1997.

[IGMPv3]

[2] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, A., "Internet Group Management Protocol, Version3," Version 3",
RFC 3376, October 2002.

[MLDv2]

[3] Vida, R. and L. Costa, L., "Multicast Listener Discovery Version 2
(MLDv2) for IPv6," IPv6", RFC 3810, June 2004.

9 Informative References

[SSM] Holbrook, H. and Cain, B., "Source-Specific Multicast

[4] Deering, S., "Host Extensions for IP," IP Multicasting", RFC 4607, 1112,
August 2006.

[IGMPv2] 1989.

[5] Fenner, W., "Internet Group Management Protocol, Version 2," 2",
RFC 2236, November 2373, July 1997.

[MLDv1]

[6] Deering, S., Fenner, W., and B. Haberman, B., "Multicast Listener
Discovery (MLD) for IPv6," IPv6", RFC 2710, October 1999.

[IGMP-SSM]

[7] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP",
RFC 4607, August 2006.

[8] Holbrook, H., Cain, B., and B. Haberman, B., "Using Internet Group
Management Protocol Version 3 (IGMPv3) and Multicast Listener
Discovery Protocol Version 2 (MLDv2) for Source-Specific
Multicast,"
Multicast", RFC 4604, August 2006.

[MSF]

8.2. Informative References

[9] Thaler, D., Fenner, B., and B. Quinn, B., "Socket Interface
Extensions for Multicast Source Filters," Filters", RFC 3678,
January 2004.

Author's Addressess

Authors' Addresses

Hui Liu
Huawei Technologies Co., Ltd.
Huawei Bld., No.3 Xinxi Rd., Rd.
Shang-Di Information Industry Base, Base
Hai-Dian Distinct, Beijing 100085, 100085
China

Email: Liuhui47967@huawei.com

Wei Cao
Huawei Technologies Co., Ltd.
Huawei Bld., No.3 Xinxi Rd., Rd.
Shang-Di Information Industry Base, Base
Hai-Dian Distinct, Beijing 100085, 100085
China

Email: caowayne@huawei.com

Hitoshi Asaeda
Keio University
Graduate School of Media and Governance
Keio University
5322 Endo, Endo
Fujisawa, Kanagawa 252-8520, 252-8520
Japan

Email: asaeda@wide.ad.jp

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Acknowledgment

The author would like to thank magma and mboned mailing lists for
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