MBONED Working Group H. Liu
Internet-Draft W. Cao
Expires: May 22, 2008 Huawei Technologies Co., Ltd.
H. Asaeda
Keio University
November 19, 2007
Lightweight IGMPv3 and MLDv2 Protocols
draft-ietf-mboned-lightweight-igmpv3-mldv2-02
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Copyright (C) The IETF Trust (2007).
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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.
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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 [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Simplification Method Overview . . . . . . . . . . . . . . . . 7
3.1. Behavior of Group Members . . . . . . . . . . . . . . . . 7
3.2. Behavior of Multicast Routers . . . . . . . . . . . . . . 7
4. LW-IGMPv3 Protocol for Group Members . . . . . . . . . . . . . 9
4.1. Query and Report Messages . . . . . . . . . . . . . . . . 9
4.2. Action on Change of Interface State . . . . . . . . . . . 9
4.3. Action on Reception of a Query . . . . . . . . . . . . . . 10
4.4. LW-IGMPv3 Group Record Types . . . . . . . . . . . . . . . 10
5. LW-IGMPv3 Protocol for Multicast Routers . . . . . . . . . . . 12
5.1. Group Timers and Source Timers in the Lightweight
Version . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. Source-Specific Forwarding Rules . . . . . . . . . . . . . 13
5.3. Reception of LW-IGMPv3 Group Records . . . . . . . . . . . 13
6. Interoperability . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Interoperation with the Full Version of IGMPv3/MLDv2 . . . 16
6.2. Interoperation with IGMPv1/IGMPv2 . . . . . . . . . . . . 16
6.2.1. Behavior of Group Members . . . . . . . . . . . . . . 16
6.2.2. Behavior of Multicast Routers . . . . . . . . . . . . 17
6.3. Interoperation with MLDv1 . . . . . . . . . . . . . . . . 18
7. Implementation Considerations . . . . . . . . . . . . . . . . 19
7.1. Implementation of Source-Specific Multicast . . . . . . . 19
7.2. Implementation of Multicast Source Filter (MSF) APIs . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.1. Normative References . . . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 23
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1. Introduction
IGMP version 3 [2] and MLD version 2 [3] implement source filtering
capabilities that are not supported by their earlier versions, IGMPv1
[4], IGMPv2 [5] and MLDv1 [6]. An IGMPv3 or MLDv2 capable host can
tell its upstream router which group it would like to join 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 learn sources which are of interest or which are
of not interested for a particular multicast address. This formation
is used during forwarding of multicast data packets.
INCLUDE and EXCLUDE filter-modes are introduced to support the source
filtering function. If a 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 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 timers and source timers are used
to maintain the forwarding state of desired groups and sources under
certain filter modes. When a group report arrives or a certain timer
expires, a multicast router 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 rules become relatively complex,
as the interface states could be frequently changed.
The multicast filter-mode improves the ability of the multicast
receiver to express its desires. It is useful to support Source-
Specific Multicast (SSM) [7] by specifying interesting source
addresses with INCLUDE mode. However, practical applications do not
use EXCLUDE mode to block sources very often, because a user or
application usually wants to specify desired source addresses, not
undesired source 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. It is
generally unnecessary to support the filtering function that blocks
sources.
This document proposes simplified versions of IGMPv3 and MLDv2, named
Lightweight IGMPv3 and Lightweight MLDv2 (or LW-IGMPv3 and LW-MLDv2).
LW-IGMPv3 and LW-MLDv2 support both ASM and SSM communications
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without a filtering function that blocks sources. Not only are they
compatible with the standard IGMPv3 and MLDv2, but also the protocol
operations made by hosts and routers or switches (performing IGMPv3/
MLDv2 snooping) are simplified to reduce the complicated operations.
Since LW-IGMPv3 and LW-MLDv2 are fully compatible with the full
version of these protocols (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.
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2. Terminology
Following notations are used in several places in this specification.
(*,G) join:
An operation triggered by a host that wants to join the group G. In
this case, the host receives from all sources sending to group G.
This is typical in the ASM communication.
(S,G) join:
An operation triggered by a host that wants to join the group G, with
specifying desired source S. In this case, the host receives only
from source S sending to group G.
INCLUDE (S,G) join:
An operation triggered by a host that wants to join a group G under
INCLUDE filter-mode, with specifying desired source S. The same
meaning of (S,G) join.
EXCLUDE (*,G) join:
An operation triggered by a host that wants to join a group G under
EXCLUDE filter-mode. The same meaning of (*,G) join.
EXCLUDE (S,G) join:
An operation triggered by a host that wants to join a group G under
EXCLUDE filter-mode, with specifying undesired source S. This
operation is not supported by LW-IGMPv3/LW-MLDv2.
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3. Simplification Method Overview
The principle is to simplify the host and router's behavior as much
as possible to improve efficiency, while guaranteeing
interoperability with the full versions, and introducing no side
effects on applications.
For convenience, this document mainly discusses IGMPv3, since MLDv2
inherits the same source filtering mechanism, but this document
additionally shows MLDv2's unique specifications when needed.
3.1. Behavior of Group Members
In 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, INCLUDE mode on the host part has the
same usage with the full version for INCLUDE (S,G) join, while
EXCLUDE mode on the host part is preserved only for excluding null
source-lists, which denotes a (*,G) join as used by IGMPv2/IGMPv1/
MLDv1. The detailed host operation of LW-IGMPv3/LW-MLDv2 is
described in Section 4.
3.2. Behavior of Multicast Routers
Router filter-mode is defined to optimize the state description of a
group membership [2][3]. 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, hosts primarily send INCLUDE requests, and also can
request an EXLUDE (*,G) join, which can be interpreted by the router
as a request to include all sources. Without the more general form
of EXCLUDE 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 a (*,G) join. Its basic
behavior is: when a router receives a (*,G) join, it will set its
group timer and keep the source list for sources specified in the
previously received source records. When the group timer expires,
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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. The detailed operation of router operation is described in
Section 5.
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4. LW-IGMPv3 Protocol for Group Members
4.1. Query and Report Messages
LW-IGMPv3 uses two sets of messages, i.e., Query and Report messages,
being the same as the full version protocols. There is no difference
between the definition and usage of the Query message. But the
report types in lightweight protocols are reduced because an
operation that triggers EXCLUDE (S,G) join is omitted.
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). LW-IGMPv3 inherits the action on change
of interface state and reception of a Query, but IS_IN and IS_EX
record types are eliminated and Current-State Records are noted by
other records. The following sections explain the details.
4.2. Action on Change of Interface State
When the state of an interface of a group member host is changed, a
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 4.4):
Old State New State State-Change Record Sent
----------- ----------- ------------------------
INCLUDE (A) INCLUDE (B) ALLOW(B-A), BLOCK(A-B)
INCLUDE (A) EXCLUDE ({}) TO_EX({})
INCLUDE ({}) EXCLUDE ({}) 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
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[2][3].)
4.3. 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 [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 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 the full version's rules that are used to
determine if a Report needs to be scheduled. The difference is
regarding the simplification of EXCLUDE filter-mode and the type of
Report as detailed in Section 4.4.
4.4. LW-IGMPv3 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:
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IGMPv3 LW-IGMPv3 Comments
-------- --------- -------------------------------------
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({}) 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. A multicast router creates the same state when it
receives a report message containing either IS_EX({}) or TO_EX({})
record types. Therefore, LW-IGMPv3 integrates the IS_EX({})
operation with the TO_EX({}) operation.
When a LW-IGMPv3 host needs to make a query response for the state of
INCLUDE (x,G) join, it makes a response whose message type is
expressed with ALLOW(x), instead of using the IS_IN record type.
Because the router's processing of the two messages is completely
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 the following situation: the host first launches an application
(AP1) that requests INCLUDE (x,G) join, and sends ALLOW(x). Then the
host launches another application (AP2) that joins (*,G), and it
sends 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.
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5. LW-IGMPv3 Protocol for Multicast Routers
The major difference between the full and lightweight version
protocols on the router part is that for the lightweight version
filter-mode is discarded and the function of the group timer is
redefined. The states maintained by the lightweight router are
reduced and the protocol operation is greatly simplified.
5.1. Group Timers and Source Timers in the Lightweight Version
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 for
transitioning the router's filter-mode from EXCLUDE to INCLUDE, is
redefined in the lightweight protocols to identify the non-source-
specific receiving states maintaining for (*,G) join. Once a group
record of TO_EX() is received, the group timer is set to represent
this (*,G) group join. The expiration of the group timer indicates
that there are no more listeners on the attached network for this
(*,G) group. Then if at this moment 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 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.
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5.2. 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, based on the
router filter-mode and source timer. In 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 is summarized as follows:
Group Timer Source Timer Action
------------ ------------------ -----------------------
G_Timer == 0 S_TIMER > 0 Suggest forwarding
traffic from source
G_Timer == 0 S_TIMER == 0 Suggest 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 forwarding
traffic from source
G_Timer > 0 No Source Elements Suggest forwarding
traffic from source
5.3. Reception of LW-IGMPv3 Group Records
On receiving LW-IGMPv3 group records, the LW-IGMPv3 router must act
upon these records and possible change their own states to reflect
the new desired membership state of the network.
Lightweight routers query sources that are requested to be no longer
forwarded to a group. When a router queries or receives a query for
a specific set of sources, it lowers its source timers for those
sources to a small interval of Last Member Query Time seconds. If
group records are received in response to the queries which express
interest in receiving traffic from the queried sources, the
corresponding timers are updated.
Similarly, when a router queries a specific group, it lowers its
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group timer for that group to a small interval of Last Member Query
Time seconds. If TO_EX({}) group records are received within the
interval, the group timer for the group is updated and the suggestion
to the routing protocol to forward the group stands without any
interruption.
During a query period (i.e., Last Member Query Time seconds), the
IGMP component in the router continues to suggest to the routing
protocol that it forwards traffic from the groups or sources that it
is querying. It is not until after Last Member Query Time seconds
without receiving a record expressing interest in the queried group
or sources that the router may prune the group or sources from the
network.
The following table describes the changes in group state and the
action(s) taken when receiving LW-IGMPV3 Group Record. This table
also describes the queries which are sent by the Querier when a
particular report is received. The notation in the table has the
same meaning as the full version defines [2][3]:
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 TO_IN(B) A+B (B)=GMI
Send Q(G,A-B)
Send Q(G)
G_Timer >= 0 A TO_EX({}) A (B)=GMI
In order to maintain protocol robustness, queries sent by actions in
the table need to be transmitted [Last Member Query Count] times,
once every [Last Member Query Interval] (These values are defined in
[2][3]).
If while scheduling new queries, there are already pending queries to
be retransmitted for the same group, the new and pending queries have
to be merged. In addition, received host reports for a group with
pending queries may affect the contents of those queries. The
process of building and maintaining the state of pending queries is
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described in [2][3].
The method which a lightweight router uses to build and send queries,
and the actions the router should take on receiving Queries from
other routers are completely the same as that of full version. The
detailed description is described in [2][3].
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6. Interoperability
LW-IGMPv3/LW-MLDv2 hosts and routers must interoperate with hosts and
routers of the full version [2][3]. Also, LW-IGMPv3/LW-MLDv2 hosts
and routers must interoperate gracefully with hosts and routers
running IGMPv1/v2 or MLDv1.
6.1. Interoperation with the Full Version of IGMPv3/MLDv2
LW-IGMPv3/LW-MLDv2 do not introduce any change on the message format
of the group query and report messages the full version protocols
use. 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 or LW-MLDv2 router does not process directly IS_IN(x),
IS_EX(x) and TO_EX(x) (except for TO_EX({})) records that are used by
the full version. When a LW-IGMPv3/LW-MLDv2 router receives these
report messages from the full version host, it MUST translate them
internally to the defined records and behaves accordingly. All
possible record types are defined as follows:
IGMPv3/MLDv2 Report LW-IGMPv3/LW-MLDv2 Equivalent
------------------- -----------------------------
IS_IN(x) ALLOW(x)
IS_EX(x) TO_EX({})
TO_EX(x) IS_EX()
6.2. Interoperation with IGMPv1/IGMPv2
6.2.1. 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 its IGMPv2 Querier Present timer is set to Older Version Querier
Present Timeout seconds (defined in [2]) whenever an IGMPv2 General
Query is received on that interface. The Host Compatibility Mode of
an interface is set to IGMPv1 and its IGMPv1 Querier Present timer is
set to Older Version Querier Present Timeout seconds 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.
In the presence of older version group members, LW-IGMPv3 hosts may
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allow its report message to be suppressed by either an IGMPv1 or
IGMPv2 membership report. However, because the transmission of
IGMPv1 or v2 packets reduces the capability of the LW-IGMPv3 system,
as a potential protection mechanism, the choice to enable or disable
the use of backward compatibility may be configurable.
6.2.2. 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.
If a router is not explicitly configured to use IGMPv1 or IGMPv2 and
hears an IGMPv1 Query or IGMPv2 General Query, it SHOULD log a
warning. These warnings MUST be rate-limited. When in IGMPv1 mode,
routers MUST send periodic IGMPv1 Queries and MUST ignore Leave Group
messages. They SHOULD also warn about receiving an IGMPv2 or IGMPv3
query (such warnings MUST be rate-limited). When in IGMPv2 mode,
routers MUST send periodic IGMPv2 Queries, and SHOULD also warn about
receiving an IGMPv3 query (such warnings MUST be rate-limited).
If an LW-IGMPv3 router is placed on a network where there are hosts
that have not been upgraded to IGMPv3, it MUST be able to operate in
version 1 or version 2 compatibility mode. The router keeps a
compatibility mode, an IGMPv1 Host Present Timer and an IGMPv2 Host
Present Timer (as defined in [2][3]) for each group record. The
IGMPv1 Host Present timer is set to Older Version Host Present
Timeout seconds whenever an IGMPv1 Membership Report is received.
The IGMPv2 Host Present timer is set to Older Version Host Present
Timeout seconds whenever an IGMPv2 Membership Report is received.
The Group Compatibility Mode of a group record changes whenever an
older version report (than the current compatibility mode) is heard
or when certain timer conditions occur. When the IGMPv1 Host Present
timer expires, the LW-IGMPv3 router switches to Group Compatibility
mode of IGMPv2 if it has a running IGMPv2 Host Present timer. If it
does not have a running IGMPv2 Host Present timer then it switches to
Group Compatibility of IGMPv3. When the IGMPv2 Host Present timer
expires and the IGMPv1 Host Present timer is not running, a router
switches to Group Compatibility mode of IGMPv3. Note that when a
group switches back to IGMPv3 mode, it takes some time to regain
source-specific state information.
When Group Compatibility mode is IGMPv2, a LW-IGMPv3 router
internally translates the following IGMPv2 messages for that group to
their LW-IGMPv3 equivalents:
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IGMPv2 Message LW-IGMPv3 Equivalent
-------------- --------------------
v2 Report TO_EX({})
v2 Leave TO_IN({})
When Group Compatibility mode is IGMPv1, a LW-IGMPv3 router
internally translates the following IGMPv1 and IGMPv2 messages for
that group to their IGMPv3 equivalents:
IGMPv1 Message LW-IGMPv3 Equivalent
-------------- --------------------
v1 Report TO_EX({})
6.3. Interoperation with MLDv1
The MLDv2 hosts and routers MUST interoperate with the hosts and
routers running MLDv1. The method is the same as described in
Section 6.2. The difference is that when a MLDv2 router has a MLDv1
listener on its network, it translates the following MLDv1 messages
to their MLDv2 equivalents:
MLDv1 Message LW-MLDv2 Equivalent
------------- -------------------
Report TO_EX({})
Done TO_IN({})
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7. Implementation Considerations
The lightweight protocols require no additional 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/MLDv2 (snooping) and multicast routing protocols may
be greatly decreased.
In the following sections, the implementation related aspects are
described for the lightweight version protocols.
7.1. Implementation of Source-Specific Multicast
[8] illustrates the requirements of implementation of 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 invoke a (*,G) join, i.e.,
TO_EX({}), and IGMPv2 Leave and MLDv1 Done messages for the
application whose multicast address is in the SSM address range. The
reception of a (*,G) join with an SSM group address should indicate
an error to the application. The SSM-aware router will ignore
TO_EX({}) reports with SSM addresses. Other types of Reports should
be processed normally.
7.2. Implementation of Multicast Source Filter (MSF) APIs
Multicast Source Filter (MSF) APIs [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.
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8. Security Considerations
The security considerations are the same as that of the full version
of IGMPv3/MLDv2.
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9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
[2] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, October 2002.
[3] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004.
[4] Deering, S., "Host Extensions for IP Multicasting", RFC 1112,
August 1989.
[5] Fenner, W., "Internet Group Management Protocol, Version 2",
RFC 2373, July 1997.
[6] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999.
[7] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP",
RFC 4607, August 2006.
[8] Holbrook, H., Cain, B., and B. Haberman, "Using Internet Group
Management Protocol Version 3 (IGMPv3) and Multicast Listener
Discovery Protocol Version 2 (MLDv2) for Source-Specific
Multicast", RFC 4604, August 2006.
9.2. Informative References
[9] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface
Extensions for Multicast Source Filters", RFC 3678,
January 2004.
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Authors' Addresses
Hui Liu
Huawei Technologies Co., Ltd.
Huawei Bld., No.3 Xinxi Rd.
Shang-Di Information Industry Base
Hai-Dian Distinct, Beijing 100085
China
Email: Liuhui47967@huawei.com
Wei Cao
Huawei Technologies Co., Ltd.
Huawei Bld., No.3 Xinxi Rd.
Shang-Di Information Industry Base
Hai-Dian Distinct, Beijing 100085
China
Email: caowayne@huawei.com
Hitoshi Asaeda
Keio University
Graduate School of Media and Governance
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Email: asaeda@wide.ad.jp
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