< draft-ietf-multimob-igmp-mld-tuning-05.txt   draft-ietf-multimob-igmp-mld-tuning-06.txt >
MULTIMOB Working Group H. Asaeda MULTIMOB Working Group H. Asaeda
Internet-Draft Keio University Internet-Draft Keio University
Intended status: Informational H. Liu Intended status: Informational H. Liu
Expires: September 8, 2012 Q. Wu Expires: September 27, 2012 Q. Wu
Huawei Huawei
March 7, 2012 March 26, 2012
Tuning the Behavior of IGMP and MLD for Routers in Mobile and Wireless Tuning the Behavior of IGMP and MLD for Routers in Mobile and Wireless
Networks Networks
draft-ietf-multimob-igmp-mld-tuning-05 draft-ietf-multimob-igmp-mld-tuning-06
Abstract Abstract
IGMP and MLD are the protocols used by hosts and multicast routers to IGMP and MLD are the protocols used by hosts and multicast routers to
exchange their IP multicast group memberships with each other. This exchange their IP multicast group memberships with each other. This
document describes the ways of IGMPv3 and MLDv2 protocol optimization document describes the ways of IGMPv3 and MLDv2 protocol optimization
for mobility, and aims to become a guideline for tuning of IGMPv3/ for mobility, and aims to become a guideline for tuning of IGMPv3/
MLDv2 Queries and timer and counter values. MLDv2 Queries and timer and counter values.
Status of this Memo Status of this Memo
skipping to change at page 1, line 37 skipping to change at page 1, line 37
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 8, 2012. This Internet-Draft will expire on September 27, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 3, line 11 skipping to change at page 3, line 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 10 10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Unicasting General Query . . . . . . . . . . . . . . 11 Appendix A. Unicasting General Query . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The Internet Group Management Protocol (IGMP) [1] for IPv4 and the The Internet Group Management Protocol (IGMP) [1] for IPv4 and the
Multicast Listener Discovery Protocol (MLD) [2] for IPv6 are the Multicast Listener Discovery Protocol (MLD) [2] for IPv6 are the
standard protocols for hosts to initiate joining or leaving of standard protocols for hosts to initiate joining or leaving of
multicast sessions. These protocols must be also supported by multicast sessions. These protocols must be also supported by
multicast routers or IGMP/MLD proxies [6] that maintain multicast multicast routers or IGMP/MLD proxies [5] that maintain multicast
membership information on their downstream interfaces. Conceptually, membership information on their downstream interfaces. Conceptually,
IGMP and MLD work on both wireless and mobile networks. However, IGMP and MLD work on both wireless and mobile networks. However,
wireless access technologies operate on a shared medium or a point- wireless access technologies operate on a shared medium or a point-
to-point link with limited spectrum and bandwidth. In many wireless to-point link with limited spectrum and bandwidth. In many wireless
regimes, it is desirable to minimize multicast-related signaling to regimes, it is desirable to minimize multicast-related signaling to
preserve the limited resources of battery powered mobile devices and preserve the limited resources of battery powered mobile devices and
the constrained transmission capacities of the networks. The motion the constrained transmission capacities of the networks. The motion
of a host may cause disruption of a multicast service initiation and of a host may cause disruption of a multicast service initiation and
termination in the new or previous network upon its movement. Slow termination in the new or previous network upon its movement. Slow
multicast service activation following a join may incur additional multicast service activation following a join may incur additional
delay in receiving multicast packets and degrade reception quality. delay in receiving multicast packets and degrade reception quality.
Slow service termination triggered by a rapid departure of the mobile Slow service termination triggered by a rapid departure of the mobile
host without leaving the group in the previous network may waste host without leaving the group in the previous network may waste
network resources. network resources.
When IGMP and MLD are used with mobile IP protocols, the proximity of When IGMP and MLD are used with mobile IP protocols, the proximity of
network entities should be considered. For example, when bi- network entities should be considered. For example, when bi-
directional tunnel is used with the mobility entities described in directional tunnel is used with the mobility entities described in
[7][8], the mobile host experiences additional latency, because the [6][7], the mobile host experiences additional latency, because the
round-trip time using bi-directional tunnel between mobility entities round-trip time using bi-directional tunnel between mobility entities
is larger comparing to the case that a host and an upstream router is larger comparing to the case that a host and an upstream router
attach to a LAN. attach to a LAN.
This document describes the ways of tuning the IGMPv3 and MLDv2 This document describes the ways of tuning the IGMPv3 and MLDv2
protocol behavior on multicast router and proxy side for wireless and protocol behavior on multicast router and proxy side for wireless and
mobile networks, including query and related timers tuning. The mobile networks, including query and related timers tuning. The
selective optimization that provides tangible benefits to the mobile selective optimization that provides tangible benefits to the mobile
hosts and routers is given by keeping track of downstream hosts' hosts and routers is given by keeping track of downstream hosts'
membership status and varying IGMP/MLD Query types and values to tune membership status and varying IGMP/MLD Query types and values to tune
the number of responses. The proposed behavior interoperates with the number of responses. This document does not make any changes to
the IGMPv3 and MLDv2 protocols. the IGMPv3 and MLDv2 protocls and only suggests optimal settings for
the configurable parameters of the protocols in mobile and wireless
environments.
2. Terminology 2. Terminology
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 [3].
In this document, "router" means both multicast router and IGMP/MLD In this document, "router" means both multicast router and IGMP/MLD
proxy. proxy.
3. Explicit Tracking of Membership Status 3. Explicit Tracking of Membership Status
Mobile hosts use IGMP and MLD to request to join or leave multicast Mobile hosts use IGMP and MLD to request to join or leave multicast
sessions. When an adjacent upstream router receives the IGMP/MLD sessions. When an adjacent upstream router receives the IGMP/MLD
Report messages, it recognizes the membership status on the link. To Report messages, it recognizes the membership status on the link. To
update the membership status reliably, the router sends IGMP/MLD update the membership status reliably, the router sends IGMP/MLD
Query messages periodically, and sends Group-Specific and/or Group- Query messages periodically, and sends Group-Specific and/or Group-
and-Source Specific Queries when a member host reports its leave. and-Source Specific Queries when a member host reports its leave.
IGMP/MLD Query is therefore necessary to obtain the up-to-date IGMP/MLD Query is therefore necessary to obtain the up-to-date
membership information, but a large number of the reply messages sent membership information, but a large number of the reply messages sent
from all member hosts MAY cause network congestion or consume network from all member hosts may cause network congestion or consume network
bandwidth. bandwidth.
The "explicit tracking function" [9] is the possible approach to The "explicit tracking function" [8] is the possible approach to
reduce the transmitted number of IGMP/MLD messages and contribute to reduce the transmitted number of IGMP/MLD messages and contribute to
the efficiency of mobile communications. It enables the router to the efficiency of mobile communications. It enables the router to
keep track of the membership status of the downstream IGMPv3 or MLDv2 keep track of the membership status of the downstream IGMPv3 or MLDv2
member hosts. That is, if a router enables the explicit tracking member hosts. That is, if a router enables the explicit tracking
function, it does not always need to ask Current-State Report function, it does not always need to ask Current-State Report
message's transmission from the receiver hosts since the router message's transmission from the receiver hosts since the router
implicitly recognizes the (potential) last member host when it implicitly recognizes the (potential) last member host when it
receives the State-Change Report reporting a leave. The router can receives the State-Change Report reporting a leave. The router can
therefore send IGMP/MLD Group-Specific and Group-and-Source Specific therefore send IGMP/MLD Group-Specific and Group-and-Source Specific
Queries LMQC/LLQC times (see Section 4.3 for LMQC/LLQC) only when it Queries LMQC/LLQC times (see Section 4.3 for LMQC/LLQC) only when it
skipping to change at page 4, line 41 skipping to change at page 4, line 41
Enabling the explicit tracking function is advantageous for mobile Enabling the explicit tracking function is advantageous for mobile
multicast, but the function requires additional processing capability multicast, but the function requires additional processing capability
and possibly a large memory for routers to keep all membership and possibly a large memory for routers to keep all membership
status. Especially when a router needs to maintain a large number of status. Especially when a router needs to maintain a large number of
receiver hosts, this resource requirement is potentially impacted. receiver hosts, this resource requirement is potentially impacted.
Therefore, in this document it is recommended that adjacent upstream Therefore, in this document it is recommended that adjacent upstream
multicast routers enable the explicit tracking function for IP multicast routers enable the explicit tracking function for IP
multicast communications on wireless and mobile networks, if they multicast communications on wireless and mobile networks, if they
have enough resources. If operators think that their routers do not have enough resources. If operators think that their routers do not
have enough resources, they MAY disable this function on their have enough resources, they may disable this function on their
routers. Note that whether routers enable the explicit tracking routers. Note that whether routers enable the explicit tracking
function or not, they need to maintain downstream membership status function or not, they need to maintain downstream membership status
by sending IGMPv3/MLDv2 General Query messages as some IGMPv3/MLDv2 by sending IGMPv3/MLDv2 General Query messages as some IGMPv3/MLDv2
messages MAY be lost during transmission. messages may be lost during transmission.
4. Tuning IGMP/MLD Timers and Values 4. Tuning IGMP/MLD Timers and Values
4.1. Tuning IGMP/MLD General Query Interval 4.1. Tuning IGMP/MLD General Query Interval
IGMP and MLD are non-reliable protocols; to cover the possibility of IGMP and MLD are non-reliable protocols; to cover the possibility of
a State-Change Report being missed by one or more multicast routers, a State-Change Report being missed by one or more multicast routers,
"hosts retransmit the same State-Change Report messages [Robustness "hosts retransmit the same State-Change Report messages [Robustness
Variable] - 1 more times", at intervals chosen at random from the Variable] - 1 more times", at intervals chosen at random from the
range (0, [Unsolicited Report Interval]) [1][2]. Although this range (0, [Unsolicited Report Interval]) [1][2]. Although this
behavior increases the protocol robustness, it does not guarantee behavior increases the protocol robustness, it does not guarantee
skipping to change at page 5, line 39 skipping to change at page 5, line 39
the IGMP/MLD Query message, for the case that a router enabling the the IGMP/MLD Query message, for the case that a router enabling the
explicit tracking function potentially operates a large number of explicit tracking function potentially operates a large number of
member hosts such as more than 200 hosts on the wireless link. This member hosts such as more than 200 hosts on the wireless link. This
longer interval value contributes to minimizing traffic of Report longer interval value contributes to minimizing traffic of Report
messages and battery power consumption for mobile hosts. messages and battery power consumption for mobile hosts.
On the other hand, this document also proposes 60 to 90 seconds for On the other hand, this document also proposes 60 to 90 seconds for
the [Query Interval] value for the case that a router enabling the the [Query Interval] value for the case that a router enabling the
explicit tracking function attaches to a wireless link with higher explicit tracking function attaches to a wireless link with higher
capacity. This shorter interval contributes to quick synchronization capacity. This shorter interval contributes to quick synchronization
of the membership information tracked by the router but MAY consume of the membership information tracked by the router but may consume
battery power of mobile hosts. battery power of mobile hosts.
If a router does not enable the explicit tracking function, the If a router does not enable the explicit tracking function, the
[Query Interval] value would be its default value, 125 seconds. [Query Interval] value would be its default value, 125 seconds.
In situations where Mobile IPv6 [8] is used, when the home agent In situations where Mobile IPv6 [7] is used, when the home agent
implements multicast router functionality and multicast data packets implements multicast router functionality and multicast data packets
are tunneled to and from the home agent, the home agent MAY want to are tunneled to and from the home agent, the home agent may want to
slow down Query periodicity. It happens, for example, when the home slow down Query periodicity. It happens, for example, when the home
agent detects network congestion. In this case, the home agent agent detects network congestion. In this case, the home agent
starts forwarding queries with the default [Query Interval] value and starts forwarding queries with the default [Query Interval] value and
increases the value in a gradual manner. increases the value in a gradual manner.
4.2. Tuning IGMP/MLD Query Response Interval 4.2. Tuning IGMP/MLD Query Response Interval
The [Query Response Interval] is the Max Response Time (or Max The [Query Response Interval] is the Max Response Time (or Max
Response Delay) used to calculate the Max Resp Code inserted into the Response Delay) used to calculate the Max Resp Code inserted into the
periodic General Queries. Its default value is 10 seconds expressed periodic General Queries. Its default value is 10 seconds expressed
skipping to change at page 6, line 29 skipping to change at page 6, line 29
tuning scenarios for tuning the [Query Response Interval] value in tuning scenarios for tuning the [Query Response Interval] value in
different wireless link conditions; one scenario is for a wireless different wireless link conditions; one scenario is for a wireless
link with a lower capacity of network resource or a lossy link, and link with a lower capacity of network resource or a lossy link, and
the other scenario is for a wireless link with enough capacity or the other scenario is for a wireless link with enough capacity or
reliable condition for IGMP/MLD message transmission. reliable condition for IGMP/MLD message transmission.
Regarding the first scenario, for instance, when a multicast router Regarding the first scenario, for instance, when a multicast router
attaches to a bursty IEEE 802.11b link, the router configures the attaches to a bursty IEEE 802.11b link, the router configures the
longer [Query Response Interval] value, such as 10 to 20 (sec). This longer [Query Response Interval] value, such as 10 to 20 (sec). This
configuration will reduce congestion of the Current-State Report configuration will reduce congestion of the Current-State Report
messages on a link but MAY increase join latency and leave latency messages on a link but may increase join latency and leave latency
when the unsolicited messages (State-Change Record) are lost on the when the unsolicited messages (State-Change Record) are lost on the
router. router. Note that as defined in Section 4.1.1 of [1], in IGMPv3, the
Max Resp Code larger than 128 represents the exponential values, and
changes the granularity. For example, if one wants to set the Max
Response Time to 20.0 seconds, the Max Resp Code should be expressed
with "0b10001001", which is divided into "mant=0b1001" and
"exp=0b000".
The second scenario MAY happen for a multicast router attaching to a The second scenario may happen for a multicast router attaching to a
wireless link having higher capacity of the resource or a point-to- wireless link having higher capacity of the resource or a point-to-
(multi-)point link such as an IEEE 802.16e link, because IGMP/MLD (multi-)point link such as an IEEE 802.16e link, because IGMP/MLD
messages do not seriously affect the link condition. The router can messages do not seriously affect the link condition. The router can
seek Current-State Report messages with the shorter [Query Response seek Current-State Report messages with the shorter [Query Response
Interval] value, such as 5 to 10 (sec). This configuration will Interval] value, such as 5 to 10 (sec). This configuration will
contribute to quickly (at some level) discovering non-tracked member contribute to quickly (at some level) discovering non-tracked member
hosts and synchronizing the membership information. hosts and synchronizing the membership information.
4.3. Tuning Last Member Query Timer (LMQT) and Last Listener Query 4.3. Tuning Last Member Query Timer (LMQT) and Last Listener Query
Timer (LLQT) Timer (LLQT)
skipping to change at page 7, line 6 skipping to change at page 7, line 11
Shortening the Last Member Query Timer (LMQT) for IGMPv3 and the Last Shortening the Last Member Query Timer (LMQT) for IGMPv3 and the Last
Listener Query Timer (LLQT) for MLDv2 contributes to minimizing leave Listener Query Timer (LLQT) for MLDv2 contributes to minimizing leave
latency. LMQT is represented by the Last Member Query Interval latency. LMQT is represented by the Last Member Query Interval
(LMQI), multiplied by the Last Member Query Count (LMQC), and LLQT is (LMQI), multiplied by the Last Member Query Count (LMQC), and LLQT is
represented by the Last Listener Query Interval (LLQI), multiplied by represented by the Last Listener Query Interval (LLQI), multiplied by
the Last Listener Query Count (LLQC). the Last Listener Query Count (LLQC).
While LMQI and LLQI are changeable, it is reasonable to use the While LMQI and LLQI are changeable, it is reasonable to use the
default values (i.e., 1 second) for LMQI and LLQI in a wireless default values (i.e., 1 second) for LMQI and LLQI in a wireless
network. LMQC and LLQC, whose default value is the [Robustness network. LMQC and LLQC, whose default value is the [Robustness
Variable] value, are also tunable. Therefore, LMQC and LLQC MAY be Variable] value, are also tunable. Therefore, LMQC and LLQC can be
set to "1" for routers enabling the explicit tracking function, and set to "1" for routers enabling the explicit tracking function, and
then LMQT and LLQT are set to 1 second. However, setting LMQC and then LMQT and LLQT are set to 1 second. However, setting LMQC and
LLQC to 1 increases the risk of missing the last member; LMQC and LLQC to 1 increases the risk of missing the last member; LMQC and
LLQC SHOULD be set to 1 only when network operators think that their LLQC ought to be set to 1 only when network operators think that
wireless link is stable enough. their wireless link is stable enough.
On the other hand, if network operators think that their wireless On the other hand, if network operators think that their wireless
link is lossy (e.g., due to a large number of attached hosts or link is lossy (e.g., due to a large number of attached hosts or
limited resources), they MAY set LMQC and LLQC to "2" for their limited resources), they can set LMQC and LLQC to "2" for their
routers enabling the explicit tracking function. Although bigger routers enabling the explicit tracking function. Although bigger
LMQC and LLQC values MAY cause longer leave latency, the risk of LMQC and LLQC values may cause longer leave latency, the risk of
missing the last member will be reduced. missing the last member will be reduced.
4.4. Tuning Startup Query Interval 4.4. Tuning Startup Query Interval
The [Startup Query Interval] is the interval between General Queries The [Startup Query Interval] is the interval between General Queries
sent by a Querier on startup. The default value is 1/4 of [Query sent by a Querier on startup. The default value is 1/4 of [Query
Interval]; however, in this document it is RECOMMENDED that the use Interval]; however, a shortened value such as 1 second would help
of its shortened value such as 1 second since the shorter value would
contribute to shortening handover delay for mobile hosts in, e.g., contribute to shortening handover delay for mobile hosts in, e.g.,
the base solution with PMIPv6 [10]. Note that the [Startup Query the base solution with PMIPv6 [9]. Note that the [Startup Query
Interval] is a static value and cannot be changed by any external Interval] is a static value and cannot be changed by any external
signal. Therefore operators who maintain routers and wireless links signal. Therefore operators who maintain routers and wireless links
MUST properly configure this value. need to properly configure this value.
4.5. Tuning Robustness Variable 4.5. Tuning Robustness Variable
To cover the possibility of unsolicited reports being missed by To cover the possibility of unsolicited reports being missed by
multicast routers, unsolicited reports are retransmitted [Robustness multicast routers, unsolicited reports are retransmitted [Robustness
Variable] - 1 more times, at intervals chosen at random from the Variable] - 1 more times, at intervals chosen at random from the
defined range [1][2]. The QRV (Querier's Robustness Variable) field defined range [1][2]. The QRV (Querier's Robustness Variable) field
in IGMP/MLD Query contains the [Robustness Variable] value used by in IGMP/MLD Query contains the [Robustness Variable] value used by
the querier. The default [Robustness Variable] value defined in the querier. The default [Robustness Variable] value defined in
IGMPv3 [1] and MLDv2 [2] is "2". IGMPv3 [1] and MLDv2 [2] is "2".
skipping to change at page 8, line 15 skipping to change at page 8, line 16
4.6. Tuning Scenarios for Various Mobile IP Networks 4.6. Tuning Scenarios for Various Mobile IP Networks
In mobile IP networks, IGMP and MLD are used either with three In mobile IP networks, IGMP and MLD are used either with three
deployment scenarios; (1) running directly between host and access deployment scenarios; (1) running directly between host and access
router on a wireless network, (2) running between host and home router on a wireless network, (2) running between host and home
router through a tunnel link, and (3) running between home router and router through a tunnel link, and (3) running between home router and
foreign router through a tunnel link. foreign router through a tunnel link.
When a receiver host connects directly through a wireless link to a When a receiver host connects directly through a wireless link to a
foreign access router or a home router, the tuning of the IGMP/MLD foreign access router or a home router, the tuning of the IGMP/MLD
protocol parameters SHOULD be the same as suggested in the previous protocol parameters should be the same as suggested in the previous
sections. The example of this scenario occurs when in Proxy Mobile sections. The example of this scenario occurs when in Proxy Mobile
IPv6 (PMIPv6) [7], the mobile access gateway, whose role is similar IPv6 (PMIPv6) [6], the mobile access gateway, whose role is similar
to a foreign router, acts as a multicast router or proxy. to a foreign router, acts as a multicast router or proxy.
The second scenario occurs when bi-directional tunnel established The second scenario occurs when bi-directional tunnel established
between host and home router is used to exchange IGMP/MLD messages between host and home router is used to exchange IGMP/MLD messages
such as in [8][11]. There are difficulties in tuning the parameters such as in [7][10]. There are difficulties in tuning the parameters
in this situation, because the tunnel link condition is diverse and in this situation, because the tunnel link condition is diverse and
changeable. When a host is far away from the home router, the changeable. When a host is far away from the home router, the
transmission delay between the two entities MAY be longer and the transmission delay between the two entities may be longer and the
packet delivery MAY be more unreliable. Thus the effects of the packet delivery may be more unreliable. Thus the effects of the
IGMP/MLD message transmission through a tunnel link SHOULD be IGMP/MLD message transmission through a tunnel link ought to be
considered during the parameter setting. For example, the [Query considered during the parameter setting. For example, the [Query
Interval] and [Query Response Interval] could be set shorter to Interval] and [Query Response Interval] could be set shorter to
compensate the transmission delay, and the [Robustness Variable] compensate the transmission delay, and the [Robustness Variable]
could be increased for possible packet loss. could be increased for possible packet loss.
The third scenario occurs in [10], in which the mobile access gateway The third scenario occurs in [9], in which the mobile access gateway
(i.e., foreign router) acts as the IGMP/MLD Proxy [6] in PMIPv6 [7]. (i.e., foreign router) acts as the IGMP/MLD Proxy [5] in PMIPv6 [6].
Through the bi-directional tunnel established with the local mobility Through the bi-directional tunnel established with the local mobility
anchor (i.e., home router), the mobile access gateway sends summary anchor (i.e., home router), the mobile access gateway sends summary
reports of its downstream member hosts to the local mobility anchor. reports of its downstream member hosts to the local mobility anchor.
Apart from the distance factor that influences the parameter setting, Apart from the distance factor that influences the parameter setting,
the [Query Response Interval] on the local mobility anchor could be the [Query Response Interval] on the local mobility anchor could be
set to a smaller value because the number of the mobile access set to a smaller value because the number of the mobile access
gateways is much smaller compared to that of the host and the chances gateways is much smaller compared to that of the host and the chances
of packet burst is low for the same reason. And the power of packet burst is low for the same reason. And the power
consumption due to a lower query interval is not an issue for the consumption due to a lower query interval is not an issue for the
moble access gateways because the mobile access gateways are usually moble access gateways because the mobile access gateways are usually
skipping to change at page 9, line 14 skipping to change at page 9, line 16
dynamically adjusting these timers and values is out of scope of this dynamically adjusting these timers and values is out of scope of this
document. document.
5. Destination Address of Specific Query 5. Destination Address of Specific Query
IGMP/MLD Group-Specific and Group-and-Source Specific Queries defined IGMP/MLD Group-Specific and Group-and-Source Specific Queries defined
in [1][2] are sent to verify whether there are hosts that desire in [1][2] are sent to verify whether there are hosts that desire
reception of the specified group or a set of sources or to rebuild reception of the specified group or a set of sources or to rebuild
the desired reception state for a particular group or a set of the desired reception state for a particular group or a set of
sources. These specific Queries build and refresh multicast sources. These specific Queries build and refresh multicast
membership state of hosts on an attached network. These specific membership state of hosts on an attached network.
Queries SHOULD be sent to all desired hosts with specific multicast
address (not the all-hosts/all-nodes multicast address) as their IP Group-specific queries are sent with an IP destination address equal
destination addresses, because hosts that do not join the multicast to the multicast address of interest, as defined in [1][2]. Using
session do not pay attention to these specific Queries, and only the multicast group of interest in the specific query is preferred in
active member hosts that have been receiving multicast contents with this environment because hosts that do not join the multicast session
the specified address reply IGMP/MLD reports. do not pay attention to these specific Queries, and only active
member hosts that have been receiving multicast contents with the
specified address reply to IGMP/MLD reports.
6. Interoperability 6. Interoperability
IGMPv3 [1] and MLDv2 [2] provide the ability for hosts to report IGMPv3 [1] and MLDv2 [2] provide the ability for hosts to report
source-specific subscriptions. With IGMPv3/MLDv2, a mobile host can source-specific subscriptions. With IGMPv3/MLDv2, a mobile host can
specify a channel of interest, using multicast group and source specify a channel of interest, using multicast group and source
addresses in its join request. Upon its reception, the upstream addresses in its join request. Upon its reception, the upstream
router that supports IGMPv3/MLDv2 establishes the shortest path tree router that supports IGMPv3/MLDv2 establishes the shortest path tree
toward the source without coordinating a shared tree. This function toward the source without coordinating a shared tree. This function
is called the source filtering function and is required to support is called the source filtering function and is required to support
Source-Specific Multicast (SSM) [4]. Source-Specific Multicast (SSM) [3].
Recently, the Lightweight-IGMPv3 (LW-IGMPv3) and Lightweight-MLDv2 Recently, the Lightweight-IGMPv3 (LW-IGMPv3) and Lightweight-MLDv2
(LW-MLDv2) [5] protocols have been defined as the proposed standard (LW-MLDv2) [4] protocols have been defined as the proposed standard
protocols in the IETF. These protocols provide protocol simplicity protocols in the IETF. These protocols provide protocol simplicity
for mobile hosts and routers, as they eliminate a complex state for mobile hosts and routers, as they eliminate a complex state
machine from the full versions of IGMPv3 and MLDv2, and promote the machine from the full versions of IGMPv3 and MLDv2, and promote the
opportunity to implement SSM in mobile communications. opportunity to implement SSM in mobile communications.
This document assumes that both multicast routers and mobile hosts This document assumes that both multicast routers and mobile hosts
MUST be IGMPv3/MLDv2 capable, regardless whether the protocols are are IGMPv3/MLDv2 capable, regardless whether the protocols are the
the full or lightweight version. And this document does not consider full or lightweight version. And this document does not consider
interoperability with older version protocols. One of the reasons interoperability with older version protocols. One of the reasons
not being interoperable with older IGMP/MLD protocols is that the not being interoperable with older IGMP/MLD protocols is that the
explicit tracking function does not work properly with older IGMP/MLD explicit tracking function does not work properly with older IGMP/MLD
protocols because of a report suppression mechanism; a host would not protocols because of a report suppression mechanism; a host would not
send a pending IGMP/MLD report if a similar report was sent by send a pending IGMP/MLD report if a similar report was sent by
another listener on the link. another listener on the link.
7. IANA Considerations 7. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
8. Security Considerations 8. Security Considerations
This document neither provides new functions or modifies the standard This document neither provides new functions or modifies the standard
functions defined in [1][2][5]. Therefore there is no additional functions defined in [1][2][4]. Therefore there is no additional
security consideration provided. security consideration provided.
9. Acknowledgements 9. Acknowledgements
Luis M. Contreras, Marshall Eubanks, Gorry Fairhurst, Dirk von Hugo, Luis M. Contreras, Marshall Eubanks, Gorry Fairhurst, Dirk von Hugo,
Imed Romdhani, Behcet Sarikaya, Stig Venaas, Jinwei Xia, and others Imed Romdhani, Behcet Sarikaya, Stig Venaas, Jinwei Xia, and others
provided many constructive and insightful comments. provided many constructive and insightful comments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[1] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. [1] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version 3", Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, October 2002. RFC 3376, October 2002.
[2] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 [2] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004. (MLDv2) for IPv6", RFC 3810, June 2004.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [3] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP",
Levels", March 1997.
[4] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP",
RFC 4607, August 2006. RFC 4607, August 2006.
[5] Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet Group [4] Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet Group
Management Protocol Version 3 (IGMPv3) and Multicast Listener Management Protocol Version 3 (IGMPv3) and Multicast Listener
Discovery Version 2 (MLDv2) Protocols", RFC 5790, Discovery Version 2 (MLDv2) Protocols", RFC 5790,
February 2010. February 2010.
10.2. Informative References 10.2. Informative References
[6] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet [5] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet
Group Management Protocol (IGMP) / Multicast Listener Discovery Group Management Protocol (IGMP) / Multicast Listener Discovery
(MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")",
RFC 4605, August 2006. RFC 4605, August 2006.
[7] Gundavelli, S, Ed., Leung, K., Devarapalli, V., Chowdhury, K., [6] Gundavelli, S, Ed., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[8] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in [7] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 6275, July 2011. IPv6", RFC 6275, July 2011.
[9] Asaeda, H. and N. Leymann, "IGMP/MLD-Based Explicit Membership [8] Asaeda, H. and N. Leymann, "IGMP/MLD-Based Explicit Membership
Tracking Function for Multicast Routers", Tracking Function for Multicast Routers",
draft-ietf-pim-explicit-tracking-00.txt (work in progress), draft-ietf-pim-explicit-tracking-00.txt (work in progress),
October 2011. October 2011.
[10] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base Deployment [9] Schmidt, T., Waehlisch, M., and S. Krishnan, "Base Deployment
for Multicast Listener Support in Proxy Mobile IPv6 (PMIPv6) for Multicast Listener Support in Proxy Mobile IPv6 (PMIPv6)
Domains", RFC 6224, April 2011. Domains", RFC 6224, April 2011.
[11] Perkins, Ed., C., "IP Mobility Support for IPv4, Revised", [10] Perkins, Ed., C., "IP Mobility Support for IPv4, Revised",
RFC 5944, November 2010. RFC 5944, November 2010.
Appendix A. Unicasting General Query Appendix A. Unicasting General Query
This appendix describes the possible IGMP and MLD protocol extensions
for further optimization in mobile and wireless environments. It
might be beneficial to include the following consideration when the
new version or modification of IGMP and MLD protocols are considered
in the future.
IGMPv3 and MLDv2 specifications [1][2] describe that a host MUST IGMPv3 and MLDv2 specifications [1][2] describe that a host MUST
accept and process any Query whose IP Destination Address field accept and process any Query whose IP Destination Address field
contains any of the addresses (unicast or multicast) assigned to the contains any of the addresses (unicast or multicast) assigned to the
interface on which the Query arrives. In general, the all-hosts interface on which the Query arrives. In general, the all-hosts
multicast address (224.0.0.1) or link-scope all-nodes multicast multicast address (224.0.0.1) or link-scope all-nodes multicast
address (FF02::1) is used as the IP destination address of IGMP/MLD address (FF02::1) is used as the IP destination address of IGMP/MLD
General Query. On the other hand, according to [1][2], a router MAY General Query. On the other hand, according to [1][2], a router may
be able to unicast General Query to the tracked member hosts in be able to unicast General Query to the tracked member hosts in
[Query Interval], if the router keeps track of membership information [Query Interval], if the router keeps track of membership information
(Section 3). (Section 3).
Unicasting IGMP/MLD General Query would reduce the drain on battery Unicasting IGMP/MLD General Query would reduce the drain on battery
power of mobile hosts as only the active hosts that have been power of mobile hosts as only the active hosts that have been
receiving multicast contents respond the unicast IGMP/MLD General receiving multicast contents respond the unicast IGMP/MLD General
Query messages and non-active hosts do not need to pay attention to Query messages and non-active hosts do not need to pay attention to
the IGMP/MLD Query messages. This also allows the upstream router to the IGMP/MLD Query messages. This also allows the upstream router to
proceed fast leaves (or shorten leave latency) by setting LMQC/LLQC proceed fast leaves (or shorten leave latency) by setting LMQC/LLQC
skipping to change at page 12, line 10 skipping to change at page 12, line 18
hosts do not retransmit the same join requests (i.e., unsolicited hosts do not retransmit the same join requests (i.e., unsolicited
Report messages), they lose the chance to join the channels unless Report messages), they lose the chance to join the channels unless
the upstream router asks the membership information by sending the upstream router asks the membership information by sending
General Query by multicast. It will be solved by using both unicast General Query by multicast. It will be solved by using both unicast
and multicast General Queries and configuring the [Query Interval] and multicast General Queries and configuring the [Query Interval]
timer value for multicast General Query and the [Unicast Query timer value for multicast General Query and the [Unicast Query
Interval] timer value for unicast General Query. However, using two Interval] timer value for unicast General Query. However, using two
different timers for General Queries would require the protocol different timers for General Queries would require the protocol
extension this document does not focus on. If a router does not extension this document does not focus on. If a router does not
distinguish the multicast and unicast General Query Intervals, the distinguish the multicast and unicast General Query Intervals, the
router SHOULD only use and enable multicast General Query. router should only use and enable multicast General Query.
Also, unicasting General Query does not remove multicasting General Also, unicasting General Query does not remove multicasting General
Query. Multicast General Query is necessary to update membership Query. Multicast General Query is necessary to update membership
information if it is not correctly synchronized due to missing information if it is not correctly synchronized due to missing
Reports. Therefore, enabling unicast General Query SHOULD NOT be Reports. Therefore, enabling unicast General Query should not be
used for the implementation that does not allow to configure used for the implementation that does not allow to configure
different query interval timers as [Query Interval] and [Unicast different query interval timers as [Query Interval] and [Unicast
Query Interval]. If a router does not distinguish these multicast Query Interval]. If a router does not distinguish these multicast
and unicast General Query Intervals, the router SHOULD only use and and unicast General Query Intervals, the router should only use and
enable multicast General Query. enable multicast General Query.
Authors' Addresses Authors' Addresses
Hitoshi Asaeda Hitoshi Asaeda
Keio University Keio University
Graduate School of Media and Governance Graduate School of Media and Governance
5322 Endo 5322 Endo
Fujisawa, Kanagawa 252-0882 Fujisawa, Kanagawa 252-0882
Japan Japan
 End of changes. 48 change blocks. 
66 lines changed or deleted 73 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/