Internet DRAFT - draft-ietf-pim-rfc1112bis
draft-ietf-pim-rfc1112bis
PIM S. E. Deering
Internet-Draft Retired
Obsoletes: 1112 (if approved) T. Eckert, Ed.
Updates: 791 (if approved) Futurewei Technologies USA
Intended status: Standards Track 18 October 2023
Expires: 20 April 2024
Host Extensions for "Any Source" IP Multicasting (ASM)
draft-ietf-pim-rfc1112bis-00
Abstract
This memo specifies the extensions required of a host implementation
of the Internet Protocol (IP) to support Any Source Multicast (ASM)
IP Multicasting or abbreviated IP Multicast. Distribution of this
memo is unlimited.
This document replaces [RFC1112] for anything but its specification
of the IGMP version 1 protocol.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on 20 April 2024.
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Table of Contents
1. STATUS OF THIS MEMO . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LEVELS OF CONFORMANCE . . . . . . . . . . . . . . . . . . . . 5
3.1. Level 0: no support for IP multicasting. . . . . . . . . 5
3.2. Level 1: support for sending but not receiving multicast IP
datagrams. . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Level 2: full support for IP multicasting. . . . . . . . 5
4. HOST GROUP ADDRESSES . . . . . . . . . . . . . . . . . . . . 6
5. MODEL OF A HOST IP IMPLEMENTATION . . . . . . . . . . . . . . 6
6. SENDING MULTICAST IP DATAGRAMS . . . . . . . . . . . . . . . 7
6.1. Extensions to the IP Service Interface . . . . . . . . . 7
6.2. Extensions to the IP Module . . . . . . . . . . . . . . . 8
6.3. Extensions to the Local Network Service Interface . . . . 9
6.4. Extensions to an Ethernet Local Network Module . . . . . 9
6.5. Extensions to Local Network Modules other than
Ethernet . . . . . . . . . . . . . . . . . . . . . . . . 9
7. RECEIVING MULTICAST IP DATAGRAMS . . . . . . . . . . . . . . 10
7.1. Extensions to the IP Service Interface . . . . . . . . . 10
7.2. Extensions to the IP Module . . . . . . . . . . . . . . . 11
7.3. Extensions to the Local Network Service Interface . . . . 12
7.4. Extensions to an Ethernet Local Network Module . . . . . 12
7.5. Extensions to Local Network Modules other than
Ethernet . . . . . . . . . . . . . . . . . . . . . . . . 13
8. Normative changes . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Moving RFC1112 and IGMPv1 to historic status . . . . . . 13
8.2. Backward compatibility with IGMPv1 . . . . . . . . . . . 13
9. Changes from RFC1112 . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative language . . . . . . . . . . . . . . . . . . . 14
9.2. Superceeding references to IGMPv1 . . . . . . . . . . . . 14
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9.3. Introduction of the term Any-Source Multicast (ASM) . . . 14
9.4. Applicability to both IP and IPv6 . . . . . . . . . . . . 14
9.5. Standard for IP multicasting in controlled networks . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. HOST GROUP ADDRESS ISSUES . . . . . . . . . . . . . 18
A.1. Group Address Binding . . . . . . . . . . . . . . . . . . 18
A.2. Allocation of Transient Host Group Addresses . . . . . . 19
Appendix B. Discussion and Explanations (TO BE REMOVED) . . . . 19
B.1. Goals of this document . . . . . . . . . . . . . . . . . 19
B.2. Internet Standard status . . . . . . . . . . . . . . . . 20
B.3. Authors email . . . . . . . . . . . . . . . . . . . . . . 21
B.4. Changelog . . . . . . . . . . . . . . . . . . . . . . . . 21
B.5. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 21
B.5.1. draft-ietf-pim-rfc1112bis-00 . . . . . . . . . . . . 22
B.5.2. draft-eckert-pim-rfc1112bis-02 . . . . . . . . . . . 22
B.5.3. draft-eckert-pim-rfc1112bis-01 . . . . . . . . . . . 22
B.5.4. draft-eckert-pim-rfc1112bis-00 . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. STATUS OF THIS MEMO
This memo specifies the extensions required of a host implementation
of the Internet Protocol (IP) to support Any Source Multicast (ASM)
IP Multicasting or abbreviated IP Multicast. Distribution of this
memo is unlimited.
This document replaces [RFC1112] for anything but its specification
of the IGMP version 1 protocol.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. INTRODUCTION
The host extensions defined in this memo are called Any Source
Multicast (ASM) IP multicast or abbreviated IP multicast. The term
Any Source Multicast is used to distinguish these extensions from
Source Specific Multicast (SSM) IP multicast as defined by [SSM].
The abbreviation IP multicast always refers to this memo's
extensions.
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This memo applies to both IP and IPv6. When it uses the term IP it
implies either or both version of the IP protocol. It uses the terms
IP and/or IPv6 explicitly when referring to functions applicable to
only a specific version of the IP protocol.
This document replaces [RFC1112] for anything but the specification
of IGMP version 1 in Appendix I. of [RFC1112]. See Section 8 and
Section 9 for a detailled list of changes from that memo.
IP multicasting is the transmission of an IP datagram to a "host
group", a set of zero or more hosts identified by a single IP
destination address. A multicast datagram is delivered to all
members of its destination host group with the same "best-efforts"
reliability as regular unicast IP datagrams, i.e., the datagram is
not guaranteed to arrive intact at all members of the destination
group or in the same order relative to other datagrams.
The membership of a host group is dynamic; that is, hosts may join
and leave groups at any time. There is no restriction on the
location or number of members in a host group. A host may be a
member of more than one group at a time. A host need not be a member
of a group to send datagrams to it.
A host group may be permanent or transient. A permanent group has a
well-known, administratively assigned IP address. It is the address,
not the membership of the group, that is permanent; at any time a
permanent group may have any number of members, even zero. Those IP
multicast addresses that are not reserved for permanent groups are
available for dynamic assignment to transient groups which exist only
as long as they have members.
Internetwork forwarding of IP multicast datagrams is handled by
"multicast routers" which may be co-resident with, or separate from,
internet gateways. A host transmits an IP multicast datagram as a
local network multicast which reaches all immediately-neighboring
members of the destination host group. If the datagram has an IP
time-to-live greater than 1, the multicast router(s) attached to the
local network take responsibility for forwarding it towards all other
networks that have members of the destination group. On those other
member networks that are reachable within the IP time-to-live, an
attached multicast router completes delivery by transmitting the
datagram as a local multicast.
This memo specifies the extensions required of a host IP
implementation to support IP multicasting, where a "host" is any
internet host or gateway other than those acting as multicast
routers. The algorithms and protocols used within and between
multicast routers are transparent to hosts and will be specified in
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separate documents. This memo also does not specify how local
network multicasting is accomplished for all types of network,
although it does specify the required service interface to an
arbitrary local network and gives an Ethernet specification as an
example. Specifications for other types of network will be the
subject of future memos.
3. LEVELS OF CONFORMANCE
There are three levels of conformance to this specification:
3.1. Level 0: no support for IP multicasting.
There is, at this time, no requirement that all IP implementations
support IP multicasting. Level 0 hosts will, in general, be
unaffected by multicast activity. The only exception arises on some
types of local network, where the presence of level 1 or 2 hosts may
cause misdelivery of multicast IP datagrams to level 0 hosts. Such
datagrams can easily be identified by the presence of a class D IP
address in their destination address field; they SHOULD be quietly
discarded by hosts that do not support IP multicasting. Class D
addresses are described in section 4 of this memo.
3.2. Level 1: support for sending but not receiving multicast IP
datagrams.
Level 1 allows a host to partake of some multicast-based services,
such as resource location or status reporting, but it does not allow
a host to join any host groups. An IP implementation may be upgraded
from level 0 to level 1 very easily and with little new code. Only
sections 4, 5, and 6 of this memo are applicable to level 1
implementations.
3.3. Level 2: full support for IP multicasting.
Level 2 allows a host to join and leave host groups, as well as send
IP datagrams to host groups. Most IPv6 hosts require Level 2 support
because IPv6 Neighbor Discovery ([RFC4861], as used on most link
types) depends on multicast and requires that nodes join Solicited
Node multicast addresses.
Level 2 requires implementation of the Internet Group Management
Protocol (IGMP) for IP and the equivalent Multicast Listener
Discovery Protocol (MLD) for IPv6 and extension of the IP and local
network service interfaces within the host.
The current protocol versions are [IGMPv3] and [MLDv2] or lightweight
versions of either protocol [IGMPv3LITE].
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All of the following sections of this memo are applicable to level 2
implementations.
4. HOST GROUP ADDRESSES
IP Host groups are identified by class D IP addresses, i.e., those
with "1110" as their high-order four bits. Class E IP addresses,
i.e., those with "1111" as their high-order four bits, are reserved
for future addressing modes.
In Internet standard "dotted decimal" notation, host group addresses
range from 224.0.0.0 to 239.255.255.255. The address 224.0.0.0 is
guaranteed not to be assigned to any group, and 224.0.0.1 is assigned
to the permanent group of all IP hosts (including gateways). This is
used to address all IP multicast hosts on the directly connected
network. There is no multicast address (or any other IP address) for
all hosts on the total Internet. The addresses of other well-known,
permanent groups are to be published in "Assigned Numbers".
IPv6 Host groups are identified by IPv6 addresses as defined in
[RFC4291] section 2.7 and updated by [RFC7346], [RFC7371].
IP and IPv6 addresses as specified in [SSM] are not used for ASM IP
multicast and are not considered IP host groups. They are instead
only the destination address part G of Source Specific Multicast
(SSM) IP multicast (S,G) channels.
Appendix I contains some background discussion of several issues
related to host group addresses.
5. MODEL OF A HOST IP IMPLEMENTATION
The multicast extensions to a host IP implementation are specified in
terms of the layered model illustrated below in Figure 1. In this
model, ICMP/ICMPv6 and (for level 2 hosts) IGMP/MLD are considered to
be implemented within the IP module, and the mapping of IP addresses
to local network addresses is considered to be the responsibility of
local network modules. This model is for expository purposes only,
and should not be construed as constraining an actual implementation.
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| |
| Upper-Layer Protocol Modules |
|__________________________________________________________|
--------------------- IP Service Interface -----------------------
__________________________________________________________
| | | |
| | IP: | IPv6: |
| | ICMP+ICMP | ICMPv6+MLD |
| IP [IP and/or IPv6] |______________|______________|
| Module(s) |
| |
|__________________________________________________________|
---------------- Local Network Service Interface -----------------
__________________________________________________________
| | |
| Local | IP-to-local address mapping |
| Network | (e.g., ARP/ND) |
| Modules |_____________________________|
| (e.g., Ethernet) |
| |
Figure 1: multicast extensions to a host IP implementation
To provide level 1 multicasting, a host IP implementation MUST
support the transmission of multicast IP datagrams. To provide level
2 multicasting, a host MUST also support the reception of multicast
IP datagrams. Each of these two new services is described in a
separate section, below. For each service, extensions are specified
for the IP service interface, the IP module, the local network
service interface, and an Ethernet local network module. Extensions
to local network modules other than Ethernet are mentioned briefly,
but are not specified in detail.
6. SENDING MULTICAST IP DATAGRAMS
6.1. Extensions to the IP Service Interface
Multicast IP datagrams are sent using the same "Send IP" operation
used to send unicast IP datagrams; an upper-layer protocol module
merely specifies an IP host group address, rather than an individual
IP address, as the destination. However, a number of extensions may
be necessary or desirable.
First, the service interface SHOULD provide a way for the upper-layer
protocol to specify the IP time-to-live of an outgoing multicast
datagram, if such a capability does not already exist. If the upper-
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layer protocol chooses not to specify a time-to-live, it SHOULD
default to 1 for all multicast IP datagrams, so that an explicit
choice is required to multicast beyond a single network.
Second, for hosts that may be attached to more than one network, the
service interface SHOULD provide a way for the upper-layer protocol
to identify which network interface is be used for the multicast
transmission. Only one interface is used for the initial
transmission; multicast routers are responsible for forwarding to any
other networks, if necessary. If the upper-layer protocol chooses
not to identify an outgoing interface, a default interface SHOULD be
used, preferably under the control of system management.
Third (level 2 implementations only), for the case in which the host
is itself a member of a group to which a datagram is being sent, the
service interface SHOULD provide a way for the upper-layer protocol
to inhibit local delivery of the datagram; by default, a copy of the
datagram is looped back. This is a performance optimization for
upper-layer protocols that restrict the membership of a group to one
process per host (such as a routing protocol), or that handle
loopback of group communication at a higher layer (such as a
multicast transport protocol).
IPv6 socket extensions supporting these functions are defined in
[RFC3493], section 5.2.
6.2. Extensions to the IP Module
To support the sending of multicast IP datagrams, the IP module MUST
be extended to recognize IP host group addresses when routing
outgoing datagrams. Most IP implementations include the following
logic:
if IP-destination is on the same local network,
send datagram locally to IP-destination
else
send datagram locally to GatewayTo( IP-destination )
To allow multicast transmissions, the routing logic MUST be changed
to:
if IP-destination is on the same local network
or IP-destination is a host group,
send datagram locally to IP-destination
else
send datagram locally to GatewayTo( IP-destination )
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If the sending host is itself a member of the destination group on
the outgoing interface, a copy of the outgoing datagram MUST be
looped-back for local delivery, unless inhibited by the sender.
(Level 2 implementations only.)
The IP source address of the outgoing datagram MUST be one of the
individual addresses corresponding to the outgoing interface.
A host group address MUST never be placed in the source address field
or anywhere in a source route or record route option of an outgoing
IP datagram. These packets are not IP Multicast packets but simply
invalid packets.
6.3. Extensions to the Local Network Service Interface
No change to the local network service interface is required to
support the sending of multicast IP datagrams. The IP module merely
specifies an IP host group destination, rather than an individual IP
destination, when it invokes the existing "Send Local" operation.
6.4. Extensions to an Ethernet Local Network Module
The Ethernet directly supports the sending of local multicast packets
by allowing multicast addresses in the destination field of Ethernet
packets. All that is needed to support the sending of multicast IP
datagrams is a procedure for mapping IP host group addresses to
Ethernet multicast addresses.
An IP host group address is mapped to an Ethernet multicast address
by placing the low-order 23-bits of the IP address into the low-order
23 bits of the Ethernet multicast address 01-00-5E-00-00-00 (hex).
Because there are 28 significant bits in an IP host group address,
more than one host group address may map to the same Ethernet
multicast address.
Mapping of IPv6 host group addresses to Ethernet is defined in
[RFC2464] and [RFC6085].
6.5. Extensions to Local Network Modules other than Ethernet
Other networks that directly support multicasting, such as rings or
buses conforming to the IEEE 802.2 standard, may be handled the same
way as Ethernet for the purpose of sending multicast IP datagrams.
For a network that supports broadcast but not multicast, such as the
Experimental Ethernet, all IP host group addresses may be mapped to a
single local broadcast address (at the cost of increased overhead on
all local hosts). For a point-to-point link joining two hosts (or a
host and a multicast router), multicasts SHOULD be transmitted
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exactly like unicasts. For a store-and-forward network like the
ARPANET or a public X.25 network, all IP host group addresses might
be mapped to the well-known local address of an IP multicast router;
a router on such a network would take responsibility for completing
multicast delivery within the network as well as among networks.
7. RECEIVING MULTICAST IP DATAGRAMS
7.1. Extensions to the IP Service Interface
Incoming multicast IP datagrams are received by upper-layer protocol
modules using the same "Receive IP" operation as normal, unicast
datagrams. Selection of a destination upper-layer protocol is based
on the protocol field in the IP header, regardless of the destination
IP address. However, before any datagrams destined to a particular
group can be received, an upper-layer protocol must ask the IP module
to join that group. Thus, the IP service interface MUST be extended
to provide two new operations:
JoinHostGroup ( group-address, interface )
LeaveHostGroup ( group-address, interface )
The JoinHostGroup operation requests that this host become a member
of the host group identified by "group-address" on the given network
interface. The LeaveGroup operation requests that this host give up
its membership in the host group identified by "group-address" on the
given network interface. The interface argument may be omitted on
hosts that support only one interface. For hosts that may be
attached to more than one network, the upper-layer protocol may
choose to leave the interface unspecified, in which case the request
will apply to the default interface for sending multicast datagrams
(see section 6.1).
It is permissible to join the same group on more than one interface,
in which case duplicate multicast datagrams may be received. It is
also permissible for more than one upper-layer protocol to request
membership in the same group.
Both operations SHOULD return immediately (i.e., they are non-
blocking operations), indicating success or failure. Either
operation may fail due to an invalid group address or interface
identifier. JoinHostGroup may fail due to lack of local resources.
LeaveHostGroup may fail because the host does not belong to the given
group on the given interface. LeaveHostGroup may succeed, but the
membership persist, if more than one upper-layer protocol has
requested membership in the same group.
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IPv6 socket extensions supporting these functions are defined in
[RFC3493], section 5.2. [RFC3678] specifies these functions for IP
and IPv6 (as well as for SSM). Note that these are UDP socket
extions (and not IP/IPv6 socket extensions due to the absence of
widely available/used IP/IPv6 level socket APIs).
7.2. Extensions to the IP Module
To support the reception of multicast IP datagrams, the IP module
MUST be extended to maintain a list of host group memberships
associated with each network interface. An incoming datagram
destined to one of those groups is processed exactly the same way as
datagrams destined to one of the host's individual addresses.
Incoming datagrams destined to groups to which the host does not
belong are discarded without generating any error report or log
entry. On hosts with more than one network interface, if a datagram
arrives via one interface, destined for a group to which the host
belongs only on a different interface, the datagram is quietly
discarded. (These cases should occur only as a result of inadequate
multicast address filtering in a local network module.)
An incoming datagram is not rejected for having an IP time-to-live of
1 (i.e., the time-to-live should not automatically be decremented on
arriving datagrams that are not being forwarded). An incoming
datagram with an IP host group address in its source address field is
quietly discarded. An ICMP/ICMPv6 error message (Destination
Unreachable, Time Exceeded, Parameter Problem, Source Quench, or
Redirect) is never generated in response to a datagram destined to an
IP host group.
The list of host group memberships is updated in response to
JoinHostGroup and LeaveHostGroup requests from upper-layer protocols.
Each membership should have an associated reference count or similar
mechanism to handle multiple requests to join and leave the same
group. On the first request to join and the last request to leave a
group on a given interface, the local network module for that
interface is notified, so that it may update its multicast reception
filter (see section 7.3).
The IP module MUST also be extended to implement the IGMP protocol
for IP and/or the MLD protocol for IPv6 (depending on the version of
IP to be supported). IGMP/MLD are used to keep neighboring multicast
routers informed of the host group memberships present on a
particular local network.
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7.3. Extensions to the Local Network Service Interface
Incoming local network multicast packets are delivered to the IP
module using the same "Receive Local" operation as local network
unicast packets. To allow the IP module to tell the local network
module which multicast packets to accept, the local network service
interface is extended to provide two new operations:
JoinLocalGroup ( group-address )
LeaveLocalGroup ( group-address )
where "group-address" is an IP host group address. The
JoinLocalGroup operation requests the local network module to accept
and deliver up subsequently arriving packets destined to the given IP
host group address. The LeaveLocalGroup operation requests the local
network module to stop delivering up packets destined to the given IP
host group address. The local network module is expected to map the
IP host group addresses to local network addresses as required to
update its multicast reception filter. Any local network module is
free to ignore LeaveLocalGroup requests, and may deliver up packets
destined to more addresses than just those specified in
JoinLocalGroup requests, if it is unable to filter incoming packets
adequately.
The local network module MUST NOT deliver up any multicast packets
that were transmitted from that module; loopback of multicasts is
handled at the IP layer or higher.
7.4. Extensions to an Ethernet Local Network Module
To support the reception of multicast IP datagrams, an Ethernet
module MUST be able to receive packets addressed to the Ethernet
multicast addresses that correspond to the host's IP host group
addresses. It is highly desirable to take advantage of any address
filtering capabilities that the Ethernet hardware interface may have,
so that the host receives only those packets that are destined to it.
Unfortunately, many current Ethernet interfaces have a small limit on
the number of addresses that the hardware can be configured to
recognize. Nevertheless, an implementation MUST be capable of
listening on an arbitrary number of Ethernet multicast addresses,
which may mean "opening up" the address filter to accept all
multicast packets during those periods when the number of addresses
exceeds the limit of the filter.
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For interfaces with inadequate hardware address filtering, it may be
desirable (for performance reasons) to perform Ethernet address
filtering within the software of the Ethernet module. This is not
mandatory, however, because the IP module performs its own filtering
based on IP destination addresses.
7.5. Extensions to Local Network Modules other than Ethernet
Other multicast networks, such as IEEE 802.2 networks, can be handled
the same way as Ethernet for the purpose of receiving multicast IP
datagrams. For pure broadcast networks, such as the Experimental
Ethernet, all incoming broadcast packets can be accepted and passed
to the IP module for IP-level filtering. On point-to-point or store-
and-forward networks, multicast IP datagrams will arrive as local
network unicasts, so no change to the local network module should be
necessary.
8. Normative changes
8.1. Moving RFC1112 and IGMPv1 to historic status
This document moves [RFC1112] to historic status so that the IGMP
version 1 protocol as specified in Appendix 1 of [RFC1112] is moved
to historic status. This protocol is not included in the text of
this document anymore, which hence renders IGMPv1 historic.
All other aspects of [RFC1112] beside IGMPv1 are inherited and
enhanced by this document and maintain their current Internet
Standard designation from [RFC1112] through the normative status of
this document.
8.2. Backward compatibility with IGMPv1
Newer versions of IGMP or other protocols/mechisms including but not
necessary limited to [IGMPv2], [IGMPv3] or [IGMPv3LITE] do or may
(such as in [IGMPsnooping]) include backward compatibility with
IGMPv1, which requires the [RFC1112] specification of IGMPv1.
This document does not ask for any change to any specifications or
implementations that includes any form of support for IGMPv1 for
backward compatibility reasons as long as it also includes
compatibility with a newer version of IGMP starting with [IGMPv2].
Any new or updated specification with such backward compatibility
needs to continue to reference the specification of IGMPv1 in
[RFC1112]. Any future reference for new or updated work to any other
definition from [RFC1112] needs to refer to this document instead.
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9. Changes from RFC1112
Beyond the normative changes described in Section 8, this document
introduces the following changes over [RFC1112].
9.1. Normative language
This document introduces the use of normative language through
capitalization. [RFC1112] preceeded this method and hence did not
have this.
TBD: This version is an initial run across the text to find the
appropriate places. It may be incomplete.
9.2. Superceeding references to IGMPv1
References to IGMPv1 in [RFC1112] are replaced by references to
[IGMPv3] in this text.
9.3. Introduction of the term Any-Source Multicast (ASM)
This update introduces the term "ASM IP multicast" (ASM) as another
term for "Host Extensions for IP multicast". This term was
introduced when [SSM] introduced another service model for IP
Multicast called "Source Specific Multicast" (SSM), and hence, the
service described in [RFC1112] and this update is more precisely
called Any Source Multicast (ASM) IP multicast.
[RFC1112] defines and uses the term "host group". This term is not
applicable to IP/IPv6 multicast group addresses that are not used for
ASM but SSM according to [SSM]. New text in this document explains
this.
No functional changes to the IP Multicast service are incurred by
these changes.
9.4. Applicability to both IP and IPv6
This update is written to apply to both IP and IPv6 by adding
equivalent detail for IPv6 where [RFC1112] only covered IP:
addressing and protocols in support of the service - Multicast
Listener Discovery [MLDv2] for IPv6 versus IGMP for IP.
Note: IPv6 documents such as [RFC1883] and all its updates (e.g.:
[RFC8200]) are defining multicasting in the assumption of the service
of [RFC1112] for IPv6, but without being able to refer to [RFC1112],
as it was only defined for IP. Future documents can refer to this
document as the IP Multicast / ASM service for both IP and IPv6.
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Additional text provides references for IETF UDP socket API
specifications that instantiate the abstract APIs defined in this
document.
No functional changes to the IP Multicast service are incurred by
these text changes.
9.5. Standard for IP multicasting in controlled networks
This document removes the claim in the abstract of [RFC1112], that
these host extensions are "... the recommended standard for IP
multicasting in the Internet."
The reason for this is that [RFC8815] deprecated the ASM Service
across the Internet because there is no Internet Standard solution
for protocols to support interdomain ASM except for [RFC3956], which
is only applicable to IPv6, and even that solution does not resolve
the challenges to source access control in interdomain deployments.
In result, ASM is today "only" a recommended solution for controlled
networks including controlled federated networks for applications for
which SSM is not usable.
However, these limitations to the applicability of ASM to no impact
the applicability of most of the host stack described in this
document for other forms of IP Multicast, specifically "Source
Specific Multicast", [SSM], which inherits all aspects of ASM
specified in this document, especially the sending (Section 6,
Section 6.2) of IP Multicast packets as well as the mapping to
ethernet (Section 6.4). It only amends the joining of IP Multicast
traffic on IP Multicast receivers with additional procedures fitting
into the host stack described in this document.
10. References
10.1. Normative References
[IGMPv2] Fenner, W., "Internet Group Management Protocol, Version
2", RFC 2236, DOI 10.17487/RFC2236, November 1997,
<https://www.rfc-editor.org/rfc/rfc2236>.
[IGMPv3] Haberman, B. and J. Martin, "Internet Group Management
Protocol Version 3 (IGMPv3) / Multicast Listener Discovery
Version 2 (MLDv2) and Multicast Routing Protocol
Interaction", RFC 5186, DOI 10.17487/RFC5186, May 2008,
<https://www.rfc-editor.org/rfc/rfc5186>.
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[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5,
RFC 1112, DOI 10.17487/RFC1112, August 1989,
<https://www.rfc-editor.org/rfc/rfc1112>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<https://www.rfc-editor.org/rfc/rfc2464>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/rfc/rfc4291>.
[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/rfc/rfc791>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/rfc/rfc8200>.
[SSM] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/rfc/rfc4607>.
10.2. Informative References
[I-D.ietf-taps-interface]
Trammell, B., Welzl, M., Enghardt, R., Fairhurst, G.,
Kühlewind, M., Perkins, C., Tiesel, P. S., and T. Pauly,
"An Abstract Application Layer Interface to Transport
Services", Work in Progress, Internet-Draft, draft-ietf-
taps-interface-22, 6 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-taps-
interface-22>.
[IGMPsnooping]
Christensen, M., Kimball, K., and F. Solensky,
"Considerations for Internet Group Management Protocol
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(IGMP) and Multicast Listener Discovery (MLD) Snooping
Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,
<https://www.rfc-editor.org/rfc/rfc4541>.
[IGMPv3LITE]
Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790,
DOI 10.17487/RFC5790, February 2010,
<https://www.rfc-editor.org/rfc/rfc5790>.
[MLDv2] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/rfc/rfc3810>.
[RFC1045] Cheriton, D., "VMTP: Versatile Message Transaction
Protocol: Protocol specification", RFC 1045,
DOI 10.17487/RFC1045, February 1988,
<https://www.rfc-editor.org/rfc/rfc1045>.
[RFC1883] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 1883, DOI 10.17487/RFC1883,
December 1995, <https://www.rfc-editor.org/rfc/rfc1883>.
[RFC1972] Crawford, M., "A Method for the Transmission of IPv6
Packets over Ethernet Networks", RFC 1972,
DOI 10.17487/RFC1972, August 1996,
<https://www.rfc-editor.org/rfc/rfc1972>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/rfc/rfc2460>.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, DOI 10.17487/RFC3493, February 2003,
<https://www.rfc-editor.org/rfc/rfc3493>.
[RFC3678] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface
Extensions for Multicast Source Filters", RFC 3678,
DOI 10.17487/RFC3678, January 2004,
<https://www.rfc-editor.org/rfc/rfc3678>.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, DOI 10.17487/RFC3956, November 2004,
<https://www.rfc-editor.org/rfc/rfc3956>.
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[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/rfc/rfc4861>.
[RFC6085] Gundavelli, S., Townsley, M., Troan, O., and W. Dec,
"Address Mapping of IPv6 Multicast Packets on Ethernet",
RFC 6085, DOI 10.17487/RFC6085, January 2011,
<https://www.rfc-editor.org/rfc/rfc6085>.
[RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346,
DOI 10.17487/RFC7346, August 2014,
<https://www.rfc-editor.org/rfc/rfc7346>.
[RFC7371] Boucadair, M. and S. Venaas, "Updates to the IPv6
Multicast Addressing Architecture", RFC 7371,
DOI 10.17487/RFC7371, September 2014,
<https://www.rfc-editor.org/rfc/rfc7371>.
[RFC8507] Deering, S. and R. Hinden, Ed., "Simple Internet Protocol
(SIP) Specification", RFC 8507, DOI 10.17487/RFC8507,
December 2018, <https://www.rfc-editor.org/rfc/rfc8507>.
[RFC8815] Abrahamsson, M., Chown, T., Giuliano, L., and T. Eckert,
"Deprecating Any-Source Multicast (ASM) for Interdomain
Multicast", BCP 229, RFC 8815, DOI 10.17487/RFC8815,
August 2020, <https://www.rfc-editor.org/rfc/rfc8815>.
Appendix A. HOST GROUP ADDRESS ISSUES
This appendix is not part of the IP multicasting specification, but
provides background discussion of several issues related to IP host
group addresses.
A.1. Group Address Binding
The binding of IP host group addresses to physical hosts may be
considered a generalization of the binding of IP unicast addresses.
An IP unicast address is statically bound to a single local network
interface on a single IP network. An IP host group address is
dynamically bound to a set of local network interfaces on a set of IP
networks.
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It is important to understand that an IP host group address is NOT
bound to a set of IP unicast addresses. The multicast routers do not
need to maintain a list of individual members of each host group.
For example, a multicast router attached to an Ethernet need
associate only a single Ethernet multicast address with each host
group having local members, rather than a list of the members'
individual IP or Ethernet addresses.
A.2. Allocation of Transient Host Group Addresses
This memo does not specify how transient group address are allocated.
It is anticipated that different portions of the IP transient host
group address space will be allocated using different techniques.
For example, there may be a number of servers that can be contacted
to acquire a new transient group address. Some higher-level
protocols (such as VMTP, specified in [RFC1045]) may generate higher-
level transient "process group" or "entity group" addresses which are
then algorithmically mapped to a subset of the IP transient host
group addresses, similarly to the way that IP host group addresses
are mapped to Ethernet multicast addresses. A portion of the IP
group address space may be set aside for random allocation by
applications that can tolerate occasional collisions with other
multicast users, perhaps generating new addresses until a suitably
"quiet" one is found.
In general, a host cannot assume that datagrams sent to any host
group address will reach only the intended hosts, or that datagrams
received as a member of a transient host group are intended for the
recipient. Misdelivery must be detected at a level above IP, using
higher-level identifiers or authentication tokens. Information
transmitted to a host group address should be encrypted or governed
by administrative routing controls if the sender is concerned about
unwanted listeners.
Appendix B. Discussion and Explanations (TO BE REMOVED)
[RFC-editor: Please remove this section]
Please refer to Section 9 for the non-process disucssion of the goals
of this document.
B.1. Goals of this document
The goal of this document is to allow for IETF to declare [RFC1112]
historic and inherit the full INTERNET STANDARD status of [RFC1112]
with this document immediately - without going through the otherwise
necessary long process.
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The reason why [RFC1112] needs to be declared historic is so that the
IGMP version 1 protocol specified in it can be declared obsolete.
This update removes IGMPv1 text.
The reason why this document is still needed (as an Internet
Standard), is because the IP Multicast service specified in [RFC1112]
has since its inception been the Internet Standard for the IP
Multicasting service.
To allow for this document to gets immediately the intended Internet
Standard status, it introduces no functional changes and it
deliverately avoids also any unnecessary textual changes. This
includes the deliberade non-upgrade of the [RFC1112] language to use
[RFC2119] terminology. While the use of that language might be
preferred for new work/text, the success of IP Multicasting as
defined in [RFC2119] seems to indicate that the existing text was
more than sufficient.
B.2. Internet Standard status
Note that the removal of the IGMPv1 protocol may raise the question
whether the document in its current form still contains
specifications sufficient for Internet Standard as opposed to
Informational.
The core aspects that impacts interoperability (and hence qualifies
the document for Internet Standard) is the format of IP packets when
IP Multicast service is used, e.g.: IP Multicast addressing and
binding to Multicast Ethernet MAC addresses. There is no other RFC
that introduces these specifications for IP, because there was never
another update to [RFC791] to do this. [SSM], another standards
track document bilding on [RFC1112], defining the SSM service / host
stack.
This update also includes the necessary text for IPv6. Note that for
IPv6 the ethernet MAC address mapping of IPv6 multicast packets was
later (after [RFC1112]) specified in [RFC1972] and its updates, but
scattering the aspects of IPv6 multicast across (currently)
[RFC2464], {RFC4291}} and [RFC8200] makes it arguably more difficult
for implementers to understand the technology than this document that
coalesces all these services aspects - from ethernet bonding to
application interfac.
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Beyond those packet format/ethernet aspects, historically, the
Multicast service (API) related text in [RFC1112] would not have been
considered to be an Internet Standards scope definition because this
classification was not extended to (abstract) APIs, even though they
do of course define an interoperability interface between e.g.:
operating system providing the API and applications using it.
Recently, the IETF has changed its stance on this issue though and is
working on [I-D.ietf-taps-interface] with the intent for it to become
Internet Standard. With this in mind, all that text of [RFC1112] can
also be considered appropriate for Internet Standard.
B.3. Authors email
This document does include Steve Deering as the original author of
the base rfc [RFC1112] in the same way as [RFC8200] does for
[RFC2460] ([RFC8507] is also similar). The mayority of text
originates from his original RFC, hence he is the primary co-author.
He is not actively involved in editing this -bis document but is in
support of the work. Changes are edited by the co-author(s).
Being retired and not actively involved, he does not want for his
personal email address to be included in the work. Any notifications
where all authors need to provide feedback will be forwarded through
the co-author.
Whereas at the time of [RFC8200] it was possible for a co-author to
not have to include an email address, policies on Datatracker have
since changed and therefore this draft include a placeholder email
address for Steve solely to allow uploading to Datatracker.
B.4. Changelog
This document is hosted at https://github.com/toerless/rfc1112bis.
Please submit issues with this text as issues to that github and
report them on pim@ietf.org.
B.5. Open Issues
Need to revisit in more details the logic of upding RFC791. RFC1112
did not claim to be such an update even though it does effectively
update RFC791 because it exempts IP Multicast packets from RFC791
processing. And also introduces invalid packets (source address IP
Multicast which are neither unicast nor multicast).
Likewise the same would apply to RFC8200 which does not specify these
details either.
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B.5.1. draft-ietf-pim-rfc1112bis-00
Just changed title, added github pointer.
B.5.2. draft-eckert-pim-rfc1112bis-02
Changed core references from numbered style to name style .
Changed copyright clause to pre5378Trust200902, which is the same as
used for RFC8200 due to the presence of text with similar early
status.
To resolve Dinos concerns at IETF116 with -01: Added hopefully
extensive explanation wrt. to how to treat IGMPv1 based on Dino's
feedback from IETF117: This document does not ask for any removal of
IGMPv1 in any IETF specs which include it for backward compatibility
reasons, it only effectively causes it to become historic once
RFC1112 would be declared historic.
To resolve Alvaros concerns at IETF1116 with -01: Added normative
language (MUST/SHOULD). Seems as if this is quite easy given how
"must" was written appropriately in the original text. The logic of
applying MUST/MUST-NOT was based on understanding by the author how
none of the MUST would actually put existing working implementations
out of compliance.
Added explicit text to move rfc1112 to historic status.
Moved explanation of changes from rfc1112 from appendix to main text
as this seem to the common practice for document updates.
Added claim for this document to be an update to rfc791. See open
issues section though.
B.5.3. draft-eckert-pim-rfc1112bis-01
Changed all use of IPv4 back to IP. Seems standard in IETF specs.
Only IPv6 has in IETF specs the distinction of including the version.
Changed Steve Deerings address to a pseudo-email address at IETF.
See prior section.
Converted document into kramdownrfc2629 format for easier editing.
Claims that rfc2119 language is not desired/used (to maintain maximum
original text without changes).
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Rewrote section for updates to rfc1112 to hopefully better motivate/
explain the reason for this document and detail what its changes are.
B.5.4. draft-eckert-pim-rfc1112bis-00
Initial version based on [RFC1112] text version, edited.
Authors' Addresses
Stephen E. Deering
Retired
Vancouver, British Columbia
Canada
Email: deering@noreply.ietf.org
Toerless Eckert (editor)
Futurewei Technologies USA
United States of America
Email: tte@cs.fau.de
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