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 30 January 2025 Expires: 3 August 2025 Host Extensions for IP Multicasting and "Any Source Multicasting" (ASM) IP service draft-ietf-pim-rfc1112bis-03 Abstract This memo specifies the extensions required of a host implementation of the Internet Protocol (IP) to support IP multicast with the IP service interface "Any Source Multicast" (ASM). This specification applies to both versions 4 and 6 of the Internet Protocol. Distribution of this memo is unlimited. This document replaces RFC1112 for everything 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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 material or to cite them other than as "work in progress." This Internet-Draft will expire on 3 August 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Deering & Eckert Expires 3 August 2025 [Page 1] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. STATUS OF THIS MEMO . . . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5 3. LEVELS OF CONFORMANCE . . . . . . . . . . . . . . . . . . . . 6 3.1. Level 0: no support for IP multicasting. . . . . . . . . 6 3.2. Level 1: support for sending but not receiving multicast IP datagrams. . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Level 2: full support for IP multicasting. . . . . . . . 7 4. HOST GROUP ADDRESSES . . . . . . . . . . . . . . . . . . . . 7 5. MODEL OF A HOST IP IMPLEMENTATION . . . . . . . . . . . . . . 8 6. SENDING MULTICAST IP DATAGRAMS . . . . . . . . . . . . . . . 9 6.1. Extensions to the IP Service Interface . . . . . . . . . 9 6.2. Extensions to the IP Module . . . . . . . . . . . . . . . 10 6.3. Extensions to the Local Network Service Interface . . . . 11 6.4. Extensions to an Ethernet Local Network Module . . . . . 11 6.5. Extensions to Local Network Modules other than Ethernet . . . . . . . . . . . . . . . . . . . . . . . . 12 7. RECEIVING MULTICAST IP DATAGRAMS . . . . . . . . . . . . . . 12 7.1. Extensions to the IP Service Interface . . . . . . . . . 12 7.2. Extensions to the IP Module . . . . . . . . . . . . . . . 13 7.3. Extensions to the Local Network Service Interface . . . . 14 7.4. Extensions to an Ethernet Local Network Module . . . . . 15 7.5. Extensions to Local Network Modules other than Ethernet . . . . . . . . . . . . . . . . . . . . . . . . 15 8. ROUTING MULTICAST IP DATAGRAMS . . . . . . . . . . . . . . . 15 9. Status changes . . . . . . . . . . . . . . . . . . . . . . . 16 Deering & Eckert Expires 3 August 2025 [Page 2] Internet-Draft IP Multicast Host Extensions and ASM January 2025 9.1. Moving RFC1112 and IGMPv1 to historic status . . . . . . 16 9.2. Backward compatibility with IGMPv1 . . . . . . . . . . . 16 9.3. Update to RFC 791 . . . . . . . . . . . . . . . . . . . . 16 9.4. Update to STD 5 . . . . . . . . . . . . . . . . . . . . . 17 10. Changes from RFC1112 . . . . . . . . . . . . . . . . . . . . 17 10.1. Normative language . . . . . . . . . . . . . . . . . . . 17 10.2. References to IGMPv1 . . . . . . . . . . . . . . . . . . 17 10.3. New summary . . . . . . . . . . . . . . . . . . . . . . 17 10.4. Any-Source Multicast (ASM) . . . . . . . . . . . . . . . 17 10.5. SSM . . . . . . . . . . . . . . . . . . . . . . . . . . 17 10.6. Applicability to both IPv4 and IPv6 . . . . . . . . . . 18 10.7. IPv4 Local Network Control Block . . . . . . . . . . . . 18 10.8. Special treatment of 224.0.0.1 and FF02::1 . . . . . . . 19 10.9. IGMP/MLD messages for Link-Local IPv4 host group addresses . . . . . . . . . . . . . . . . . . . . . . . 19 10.10. Standard for IP multicasting in controlled networks . . 20 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 11.1. Protocol Numbers registry . . . . . . . . . . . . . . . 20 11.2. Internet Group Management Protocol (IGMP) Type Numbers Registry . . . . . . . . . . . . . . . . . . . . . . . . 20 11.3. Multicast 48-bit MAC Addresses registry . . . . . . . . 21 11.4. IPv4 Address range registries . . . . . . . . . . . . . 21 11.5. IPv4 Multicast Address Space registry . . . . . . . . . 21 11.6. IP Flow Information Export registry . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 12.1. Normative References . . . . . . . . . . . . . . . . . . 21 12.2. Informative References . . . . . . . . . . . . . . . . . 23 Appendix A. HOST GROUP ADDRESS ISSUES . . . . . . . . . . . . . 25 A.1. Group Address Binding . . . . . . . . . . . . . . . . . . 25 A.2. Allocation of Transient Host Group Addresses . . . . . . 26 A.3. Link-local IP multicast and IGMP/MLD . . . . . . . . . . 26 Appendix B. Discussion and Explanations (TO BE REMOVED) . . . . 28 B.1. RFC-Editor notes . . . . . . . . . . . . . . . . . . . . 28 B.2. Goals and evolution of this document . . . . . . . . . . 28 B.3. Update to RFC791 . . . . . . . . . . . . . . . . . . . . 29 B.4. Changelog . . . . . . . . . . . . . . . . . . . . . . . . 30 B.4.1. draft-ietf-pim-rfc1112bis-03 . . . . . . . . . . . . 30 B.4.2. draft-ietf-pim-rfc1112bis-02 . . . . . . . . . . . . 31 B.4.3. draft-ietf-pim-rfc1112bis-01 . . . . . . . . . . . . 31 B.4.4. draft-eckert-pim-rfc1112bis-02 . . . . . . . . . . . 32 B.4.5. draft-ietf-pim-rfc1112bis-00 . . . . . . . . . . . . 32 B.4.6. draft-eckert-pim-rfc1112bis-01 . . . . . . . . . . . 32 B.4.7. draft-eckert-pim-rfc1112bis-00 . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 Deering & Eckert Expires 3 August 2025 [Page 3] Internet-Draft IP Multicast Host Extensions and ASM January 2025 1. STATUS OF THIS MEMO This memo specifies the extensions required of a host implementation of the Internet Protocol (IP) to support IP multicast with the IP service interface "Any Source Multicast" (ASM). This specification applies to both versions 4 and 6 of the Internet Protocol. Distribution of this memo is unlimited. This document replaces RFC1112 for everything except for 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 2.1. Summary This memo specifies the extensions required of a host implementation of the Internet Protocol (IP) to support IP multicast. It replaces [RFC791] for everything except for the specification of the protocol IGMP version 1 in Appendix I. of RFC1112. This document declares RFC1112 including IGMP version 1 historic. RFC1112 specified IP multicast for version 4 of the IP protocol (IPv4, [RFC791]), and refers to that version as IP. This document applies both to version 4 of the IP protocol and version 6 of the IP protocol (IPv6, [RFC8200]). The term IP is used in this document to refer to both versions. Where specifications in support of IP multicast for version 6 of the IP protocol where already provided by other RFCs, this document provides references to those pre-existing specifications, so that this document can serve as a complete single point of reference for the host extensions for IP multicast with either versions of IP. "Source Specific Multicast", (SSM, [SSM]) introduced a complementary extension to the IP service from the one specified here. It is relying on components specified here, such as {#ethernet}, and extending or superseding others. The service specified here is called "Any Source Multicast" (ASM) to distinguish it explicitly from SSM. This document also describes, where SSM changes specifications from RFC1112. Deering & Eckert Expires 3 August 2025 [Page 4] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Due to the existence of both ASM and SSM, the term "IP multicast" best refers to the complete set of IP host extensions in support of either service options: this specification for ASM plus [SSM]). When the term IP multicast is used to refer to the IP multicast service without further qualification, then ASM is to be implied. This specification aims to maintain all the original text of RFC1112 where technically appropriate. This incurs the use of some historic language, such as "(internet) gateway" to refer to IP routers, and capitalization of chapter headings. See Section 9 and Section 10 for a detailed list of changes from RFC1112. 2.2. Overview 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. Deering & Eckert Expires 3 August 2025 [Page 5] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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 IPv4 time-to-live or IPv6 hop limit 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 IPv4 time-to-live or IPv6 hop limit, 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 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 in support of multicasting with IPv4 are described in section 4 of this memo, IPv6 addresses for IP multicasting are described in [RFC4291] and [RFC7371]. Deering & Eckert Expires 3 August 2025 [Page 6] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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 IPv4 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 for full Level 2 support of IP multicasting are [IGMPv3] and [MLDv2] or lightweight versions of either protocol [IGMPv3lite]. All of the following sections of this memo are applicable to level 2 implementations. 4. HOST GROUP ADDRESSES IPv4 Host groups are identified by class D IPv4 addresses, i.e., those with "1110" as their high-order four bits. Class E IPv4 addresses, i.e., those with "1111" as their high-order four bits, are reserved for future addressing modes. Deering & Eckert Expires 3 August 2025 [Page 7] Internet-Draft IP Multicast Host Extensions and ASM January 2025 In Internet standard "dotted decimal" notation, IPv4 host group addresses range from 224.0.0.0 to 239.255.255.255. IPv4 host group addresses in the "Local Network Control Block", 224.0.0.0 - 224.0.0.255 are called Link-Local IPv4 host group addresses. IP datagrams with a Link-Local destination address are called Link-Local multicast packets. The IPv4 Link-Local addresses 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 IPv4 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. Allocation guidelines for Link- Local addresses are specified in [RFC5771]. The addresses of well-known, permanent groups are to be published in "Assigned Numbers", see [RFC3232], currently through the IANA "IPv4 Multicast Address Space Registry". [RFC5771] and [RFC6034] refine more detailed allocation and uses of different sub-blocks of 224.0.0.0/4. The IPv6 all-hosts group address is FF02::1, IPv6 Host groups are identified by IPv6 addresses as defined in [RFC4291] section 2.7 and updated by [RFC7346], [RFC7371]. The addresses of other groups are currently published via the IANA "IPv6 Multicast Address Space Registry". IP addresses as specified in [SSM] are not used for ASM IP multicast and are not considered IP host groups by [SSM]. 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. Deering & Eckert Expires 3 August 2025 [Page 8] Internet-Draft IP Multicast Host Extensions and ASM January 2025 | | | Upper-Layer Protocol Modules | |__________________________________________________________| --------------------- IP Service Interface ----------------------- __________________________________________________________ | | | | | | IPv4: | IPv6: | | | ICMP+IGMP | ICMPv6+MLD | | IP [IPv4 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 IPv4 time-to-live or IPv6 hop limit of an outgoing multicast datagram, if such a capability does not already Deering & Eckert Expires 3 August 2025 [Page 9] Internet-Draft IP Multicast Host Extensions and ASM January 2025 exist. If the upper-layer protocol chooses not to specify a time-to- live/hop limit, 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 ) Deering & Eckert Expires 3 August 2025 [Page 10] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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 or IP address from an SSM range 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 IPv4 host group address is mapped to an Ethernet multicast address by placing the low-order 23-bits of the IPv4 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 IPv4 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]. The address mappings for IP addresses do apply not only to IP host group addresses, but also to destination IP addresses used for SSM. Deering & Eckert Expires 3 August 2025 [Page 11] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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 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. Deering & Eckert Expires 3 August 2025 [Page 12] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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. IPv6 socket extensions supporting these functions are defined in [RFC3493], section 5.2. [RFC3678] specifies socket options for these functions for ASM and also includes socket options in support of SSM. Note that these are UDP socket extensions but not IP socket extensions due to the absence of widely adopted/required IP 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 MUST be 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 IPv4 time-to-live of 1 or IPv6 Hop Limit of 1. This field MUST 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 or SSM range destination IP address. Deering & Eckert Expires 3 August 2025 [Page 13] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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). When supporting Level 2, the IP module MUST also be extended to implement the IGMP protocol for IPv4 and the MLD protocol for IPv6 depending on the version(s) 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. See Section 10.8 for potentially special treatment of the all-hosts groups in IGMP/ MLD. Hosts and gateways MAY omit the sending of IGMP messages to report membership for Link-Local IPv4 host group addresses, especially on networks known not to (be able to) use any form of IGMP snooping. This does also apply for the IPv6 Link-Local host group all-hosts FF02::1, but not to other Link-Local IPv6 host groups. See Appendix A.3. 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. Deering & Eckert Expires 3 August 2025 [Page 14] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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. 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. ROUTING MULTICAST IP DATAGRAMS IPv4 datagrams with a Link-Local destination address MUST never be forwarded to a different link by multicast routers, regardless of their time-to-live. See Section 10.7 for explanations. The equivalent requirement are specified for IPv6 in [RFC4291], section 2.5.6. Deering & Eckert Expires 3 August 2025 [Page 15] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Rules for forwarding of non Link-Local IP multicast packets are outside the scope of this document. 9. Status changes 9.1. Moving RFC1112 and IGMPv1 to historic status This document moves RFC1112 to historic status which also moves the IGMP version 1 protocol as specified in Appendix 1 of RFC1112 to historic status, as it is not included into this document anymore. All other aspects of RFC1112 beside IGMPv1 are kept and updated by this document and maintain their current Internet Standard designation from RFC1112 through the normative status of this document. 9.2. Backward compatibility with IGMPv1 Current or future versions of IGMP or other protocols/mechanisms including but not necessary limited to [IGMPv2], [IGMPv3] or [IGMPv3lite] do or may include backward compatibility with IGMPv1, such as in [IGMPsnooping], which requires them to refer to 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 that wants to maintain such backward compatibility with IGMPv1 need to continue to reference RFC1112 as the specification of IGMPv1. Any future reference for new or updated work to any other definition from RFC1112 (host extensions for IP multicast and/or Any Source Multicast service) need to refer to this document instead of RFC1112. 9.3. Update to RFC 791 This document is an update to [RFC791] because none of the core procedures to send and receive IP multicast packets described in this document match those defined for IP unicast packets in [RFC791]. Instead, IP multicast is carving out parts of the IP address space to trigger completely new forwarding for completely new entities: host groups in ASM, channels in SSM). See Appendix B.3 for further discussions. Deering & Eckert Expires 3 August 2025 [Page 16] Internet-Draft IP Multicast Host Extensions and ASM January 2025 9.4. Update to STD 5 This document replaces RFC1112 in [STD5] which defines IPv4 ([RFC791]) including its core extensions. Note: As there is no precedent for STD86 (IPv6) to include any specifications for extension of IPv6, this document is not asked to become part of STD86. 10. Changes from RFC1112 Beyond the status changes described in Section 9, this document introduces the following changes over RFC1112. All requirements changes are intended to make this specification aligned with long-term, most widely implemented, deployed and standardised RFCs for IP multicast, so that this document does not create the need to change existing implementations or deployments, as could be the case if RFC1112 (without IGMPv1) was to be implemented today. 10.1. Normative language This document introduces the use of normative language through capitalization. RFC1112 preceded [RFC2119] and hence did not include this language. 10.2. References to IGMPv1 References to IGMPv1 in RFC1112 are replaced with references to [IGMPv3] in this text. 10.3. New summary The new Section 2.1 summarizes the scope of this document and the core new changes over RFC1112. 10.4. Any-Source Multicast (ASM) This update introduces the term "ASM IP multicast" (ASM) as a new term for the IP service interface specified in this document (and previously in RFC1112) as explained in Section 2.1. 10.5. SSM Section 2.1 explains the relationship of this document to SSM ([SSM]). Deering & Eckert Expires 3 August 2025 [Page 17] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Section 4 adds the specification that the term host groups specified in this document does not apply to destination addresses used for SSM. No functional changes to the IP multicast service are incurred by these changes, except that it acknowledges the existence of SSM which reduces the range of host group addresses used for ASM. 10.6. Applicability to both IPv4 and IPv6 This document is written to apply to both IPv4 and IPv6 by adding detail for IPv6 where RFC1112 only covered IPv4. This includes addressing and protocols in support of the service - Multicast Listener Discovery [MLDv2] for IPv6 versus IGMP for IPv4. IPv6 documents such as [RFC1883] and all its updates (e.g.: [RFC8200]) are defining the necessary wire encoding aspects of IP multicast in the assumption of the service of RFC1112 for IPv6, but without being able to refer to RFC1112, as it was only defined for IPv4. Future documents can refer to this document as the IP multicast / ASM service for both IPv4 and IPv6. 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 changes. 10.7. IPv4 Local Network Control Block RFC1112 defines the requirement for IPv4 datagrams to the all-hosts group 224.0.0.1 to never be forwarded beyond a single network. In later RFCs, this behavior became the BCP for the whole IPv4 Local Network Control Block 224.0.0.0 - 224.0.0.255, making it the Link- Local host group address block for IPv4 multicast. [RFC2365] and [RFC5771], section 4 are the BCPs covering this requirement. This document formalizes this BCP behavior as a standard requirement in Section 8, superseding and encompassing the more specific requirement for just 224.0.0.1 from RFC1112, and mirroring the same standardized behavior for IPv6 Link-Local addresses. Because this is actually a requirement against IP multicast routers and not hosts, this is now also accordingly described in a separate section. This requirement does not incur changes over how IP multicast is implemented or deployed. Deering & Eckert Expires 3 August 2025 [Page 18] Internet-Draft IP Multicast Host Extensions and ASM January 2025 10.8. Special treatment of 224.0.0.1 and FF02::1 RFC1112, section 7.2 introduced the requirements for hosts to permanently join 224.0.0.1. Its explains this requirement to be in support of IGMP (version 1). Likewise, [IGMPv2], section 6. and [IGMPv3], section 5. repeat this requirement, and [MLDv1], section 6. and [MLDv2] section 6. also define the same requirement for the IPv6 all-hosts address FF02::1. Because this requirement is considered part of IGMP/MLD, and because this document does not anymore specify any form of IGMP, it does not repeat this requirement from RFC1112. Instead, this requirement now solely relies on IGMP/MLD specifications to define it. These text changes do therefore not incur any requirements changes for implementations of these existing versions of IGMP/MLD, By leaving out this requirement from the document, future versions of IGMP/MLD are also free to choose whether to carry on this method without having to update this document. Note that [IGMPv3lite] omits this requirement. 10.9. IGMP/MLD messages for Link-Local IPv4 host group addresses RFC1112, Appendix I. (IGMPv1), [IGMPv2], [IGMPv3], [MLDv1], [MLDv2] require hosts to not send IGMP/MLD messages for the all-hosts group. This would be in conflict of the general rules of RFC1112 (outside of its IGMPv1 specific definitions) and equally this specification if it was not enhanced. This specification therefore contains new text that makes it compatible with existing IGMP/MLD specification, and with long tern established and deployed implementation practices. New text in Appendix A.3 explains how after RFC1112, it became a common place implementation choice to not send IGMP messages for any IPv4 Link-Local host group address, and explains how this was done with good technical reason at the time. This behavior is so common, that [IGMPsnooping] mandates to explicit support it IGMP snooping implementations. Referring to that explanation, a new MAY requirement in Section 7.2 allowing (but not recommending) this behavior makes existing specifications and deployments compatible with this documents specifications. It is only a MAY even though it is common in IPv4, because the experience with IPv6 shows that it does work (of course) equally well if this is not done, and can then support better MLD snooping than IGMP snooping. Deering & Eckert Expires 3 August 2025 [Page 19] Internet-Draft IP Multicast Host Extensions and ASM January 2025 10.10. 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 preferable. However, these limitations to the applicability of ASM do not impact the applicability of any parts of the host stack described in this document for other IP multicast service interfaces, 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. 11. IANA Considerations 11.1. Protocol Numbers registry IANA is asked to replace the Reference field for the IGMP protocol in the Protocol Numbers registry (https://www.iana.org/assignments/ protocol-numbers/protocol-numbers.xhtml) from RFC1112 to [THIS-RFC]. Explanation: This protocol number is used by all versions of IGMP, including [IGMPv2] and [IGMPv3] and is unaffected by making IGMP version 1 historic. 11.2. Internet Group Management Protocol (IGMP) Type Numbers Registry IANA is asked to replace the Reference to RFC1112 for the 0x11 / "IGMP Membership Query" entry in the "Internet Group Management Protocol (IGMP) Type Numbers Registry" (https://www.iana.org/assignments/igmp-type-numbers/igmp-type- numbers.xhtml) with "RFC1112, [RFC2236], [RFC3376]". Deering & Eckert Expires 3 August 2025 [Page 20] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Explanation: This type code messages where introduced by RFC1112 but modified versions thereof where also introduced by [RFC2236] and [RFC3376], so that it is clearer if all three RFCs are indicated. All other references to RFC1112 in this registry are specifically referring to that RFC in it's role of defining IGMP version 1 and thus need to continue to refer to RFC1112 and not [THIS-RFC. 11.3. Multicast 48-bit MAC Addresses registry IANA is asked to replace the Reference field for the IPv4 Multicast range entry in the "IANA Multicast 48-bit MAC Addresses" (https://www.iana.org/assignments/ethernet-numbers) from RFC1112 to [THIS-RFC]. 11.4. IPv4 Address range registries IANA is asked to replace the Reference field for the 240.0.0.0/4 entry in the "IANA IPv4 Special-Purpose Address Registry" (https://www.iana.org/assignments/iana-ipv4-special-registry/iana- ipv4-special-registry.xhtml) from RFC1112 to [THIS-RFC]. The Section 4 text stays unchanged. IANA is asked to replace the Reference to RFC1112 in the "IANA IPv4 Address Space Registry" (https://www.iana.org/assignments/ipv4- address-space/ipv4-address-space.xhtml) with [THIS-RFC]. 11.5. IPv4 Multicast Address Space registry IANA is asked to replace the three references to RFC1112 in the "IPv4 Multicast Address Space Registry" (https://www.iana.org/assignments/ multicast-addresses/multicast-addresses.xhtml) with [THIS-RFC]. 11.6. IP Flow Information Export registry IANA is asked to replace the two references to RFC1112 in the "IPFIX Information Elements" registry (https://www.iana.org/assignments/ipfix/ipfix.xhtml) with [THIS-RFC]. 12. References 12.1. Normative References [IGMPv2] Fenner, W., "Internet Group Management Protocol, Version 2", RFC 2236, DOI 10.17487/RFC2236, November 1997, . Deering & Eckert Expires 3 August 2025 [Page 21] Internet-Draft IP Multicast Host Extensions and ASM January 2025 [IGMPv3] Haberman, B., "Internet Group Management Protocol, Version 3", Work in Progress, Internet-Draft, draft-ietf-pim- 3376bis-12, 27 August 2024, . [MLDv2] Haberman, B., "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", Work in Progress, Internet-Draft, draft-ietf-pim-3810bis-12, 27 August 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [SSM] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, . [STD5] Internet Standard 5, . At the time of writing, this STD comprises the following: Deering & Eckert Expires 3 August 2025 [Page 22] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, September 1981, . Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC 919, DOI 10.17487/RFC0919, October 1984, . Mogul, J., "Broadcasting Internet datagrams in the presence of subnets", STD 5, RFC 922, DOI 10.17487/RFC0922, October 1984, . Mogul, J. and J. Postel, "Internet Standard Subnetting Procedure", STD 5, RFC 950, DOI 10.17487/RFC0950, August 1985, . Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, DOI 10.17487/RFC1112, August 1989, . 12.2. Informative References [IGMPsnooping] Christensen, M., Kimball, K., and F. Solensky, "Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, . [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, . [MLDv1] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, DOI 10.17487/RFC2710, October 1999, . Deering & Eckert Expires 3 August 2025 [Page 23] Internet-Draft IP Multicast Host Extensions and ASM January 2025 [RFC1045] Cheriton, D., "VMTP: Versatile Message Transaction Protocol: Protocol specification", RFC 1045, DOI 10.17487/RFC1045, February 1988, . [RFC1723] Malkin, G., "RIP Version 2 - Carrying Additional Information", RFC 1723, DOI 10.17487/RFC1723, November 1994, . [RFC1883] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 1883, DOI 10.17487/RFC1883, December 1995, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . [RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC 2365, DOI 10.17487/RFC2365, July 1998, . [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, January 2002, . [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, . [RFC3678] Thaler, D., Fenner, B., and B. Quinn, "Socket Interface Extensions for Multicast Source Filters", RFC 3678, DOI 10.17487/RFC3678, January 2004, . [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, . [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, . Deering & Eckert Expires 3 August 2025 [Page 24] Internet-Draft IP Multicast Host Extensions and ASM January 2025 [RFC5771] Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for IPv4 Multicast Address Assignments", BCP 51, RFC 5771, DOI 10.17487/RFC5771, March 2010, . [RFC6034] Thaler, D., "Unicast-Prefix-Based IPv4 Multicast Addresses", RFC 6034, DOI 10.17487/RFC6034, October 2010, . [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, . [RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346, DOI 10.17487/RFC7346, August 2014, . [RFC7371] Boucadair, M. and S. Venaas, "Updates to the IPv6 Multicast Addressing Architecture", RFC 7371, DOI 10.17487/RFC7371, September 2014, . [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, . 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. Deering & Eckert Expires 3 August 2025 [Page 25] Internet-Draft IP Multicast Host Extensions and ASM January 2025 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. A.3. Link-local IP multicast and IGMP/MLD On networks, where IP multicast packets are broadcast, such as (non- switched) ethernet, IP multicast packets will reach all level 2 IP multicast receivers without the need to use IGMP or MLD. This signaling is only necessary for IP multicast receivers when the sender is in a different LAN so that IP multicast routers can forward the IP multicast traffic from the sender network to the receiver network. IP multicast packet to a Link-Local IP multicast destination address do therefore technically never need any IGMP or MLD signaling on such (non-switched broadcast) networks, because they are never forwarded between networks (Section 8). Deering & Eckert Expires 3 August 2025 [Page 26] Internet-Draft IP Multicast Host Extensions and ASM January 2025 During the early years of IPv4 multicast, this understanding resulted in implementations for protocols that receive Link-Local IPv4 multicast packet without implementing IGMP. Examples of such protocols include RIPv2 ([RFC1723]) or OSPF ([RFC2328]) and several other protocols, often running on IPv4 routers which had no IPv4 multicast routing implementation at the time and no IPv4 multicast applications for which they needed to be IPv4 multicast receiver for non Link-Local IPv4 multicast addresses. When these implementations later received implementations of level 2 IPv4 multicast support, those implementations excluded Link-Local host groups, so that those protocols would continue to run without IGMP as they had in before. Contributing to these implementation choices was also the fact that IGMP in the versions specified so far does not allow to keep track of ongoing receiver membership status in the absence of an IGMP router side implementation, called an IGMP querier. With the target (Link- Local IPv4 multicast only) protocols being deployed in the absence of any such IGMP querier, the use of IGMP could also serve arguably no purpose except for compliance with RFC1112. This situation changed towards the end of the 1990th with the introduction of ethernet switches that snoop IGMP messages to constrain forwarding of IPv4 multicast packets for a particular IPv4 multicast group to only those ports with hosts joined to the group. This behavior was later documented in [IGMPsnooping] but was widely deployed even earlier due to the co-existence of ports with the different speeds 10Mbps, 100Mbps and 1Gbps, and the resulting need to protect the slower speed ports from potentially large rates of IPv4 multicast traffic between faster hosts. In result, IGMP snooping switches had to flood traffic to Link-Local IPv4 multicast groups due to the common absence of IGMP support for them, and this is accordingly also recommended by [IGMPsnooping]. Due to this long-term practice, this document is thus permitting this non-use of IGMP for Link-Local host groups by introducing a MAY for it in Section 7.2. Note that IP multicast routers do not and can not typically report IP multicast groups via IGMP or MLD, because they are not joined to them as an IP multicast host, but simply need to receive them as an IP multicast router to forward them. Even when an IP multicast router is joined to specific IP multicast group as an IP multicast host, reporting them via IGMP may sound futile because as an IP multicast router it would still need to receive the IP multicast traffic in the absence of such IGMP reporting, because it might need to forward it. Deering & Eckert Expires 3 August 2025 [Page 27] Internet-Draft IP Multicast Host Extensions and ASM January 2025 However, this logic does not apply to Link-Local groups, because they are never forwarded and could thus be filtered by IGMP or MLD snooping switches if those switches could trust routers to report them correctly. Which they can not do for IPv4 due to its history. In recognition of this situation, [MLDv1] for IPv6 did emphasize the need to report also Link-Local IPv6 group memberships to avoid these issues. Therefore this document also has no equivalent MAY statement for IPv6. Note that IGMP/MLD reporting for non Link-Local IP multicast groups from an IP multicast router joining it as a host is also not just a superficial specification requirement because of the assumption that routers need to receive all non Link-Local IP multicast packets. Switches that do support snooping of IP multicast routing protocols such as PIM may also be able to determine which traffic needs to be forwarded to an IP multicast router but those can may not include the groups that the IP multicast router has only joined to only as a host and is not reporting via IGMP/MLD. Appendix B. Discussion and Explanations (TO BE REMOVED) [RFC-editor: Please remove this Appendix after observing the following section addressed to you] Please refer to Section 10 for the non-process discussion of the goals of this document. B.1. RFC-Editor notes The kramdown tooling did not allow to have references for both STD5 and RFC1112, those fail because the STD5 reference creates an "RFC1112" anchor. Thus there is no separate reference for RFC1112 in this version of the document. This needs to be fixed in XML by adding a full reference to RFC1112 and removing the RFC1112 anchor from the STD5 reference. B.2. Goals and evolution of this document The initial goal of this document was to allow for IETF to declare the IGMPv1 protocol historic which today is a Full Internet Standard due to it being defined in RFC1112. This should be achieved without changing the Full Internet Standard status of the IP Host Extensions for IP Multicast and ASM IP Service interface specified in RFC1112 because those specification are as fundamental to the definition of IP multicast as RFC791 is for IP (unicast). Deering & Eckert Expires 3 August 2025 [Page 28] Internet-Draft IP Multicast Host Extensions and ASM January 2025 The best way to achieve this seemed to be an update to RFC1112 which removes all of IGMPv1, but maintains the rest of the document. None of these removal of IGMPv1 changes changed the applicability or requirements to existing IP multicast (plus its protocols) implementations or other specifications. The next refinement was to rectify the situation that there is no specification explaining the same details as RFC1112 for IPv6 multicast even though RFC8200 (full internet standard) even explicitly includes IPv6 multicast, and a range of other RFC define necessary code-points (such as for ethernet mapping) for IPv6 multicast. Most of the text of this specification can hence can simply talk about "IP" which in this specification implies both IPv4 and IPv6, and only in places where IPv6 differs, does the document now include new explicit text, most often pointing to pre-existing RFCs specifying the necessary details for IPv6. Again, none of these changes impact other specs or deployments. The third step of refinement was add the necessary verbiage to explain the differences between SSM and the specifications in this document. None of these text enhancements incur any functional changes of long-term established practices. Instead, they are only resulting in references to SSM RFCs, introduction of the term ASM (which was previously only defined in SSM RFCs), and the limitation of applicability of terms in this document (such as host group) to their use with ASM. The last round of changes added and refined details to be in-line with long-term established practices and removing any possible contradictions between the original RFC1112 text and newer standards track specification such as IGMPv2/MLDv3 or long term established implementation practices. This includes the limitation of scope of ASM to controlled networks and the definition of the IPv4 Link-Local address range, which so far had only been defined through BCP RFC, unlike in IPv6, where it's part of the architecture, as well as permitting (but not recommending) non-use of IGMP for them. In summary, all changes in the document will make this document a replacement of rfc1112 which much more reflects the full internet standard nature of the technology than rfc1112 did as of recent. B.3. Update to RFC791 This version of the text proposes that this spec is declared to be an update to RFC791. Deering & Eckert Expires 3 August 2025 [Page 29] Internet-Draft IP Multicast Host Extensions and ASM January 2025 The argument made in Section 9.3 to support this classification may not be persuasive enough (because the according rfc791 text may be read as a perfectly good extension point specification), in which case the update status and related text should be deleted. However, If anyone where to come up with a re-use of 224.0.0.0/4 for any non-IP multicast purposes, havoc might ensure with devices that do assume IP multicast semantics, so it may simply be prudent to include this declaration. It would also make the relationship between IPv4 and IPv4 multicast be more aligned with IPv6, where IPv6 multicast is included in RFC8200. 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.4.1. draft-ietf-pim-rfc1112bis-03 1. Changed document text to make the term "ASM" apply only to the IP service interface (extensions) specified by the document (and shown and explained in existing text), instead of the whole host extensions specified in this document (as it was written up to up to -02). This is the only correct semantic, given how all the host exensions specified in this document are shared by SSM, only the IP service interface is changed/amended by SSM. 2. Subdivided section 2 (INTRODUCTION) into sections 2.1 (Summary), which contains new text from this spec, and 2.2 (Overview), which is unchanged RFC1112 text. Newly written section 2.1 to summarize the key content of this document. This was so far only explained in the much later changes from rfc1112 section. Includes IPv4/IPv6 applicability, ASM/SSM naming and maintaining most of RFC1112 text as a goal. 3. Introduced text to define and explain link local IPv4 host group addresses 224.0.0.0 - 224.0.0.255. This was triggered by trying to fix the rfc1112 text sections that Brian Haberman was concerned about, which did cover behavior for 224.0.0.1. As it turns out, the behavior for 224.0.0.1 was quickly adopted by other protocols getting 224.0.0.0/24 addresses and there has been no functional specification to explain the non-forwarding behavior for these link-local addresses. Instead, only IANA allocation guideline RFCs where introducing them. This is now rectified with new explanatory text in this spec. and a new MAY requirement to permit non-use of IGMP for those groups. See Section 7.2. Deering & Eckert Expires 3 August 2025 [Page 30] Internet-Draft IP Multicast Host Extensions and ASM January 2025 1. Changed references to IGMPv3 and MLDv2 to the -bis drafts currently in RFC-editor queue. Also triggered by Brian Haberman mentioning them. 2. Improved wording in "(Normative) Status Change" section 9. 5.1 Removed "Update to rfc791" as an open issue and instead claimed it as fact in section 9.3. Added discussion about this point to the discussion appendix that is to be removed by RFC-editor. 5.1 Also added subsection to declare that this document replaces RFC1112 in STD5. 1. Enhanced/New text in section 10., "changes from RFC1112" Especially explaining the changes in the normative section explained above and below, triggered by Brian's review. 1. Applying changes proposed by Brian Haberman during WGLC. 7.1 Changed meaning of IP from "IPv4" to "IPv4 and IPv6", accordingly updated all text. Makes a lot of sense given the goal of showing how most of the IP multicast host stack operates the same for IPv4 and IPv6. 7.2 Re-added requirement for routers not to forward link-local multicast 7.3 adding MAY requirement to allow non-signaling of Link-Local scope IPv4 multicast and IPv6 all-hosts group, and explanations how this is better than the prior definitions from rfc1112. Also includes new (length) Appendix A.3 to justify this for IPv4. 7.4 text nits (thanks, Brian). B.4.2. draft-ietf-pim-rfc1112bis-02 Removed unused references, fefresh - waiting for more reviews. Added IANA section for updates from RFC1112 to RFC1112bis. Added references to RFC5771 and RFC6034 because they actually are the references for the IANA 224.0.0.0/4 registrations, which seems a bit undocumented given how RFC1112 did introduce the definition (before IANA). B.4.3. draft-ietf-pim-rfc1112bis-01 Fix up reference for IGMPv3. Refined candidate open issues. Removed author discussion. Deering & Eckert Expires 3 August 2025 [Page 31] Internet-Draft IP Multicast Host Extensions and ASM January 2025 B.4.4. 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 Dino's 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.4.5. draft-ietf-pim-rfc1112bis-00 Just changed title, added github pointer. B.4.6. 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). Deering & Eckert Expires 3 August 2025 [Page 32] Internet-Draft IP Multicast Host Extensions and ASM January 2025 Rewrote section for updates to rfc1112 to hopefully better motivate/ explain the reason for this document and detail what its changes are. B.4.7. 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 Deering & Eckert Expires 3 August 2025 [Page 33]