BIER Ingress Multicast Flow Overlay using Multicast Listener Discovery Protocols
draft-pfister-bier-mld-01
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| Authors | Pierre Pfister , IJsbrand Wijnands , Stig Venaas , Markus Stenberg | ||
| Last updated | 2016-07-07 | ||
| Replaced by | draft-ietf-bier-mld | ||
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draft-pfister-bier-mld-01
Network Working Group P. Pfister
Internet-Draft IJ. Wijnands
Intended status: Standards Track S. Venaas
Expires: January 8, 2017 Cisco Systems
M. Stenberg
July 7, 2016
BIER Ingress Multicast Flow Overlay using Multicast Listener Discovery
Protocols
draft-pfister-bier-mld-01
Abstract
This document specifies the ingress part of a multicast flow overlay
for BIER networks. Using existing multicast listener discovery
protocols, it enables multicast membership information sharing from
egress routers, acting as listeners, toward ingress routers, acting
as queriers. Ingress routers keep per-egress-router state, used to
construct the BIER bit mask associated with IP multicast packets
entering the BIER domain.
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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Drafts is at http://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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 8, 2017.
Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 4
5. Querier and Listener Specifications . . . . . . . . . . . . . 4
5.1. Configuration Parameters . . . . . . . . . . . . . . . . 4
5.2. MLDv2 instances. . . . . . . . . . . . . . . . . . . . . 5
5.2.1. Sending Queries . . . . . . . . . . . . . . . . . . . 5
5.2.2. Sending Reports . . . . . . . . . . . . . . . . . . . 6
5.2.3. Receiving Queries . . . . . . . . . . . . . . . . . . 6
5.2.4. Receiving Reports . . . . . . . . . . . . . . . . . . 6
5.3. Packet Forwarding . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The Bit Index Explicit Replication (BIER -
[I-D.ietf-bier-architecture]) forwarding technique enables IP
multicast transport across a BIER domain. When receiving or
originating a packet, ingress routers have to construct a bit mask
indicating which BIER egress routers located within the same BIER
domain will receive the packet. A stateless approach would consist
in forwarding all incoming packets toward all egress routers, which
would in turn make a forwarding decision based on local information.
But any more efficient approach would require ingress routers to keep
some state about egress routers multicast membership information,
hence requiring state sharing from egress routers toward ingress
routers.
This document specifies how to use the Multicast Listener Discovery
protocol version 2 [RFC3810] (resp. the Internet Group Management
protocol version 3 [RFC3376]) as the ingress part of a BIER multicast
flow overlay (BIER layering is described in
[I-D.ietf-bier-architecture]) for IPv6 (resp. IPv4). It enables
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multicast membership information sharing from egress routers, acting
as listeners, toward ingress routers, acting as queriers. Ingress
routers keep per-egress-router state, used to construct the BIER bit
mask associated with IP multicast packets entering the BIER domain.
This specification is applicable to both IP version 4 and version 6.
It therefore specifies two separate mechanisms operating
independently. For the sake of simplicity, the rest of this document
uses IPv6 terminology. It can be applied to IPv4 by replacing
'MLDv2' with 'IGMPv3', and following specific requirements when
explicitly stated.
2. Terminology
In this document, the key words "MAY", "MUST", "MUST NOT",
"RECOMMENDED", and "SHOULD", are to be interpreted as described in
[RFC2119].
The terms "Bit-Forwarding Router" (BFR), "Bit-Forwarding Egress
Router" (BFER), "Bit-Forwarding Ingress Router" (BFIR), "BFR-id" and
"BFR-Prefix" are to be interpreted as described in
[I-D.ietf-bier-architecture].
Additionally, the following definitions are used:
BIER Multicast Listener Discovery (BMLD): The modified version of
MLD specified in this document.
BMLD Querier: A BFR implementing the Querier part of this
specification. A BMLD Node MAY be both a Querier and a Listener.
BMLD Listener: A BFR implementing the Listener part of this
specification. A BMLD Node MAY be both a Querier and a Listener.
3. Overview
This document proposes to use the mechanisms described in MLDv2 in
order to enable multicast membership information sharing from BFERs
toward BFIRs within a given BIER domain. BMLD queries (resp.
reports) are sent over BIER toward all BMLD Nodes (resp. BMLD
Queriers) using modified MLDv2 messages which IP destination is set
to a configured 'all BMLD Nodes' (resp. 'all BMLD Queriers') IP
multicast address.
By running MLDv2 instances with per-listener explicit tracking, BMLD
Queriers are able to map BMLD Listeners with MLDv2 membership states.
This state is then used to construct the set of BFERs associated with
each incoming IP multicast data packet.
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4. Applicability Statement
BMLD runs on top of a BIER Layer and provides the ingress part of a
BIER multicast flow overlay, i.e, it specifies how BFIRs construct
the set of BFERs for each ingress IP multicast data packet. The BFER
part of the Multicast Flow Overlay is out of scope of this document.
The BIER Layer MUST be able to transport BMLD messages toward all
BMLD Queriers and Listeners. Such packets are IP multicast packets
with a BFR-Prefix as source address, a multicast destination address,
and containing a MLDv2 message.
BMLD only requires state to be kept by Queriers, and is therefore
more scalable than PIMv2 [RFC7761] in terms of overall state, but is
also likely to be less scalable than PIMv2 in terms of the amount of
control traffic and the size of the state that is kept by individual
routers.
This specification is applicable to both IP version 4 and version 6.
It therefore specifies two separate mechanisms operating
independently. For the sake of simplicity, this document uses IPv6
terminology. It can be applied to IPv4 by replacing 'MLDv2' with
'IGMPv3', and following specific requirements when explicitly stated.
5. Querier and Listener Specifications
Routers desiring to receive IP multicast traffic (e.g., for their own
use, or for forwarding) MUST behave as BMLD Listeners. Routers
receiving IP multicast traffic from outside the BIER domain, or
originating multicast traffic, MUST behave as BMLD Queriers.
BMLD Queriers (resp. BMLD Listeners) MUST act as MLDv2 Queriers
(resp. MLDv2 Listeners) as specified in [RFC3810] unless stated
otherwise in this section.
5.1. Configuration Parameters
Both Queriers and Listeners MUST operate as BFIRs and BFERs within
the BIER domain in order to send and receive BMLD messages. They
MUST therefore be configured accordingly, as specified in
[I-D.ietf-bier-architecture].
All Listeners MUST be configured with a 'all BMLD Queriers' multicast
address and the BFR-ids of all the BMLD Queriers. This is used by
Listeners to send BMLD Reports over BIER toward all Queriers.
All Queriers MUST be configured with a 'all BMLD Nodes' multicast
address and the BFR-ids of all the Queriers and Listeners. This
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information is used by Queriers to send BMLD queries over BIER toward
all BMLD Nodes.
Note that BMLD (unlike MLDv2) makes use of per-instance configured
multicast group addresses rather than well-known addresses so that
multiple instances of BMLD (using different group addresses) can be
run simultaneously within the same BIER domain. Configured group
addresses MAY be obtained from allocated IP prefixes using [RFC3306].
IP packets coming from outside of the BIER domain and having a
destination address set to the configured 'all BMLD Queriers' or the
'all BMLD Nodes' group address MUST be dropped. It is RECOMMENDED
that these configured addresses have a limited scope, enforcing this
behavior by scope-based filtering on BIER domain's egress interfaces.
5.2. MLDv2 instances.
BMLD Queriers MUST run a MLDv2 Querier instance with per-host
tracking, which means they keep track of the MLDv2 state associated
with each BMLD Listener. For that purpose, Listeners are identified
by their respective BFR-Prefix, used as IP source address in all BMLD
reports.
BMLD Listeners MUST run a MLDv2 Listener instance expressing their
interest in the multicast traffic they are supposed to receive for
local use or forwarding.
BMLD Listeners and Queriers MUST NOT run the MLDv1 (IGMPv2 and IGMPv1
for IPv4) backward compatibility procedures.
5.2.1. Sending Queries
BMLD Queries are IP packets sent over BIER by BMLD Queriers:
o Toward all BMLD Nodes (i.e., providing to the BIER Layer the BFR-
ids of all BMLD Nodes).
o Without the IPv6 router alert option [RFC2711] in the hop-by-hop
extension header [RFC2460] (or the IPv4 router alert option
[RFC2113] for IPv4).
o With the IP destination address set to the 'all BMLD Nodes' group
address.
o With the IP source address set to the BFR-Prefix of the sender.
o With a TTL value great enough such that the packet can be received
by all BMLD Nodes, depending on the underlying BIER layer (whether
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it decrements the IP TTL or not) and the size of the network. The
default value is 64.
5.2.2. Sending Reports
BMLD Reports are IP packets sent over BIER by BMLD Listeners:
o Toward all BMLD Queriers (i.e., providing to the BIER layer the
BFR-ids of all BMLD Queriers).
o Without the IPv6 router alert option [RFC2711] in the hop-by-hop
extension header [RFC2460] (or the IPv4 router alert option
[RFC2113] for IPv4).
o With the IP destination address set to the 'all BMLD Queriers'
group address.
o With the IP source address set to the BFR-Prefix of the sender.
o With a TTL value great enough such that the packet can be received
by all BMLD Queriers, depending on the underlying BIER layer
(whether it decrements the IP TTL or not) and the size of the
network. The default value is 64.
5.2.3. Receiving Queries
BMLD Queriers and Listeners MUST check the destination address of all
the IP packets that are received or forwarded over BIER whenever
their own BIER bit is set in the packet. If the destination address
is equal to the 'all BMLD Nodes' group address the packet is
processed as specified in this section.
If the IPv6 (resp. IPv4) packet contains an ICMPv6 (resp. IGMP)
message of type 'Multicast Listener Query' (resp. of type 'Membership
Query'), it is processed by the MLDv2 (resp. IGMPv3) instance run by
the BMLD Querier. It MUST be dropped otherwise.
During the MLDv2 processing, the packet MUST NOT be checked against
the MLDv2 consistency conditions (i.e., the presence of the router
alert option, the TTL equaling 1 and, for IPv6 only, the source
address being link-local).
5.2.4. Receiving Reports
BMLD Queriers MUST check the destination address of all the IP
packets that are received or forwarded over BIER whenever their own
BIER bit is set. If the destination address is equal to the 'all
BMLD Queriers' the packet is processed as specified in this section.
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If the IPv6 (resp. IPv4) packet contains an ICMPv6 (resp. IGMP)
message of type 'Multicast Listener Report Message v2' (resp.
'Version 3 Membership Report'), it is processed by the MLDv2 (resp.
IGMPv3) instance run by the BMLD Querier. It MUST be dropped
otherwise.
During the MLDv2 processing, the packet MUST NOT be checked against
the MLDv2 consistency conditions (i.e., the presence of the router
alert option, the TTL equaling 1 and, for IPv6 only, the source
address being link-local).
5.3. Packet Forwarding
BMLD Queriers configure the BIER Layer using the information obtained
using BMLD, which associates BMLD Listeners (identified by their BFR-
Prefixes) with their respective MLDv2 membership state.
More specifically, the MLDv2 state associated with each BMLD Listener
is provided to the BIER layer such that whenever a multicast packet
enters the BIER domain, if that packet matches the membership
information from a BMLD Listener, its BFR-id is added to the set of
BFR-ids the packet should be forwarded to by the BIER-Layer.
6. Security Considerations
BMLD makes use of IP MLDv2 messages transported over BIER in order to
configure the BIER Layer of BFIRs. BMLD messages MUST be secured,
either by relying on physical or link-layer security, by securing the
IP packets (e.g., using IPSec [RFC4301]), or by relying on security
features provided by the BIER Layer.
Whenever an attacker would be able to spoof the identity of a router,
it could:
o Redirect undesired traffic toward the spoofed router by
subscribing to undesired multicast traffic.
o Prevent desired multicast traffic from reaching the spoofed router
by unsubscribing to some desired multicast traffic.
7. IANA Considerations
This specification does not require any action from IANA.
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8. References
8.1. Normative References
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
DOI 10.17487/RFC2113, February 1997,
<http://www.rfc-editor.org/info/rfc2113>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
<http://www.rfc-editor.org/info/rfc3376>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<http://www.rfc-editor.org/info/rfc3810>.
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-03 (work in
progress), January 2016.
8.2. Informative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, DOI 10.17487/RFC2711, October 1999,
<http://www.rfc-editor.org/info/rfc2711>.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, DOI 10.17487/RFC3306,
August 2002, <http://www.rfc-editor.org/info/rfc3306>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>.
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[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <http://www.rfc-editor.org/info/rfc7761>.
Appendix A. Acknowledgements
Comments concerning this document are very welcome.
Authors' Addresses
Pierre Pfister
Cisco Systems
Paris
France
Email: pierre.pfister@darou.fr
IJsbrand Wijnands
Cisco Systems
De Kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Stig Venaas
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
Email: stig@cisco.com
Markus Stenberg
Helsinki 00930
Finland
Email: markus.stenberg@iki.fi
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