Internet DRAFT - draft-hb-pim-light
draft-hb-pim-light
Network Working Group H. Bidgoli, Ed.
Internet-Draft Nokia
Intended status: Standards Track S. Venaas
Expires: 3 March 2023 Cisco System, Inc.
M. Mishra
Cisco System
Z. Zhang
Juniper Networks
M. McBride
Futurewei Technologies Inc.
30 August 2022
PIM Light
draft-hb-pim-light-03
Abstract
This document specifies a new Protocol Independent Multicast
interface which does not need PIM Hello to accept PIM Join/Prunes or
PIM Asserts.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 3 March 2023.
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Copyright (c) 2022 IETF Trust and the persons identified as the
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. PIM Light Interface . . . . . . . . . . . . . . . . . . . . . 3
3.1. PLI supported Messages . . . . . . . . . . . . . . . . . 3
3.1.1. PIM Sparse Mode . . . . . . . . . . . . . . . . . . . 4
3.2. Lack of Hello Message considration . . . . . . . . . . . 4
3.2.1. Join Attribute . . . . . . . . . . . . . . . . . . . 4
3.2.2. DR Selection . . . . . . . . . . . . . . . . . . . . 4
3.3. PLI Configuration . . . . . . . . . . . . . . . . . . . . 5
3.4. Failures in PLR domain . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
It might be desirable to create a PIM interface between routers where
only PIM Join/Prunes packets are triggered over it without having a
full PIM neighbor discovery. As an example, this type of PIM
interface can be useful in some scenarios where the multicast state
needs to be signaled over a network or medium which is not capable of
or has no need for creating full PIM neighborship between its Peer
Routers. These type of PIM interfaces are called PIM Light
Interfaces (PLI).
2. Conventions used in this document
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.
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2.1. Definitions
This draft uses definitions used in [RFC7761]
3. PIM Light Interface
RFC [RFC7761] section 4.3.1 describes the PIM neighbor discovery via
Hello messages. It also describes that PIM Join/Prune are not
accepted from a router unless a Hello message has been heard from
that router.
In some scenarios it is desirable to communicate and build multicast
states between two directly or non directly attach routers without
establishing a PIM neighborship. There could be many reasons for
this desired, but one example is the desired to signal multicast
states upstream, between two or more PIM Domains via a network or
medium that is not optimized for PIM or does not require PIM Neighbor
establishment. An example is a BIER network connecting multiple PIM
domains. In these BIER networks PIM Join/prune messages are tunneled
via bier as per [draft-ietf-bier-pim-signaling].
A PIM Light Interface (PLI) ONLY accepts Join/Prune messages from an
unknown PIM router and it accepts these messages it without receiving
a PIM Hello message form the router. Lack of Hello Messages on a PLI
means there is no mechanism to learn about the neighboring PIM
routers on each interface and their capabilities or run some of the
basic algorithms like DR Priority between the routers. As such the
router doesn't create any General-Purpose state for neighboring PIM
and it only accepts and installs each Join message from upstream
routers in its multicast routing table.
Because of this, a PLI needs to be created in very especial cases and
the application that is using these PLIs should ensure there is no
multicast duplication of packets. As an example, multiple upstream
routers sending the same multicast stream to a single downstream
router.
3.1. PLI supported Messages
As per IANA [iana_pim-parameters] pim currently supports 12 message
types, PIM Light only supports message type 3 (Join/Prune). All
other message types are not supported for PIM Light and should not be
process if recived on a PLR interface.
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3.1.1. PIM Sparse Mode
Lack of register message on PLR means that, the Source, DR, RP all
need to be in a common PIM domain and can not be connected over PLR.
PLR will only processes join/prune regardless of if the join/prune is
<S,G> or <*,G>.
3.2. Lack of Hello Message considration
The following should be considered on a PLR domain since hello
messages are not processed.
3.2.1. Join Attribute
Since PLI does not process the pim hello message, processing of the
join attributes option in pim hello as per [RFC5384] is also not
supported, leaving PLRs unaware if their neighbors have the
capability of processing the join attribute. A PLR that does not
understand the type 1 Encoded-source Address, should not process a
join message that contains it. Otherwise the PLR can process the
Join Attribute accordingly.
3.2.2. DR Selection
Since DR selection is not supported on the PLR because of lack of
hello messages, the network design should ensure that DR selection is
achieve on the PIM domain, assuming the PLR domain is connecting PIM
domains.
As an example, in a BIER domain which is connecting 2 PIM networks, a
PLI can be used between the BIER edge routers. The PLI will be only
used for multicast states communication, by transmitting ONLY PIM
Join/prunes over the BIER domain. In this case to ensure there is no
multicast stream duplication the PIM routers attached on each side of
the BIER domain might want to establish PIM Adjacency via [RFC7761]
to ensure DR selection on the edge of the BIER router, while PLI is
used in the BIER domain, between BIER edge routers. When the Join or
Prune message arrives from a PIM domain to the down stream BIER edge
router, it can be send over the BIER tunnel to the upstream BIER edge
router only via the selected designated router.
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3.3. PLI Configuration
Since a PLI doesn't require PIM Hello Messages and PIM neighbor
adjacency is not checked for join/prune messages, there needs to be a
mechanism to enable PLI on interfaces for security purpose, while on
some other interfaces this may be enabled automatically. An example
of the latter is the logical interface for a BIER sub-domain
[draft-ietf-bier-pim-signaling].
If a system explicitly needs a PLI to be configured, then this system
should not accepts the Join/Prune messages on interfaces that the PLI
is not configured on, and it should drop these messages on a non PLI
interface. If the system automatically enables PLI on some special
interfaces, as an example interfaces facing a BIER domain, then it
should accept Join/Prune messages on these interfaces only.
3.4. Failures in PLR domain
Because the hello messages are not processed on the PLI, some
failures may not be discovered in PLI domain and multicast routes
will not be pruned toward the source on the PIM domain, leaving the
upstream routers continuously sending multicast streams.
Other protocols can be used to detect these failures in the PLR
domain and they can be implementation specific. As an example, the
interface that PLR is configured on can be protected via BFD or
similar technology. If BFD to the far-end PLR goes down, and the PLR
is upstream and is an OIF for a multicast route <S,G>, PIM should
remove that PLR from its OIF list. In addition if upstream PLR is
configured automatically, as an example in BIER case, when the
downstream BFR is no longer reachable, the upstream PLR can prune the
<S,G> advertised by that BFR, toward the source to stop the
transmission of the multicast stream.
4. IANA Considerations
5. Security Considerations
6. Acknowledgments
7. References
7.1. Normative References
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[draft-ietf-bier-pim-signaling]
"H.Bidgoli, F.XU, J. Kotalwar, I. Wijnands, M.Mishra, Z.
Zhang, "PIM Signaling Through BIER Core"", July 2021.
[iana_pim-parameters]
"", January 2022.
[RFC2119] "S. Brandner, "Key words for use in RFCs to Indicate
Requirement Levels"", March 1997.
[RFC5384] "A. Boers, I. Wijnands, E. Rosen "PIM Join Attribute
Format"", March 2016.
[RFC7761] "B.Fenner, M.Handley, H. Holbrook, I. Kouvelas, R. Parekh,
Z.Zhang "PIM Sparse Mode"", March 2016.
[RFC8174] "B. Leiba, "ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words"", May 2017.
7.2. Informative References
[RFC8279] "Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T.
and S. Aldrin, "Multicast using Bit Index Explicit
Replication"", October 2016.
Authors' Addresses
Hooman Bidgoli (editor)
Nokia
Ottawa
Canada
Email: hooman.bidgoli@nokia.com
Stig
Cisco System, Inc.
San Jose,
United States of America
Email: stig@cisco.com
Mankamana Mishra
Cisco System
Milpitas,
United States of America
Email: mankamis@cisco.com
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Zhaohui Zhang
Juniper Networks
Boston,
United States of America
Email: zzhang@juniper.com
Mike
Futurewei Technologies Inc.
Santa Clara,
United States of America
Email: michael.mcbride@futurewei.com
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