Internet DRAFT - draft-hb-pim-p2mp-policy-ping
draft-hb-pim-p2mp-policy-ping
Network Working Group H. Bidgoli, Ed.
Internet-Draft Nokia
Intended status: Standards Track V. Voyer
Expires: 17 May 2022 Bell Canada
P. Parekh
Cisco System
Z. Zhang
Juniper Networks
13 November 2021
P2MP Policy Ping
draft-hb-pim-p2mp-policy-ping-03
Abstract
SR P2MP policies are set of policies that enable architecture for
P2MP service delivery. A P2MP Policy consists of candidate paths
that connects the Root of the Tree to a set of Leaves. The P2MP
policy is composed of replication segments. A replication segment is
a forwarding instruction for a candidate path which is downloaded to
the Root, transit nodes and the leaves.
This document describes a simple and efficient mechanism that can be
used to detect data plane failures in P2MP Policy Candidate Paths
(CPs) and Path Instances (PIs).
Status of This Memo
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. MPLS P2MP Policy Ping and Traceroute . . . . . . . . . . 3
3.2. Packet format and new TLVs . . . . . . . . . . . . . . . 4
3.2.1. Identifying a P2MP Policy . . . . . . . . . . . . . . 4
3.2.1.1. P2MP Policy CP FEC Stack Sub-TLVs . . . . . . . . 4
3.3. Limiting the Scope of Response . . . . . . . . . . . . . 5
4. IANA Consideration . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Each P2MP Policy can have multiple CPs. The CP with highest
preference is the active CP while all other CPs are the backup CPs.
A CP can have multiple PIs to allow global optimization of the CP via
Make Before Break procedures between the active PI and the newly
setup and optimized PI.
It is desirable to test the end to end connectivity of a CP, whether
it is the active CP or a backup CP and all the CP's PIs. This
document describes a mechanism that can be used to detect data plane
failures in P2MP Policy Candidate Paths (CP) and its associate Path
Instances (PI).
This draft is only for replication SIDs that use MPLS encap for their
forwarding and not SRv6. It reuses most of the concepts in [RFC6425]
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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.
3. Motivation
A P2MP Policy and its corresponding Replication Segments are usually
setup via a controller, the root and the leaves are discovered as per
[draft-ietf-pim-sr-p2mp-policy-02]. The tree is calculated from the
root to the leaves. There is no underlay protocol to signal the P2MP
Policy from the root to the Leaf routers, as such when a P2MP tree
fails to deliver user traffic, the failure can be difficult to pin
point without a ping/traceroute mechanism to isolate the fault in the
P2MP tree. The P2MP Policy ping/traceroute can be utilize to detect
faults on the path of the tree and its associated replication
segments [draft-ietf-spring-segment-routing-policy-13]. These tools
can be used to periodically ping the leaves to ensure connectivity.
If the ping fails, trace route can be initiated to determine where
the failure lies. The ping/traceroute can be initiated from the node
that initiates the P2MP policy.
3.1. MPLS P2MP Policy Ping and Traceroute
Ping/Traceroute packets are forwarded on the P2MP Policy, on a
specific CP or its active PI toward the leaf routers. They are
replicated at the replication point based on the replication segment
forwarding information on the corresponding node. This draft only
addresses the replication segments that use MPLS encap only, future
drafts will address the SRv6 forwarding. The packet are processed
accordingly when their TTL expires or when the egress router (leaf)
is reached. The appropriate respond is send back to the root as per
procedures in [RFC6425]
This draft reuses most procedures for mLDP in RFC [RFC6425]
This draft also reuses the same destination UDP port as [RFC4379]
The implementation should take into account that there can be many
CPs under the P2MP Policy and the implementation should allow each CP
and its corresponding PI to be tested via Ping and Trace route. The
Ping and Traceroute packet is forwarded via that specific CP and its
corresponding replication segments. On the egress node the
corresponding CP and its PI should respond irrespective if it is the
active CP or a backup CP.
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Two replication segments can be connected via a unicast SR domain.
In this scenario the SR tunnel labels need to be programmed with the
right TTL depending on the which type of hierarchical MPLS TTL mode
is used. As an example pipe vs uniform mode. When in SR domain the
P2MP Tree PING and Traceroute will be processed on the two connecting
replication segments based on the replication SID and its TTL. As
such the SR domain will act as a single hop on the replication SID
and the replication SID TTL is subtracted by one before the unicast
SR SIDs are pushed on the replication SID. To detect failure in SR
domain is beyond the scope of this draft.
3.2. Packet format and new TLVs
The packet format used is as per [RFC4379] section 3. Some new TLVs
and sub-TLVs are required to support the new functionality. They are
described in the following sections.
3.2.1. Identifying a P2MP Policy
[RFC4379] defines how an MPLS TE LSP under test may be identified in
an echo request.In order to identify the correct replication segment
for the CP and its PI, the echo request message MUST carry a Target
FEC Stack TLV, and this MUST carry exactly one of one new sub-TLV: a
P2MP policy MPLS CP FEC Stack sub-TLV. The new sub-TLV is assigned
Sub-Type identifiers as follows, and are described in the following
sections.
artwork
Sub-Type Length Value Field
-------- ------ -----------
42 xx P2MP Policy MPLS CP
3.2.1.1. P2MP Policy CP FEC Stack Sub-TLVs
The format of the P2MP Policy Session sub-TLV value field is
specified in the following figure. The value fields are taken from
the definitions of the P2MP Policy section 3 of
[draft-ietf-pim-sr-p2mp-policy-02]
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artwork
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | Address Length| Root Addr |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Root Address (Cont.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TreeId length | Tree-ID ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path-Instance length | Path-instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* Address Family: Two-octet quantity, containing a value from
ADDRESS FAMILY NUMBERS in [IANA-AF] that encodes the address
family for the Root Address.
* Address Length: Length of the Root Address in octets.
* Root Address: The address of Root node of P2MP tree instantiated
by the SR P2MP Policy
* TreeId Length: Length of the TreeID in octets. This should be set
to 4 octets
* Tree-ID: A identifier that is unique in context of the Root. This
is an unsigned 32-bit number.
* Path-instance Length: Length of the path instance ID in octet.
* path-instance: path instance ID to be tested
[draft-ietf-spring-segment-routing-policy-13]
3.3. Limiting the Scope of Response
As per [RFC6425] section 3.2 Four sub-TLVs are used for the inclusion
in the P2MP Responder Identifier TLV carried on the echo request
message.
The Sub-TLVs for IPv4 and IPv6 egress address P2MP responder is in
par with [RFC6425] section 3.2.1
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The Sub-TLVs for IPv4 and IPv6 node address P2MP responder is in par
with [RFC6425] section 3.2.2
4. IANA Consideration
Two new sub-TLV types are defined for inclusion within the LSP ping
[RFC4379] Target FEC Stack TLV (TLV type 1).
5. Security Considerations
TBD
6. Acknowledgments
7. References
7.1. Normative References
[RFC2119] "S. Brandner, "Key words for use in RFCs to Indicate
Requirement Levels"", March 1997.
[RFC8174] "B. Leiba, "ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words"", May 2017.
7.2. Informative References
[draft-ietf-pim-sr-p2mp-policy-02]
"D. Yoyer, C. Filsfils, R.Prekh, H.bidgoli, Z. Zhang,
"draft-voyer-pim-sr-p2mp-policy"", October 2019.
[draft-ietf-spring-segment-routing-policy-13]
"D. Yoyer, C. Filsfils, R.Prekh, H.bidgoli, Z. Zhang,
"draft-voyer-pim-sr-p2mp-policy "draft-voyer-spring-sr-
replication-segment"", July 2020.
[RFC4379] "K. Kompella, G. Swallow", February 2006.
[RFC6425] "S. Saxena, G. Swallow, Z. Ali, A. Farrel, S. Yasukawa,
T.Nadeau "Detecting Data-Plane Failures in Point-to-
Multipoint MPLS"", November 2011.
Authors' Addresses
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Hooman Bidgoli (editor)
Nokia
Ottawa
Canada
Email: hooman.bidgoli@nokia.com
Daniel Voyer
Bell Canada
Montreal
Canada
Email: daniel.yover@bell.ca
Rishabh Parekh
Cisco System
San Jose,
United States of America
Email: riparekh@cisco.com
Zhaohui Zhang
Juniper Networks
Boston,
United States of America
Email: zzhang@juniper.com
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