draft-ietf-mpls-lsp-ping-lag-multipath-08.txt   rfc8611.txt 
Internet Engineering Task Force N. Akiya Internet Engineering Task Force (IETF) N. Akiya
Internet-Draft Big Switch Networks Request for Comments: 8611 Big Switch Networks
Updates: 8029 (if approved) G. Swallow Updates: 8029 G. Swallow
Intended status: Standards Track Cisco Systems Category: Standards Track SETC
Expires: October 6, 2019 S. Litkowski ISSN: 2070-1721 S. Litkowski
B. Decraene B. Decraene
Orange Orange
J. Drake J. Drake
Juniper Networks Juniper Networks
M. Chen M. Chen
Huawei Huawei
April 04, 2019 June 2019
Label Switched Path (LSP) Ping/Trace Multipath Support for Label Switched Path (LSP) Ping and Traceroute Multipath Support
Link Aggregation Group (LAG) Interfaces for Link Aggregation Group (LAG) Interfaces
draft-ietf-mpls-lsp-ping-lag-multipath-08
Abstract Abstract
This document defines extensions to the MPLS Label Switched Path This document defines extensions to the MPLS Label Switched Path
(LSP) Ping and Traceroute mechanisms as specified in RFC 8029. The (LSP) Ping and Traceroute mechanisms as specified in RFC 8029. The
extensions allow the MPLS LSP Ping and Traceroute mechanisms to extensions allow the MPLS LSP Ping and Traceroute mechanisms to
discover and exercise specific paths of Layer 2 (L2) Equal-Cost discover and exercise specific paths of Layer 2 (L2) Equal-Cost
Multipath (ECMP) over Link Aggregation Group (LAG) interfaces. Multipath (ECMP) over Link Aggregation Group (LAG) interfaces.
Additionally, a mechanism is defined to enable determination of the Additionally, a mechanism is defined to enable the determination of
capabilities of an LSR supported. the capabilities supported by a Label Switching Router (LSR).
This document updates RFC8029.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", This document updates RFC 8029.
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on October 6, 2019. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8611.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Overview of Solution . . . . . . . . . . . . . . . . . . . . 4 2. Overview of Solution . . . . . . . . . . . . . . . . . . . . 4
3. LSR Capability Discovery . . . . . . . . . . . . . . . . . . 6 3. LSR Capability Discovery . . . . . . . . . . . . . . . . . . 6
3.1. Initiator LSR Procedures . . . . . . . . . . . . . . . . 7 3.1. Initiator LSR Procedures . . . . . . . . . . . . . . . . 7
3.2. Responder LSR Procedures . . . . . . . . . . . . . . . . 7 3.2. Responder LSR Procedures . . . . . . . . . . . . . . . . 7
4. Mechanism to Discover L2 ECMP Multipath . . . . . . . . . . . 7 4. Mechanism to Discover L2 ECMP . . . . . . . . . . . . . . . . 7
4.1. Initiator LSR Procedures . . . . . . . . . . . . . . . . 7 4.1. Initiator LSR Procedures . . . . . . . . . . . . . . . . 7
4.2. Responder LSR Procedures . . . . . . . . . . . . . . . . 8 4.2. Responder LSR Procedures . . . . . . . . . . . . . . . . 8
4.3. Additional Initiator LSR Procedures . . . . . . . . . . . 10 4.3. Additional Initiator LSR Procedures . . . . . . . . . . . 10
5. Mechanism to Validate L2 ECMP Traversal . . . . . . . . . . . 11 5. Mechanism to Validate L2 ECMP Traversal . . . . . . . . . . . 11
5.1. Incoming LAG Member Links Verification . . . . . . . . . 11 5.1. Incoming LAG Member Links Verification . . . . . . . . . 11
5.1.1. Initiator LSR Procedures . . . . . . . . . . . . . . 11 5.1.1. Initiator LSR Procedures . . . . . . . . . . . . . . 11
5.1.2. Responder LSR Procedures . . . . . . . . . . . . . . 12 5.1.2. Responder LSR Procedures . . . . . . . . . . . . . . 12
5.1.3. Additional Initiator LSR Procedures . . . . . . . . . 12 5.1.3. Additional Initiator LSR Procedures . . . . . . . . . 12
5.2. Individual End-to-End Path Verification . . . . . . . . . 14 5.2. Individual End-to-End Path Verification . . . . . . . . . 14
6. LSR Capability TLV . . . . . . . . . . . . . . . . . . . . . 14 6. LSR Capability TLV . . . . . . . . . . . . . . . . . . . . . 14
7. LAG Description Indicator Flag: G . . . . . . . . . . . . . . 15 7. LAG Description Indicator Flag: G . . . . . . . . . . . . . . 15
8. Local Interface Index Sub-TLV . . . . . . . . . . . . . . . . 16 8. Local Interface Index Sub-TLV . . . . . . . . . . . . . . . . 16
9. Remote Interface Index Sub-TLV . . . . . . . . . . . . . . . 16 9. Remote Interface Index Sub-TLV . . . . . . . . . . . . . . . 17
10. Detailed Interface and Label Stack TLV . . . . . . . . . . . 17 10. Detailed Interface and Label Stack TLV . . . . . . . . . . . 17
10.1. Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . . 19 10.1. Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1.1. Incoming Label Stack Sub-TLV . . . . . . . . . . . . 19 10.1.1. Incoming Label Stack Sub-TLV . . . . . . . . . . . . 19
10.1.2. Incoming Interface Index Sub-TLV . . . . . . . . . . 20 10.1.2. Incoming Interface Index Sub-TLV . . . . . . . . . . 20
11. Rate Limiting On Echo Request/Reply Messages . . . . . . . . 21 11. Rate-Limiting on Echo Request/Reply Messages . . . . . . . . 21
12. Security Considerations . . . . . . . . . . . . . . . . . . . 21 12. Security Considerations . . . . . . . . . . . . . . . . . . . 21
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
13.1. LSR Capability TLV . . . . . . . . . . . . . . . . . . . 21 13.1. LSR Capability TLV . . . . . . . . . . . . . . . . . . . 22
13.1.1. LSR Capability Flags . . . . . . . . . . . . . . . . 22 13.1.1. LSR Capability Flags . . . . . . . . . . . . . . . . 22
13.2. Local Interface Index Sub-TLV . . . . . . . . . . . . . 22 13.2. Local Interface Index Sub-TLV . . . . . . . . . . . . . 22
13.2.1. Interface Index Flags . . . . . . . . . . . . . . . 22 13.2.1. Interface Index Flags . . . . . . . . . . . . . . . 22
13.3. Remote Interface Index Sub-TLV . . . . . . . . . . . . . 23 13.3. Remote Interface Index Sub-TLV . . . . . . . . . . . . . 23
13.4. Detailed Interface and Label Stack TLV . . . . . . . . . 23 13.4. Detailed Interface and Label Stack TLV . . . . . . . . . 23
13.4.1. Sub-TLVs for TLV Type TBD4 . . . . . . . . . . . . . 23 13.4.1. Sub-TLVs for TLV Type 6 . . . . . . . . . . . . . . 23
13.4.2. Interface and Label Stack Address Types . . . . . . 24 13.4.2. Interface and Label Stack Address Types . . . . . . 25
13.5. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 24 13.5. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 25
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 14.1. Normative References . . . . . . . . . . . . . . . . . . 25
15.1. Normative References . . . . . . . . . . . . . . . . . . 25 14.2. Informative References . . . . . . . . . . . . . . . . . 26
15.2. Informative References . . . . . . . . . . . . . . . . . 25 Appendix A. LAG with Intermediate L2 Switch Issues . . . . . . . 27
Appendix A. LAG with intermediate L2 Switch Issues . . . . . . . 26 A.1. Equal Numbers of LAG Members . . . . . . . . . . . . . . 27
A.1. Equal Numbers of LAG Members . . . . . . . . . . . . . . 26 A.2. Deviating Numbers of LAG Members . . . . . . . . . . . . 27
A.2. Deviating Numbers of LAG Members . . . . . . . . . . . . 26
A.3. LAG Only on Right . . . . . . . . . . . . . . . . . . . . 27 A.3. LAG Only on Right . . . . . . . . . . . . . . . . . . . . 27
A.4. LAG Only on Left . . . . . . . . . . . . . . . . . . . . 27 A.4. LAG Only on Left . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
1.1. Terminology 1.1. Background
The MPLS Label Switched Path (LSP) Ping and Traceroute mechanisms
[RFC8029] are powerful tools designed to diagnose all available
Layer 3 (L3) paths of LSPs, including diagnostic coverage of L3
Equal-Cost Multipath (ECMP). In many MPLS networks, Link Aggregation
Groups (LAGs), as defined in [IEEE802.1AX], provide Layer 2 (L2) ECMP
and are often used for various reasons. MPLS LSP Ping and Traceroute
tools were not designed to discover and exercise specific paths of L2
ECMP. This produces a limitation for the following scenario when an
LSP traverses a LAG:
o Label switching over some member links of the LAG is successful,
but fails over other member links of the LAG.
o MPLS echo request for the LSP over the LAG is load-balanced on one
of the member links that is label switching successfully.
With the above scenario, MPLS LSP Ping and Traceroute will not be
able to detect the label-switching failure of the problematic member
link(s) of the LAG. In other words, lack of L2 ECMP diagnostic
coverage can produce an outcome where MPLS LSP Ping and Traceroute
can be blind to label-switching failures over a problematic LAG
interface. It is, thus, desirable to extend the MPLS LSP Ping and
Traceroute to have deterministic diagnostic coverage of LAG
interfaces.
The work toward a solution to this problem was motivated by issues
encountered in live networks.
1.2. Terminology
The following acronyms/terms are used in this document: The following acronyms/terms are used in this document:
o MPLS - Multiprotocol Label Switching. o MPLS - Multiprotocol Label Switching.
o LSP - Label Switched Path. o LSP - Label Switched Path.
o LSR - Label Switching Router. o LSR - Label Switching Router.
o ECMP - Equal-Cost Multipath. o ECMP - Equal-Cost Multipath.
o LAG - Link Aggregation Group. o LAG - Link Aggregation Group.
o Initiator LSR - The LSR which sends the MPLS echo request message. o Initiator LSR - The LSR that sends the MPLS echo request message.
o Responder LSR - The LSR which receives the MPLS echo request o Responder LSR - The LSR that receives the MPLS echo request
message and sends the MPLS echo reply message. message and sends the MPLS echo reply message.
1.2. Background 1.3. Requirements Language
The MPLS Label Switched Path (LSP) Ping and Traceroute mechanisms
[RFC8029] are powerful tools designed to diagnose all available Layer
3 (L3) paths of LSPs, including diagnostic coverage of L3 Equal-Cost
Multipath (ECMP). In many MPLS networks, Link Aggregation Group
(LAG) as defined in [IEEE802.1AX], which provides Layer 2 (L2) ECMP,
is often used for various reasons. MPLS LSP Ping and Traceroute
tools were not designed to discover and exercise specific paths of L2
ECMP. This raises a limitation for the following scenario when an
LSP traverses over a LAG:
o Label switching over some member links of the LAG is successful,
but fails over other member links of the LAG.
o MPLS echo request for the LSP over the LAG is load balanced on one
of the member links which is label switching successfully.
With the above scenario, MPLS LSP Ping and Traceroute will not be
able to detect the label switching failure of the problematic member
link(s) of the LAG. In other words, lack of L2 ECMP diagnostic
coverage can produce an outcome where MPLS LSP Ping and Traceroute
can be blind to label switching failures over a problematic LAG
interface. It is, thus, desirable to extend the MPLS LSP Ping and
Traceroute to have deterministic diagnostic coverage of LAG
interfaces.
The need for a solution of this problem was motivated by issues The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
encountered in live networks. "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. Overview of Solution 2. Overview of Solution
This document defines a new TLV to discover the capabilities of a This document defines a new TLV to discover the capabilities of a
responder LSR and extensions for use with the MPLS LSP Ping and responder LSR and extensions for use with the MPLS LSP Ping and
Traceroute mechanisms to describe Multipath Information for Traceroute mechanisms to describe Multipath Information for
individual LAG member links, thus allowing MPLS LSP Ping and individual LAG member links, thus allowing MPLS LSP Ping and
Traceroute to discover and exercise specific paths of L2 ECMP over Traceroute to discover and exercise specific paths of L2 ECMP over
LAG interfaces. The reader is expected to be familiar with mechanics LAG interfaces. The reader is expected to be familiar with the
Downstream Detailed Mapping TLV (DDMAP) described in Section 3.4 of Downstream Detailed Mapping TLV (DDMAP) described in Section 3.4 of
[RFC8029]. [RFC8029].
The solution consists of the MPLS echo request containing a DDMAP TLV The solution consists of the MPLS echo request containing a DDMAP TLV
and the new LSR Capability TLV to indicate that separate load and the new LSR Capability TLV to indicate that separate load-
balancing information for each L2 nexthop over LAG is desired in the balancing information for each L2 next hop over LAG is desired in the
MPLS echo reply. The Responder LSR places the same LSR Capability MPLS echo reply. The responder LSR places the same LSR Capability
TLV in the MPLS echo reply to provide acknowledgement back to the TLV in the MPLS echo reply to provide acknowledgement back to the
initiator LSR. It also adds, for each downstream LAG member, load initiator LSR. It also adds, for each downstream LAG member, load-
balance information (i.e., multipath information and interface balancing information (i.e., multipath information and interface
index). This mechanism is applicable to all types of LSPs which can index). This mechanism is applicable to all types of LSPs that can
traverse over LAG interfaces. Many LAGs are built from p2p links, traverse LAG interfaces. Many LAGs are built from peer-to-peer
with router X and router X+1 having direct connectivity and the same links, with router X and router X+1 having direct connectivity and
number of LAG members. It is possible to build LAGs asymmetrically the same number of LAG members. It is possible to build LAGs
by using Ethernet switches between two routers. Appendix A lists asymmetrically by using Ethernet switches between two routers.
some use cases for which the mechanisms defined in this document may Appendix A lists some use cases for which the mechanisms defined in
not be applicable. Note that the mechanisms described in this this document may not be applicable. Note that the mechanisms
document do not impose any changes to scenarios where an LSP is described in this document do not impose any changes to scenarios
pinned down to a particular LAG member (i.e. the LAG is not treated where an LSP is pinned down to a particular LAG member (i.e., the LAG
as one logical interface by the LSP). is not treated as one logical interface by the LSP).
The following figure and description provides an example using an LDP The following figure and description provide an example of an LDP
network. network.
<----- LDP Network -----> <----- LDP Network ----->
+-------+ +-------+
| | | |
A-------B=======C-------E A-------B=======C-------E
| | | |
+-------D-------+ +-------D-------+
---- Non-LAG ---- Non-LAG
==== LAG comprising of two member links ==== LAG comprising of two member links
Figure 1: Example LDP Network Figure 1: Example LDP Network
When node A is initiating LSP Traceroute to node E, node B will When node A is initiating LSP Traceroute to node E, node B will
return to node A load balance information for following entries. return to node A load-balancing information for the following
entries:
1. Downstream C over Non-LAG (upper path). 1. Downstream C over Non-LAG (upper path).
2. First Downstream C over LAG (middle path). 2. First Downstream C over LAG (middle path).
3. Second Downstream C over LAG (middle path). 3. Second Downstream C over LAG (middle path).
4. Downstream D over Non-LAG (lower path). 4. Downstream D over Non-LAG (lower path).
This document defines: This document defines:
o In Section 3, a mechanism to discover capabilities of responder o in Section 3, a mechanism to discover capabilities of responder
LSRs; LSRs;
o In Section 4, a mechanism to discover L2 ECMP multipath o in Section 4, a mechanism to discover L2 ECMP information;
information;
o In Section 5, a mechanism to validate L2 ECMP traversal; o in Section 5, a mechanism to validate L2 ECMP traversal;
o In Section 6, the LSR Capability TLV; o in Section 6, the LSR Capability TLV;
o In Section 7, the LAG Description Indicator flag; o in Section 7, the LAG Description Indicator flag;
o In Section 8, the Local Interface Index Sub-TLV; o in Section 8, the Local Interface Index Sub-TLV;
o In Section 9, the Remote Interface Index Sub-TLV; o in Section 9, the Remote Interface Index Sub-TLV; and
o In Section 10, the Detailed Interface and Label Stack TLV; o in Section 10, the Detailed Interface and Label Stack TLV.
3. LSR Capability Discovery 3. LSR Capability Discovery
The MPLS Ping operates by an initiator LSR sending an MPLS echo The MPLS Ping operates by an initiator LSR sending an MPLS echo
request message and receiving back a corresponding MPLS echo reply request message and receiving back a corresponding MPLS echo reply
message from a responder LSR. The MPLS Traceroute operates in a message from a responder LSR. The MPLS Traceroute operates in a
similar way except the initiator LSR potentially sends multiple MPLS similar way except the initiator LSR potentially sends multiple MPLS
echo request messages with incrementing TTL values. echo request messages with incrementing TTL values.
There have been many extensions to the MPLS Ping and Traceroute There have been many extensions to the MPLS Ping and Traceroute
mechanisms over the years. Thus it is often useful, and sometimes mechanisms over the years. Thus, it is often useful, and sometimes
necessary, for the initiator LSR to deterministically disambiguate necessary, for the initiator LSR to deterministically disambiguate
the differences between: the differences between:
o The responder LSR sent the MPLS echo reply message with contents C o The responder LSR sent the MPLS echo reply message with contents C
because it has feature X, Y and Z implemented. because it has feature X, Y, and Z implemented.
o The responder LSR sent the MPLS echo reply message with contents C o The responder LSR sent the MPLS echo reply message with contents C
because it has subset of features X, Y and Z implemented but not because it has a subset of features X, Y, and Z (i.e., not all of
all. them) implemented.
o The responder LSR sent the MPLS echo reply message with contents C o The responder LSR sent the MPLS echo reply message with contents C
because it does not have features X, Y and Z implemented. because it does not have features X, Y, or Z implemented.
To allow the initiator LSR to disambiguate the above differences, To allow the initiator LSR to disambiguate the above differences,
this document defines the LSR Capability TLV (described in this document defines the LSR Capability TLV (described in
Section 6). When the initiator LSR wishes to discover the Section 6). When the initiator LSR wishes to discover the
capabilities of the responder LSR, the initiator LSR includes the LSR capabilities of the responder LSR, the initiator LSR includes the LSR
Capability TLV in the MPLS echo request message. When the responder Capability TLV in the MPLS echo request message. When the responder
LSR receives an MPLS echo request message with the LSR Capability TLV LSR receives an MPLS echo request message with the LSR Capability TLV
included, if it knows the LSR Capability TLV, then it MUST include included, if it knows the LSR Capability TLV, then it MUST include
the LSR Capability TLV in the MPLS echo reply message with the LSR the LSR Capability TLV in the MPLS echo reply message with the LSR
Capability TLV describing features and extensions supported by the Capability TLV describing the features and extensions supported by
local LSR. Otherwise, an MPLS echo reply must be sent back to the the local LSR. Otherwise, an MPLS echo reply must be sent back to
initiator LSR with the return code set to "One or more of the TLVs the initiator LSR with the return code set to "One or more of the
was not understood", according to the rules as defined Section 3 of TLVs was not understood", according to the rules defined in Section 3
[RFC8029]. Then the initiator LSR can send another MPLS echo request of [RFC8029]. Then, the initiator LSR can send another MPLS echo
without including the LSR Capability TLV. request without including the LSR Capability TLV.
It is RECOMMENDED that implementations supporting the LAG Multipath It is RECOMMENDED that implementations supporting the LAG multipath
extensions defined in this document include the LSR Capability TLV in extensions defined in this document include the LSR Capability TLV in
MPLS echo request messages. MPLS echo request messages.
3.1. Initiator LSR Procedures 3.1. Initiator LSR Procedures
If an initiator LSR does not know what capabilities a responder LSR If an initiator LSR does not know what capabilities a responder LSR
can support, it can send an MPLS each request message and carry the can support, it can send an MPLS echo request message and carry the
LSR Capability TLV to the responder to discover the capabilities that LSR Capability TLV to the responder to discover the capabilities that
the responder LSR can support. the responder LSR can support.
3.2. Responder LSR Procedures 3.2. Responder LSR Procedures
When a responder LSR received an MPLS echo request message that When a responder LSR receives an MPLS echo request message that
carries the LSR Capability TLV, the following procedures are used: carries the LSR Capability TLV, the following procedures are used:
If the responder knows how to process the LSR Capability TLV, the If the responder knows how to process the LSR Capability TLV, the
following procedures are used: following procedures are used:
o The responder LSR MUST include the LSR Capability TLV in the MPLS o The responder LSR MUST include the LSR Capability TLV in the MPLS
echo reply message. echo reply message.
o If the responder LSR understands the "LAG Description Indicator o If the responder LSR understands the LAG Description Indicator
flag": flag:
* Set the "Downstream LAG Info Accommodation flag" if the * Set the Downstream LAG Info Accommodation flag if the responder
responder LSR is capable of describing outgoing LAG member LSR is capable of describing the outgoing LAG member links
links separately; otherwise, clear the "Downstream LAG Info separately; otherwise, clear the Downstream LAG Info
Accommodation flag". Accommodation flag.
* Set the "Upstream LAG Info Accommodation flag" if responder LSR * Set the Upstream LAG Info Accommodation flag if the responder
is capable of describing incoming LAG member links separately; LSR is capable of describing the incoming LAG member links
otherwise, clear the "Upstream LAG Info Accommodation flag". separately; otherwise, clear the Upstream LAG Info
Accommodation flag.
4. Mechanism to Discover L2 ECMP Multipath 4. Mechanism to Discover L2 ECMP
4.1. Initiator LSR Procedures 4.1. Initiator LSR Procedures
Through the "LSR Capability Discovery" as defined in Section 3, the Through LSR Capability Discovery as defined in Section 3, the
initiator LSR can understand whether the responder LSR can describe initiator LSR can understand whether the responder LSR can describe
incoming/outgoing LAG member links separately in the DDMAP TLV. incoming/outgoing LAG member links separately in the DDMAP TLV.
Once the initiator LSR knows that a responder can support this Once the initiator LSR knows that a responder can support this
mechanism, then it sends an MPLS echo request carrying a DDMAP TLV mechanism, then it sends an MPLS echo request carrying a DDMAP TLV
with the "LAG Description Indicator flag" (G) set to the responder with the LAG Description Indicator flag (G) set to the responder LSR.
LSR. The "LAG Description Indicator flag" (G) indicates that The LAG Description Indicator flag (G) indicates that separate load-
separate load balancing information for each L2 nexthop over a LAG is balancing information for each L2 next hop over a LAG is desired in
desired in the MPLS echo reply. The new "LAG Description Indicator the MPLS echo reply. The new LAG Description Indicator flag is
flag" is described in Section 7. described in Section 7.
4.2. Responder LSR Procedures 4.2. Responder LSR Procedures
When a responder LSR received an MPLS echo request message with the When a responder LSR receives an MPLS echo request message with the
"LAG Description Indicator flag" set in the DDMAP TLV, if the LAG Description Indicator flag set in the DDMAP TLV, if the responder
responder LSR understands the "LAG Description Indicator flag" and is LSR understands the LAG Description Indicator flag and is capable of
capable of describing outgoing LAG member links separately, the describing outgoing LAG member links separately, the following
following procedures are used, regardless of whether or not outgoing procedures are used, regardless of whether or not the outgoing
interfaces include LAG interfaces: interfaces include LAG interfaces:
o For each downstream that is a LAG interface: o For each downstream interface that is a LAG interface:
* The responder LSR MUST include a DDMAP TLV when sending the * The responder LSR MUST include a DDMAP TLV when sending the
MPLS echo reply. There is a single DDMAP TLV for the LAG MPLS echo reply. There is a single DDMAP TLV for the LAG
interface, with member links described using sub-TLVs. interface, with member links described using sub-TLVs.
* The responder LSR MUST set the "LAG Description Indicator flag" * The responder LSR MUST set the LAG Description Indicator flag
in the DS Flags field of the DDMAP TLV. in the DS Flags field of the DDMAP TLV.
* In the DDMAP TLV, the Local Interface Index Sub-TLV, Remote * In the DDMAP TLV, the Local Interface Index Sub-TLV, Remote
Interface Index Sub-TLV and Multipath Data Sub-TLV are used to Interface Index Sub-TLV, and Multipath Data Sub-TLV are used to
describe each LAG member link. All other fields of the DDMAP describe each LAG member link. All other fields of the DDMAP
TLV are used to describe the LAG interface. TLV are used to describe the LAG interface.
* For each LAG member link of the LAG interface: * For each LAG member link of the LAG interface:
+ The responder LSR MUST add a Local Interface Index Sub-TLV + The responder LSR MUST add a Local Interface Index Sub-TLV
(described in Section 8) with the "LAG Member Link Indicator (described in Section 8) with the LAG Member Link Indicator
flag" set in the Interface Index Flags field, describing the flag set in the Interface Index Flags field. It describes
interface index of this outgoing LAG member link (the local the interface index of this outgoing LAG member link (the
interface index is assigned by the local LSR). local interface index is assigned by the local LSR).
+ The responder LSR MAY add a Remote Interface Index Sub-TLV + The responder LSR MAY add a Remote Interface Index Sub-TLV
(described in Section 9) with the "LAG Member Link Indicator (described in Section 9) with the LAG Member Link Indicator
flag" set in the Interface Index Flags field, describing the flag set in the Interface Index Flags field. It describes
interface index of the incoming LAG member link on the the interface index of the incoming LAG member link on the
downstream LSR (this interface index is assigned by the downstream LSR (this interface index is assigned by the
downstream LSR). How the local LSR obtains the interface downstream LSR). How the local LSR obtains the interface
index of the LAG member link on the downstream LSR is index of the LAG member link on the downstream LSR is
outside the scope of this document. outside the scope of this document.
+ The responder LSR MUST add an Multipath Data Sub-TLV for + The responder LSR MUST add a Multipath Data Sub-TLV for this
this LAG member link, if the received DDMAP TLV requested LAG member link, if the received DDMAP TLV requested
multipath information. multipath information.
Based on the procedures described above, every LAG member link will Based on the procedures described above, every LAG member link will
have a Local Interface Index Sub-TLV and a Multipath Data Sub-TLV have a Local Interface Index Sub-TLV and a Multipath Data Sub-TLV
entries in the DDMAP TLV. The order of the Sub-TLVs in the DDMAP TLV entry in the DDMAP TLV. The order of the sub-TLVs in the DDMAP TLV
for a LAG member link MUST be Local Interface Index Sub-TLV for a LAG member link MUST be Local Interface Index Sub-TLV
immediately followed by Multipath Data Sub-TLV except as follows. A immediately followed by Multipath Data Sub-TLV, except as follows. A
LAG member link MAY also have a corresponding Remote Interface Index LAG member link MAY also have a corresponding Remote Interface Index
Sub-TLV. When a Local Interface Index Sub-TLV, a Remote Interface Sub-TLV. When a Local Interface Index Sub-TLV, a Remote Interface
Index-Sub-TLV and a Multipath Data Sub-TLV are placed in the DDMAP Index Sub-TLV, and a Multipath Data Sub-TLV are placed in the DDMAP
TLV to describe a LAG member link, they MUST be placed in the order TLV to describe a LAG member link, they MUST be placed in the order
of Local Interface Index Sub-TLV, Remote Interface Index-Sub-TLV and of Local Interface Index Sub-TLV, Remote Interface Index Sub-TLV, and
Multipath Data Sub-TLV. The block of local interface index, Multipath Data Sub-TLV. The blocks of Local Interface Index, Remote
(optional remote interface index) and multipath data sub-TLVs for Interface Index (optional), and Multipath Data Sub-TLVs for each
each member link MUST appear adjacent to each other in order of member link MUST appear adjacent to each other and be in order of
increasing local interface index. increasing local interface index.
A responder LSR possessing a LAG interface with two member links A responder LSR possessing a LAG interface with two member links
would send the following DDMAP for this LAG interface: would send the following DDMAP for this LAG interface:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ DDMAP fields describing LAG interface with DS Flags G set ~ ~ DDMAP fields describing LAG interface (DS Flags with G set) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface Index Sub-TLV of LAG member link #1 | | Local Interface Index Sub-TLV of LAG member link #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface Index Sub-TLV of LAG member link #1 | | Remote Interface Index Sub-TLV of LAG member link #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath Data Sub-TLV LAG member link #1 | | Multipath Data Sub-TLV LAG member link #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface Index Sub-TLV of LAG member link #2 | | Local Interface Index Sub-TLV of LAG member link #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface Index Sub-TLV of LAG member link #2 | | Remote Interface Index Sub-TLV of LAG member link #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath Data Sub-TLV LAG member link #2 | | Multipath Data Sub-TLV LAG member link #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Stack Sub-TLV | | Label Stack Sub-TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Example of DDMAP in MPLS Echo Reply Figure 2: Example of DDMAP in MPLS Echo Reply
When none of the received multipath information maps to a particular When none of the received multipath information maps to a particular
LAG member link, then the responder LSR MUST still place the Local LAG member link, then the responder LSR MUST still place the Local
Interface Index Sub-TLV and the Multipath Data Sub-TLV for that LAG Interface Index Sub-TLV and the Multipath Data Sub-TLV for that LAG
member link in the DDMAP TLV. The value of Multipath Length field of member link in the DDMAP TLV. The value of the Multipath Length
the Multipath Data Sub-TLV is set to zero. field of the Multipath Data Sub-TLV is set to zero.
4.3. Additional Initiator LSR Procedures 4.3. Additional Initiator LSR Procedures
The procedures above allow an initiator LSR to: The procedures in Section 4.2 allow an initiator LSR to:
o Identify whether or not the responder LSR can describe outgoing o Identify whether or not the responder LSR can describe outgoing
LAG member links separately, by looking at the LSR Capability TLV. LAG member links separately, by looking at the LSR Capability TLV.
o Utilize the value of the "LAG Description Indicator flag" in DS o Utilize the value of the LAG Description Indicator flag in DS
Flags to identify whether each received DDMAP TLV describes a LAG Flags to identify whether each received DDMAP TLV describes a LAG
interface or a non-LAG interface. interface or a non-LAG interface.
o Obtain multipath information which is expected to traverse the o Obtain multipath information that is expected to traverse the
specific LAG member link described by corresponding interface specific LAG member link described by the corresponding interface
index. index.
When an initiator LSR receives a DDMAP containing LAG member When an initiator LSR receives a DDMAP containing LAG member
information from a downstream LSR with TTL=n, then the subsequent information from a downstream LSR with TTL=n, then the subsequent
DDMAP sent by the initiator LSR to the downstream LSR with TTL=n+1 DDMAP sent by the initiator LSR to the downstream LSR with TTL=n+1
through a particular LAG member link MUST be updated with following through a particular LAG member link MUST be updated according to the
procedures: following procedures:
o The Local Interface Index Sub-TLVs MUST be removed in the sending o The Local Interface Index Sub-TLVs MUST be removed in the sending
DDMAP. DDMAP.
o If the Remote Interface Index Sub-TLVs were present and the o If the Remote Interface Index Sub-TLVs were present and the
initiator LSR is traversing over a specific LAG member link, then initiator LSR is traversing over a specific LAG member link, then
the Remote Interface Index Sub-TLV corresponding to the LAG member the Remote Interface Index Sub-TLV corresponding to the LAG member
link being traversed SHOULD be included in the sending DDMAP. All link being traversed SHOULD be included in the sending DDMAP. All
other Remote Interface Index Sub-TLVs MUST be removed from the other Remote Interface Index Sub-TLVs MUST be removed from the
sending DDMAP. sending DDMAP.
o The Multipath Data Sub-TLVs MUST be updated to include just one o The Multipath Data Sub-TLVs MUST be updated to include just one
Multipath Data Sub-TLV. The initiator LSR MAY just keep the Multipath Data Sub-TLV. The initiator LSR MAY just keep the
Multipath Data Sub-TLV corresponding to the LAG member link being Multipath Data Sub-TLV corresponding to the LAG member link being
traversed, or combine the Multipath Data Sub-TLVs for all LAG traversed or combine the Multipath Data Sub-TLVs for all LAG
member links into a single Multipath Data Sub-TLV when diagnosing member links into a single Multipath Data Sub-TLV when diagnosing
further downstream LSRs. further downstream LSRs.
o All other fields of the DDMAP are to comply with procedures o All other fields of the DDMAP are to comply with procedures
described in [RFC8029]. described in [RFC8029].
Figure 3 is an example that shows how to use the DDMAP TLV to notify Figure 3 is an example that shows how to use the DDMAP TLV to send a
which member link (link #1 in the example) will be chosen to send the notification about which member link (link #1 in the example) will be
MPLS echo request message to the next downstream LSR: chosen to send the MPLS echo request message to the next downstream
LSR:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ DDMAP fields describing LAG interface with DS Flags G set ~ ~ DDMAP fields describing LAG interface (DS Flags with G set) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|[OPTIONAL] Remote Interface Index Sub-TLV of LAG member link #1| |[OPTIONAL] Remote Interface Index Sub-TLV of LAG member link #1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath Data Sub-TLV LAG member link #1 | | Multipath Data Sub-TLV LAG member link #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Stack Sub-TLV | | Label Stack Sub-TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Example of DDMAP in MPLS Echo Request Figure 3: Example of DDMAP in MPLS Echo Request
5. Mechanism to Validate L2 ECMP Traversal 5. Mechanism to Validate L2 ECMP Traversal
Section 4 defines the responder LSR procedures to construct a DDMAP Section 4 defines the responder LSR procedures to construct a DDMAP
for a downstream LAG. The Remote Interface Index Sub-TLVs that for a downstream LAG. The Remote Interface Index Sub-TLV that
describes the incoming LAG member links of the downstream LSR is describes the incoming LAG member links of the downstream LSR is
optional, because this information from the downstream LSR is often optional, because this information from the downstream LSR is often
not available on the responder LSR. In such case, the traversal of not available on the responder LSR. In such case, the traversal of
LAG member links can be validated with procedures described in LAG member links can be validated with procedures described in
Section 5.1. If LSRs can provide the Remote Interface Index Sub- Section 5.1. If LSRs can provide the Remote Interface Index Sub-
TLVs, then the validation procedures described in Section 5.2 can be TLVs, then the validation procedures described in Section 5.2 can be
used. used.
5.1. Incoming LAG Member Links Verification 5.1. Incoming LAG Member Links Verification
Without downstream LSRs returning remote Interface Index Sub-TLVs in Without downstream LSRs returning Remote Interface Index Sub-TLVs in
the DDMAP, validation of the LAG member link traversal requires that the DDMAP, validation of the LAG member link traversal requires that
initiator LSR traverses all available LAG member links and taking the the initiator LSR traverses all available LAG member links and takes
results through a logic. This section provides the mechanism for the the results through additional logic. This section provides the
initiator LSR to obtain additional information from the downstream mechanism for the initiator LSR to obtain additional information from
LSRs and describes the additional logic in the initiator LSR to the downstream LSRs and describes the additional logic in the
validate the L2 ECMP traversal. initiator LSR to validate the L2 ECMP traversal.
5.1.1. Initiator LSR Procedures 5.1.1. Initiator LSR Procedures
An MPLS echo request carrying a DDMAP TLV with the "Interface and An MPLS echo request carrying a DDMAP TLV with the Interface and
Label Stack Object Request flag" and "LAG Description Indicator flag" Label Stack Object Request flag and LAG Description Indicator flag
set is sent to indicate the request for Detailed Interface and Label set is sent to indicate the request for Detailed Interface and Label
Stack TLV with additional LAG member link information (i.e. Stack TLV with additional LAG member link information (i.e.,
interface index) in the MPLS echo reply. interface index) in the MPLS echo reply.
5.1.2. Responder LSR Procedures 5.1.2. Responder LSR Procedures
When received an echo request with the "LAG Description Indicator When it receives an echo request with the LAG Description Indicator
flag" set, a responder LSR that understands the "LAG Description flag set, a responder LSR that understands that flag and is capable
Indicator flag" and is capable of describing incoming LAG member link of describing the incoming LAG member link SHOULD use the following
SHOULD use the following procedures, regardless of whether or not procedures, regardless of whether or not the incoming interface was a
incoming interface was a LAG interface: LAG interface:
o When the "I" flag ( "Interface and Label Stack Object Request o When the I flag (Interface and Label Stack Object Request flag) of
flag") of the DDMAP TLV in the received MPLS echo request is set: the DDMAP TLV in the received MPLS echo request is set:
* The responder LSR MUST add the Detailed Interface and Label * The responder LSR MUST add the Detailed Interface and Label
Stack TLV (described in Section 10) in the MPLS echo reply. Stack TLV (described in Section 10) in the MPLS echo reply.
* If the incoming interface is a LAG, the responder LSR MUST add * If the incoming interface is a LAG, the responder LSR MUST add
the Incoming Interface Index Sub-TLV (described in the Incoming Interface Index Sub-TLV (described in
Section 10.1.2) in the Detailed Interface and Label Stack TLV. Section 10.1.2) in the Detailed Interface and Label Stack TLV.
The "LAG Member Link Indicator flag" MUST be set in the The LAG Member Link Indicator flag MUST be set in the Interface
Interface Index Flags field, and the Interface Index field set Index Flags field, and the Interface Index field set to the LAG
to the LAG member link which received the MPLS echo request. member link that received the MPLS echo request.
These procedures allow initiator LSR to:
o Utilize the Incoming Interface Index Sub-TLV in the Detailed These procedures allow the initiator LSR to utilize the Incoming
Interface and Label Stack TLV to derive, if the incoming interface Interface Index Sub-TLV in the Detailed Interface and the Label Stack
is a LAG, the identity of the incoming LAG member. TLV to derive, if the incoming interface is a LAG, the identity of
the incoming LAG member.
5.1.3. Additional Initiator LSR Procedures 5.1.3. Additional Initiator LSR Procedures
Along with procedures described in Section 4, the procedures Along with procedures described in Section 4, the procedures
described in this section will allow an initiator LSR to know: described in this section will allow an initiator LSR to know:
o The expected load balance information of every LAG member link, at o The expected load-balance information of every LAG member link, at
LSR with TTL=n. LSR with TTL=n.
o With specific entropy, the expected interface index of the o With specific entropy, the expected interface index of the
outgoing LAG member link at TTL=n. outgoing LAG member link at TTL=n.
o With specific entropy, the interface index of the incoming LAG o With specific entropy, the interface index of the incoming LAG
member link at TTL=n+1. member link at TTL=n+1.
Depending on the LAG traffic division algorithm, the messages may or Depending on the LAG traffic division algorithm, the messages may or
may not traverse different member links. The expectation is that may not traverse different member links. The expectation is that
there's a relationship between the interface index of the outgoing there's a relationship between the interface index of the outgoing
LAG member link at TTL=n and the interface index of the incoming LAG LAG member link at TTL=n and the interface index of the incoming LAG
member link at TTL=n+1 for all entropies examined. In other words, member link at TTL=n+1 for all entropies examined. In other words,
set of entropies that load balances to outgoing LAG member link X at the messages with a set of entropies that load-balances to outgoing
TTL=n should all reach the nexthop on same incoming LAG member link Y LAG member link X at TTL=n should all reach the next hop on the same
at TTL=n+1. incoming LAG member link Y at TTL=n+1.
With additional logic, the initiator LSR can perform the following With additional logic, the initiator LSR can perform the following
checks in a scenario where the initiator LSR knows that there is a checks in a scenario where it (a) knows that there is a LAG that has
LAG, with two LAG members, between TTL=n and TTL=n+1, and has the two LAG members, between TTL=n and TTL=n+1, and (b) has the multipath
multipath information to traverse the two LAG member links. information to traverse the two LAG member links.
The initiator LSR sends two MPLS echo request messages to traverse The initiator LSR sends two MPLS echo request messages to traverse
the two LAG member links at TTL=n+1: the two LAG member links at TTL=n+1:
o Success case: o Success case:
* One MPLS echo request message reaches TTL=n+1 on an LAG member * One MPLS echo request message reaches TTL=n+1 on LAG member
link 1. link 1.
* The other MPLS echo request message reaches TTL=n+1 on an LAG * The other MPLS echo request message reaches TTL=n+1 on LAG
member link 2. member link 2.
The two MPLS echo request messages sent by the initiator LSR reach The two MPLS echo request messages sent by the initiator LSR reach
at the immediate downstream LSR from two different LAG member the immediate downstream LSR from two different LAG member links.
links.
o Error case: o Error case:
* One MPLS echo request message reaches TTL=n+1 on an LAG member * One MPLS echo request message reaches TTL=n+1 on LAG member
link 1. link 1.
* The other MPLS echo request message also reaches TTL=n+1 on an * The other MPLS echo request message also reaches TTL=n+1 on LAG
LAG member link 1. member link 1.
* One or both MPLS echo request messages cannot reach the * One or both MPLS echo request messages cannot reach the
immediate downstream LSR on whichever link. immediate downstream LSR on whichever link.
One or two MPLS echo request messages sent by the initiator LSR One or two MPLS echo request messages sent by the initiator LSR
cannot reach the immediate downstream LSR, or the two MPLS echo cannot reach the immediate downstream LSR, or the two MPLS echo
request messages reach at the immediate downstream LSR from the request messages reach at the immediate downstream LSR from the
same LAG member link. same LAG member link.
Note that the above defined procedures will provide a deterministic Note that the procedures defined above will provide a deterministic
result for LAG interfaces that are back-to-back connected between result for LAG interfaces that are back-to-back connected between
LSRs (i.e. no L2 switch in between). If there is a L2 switch between LSRs (i.e., no L2 switch in between). If there is an L2 switch
the LSR at TTL=n and the LSR at TTL=n+1, there is no guarantee that between the LSR at TTL=n and the LSR at TTL=n+1, there is no
traversal of every LAG member link at TTL=n will result in reaching guarantee that every incoming interface at TTL=n+1 can be traversed,
from different interface at TTL=n+1. Issues resulting from LAG with even when traversing every outgoing LAG member link at TTL=n. Issues
L2 switch in between are further described in Appendix A. LAG resulting from LAG with an L2 switch in between are further described
provisioning models in operated network should be considered when in Appendix A. LAG provisioning models in operator networks should
analyzing the output of LSP Traceroute exercising L2 ECMPs. be considered when analyzing the output of LSP Traceroute that is
exercising L2 ECMPs.
5.2. Individual End-to-End Path Verification 5.2. Individual End-to-End Path Verification
When the Remote Interface Index Sub-TLVs are available from an LSR When the Remote Interface Index Sub-TLVs are available from an LSR
with TTL=n, then the validation of LAG member link traversal can be with TTL=n, then the validation of LAG member link traversal can be
performed by the downstream LSR of TTL=n+1. The initiator LSR performed by the downstream LSR of TTL=n+1. The initiator LSR
follows the procedures described in Section 4.3. follows the procedures described in Section 4.3.
The DDMAP validation procedures for the downstream responder LSR are The DDMAP validation procedures for the downstream responder LSR are
then updated to include the comparison of the incoming LAG member then updated to include the comparison of the incoming LAG member
link to the interface index described in the Remote Interface Index link to the interface index described in the Remote Interface Index
Sub-TLV in the DDMAP TLV. Failure of this comparison results in the Sub-TLV in the DDMAP TLV. Failure of this comparison results in the
return code being set to "Downstream Mapping Mismatch (5)". return code being set to "Downstream Mapping Mismatch (5)".
6. LSR Capability TLV 6. LSR Capability TLV
This document defines a new TLV which is referred to as the "LSR This document defines a new TLV that is referred to as the LSR
Capability TLV. It MAY be included in the MPLS echo request message Capability TLV. It MAY be included in the MPLS echo request message
and the MPLS echo reply message. An MPLS echo request message and an and the MPLS echo reply message. An MPLS echo request message and an
MPLS echo reply message MUST NOT include more than one LSR Capability MPLS echo reply message MUST NOT include more than one LSR Capability
TLV. The presence of an LSR Capability TLV in an MPLS echo request TLV. The presence of an LSR Capability TLV in an MPLS echo request
message is a request that a responder LSR includes an LSR Capability message is a request that a responder LSR includes an LSR Capability
TLV in the MPLS echo reply message, with the LSR Capability TLV TLV in the MPLS echo reply message, with the LSR Capability TLV
describing features and extensions that the responder LSR supports. describing features and extensions that the responder LSR supports.
The format of the LSR Capability TLV is as below: The format of the LSR Capability TLV is as below:
LSR Capability TLV Type is TBD1. Length is 4. The value field of LSR Capability TLV Type is 4. Length is 4. The LSR Capability TLV
the LSR Capability TLV has following format: has the following format:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSR Capability Flags | | LSR Capability Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: LSR Capability TLV Figure 4: LSR Capability TLV
Where: Where:
The Type field is 2 octets in length and the value is TBD1. The Type field is 2 octets in length, and the value is 4.
The Length field is 2 octets in length, and the value is 4. The Length field is 2 octets in length, and the value is 4.
The "LSR Capability Flags" field is 4 octets in length, this The LSR Capability Flags field is 4 octets in length; this
document defines the following flags: document defines the following flags:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Must Be Zero) |U|D| | Reserved (Must Be Zero) |U|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This document defines two flags. The unallocated flags MUST be This document defines two flags. The unallocated flags MUST be
set to zero when sending and ignored on receipt. Both the U and set to zero when sending and ignored on receipt. Both the U and
the D flag MUST be cleared in the MPLS echo request message when the D flag MUST be cleared in the MPLS echo request message when
sending, and ignored on receipt. Neither, either or both the U sending and ignored on receipt. Zero, one, or both of the flags
and the D flag MAY be set in the MPLS echo reply message. (U and D) MAY be set in the MPLS echo reply message.
Flag Name and Meaning Flag Name and Meaning
---- ---------------- ---- ----------------
U Upstream LAG Info Accommodation U Upstream LAG Info Accommodation
An LSR sets this flag when the LSR is capable of An LSR sets this flag when the LSR is capable of describing
describing a LAG member link in the Incoming Interface a LAG member link in the Incoming Interface Index Sub-TLV
Index Sub-TLV in the Detailed Interface and in the Detailed Interface and Label Stack TLV.
Label Stack TLV.
D Downstream LAG Info Accommodation D Downstream LAG Info Accommodation
An LSR sets this flag when the LSR is capable of An LSR sets this flag when the LSR is capable of describing
describing LAG member links in the Local Interface LAG member links in the Local Interface Index Sub-TLV and
Index Sub-TLV and the Multipath Data Sub-TLV in the the Multipath Data Sub-TLV in the Downstream Detailed
Downstream Detailed Mapping TLV. Mapping TLV.
7. LAG Description Indicator Flag: G 7. LAG Description Indicator Flag: G
This document defines a new flag, the "G" flag (LAG Description This document defines a new flag, the G flag (LAG Description
Indicator), in the DS Flags field of the DDMAP TLV. Indicator), in the DS Flags field of the DDMAP TLV.
The "G" flag in the MPLS echo request message indicates the request The G flag in the MPLS echo request message indicates the request for
for detailed LAG information from the responder LSR. In the MPLS detailed LAG information from the responder LSR. In the MPLS echo
echo reply message, the "G" flag MUST be set if the DDMAP TLV reply message, the G flag MUST be set if the DDMAP TLV describes a
describes a LAG interface. It MUST be cleared otherwise. LAG interface. It MUST be cleared otherwise.
The "G" flag is defined as below: The G flag is defined as below:
The Bit Number is TBD5. The Bit Number is 3.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| MBZ |G|E|L|I|N| | MBZ |G|E|L|I|N|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
RFC-Editor-Note: Please update above figure to place the G flag in
the bit number TBD5.
Flag Name and Meaning Flag Name and Meaning
---- ---------------- ---- ----------------
G LAG Description Indicator G LAG Description Indicator
When this flag is set in the MPLS echo request, the responder LSR When this flag is set in the MPLS echo request, the responder
is requested to respond with detailed LAG information. When this LSR is requested to respond with detailed LAG information.
flag is set in the MPLS echo reply, the corresponding DDMAP TLV When this flag is set in the MPLS echo reply, the corresponding
describes a LAG interface. DDMAP TLV describes a LAG interface.
8. Local Interface Index Sub-TLV 8. Local Interface Index Sub-TLV
The Local Interface Index Sub-TLV describes the interface index The Local Interface Index Sub-TLV describes the interface index
assigned by the local LSR to an egress interface. One or more Local assigned by the local LSR to an egress interface. One or more Local
Interface Index sub-TLVs MAY appear in a DDMAP TLV. Interface Index sub-TLVs MAY appear in a DDMAP TLV.
The format of the Local Interface Index Sub-TLV is below: The format of the Local Interface Index Sub-TLV is below:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface Index | | Local Interface Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Local Interface Index Sub-TLV Figure 5: Local Interface Index Sub-TLV
Where: Where:
o The "Type" field is 2 octets in length, the value is TBD2. o The Type field is 2 octets in length, and the value is 4.
o The "Length" filed 2 octets in length, and the value is 4. o The Length field is 2 octets in length, and the value is 4.
o The "Local Interface Index" field is 4 octets in length, it is an o The Local Interface Index field is 4 octets in length; it is an
interface index assigned by a local LSR to an egress interface. interface index assigned by a local LSR to an egress interface.
It's normally an unsigned integer and in network byte order. It's normally an unsigned integer and in network byte order.
9. Remote Interface Index Sub-TLV 9. Remote Interface Index Sub-TLV
The Remote Interface Index Sub-TLV is an optional TLV, it describes The Remote Interface Index Sub-TLV is an optional TLV; it describes
the interface index assigned by a downstream LSR to an ingress the interface index assigned by a downstream LSR to an ingress
interface. One or more Remote Interface Index sub-TLVs MAY appear in interface. One or more Remote Interface Index sub-TLVs MAY appear in
a DDMAP TLV. a DDMAP TLV.
The format of the Remote Interface Index Sub-TLV is as below: The format of the Remote Interface Index Sub-TLV is below:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface Index | | Remote Interface Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Remote Interface Index Sub-TLV Figure 6: Remote Interface Index Sub-TLV
Where: Where:
o The "Type" field is 2 octets in length, and the value is TBD3. o The Type field is 2 octets in length, and the value is 5.
o The "Length" field is 2 octets in length, and the value is 4. o The Length field is 2 octets in length, and the value is 4.
o The "Remote Interface Index" is 4 octets in length, it is an o The Remote Interface Index field is 4 octets in length; it is an
interface index assigned by a downstream LSR to an ingress interface index assigned by a downstream LSR to an ingress
interface. It's normally an unsigned integer and in network byte interface. It's normally an unsigned integer and in network byte
order. order.
10. Detailed Interface and Label Stack TLV 10. Detailed Interface and Label Stack TLV
The "Detailed Interface and Label Stack" object is a TLV that MAY be The Detailed Interface and Label Stack TLV MAY be included in an MPLS
included in an MPLS echo reply message to report the interface on echo reply message to report the interface on which the MPLS echo
which the MPLS echo request message was received and the label stack request message was received and the label stack that was on the
that was on the packet when it was received. A responder LSR MUST packet when it was received. A responder LSR MUST NOT insert more
NOT insert more than one instance of this TLV into the MPLS echo than one instance of this TLV into the MPLS echo reply message. This
reply message. This TLV allows the initiator LSR to obtain the exact TLV allows the initiator LSR to obtain the exact interface and label
interface and label stack information as it appears at the responder stack information as it appears at the responder LSR.
LSR.
Detailed Interface and Label Stack TLV Type is TBD4. Length is K + Detailed Interface and Label Stack TLV Type is 6. Length is K + Sub-
Sub-TLV Length (sum of Sub-TLVs). K is the sum of all fields of this TLV Length (sum of Sub-TLVs). K is the sum of all fields of this TLV
TLV prior to Sub-TLVs, but the length of K depends on the Address prior to the list of Sub-TLVs, but the length of K depends on the
Type. Details of this information is described below. The Value Address Type. Details of this information is described below. The
field has following format: Detailed Interface and Label Stack TLV has the following format:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | Reserved (Must Be Zero) | | Address Type | Reserved (Must Be Zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address (4 or 16 octets) | | IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface (4 or 16 octets) | | Interface (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . .
. List of Sub-TLVs . . List of Sub-TLVs .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Detailed Interface and Label Stack TLV Figure 7: Detailed Interface and Label Stack TLV
The Detailed Interface and Label Stack TLV format is derived from the The Detailed Interface and Label Stack TLV format is derived from the
Interface and Label Stack TLV format (from [RFC8029]). Two changes Interface and Label Stack TLV format (from [RFC8029]). Two changes
are introduced. The first is that the label stack is converted into are introduced. The first is that the label stack is converted into
a sub-TLV. The second is that a new sub-TLV is added to describe an a sub-TLV. The second is that a new sub-TLV is added to describe an
interface index. The other fields of Detailed Interface and Label interface index. The other fields of the Detailed Interface and
Stack TLV have the same use and meaning as in [RFC8029]. A summary Label Stack TLV have the same use and meaning as in [RFC8029]. A
of these fields is as below: summary of these fields is as below:
Address Type Address Type
The Address Type indicates if the interface is numbered or The Address Type indicates if the interface is numbered or
unnumbered. It also determines the length of the IP Address unnumbered. It also determines the length of the IP Address
and Interface fields. The resulting total length of the and Interface fields. The resulting total length of the
initial part of the TLV is listed as "K Octets". The Address initial part of the TLV is listed as "K Octets". The Address
Type is set to one of the following values: Type is set to one of the following values:
Type # Address Type K Octets Type # Address Type K Octets
skipping to change at page 19, line 14 skipping to change at page 19, line 14
Numbered or IPv6 Numbered, the IP Address MUST be set to either Numbered or IPv6 Numbered, the IP Address MUST be set to either
the LSR's Router ID or the interface address, and the Interface the LSR's Router ID or the interface address, and the Interface
MUST be set to the interface address. MUST be set to the interface address.
If the interface is unnumbered, the Address Type MUST be either If the interface is unnumbered, the Address Type MUST be either
IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the
LSR's Router ID, and the Interface MUST be set to the index LSR's Router ID, and the Interface MUST be set to the index
assigned to the interface. assigned to the interface.
Note: Usage of IPv6 Unnumbered has the same issue as [RFC8029], Note: Usage of IPv6 Unnumbered has the same issue as [RFC8029],
described in Section 3.4.2 of [RFC7439]. A solution should be which is described in Section 3.4.2 of [RFC7439]. A solution
considered an applied to both [RFC8029] and this document. should be considered and applied to both [RFC8029] and this
document.
10.1. Sub-TLVs 10.1. Sub-TLVs
This section defines the sub-TLVs that MAY be included as part of the This section defines the sub-TLVs that MAY be included as part of the
Detailed Interface and Label Stack TLV. Two sub-TLVs are defined: Detailed Interface and Label Stack TLV. Two sub-TLVs are defined:
Sub-Type Sub-TLV Name Sub-Type Sub-TLV Name
--------- ------------ --------- ------------
1 Incoming Label stack 1 Incoming Label Stack
2 Incoming Interface Index 2 Incoming Interface Index
10.1.1. Incoming Label Stack Sub-TLV 10.1.1. Incoming Label Stack Sub-TLV
The Incoming Label Stack sub-TLV contains the label stack as received The Incoming Label Stack Sub-TLV contains the label stack as received
by an LSR. If any TTL values have been changed by this LSR, they by an LSR. If any TTL values have been changed by this LSR, they
SHOULD be restored. SHOULD be restored.
Incoming Label Stack Sub-TLV Type is 1. Length is variable, and its Incoming Label Stack Sub-TLV Type is 1. Length is variable, and its
format is as below: format is as below:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | TC |S| TTL | | Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . . .
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | TC |S| TTL | | Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Incoming Label Stack Sub-TLV Figure 8: Incoming Label Stack Sub-TLV
10.1.2. Incoming Interface Index Sub-TLV 10.1.2. Incoming Interface Index Sub-TLV
The Incoming Interface Index object is a Sub-TLV that MAY be included The Incoming Interface Index Sub-TLV MAY be included in a Detailed
in a Detailed Interface and Label Stack TLV. The Incoming Interface Interface and Label Stack TLV. The Incoming Interface Index Sub-TLV
Index Sub-TLV describes the index assigned by a local LSR to the describes the index assigned by a local LSR to the interface that
interface which received the MPLS echo request message. received the MPLS echo request message.
Incoming Interface Index Sub-TLV Type is 2. Length is 8, and its Incoming Interface Index Sub-TLV Type is 2. Length is 8, and its
format is as below: format is as below:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface Index Flags | Reserved (Must Be Zero) | | Interface Index Flags | Reserved (Must Be Zero) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Incoming Interface Index | | Incoming Interface Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Incoming Interface Index Sub-TLV Figure 9: Incoming Interface Index Sub-TLV
Interface Index Flags Interface Index Flags
Interface Index Flags field is a bit vector with following format. The Interface Index Flags field is a bit vector with following
format.
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (Must Be Zero) |M| | Reserved (Must Be Zero) |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
One flag is defined: M. The remaining flags MUST be set to zero One flag is defined: M. The remaining flags MUST be set to zero
when sending and ignored on receipt. when sending and ignored on receipt.
Flag Name and Meaning Flag Name and Meaning
---- ---------------- ---- ----------------
M LAG Member Link Indicator M LAG Member Link Indicator
When this flag is set, interface index described in When this flag is set, the interface index described in this
this sub-TLV is a member of a LAG. sub-TLV is a member of a LAG.
Incoming Interface Index Incoming Interface Index
An Index assigned by the LSR to this interface. It's normally an An Index assigned by the LSR to this interface. It's normally an
unsigned integer and in network byte order. unsigned integer and in network byte order.
11. Rate Limiting On Echo Request/Reply Messages 11. Rate-Limiting on Echo Request/Reply Messages
For an LSP path, it may be over several LAGs. Each LAG may have many An LSP may be over several LAGs. Each LAG may have many member
member links. To exercise all the links, many Echo Request/Reply links. To exercise all the links, many echo request/reply messages
messages will be sent in a short period. It's possible that those will be sent in a short period. It's possible that those messages
messages may traverse a common path as a burst. Under some may traverse a common path as a burst. Under some circumstances,
circumstances this might cause congestion at the common path. To this might cause congestion at the common path. To avoid potential
avoid potential congestion, it is RECOMMENDED that implementations to congestion, it is RECOMMENDED that implementations randomly delay the
randomly delay the Echo Request and Reply messages at the Initiating echo request and reply messages at the initiator LSRs and responder
LSRs and Responder LSRs. Rate limiting of ping traffic is further LSRs. Rate-limiting of ping traffic is further specified in
specified in [RFC8029] (Section 5) and [RFC6425] (Section 4.1) which Section 5 of [RFC8029] and Section 4.1 of [RFC6425], which apply to
apply to this document as well. this document as well.
12. Security Considerations 12. Security Considerations
This document extends LSP Traceroute mechanism [RFC8029] to discover This document extends the LSP Traceroute mechanism [RFC8029] to
and exercise L2 ECMP paths to determine problematic member link(s) of discover and exercise L2 ECMP paths to determine problematic member
a LAG. These on-demand diagnostic mechanisms are used by an operator link(s) of a LAG. These on-demand diagnostic mechanisms are used by
within an MPLS control domain. an operator within an MPLS control domain.
[RFC8029] reviews the possible attacks and approaches to mitigate [RFC8029] reviews the possible attacks and approaches to mitigate
possible threats when using these mechanisms. possible threats when using these mechanisms.
To prevent leakage of vital information to untrusted users, a To prevent leakage of vital information to untrusted users, a
responder LSR MUST only accept MPLS echo request messages from responder LSR MUST only accept MPLS echo request messages from
designated trusted sources via filtering source IP address field of designated trusted sources via filtering the source IP address field
received MPLS echo request messages. As noted in [RFC8029], spoofing of received MPLS echo request messages. As noted in [RFC8029],
attacks only have a small window of opportunity. If these messages spoofing attacks only have a small window of opportunity. If an
are indeed hijacked (non-delivery) by an intermediate node, the use intermediate node hijacks these messages (i.e., causes non-delivery),
of these mechanisms will determine the data plane is not working (as the use of these mechanisms will determine the data plane is not
it should). Hijacking of a responder node such that it provides a working as it should. Hijacking of a responder node such that it
legitimate reply would involve compromising the node itself and the provides a legitimate reply would involve compromising the node
MPLS control domain. [RFC5920] provides additional MPLS network-wide itself and the MPLS control domain. [RFC5920] provides additional
operation recommendations to avoid attacks and recommendations to MPLS network-wide operation recommendations to avoid attacks. Please
follow. Please note that source IP address filtering provides only a note that source IP address filtering provides only a weak form of
weak form of access control and is not, in general, a reliable access control and is not, in general, a reliable security mechanism.
security mechanism. Nonetheless, it is required here in the absence Nonetheless, it is required here in the absence of any more robust
of any more robust mechanisms that might be used. mechanisms that might be used.
13. IANA Considerations 13. IANA Considerations
13.1. LSR Capability TLV 13.1. LSR Capability TLV
The IANA is requested to assign new value TBD1 (from the range IANA has assigned value 4 (from the range 0-16383) for the LSR
4-16383) for LSR Capability TLV from the "Multiprotocol Label Capability TLV from the "TLVs" registry under the "Multiprotocol
Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
Parameters - TLVs" registry. registry [IANA-MPLS-LSP-PING].
Value Meaning Reference Type TLV Name Reference
----- ------- --------- ----- -------- ---------
TBD1 LSR Capability TLV this document 4 LSR Capability RFC 8611
13.1.1. LSR Capability Flags 13.1.1. LSR Capability Flags
The IANA is requested to create and maintain a registry entitled "LSR IANA has created a new "LSR Capability Flags" registry. The initial
Capability Flags" with following registration procedures: contents are as follows:
Registry Name: LAG Interface Info Flags
Bit number Name Reference Value Meaning Reference
---------- ---------------------------------------- --------- ----- ------- ---------
31 D: Downstream LAG Info Accommodation this document 31 D: Downstream LAG Info Accommodation RFC 8611
30 U: Upstream LAG Info Accommodation this document 30 U: Upstream LAG Info Accommodation RFC 8611
0-29 Unassigned 0-29 Unassigned
Assignments of LSR Capability Flags are via Standards Action Assignments of LSR Capability Flags are via Standards Action
[RFC8126]. [RFC8126].
13.2. Local Interface Index Sub-TLV 13.2. Local Interface Index Sub-TLV
The IANA is requested to assign new value TBD2 (from the range IANA has assigned value 4 (from the range 0-16383) for the Local
4-16383) for the Local Interface Index Sub-TLV from the Interface Index Sub-TLV from the "Sub-TLVs for TLV Type 20"
"Multiprotocol Label Switching Architecture (MPLS) Label Switched subregistry of the "TLVs" registry in the "Multiprotocol Label
Paths (LSPs) Ping Parameters - TLVs" registry, "Sub-TLVs for TLV Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
Types 20" sub-registry. registry [IANA-MPLS-LSP-PING].
Value Meaning Reference Sub-Type Sub-TLV Name Reference
----- ------- --------- -------- ------------ ---------
TBD2 Local Interface Index Sub-TLV this document 4 Local Interface Index RFC 8611
13.2.1. Interface Index Flags 13.2.1. Interface Index Flags
The IANA is requested to create and maintain a registry entitled IANA has created a new "Interface Index Flags" registry. The initial
"Interface Index Flags" with following registration procedures: contents are as follows:
Registry Name: Interface Index Flags
Bit number Name Reference Bit Number Name Reference
---------- ---------------------------------------- --------- ---------- -------------------------------- ---------
15 M: LAG Member Link Indicator this document 15 M: LAG Member Link Indicator RFC 8611
0-14 Unassigned 0-14 Unassigned
Assignments of Interface Index Flags are via Standards Action Assignments of Interface Index Flags are via Standards Action
[RFC8126]. [RFC8126].
Note that this registry is used by the Interface Index Flags field of Note that this registry is used by the Interface Index Flags field of
following Sub-TLVs: the following sub-TLVs:
o The Local Interface Index Sub-TLV which may be present in the o The Local Interface Index Sub-TLV, which may be present in the
"Downstream Detailed Mapping" TLV. Downstream Detailed Mapping TLV.
o The Remote Interface Index Sub-TLV which may be present in the o The Remote Interface Index Sub-TLV, which may be present in the
"Downstream Detailed Mapping" TLV. Downstream Detailed Mapping TLV.
o The Incoming Interface Index Sub-TLV which may be present in the o The Incoming Interface Index Sub-TLV, which may be present in the
"Detailed Interface and Label Stack" TLV. Detailed Interface and Label Stack TLV.
13.3. Remote Interface Index Sub-TLV 13.3. Remote Interface Index Sub-TLV
The IANA is requested to assign new value TBD3 (from the range IANA has assigned value 5 (from the range 0-16383) for the Remote
32768-49161) for the Remote Interface Index Sub-TLV from the Interface Index Sub-TLV from the "Sub-TLVs for TLV Type 20"
"Multiprotocol Label Switching Architecture (MPLS) Label Switched subregistry of the "TLVs" registry in the "Multiprotocol Label
Paths (LSPs) Ping Parameters - TLVs" registry, "Sub-TLVs for TLV Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
Types 20" sub-registry. registry [IANA-MPLS-LSP-PING].
Value Meaning Reference Sub-Type Sub-TLV Name Reference
----- ------- --------- -------- ------------ ---------
TBD3 Remote Interface Index Sub-TLV this document 5 Remote Interface Index RFC 8611
13.4. Detailed Interface and Label Stack TLV 13.4. Detailed Interface and Label Stack TLV
The IANA is requested to assign new value TBD4 (from the range IANA has assigned value 6 (from the range 0-16383) for the Detailed
4-16383) for Detailed Interface and Label Stack TLV from the Interface and Label Stack TLV from the "TLVs" registry in the
"Multiprotocol Label Switching Architecture (MPLS) Label Switched "Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs)
Paths (LSPs) Ping Parameters - TLVs" registry ([IANA-MPLS-LSP-PING]). Ping Parameters" registry [IANA-MPLS-LSP-PING].
Value Meaning Reference Type TLV Name Reference
----- ------- --------- ----- -------- ---------
TBD4 Detailed Interface and Label Stack TLV this document 6 Detailed Interface and Label Stack RFC 8611
13.4.1. Sub-TLVs for TLV Type TBD4 13.4.1. Sub-TLVs for TLV Type 6
The IANA is requested to create and maintain a sub-registry entitled RFC 8029 changed the registration procedures for TLV and sub-TLV
"Sub-TLVs for TLV Type TBD4" under "Multiprotocol Label Switching registries for LSP Ping.
Architecture (MPLS) Label Switched Paths (LSPs) Ping Parameters -
TLVs" registry.
Initial values for this sub-registry, "Sub-TLVs for TLV Types TBD4", IANA has created a new "Sub-TLVs for TLV Type 6" subregistry under
are described below. the "TLVs" registry of the "Multiprotocol Label Switching (MPLS)
Label Switched Paths (LSPs) Ping Parameters" registry
[IANA-MPLS-LSP-PING].
Sub-Type Name Reference This registry conforms with RFC 8029.
----------- -------------------------------------- ---------
1 Incoming Label Stack this document
2 Incoming Interface Index this document
3-16383 Unassigned (mandatory TLVs)
16384-31743 Specification Required
32768-49161 Unassigned (optional TLVs)
49162-64511 Specification Required
Assignments of Sub-Types in the mandatory and optional spaces are via The registration procedures for this sub-TLV registry are:
Standards Action [RFC8126]. Assignments of Sub-Types in the
Specification Required space is via Specification Required [RFC8126].
13.4.2. Interface and Label Stack Address Types Range Registration Procedure Note
----- ---------------------- -----
0-16383 Standards Action This range is for mandatory
TLVs or for optional TLVs that
require an error message if
not recognized.
16384-31743 RFC Required This range is for mandatory
TLVs or for optional TLVs that
require an error message if
not recognized.
31744-32767 Private Use Not to be assigned
32768-49161 Standards Action This range is for optional TLVs
that can be silently dropped if
not recognized.
49162-64511 RFC Required This range is for optional TLVs
that can be silently dropped if
not recognized.
64512-65535 Private Use Not to be assigned
Since the "Detailed Interface and Label Stack TLV" shares the The initial allocations for this registry are:
"Interface and Label Stack Address Types" with the "Interface and
Label Stack TLV". IANA is requested to update the "Interface and
Label Stack Address Types" registry to reflect this.
For example, change the registry name to "Interface and Label Stack Sub-Type Sub-TLV Name Reference Comment
and Detailed Interface and Label Stack Address Types", and add a -------- ------------ --------- -------
reference to this document. 0 Reserved RFC 8611
1 Incoming Label Stack RFC 8611
2 Incoming Interface Index RFC 8611
3-31743 Unassigned
31744-32767 RFC 8611 Reserved for
Private Use
32768-64511 Unassigned
64512-65535 RFC 8611 Reserved for
Private Use
13.5. DS Flags Note: IETF does not prescribe how the Private Use sub-TLVs are
handled; however, if a packet containing a sub-TLV from a Private Use
ranges is received by an LSR that does not recognize the sub-TLV, an
error message MAY be returned if the sub-TLV is from the range
31744-32767, and the packet SHOULD be silently dropped if it is from
the range 64511-65535.
The IANA is requested to assign a new bit number from the "DS flags" 13.4.2. Interface and Label Stack Address Types
sub-registry from the "Multi-Protocol Label Switching (MPLS) Label
Switched Paths (LSPs) Ping Parameters - TLVs" registry
([IANA-MPLS-LSP-PING]).
Note: the "DS flags" sub-registry is created by [RFC8029]. The Detailed Interface and Label Stack TLV shares the Interface and
Label Stack Address Types with the Interface and Label Stack TLV. To
reflect this, IANA has updated the name of the registry from
"Interface and Label Stack Address Types" to "Interface and Label
Stack and Detailed Interface and Label Stack Address Types".
Bit number Name Reference 13.5. DS Flags
---------- ---------------------------------------- ---------
TBD5 G: LAG Description Indicator this document
14. Acknowledgements IANA has assigned a new bit number from the "DS Flags" subregistry of
the "Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs)
Ping Parameters" registry [IANA-MPLS-LSP-PING].
The authors would like to thank Nagendra Kumar, Sam Aldrin, for Note: the "DS Flags" subregistry was created by [RFC8029].
providing useful comments and suggestions. The authors would like to
thank Loa Andersson for performing a detailed review and providing
number of comments.
The authors also would like to extend sincere thanks to the MPLS RT Bit number Name Reference
review members who took time to review and provide comments. The ---------- ---------------------------------------- ---------
members are Eric Osborne, Mach Chen and Yimin Shen. The suggestion 3 G: LAG Description Indicator RFC 8611
by Mach Chen to generalize and create the LSR Capability TLV was
tremendously helpful for this document and likely for future
documents extending the MPLS LSP Ping and Traceroute mechanisms. The
suggestion by Yimin Shen to create two separate validation procedures
had a big impact to the contents of this document.
15. References 14. References
15.1. Normative References 14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029, Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017, DOI 10.17487/RFC8029, March 2017,
skipping to change at page 25, line 33 skipping to change at page 26, line 5
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
15.2. Informative References 14.2. Informative References
[IANA-MPLS-LSP-PING] [IANA-MPLS-LSP-PING]
IANA, "Multi-Protocol Label Switching (MPLS) Label IANA, "Multiprotocol Label Switching (MPLS) Label Switched
Switched Paths (LSPs) Ping Parameters", Paths (LSPs) Ping Parameters",
<http://www.iana.org/assignments/mpls-lsp-ping-parameters/ <https://www.iana.org/assignments/
mpls-lsp-ping-parameters.xhtml>. mpls-lsp-ping-parameters/>.
[IEEE802.1AX] [IEEE802.1AX]
IEEE Std. 802.1AX, "IEEE Standard for Local and IEEE, "IEEE Standard for Local and metropolitan area
metropolitan area networks - Link Aggregation", November networks - Link Aggregation", IEEE Std. 802.1AX.
2008.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>. <https://www.rfc-editor.org/info/rfc5920>.
[RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A., [RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
Yasukawa, S., and T. Nadeau, "Detecting Data-Plane Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
Failures in Point-to-Multipoint MPLS - Extensions to LSP Failures in Point-to-Multipoint MPLS - Extensions to LSP
Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011, Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011,
<https://www.rfc-editor.org/info/rfc6425>. <https://www.rfc-editor.org/info/rfc6425>.
[RFC7439] George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for [RFC7439] George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for
Operating IPv6-Only MPLS Networks", RFC 7439, Operating IPv6-Only MPLS Networks", RFC 7439,
DOI 10.17487/RFC7439, January 2015, DOI 10.17487/RFC7439, January 2015,
<https://www.rfc-editor.org/info/rfc7439>. <https://www.rfc-editor.org/info/rfc7439>.
Appendix A. LAG with intermediate L2 Switch Issues Appendix A. LAG with Intermediate L2 Switch Issues
Several flavors of "LAG with L2 switch" provisioning models and the Several flavors of provisioning models that use a "LAG with L2
corresponding MPLS data plane ECMP traversal validation issues are switch" and the corresponding MPLS data-plane ECMP traversal
described in this section . validation issues are described in this appendix.
A.1. Equal Numbers of LAG Members A.1. Equal Numbers of LAG Members
R1 ==== S1 ==== R2 R1 ==== S1 ==== R2
The issue with this LAG provisioning model is that packets traversing The issue with this LAG provisioning model is that packets traversing
a LAG member from Router 1 (R1) to intermediate L2 switch (S1) can a LAG member from Router 1 (R1) to intermediate L2 switch (S1) can
get load balanced by S1 towards Router 2 (R2). Therefore, MPLS echo get load-balanced by S1 towards Router 2 (R2). Therefore, MPLS echo
request messages traversing a specific LAG member from R1 to S1 can request messages traversing a specific LAG member from R1 to S1 can
actually reach R2 via any of the LAG members, and the sender of MPLS actually reach R2 via any of the LAG members, and the sender of the
echo request messages has no knowledge of this nor no way to control MPLS echo request messages has no knowledge of this nor any way to
this traversal. In the worst case, MPLS echo request messages with control this traversal. In the worst case, MPLS echo request
specific entropies to exercise every LAG members from R1 to S1 can messages with specific entropies will exercise every LAG member link
all reach R2 via same LAG member. Thus it is impossible for MPLS from R1 to S1 and can all reach R2 via the same LAG member link.
echo request sender to verify that packets intended to traverse Thus, it is impossible for the MPLS echo request sender to verify
specific LAG member from R1 to S1 did actually traverse that LAG that packets intended to traverse a specific LAG member link from R1
member, and to deterministically exercise "receive" processing of to S1 did actually traverse that LAG member link and to
every LAG member on R2. (Notes, AFAICT there's not a better option deterministically exercise "receive" processing of every LAG member
than "try a bunch of entropy labels and see what responses you can link on R2. (Note: As far as we can tell, there's not a better
get back" and that's the same remedy in all the described option than "try a bunch of entropy labels and see what responses you
can get back", and that's the same remedy in all the described
topologies.) topologies.)
A.2. Deviating Numbers of LAG Members A.2. Deviating Numbers of LAG Members
____ ____
R1 ==== S1 ==== R2 R1 ==== S1 ==== R2
There are deviating number of LAG members on the two sides of the L2 There are deviating numbers of LAG members on the two sides of the L2
switch. The issue with this LAG provisioning model is the same as switch. The issue with this LAG provisioning model is the same as
previous model, sender of MPLS echo request messages have no with the previous model: the sender of MPLS echo request messages has
knowledge of L2 load balance algorithm nor entropy values to control no knowledge of the L2 load-balancing algorithm nor entropy values to
the traversal. control the traversal.
A.3. LAG Only on Right A.3. LAG Only on Right
R1 ---- S1 ==== R2 R1 ---- S1 ==== R2
The issue with this LAG provisioning model is that there is no way The issue with this LAG provisioning model is that there is no way
for MPLS echo request sender to deterministically exercise both LAG for an MPLS echo request sender to deterministically exercise both
members from S1 to R2. And without such, "receive" processing of R2 LAG member links from S1 to R2. And without such, "receive"
on each LAG member cannot be verified. processing of R2 on each LAG member cannot be verified.
A.4. LAG Only on Left A.4. LAG Only on Left
R1 ==== S1 ---- R2 R1 ==== S1 ---- R2
MPLS echo request sender has knowledge of how to traverse both LAG The MPLS echo request sender has knowledge of how to traverse both
members from R1 to S1. However, both types of packets will terminate LAG members from R1 to S1. However, both types of packets will
on the non-LAG interface at R2. It becomes impossible for MPLS echo terminate on the non-LAG interface at R2. It becomes impossible for
request sender to know that MPLS echo request messages intended to the MPLS echo request sender to know that MPLS echo request messages
traverse a specific LAG member from R1 to S1 did indeed traverse that intended to traverse a specific LAG member from R1 to S1 did indeed
LAG member. traverse that LAG member.
Acknowledgements
The authors would like to thank Nagendra Kumar and Sam Aldrin for
providing useful comments and suggestions. The authors would like to
thank Loa Andersson for performing a detailed review and providing a
number of comments.
The authors also would like to extend sincere thanks to the MPLS RT
review members who took the time to review and provide comments. The
members are Eric Osborne, Mach Chen, and Yimin Shen. The suggestion
by Mach Chen to generalize and create the LSR Capability TLV was
tremendously helpful for this document and likely for future
documents extending the MPLS LSP Ping and Traceroute mechanisms. The
suggestion by Yimin Shen to create two separate validation procedures
had a big impact on the contents of this document.
Authors' Addresses Authors' Addresses
Nobo Akiya Nobo Akiya
Big Switch Networks Big Switch Networks
Email: nobo.akiya.dev@gmail.com Email: nobo.akiya.dev@gmail.com
George Swallow George Swallow
Cisco Systems Southend Technical Center
Email: swallow@cisco.com Email: swallow.ietf@gmail.com
Stephane Litkowski Stephane Litkowski
Orange Orange
Email: stephane.litkowski@orange.com Email: stephane.litkowski@orange.com
Bruno Decraene Bruno Decraene
Orange Orange
Email: bruno.decraene@orange.com Email: bruno.decraene@orange.com
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