draft-ietf-mpls-entropy-lsp-ping-04.txt   draft-ietf-mpls-entropy-lsp-ping-05.txt 
MPLS Working Group N. Akiya MPLS Working Group N. Akiya
Internet-Draft Big Switch Networks Internet-Draft Big Switch Networks
Updates: 4379, 6424, 6790 (if approved) G. Swallow Updates: 6790 (if approved) G. Swallow
Intended status: Standards Track C. Pignataro Intended status: Standards Track C. Pignataro
Expires: February 12, 2017 Cisco Expires: March 9, 2017 Cisco
A. Malis A. Malis
Huawei Technologies Huawei Technologies
S. Aldrin S. Aldrin
Google Google
August 11, 2016 September 5, 2016
Label Switched Path (LSP) and Pseudowire (PW) Ping/Trace over Label Switched Path (LSP) and Pseudowire (PW) Ping/Trace over
MPLS Network using Entropy Labels (EL) MPLS Network using Entropy Labels (EL)
draft-ietf-mpls-entropy-lsp-ping-04 draft-ietf-mpls-entropy-lsp-ping-05
Abstract Abstract
Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Ping Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Ping
and Traceroute are methods used to test Equal-Cost Multipath (ECMP) and Traceroute are methods used to test Equal-Cost Multipath (ECMP)
paths. Ping is known as a connectivity verification method and paths. Ping is known as a connectivity verification method and
Traceroute as a fault isolation method, as described in RFC 4379. Traceroute as a fault isolation method, as described in RFC 4379.
When an LSP is signaled using the Entropy Label (EL) described in RFC When an LSP is signaled using the Entropy Label (EL) described in RFC
6790, the ability for LSP Ping and Traceroute operations to discover 6790, the ability for LSP Ping and Traceroute operations to discover
and exercise ECMP paths is lost for scenarios where LSRs apply and exercise ECMP paths is lost for scenarios where Label Switching
different load balancing techniques. One such scenario is when some Routers (LSRs) apply different load balancing techniques. One such
LSRs apply EL-based load balancing while other LSRs apply non-EL scenario is when some LSRs apply EL-based load balancing while other
based load balancing (e.g., IP). Another scenario is when an EL- LSRs apply non-EL-based load balancing (e.g., IP). Another scenario
based LSP is stitched with another LSP which can be EL-based or non- is when an EL-based LSP is stitched with another LSP which can be EL-
EL based. based or non-EL-based.
This document extends the MPLS LSP Ping and Traceroute multipath This document extends the MPLS LSP Ping and Traceroute multipath
mechanisms in RFC 6424 to allow the ability of exercising LSPs which mechanisms in RFC 6424 to allow the ability of exercising LSPs which
make use of the EL. This document updates RFC 4379, RFC 6424, and make use of the EL. This document updates RFC 6790.
RFC 6790.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 12, 2017. This Internet-Draft will expire on March 9, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Multipath Type 9 . . . . . . . . . . . . . . . . . . . . . . 7 3. Multipath Type 9 . . . . . . . . . . . . . . . . . . . . . . 7
4. Pseudowire Tracing . . . . . . . . . . . . . . . . . . . . . 7 4. Pseudowire Tracing . . . . . . . . . . . . . . . . . . . . . 7
5. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 8 5. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 8
6. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 9 6. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 9
7. New Multipath Information Type: TBD4 . . . . . . . . . . . . 10 7. New Multipath Information Type: TBD4 . . . . . . . . . . . . 10
8. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 11 8. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 11
9. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 13 9. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 13
9.1. IP Based Load Balancer & Not Pushing ELI/EL . . . . . . . 14 9.1. IP-based Load Balancer & Not Pushing ELI/EL . . . . . . . 14
9.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 14 9.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 14
9.3. Label Based Load Balancer & Not Pushing ELI/EL . . . . . 15 9.3. Label-based Load Balancer & Not Pushing ELI/EL . . . . . 15
9.4. Label Based Load Balancer & Pushes ELI/EL . . . . . . . . 16 9.4. Label-based Load Balancer & Pushes ELI/EL . . . . . . . . 16
9.5. Flow-Aware MS-PW Stitching LSR . . . . . . . . . . . . . 17 9.5. Flow-Aware MS-PW Stitching LSR . . . . . . . . . . . . . 17
10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 17 10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 17
11. Security Considerations . . . . . . . . . . . . . . . . . . . 19 11. Security Considerations . . . . . . . . . . . . . . . . . . . 19
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12.1. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19 12.1. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19
12.2. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19 12.2. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19
12.3. Multipath Type . . . . . . . . . . . . . . . . . . . . . 20 12.3. Multipath Type . . . . . . . . . . . . . . . . . . . . . 20
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
14. Contributing Authors . . . . . . . . . . . . . . . . . . . . 20 14. Contributing Authors . . . . . . . . . . . . . . . . . . . . 20
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction 1. Introduction
1.1. Terminology 1.1. Terminology
The following acronyms and terms are used in this document: The following acronyms and 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 Stitched LSP - Stitched Label Switched Paths combine several LSPs
such that a single end-to-end (e2e) LSP is realized. [RFC6424]
describes LSP Ping for Stitched LSPs.
o LSR - Label Switching Router. o LSR - Label Switching Router.
o FEC - Forwarding Equivalent Class. o FEC - Forwarding Equivalence Class.
o ECMP - Equal-Cost Multipath. o ECMP - Equal-Cost Multipath.
o EL - Entropy Label. o EL - Entropy Label.
o ELI - Entropy Label Indicator. o ELI - Entropy Label Indicator.
o GAL - Generic Associated Channel Label. o GAL - Generic Associated Channel Label.
o MS-PW - Multi-Segment Pseudowire. o MS-PW - Multi-Segment Pseudowire.
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MPLS implementations employ a wide variety of load balancing MPLS implementations employ a wide variety of load balancing
techniques in terms of fields used for hash "keys". The mechanisms techniques in terms of fields used for hash "keys". The mechanisms
in [RFC4379] and updated by [RFC6424] are designed to provide in [RFC4379] and updated by [RFC6424] are designed to provide
multipath support for a subset of techniques. The intent of this multipath support for a subset of techniques. The intent of this
document is to provide multipath support for the supported techniques document is to provide multipath support for the supported techniques
which are compromised by the use of ELs [RFC6790]. Section 10 which are compromised by the use of ELs [RFC6790]. Section 10
describes supported and unsupported cases, and it may be useful for describes supported and unsupported cases, and it may be useful for
the reader to first review this section. the reader to first review this section.
The Downstream Detailed Mapping (DDMAP) TLV [RFC6424] provides The Downstream Detailed Mapping (DDMAP) TLV [RFC6424] provides
multipath information which can be used by an LSP Ping initiator to Multipath Information which can be used by an LSP Ping initiator to
trace and validate ECMP paths between an ingress and egress. The trace and validate ECMP paths between an ingress and egress. The
multipath information encodings defined by [RFC6424] are sufficient Multipath Information encodings defined by [RFC6424] are sufficient
when all the LSRs along the path(s), between ingress and egress, when all the LSRs along the path(s), between ingress and egress,
consider the same set of "keys" as input for load balancing consider the same set of "keys" as input for load balancing
algorithms, e.g. either all IP-based or all label-based. algorithms, e.g., either all IP-based or all label-based.
With the introduction of [RFC6790], some LSRs may perform load With the introduction of [RFC6790], some LSRs may perform load
balancing based on labels while others may be IP-based. This results balancing based on labels while others may be IP-based. This results
in an LSP Ping initiator to not be able to trace and validate all the in an LSP Ping initiator that is unable to trace and validate all the
ECMP paths in the following scenarios: ECMP paths in the following scenarios:
o One or more transit LSRs along an LSP with ELI/EL in label stack o One or more transit LSRs along an LSP with ELI/EL in the label
do not perform ECMP load balancing based on EL (hashes based on stack do not perform ECMP load balancing based on EL (hashes based
"keys" including the IP destination address). This scenario is on "keys" including the IP destination address). This scenario is
not only possible but quite common due to transit LSRs not not only possible but quite common due to transit LSRs not
implementing [RFC6790] or transit LSRs implementing [RFC6790], but implementing [RFC6790] or transit LSRs implementing [RFC6790], but
not implementing the suggested transit LSR behavior in Section 4.3 not implementing the suggested transit LSR behavior in Section 4.3
of [RFC6790]. of [RFC6790].
o Two or more LSPs stitched together with at least one of these LSPs o Two or more LSPs stitched together with at least one of these LSPs
pushing ELI/EL into the label stack. pushing ELI/EL into the label stack.
These scenarios can be quite common because deployments of [RFC6790] These scenarios can be quite common because deployments of [RFC6790]
typically have a mixture of nodes that support ELI/EL and nodes that typically have a mixture of nodes that support ELI/EL and nodes that
do not. There will also typically be a mixture of areas that support do not. There will also typically be a mixture of areas that support
ELI/EL and areas that do not. ELI/EL and areas that do not.
As pointed out in [RFC6790], the procedures of [RFC4379] (and As pointed out in [RFC6790], the procedures of [RFC4379] (and
consequently of [RFC6424]) with respect to multipath information type consequently of [RFC6424]) with respect to Multipath Information Type
{9} are incomplete. However, [RFC6790] does not actually update {9} are incomplete. However, [RFC6790] does not actually update
[RFC4379]. Further, the specific EL location is not clearly defined, [RFC4379]. Further, the specific EL location is not clearly defined,
particularly in the case of Flow Aware Pseudowires [RFC6391]. This particularly in the case of Flow Aware Pseudowires [RFC6391]. This
document defines a new FEC Stack sub-TLV for the entropy label. document defines a new FEC Stack sub-TLV for the entropy label.
Section 3 of this document updates the procedures for multipath Section 3 of this document updates the procedures for Multipath
information type {9} described in [RFC4379] and applicable to Information Type {9} described in [RFC4379] and applicable to
[RFC6424]. The rest of this document describes extensions required [RFC6424]. The rest of this document describes extensions required
to restore ECMP discovery and tracing capabilities for the scenarios to restore ECMP discovery and tracing capabilities for the scenarios
described. described.
[RFC4379], [RFC6424], and this document will support IP-based load [RFC4379], [RFC6424], and this document will support IP-based load
balancers and label-based load balancers which limit their hash to balancers and label-based load balancers which limit their hash to
the first (top-most) or only entropy label in the label stack. Other the first (top-most) or only entropy label in the label stack. Other
use cases (refer to Section 10) are out of scope. use cases (refer to Section 10) are out of scope.
2. Overview 2. Overview
[RFC4379] describes LSP traceroute as an operation where the [RFC4379] describes LSP traceroute as an operation where the
initiating LSR sends a series of MPLS echo requests towards the same initiating LSR sends a series of MPLS echo requests towards the same
destination. The first packet in the series has the TTL set to 1. destination. The first packet in the series has the TTL set to 1.
When the echo reply is received from the LSR one hop away, the second When the echo reply is received from the LSR one hop away, the second
echo request in the series is sent with the TTL set to 2. For each echo request in the series is sent with the TTL set to 2. For each
additional echo request the TLL is incremented by one until a additional echo request the TLL is incremented by one until a
response is received from the intended destination. The initiating response is received from the intended destination. The initiating
LSR discovers and exercises ECMP by obtaining multipath information LSR discovers and exercises ECMP by obtaining Multipath Information
from each transit LSR and using a specific destination IP address or from each transit LSR and using a specific destination IP address or
specific entropy label. specific entropy label.
From here on, the notation {x, y, z} refers to multipath information From here on, the notation {x, y, z} refers to Multipath Information
types x, y or z. Multipath information types are defined in Types x, y, or z. Multipath Information Types are defined in
Section 3.3 of [RFC4379]. Section 3.3 of [RFC4379].
The LSR initiating LSP Ping sends an MPLS echo request with multipath The LSR initiating LSP Ping sends an MPLS echo request with Multipath
information. This multipath information is described in the echo Information. This Multipath Information is described in the echo
request's DDMAP TLV, and may contain a set of IP addresses or a set request's DDMAP TLV, and may contain a set of IP addresses or a set
of labels. Multipath information types {2, 4, 8} carry a set of IP of labels. Multipath Information Types {2, 4, 8} carry a set of IP
addresses, and multipath information type {9} carries a set of addresses, and Multipath Information Type {9} carries a set of
labels. The responder LSR (the receiver of the MPLS echo request) labels. The responder LSR (the receiver of the MPLS echo request)
will determine the subset of initiator-specified multipath will determine the subset of initiator-specified Multipath
information which load balances to each downstream (outgoing Information which load balances to each downstream (outgoing)
interface). The responder LSR sends an MPLS echo reply with interface. The responder LSR sends an MPLS echo reply with resulting
resulting multipath information per downstream (outgoing interface) Multipath Information per downstream (outgoing interface) back to the
back to the initiating LSR. The initiating LSR is then able to use a initiating LSR. The initiating LSR is then able to use a specific IP
specific IP destination address or a specific label to exercise a destination address or a specific label to exercise a specific ECMP
specific ECMP path on the responder LSR. path on the responder LSR.
Current behavior is problematic in following scenarios: The current behavior is problematic in the following scenarios:
o The initiating LSR sends IP multipath information, but the o The initiating LSR sends IP Multipath Information, but the
responder LSR load balances on labels. responder LSR load balances on labels.
o The initiating LSR sends label multipath information, but the o The initiating LSR sends Label Multipath Information, but the
responder LSR load balances on IP addresses. responder LSR load balances on IP addresses.
o The initiating LSR sends existing multipath information to an LSR o The initiating LSR sends existing Multipath Information to an LSR
which pushes ELI/EL in the label stack, but the initiating LSR can which pushes ELI/EL in the label stack, but the initiating LSR can
only continue to discover and exercise specific paths of the ECMP, only continue to discover and exercise specific paths of the ECMP,
if the LSR which pushes ELI/EL responds with both IP addresses and if the LSR which pushes ELI/EL responds with both IP addresses and
the associated EL corresponding to each IP address. This is the associated EL corresponding to each IP address. This is
because: because:
* An ELI/EL pushing LSR that is a stitching point will load * An ELI/EL-pushing LSR that is a stitching point will load
balance based on the IP address. balance based on the IP address.
* Downstream LSR(s) of an ELI/EL pushing LSR may load balance * Downstream LSR(s) of an ELI/EL-pushing LSR may load balance
based on ELs. based on ELs.
o The initiating LSR sends existing multipath information to an ELI/ o The initiating LSR sends existing Multipath Information to an ELI/
EL pushing LSR, but the initiating LSR can only continue to EL-pushing LSR, but the initiating LSR can only continue to
discover and exercise specific paths of ECMP, if the ELI/EL discover and exercise specific paths of ECMP, if the ELI/EL-
pushing LSR responds with both labels and associated EL pushing LSR responds with both labels and the associated EL
corresponding to the label. This is because: corresponding to the label. This is because:
* An ELI/EL pushing LSR that is a stitching point will load * An ELI/EL-pushing LSR that is a stitching point will load
balance based on EL from the previous LSP and pushes a new EL. balance based on the EL from the previous LSP and pushes a new
EL.
* Downstream LSR(s) of ELI/EL pushing LSR may load balance based * Downstream LSR(s) of ELI/EL-pushing LSR may load balance based
on new ELs. on new ELs.
The above scenarios demonstrate the existing multipath information is The above scenarios demonstrate the existing Multipath Information is
insufficient when LSP traceroute is used on an LSP with entropy insufficient when LSP traceroute is used on an LSP with entropy
labels [RFC6790]. This document defines a new multipath information labels [RFC6790]. This document defines a new Multipath Information
type to be used in the DDMAP of MPLS echo request/reply packets for Type to be used in the DDMAP of MPLS echo request/reply packets for
[RFC6790] LSPs. [RFC6790] LSPs.
The responder LSR can reply with empty multipath information if no IP The responder LSR can reply with empty Multipath Information if no IP
address is set or label set is received with the multipath address is set or label set is received with the Multipath
information. An empty return is also possible if an initiating LSR Information. An empty return is also possible if an initiating LSR
sends multipath information of one type, IP address or label, but the sends Multipath Information of one type, IP Address or Label, but the
responder LSR load balances on the other type. To disambiguate responder LSR load balances on the other type. To disambiguate
between the two results, this document introduces new flags in the between the two results, this document introduces new flags in the
DDMAP TLV to allow the responder LSR to describe the load balancing DDMAP TLV to allow the responder LSR to describe the load balancing
technique being used. technique being used.
All LSRs along the LSP need to be able to understand the new flags To use this enhanced method end-to-end, all LSRs along the LSP need
and the new multipath information type. It is also required that the to be able to understand the new flags and the new Multipath
initiating LSR can select both the IP destination address and label Information Type. Mechanisms to verify this condition are outside of
to use when transmitting MPLS echo request packets. Two additional the scope of this document. The rest of the requirements are
DS Flags are defined for the DDMAP TLV in Section 6. These two flags detailed in the initiating LSR and responder LSR procedures. Two
are used by the responder LSR to describe its load balance behavior additional DS Flags are defined for the DDMAP TLV in Section 6.
on a received MPLS echo request. These two flags are used by the responder LSR to describe its load
balance behavior on a received MPLS echo request.
Note that the terms "IP-Based Load Balancer" and "Label-Based Load Note that the terms "IP-Based Load Balancer" and "Label-Based Load
Balancer" are in context of how a received MPLS echo request is Balancer" are in context of how a received MPLS echo request is
handled by the responder LSR. handled by the responder LSR.
3. Multipath Type 9 3. Multipath Type 9
[RFC4379] defined multipath type {9} for tracing of LSPs where label [RFC4379] defined Multipath Type {9} for tracing of LSPs where label-
based load balancing is used. However, as pointed out in [RFC6790], based load balancing is used. However, as pointed out in [RFC6790],
the procedures for using this type are incomplete as the specific the procedures for using this type are incomplete as the specific
location of the label was not defined. It was assumed that the location of the label was not defined. It was assumed that the
presence of multipath type {9} implied the value of the bottom-of- presence of Multipath Type {9} implied the value of the bottom-of-
stack label should be varied by the values indicated by multipath to stack label should be varied by the values indicated by multipath to
determine the respective outgoing interfaces. determine the respective outgoing interfaces.
Section 5 defines a new FEC-Stack sub-TLV to indicate an entropy Section 5 defines a new FEC-Stack sub-TLV to indicate an entropy
label. These labels MAY appear anywhere in a label stack. label. These labels MAY appear anywhere in a label stack.
Multipath type {9} applies to the first label in the label stack that Multipath Type {9} applies to the first label in the label stack that
corresponds to an EL-FEC. If no such label is found, it applies to corresponds to an EL-FEC. If no such label is found, it applies to
the label at the bottom of the label stack. the label at the bottom of the label stack.
4. Pseudowire Tracing 4. Pseudowire Tracing
This section defines procedures for tracing pseudowires. These This section defines procedures for tracing pseudowires. These
procedures pertain to the use of multipath information type {9} as procedures pertain to the use of Multipath Information Type {9} as
well as type {TBD4}. In all cases below, when a control word is in well as Type {TBD4}. In all cases below, when a control word is in
use, the N-flag in the DDMAP MUST be set. Note that when a control use, the N-flag in the DDMAP MUST be set. Note that when a control
word is not in use, the returned DDMAPs may not be accurate. word is not in use, the returned DDMAPs may not be accurate.
In order to trace a non-flow-aware Pseudowire, the initiator includes In order to trace a non-flow-aware Pseudowire, the initiator includes
an EL-FEC instead of the appropriate PW-FEC at the bottom of the FEC an EL-FEC instead of the appropriate PW FEC at the bottom of the FEC
stack. Tracing in this way will cause compliant routers to return stack. Tracing in this way will cause compliant routers to return
the proper outgoing interface. Note that this procedure only traces the proper outgoing interface. Note that this procedure only traces
to the end of the MPLS LSP that is under test and will not verify the to the end of the MPLS LSP that is under test and will not verify the
PW FEC. To actually verify the PW FEC or in the case of a MS-PW, to PW FEC. To actually verify the PW FEC or in the case of a MS-PW, to
determine the next pseudowire label value, the initiator MUST repeat determine the next pseudowire label value, the initiator MUST repeat
that step of the trace (i.e., repeating the TTL value used) but with that step of the trace (i.e., repeating the TTL value used) but with
the FEC Stack modified to contain the appropriate PW FEC. Note that the FEC Stack modified to contain the appropriate PW FEC. Note that
these procedures are applicable to scenarios where an initiator is these procedures are applicable to scenarios where an initiator is
able to vary the bottom label (i.e., Pseudowire label). Possible able to vary the bottom label (i.e., Pseudowire label). Possible
scenarios are tracing multiple non-flow-aware Pseudowires on the same scenarios are tracing multiple non-flow-aware Pseudowires on the same
endpoints or tracing a non-flow-aware Pseudowire provisioned with endpoints or tracing a non-flow-aware Pseudowire provisioned with
multiple Pseudowire labels. multiple Pseudowire labels.
In order to trace a flow-aware Pseudowire [RFC6391], the initiator In order to trace a flow-aware Pseudowire [RFC6391], the initiator
includes an EL FEC at the bottom of the FEC Stack and pushes the includes an EL FEC at the bottom of the FEC Stack and pushes the
appropriate PW FEC onto the FEC Stack. appropriate PW FEC onto the FEC Stack.
In order to trace through non-compliant routers, the initiator forms In order to trace through non-compliant routers, the initiator forms
an MPLS echo request message and includes a DDMAP with multipath type an MPLS echo request message and includes a DDMAP with Multipath Type
{9}. For a non-flow-aware Pseudowire it includes the appropriate PW {9}. For a non-flow-aware Pseudowire it includes the appropriate PW
FEC in the FEC Stack. For a flow-aware Pseudowire, the initiator FEC in the FEC Stack. For a flow-aware Pseudowire, the initiator
includes a Nil FEC at the bottom of the FEC Stack and pushes the includes a Nil FEC at the bottom of the FEC Stack and pushes the
appropriate PW FEC onto the FEC Stack. appropriate PW FEC onto the FEC Stack.
5. Entropy Label FEC 5. Entropy Label FEC
The entropy label indicator (ELI) is a reserved label that has no The entropy label indicator (ELI) is a reserved label that has no
explicit FEC associated, and has label value 7 assigned from the explicit FEC associated, and has label value 7 assigned from the
reserved range. Use the Nil FEC as the Target FEC Stack sub-TLV to reserved range. Use the Nil FEC as the Target FEC Stack sub-TLV to
skipping to change at page 9, line 26 skipping to change at page 9, line 26
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| MBZ |L|E|I|N| | MBZ |L|E|I|N|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
RFC-Editor-Note: Please update the above figure to place the flag E RFC-Editor-Note: Please update the above figure to place the flag E
in the bit number TBD2 and the flag L in the bit number TBD3. in the bit number TBD2 and the flag L in the bit number TBD3.
Flag Name and Meaning Flag Name and Meaning
---- ---------------- ---- ----------------
L Label-based load balance indicator L Label-based load balance indicator
This flag MUST be set to zero in the echo request. An LSR This flag MUST be cleared in the echo request. An LSR
which performs load balancing on a label MUST set this which performs load balancing on a label MUST set this
flag in the echo reply. An LSR which performs load flag in the echo reply. An LSR which performs load
balancing on IP MUST NOT set this flag in the echo balancing on IP MUST NOT set this flag in the echo
reply. reply.
E ELI/EL push indicator E ELI/EL push indicator
This flag MUST be set to zero in the echo request. An LSR This flag MUST be cleared in the echo request. An LSR
which pushes ELI/EL MUST set this flag in the echo which pushes ELI/EL MUST set this flag in the echo
reply. An LSR which does not push ELI/EL MUST NOT set reply. An LSR which does not push ELI/EL MUST NOT set
this flag in the echo reply. this flag in the echo reply.
The two flags result in four load balancing techniques which the echo The two flags result in four load balancing techniques which the echo
reply generating LSR can indicate: reply generating LSR can indicate:
o {L=0, E=0} LSR load balances based on IP and does not push ELI/EL. o {L=0, E=0} LSR load balances based on IP and does not push ELI/EL.
o {L=0, E=1} LSR load balances based on IP and pushes ELI/EL. o {L=0, E=1} LSR load balances based on IP and pushes ELI/EL.
o {L=1, E=0} LSR load balances based on labels and does not push o {L=1, E=0} LSR load balances based on labels and does not push
ELI/EL. ELI/EL.
o {L=1, E=1} LSR load balances based on labels and pushes ELI/EL. o {L=1, E=1} LSR load balances based on labels and pushes ELI/EL.
7. New Multipath Information Type: TBD4 7. New Multipath Information Type: TBD4
One new multipath information type is added to be used in DDMAP TLV. One new Multipath Information Type is added to be used in DDMAP TLV.
This new multipath type has the value of TBD4. This new Multipath Type has the value of TBD4.
Key Type Multipath Information Key Type Multipath Information
--- ---------------- --------------------- --- ---------------- ---------------------
TBD4 IP and label set IP addresses and label prefixes TBD4 IP and Label set IP addresses and label prefixes
Multipath type TBD4 is comprised of three sections. The first Multipath Type TBD4 is comprised of three sections. The first
section describes the IP address set. The second section describes section describes the IP address set. The second section describes
the label set. The third section describes another label set which the label set. The third section describes another label set which
associates to either the IP address set or the label set specified in associates to either the IP address set or the label set specified in
the other sections. the other sections.
Multipath information type TBD4 has following format: Multipath Information Type TBD4 has 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPMultipathType| IP Multipath Length | Reserved(MBZ) | |IPMultipathType| IP Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~ ~ ~
| (IP Multipath Information) | | (IP Multipath Information) |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 10, line 49 skipping to change at page 10, line 49
~ ~ ~ ~
| (Associated Label Multipath Information) | | (Associated Label Multipath Information) |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Multipath Information Type TBD4 Figure 2: Multipath Information Type TBD4
o IPMultipathType o IPMultipathType
* 0 when "IP Multipath Information" is omitted. Otherwise, one * 0 when "IP Multipath Information" is omitted. Otherwise, one
of the IP multipath information values: {2, 4, 8}. of the IP Multipath Information values: {2, 4, 8}.
o IP Multipath Information o IP Multipath Information
* This section is omitted when "IPMultipathType" is 0. * This section is omitted when "IPMultipathType" is 0.
Otherwise, this section reuses IP multipath information from Otherwise, this section reuses IP Multipath Information from
[RFC4379]. Specifically, multipath information for values {2, [RFC4379]. Specifically, Multipath Information for values {2,
4, 8} can be used. 4, 8} can be used.
o LbMultipathType o LbMultipathType
* 0 when "Label Multipath Information" is omitted. Otherwise, * 0 when "Label Multipath Information" is omitted. Otherwise,
label multipath information value {9}. Label Multipath Information value {9}.
o Label Multipath Information o Label Multipath Information
* This section is omitted when "LbMultipathType" is 0. * This section is omitted when "LbMultipathType" is 0.
Otherwise, this section reuses label multipath information from Otherwise, this section reuses Label Multipath Information from
[RFC4379]. Specifically, multipath information for value {9} [RFC4379]. Specifically, Multipath Information for value {9}
can be used. can be used.
o Associated Label Multipath Information o Associated Label Multipath Information
* "Assoc Label Multipath Length" is a 16 bit field of multipath * "Assoc Label Multipath Length" is a 16-bit field of Multipath
information which indicates the length in octets of the Information which indicates the length in octets of the
associated label multipath information. Associated Label Multipath Information.
* "Associated Label Multipath Information" is a list of labels * "Associated Label Multipath Information" is a list of labels
with each label described in 24 bits. This section MUST be with each label described in 24 bits. This section MUST be
omitted in an MPLS echo request message. A midpoint which omitted in an MPLS echo request message. A midpoint which
pushes ELI/EL labels SHOULD include "Assoc Label Multipath pushes ELI/EL labels SHOULD include "Assoc Label Multipath
Information" in its MPLS echo reply message, along with either Information" in its MPLS echo reply message, along with either
"IP Multipath Information" or "Label Multipath Information". "IP Multipath Information" or "Label Multipath Information".
Each specified associated label described in this section maps Each specified associated label described in this section maps
to a specific IP address OR label described in the "IP to a specific IP address OR label described in the "IP
Multipath Information" section or "Label Multipath Information" Multipath Information" section or "Label Multipath Information"
section. For example, if three IP addresses are specified in section. For example, if three IP addresses are specified in
the "IP Multipath Information" section, then there MUST be the "IP Multipath Information" section, then there MUST be
three labels described in this section. The first label maps three labels described in this section. The first label maps
to the first IP address specified, the second label maps to the to the first IP address specified, the second label maps to the
second IP address specified, and the third label maps to the second IP address specified, and the third label maps to the
third IP address specified. third IP address specified.
When a section is omitted, the length for that section MUST BE set to When a section is omitted, the length for that section MUST be set to
zero. zero.
8. Initiating LSR Procedures 8. Initiating LSR Procedures
The following procedure is described in terms of an EL_LSP boolean The following procedure is described in terms of an EL_LSP boolean
maintained by the initiating LSR. This value controls the multipath maintained by the initiating LSR. This value controls the Multipath
information type to be used in the transmitted echo request packets. Information Type to be used in the transmitted echo request packets.
When the initiating LSR is transmitting an echo request packet with When the initiating LSR is transmitting an echo request packet with
DDMAP with a non-zero multipath information type, then the EL_LSP DDMAP with a non-zero Multipath Information Type, then the EL_LSP
boolean MUST be consulted to determine the multipath information type boolean MUST be consulted to determine the Multipath Information Type
to use. to use.
In addition to procedures described in [RFC4379], as updated by In addition to procedures described in [RFC4379], as updated by
Section 3 and [RFC6424], the initiating LSR MUST operate with the Section 3 and [RFC6424], the initiating LSR MUST operate with the
following procedures: following procedures:
o When the initiating LSR pushes ELI/EL, initialize EL_LSP=True. o When the initiating LSR pushes ELI/EL, initialize EL_LSP=True.
Else set EL_LSP=False. Else set EL_LSP=False.
o When the initiating LSR is transmitting a non-zero multipath o When the initiating LSR is transmitting a non-zero Multipath
information type: Information Type:
* If (EL_LSP), the initiating LSR MUST use multipath information * If (EL_LSP), the initiating LSR MUST use Multipath Information
type {TBD4} unless the responder LSR cannot handle type {TBD4}. Type {TBD4} unless the responder LSR cannot handle Type {TBD4}.
When the initiating LSR is transmitting multipath information When the initiating LSR is transmitting Multipath Information
type {TBD4}, both "IP Multipath Information" and "Label Type {TBD4}, both "IP Multipath Information" and "Label
Multipath Information" MUST be included, and "IP Associated Multipath Information" MUST be included, and "Associated Label
Label Multipath Information" MUST be omitted (NULL). Multipath Information" MUST be omitted (NULL).
* Else the initiating LSR MAY use multipath information type {2, * Else the initiating LSR MAY use Multipath Information Type {2,
4, 8, 9, TBD4}. When the initiating LSR is transmitting 4, 8, 9, TBD4}. When the initiating LSR is transmitting
multipath information type {TBD4} in this case, "IP Multipath Multipath Information Type {TBD4} in this case, "IP Multipath
Information" MUST be included, and "Label Multipath Information" MUST be included, and "Label Multipath
Information" and "IP Associated Label Multipath Information" Information" and "Associated Label Multipath Information" MUST
MUST be omitted (NULL). be omitted (NULL).
o When the initiating LSR receives echo reply with {L=0, E=1} in DS o When the initiating LSR receives an echo reply with {L=0, E=1} in
flags with valid contents, set EL_LSP=True. the DS flags with valid contents, set EL_LSP=True.
In the following conditions, the initiating LSR may have lost the In the following conditions, the initiating LSR may have lost the
ability to exercise specific ECMP paths. The initiating LSR MAY ability to exercise specific ECMP paths. The initiating LSR MAY
continue with "best effort" in the following cases: continue with "best effort" in the following cases:
o Received echo reply contains empty multipath information. o Received echo reply contains empty Multipath Information.
o Received echo reply contains {L=0, E=<any>} DS flags, but does not o Received echo reply contains {L=0, E=<any>} DS flags, but does not
contain IP multipath information. contain IP Multipath Information.
o Received echo reply contains {L=1, E=<any>} DS flags, but does not o Received echo reply contains {L=1, E=<any>} DS flags, but does not
contain label multipath information. contain Label Multipath Information.
o Received echo reply contains {L=<any>, E=1} DS flags, but does not o Received echo reply contains {L=<any>, E=1} DS flags, but does not
contain associated label multipath information. contain Associated Label Multipath Information.
o IP multipath information types {2, 4, 8} sent, and received echo o IP Multipath Information Types {2, 4, 8} sent, and received echo
reply with {L=1, E=0} in DS flags. reply with {L=1, E=0} in DS flags.
o Multipath information type {TBD4} sent, and received echo reply o Multipath Information Type {TBD4} sent, and received echo reply
with multipath information type other than {TBD4}. with Multipath Information Type other than {TBD4}.
9. Responder LSR Procedures 9. Responder LSR Procedures
Common Procedures: Common Procedures:
o The responder LSR receiving an MPLS echo request packet MUST first o The responder LSR receiving an MPLS echo request packet MUST first
determine whether or not the initiating LSR supports this LSP Ping determine whether or not the initiating LSR supports this LSP Ping
and Traceroute extension for Entropy Labels. If either of the and Traceroute extension for Entropy Labels. If either of the
following conditions are met, the responder LSR SHOULD determine following conditions are met, the responder LSR SHOULD determine
that the initiating LSR supports this LSP Ping and Traceroute that the initiating LSR supports this LSP Ping and Traceroute
extension for entropy labels. extension for entropy labels.
1. Received MPLS echo request contains the multipath information 1. Received MPLS echo request contains the Multipath Information
type {TBD4}. Type {TBD4}.
2. Received MPLS echo request contains a Target FEC Stack TLV 2. Received MPLS echo request contains a Target FEC Stack TLV
that includes the entropy label FEC. that includes the entropy label FEC.
If the initiating LSR is determined to not support this LSP Ping If the initiating LSR is determined not to support this LSP Ping
and Traceroute extension for entropy labels, then the responder and Traceroute extension for entropy labels, then the responder
LSR MUST NOT follow further procedures described in this section. LSR MUST NOT follow further procedures described in this section.
Specifically, MPLS echo reply packets: Specifically, MPLS echo reply packets:
* MUST have following DS Flags cleared (i.e., not set): "ELI/EL * MUST have the following DS Flags cleared (i.e., not set): "ELI/
push indicator" and "Label-based load balance indicator". EL push indicator" and "Label-based load balance indicator".
* MUST NOT use multipath information type {TBD4}. * MUST NOT use Multipath Information Type {TBD4}.
o The responder LSR receiving an MPLS echo request packet with o The responder LSR receiving an MPLS echo request packet with
multipath information type {TBD4} MUST validate the following Multipath Information Type {TBD4} MUST validate the following
contents. Any deviation MUST result in the responder LSR to contents. Any deviation MUST result in the responder LSR
consider the packet as malformed and return code 1 ("Malformed considering the packet as malformed and returning code 1
echo request received") in the MPLS echo reply packet. ("Malformed echo request received") in the MPLS echo reply packet.
* IP multipath information MUST be included. * IP Multipath Information MUST be included.
* Label multipath information MAY be included. * Label Multipath Information MAY be included.
* IP associated label multipath information MUST be omitted * Associated Label Multipath Information MUST be omitted (NULL).
(NULL).
The following subsections describe expected responder LSR procedures The following subsections describe expected responder LSR procedures
when the echo reply is to include DDMAP TLVs, based on the local load when the echo reply is to include DDMAP TLVs, based on the local load
balance technique being employed. In case the responder LSR performs balance technique being employed. In case the responder LSR performs
deviating load balance techniques on a per downstream basis, deviating load balance techniques on a per downstream basis,
appropriate procedures matched to each downstream load balance appropriate procedures matched to each downstream load balance
technique MUST be followed. technique MUST be followed.
9.1. IP Based Load Balancer & Not Pushing ELI/EL 9.1. IP-based Load Balancer & Not Pushing ELI/EL
o The responder MUST set {L=0, E=0} in DS flags. o The responder MUST set {L=0, E=0} in DS flags.
o If multipath information type {2, 4, 8} is received, the responder o If Multipath Information Type {2, 4, 8} is received, the responder
MUST comply with [RFC4379] and [RFC6424]. MUST comply with [RFC4379] and [RFC6424].
o If multipath information type {9} is received, the responder MUST o If Multipath Information Type {9} is received, the responder MUST
reply with multipath type {0}. reply with Multipath Type {0}.
o If multipath information type {TBD4} is received, the following o If Multipath Information Type {TBD4} is received, the following
procedures are to be used: procedures are to be used:
* The responder MUST reply with multipath information type * The responder MUST reply with Multipath Information Type
{TBD4}. {TBD4}.
* The "Label Multipath Information" and "Associated Label * The "Label Multipath Information" and "Associated Label
Multipath Information" sections MUST be omitted (NULL). Multipath Information" sections MUST be omitted (NULL).
* If no matching IP address is found, then the "IPMultipathType" * If no matching IP address is found, then the "IPMultipathType"
field MUST be set to multipath information type {0} and the "IP field MUST be set to Multipath Information Type {0} and the "IP
Multipath Information" section MUST also be omitted (NULL). Multipath Information" section MUST also be omitted (NULL).
* If at least one matching IP address is found, then the * If at least one matching IP address is found, then the
"IPMultipathType" field MUST be set to appropriate multipath "IPMultipathType" field MUST be set to appropriate Multipath
information type {2, 4, 8} and the "IP Multipath Information" Information Type {2, 4, 8} and the "IP Multipath Information"
section MUST be included. section MUST be included.
9.2. IP Based Load Balancer & Pushes ELI/EL 9.2. IP Based Load Balancer & Pushes ELI/EL
o The responder MUST set {L=0, E=1} in DS flags. o The responder MUST set {L=0, E=1} in DS flags.
o If multipath information type {9} is received, the responder MUST o If Multipath Information Type {9} is received, the responder MUST
reply with multipath type {0}. reply with Multipath Type {0}.
o If multipath type {2, 4, 8, TBD4} is received, the following o If Multipath Type {2, 4, 8, TBD4} is received, the following
procedures are to be used: procedures are to be used:
* The responder MUST respond with multipath type {TBD4}. See * The responder MUST respond with Multipath Type {TBD4}. See
Section 7 for details of multipath type {TBD4}. Section 7 for details of Multipath Type {TBD4}.
* The "Label Multipath Information" section MUST be omitted * The "Label Multipath Information" section MUST be omitted
(i.e., it is not there). (i.e., it is not there).
* The IP address set specified in the received IP multipath * The IP address set specified in the received IP Multipath
information MUST be used to determine the returning IP/Label Information MUST be used to determine the returned IP/Label
pairs. pairs.
* If the received multipath information type was {TBD4}, the * If the received Multipath Information Type was {TBD4}, the
received "Label Multipath Information" sections MUST NOT be received "Label Multipath Information" sections MUST NOT be
used to determine the associated label portion of returning IP/ used to determine the associated label portion of the returned
Label pairs. IP/Label pairs.
* If no matching IP address is found, then the "IPMultipathType" * If no matching IP address is found, then the "IPMultipathType"
field MUST be set to multipath information type {0} and the "IP field MUST be set to Multipath Information Type {0} and the "IP
Multipath Information" section MUST be omitted. In addition, Multipath Information" section MUST be omitted. In addition,
the "Assoc Label Multipath Length" MUST be set to 0, and the the "Assoc Label Multipath Length" MUST be set to 0, and the
"Associated Label Multipath Information" section MUST also be "Associated Label Multipath Information" section MUST also be
omitted. omitted.
* If at least one matching IP address is found, then the * If at least one matching IP address is found, then the
"IPMultipathType" field MUST be set to appropriate multipath "IPMultipathType" field MUST be set to appropriate Multipath
information type {2, 4, 8} and the "IP Multipath Information" Information Type {2, 4, 8} and the "IP Multipath Information"
section MUST be included. In addition, the "Associated Label section MUST be included. In addition, the "Associated Label
Multipath Information" section MUST be populated with a list of Multipath Information" section MUST be populated with a list of
labels corresponding to each IP address specified in the "IP labels corresponding to each IP address specified in the "IP
Multipath Information" section. "Assoc Label Multipath Length" Multipath Information" section. "Assoc Label Multipath Length"
MUST be set to a value representing the length in octets of the MUST be set to a value representing the length in octets of the
"Associated Label Multipath Information" field. "Associated Label Multipath Information" field.
9.3. Label Based Load Balancer & Not Pushing ELI/EL 9.3. Label-based Load Balancer & Not Pushing ELI/EL
o The responder MUST set {L=1, E=0} in DS flags. o The responder MUST set {L=1, E=0} in DS flags.
o If multipath information type {2, 4, 8} is received, the responder o If Multipath Information Type {2, 4, 8} is received, the responder
MUST reply with multipath type {0}. MUST reply with Multipath Type {0}.
o If multipath information type {9} is received, the responder MUST o If Multipath Information Type {9} is received, the responder MUST
comply with [RFC4379] and [RFC6424] as updated by Section 3. comply with [RFC4379] and [RFC6424] as updated by Section 3.
o If multipath information type {TBD4} is received, the following o If Multipath Information Type {TBD4} is received, the following
procedures are to be used: procedures are to be used:
* The responder MUST reply with multipath information type * The responder MUST reply with Multipath Information Type
{TBD4}. {TBD4}.
* The "IP Multipath Information" and "Associated Label Multipath * The "IP Multipath Information" and "Associated Label Multipath
Information" sections MUST be omitted (NULL). Information" sections MUST be omitted (NULL).
* If no matching label is found, then the "LbMultipathType" field * If no matching label is found, then the "LbMultipathType" field
MUST be set to multipath information type {0} and the "Label MUST be set to Multipath Information Type {0} and the "Label
Multipath Information" section MUST also be omitted (NULL). Multipath Information" section MUST also be omitted (NULL).
* If at least one matching label is found, then the * If at least one matching label is found, then the
"LbMultipathType" field MUST be set to the appropriate "LbMultipathType" field MUST be set to the appropriate
multipath information type {9} and the "Label Multipath Multipath Information Type {9} and the "Label Multipath
Information" section MUST be included. Information" section MUST be included.
9.4. Label Based Load Balancer & Pushes ELI/EL 9.4. Label-based Load Balancer & Pushes ELI/EL
o The responder MUST set {L=1, E=1} in DS flags. o The responder MUST set {L=1, E=1} in DS flags.
o If multipath information type {2, 4, 8} is received, the responder o If Multipath Information Type {2, 4, 8} is received, the responder
MUST reply with multipath type {0}. MUST reply with Multipath Type {0}.
o If multipath type {9, TBD4} is received, the following procedures o If Multipath Type {9, TBD4} is received, the following procedures
are to be used: are to be used:
* The responder MUST respond with multipath type {TBD4}. * The responder MUST respond with Multipath Type {TBD4}.
* The "IP Multipath Information" section MUST be omitted. * The "IP Multipath Information" section MUST be omitted.
* The label set specified in the received label multipath * The label set specified in the received Label Multipath
information MUST be used to determine the returning Label/Label Information MUST be used to determine the returned Label/Label
pairs. pairs.
* If received multipath information type was {TBD4}, received * If received Multipath Information Type was {TBD4}, received
"Label Multipath Information" sections MUST NOT be used to "Label Multipath Information" sections MUST NOT be used to
determine the associated label portion of returning Label/Label determine the associated label portion of the returned Label/
pairs. Label pairs.
* If no matching label is found, then the "LbMultipathType" field * If no matching label is found, then the "LbMultipathType" field
MUST be set to multipath information type {0} and "Label MUST be set to Multipath Information Type {0} and "Label
Multipath Information" section MUST be omitted. In addition, Multipath Information" section MUST be omitted. In addition,
"Assoc Label Multipath Length" MUST be set to 0, and the "Assoc Label Multipath Length" MUST be set to 0, and the
"Associated Label Multipath Information" section MUST also be "Associated Label Multipath Information" section MUST also be
omitted. omitted.
* If at least one matching label is found, then the * If at least one matching label is found, then the
"LbMultipathType" field MUST be set to the appropriate "LbMultipathType" field MUST be set to the appropriate
multipath information type {9} and the "Label Multipath Multipath Information Type {9} and the "Label Multipath
Information" section MUST be included. In addition, the Information" section MUST be included. In addition, the
"Associated Label Multipath Information" section MUST be "Associated Label Multipath Information" section MUST be
populated with a list of labels corresponding to each label populated with a list of labels corresponding to each label
specified in the "Label Multipath Information" section. "Assoc specified in the "Label Multipath Information" section. "Assoc
Label Multipath Length" MUST be set to a value representing the Label Multipath Length" MUST be set to a value representing the
length in octets of the "Associated Label Multipath length in octets of the "Associated Label Multipath
Information" field. Information" field.
9.5. Flow-Aware MS-PW Stitching LSR 9.5. Flow-Aware MS-PW Stitching LSR
skipping to change at page 17, line 22 skipping to change at page 17, line 22
described in Section 9.3. described in Section 9.3.
o Load balances on the previous flow label, and replaces the flow o Load balances on the previous flow label, and replaces the flow
label with a newly computed label. For this case, the stitching label with a newly computed label. For this case, the stitching
LSR is to behave as described in Section 9.4. LSR is to behave as described in Section 9.4.
10. Supported and Unsupported Cases 10. Supported and Unsupported Cases
The MPLS architecture does not define strict rules on how The MPLS architecture does not define strict rules on how
implementations are to identify hash "keys" for load balancing implementations are to identify hash "keys" for load balancing
purpose. As a result, implementations may be of the following load purposes. As a result, implementations may be of the following load
balancer types: balancer types:
1. IP-based load balancer. 1. IP-based load balancer.
2. Label-based load balancer. 2. Label-based load balancer.
3. Label- and IP-based load balancer. 3. Label- and IP-based load balancer.
For cases (2) and (3), an implementation can include different sets For cases (2) and (3), an implementation can include different sets
of labels from the label stack for load balancing purpose. Thus the of labels from the label stack for load balancing purpose. Thus the
following sub-cases are possible: following sub-cases are possible:
a. Entire label stack. a. Entire label stack.
b. Top N labels from label stack where the number of labels in label b. Top N labels from label stack where the number of labels in label
stack is >N. stack is > N.
c. Bottom N labels from label stack where the number of labels in c. Bottom N labels from label stack where the number of labels in
label stack is >N. label stack is > N.
In a scenario where there is one flow label or entropy label present In a scenario where there is one flow label or entropy label present
in the label stack, the following further cases are possible for in the label stack, the following further cases are possible for
(2b), (2c), (3b) and (3c): (2b), (2c), (3b) and (3c):
1. N labels from label stack include flow label or entropy label. 1. N labels from label stack include flow label or entropy label.
2. N labels from label stack do not include flow label or entropy 2. N labels from label stack do not include flow label or entropy
label. label.
Also in a scenario where there are multiple entropy labels present in Also in a scenario where there are multiple entropy labels present in
skipping to change at page 18, line 12 skipping to change at page 18, line 12
o Search for entropy stops at the first entropy label. o Search for entropy stops at the first entropy label.
o Search for entropy includes any entropy label found plus continues o Search for entropy includes any entropy label found plus continues
to search for entropy in the label stack. to search for entropy in the label stack.
Furthermore, handling of reserved (i.e., special) labels varies among Furthermore, handling of reserved (i.e., special) labels varies among
implementations: implementations:
o Reserved labels are used in the hash as any other label would be o Reserved labels are used in the hash as any other label would be
(not a recommended practice). (not a recommended practice.)
o Reserved labels are skipped over and, for implementations limited o Reserved labels are skipped over and, for implementations limited
to N labels, the reserved labels do not count towards the limit of to N labels, the reserved labels do not count towards the limit of
N. N.
o Reserved labels are skipped over and, for implementations limited o Reserved labels are skipped over and, for implementations limited
to N labels, the reserved labels count towards the limit of N. to N labels, the reserved labels count towards the limit of N.
It is important to point this out since the presence of GAL will It is important to point this out since the presence of GAL will
affect those implementations which include reserved labels for load affect those implementations which include reserved labels for load
balancing purposes. balancing purposes.
skipping to change at page 18, line 43 skipping to change at page 18, line 43
is expected that most implementations will be of types "IP-based is expected that most implementations will be of types "IP-based
load balancer" or "Label-based load balancer". load balancer" or "Label-based load balancer".
o Section 2.4.5.1 of [RFC7325] recommends that searching for entropy o Section 2.4.5.1 of [RFC7325] recommends that searching for entropy
labels in the label stack should terminate upon finding the first labels in the label stack should terminate upon finding the first
entropy label. Therefore, it is expected that implementations entropy label. Therefore, it is expected that implementations
will only include the first (top-most) entropy label when there will only include the first (top-most) entropy label when there
are multiple entropy labels in the label stack. are multiple entropy labels in the label stack.
o It is expected that, in most cases, the number of labels in the o It is expected that, in most cases, the number of labels in the
label stack will not exceed number of labels (N) which label stack will not exceed the number of labels (N) which
implementations can include for load balancing purposes. implementations can include for load balancing purposes.
o It is expected that labels in the label stack, besides the flow o It is expected that labels in the label stack, besides the flow
label and entropy label, are constant for the lifetime of a single label and entropy label, are constant for the lifetime of a single
LSP multipath traceroute operation. Therefore, deviating load LSP multipath traceroute operation. Therefore, deviating load
balancing implementations with respect to reserved labels should balancing implementations with respect to reserved labels should
not affect this tool. not affect this tool.
Thus [RFC4379], [RFC6424], and this document supports cases (1) and Thus [RFC4379], [RFC6424], and this document support cases (1) and
(2a1), where only the first (top-most) entropy label is included when (2a1), where only the first (top-most) entropy label is included when
there are multiple entropy labels in the label stack. there are multiple entropy labels in the label stack.
11. Security Considerations 11. Security Considerations
This document extends the LSP Ping and Traceroute mechanisms to While [RFC4379] and [RFC6424] already allow for the discovery and
discover and exercise ECMP paths when an LSP uses ELI/EL in the label exercise of ECMP paths, this document extends the LSP Ping and
stack. Additional processing is required for responder and initiator Traceroute mechanisms to more precisely discover and exercise ECMP
nodes. The responder node that pushes ELI/EL will need to compute paths when an LSP uses ELI/EL in the label stack. Sourcing or
and return multipath data including associated EL. The initiator inspecting LSP Ping packets can be used for network reconnaissance.
node will need to store and handle both IP multipath and label
multipath information, and include destination IP addresses and/or The extended capability defined in this document requires small
ELs in MPLS echo request packets as well as in multipath information additional processing for the responder and initiator nodes. The
sent to downstream nodes. This document does not itself introduce responder node that pushes ELI/EL will need to compute and return
any new security considerations. The security measures described in multipath data including associated EL. The initiator node will need
[RFC4379], [RFC6424], and [RFC6790] are applicable. [RFC6424] to store and handle both IP Multipath and Label Multipath
provides guidelines if a network operator wants to prevent tracing or Information, and include destination IP addresses and/or ELs in MPLS
does not want to expose details of the tunnel and [RFC6790] provides echo request packets as well as in Multipath Information sent to
guidance on the use of the EL. downstream nodes. The security considerations of [RFC4379] already
cover Denial-of-Service attacks by regulating LSP Ping traffic going
to the control plane.
Finally, the security measures described in [RFC4379], [RFC6424], and
[RFC6790] are applicable. [RFC6424] provides guidelines if a network
operator wants to prevent tracing or does not want to expose details
of the tunnel and [RFC6790] provides guidance on the use of the EL.
12. IANA Considerations 12. IANA Considerations
12.1. Entropy Label FEC 12.1. Entropy Label FEC
The IANA is requested to assign a new sub-TLV from the "Sub-TLVs for The IANA is requested to assign a new sub-TLV from the "Sub-TLVs for
TLV Types 1, 16, and 21" section from the "Multi-Protocol Label TLV Types 1, 16, and 21" section from the "Multi-Protocol Label
Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs"
registry ([IANA-MPLS-LSP-PING]). registry ([IANA-MPLS-LSP-PING]).
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Note: The "Multipath Type" sub-registry is created by [RFC7537]. Note: The "Multipath Type" sub-registry is created by [RFC7537].
Value Meaning Reference Value Meaning Reference
---------- ---------------------------------------- --------- ---------- ---------------------------------------- ---------
TBD4 IP and label set this document TBD4 IP and label set this document
13. Acknowledgements 13. Acknowledgements
The authors would like to thank Loa Andersson, Curtis Villamizar, The authors would like to thank Loa Andersson, Curtis Villamizar,
Daniel King, Sriganesh Kini, Victor Ji, and Acee Lindem for Daniel King, Sriganesh Kini, Victor Ji, Acee Lindem, Deborah
performing thorough reviews and providing valuable comments. Brungard, Shawn M Emery, Scott O. Bradner, and Peter Yee for
performing thorough reviews and providing most valuable comments.
Carlos Pignataro would like to acknowledge his lifetime friend Martin
Rigueiro, with deep gratutide and esteem, for sharing his contagious
passion for engineering and sciences, and for selflessly teaching so
many lessons.
14. Contributing Authors 14. Contributing Authors
Nagendra Kumar Nagendra Kumar
Cisco Systems, Inc. Cisco Systems, Inc.
Email: naikumar@cisco.com Email: naikumar@cisco.com
15. References 15. References
15.1. Normative References 15.1. 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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
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