draft-ietf-mpls-entropy-lsp-ping-03.txt   draft-ietf-mpls-entropy-lsp-ping-04.txt 
Internet Engineering Task Force 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: 4379, 6424, 6790 (if approved) G. Swallow
Intended status: Standards Track C. Pignataro Intended status: Standards Track C. Pignataro
Expires: November 19, 2016 Cisco Expires: February 12, 2017 Cisco
A. Malis A. Malis
Huawei Technologies Huawei Technologies
S. Aldrin S. Aldrin
Google Google
May 18, 2016 August 11, 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-03 draft-ietf-mpls-entropy-lsp-ping-04
Abstract Abstract
The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Ping
Ping and Traceroute are used to exercise specific paths of Equal-Cost and Traceroute are methods used to test Equal-Cost Multipath (ECMP)
Multipath (ECMP). When LSP is signaled to use Entropy Label (EL) paths. Ping is known as a connectivity verification method and
described in RFC 6790, the ability for LSP Ping and Traceroute Traceroute as a fault isolation method, as described in RFC 4379.
operation to discover and exercise ECMP paths has been lost in When an LSP is signaled using the Entropy Label (EL) described in RFC
scenarios which LSRs apply deviating load balance techniques. One 6790, the ability for LSP Ping and Traceroute operations to discover
such scenario is when some LSRs apply EL based load balancing while and exercise ECMP paths is lost for scenarios where LSRs apply
other LSRs apply non-EL based load balancing (ex: IP). Another different load balancing techniques. One such scenario is when some
scenario is when EL based LSP is stitched with another LSP which can LSRs apply EL-based load balancing while other LSRs apply non-EL
be EL based or non-EL based. based load balancing (e.g., IP). Another scenario is when an EL-
based LSP is stitched with another LSP which can be EL-based or non-
EL based.
This document extends the MPLS LSP Ping and Traceroute mechanisms to This document extends the MPLS LSP Ping and Traceroute multipath
restore the ability of exercising specific paths of ECMP over LSP mechanisms in RFC 6424 to allow the ability of exercising LSPs which
which make use of the Entropy Label. This document updates RFC 4379, make use of the EL. This document updates RFC 4379, RFC 6424, and
RFC 6424, and 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
skipping to change at page 2, line 12 skipping to change at page 2, line 15
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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 November 19, 2016. This Internet-Draft will expire on February 12, 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.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Prerequisite . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Background . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. 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. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 8 5. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 8
6. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 9 6. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 9
6.1. IP Based Load Balancer & Not Pushing ELI/EL . . . . . . . 10 7. New Multipath Information Type: TBD4 . . . . . . . . . . . . 10
6.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 11 8. Initiating LSR Procedures . . . . . . . . . . . . . . . . . . 11
6.3. Label Based Load Balancer & Not Pushing ELI/EL . . . . . 12 9. Responder LSR Procedures . . . . . . . . . . . . . . . . . . 13
6.4. Label Based Load Balancer & Pushes ELI/EL . . . . . . . . 12 9.1. IP Based Load Balancer & Not Pushing ELI/EL . . . . . . . 14
6.5. Flow Aware MS-PW Stitching LSR . . . . . . . . . . . . . 13 9.2. IP Based Load Balancer & Pushes ELI/EL . . . . . . . . . 14
7. Entropy Label FEC . . . . . . . . . . . . . . . . . . . . . . 13 9.3. Label Based Load Balancer & Not Pushing ELI/EL . . . . . 15
8. DS Flags: L and E . . . . . . . . . . . . . . . . . . . . . . 14 9.4. Label Based Load Balancer & Pushes ELI/EL . . . . . . . . 16
9. New Multipath Information Type: TBD4 . . . . . . . . . . . . 15 9.5. Flow-Aware MS-PW Stitching LSR . . . . . . . . . . . . . 17
10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 16 10. Supported and Unsupported Cases . . . . . . . . . . . . . . . 17
11. Security Considerations . . . . . . . . . . . . . . . . . . . 18 11. Security Considerations . . . . . . . . . . . . . . . . . . . 19
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12.1. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19 12.1. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19
12.2. Multpath Type . . . . . . . . . . . . . . . . . . . . . 19 12.2. DS Flags . . . . . . . . . . . . . . . . . . . . . . . . 19
12.3. Entropy Label FEC . . . . . . . . . . . . . . . . . . . 19 12.3. Multipath Type . . . . . . . . . . . . . . . . . . . . . 20
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
14. Contributing Authors . . . . . . . . . . . . . . . . . . . . 20 14. Contributing Authors . . . . . . . . . . . . . . . . . . . . 20
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
15.1. Normative References . . . . . . . . . . . . . . . . . . 20 15.1. Normative References . . . . . . . . . . . . . . . . . . 20
15.2. Informative References . . . . . . . . . . . . . . . . . 20 15.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
1.1. Terminology 1.1. Terminology
The following acronyms/terminologies 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 LSR - Label Switching Router. o LSR - Label Switching Router.
o FEC - Forwarding Equivalent Class. o FEC - Forwarding Equivalent 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.
o Initiating LSR - LSR which sends MPLS echo request. o Initiating LSR - LSR which sends an MPLS echo request.
o Responder LSR - LSR which receives MPLS echo request and sends
MPLS echo reply.
o IP Based Load Balancer - LSR which load balances on fields from IP o Responder LSR - LSR which receives an MPLS echo request and sends
header (and possibly fields from upper layers), and does not an MPLS echo reply.
consider entropy label from label stack (i.e. Flow Label or
Entropy Label) for load balancing purpose.
o Label Based Load Balancer - LSR which load balances on entropy o IP-Based Load Balancer - LSR which load balances on fields from an
label from label stack (i.e. Flow Label or Entropy Label), and IP header (and possibly fields from upper layers), and does not
does not consider fields from IP header (and possibly fields from consider an entropy label from an MPLS label stack (i.e., flow
upper layers) for load balancing purpose. label [RFC6391] or entropy label [RFC6790]) for load balancing
purposes.
o Label and IP Based Load Balancer - LSR which load balances on both o Label-Based Load Balancer - LSR which load balances on an entropy
labels from label stack (including Flow Label or Entropy Label if label from an MPLS label stack (i.e., flow label or entropy
present) and fields from IP header (and possibly fields from upper label), and does not consider fields from an IP header (and
layers). possibly fields from upper layers) for load balancing purposes.
1.2. Prerequisite o Label and IP-Based Load Balancer - LSR which load balances on both
entropy labels from an MPLS label stack and fields from an IP
header (and possibly fields from upper layers).
MPLS implementations employ wide variety of load balancing techniques 1.2. Background
in terms of fields used for hash "keys". The mechanisms in [RFC4379]
updated by [RFC6424] are designed to provide multipath support for
subset of techniques. Intent of this document is to restore
multipath support for those supported techniques which have been
compromised by the introduction of [RFC6790] (i.e. Entropy Labels).
Section 10 describes supported and unsupported cases, and it may be
useful for one to visit this section first.
1.3. Background MPLS implementations employ a wide variety of load balancing
techniques in terms of fields used for hash "keys". The mechanisms
in [RFC4379] and updated by [RFC6424] are designed to provide
multipath support for a subset of techniques. The intent of this
document is to provide multipath support for the supported techniques
which are compromised by the use of ELs [RFC6790]. Section 10
describes supported and unsupported cases, and it may be useful for
the reader to first review this section.
Section 3.3.1 of [RFC4379] specifies multipath information encoding The Downstream Detailed Mapping (DDMAP) TLV [RFC6424] provides
in Downstream Mapping (DSMAP) TLV (Section 3.3 of [RFC4379]) and multipath information which can be used by an LSP Ping initiator to
Downstream Detailed Mapping (DDMAP) TLV (Section 3.3 of [RFC6424]) trace and validate ECMP paths between an ingress and egress. The
which can be used by LSP Ping initiator to trace and validate all multipath information encodings defined by [RFC6424] are sufficient
ECMP paths between ingress and egress. While the multipath when all the LSRs along the path(s), between ingress and egress,
information encoding is common to both the Downstream Mapping (DSMAP) consider the same set of "keys" as input for load balancing
TLV and the Downstream Detailed Mapping (DDMAP) TLV, the former has algorithms, e.g. either all IP-based or all label-based.
been deprecated by [RFC6424] and this specification only concerns
itself with the latter. The multipath information encodings are
sufficient when all the LSRs along the path(s), between ingress and
egress, consider same set of "keys" as input for load balancing
algorithm: all IP based or all label based.
With introduction of [RFC6790], it is quite normal to see set of LSRs With the introduction of [RFC6790], some LSRs may perform load
performing load balancing based on EL/ELI while others still follow balancing based on labels while others may be IP-based. This results
the traditional way (IP based). This results in LSP Ping initiator in an LSP Ping initiator to not be able to trace and validate all the
not be able to trace and validate all ECMP paths in following ECMP paths in the following scenarios:
scenarios:
o One or more transit LSRs along LSP with ELI/EL in label stack do o One or more transit LSRs along an LSP with ELI/EL in label stack
not perform ECMP load balancing based on EL (hashes based on do not perform ECMP load balancing based on EL (hashes based on
"keys" including IP destination address). This scenario is not "keys" including the IP destination address). This scenario is
only possible but quite common due transit LSRs not implementing not only possible but quite common due to transit LSRs not
[RFC6790] or transit LSRs implementing [RFC6790] but not implementing [RFC6790] or transit LSRs implementing [RFC6790], but
implementing suggested transit LSR behavior in Section 4.3 of not implementing the suggested transit LSR behavior in Section 4.3
[RFC6790]. of [RFC6790].
o Two or more LSPs stitched together with at least one of these LSP o Two or more LSPs stitched together with at least one of these LSPs
pushing ELI/EL in label stack. Such scenarios are described in pushing ELI/EL into the label stack.
[I-D.ravisingh-mpls-el-for-seamless-mpls].
These scenarios will be quite common because every deployment of These scenarios can be quite common because deployments of [RFC6790]
[RFC6790] will invariably end up with nodes that support ELI/EL and typically have a mixture of nodes that support ELI/EL and nodes that
nodes that do not. There will typically be areas that support ELI/EL do not. There will also typically be a mixture of areas that support
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 scenarios to restore ECMP discovery and tracing capabilities for the scenarios
described. described.
[RFC4379], [RFC6424], and this document will support IP-based load
balancers and label-based load balancers which limit their hash to
the first (top-most) or only entropy label in the label stack. Other
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 send 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 have 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
echo request the TLL is incremented by one until a response is additional echo request the TLL is incremented by one until a
received from the intended destination. Initiating LSR discovers and response is received from the intended destination. The initiating
exercises ECMP by obtaining multipath information from each transit LSR discovers and exercises ECMP by obtaining multipath information
LSR and using specific destination IP address or specific entropy from each transit LSR and using a specific destination IP address or
label. specific entropy label.
Notion of {x, y, z} from here on refers to Multipath information From here on, the notation {x, y, z} refers to multipath information
types x, y or z. types x, y or z. Multipath information types are defined in
Section 3.3 of [RFC4379].
LSP Ping initiating LSR sends MPLS echo request with multipath The LSR initiating LSP Ping sends an MPLS echo request with multipath
information. This multipath information is described in DDMAP TLV of information. This multipath information is described in the echo
echo request, and may contain set of IP addresses or set of labels. request's DDMAP TLV, and may contain a set of IP addresses or a set
Multipath information types {2, 4, 8} carry set of IP addresses and of labels. Multipath information types {2, 4, 8} carry a set of IP
multipath information type {9} carries set of labels. Responder LSR addresses, and multipath information type {9} carries a set of
(receiver of MPLS echo request) will determine the subset of labels. The responder LSR (the receiver of the MPLS echo request)
initiator specified multipath information which load balances to each will determine the subset of initiator-specified multipath
downstream (outgoing interface). Responder LSR sends MPLS echo reply information which load balances to each downstream (outgoing
with resulting multipath information per downstream (outgoing interface). The responder LSR sends an MPLS echo reply with
interface) back to the initiating LSR. Initiating LSR is then able resulting multipath information per downstream (outgoing interface)
to use specific IP destination address or specific label to exercise back to the initiating LSR. The initiating LSR is then able to use a
specific IP destination address or a specific label to exercise a
specific ECMP path on the responder LSR. specific ECMP path on the responder LSR.
Current behavior is problematic in following scenarios: Current behavior is problematic in following scenarios:
o Initiating LSR sends IP multipath information, but responder LSR o The initiating LSR sends IP multipath information, but the
load balances on labels. responder LSR load balances on labels.
o Initiating LSR sends label multipath information, but responder o The initiating LSR sends label multipath information, but the
LSR load balances on IP addresses. responder LSR load balances on IP addresses.
o Initiating LSR sends existing multipath information to LSR which o The initiating LSR sends existing multipath information to an LSR
pushes ELI/EL in label stack, but the initiating LSR can only which pushes ELI/EL in the label stack, but the initiating LSR can
continue to discover and exercise specific path of ECMP, if the only continue to discover and exercise specific paths of the ECMP,
LSR which pushes ELI/EL responds with both IP addresses and if the LSR which pushes ELI/EL responds with both IP addresses and
associated EL corresponding to each IP address. This is because: the associated EL corresponding to each IP address. This is
because:
* ELI/EL pushing LSR that is a stitching point will load balance * An ELI/EL pushing LSR that is a stitching point will load
based on IP address. balance based on the IP address.
* Downstream LSR(s) of ELI/EL pushing LSR may load balance based * Downstream LSR(s) of an ELI/EL pushing LSR may load balance
on ELs. based on ELs.
o Initiating LSR sends one of existing multipath information to ELI/ o The initiating LSR sends existing multipath information to an ELI/
EL pushing LSR, but initiating LSR can only continue to discover EL pushing LSR, but the initiating LSR can only continue to
and exercise specific path of ECMP if ELI/EL pushing LSR responds discover and exercise specific paths of ECMP, if the ELI/EL
with both labels and associated EL corresponding to label. This pushing LSR responds with both labels and associated EL
is because: corresponding to the label. This is because:
* ELI/EL pushing LSR that is a stitching point will load balance * An ELI/EL pushing LSR that is a stitching point will load
based on EL from previous LSP and pushes new EL. balance based on 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 point to how the existing multipath information The above scenarios demonstrate the existing multipath information is
is insufficient when LSP traceroute is operated on an LSP with insufficient when LSP traceroute is used on an LSP with entropy
Entropy Labels described by [RFC6790]. Therefore, this document labels [RFC6790]. This document defines a new multipath information
defines a multipath information type to be used in the DDMAP of MPLS type to be used in the DDMAP of MPLS echo request/reply packets for
echo request/reply packets in Section 9. [RFC6790] LSPs.
In addition, responder LSR can reply with empty multipath information The responder LSR can reply with empty multipath information if no IP
if no IP address set or label set from received multipath information address is set or label set is received with the multipath
matched load balancing to a downstream. Empty return is also information. An empty return is also possible if an initiating LSR
possible if initiating LSR sends multipath information of one type, sends multipath information of one type, IP address or label, but the
IP address or label, but responder LSR load balances on the other responder LSR load balances on the other type. To disambiguate
type. To disambiguate between the two results, this document between the two results, this document introduces new flags in the
introduces new flags in the DDMAP TLV to allow responder LSR to DDMAP TLV to allow the responder LSR to describe the load balancing
describe the load balance technique being used. technique being used.
It is required that all LSRs along the LSP understand new flags as All LSRs along the LSP need to be able to understand the new flags
well as new multipath information type. It is also required that and the new multipath information type. It is also required that the
initiating LSR can select both IP destination address and label to initiating LSR can select both the IP destination address and label
use on transmitting MPLS echo request packets. Two additional DS to use when transmitting MPLS echo request packets. Two additional
Flags are defined for the DDMAP TLV in Section 8. These two flags DS Flags are defined for the DDMAP TLV in Section 6. These two flags
are used by the responder LSR to describe its load balance behavior are used by the responder LSR to describe its load balance behavior
on received MPLS echo request. on a received MPLS echo request.
Note that the terms "IP Based Load Balancer", "Label Based Load Note that the terms "IP-Based Load Balancer" and "Label-Based Load
Balancer" and "Label Based Load Balancer" are in context of how Balancer" are in context of how a received MPLS echo request is
received MPLS echo request is handled by the responder LSR. handled by the responder LSR.
3. Multipath Type 9 3. Multipath Type 9
This section defines to which labels multipath type {9} applies.
[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 their respective out-going interfaces. determine the respective outgoing interfaces.
Section 7 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 which 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, the initiator includes an In order to trace a flow-aware Pseudowire [RFC6391], the initiator
EL-FEC at the bottom of the FEC-Stack and pushes the appropriate PW- includes an EL FEC at the bottom of the FEC Stack and pushes the
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. Initiating LSR Procedures 5. Entropy Label FEC
In order to facilitate the flow of the following text we speak in The entropy label indicator (ELI) is a reserved label that has no
terms of a boolean called EL_LSP maintained by the initiating LSR. explicit FEC associated, and has label value 7 assigned from the
This value controls the multipath information type to be used in reserved range. Use the Nil FEC as the Target FEC Stack sub-TLV to
transmitted echo request packets. When the initiating LSR is account for ELI in a Target FEC Stack TLV.
transmitting an echo request packet with DDMAP with a non-zero
multipath information type, then EL_LSP boolean MUST be consulted to
determine the multipath information type to use.
In addition to procedures described in [RFC4379] as updated by The entropy label (EL) is a special purpose label with the label
Section 3 and [RFC6424], initiating LSR MUST operate with following value being discretionary (i.e., the label value is not from the
procedures. reserved range). For LSP verification mechanics to perform its
purpose, it is necessary for a Target FEC Stack sub-TLV to clearly
describe the EL, particularly in the scenario where the label stack
does not carry ELI (e.g., flow-aware Pseudowire [RFC6391]).
Therefore, this document defines an EL FEC sub-TLV (TBD1, see
Section 12.1) to allow a Target FEC Stack sub-TLV to be added to the
Target FEC Stack to account for EL.
The Length is 4. Labels are 20-bit values treated as numbers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Entropy Label FEC
Label is the actual label value inserted in the label stack; the MBZ
field MUST be zero when sent and ignored on receipt.
6. DS Flags: L and E
Two flags, L and E, are added to the DS Flags field of the DDMAP TLV.
Both flags MUST NOT be set in echo request packets when sending, and
SHOULD be ignored when received. Zero, one or both new flags MUST be
set in echo reply packets.
DS Flags
--------
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| MBZ |L|E|I|N|
+-+-+-+-+-+-+-+-+
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.
Flag Name and Meaning
---- ----------------
L Label-based load balance indicator
This flag MUST be set to zero in the echo request. An LSR
which performs load balancing on a label MUST set this
flag in the echo reply. An LSR which performs load
balancing on IP MUST NOT set this flag in the echo
reply.
E ELI/EL push indicator
This flag MUST be set to zero in the echo request. An LSR
which pushes ELI/EL MUST set this flag in the echo
reply. An LSR which does not push ELI/EL MUST NOT set
this flag in the echo reply.
The two flags result in four load balancing techniques which the echo
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=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
ELI/EL.
o {L=1, E=1} LSR load balances based on labels and pushes ELI/EL.
7. New Multipath Information Type: TBD4
One new multipath information type is added to be used in DDMAP TLV.
This new multipath type has the value of TBD4.
Key Type Multipath Information
--- ---------------- ---------------------
TBD4 IP and label set IP addresses and label prefixes
Multipath type TBD4 is comprised of three sections. The first
section describes the IP address set. The second section describes
the label set. The third section describes another label set which
associates to either the IP address set or the label set specified in
the other sections.
Multipath information type TBD4 has following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPMultipathType| IP Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (IP Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|LbMultipathType| Label Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (Label Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Assoc Label Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (Associated Label Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Multipath Information Type TBD4
o IPMultipathType
* 0 when "IP Multipath Information" is omitted. Otherwise, one
of the IP multipath information values: {2, 4, 8}.
o IP Multipath Information
* This section is omitted when "IPMultipathType" is 0.
Otherwise, this section reuses IP multipath information from
[RFC4379]. Specifically, multipath information for values {2,
4, 8} can be used.
o LbMultipathType
* 0 when "Label Multipath Information" is omitted. Otherwise,
label multipath information value {9}.
o Label Multipath Information
* This section is omitted when "LbMultipathType" is 0.
Otherwise, this section reuses label multipath information from
[RFC4379]. Specifically, multipath information for value {9}
can be used.
o Associated Label Multipath Information
* "Assoc Label Multipath Length" is a 16 bit field of multipath
information which indicates the length in octets of the
associated label multipath information.
* "Associated Label Multipath Information" is a list of labels
with each label described in 24 bits. This section MUST be
omitted in an MPLS echo request message. A midpoint which
pushes ELI/EL labels SHOULD include "Assoc Label Multipath
Information" in its MPLS echo reply message, along with either
"IP Multipath Information" or "Label Multipath Information".
Each specified associated label described in this section maps
to a specific IP address OR label described in the "IP
Multipath Information" section or "Label Multipath Information"
section. For example, if three IP addresses are specified in
the "IP Multipath Information" section, then there MUST be
three labels described in this section. The first label maps
to the first IP address specified, the second label maps to the
second IP address specified, and the third label maps to the
third IP address specified.
When a section is omitted, the length for that section MUST BE set to
zero.
8. Initiating LSR Procedures
The following procedure is described in terms of an EL_LSP boolean
maintained by the initiating LSR. This value controls the multipath
information type to be used in the transmitted echo request packets.
When the initiating LSR is transmitting an echo request packet with
DDMAP with a non-zero multipath information type, then the EL_LSP
boolean MUST be consulted to determine the multipath information type
to use.
In addition to procedures described in [RFC4379], as updated by
Section 3 and [RFC6424], the initiating LSR MUST operate with the
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 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 same responder LSR cannot handle type type {TBD4} unless the responder LSR cannot handle type {TBD4}.
{TBD4}. When the initiating LSR is transmitting multipath When the initiating LSR is transmitting multipath information
information type {TBD4} in this case, both "IP Multipath type {TBD4}, both "IP Multipath Information" and "Label
Information" and "Label Multipath Information" MUST be Multipath Information" MUST be included, and "IP Associated
included, and "IP Associated Label Multipath Information" MUST Label Multipath Information" MUST be omitted (NULL).
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 "IP Associated Label Multipath Information"
MUST be omitted (NULL). MUST be omitted (NULL).
o When the initiating LSR receives echo reply with {L=0, E=1} in DS o When the initiating LSR receives echo reply with {L=0, E=1} in DS
flags with valid contents, set EL_LSP=True. flags with valid contents, set EL_LSP=True.
In following conditions, the initiating LSR may have lost the ability In the following conditions, the initiating LSR may have lost the
to exercise specific ECMP paths. The initiating LSR MAY continue ability to exercise specific ECMP paths. The initiating LSR MAY
with "best effort". 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}.
6. 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 to not 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 following DS Flags cleared (i.e., not set): "ELI/EL
push indicator" and "Label based load balance indicator". 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 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 to
consider the packet as malformed and return code 1 (Malformed echo consider the packet as malformed and return code 1 ("Malformed
request received) in the MPLS echo reply packet. 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 * IP associated label multipath information MUST be omitted
(NULL). (NULL).
Following subsections describe expected responder LSR procedures when The following subsections describe expected responder LSR procedures
echo reply is to include DDMAP TLVs, based on local load balance when the echo reply is to include DDMAP TLVs, based on the local load
technique being employed. In case the responder LSR performs balance technique being employed. In case the responder LSR performs
deviating load balance techniques per downstream basis, appropriate deviating load balance techniques on a per downstream basis,
procedures matching to each downstream load balance technique MUST be appropriate procedures matched to each downstream load balance
operated. technique MUST be followed.
6.1. 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, 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}.
* "Label Multipath Information" and "Associated Label Multipath * The "Label Multipath Information" and "Associated Label
Information" sections MUST be omitted (NULL). Multipath Information" sections MUST be omitted (NULL).
* If no matching IP address is found, then "IPMultipathType" * If no matching IP address is found, then the "IPMultipathType"
field MUST be set to multipath information type {0} and "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 * 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 "IP Multipath Information" information type {2, 4, 8} and the "IP Multipath Information"
section MUST be included. section MUST be included.
6.2. 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, 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 9 for details of multipath type {TBD4}. Section 7 for details of multipath type {TBD4}.
* "Label Multipath Information" section MUST be omitted (i.e. is
it not there).
* IP address set specified in received IP multipath information * The "Label Multipath Information" section MUST be omitted
MUST be used to determine the returning IP/Label pairs. (i.e., it is not there).
* If received multipath information type was {TBD4}, received * The IP address set specified in the received IP multipath
"Label Multipath Information" sections MUST NOT be used to information MUST be used to determine the returning IP/Label
determine the associated label portion of returning IP/Label
pairs. pairs.
* If no matching IP address is found, then "IPMultipathType" * If the received multipath information type was {TBD4}, the
field MUST be set to multipath information type {0} and "IP received "Label Multipath Information" sections MUST NOT be
used to determine the associated label portion of returning IP/
Label pairs.
* If no matching IP address is found, then the "IPMultipathType"
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,
"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 IP address is found, then * 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 "IP Multipath Information" information type {2, 4, 8} and the "IP Multipath Information"
section MUST be included. In addition, "Associated Label section MUST be included. In addition, the "Associated Label
Multipath Information" section MUST be populated with list of Multipath Information" section MUST be populated with a list of
labels corresponding to each IP address specified in "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 length in octets of MUST be set to a value representing the length in octets of the
"Associated Label Multipath Information" field. "Associated Label Multipath Information" field.
6.3. 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, 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}.
* "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 "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 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 "LbMultipathType" * If at least one matching label is found, then the
field MUST be set to appropriate multipath information type {9} "LbMultipathType" field MUST be set to the appropriate
and "Label Multipath Information" section MUST be included. multipath information type {9} and the "Label Multipath
Information" section MUST be included.
6.4. 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, following procedures are o If multipath type {9, TBD4} is received, the following procedures
to be used: are to be used:
* The responder MUST respond with multipath type {TBD4}. * The responder MUST respond with multipath type {TBD4}.
* "IP Multipath Information" section MUST be omitted. * The "IP Multipath Information" section MUST be omitted.
* Label set specified in received label multipath information * The label set specified in the received label multipath
MUST be used to determine the returning Label/Label pairs. information MUST be used to determine the returning Label/Label
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 returning Label/Label
pairs. pairs.
* If no matching label is found, then "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 "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 "LbMultipathType" * If at least one matching label is found, then the
field MUST be set to appropriate multipath information type {9} "LbMultipathType" field MUST be set to the appropriate
and "Label Multipath Information" section MUST be included. In multipath information type {9} and the "Label Multipath
addition, "Associated Label Multipath Information" section MUST Information" section MUST be included. In addition, the
be populated with list of labels corresponding to each label "Associated Label Multipath Information" section MUST be
specified in "Label Multipath Information" section. "Assoc populated with a list of labels corresponding to each label
Label Multipath Length" MUST be set to a value representing specified in the "Label Multipath Information" section. "Assoc
length in octets of "Associated Label Multipath Information" Label Multipath Length" MUST be set to a value representing the
field. length in octets of the "Associated Label Multipath
Information" field.
6.5. Flow Aware MS-PW Stitching LSR 9.5. Flow-Aware MS-PW Stitching LSR
Stitching LSR that cross-connects Flow Aware Pseudowires behave in A stitching LSR that cross-connects flow-aware Pseudowires behaves in
one of two ways: one of two ways:
o Load balances on previous Flow Label, and carries over same Flow o Load balances on the previous flow label, and carries over the
Label. For this case, stitching LSR is to behave as procedures same flow label. For this case, the stitching LSR is to behave as
described in Section 6.3. described in Section 9.3.
o Load balances on previous Flow Label, and replaces Flow Label with
newly computed. For this case, stitching LSR is to behave as
procedures described in Section 6.4.
7. Entropy Label FEC
Entropy Label Indicator (ELI) is a reserved label that has no
explicit FEC associated, and has label value 7 assigned from the
reserved range. Use Nil FEC as Target FEC Stack sub-TLV to account
for ELI in a Target FEC Stack TLV.
Entropy Label (EL) is a special purpose label with label value being
discretionary (i.e. label value may not be from the reserved range).
For LSP verification mechanics to perform its purpose, it is
necessary for a Target FEC Stack sub-TLV to clearly describe EL,
particularly in the scenario where label stack does not carry ELI
(ex: Flow Aware Pseudowire [RFC6391]). Therefore, this document
defines a EL FEC to allow a Target FEC Stack sub-TLV to be added to
the Target FEC Stack to account for EL.
The Length is 4. Labels are 20-bit values treated as numbers.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Entropy Label FEC
Label is the actual label value inserted in the label stack; the MBZ
fields MUST be zero when sent and ignored on receipt.
8. DS Flags: L and E
Two flags, L and E, are added in DS Flags field of the DDMAP TLV.
Both flags MUST NOT be set in echo request packets when sending, and
ignored when received. Zero, one or both new flags MUST be set in
echo reply packets.
DS Flags
--------
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| MBZ |L|E|I|N|
+-+-+-+-+-+-+-+-+
RFC-Editor-Note: Please update above figure to place the flag E in
the bit number TBD2 and the flag L in the bit number TBD3.
Flag Name and Meaning
---- ----------------
L Label based load balance indicator
This flag MUST be set to zero in the echo request. LSR
which performs load balancing on a label MUST set this
flag in the echo reply. LSR which performs load
balancing on IP MUST NOT set this flag in the echo
reply.
E ELI/EL push indicator
This flag MUST be set to zero in the echo request. LSR
which pushes ELI/EL MUST set this flag in the echo
reply. LSR which does not push ELI/EL MUST NOT set
this flag in the echo reply.
Two flags result in four load balancing techniques which echo 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=1} LSR load balances based on IP and pushes ELI/EL.
o {L=1, E=0} LSR load balances based on label and does not push ELI/
EL.
o {L=1, E=1} LSR load balances based on label and pushes ELI/EL.
9. New Multipath Information Type: TBD4
One new multipath information type is added to be used in DDMAP TLV.
New multipath type has value of TBD4.
Key Type Multipath Information
--- ---------------- ---------------------
TBD4 IP and label set IP addresses and label prefixes
Multipath type TBD4 is comprised of three sections. One section to
describe IP address set. One section to describe label set. One
section to describe another label set which associates to either IP
address set or label set specified in the other section.
Multipath information type TBD4 has following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPMultipathType| IP Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (IP Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|LbMultipathType| Label Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (Label Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Assoc Label Multipath Length | Reserved(MBZ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| (Associated Label Multipath Information) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Multipath Information Type TBD4
o IPMultipathType
* 0 when "IP Multipath Information" is omitted. Otherwise one of
IP multipath information values: {2, 4, 8}.
o IP Multipath Information
* This section is omitted when "IPMultipathType" is 0. Otherwise
this section reuses IP multipath information from [RFC4379].
Specifically, multipath information for values {2, 4, 8} can be
used.
o LbMultipathType
* 0 when "Label Multipath Information" is omitted. Otherwise
label multipath information value {9}.
o Label Multipath Information
* This section is omitted when "LbMultipathType" is 0. Otherwise
this section reuses label multipath information from [RFC4379].
Specifically, multipath information for value {9} can be used.
o Associated Label Multipath Information
* "Assoc Label Multipath Length" is a 16 bit field of multipath
information which indicates length in octets of the associated
label multipath information.
* "Associated Label Multipath Information" is a list of labels o Load balances on the previous flow label, and replaces the flow
with each label described in 24 bits. This section MUST be label with a newly computed label. For this case, the stitching
omitted in an MPLS echo request message. A midpoint which LSR is to behave as described in Section 9.4.
pushes ELI/EL labels SHOULD include "Assoc Label Multipath
Information" in its MPLS echo reply message, along with either
"IP Multipath Information" or "Label Multipath Information".
Each specified associated label described in this section maps
to specific IP address OR label described in the "IP Multipath
Information" section or "Label Multipath Information" section.
For example, if 3 IP addresses are specified in the "IP
Multipath Information" section, then there MUST be 3 labels
described in this section. First label maps to the lowest IP
address specified, second label maps to the second lowest IP
address specified and third label maps to the third lowest IP
address specified.
10. Supported and Unsupported Cases 10. Supported and Unsupported Cases
MPLS architecture never defined strict rules on how implementations The MPLS architecture does not define strict rules on how
are to identify hash "keys" for load balancing purpose. As result, implementations are to identify hash "keys" for load balancing
implementations may be of following load balancer types: purpose. As a result, implementations may be of the following load
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), implementation can include different sets of For cases (2) and (3), an implementation can include different sets
labels from the label stack for load balancing purpose. Thus 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 number of labels in label b. Top N labels from label stack where the number of labels in label
stack is >N.
c. Bottom N labels from label stack where number of labels in label
stack is >N. stack is >N.
c. Bottom N labels from label stack where the number of labels in
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, following further cases are possible for (2b), in the label stack, the following further cases are possible for
(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 does 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
the label stack, it is possible for implementations to employ the label stack, it is possible for implementations to employ
deviating techniques: deviating techniques:
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
(a bad 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 presence of GAL will affect It is important to point this out since the presence of GAL will
those implementations which include reserved labels for load affect those implementations which include reserved labels for load
balancing purpose. balancing purposes.
As can be seen from above, there are many flavors of potential load As can be seen from the above, there are many types of potential load
balancing implementations. Attempting for any OAM tools to support balancing implementations. Attempting for any OAM tools to support
ECMP discovery and traversal over all flavors of such will require ECMP discovery and traversal over all types would require fairly
fairly complex procedures and implementations to support those complex procedures. Complexities in OAM tools have minimal benefit
complex procedures. Complexities in OAM tools will produce minimal if the majority of implementations are expected to employ only a
benefits if majority of implementations are expected to employ small small subset of the cases described above.
subset of cases described above.
o Section 4.3 of [RFC6790] states that implementations, for load o Section 4.3 of [RFC6790] states that in implementations, for load
balancing purpose, parsing beyond the label stack after finding balancing purposes, parsing beyond the label stack after finding
Entropy Label is "limited incremental value". Therefore, it is an entropy label has "limited incremental value". Therefore, it
expected that most implementations will be of types "IP Based Load is expected that most implementations will be of types "IP-based
Balancer" or "Label Based Load Balancer". load balancer" or "Label-based load balancer".
o Section 2.4.5.1 of [RFC7325] recommends that search for entropies o Section 2.4.5.1 of [RFC7325] recommends that searching for entropy
from 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, number of labels in the label o It is expected that, in most cases, the number of labels in the
stack will not exceed number of labels (N) which implementations label stack will not exceed number of labels (N) which
can include for load balancing purpose. implementations can include for load balancing purposes.
o It is expected that labels in the label stack, besides Flow Label o It is expected that labels in the label stack, besides the flow
and Entropy Label, are constant for the lifetime of a single LSP label and entropy label, are constant for the lifetime of a single
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 will support cases (1) Thus [RFC4379], [RFC6424], and this document supports cases (1) and
and (2a1), where only the first (top-most) Entropy Label is included (2a1), where only the first (top-most) entropy label is included when
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 LSP Traceroute mechanism to discover and This document extends the LSP Ping and Traceroute mechanisms to
exercise ECMP paths when LSP uses ELI/EL in label stack. Additional discover and exercise ECMP paths when an LSP uses ELI/EL in the label
processings are required for responder and initiator nodes. stack. Additional processing is required for responder and initiator
Responder node that pushes ELI/EL will need to compute and return nodes. The responder node that pushes ELI/EL will need to compute
multipath data including associated EL. Initiator node will need to and return multipath data including associated EL. The initiator
store and handle both IP multipath and label multipath information, node will need to store and handle both IP multipath and label
and include destination IP addresses and/or ELs in MPLS echo request multipath information, and include destination IP addresses and/or
packet as well as in carried multipath information to downstream ELs in MPLS echo request packets as well as in multipath information
nodes. Due to additional processing, it is critical that proper sent to downstream nodes. This document does not itself introduce
security measures described in [RFC4379] and [RFC6424] are followed. any new security considerations. 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. DS Flags 12.1. Entropy Label FEC
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
Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs"
registry ([IANA-MPLS-LSP-PING]).
Sub-Type Sub-TLV Name Reference
-------- ------------ ---------
TBD1 Entropy label FEC this document
12.2. DS Flags
The IANA is requested to assign new bit numbers from the "DS flags" The IANA is requested to assign new bit numbers from the "DS flags"
sub-registry from the "Multi-Protocol Label Switching (MPLS) Label sub-registry from the "Multi-Protocol Label Switching (MPLS) Label
Switched Paths (LSPs) Ping Parameters - TLVs" registry Switched Paths (LSPs) Ping Parameters - TLVs" registry
([IANA-MPLS-LSP-PING]). ([IANA-MPLS-LSP-PING]).
Note: the "DS flags" sub-registry is created by [RFC7537]. Note: the "DS flags" sub-registry is created by [RFC7537].
Bit number Name Reference Bit number Name Reference
---------- ---------------------------------------- --------- ---------- ---------------------------------------- ---------
TBD2 E: ELI/EL push indicator this document TBD2 E: ELI/EL push indicator this document
TBD3 L: Label based load balance indicator this document TBD3 L: Label-based load balance indicator this document
12.2. Multpath Type 12.3. Multipath Type
The IANA is requested to assign a new value from the "Multipath Type" The IANA is requested to assign a new value from the "Multipath Type"
sub-registry from the "Multi-Protocol Label Switching (MPLS) Label sub-registry from the "Multi-Protocol Label Switching (MPLS) Label
Switched Paths (LSPs) Ping Parameters - TLVs" registry Switched Paths (LSPs) Ping Parameters - TLVs" registry
([IANA-MPLS-LSP-PING]). ([IANA-MPLS-LSP-PING]).
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
12.3. Entropy Label FEC
The IANA is requested to assign a new sub-TLV from the "Sub-TLVs for
TLV Types 1 and 16" section from the "Multi-Protocol Label Switching
(MPLS) Label Switched Paths (LSPs) Ping Parameters - TLVs" registry
([IANA-MPLS-LSP-PING]).
Sub-Type Sub-TLV Name Reference
-------- ------------ ---------
TBD1 Entropy Label FEC this document
13. Acknowledgements 13. Acknowledgements
Authors would like to thank Loa Andersson, Curtis Villamizar, Daniel The authors would like to thank Loa Andersson, Curtis Villamizar,
King, Sriganesh Kini and Victor Ji for performing thorough review and Daniel King, Sriganesh Kini, Victor Ji, and Acee Lindem for
providing valuable comments. performing thorough reviews and providing valuable comments.
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
skipping to change at page 20, line 25 skipping to change at page 20, line 44
[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>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379, Label Switched (MPLS) Data Plane Failures", RFC 4379,
DOI 10.17487/RFC4379, February 2006, DOI 10.17487/RFC4379, February 2006,
<http://www.rfc-editor.org/info/rfc4379>. <http://www.rfc-editor.org/info/rfc4379>.
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
Performing Label Switched Path Ping (LSP Ping) over MPLS
Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
<http://www.rfc-editor.org/info/rfc6424>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding", L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012, RFC 6790, DOI 10.17487/RFC6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>. <http://www.rfc-editor.org/info/rfc6790>.
[RFC7537] Decraene, B., Akiya, N., Pignataro, C., Andersson, L., and [RFC7537] Decraene, B., Akiya, N., Pignataro, C., Andersson, L., and
S. Aldrin, "IANA Registries for LSP Ping Code Points", S. Aldrin, "IANA Registries for LSP Ping Code Points",
RFC 7537, DOI 10.17487/RFC7537, May 2015, RFC 7537, DOI 10.17487/RFC7537, May 2015,
<http://www.rfc-editor.org/info/rfc7537>. <http://www.rfc-editor.org/info/rfc7537>.
15.2. Informative References 15.2. Informative References
[I-D.ravisingh-mpls-el-for-seamless-mpls]
Singh, R., Shen, Y., and J. Drake, "Entropy label for
seamless MPLS", draft-ravisingh-mpls-el-for-seamless-
mpls-04 (work in progress), October 2014.
[IANA-MPLS-LSP-PING] [IANA-MPLS-LSP-PING]
IANA, "Multi-Protocol Label Switching (MPLS) Label IANA, "Multi-Protocol Label Switching (MPLS) Label
Switched Paths (LSPs) Ping Parameters", Switched Paths (LSPs) Ping Parameters",
<http://www.iana.org/assignments/mpls-lsp-ping-parameters/ <http://www.iana.org/assignments/mpls-lsp-ping-parameters/
mpls-lsp-ping-parameters.xhtml>. mpls-lsp-ping-parameters.xhtml>.
[RFC6391] Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V., [RFC6391] Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V.,
Regan, J., and S. Amante, "Flow-Aware Transport of Regan, J., and S. Amante, "Flow-Aware Transport of
Pseudowires over an MPLS Packet Switched Network", Pseudowires over an MPLS Packet Switched Network",
RFC 6391, DOI 10.17487/RFC6391, November 2011, RFC 6391, DOI 10.17487/RFC6391, November 2011,
<http://www.rfc-editor.org/info/rfc6391>. <http://www.rfc-editor.org/info/rfc6391>.
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
Performing Label Switched Path Ping (LSP Ping) over MPLS
Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
<http://www.rfc-editor.org/info/rfc6424>.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A., [RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325, Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <http://www.rfc-editor.org/info/rfc7325>. August 2014, <http://www.rfc-editor.org/info/rfc7325>.
Authors' Addresses Authors' Addresses
Nobo Akiya Nobo Akiya
Big Switch Networks Big Switch Networks
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