draft-ietf-mpls-entropy-lsp-ping-02.txt   draft-ietf-mpls-entropy-lsp-ping-03.txt 
Internet Engineering Task Force N. Akiya Internet Engineering Task Force 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: July 7, 2016 Cisco Expires: November 19, 2016 Cisco
A. Malis A. Malis
Huawei Technologies Huawei Technologies
S. Aldrin S. Aldrin
Google Google
January 4, 2016 May 18, 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-02 draft-ietf-mpls-entropy-lsp-ping-03
Abstract Abstract
The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP)
Ping and Traceroute are used to exercise specific paths of Equal-Cost Ping and Traceroute are used to exercise specific paths of Equal-Cost
Multipath (ECMP). When LSP is signaled to use Entropy Label (EL) Multipath (ECMP). When LSP is signaled to use Entropy Label (EL)
described in RFC 6790, the ability for LSP Ping and Traceroute described in RFC 6790, the ability for LSP Ping and Traceroute
operation to discover and exercise ECMP paths has been lost in operation to discover and exercise ECMP paths has been lost in
scenarios which LSRs apply deviating load balance techniques. One scenarios which LSRs apply deviating load balance techniques. One
such scenario is when some LSRs apply EL based load balancing while such scenario is when some LSRs apply EL based load balancing while
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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 July 7, 2016. This Internet-Draft will expire on November 19, 2016.
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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upper layers) for load balancing purpose. upper layers) for load balancing purpose.
o Label and IP Based Load Balancer - LSR which load balances on both o Label and IP Based Load Balancer - LSR which load balances on both
labels from label stack (including Flow Label or Entropy Label if labels from label stack (including Flow Label or Entropy Label if
present) and fields from IP header (and possibly fields from upper present) and fields from IP header (and possibly fields from upper
layers). layers).
1.2. Prerequisite 1.2. Prerequisite
MPLS implementations employ wide variety of load balancing techniques MPLS implementations employ wide variety of load balancing techniques
in terms of fields used for hash "keys". [RFC4379] and [RFC6424] are in terms of fields used for hash "keys". The mechanisms in [RFC4379]
designed to provide multipath support for subset of techniques. updated by [RFC6424] are designed to provide multipath support for
Intent of this document is to restore multipath support for those subset of techniques. Intent of this document is to restore
supported techniques which have been compromised by the introduction multipath support for those supported techniques which have been
of [RFC6790] (i.e. Entropy Labels). Section 10 describes supported compromised by the introduction of [RFC6790] (i.e. Entropy Labels).
and unsupported cases, and it may be useful for one to visit this Section 10 describes supported and unsupported cases, and it may be
section first. useful for one to visit this section first.
1.3. Background 1.3. Background
Section 3.3.1 of [RFC4379] specifies multipath information encoding Section 3.3.1 of [RFC4379] specifies multipath information encoding
in Downstream Mapping TLV (Section 3.3 of [RFC4379]) and Downstream in Downstream Mapping (DSMAP) TLV (Section 3.3 of [RFC4379]) and
Detailed Mapping TLV (Section 3.3 of [RFC6424]) which can be used by Downstream Detailed Mapping (DDMAP) TLV (Section 3.3 of [RFC6424])
LSP Ping initiator to trace and validate all ECMP paths between which can be used by LSP Ping initiator to trace and validate all
ingress and egress. These encodings are sufficient when all the LSRs ECMP paths between ingress and egress. While the multipath
along the path(s), between ingress and egress, consider same set of information encoding is common to both the Downstream Mapping (DSMAP)
"keys" as input for load balancing algorithm: all IP based or all TLV and the Downstream Detailed Mapping (DDMAP) TLV, the former has
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 introduction of [RFC6790], it is quite normal to see set of LSRs
performing load balancing based on EL/ELI while others still follow performing load balancing based on EL/ELI while others still follow
the traditional way (IP based). This results in LSP Ping initiator the traditional way (IP based). This results in LSP Ping initiator
not be able to trace and validate all ECMP paths in following not be able to trace and validate all ECMP paths in 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 LSP with ELI/EL in label stack do
not perform ECMP load balancing based on EL (hashes based on not perform ECMP load balancing based on EL (hashes based on
"keys" including IP destination address). This scenario is not "keys" including IP destination address). This scenario is not
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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 LSP
pushing ELI/EL in label stack. Such scenarios are described in pushing ELI/EL in label stack. Such scenarios are described in
[I-D.ravisingh-mpls-el-for-seamless-mpls]. [I-D.ravisingh-mpls-el-for-seamless-mpls].
These scenarios will be quite common because every deployment of These scenarios will be quite common because every deployment of
[RFC6790] will invariably end up with nodes that support ELI/EL and [RFC6790] will invariably end up with nodes that support ELI/EL and
nodes that do not. There will typically be areas that support ELI/EL nodes that do not. There will typically be areas that support ELI/EL
and areas that do not. and areas that do not.
As pointed out in [RFC6790] the procedures of [RFC4379] with respect As pointed out in [RFC6790] the procedures of [RFC4379] (and
to multipath information type {9} are incomplete. However [RFC6790] consequently of [RFC6424]) with respect to multipath information type
does not actually update [RFC4379]. Further the specific EL location {9} are incomplete. However [RFC6790] does not actually update
is not clearly defined, particularly in the case of Flow Aware [RFC4379]. Further the specific EL location is not clearly defined,
Pseudowires [RFC6391]. This document defines a new FEC Stack sub-TLV particularly in the case of Flow Aware Pseudowires [RFC6391]. This
for the Entropy Label. Section 3 of this document updates the document defines a new FEC Stack sub-TLV for the Entropy Label.
procedures for multipath information type {9} described in [RFC4379]. Section 3 of this document updates the procedures for multipath
Rest of this document describes extensions required to restore ECMP information type {9} described in [RFC4379] and applicable to
discovery and tracing capabilities for scenarios described. [RFC6424]. The rest of this document describes extensions required
to restore ECMP discovery and tracing capabilities for scenarios
described.
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 send 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 have 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 echo request the TLL is incremented by one until a response is
received from the intended destination. Initiating LSR discovers and received from the intended destination. Initiating LSR discovers and
exercises ECMP by obtaining multipath information from each transit exercises ECMP by obtaining multipath information from each transit
LSR and using specific destination IP address or specific entropy LSR and using specific destination IP address or specific entropy
label. label.
Notion of {x, y, z} from here on refers to Multipath information Notion of {x, y, z} from here on refers to Multipath information
types x, y or z. types x, y or z.
LSP Ping initiating LSR sends MPLS echo request with multipath LSP Ping initiating LSR sends MPLS echo request with multipath
information. This multipath information is described in DSMAP/DDMAP information. This multipath information is described in DDMAP TLV of
TLV of echo request, and may contain set of IP addresses or set of echo request, and may contain set of IP addresses or set of labels.
labels. Multipath information types {2, 4, 8} carry set of IP Multipath information types {2, 4, 8} carry set of IP addresses and
addresses and multipath information type {9} carries set of labels. multipath information type {9} carries set of labels. Responder LSR
Responder LSR (receiver of MPLS echo request) will determine the (receiver of MPLS echo request) will determine the subset of
subset of initiator specified multipath information which load initiator specified multipath information which load balances to each
balances to each downstream (outgoing interface). Responder LSR downstream (outgoing interface). Responder LSR sends MPLS echo reply
sends MPLS echo reply with resulting multipath information per with resulting multipath information per downstream (outgoing
downstream (outgoing interface) back to the initiating LSR. interface) back to the initiating LSR. Initiating LSR is then able
Initiating LSR is then able to use specific IP destination address or to use specific IP destination address or specific label to exercise
specific label to exercise 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 Initiating LSR sends IP multipath information, but responder LSR
load balances on labels. load balances on labels.
o Initiating LSR sends label multipath information, but responder o Initiating LSR sends label multipath information, but responder
LSR load balances on IP addresses. LSR load balances on IP addresses.
o Initiating LSR sends existing multipath information to LSR which o Initiating LSR sends existing multipath information to LSR which
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* ELI/EL pushing LSR that is a stitching point will load balance * ELI/EL pushing LSR that is a stitching point will load balance
based on EL from previous LSP and pushes new EL. based on EL from previous LSP and pushes 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 point to how the existing multipath information
is insufficient when LSP traceroute is operated on an LSP with is insufficient when LSP traceroute is operated on an LSP with
Entropy Labels described by [RFC6790]. Therefore, this document Entropy Labels described by [RFC6790]. Therefore, this document
defines a multipath information type to be used in the DSMAP/DDMAP of defines a multipath information type to be used in the DDMAP of MPLS
MPLS echo request/reply packets in Section 9. echo request/reply packets in Section 9.
In addition, responder LSR can reply with empty multipath information In addition, responder LSR can reply with empty multipath information
if no IP address set or label set from received multipath information if no IP address set or label set from received multipath information
matched load balancing to a downstream. Empty return is also matched load balancing to a downstream. Empty return is also
possible if initiating LSR sends multipath information of one type, possible if initiating LSR sends multipath information of one type,
IP address or label, but responder LSR load balances on the other IP address or label, but responder LSR load balances on the other
type. To disambiguate between the two results, this document type. To disambiguate between the two results, this document
introduces new flags in the DSMAP/DDMAP TLV to allow responder LSR to introduces new flags in the DDMAP TLV to allow responder LSR to
describe the load balance technique being used. describe the load balance technique being used.
It is required that all LSRs along the LSP understand new flags as It is required that all LSRs along the LSP understand new flags as
well as new multipath information type. It is also required that well as new multipath information type. It is also required that
initiating LSR can select both IP destination address and label to initiating LSR can select both IP destination address and label to
use on transmitting MPLS echo request packets. Two additional DS use on transmitting MPLS echo request packets. Two additional DS
Flags are defined for the DSMAP and DDMAP TLVs in Section 8. These Flags are defined for the DDMAP TLV in Section 8. These two flags
two flags are used by the responder LSR to describe its load balance are used by the responder LSR to describe its load balance behavior
behavior on received MPLS echo request. on received MPLS echo request.
Note that the terms "IP Based Load Balancer", "Label Based Load Note that the terms "IP Based Load Balancer", "Label Based Load
Balancer" and "Label Based Load Balancer" are in context of how Balancer" and "Label Based Load Balancer" are in context of how
received MPLS echo request is handled by the responder LSR. received MPLS echo request is handled by the responder LSR.
3. Multipath Type 9 3. Multipath Type 9
This section defines to which labels multipath type {9} applies. 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
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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 or DSMAP MUST be set. Note that when a use the N-flag in the DDMAP MUST be set. Note that when a control
control word is not in use the returned DDMAPs or DSMAPs may not be word is not in use the returned DDMAPs may not be accurate.
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
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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, the initiator includes an
EL-FEC at the bottom of the FEC-Stack and pushes the appropriate PW- EL-FEC at the bottom of the FEC-Stack and pushes the appropriate PW-
FEC onto the FEC-Stack. 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 or DSMAP with an MPLS echo request message and includes a DDMAP with multipath type
multipath type {9}. For a non Flow-Aware Pseudowire it includes the {9}. For a non Flow-Aware Pseudowire it includes the appropriate PW-
appropriate PW-FEC in the FEC-Stack. For a Flow Aware Pseudowire, FEC in the FEC-Stack. For a Flow Aware Pseudowire, the initiator
the initiator includes a NIL-FEC at the bottom of the FEC-Stack and includes a NIL-FEC at the bottom of the FEC-Stack and pushes the
pushes the appropriate PW-FEC onto the FEC-Stack. appropriate PW-FEC onto the FEC-Stack.
5. Initiating LSR Procedures 5. Initiating LSR Procedures
In order to facilitate the flow of the following text we speak in In order to facilitate the flow of the following text we speak in
terms of a boolean called EL_LSP maintained by the initiating LSR. terms of a boolean called EL_LSP maintained by the initiating LSR.
This value controls the multipath information type to be used in This value controls the multipath information type to be used in
transmitted echo request packets. When the initiating LSR is transmitted echo request packets. When the initiating LSR is
transmitting an echo request packet with DSMAP/DDMAP with a non-zero transmitting an echo request packet with DDMAP with a non-zero
multipath information type, then EL_LSP boolean MUST be consulted to multipath information type, then EL_LSP boolean MUST be consulted to
determine the multipath information type to use. determine the multipath information type 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], initiating LSR MUST operate with following Section 3 and [RFC6424], initiating LSR MUST operate with following
procedures. 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.
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request received) in the MPLS echo reply packet. 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 Following subsections describe expected responder LSR procedures when
echo reply is to include DSMAP/DDMAP TLVs, based on local load echo reply is to include DDMAP TLVs, based on local load balance
balance technique being employed. In case the responder LSR performs technique being employed. In case the responder LSR performs
deviating load balance techniques per downstream basis, appropriate deviating load balance techniques per downstream basis, appropriate
procedures matching to each downstream load balance technique MUST be procedures matching to each downstream load balance technique MUST be
operated. operated.
6.1. IP Based Load Balancer & Not Pushing ELI/EL 6.1. 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].
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| Label | MBZ | | Label | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Entropy Label FEC Figure 1: Entropy Label FEC
Label is the actual label value inserted in the label stack; the MBZ Label is the actual label value inserted in the label stack; the MBZ
fields MUST be zero when sent and ignored on receipt. fields MUST be zero when sent and ignored on receipt.
8. DS Flags: L and E 8. DS Flags: L and E
Two flags, L and E, are added in DS Flags field of the DSMAP/DDMAP Two flags, L and E, are added in DS Flags field of the DDMAP TLV.
TLVs. Both flags MUST NOT be set in echo request packets when Both flags MUST NOT be set in echo request packets when sending, and
sending, and ignored when received. Zero, one or both new flags MUST ignored when received. Zero, one or both new flags MUST be set in
be set in echo reply packets. echo reply packets.
DS Flags DS Flags
-------- --------
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| MBZ |L|E|I|N| | MBZ |L|E|I|N|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
RFC-Editor-Note: Please update above figure to place the flag E in RFC-Editor-Note: Please update above figure to place the flag E in
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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 label and does not push ELI/ o {L=1, E=0} LSR load balances based on label and does not push ELI/
EL. EL.
o {L=1, E=1} LSR load balances based on label and pushes ELI/EL. o {L=1, E=1} LSR load balances based on label and pushes ELI/EL.
9. New Multipath Information Type: TBD4 9. New Multipath Information Type: TBD4
One new multipath information type is added to be used in DSMAP/DDMAP One new multipath information type is added to be used in DDMAP TLV.
TLVs. New multipath type has value of TBD4. New multipath type has 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. One section to Multipath type TBD4 is comprised of three sections. One section to
describe IP address set. One section to describe label set. One describe IP address set. One section to describe label set. One
section to describe another label set which associates to either IP section to describe another label set which associates to either IP
address set or label set specified in the other section. address set or label set specified in the other section.
 End of changes. 17 change blocks. 
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