draft-ietf-mpls-lsp-ping-reply-mode-simple-04.txt   draft-ietf-mpls-lsp-ping-reply-mode-simple-05.txt 
Internet Engineering Task Force N. Akiya Internet Engineering Task Force N. Akiya
Internet-Draft Big Switch Networks Internet-Draft Big Switch Networks
Updates: 7110 (if approved) G. Swallow Updates: 7110 (if approved) G. Swallow
Intended status: Standards Track C. Pignataro Intended status: Standards Track C. Pignataro
Expires: March 16, 2016 Cisco Systems Expires: April 10, 2016 Cisco Systems
L. Andersson L. Andersson
M. Chen M. Chen
Huawei Huawei
September 13, 2015 October 8, 2015
Label Switched Path (LSP) Ping/Traceroute Reply Mode Simplification Label Switched Path (LSP) Ping/Traceroute Reply Mode Simplification
draft-ietf-mpls-lsp-ping-reply-mode-simple-04 draft-ietf-mpls-lsp-ping-reply-mode-simple-05
Abstract Abstract
The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP)
Ping and Traceroute use the Reply Mode field to signal the method to Ping and Traceroute use the Reply Mode field to signal the method to
be used in the MPLS echo reply. This document updates the "Reply via be used in the MPLS echo reply. This document updates the procedures
Specified Path (5)" Reply Mode value to easily indicate the reverse for the "Reply via Specified Path" Reply Mode, the value of this
LSP. This document also adds an optional TLV which can carry ordered Reply Mode is 5. The update creates a simple way to indicate that
list of Reply Mode values. the Reverse LSP should be used as return path. This document also
adds an optional TLV which can carry ordered list of Reply Mode
values.
This document updates RFC7110. This document updates RFC7110.
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
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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 April 10, 2016.
This Internet-Draft will expire on March 16, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statements . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statements . . . . . . . . . . . . . . . . . . . . . 3
3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Reply via Specified Path Update . . . . . . . . . . . . . 5 3.1. Reply via Specified Path Update . . . . . . . . . . . . . 5
3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 6 3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 6
4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 8 4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 8
4.1. Backwards Compatibility with Reply via Specified Path (5) 4.1. Backwards Compatibility with Reply via Specified Path
Reply Mode . . . . . . . . . . . . . . . . . . . . . . . 8 Reply Mode . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 8 4.2. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Example 1: Reply Mode Order TLV Usage with Reply Path 4.2.1. Example 1: Reply Mode Order TLV Usage with Reply Path
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 9 TLV . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2.2. Example 2: Reply Mode Order TLV Usage with Reply Path 4.2.2. Example 2: Reply Mode Order TLV Usage with Reply Path
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 9 TLV . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 10 4.3. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 10
4.3.1. Proxy LSR Sending an MPLS Echo Request . . . . . . . 10 4.3.1. Proxy LSR Sending an MPLS Echo Request . . . . . . . 10
4.3.2. Proxy LSR Sending an MPLS Proxy Ping Reply . . . . . 10 4.3.2. Proxy LSR Sending an MPLS Proxy Ping Reply . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Manageability Considerations . . . . . . . . . . . . . . . . 10 6. Manageability Considerations . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 11 7.1. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 12 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . 12 10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 12 10.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Reply Mode Order TLV Beneficial Scenarios . . . . . 12 Appendix A. Reply Mode Order TLV Beneficial Scenarios . . . . . 13
A.1. Incorrect Forwarding Scenario . . . . . . . . . . . . . . 13 A.1. Incorrect Forwarding Scenario . . . . . . . . . . . . . . 14
A.2. Non-Co-Routed Bidirectional LSP Scenario . . . . . . . . 13 A.2. Non-Co-Routed Bidirectional LSP Scenario . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP)
Ping, described in [RFC4379], allows an initiator LSR to encode Ping, described in [RFC4379], allows an initiator LSR to encode
instructions (Reply Mode) on how a responder LSR should send the instructions (Reply Mode) on how a responder LSR should send the
response back to the initiator LSR. [RFC7110] also allows the response back to the initiator LSR. [RFC7110] also allows the
initiator LSR to encode a TLV (Reply Path TLV) which can instruct the initiator LSR to encode a TLV (Reply Path TLV) which can instruct the
responder LSR to use a specific LSP to send the response back to the responder LSR to use a specific LSP to send the response back to the
initiator LSR. Both approaches are powerful as they provide the initiator LSR. Both approaches are powerful as they provide the
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o In Section 2, further description of the problems; o In Section 2, further description of the problems;
o In Section 3, a solution to minimize false failures while o In Section 3, a solution to minimize false failures while
accommodating operator preferences; accommodating operator preferences;
o In Section 4, relationships to other LSP Ping/Traceroute features; o In Section 4, relationships to other LSP Ping/Traceroute features;
o In Appendix A, examples of scenarios where the mechanism described o In Appendix A, examples of scenarios where the mechanism described
in this document provides benefits. in this document provides benefits.
This documents updates [RFC7110] by allowing the usage of the Reply This document updates [RFC7110] by allowing the usage of the "Reply
Mode value 5 (Reply via Specified Path) without including the Reply via Specified Path" (value=5) Reply Mode without including the Reply
Path TLV. Path TLV. The update creates a simple way to indicate that the
Reverse LSP should be used as return path.
2. Problem Statements 2. Problem Statements
It is becoming increasingly difficult for implementations to It is becoming increasingly difficult for implementations to
automatically supply a workable return path encoding for all MPLS LSP automatically supply a workable return path encoding for all MPLS LSP
Ping and Traceroute operations across all LSP types. There are Ping and Traceroute operations across all LSP types. There are
several factors which are contributing to this complication. several factors which are contributing to this complication.
o Some LSPs have a control-channel, and some do not. Some LSPs have o Some LSPs have a control-channel, and some do not. Some LSPs have
a reverse LSP, and some do not. Some LSPs have IP reachability in a reverse LSP, and some do not. Some LSPs have IP reachability in
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unintended target, which can have different available return unintended target, which can have different available return
path(s) than the intended target. path(s) than the intended target.
o The MPLS LSP Ping operation is expected to terminate on an egress o The MPLS LSP Ping operation is expected to terminate on an egress
LSR. However, the MPLS LSP Ping operation with specific TTL LSR. However, the MPLS LSP Ping operation with specific TTL
values and MPLS LSP Traceroute operation can terminate on both values and MPLS LSP Traceroute operation can terminate on both
transit LSR(s) and the egress LSR. transit LSR(s) and the egress LSR.
Except for the case where the responder LSR does not have an IP route Except for the case where the responder LSR does not have an IP route
back to the initiator LSR, it is possible to use the "Reply via an back to the initiator LSR, it is possible to use the "Reply via an
IPv4/IPv6 UDP packet (2)" Reply Mode value in all cases. However, IPv4/IPv6 UDP packet" (value=2) Reply Mode value in all cases.
some operators are preferring control-channel and reverse LSP as However, some operators are preferring control-channel and reverse
default return path if they are available, which is not always the LSP as default return path if they are available, which is not always
case. the case.
When specific return path encoding is supplied by users or When specific return path encoding is supplied by users or
applications, then there are no issues in choosing the return path applications, then there are no issues in choosing the return path
encoding. When specific return path encoding is not supplied by encoding. When specific return path encoding is not supplied by
users or applications, then implementations use extra logic to users or applications, then implementations use extra logic to
compute, and sometimes guess, the default return path encodings. If compute, and sometimes guess, the default return path encodings. If
a responder LSR receives an MPLS echo request containing return path a responder LSR receives an MPLS echo request containing return path
instructions which cannot be accommodated due to unavailability, then instructions which cannot be accommodated due to unavailability, then
the responder LSR often drops such packets. This failure mode the responder LSR often drops such packets. This failure mode
results in the initiator LSR not receiving the intended MPLS LSP echo results in the initiator LSR not receiving the intended MPLS LSP echo
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for particular operations, or allow a default return path to be for particular operations, or allow a default return path to be
configured. It would not be considered beneficial to use a preferred configured. It would not be considered beneficial to use a preferred
return path for an intended target LSR if there is previous knowledge return path for an intended target LSR if there is previous knowledge
at the initiator LSR that the return path is not available. Using a at the initiator LSR that the return path is not available. Using a
unavailable preferred return path would undesirably result in the unavailable preferred return path would undesirably result in the
initiator LSR not receiving the MPLS echo return packets. It would initiator LSR not receiving the MPLS echo return packets. It would
be considered beneficial, for given operations, if the sender of the be considered beneficial, for given operations, if the sender of the
MPLS echo request would be able to determined return path MPLS echo request would be able to determined return path
availability before the operation is initiated. availability before the operation is initiated.
This document updates the "Reply via Specified Path (5)" Reply Mode This document updates the procedures for "Reply via Specified Path"
to easily indicate the reverse the reverse LSP, and adds one optional Reply Mode to easily indicate the reverse LSP, and adds one optional
TLV to describe an ordered list of reply modes. Based on operational TLV to describe an ordered list of Reply Modes. Based on operational
needs, the TLV can describe multiple Reply Mode values in a preferred needs, the TLV can describe multiple Reply Mode values in a preferred
order to allow the responder LSR to use the first available Reply order to allow the responder LSR to use the first available Reply
Mode from the list. This eliminates the need for the initiator LSR Mode from the list. This eliminates the need for the initiator LSR
to compute, or sometimes guess, the default return path encoding. to compute, or sometimes guess, the default return path encoding.
This new mode of operation would resulted in a simplification to This new mode of operation would resulted in a simplification to
implementations across the various vendors and improve both usability implementations across the various vendors and improve both usability
and operational needs. and operational needs.
3. Solution 3. Solution
This document updates the "Reply via Specified Path (5)" Reply Mode This document updates the procedures for "Reply via Specified Path"
to easily indicate the reverse LSP. This document also adds an Reply Mode to easily indicate the reverse LSP. This document also
optional TLV which can carry an ordered list of reply modes. adds an optional TLV which can carry an ordered list of Reply Modes.
3.1. Reply via Specified Path Update 3.1. Reply via Specified Path Update
Some LSP types are capable of having a related LSP in reverse Some LSP types are capable of having a related LSP in reverse
direction, through signaling or other association mechanisms. direction, through signaling or other association mechanisms.
Examples of such LSP types are bidirectional Resource ReserVation Examples of such LSP types are bidirectional Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) LSPs [RFC3473] and MPLS Protocol-Traffic Engineering (RSVP-TE) LSPs [RFC3473] and MPLS
Transport Profile (MPLS-TP) LSPs ([RFC5960]). This document uses the Transport Profile (MPLS-TP) LSPs ([RFC5960]). This document uses the
term "Reverse LSP" to refer to the LSP in the reverse direction of term "Reverse LSP" to refer to the LSP in the reverse direction of
such LSP types. Note that this document restricts the scope of such LSP types. Note that this document restricts the scope of
"Reverse LSP" applicability to those reverse LSPs which are capable "Reverse LSP" applicability to those reverse LSPs which are capable
and allowed to carry the IP encapsulated MPLS echo reply. and allowed to carry the IP encapsulated MPLS echo reply.
[RFC7110] has defined the Reply Mode "Reply via Specified Path (5)" [RFC7110] has defined the Reply Mode "Reply via Specified Path" which
which allows the initiator LSR to instruct the responder LSR to send allows the initiator LSR to instruct the responder LSR to send the
the MPLS echo reply message on the reverse LSP. However, the MPLS echo reply message on the reverse LSP. However, the instruction
instruction also requires the initiator LSR to include the "Reply also requires the initiator LSR to include the "Reply Path TLV" with
Path TLV" with the B bit (Bidirectional bit) set in the Flags field. the B bit (Bidirectional bit) set in the Flags field. Additionally,
Additionally, [RFC7110] defines the usage of the "Reply via Specified [RFC7110] defines that if the "Reply via Specified Path" Reply Mode
Path (5)" Reply Mode without inclusion of the "Reply Path TLV" to be is used the "Reply Path TLV" MUST present.
invalid.
This document updates the "Reply via Specified Path (5)" Reply Mode This document updates the procedures for "Reply via Specified Path"
as follows: Reply Mode as follows:
o The usage of the "Reply via Specified Path (5)" without inclusion o The "Reply via Specified Path" MAY be used without including a
of a "Reply Path TLV" is no longer invalid. "Reply Path TLV".
o The usage of the "Reply via Specified Path (5)" without inclusion o The usage of the "Reply via Specified Path" without inclusion of a
of a "Reply Path TLV" implies the reverse LSP. In other words, "Reply Path TLV" implies the reverse LSP. In other words, the
the usage of the "Reply via Specified Path (5)" without inclusion usage of the "Reply via Specified Path" without inclusion of a
of a "Reply Path TLV" has the same semantics as the usage of the "Reply Path TLV" has the same semantics as the usage of the "Reply
"Reply via Specified Path (5)" with inclusion of a "Reply Path via Specified Path" with inclusion of a "Reply Path TLV" with the
TLV" with the B bit set in the Flags field. B bit set in the Flags field.
Specific to section 5.1 of [RFC7110], this document updates the first
sentence as follows:
o When sending an echo request, in addition to the rules and
procedures defined in Section 4.3 of [RFC4379], the Reply Mode of
the echo request MUST be set to "Reply via Specified Path", and a
Reply Path TLV SHOULD be carried in the echo request message
correspondingly; if the Reply Path TLV is not carried, then it
indicates the reverse LSP as the reply path.
Note that the reverse LSP is in relation to the last FEC specified in Note that the reverse LSP is in relation to the last FEC specified in
the Target FEC Stack TLV. the Target FEC Stack TLV.
3.2. Reply Mode Order TLV 3.2. Reply Mode Order TLV
This document also introduces a new optional TLV to describe a list This document also introduces a new optional TLV to describe a list
of Reply Mode values. The new TLV will contain one or more Reply of Reply Mode values. The new TLV will contain one or more Reply
Mode value(s) in preferred order. The first Reply Mode value is the Mode value(s) in preferred order. The first Reply Mode value is the
most preferred and the last Reply Mode value is the least preferred. most preferred and the last Reply Mode value is the least preferred.
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path MUST be set in Reply Mode field of the MPLS echo reply to path MUST be set in Reply Mode field of the MPLS echo reply to
communicate back to the initiator LSR which return path was chosen. communicate back to the initiator LSR which return path was chosen.
The format of the TLV is as follows: The format of the TLV is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reply Mode Order TLV Type | Length | | Reply Mode Order TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Reply mode 1 | Reply mode 2 | Reply mode 3 | Reply mode 4 ~ ~ Reply Mode 1 | Reply Mode 2 | Reply Mode 3 | Reply Mode 4 ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 Reply Mode Order TLV Figure 1 Reply Mode Order TLV
This is a variable length optional TLV. Each Reply Mode field is 1 This is a variable length optional TLV. The Reply Mode Order TLV
octet. Type is TBD1.
The Length field is 2 octets in length. It defines the length in
octets of the list of Reply Mode values.
Each Reply Mode field is 1 octet, and there is no padding.
4. Relations to Other LSP Ping/Trace Features 4. Relations to Other LSP Ping/Trace Features
4.1. Backwards Compatibility with Reply via Specified Path (5) Reply 4.1. Backwards Compatibility with Reply via Specified Path Reply Mode
Mode
[RFC7110] has introduced the "Reply via Specified path (5)" Reply [RFC7110] introduces the "Reply via Specified Path" (value=5) Reply
Mode, and defined that usage of the "Reply via Specified path (5)" Mode. The RFC also defines that if this Reply Mode is used, the
Reply Mode without also including the "Reply Path TLV" to be invalid. "Reply Path TLV" MUST be included. This document relaxes the
This document relaxes this semantic by defining the use of the "Reply semantics and defines that this Reply Mode MAY be used without the
via Specified path (5)" Reply Mode without the "Reply via Specified "Reply Path TLV". This MAY be done to indicate that the reverse LSP
path (5)" to indicate the reverse LSP. In other words, what was SHALL be used as he return path.
considered invalid is now valid. If the initiator LSR, which sent an
MPLS echo request message with the "Reply via Specified path (5)" If the initiator LSR, which sent an MPLS echo request message with
Reply Mode but without including the "Reply Path TLV", receives back the "Reply via Specified Path" Reply Mode but without including the
an MPLS echo reply message with the return code being "Malformed echo "Reply Path TLV", receives back an MPLS echo reply message with the
request received", then the initiator LSR SHOULD assume that the return code being "Malformed echo request received", then the
responder LSR does not support the mechanism defined in this initiator LSR SHOULD assume that the responder LSR does not support
document. the mechanism defined in this document.
4.2. Reply Path TLV 4.2. Reply Path TLV
A "Reply Path TLV" [RFC7110] is defined to identify a single return A "Reply Path TLV" [RFC7110] is defined to identify a single return
path. When the initiator LSR wants to use the Reply Mode Order TLV path. When the initiator LSR wants to use the Reply Mode Order TLV
to describe multiple return paths, then the initiator SHOULD include to describe multiple return paths, then the initiator SHOULD include
multiple "Reply via Specified Path (5)" Reply mode values and multiple "Reply via Specified Path" (value=5) Reply Mode values and
multiple corresponding "Reply Path TLV" objects (one "Reply Path TLV" multiple corresponding "Reply Path TLV" objects (one "Reply Path TLV"
corresponding to a "Reply via Specified Path (5)" Reply mode, and one corresponding to a "Reply via Specified Path" Reply Mode, and one
"Reply Path TLV" identifies a return path). "Reply Path TLV" identifies a return path).
As described in Section 3.1, it's valid to use the "Reply via As described in Section 3.1, it's valid to use the "Reply via
Specified Path (5)" Reply mode without inclusion a "Reply Path TLV". Specified Path" Reply Mode without inclusion a "Reply Path TLV". For
For the Reply Mode Order TLV, it's also valid to include a "Reply via the Reply Mode Order TLV, it's also valid to include a "Reply via
Specified Path (5)" Reply mode value without a corresponding "Reply Specified Path" Reply Mode value without a corresponding "Reply Path
Path TLV", this implies that the reverse LSP is the preferred return TLV", this implies that the reverse LSP is the preferred return path.
path. When multiple consecutive "Reply via Specified Path (5)" Reply When multiple consecutive "Reply via Specified Path" Reply Mode
mode values are included but less corresponding "Reply Path TLV" values are included but less corresponding "Reply Path TLV" objects
objects exist, the responder LSR SHOULD think that the former "Reply exist, the responder LSR SHOULD think that the former "Reply via
via Specified Path (5)" Reply mode values have corresponding "Reply Specified Path" Reply Mode values have corresponding "Reply Path
Path TLV", the latter "Reply via Specified Path (5)" Reply mode TLV", the latter "Reply via Specified Path" Reply Mode values have no
values have no corresponding "Reply Path TLV". For example, if the corresponding "Reply Path TLV". For example, if the Reply Mode Order
Reply Mode Order TLV carrying Reply Modes {5, 5, 5} and only two TLV carrying Reply Modes {5, 5, 5} and only two Reply Path TLVs
Reply Path TLVs carrying FEC X and FEC Y respectively. The reply carrying FEC X and FEC Y respectively. The reply path order is as
path order is as follows: follows:
1. Reply via Specified Path (FEC X) 1. Reply via Specified Path (FEC X)
2. Reply via Specified Path (FEC Y) 2. Reply via Specified Path (FEC Y)
3. Reply via Specified Path (Reverse LSP) 3. Reply via Specified Path (Reverse LSP)
4.2.1. Example 1: Reply Mode Order TLV Usage with Reply Path TLV 4.2.1. Example 1: Reply Mode Order TLV Usage with Reply Path TLV
If the initiator LSR was interested in encoding following return If the initiator LSR was interested in encoding following return
paths: paths:
1. Reply via application level control channel 1. Reply via application level control channel
2. FEC X 2. FEC X
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TLVs, then order of them MUST be preserved when copying. TLVs, then order of them MUST be preserved when copying.
4.3.2. Proxy LSR Sending an MPLS Proxy Ping Reply 4.3.2. Proxy LSR Sending an MPLS Proxy Ping Reply
If the proxy LSR is sending an MPLS proxy ping reply, then it is If the proxy LSR is sending an MPLS proxy ping reply, then it is
RECOMMENDED that the Reply Mode Order TLV is ignored and the Reply RECOMMENDED that the Reply Mode Order TLV is ignored and the Reply
Mode field in the MPLS proxy ping request message is used. Mode field in the MPLS proxy ping request message is used.
5. Security Considerations 5. Security Considerations
Beyond those specified in [RFC4379] and [RFC7110], there are no Those security considerations specified in [RFC4379] and [RFC7110]
further security measures required. apply for this document.
In addition, this document introduces the Reply Mode Order TLV. It
provides a new way for an unauthorized source to gather more network
information, especially the potential return path(s) information of
an LSP. To protect against unauthorized sources using MPLS echo
request messages with the Reply Mode Order TLV to obtain network
information, similar to [RFC4379], it is RECOMMENDED that
implementations provide a means of checking the source addresses of
MPLS echo request messages against an access list before accepting
the message.
Another potential security issue is that the MPLS echo request and
reply messages are not encrypted, the content of the MPLS echo
request and reply messages may be potentially exposed. Although the
exposure is within the MPLS domain, if such exposure is a concern,
some encryption mechanisms [I-D.ietf-mpls-opportunistic-encrypt] may
be employed.
6. Manageability Considerations 6. Manageability Considerations
Section 2 described the problems which increases the complexity with Section 2 described the problems which increases the complexity with
respect to operations and implementations. In order to simplify respect to operations and implementations. In order to simplify
operations and to allow for the LSP Ping/Traceroute to function operations and to allow for the LSP Ping/Traceroute to function
efficiently whilst preserving the code simplicity, it is RECOMMENDED efficiently whilst preserving the code simplicity, it is RECOMMENDED
that implementations allow devices to have configuration options to that implementations allow devices to have configuration options to
set operator preferred Reply Modes. For example: set operator preferred Reply Modes. For example:
skipping to change at page 12, line 32 skipping to change at page 13, line 23
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>.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping", "Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, DOI 10.17487/RFC7110, January 2014, RFC 7110, DOI 10.17487/RFC7110, January 2014,
<http://www.rfc-editor.org/info/rfc7110>. <http://www.rfc-editor.org/info/rfc7110>.
10.2. Informative References 10.2. Informative References
[I-D.ietf-mpls-opportunistic-encrypt]
Farrel, A. and S. Farrell, "Opportunistic Security in MPLS
Networks", draft-ietf-mpls-opportunistic-encrypt-00 (work
in progress), July 2015.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol- Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473, Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003, DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>. <http://www.rfc-editor.org/info/rfc3473>.
[RFC5960] Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS [RFC5960] Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
Transport Profile Data Plane Architecture", RFC 5960, Transport Profile Data Plane Architecture", RFC 5960,
DOI 10.17487/RFC5960, August 2010, DOI 10.17487/RFC5960, August 2010,
<http://www.rfc-editor.org/info/rfc5960>. <http://www.rfc-editor.org/info/rfc5960>.
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