draft-ietf-mpls-lsp-ping-reply-mode-simple-00.txt   draft-ietf-mpls-lsp-ping-reply-mode-simple-01.txt 
Internet Engineering Task Force N. Akiya Internet Engineering Task Force N. Akiya
Internet-Draft G. Swallow Internet-Draft G. Swallow
Updates: 4379 (if approved) C. Pignataro Updates: 4379,7110 (if approved) C. Pignataro
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: March 9, 2015 L. Andersson Expires: July 9, 2015 L. Andersson
M. Chen M. Chen
Huawei Huawei
September 5, 2014 January 5, 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-00 draft-ietf-mpls-lsp-ping-reply-mode-simple-01
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 adds one value to the be used in the MPLS echo reply. This document updates the "Reply via
Reply Mode field to indicate reverse LSP. This document also adds an Specified Path (5)" Reply Mode value to easily indicate the reverse
optional TLV which can carry ordered list of Reply Mode values. LSP. This document also adds an optional TLV which can carry ordered
list of Reply Mode values.
This document updates RFC4379. This document updates RFC4379 and 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
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 1, line 46 skipping to change at page 1, line 47
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 March 9, 2015. This Internet-Draft will expire on July 9, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Problem Statements . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statements . . . . . . . . . . . . . . . . . . . . . 3
3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Reply via reverse LSP . . . . . . . . . . . . . . . . . . 5 3.1. Reply via Specified Path Update . . . . . . . . . . . . . 5
3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 5 3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 6
4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 6 4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 7
4.1. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 6 4.1. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. Reply Mode Order TLV Usage Example with Reply Path 4.1.1. Example 1: Reply Mode Order TLV Usage with Reply Path
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 7 TLV . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 7 4.1.2. Example 2: Reply Mode Order TLV Usage with Reply Path
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 TLV . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4.2. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 8
6.1. New Reply Mode . . . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6.2. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 6.1. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 9
8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Reply Mode Order TLV Beneficial Scenarios . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 10
A.1. Incorrect Forwarding Scenario . . . . . . . . . . . . . . 9 Appendix A. Reply Mode Order TLV Beneficial Scenarios . . . . . 10
A.2. Non-Co-Routed Bidirectional LSP Scenario . . . . . . . . 10 A.1. Incorrect Forwarding Scenario . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 A.2. Non-Co-Routed Bidirectional LSP Scenario . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The MPLS LSP Ping, described in [RFC4379], allows an initiator to The MPLS LSP Ping, described in [RFC4379], allows an initiator LSR to
encode instructions (Reply Mode) on how a responder should send the encode instructions (Reply Mode) on how a responder LSR should send
response back to the initiator. [RFC7110] also allows the initiator the response back to the initiator LSR. [RFC7110] also allows the
to encode a TLV (Reply Path TLV) which can instruct the responder to initiator LSR to encode a TLV (Reply Path TLV) which can instruct the
use specific LSP to send the response back to the initiator. Both responder LSR to use specific LSP to send the response back to the
approaches are powerful as they provide the ability for the initiator initiator LSR. Both approaches are powerful as they provide the
to control the return path. ability for the initiator LSR to control the return path.
However, it is becoming increasingly difficult for an initiator to However, it is becoming increasingly difficult for an initiator LSR
select a valid return path to encode in the MPLS LSP echo request to select a valid return path to encode in the MPLS LSP echo request
packets. If the initiator does not select a valid return path, the packets. If the initiator LSR does not select a valid return path,
MPLS LSP echo reply will not get back to the initiator. This results the MPLS LSP echo reply will not get back to the initiator LSR. This
in a false failure of MPLS LSP Ping and Traceroute operation. In an results in a false failure of MPLS LSP Ping and Traceroute operation.
effort to minimize such false failures, different implementations In an effort to minimize such false failures, different
have chosen different default return path encoding for different LSP implementations have chosen different default return path encoding
types and LSP operations. The problem with implementations having for different LSP types and LSP operations. The problem with
different default return path encoding is that the MPLS echo reply implementations having different default return path encoding is that
will not work in many cases, and the default value may not be the the MPLS echo reply will not work in many cases, and the default
preferred choice by the operators. value may not be the preferred choice by the operators.
This document further describes the problem in Section 2, and This document describes:
proposes a solution in Section 3 to minimizes false failure scenarios
while accommodating operator preferences. Additionally, Appendix A o In Section 2, further description of the problems;
provides examples of scenarios where the mechanism described in this
document provides benefits. o In Section 3, a solution to minimize false failures while
accommodating operator preferences;
o In Section 4, relationships to other LSP Ping/Traceroute features;
o In Appendix A, examples of scenarios where the mechanism described
in this document provides benefits.
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
the reverse direction, and some do not. the reverse direction, and some do not.
o LSRs on some LSPs can have different available return path(s). o LSRs on some LSPs can have different available return path(s).
Available return path(s) can depend on whether the responder is a Available return path(s) can depend on whether the responder LSR
transit LSR or an egress LSR. In case of a bi-directional LSP, is a transit LSR or an egress LSR. In case of a bi-directional
available return path(s) on transit LSRs can also depend on LSP, available return path(s) on transit LSRs can also depend on
whether LSP is completely co-routed, partially co-routed or whether LSP is completely co-routed, partially co-routed or
associated (i.e., LSPs in the two directions are not co-routed). associated (i.e., LSPs in the two directions are not co-routed).
o MPLS echo request packets may incorrectly terminate on an o MPLS echo request packets may incorrectly terminate on an
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 egress o The MPLS LSP Ping operation is expected to terminate on 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 node does not have an IP Except for the case where the responder LSR does not have an IP route
route back to the initiator, it is possible to use Reply Mode of back to the initiator LSR, it is possible to use the "Reply via an
value 2 (Reply via an IPv4/IPv6 UDP packet) in all cases. However, IPv4/IPv6 UDP packet (2)" Reply Mode value in all cases. However,
some operators are preferring control-channel and reverse LSP as some operators are preferring control-channel and reverse LSP as
default return path if they are available, which is not always the default return path if they are available, which is not always the
case. 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 node 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 often drops such packets. This results in the the responder LSR often drops such packets. This results in the
initiator not receiving the MPLS LSP echo reply packets back. This initiator LSR not receiving the MPLS LSP echo reply packets back.
consequence may be acceptable for failure cases (e.g., broken LSPs) This consequence may be acceptable for failure cases (e.g., broken
where the MPLS echo request terminated on unintended target. LSPs) where the MPLS echo request terminated on unintended target.
However, the initiator not receiving back MPLS echo reply packets, However, the initiator LSR not receiving back MPLS echo reply
even when the intended target received and verified the requests, is packets, even when the intended target received and verified the
not desirable as false failures will be conveyed to users. requests, is not desirable as false failures will be conveyed to
users.
Many operators prefer some return path(s) over others for specific Many operators prefer some return path(s) over others for specific
LSP types. To accommodate this, implementations may default to LSP types. To accommodate this, implementations may default to
operator preferred return path (or allow default return path to be operator preferred return path (or allow default return path to be
configured) for a specific operation. However, if the sender of MPLS configured) for a specific operation. However, if the sender of MPLS
echo request knew that preferred return path will not be available at echo request knew that preferred return path will not be available at
the intended target node, then it is not very beneficial to use a the intended target node, then it is not very beneficial to use a
Reply Mode corresponding to preferred return path (i.e., the sender Reply Mode corresponding to preferred return path (i.e., the sender
of the MPLS echo request will not receive the MPLS echo reply in the of the MPLS echo request will not receive the MPLS echo reply in the
successful case). What would be beneficial, for a given operation, successful case). What would be beneficial, for a given operation,
is for the sender of the MPLS echo request to determine which return is for the sender of the MPLS echo request to determine which return
path(s) can and cannot be used ahead of time. path(s) can and cannot be used ahead of time.
This document adds one Reply Mode value to describe the reverse LSP, This document adds one Reply Mode value to describe the reverse LSP,
and one optional TLV to describe an ordered list of reply modes. and one optional TLV to describe an ordered list of reply modes.
Based on operational needs, the TLV can describe multiple Reply Mode Based on operational needs, the TLV can describe multiple Reply Mode
values in a preferred order to allow the responder to use the first values in a preferred order to allow the responder LSR to use the
available Reply Mode from the list. This eliminates the need for the first available Reply Mode from the list. This eliminates the need
initiator to compute, or sometimes guess, the default return path for the initiator LSR to compute, or sometimes guess, the default
encoding. And that will result in simplified implementations across return path encoding. And that will result in simplified
vendors, and result in improved usability to fit operational needs. implementations across vendors, and result in improved usability to
fit operational needs.
3. Solution 3. Solution
This document adds one reply mode to indicate reverse LSP, to be used This document updates "Reply via Specified Path (5)" Reply Mode to
by the MPLS LSP Ping and Traceroute. This document also adds an easily indicate the reverse LSP. This document also adds an optional
optional TLV which can carry ordered list of reply modes. TLV which can carry ordered list of reply modes.
3.1. Reply via reverse LSP 3.1. Reply via Specified Path Update
Some LSP types are capable of having related LSP in reverse Some LSP types are capable of having related LSP in reverse
direction, through signaling or other association mechanisms. direction, through signaling or other association mechanisms.
Examples of such LSP types are RSVP LSPs and TP LSPs. This document Examples of such LSP types are RSVP LSPs and TP LSPs. This document
uses the term "Reverse LSP" to refer to the LSP in reverse direction uses the term "Reverse LSP" to refer to the LSP in reverse direction
of such LSP types. Note that this document restricts the scope of 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.
This document adds one Reply Mode to be used by MPLS LSP Ping and [RFC7110] has defined the Reply Mode "Reply via Specified Path (5)"
Traceroute operations. which allows the initiator LSR to instruct the responder LSR to send
the MPLS echo reply message on the reverse LSP. However, the
instruction also requires the initiator LSR to include the "Reply
Path TLV" with the B bit (Bidirectional bit) set in the Flags field.
Additionally, [RFC7110] defines the usage of the "Reply via Specified
Path (5)" Reply Mode without inclusion of the "Reply Path TLV" to be
invalid.
Value Meaning This document updates the "Reply via Specified Path (5)" Reply Mode
----- ------- as follows:
TBD1 Reply via reverse LSP
MPLS echo request with TBD1 (Reply via reverse LSP) in the Reply Mode o The usage of the "Reply via Specified Path (5)" without inclusion
field may be used to instruct responder to use reverse LSP to send of a "Reply Path TLV" is no longer invalid.
MPLS echo reply. Reverse LSP is in relation to the last FEC
specified in the Target FEC Stack TLV.
When a responder is using this Reply Mode, transmitting MPLS echo o The usage of the "Reply via Specified Path (5)" without inclusion
of a "Reply Path TLV" implies the reverse LSP. In other words,
the usage of the "Reply via Specified Path (5)" without inclusion
of a "Reply Path TLV" has the same semantics as the usage of the
"Reply via Specified Path (5)" with inclusion of a "Reply Path
TLV" with the B bit set in the Flags field.
Note that the reverse LSP is in relation to the last FEC specified in
the Target FEC Stack TLV.
When a responder LSR is using this Reply Mode, transmitting MPLS echo
reply packet MUST use IP destination address of 127/8 for IPv4 and reply packet MUST use IP destination address of 127/8 for IPv4 and
0:0:0:0:0:FFFF:7F00/104 for IPv6. 0:0:0:0:0:FFFF:7F00/104 for IPv6.
3.2. Reply Mode Order TLV 3.2. Reply Mode Order TLV
This document also introduces a new optional TLV to describe list of This document also introduces a new optional TLV to describe list of
Reply Mode values. The new TLV will contain one or more Reply Mode 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 most value(s) in preferred order. The first Reply Mode value is the most
preferred and the last Reply Mode value is the least preferred. preferred and the last Reply Mode value is the least preferred.
Following rules apply when using Reply Mode Order TLV. Following rules apply when using Reply Mode Order TLV.
1. Reply Mode Order TLV MAY be included in MPLS echo request. 1. Reply Mode Order TLV MAY be included in MPLS echo request.
2. Reply Mode Order TLV MUST NOT be included in MPLS echo reply. 2. Reply Mode Order TLV MUST NOT be included in MPLS echo reply.
3. Reply Mode field of MPLS echo request MUST be set to a valid 3. Reply Mode field of MPLS echo request MUST be set to a valid
value when supplying Reply Mode Order TLV in transmitting MPLS value when supplying Reply Mode Order TLV in transmitting MPLS
echo request. The initiator SHOULD set Reply Mode field of MPLS echo request. The initiator LSR SHOULD set Reply Mode field of
echo request to a value that corresponds to a return path which MPLS echo request to a value that corresponds to a return path
most likely to be available, in case responder does not which most likely to be available, in case the responder LSR does
understand the Reply Mode Order TLV. not understand the Reply Mode Order TLV.
4. If a responder node understands the Reply Mode Order TLV and the 4. If a responder LSR understands the Reply Mode Order TLV and the
TLV is valid, then the responder MUST consider Reply Mode values TLV is valid, then the responder LSR MUST consider Reply Mode
described in the TLV and MUST NOT use the value described in the values described in the TLV and MUST NOT use the value described
Reply Mode field of received MPLS echo request. in the Reply Mode field of received MPLS echo request.
5. If a responder node understands the Reply Mode Order TLV but the 5. If a responder LSR understands the Reply Mode Order TLV but the
TLV is not valid (due to conditions listed below), then the TLV is not valid (due to conditions listed below), then the
responder MUST only use the value described in the Reply Mode responder LSR MUST only use the value described in the Reply Mode
field of received MPLS echo request. field of received MPLS echo request.
6. Reply Mode Order TLV MUST contain at least one Reply Mode value, 6. Reply Mode Order TLV MUST contain at least one Reply Mode value,
and SHOULD contain at least two Reply Mode values. and SHOULD contain at least two Reply Mode values.
7. A Reply Mode value MUST NOT be repeated (i.e. MUST NOT appear 7. A Reply Mode value MUST NOT be repeated (i.e. MUST NOT appear
multiple times) in the Reply Mode Order TLV. multiple times) in the Reply Mode Order TLV.
8. Reply Mode value 1 (Do not reply) SHOULD NOT be used in the Reply 8. Reply Mode value 1 (Do not reply) SHOULD NOT be used in the Reply
Mode Order TLV. Mode Order TLV.
The responding node is to select the first available return path in The responding node is to select the first available return path in
this TLV. Reply Mode value corresponding to selected return path this TLV. Reply Mode value corresponding to selected return path
MUST be set in Reply Mode field of MPLS echo reply to communicate MUST be set in Reply Mode field of MPLS echo reply to communicate
back to the initiator which return path was chosen. 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. Each Reply Mode field is 1
octet. octet.
4. Relations to Other LSP Ping/Trace Features 4. Relations to Other LSP Ping/Trace Features
4.1. Reply Path TLV 4.1. Reply Path TLV
[RFC7110] defines a new Reply Mode (5 - Reply via Specified Path). [RFC7110] has defined that the "Reply Path TLV" can include Sub-TLVs
This Reply Mode specified in MPLS echo request indicates that MPLS describing multiple FECs, from which the responder LSR can chose the
echo reply be sent on one specific path described by the Reply Path FEC to send the MPLS echo reply message on. [RFC7110] has also
TLV. The Flags field of the Reply Path TLV can indicate B defined that Sub-TLVs, within the "Reply Path TLV", describing FECs
(Bidirectional) bit to describe reverse direction of the tested for return paths SHOULD be ignored when the B bit is set in the Flags
bidirectional LSP. However, it is desired to have a new Reply Mode field. Therefore, when the initiator LSR wants to use the Reply Mode
(TBD1 - Reply via reverse LSP) to indicate reverse direction of the Order TLV to describe the reverse LSP and other FECs for return
tested bidirectional LSP without requiring to include additional TLV paths, then the initiator SHOULD include two "Reply via Specified
(i.e. Reply Path TLV). Therefore, a new Reply Mode (TBD1 - Reply Path (5)" Reply Mode values and two "Reply Path TLV" objects (one
via reverse LSP) has been added. "Reply Path TLV" corresponding to each "Reply via Specified Path
(5)").
4.1.1. Reply Mode Order TLV Usage Example with Reply Path TLV o The reverse LSP is described by the "Reply via Specified Path (5)"
Reply Mode value and the corresponding "Reply Path TLV" with the B
bit set in the Flags field. In this "Reply Path TLV", no Sub-TLVs
are present.
If the initiator was interested in encoding following return paths: o Other return FECs are described by the "Reply via Specified Path
(5)" Reply Mode value and the corresponding "Reply Path TLV"
describing the FECs for return paths. In this "Reply Path TLV",
the B bit is cleared in the Flags field.
4.1.1. Example 1: Reply Mode Order TLV Usage with Reply Path TLV
If the initiator LSR was interested in encoding following return
paths:
1. Reply via application level control channel 1. Reply via application level control channel
2. FEC X 2. FEC X
3. FEC Y 3. FEC Y
4. Reply via an IPv4/IPv6 UDP packet 4. Reply via an IPv4/IPv6 UDP packet
Then the MPLS echo request message is to carry: Then the MPLS echo request message is to carry:
o The Reply Mode Order TLV carrying Reply Modes {4, 5, 2} o The Reply Mode Order TLV carrying Reply Modes {4, 5, 2}
o The Reply Path TLV carrying {FEC X, FEC Y} o The Reply Path TLV carrying {FEC X, FEC Y}
Described encoding of the Reply Mode Order TLV and the Reply Path TLV Described encoding of the Reply Mode Order TLV and the Reply Path TLV
in the MPLS echo request message will result in the responder to in the MPLS echo request message will result in the responder LSR to
prefer "Reply via application level control channel (4)", followed by prefer "Reply via application level control channel (4)", followed by
FEC X, FEC Y and then "Reply via an IPv4/IPv6 UDP packet (2)". FEC X, FEC Y and then "Reply via an IPv4/IPv6 UDP packet (2)".
4.1.2. Example 2: Reply Mode Order TLV Usage with Reply Path TLV
If the initiator LSR was interested in encoding following return
paths:
1. Reverse LSP
2. Reply via an IPv4/IPv6 UDP packet
3. FEC X
4. FEC Y
Then the MPLS echo request message is to carry:
o The Reply Mode Order TLV carrying Reply Modes {5, 2, 5}
o One Reply Path TLV with the B bit set.
o One Reply Path TLV carrying {FEC X, FEC Y}
Described encoding of the Reply Mode Order TLV and the Reply Path TLV
in the MPLS echo request message will result in the responder LSR to
prefer the reverse LSP, followed by "Reply via an IPv4/IPv6 UDP
packet (2)", FEC X and then FEC Y.
4.2. Proxy LSP Ping 4.2. Proxy LSP Ping
The mechanism defined in this document will work with Proxy LSP Ping The mechanism defined in this document will work with Proxy LSP Ping
defined by [I-D.ietf-mpls-proxy-lsp-ping]. MPLS proxy ping request defined by [I-D.ietf-mpls-proxy-lsp-ping]. MPLS proxy ping request
can carry a Reply Mode value and the Reply Mode Order TLV with list can carry a Reply Mode value and the Reply Mode Order TLV with list
of Reply Mode values. Proxy LSR MUST copy both Reply Mode value and of Reply Mode values. Proxy LSR MUST copy both Reply Mode value and
the Reply Mode Order TLV into MPLS echo request. Proxy LSR, upon the Reply Mode Order TLV into MPLS echo request. Proxy LSR, upon
receiving MPLS echo reply, MUST copy Reply Mode value into MPLS proxy receiving MPLS echo reply, MUST copy Reply Mode value into MPLS proxy
ping reply. With these procedures, Reply Mode used by the MPLS echo ping reply. With these procedures, Reply Mode used by the MPLS echo
reply sender is propagated in the Reply Mode field to the sender of reply sender is propagated in the Reply Mode field to the sender of
MPLS proxy ping request. MPLS proxy ping request.
5. Security Considerations 5. Security Considerations
Beyond those specified in [RFC4379], there are no further security Beyond those specified in [RFC4379], there are no further security
measures required. measures required.
6. IANA Considerations 6. IANA Considerations
6.1. New Reply Mode
IANA is requested to assign one reply modes from the "Reply Mode" 6.1. New Reply Mode Order TLV
sub-registry within the "Multiprotocol Label Switching Architecture
(MPLS)" registry.
Value Meaning Reference
----- ------- ---------
TBD1 Reply via reverse LSP this document
6.2. New Reply Mode Order TLV
IANA is requested to assign a new TLV type value from the "TLVs" sub- IANA is requested to assign a new TLV type value from the "TLVs" sub-
registry within the "Multiprotocol Label Switching Architecture registry within the "Multiprotocol Label Switching Architecture
(MPLS)" registry, for the "Reply Mode Order TLV". (MPLS)" registry, for the "Reply Mode Order TLV".
The new TLV Type value should be assigned from the range The new TLV Type value should be assigned from the range
(32768-49161) specified in [RFC4379] section 3 that allows the TLV (32768-49161) specified in [RFC4379] section 3 that allows the TLV
type to be silently dropped if not recognized. type to be silently dropped if not recognized.
Type Meaning Reference Type Meaning Reference
---- ------- --------- ---- ------- ---------
TBD2 Reply Mode Order TLV this document TBD1 Reply Mode Order TLV this document
7. Acknowledgements 7. Acknowledgements
Authors would like to thank Santiago Alvarez and Faisal Iqbal for Authors would like to thank Santiago Alvarez and Faisal Iqbal for
discussions which motivated creation of this document. Authors would discussions which motivated creation of this document. Authors would
also like to thank Sam Aldrin, Curtis Villamizar, Ross Callon, also like to thank Sam Aldrin, Curtis Villamizar, Ross Callon,
Jeffrey Zhang, Jeremy Whittaker and Mustapha Alissaoui for providing Jeffrey Zhang, Jeremy Whittaker and Mustapha Alissaoui for providing
valuable comments to influence the contents of the draft. valuable comments to influence the contents of the draft.
8. Contributing Authors 8. Contributing Authors
Shaleen Saxena Shaleen Saxena
Cisco Systems Brocade
Email: ssaxena@cisco.com Email: ssaxena@brocade.com
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[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,
February 2006. February 2006.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, January 2014.
9.2. Informative References 9.2. Informative References
[I-D.ietf-mpls-proxy-lsp-ping] [I-D.ietf-mpls-proxy-lsp-ping]
Swallow, G., Lim, V., and S. Aldrin, "Proxy MPLS Echo Swallow, G., Lim, V., and S. Aldrin, "Proxy MPLS Echo
Request", draft-ietf-mpls-proxy-lsp-ping-02 (work in Request", draft-ietf-mpls-proxy-lsp-ping-02 (work in
progress), July 2014. progress), July 2014.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, January 2014.
Appendix A. Reply Mode Order TLV Beneficial Scenarios Appendix A. Reply Mode Order TLV Beneficial Scenarios
This section lists examples of how the Reply Mode Order TLV can This section lists examples of how the Reply Mode Order TLV can
benefit. benefit.
A.1. Incorrect Forwarding Scenario A.1. Incorrect Forwarding Scenario
A network has a following LSP, and the LSP has a control channel. A network has a following LSP, and the LSP has a control channel.
A------B------C------D------E A------B------C------D------E
skipping to change at page 10, line 7 skipping to change at page 11, line 7
same procedures can be performed with the Reply Mode Order TLV same procedures can be performed with the Reply Mode Order TLV
carrying {4, 2}. When LSP Traceroute is issued, then following output carrying {4, 2}. When LSP Traceroute is issued, then following output
may be displayed without any unnecessary timeout. may be displayed without any unnecessary timeout.
Success (Reply from B, Reply Mode: 4) Success (Reply from B, Reply Mode: 4)
Success (Reply from C, Reply Mode: 4) Success (Reply from C, Reply Mode: 4)
Success (Reply from D, Reply Mode: 4) Success (Reply from D, Reply Mode: 4)
FEC Mismatch (Reply from F, Reply Mode: 2) FEC Mismatch (Reply from F, Reply Mode: 2)
Complete Complete
The result provides more diagnostic information to the initiator, and The result provides more diagnostic information to the initiator LSR,
without any delay (i.e. timeout from one or more downstream LSRs). and without any delay (i.e. timeout from one or more downstream
LSRs).
A.2. Non-Co-Routed Bidirectional LSP Scenario A.2. Non-Co-Routed Bidirectional LSP Scenario
A network has a following bidirectional LSP where the forward LSP and A network has a following bidirectional LSP where the forward LSP and
the reverse LSP are not fully co-routed. the reverse LSP are not fully co-routed.
+----C------D----+ +----C------D----+
/ \ / \
A------B G------H A------B G------H
\ / \ /
+----E------F----+ +----E------F----+
Forward Paths: A-B-C-D-G-H (upper path) Forward Paths: A-B-C-D-G-H (upper path)
Reverse Paths: H-G-F-E-B-A (lower path) Reverse Paths: H-G-F-E-B-A (lower path)
Figure 3: Non-Co-Routed Bidirectional LSP Figure 3: Non-Co-Routed Bidirectional LSP
Some operators may prefer and configure the system to default the Some operators may prefer and configure the system to default the
Reply Mode to "Reply via reverse LSP (TBD1)" when MPLS echo request Reply Mode to indicate the reverse LSP when MPLS echo request
messages are sent on bidirectional LSPs. Without extensions messages are sent on bidirectional LSPs. Without extensions
described in this document, following behaviors will be seen: described in this document, following behaviors will be seen:
o When LSP Ping is issued from A, reply will come back on the o When LSP Ping is issued from A, reply will come back on the
reverse LSP from H. reverse LSP from H.
o When LSP Traceroute is issued from A, reply will come back on the o When LSP Traceroute is issued from A, reply will come back on the
reverse LSP from B, G and H, but will encounter a timeout from C reverse LSP from B, G and H, but will encounter a timeout from C
and D as there are no reverse LSP on those nodes. and D as there are no reverse LSP on those nodes.
o When LSP Ping with specific TTL value is issued from A, whether a o When LSP Ping with specific TTL value is issued from A, whether a
timeout will be encountered depends on the value of the TTL used timeout will be encountered depends on the value of the TTL used
(i.e. whether or not MPLS echo request terminates on a node that (i.e. whether or not MPLS echo request terminates on a node that
has reverse LSP). has reverse LSP).
One can argue that the initiator can automatically generate a same One can argue that the initiator LSR can automatically generate a
MPLS echo request with different Reply Mode value to those nodes that same MPLS echo request with different Reply Mode value to those nodes
timeout. However, such mechanism will result in extended time for that timeout. However, such mechanism will result in extended time
the entire operation to complete (i.e. multiple seconds to multiple for the entire operation to complete (i.e. multiple seconds to
minutes). This is undesirable, and perhaps unacceptable if the multiple minutes). This is undesirable, and perhaps unacceptable if
"user" is an application. the "user" is an application.
With the extension described in this document, same procedures can be With the extension described in this document, same procedures can be
performed with the Reply Mode Order TLV carrying {TBD1, 2}. When LSP performed with the Reply Mode Order TLV carrying {5, 2}. When LSP
Traceroute is issued, then following output may be displayed without Traceroute is issued, then following output may be displayed without
any unnecessary timeout. any unnecessary timeout.
Success (Reply Mode: TBD1) Success (Reply Mode: 5)
Success (Reply Mode: 2) Success (Reply Mode: 2)
Success (Reply Mode: 2) Success (Reply Mode: 2)
Success (Reply Mode: TBD1) Success (Reply Mode: 5)
Success (Reply Mode: TBD1) Success (Reply Mode: 5)
Complete Complete
Authors' Addresses Authors' Addresses
Nobo Akiya Nobo Akiya
Cisco Systems Cisco Systems
Email: nobo@cisco.com Email: nobo@cisco.com
George Swallow George Swallow
 End of changes. 47 change blocks. 
141 lines changed or deleted 193 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/