draft-akiya-mpls-lsp-ping-reply-mode-simple-02.txt   draft-akiya-mpls-lsp-ping-reply-mode-simple-03.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 (if approved) C. Pignataro
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: November 21, 2014 L. Andersson Expires: January 28, 2015 L. Andersson
M. Chen M. Chen
Huawei Huawei
May 20, 2014 July 27, 2014
Label Switched Path (LSP) Ping/Traceroute Reply Mode Simplification Label Switched Path (LSP) Ping/Traceroute Reply Mode Simplification
draft-akiya-mpls-lsp-ping-reply-mode-simple-02 draft-akiya-mpls-lsp-ping-reply-mode-simple-03
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 adds one value to the
Reply Mode field to indicate reverse LSP. This document also adds an Reply Mode field to indicate reverse LSP. This document also adds an
optional TLV which can carry ordered list of Reply Mode values. optional TLV which can carry ordered list of Reply Mode values.
This document updates RFC4379. This document updates RFC4379.
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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-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 21, 2014. This Internet-Draft will expire on January 28, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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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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 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Reply via reverse LSP . . . . . . . . . . . . . . . . . . 4 3.1. Reply via reverse LSP . . . . . . . . . . . . . . . . . . 5
3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 5 3.2. Reply Mode Order TLV . . . . . . . . . . . . . . . . . . 5
4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 6 4. Relations to Other LSP Ping/Trace Features . . . . . . . . . 6
4.1. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 6 4.1. Reply Path TLV . . . . . . . . . . . . . . . . . . . . . 6
4.2. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 6 4.1.1. Reply Mode Order TLV Usage Example with Reply Path
TLV . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Proxy LSP Ping . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. New Reply Mode . . . . . . . . . . . . . . . . . . . . . 7 6.1. New Reply Mode . . . . . . . . . . . . . . . . . . . . . 8
6.2. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 7 6.2. New Reply Mode Order TLV . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 8 8. Contributing Authors . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Appendix A. Reply Mode Order TLV Beneficial Scenarios . . . . . 9
A.1. Incorrect Forwarding Scenario . . . . . . . . . . . . . . 9
A.2. Non-Co-Routed Bidirectional LSP Scenario . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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 to
encode instructions (Reply Mode) on how a responder should send the encode instructions (Reply Mode) on how a responder should send the
response back to the initiator. [RFC7110] also allows the initiator response back to the initiator. [RFC7110] also allows the initiator
to encode a TLV (Reply Path TLV) which can instruct the responder to to encode a TLV (Reply Path TLV) which can instruct the responder to
use specific LSP to send the response back to the initiator. Both use specific LSP to send the response back to the initiator. Both
approaches are powerful as they provide the ability for the initiator approaches are powerful as they provide the ability for the initiator
to control the return path. to control the return path.
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in a false failure of MPLS LSP Ping and Traceroute operation. In an in a false failure of MPLS LSP Ping and Traceroute operation. In an
effort to minimize such false failures, different implementations effort to minimize such false failures, different implementations
have chosen different default return path encoding for different LSP have chosen different default return path encoding for different LSP
types and LSP operations. The problem with implementations having types and LSP operations. The problem with implementations having
different default return path encoding is that the MPLS echo reply different default return path encoding is that the MPLS echo reply
will not work in many cases, and the default value may not be the will not work in many cases, and the default value may not be the
preferred choice by the operators. preferred choice by the operators.
This document further describes the problem in Section 2, and This document further describes the problem in Section 2, and
proposes a solution in Section 3 to minimizes false failure scenarios proposes a solution in Section 3 to minimizes false failure scenarios
while accommodating operator preferences. while accommodating operator preferences. Additionally, Appendix A
provides 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
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3. Solution 3. Solution
This document adds one reply mode to indicate reverse LSP, to be used This document adds one reply mode to indicate reverse LSP, to be used
by the MPLS LSP Ping and Traceroute. This document also adds an by the MPLS LSP Ping and Traceroute. This document also adds an
optional TLV which can carry ordered list of reply modes. optional TLV which can carry ordered list of reply modes.
3.1. Reply via reverse LSP 3.1. Reply via reverse LSP
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. This direction, through signaling or other association mechanisms.
document uses the term "Reverse LSP" to refer to the LSP in reverse Examples of such LSP types are RSVP LSPs and TP LSPs. This document
direction of such LSP types. Note that this document restricts the uses the term "Reverse LSP" to refer to the LSP in reverse direction
scope of "Reverse LSP" applicability to those reverse LSPs which are of such LSP types. Note that this document restricts the scope of
capable and allowed to carry the IP encapsulated MPLS echo reply. "Reverse LSP" applicability to those reverse LSPs which are capable
and allowed to carry the IP encapsulated MPLS echo reply.
This document adds one Reply Mode to be used by MPLS LSP Ping and This document adds one Reply Mode to be used by MPLS LSP Ping and
Traceroute operations. Traceroute operations.
Value Meaning Value Meaning
----- ------- ----- -------
TBD1 Reply via reverse LSP TBD1 Reply via reverse LSP
MPLS echo request with TBD1 (Reply via reverse LSP) in the Reply Mode MPLS echo request with TBD1 (Reply via reverse LSP) in the Reply Mode
field may be used to instruct responder to use reverse LSP to send field may be used to instruct responder to use reverse LSP to send
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Reply Mode field of received MPLS echo request. 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 node 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 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 which return path was chosen.
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4.1. Reply Path TLV 4.1. Reply Path TLV
[RFC7110] defines a new Reply Mode (5 - Reply via Specified Path). [RFC7110] defines a new Reply Mode (5 - Reply via Specified Path).
This Reply Mode specified in MPLS echo request indicates that MPLS This Reply Mode specified in MPLS echo request indicates that MPLS
echo reply be sent on one specific path described by the Reply Path echo reply be sent on one specific path described by the Reply Path
TLV. The Flags field of the Reply Path TLV can indicate B TLV. The Flags field of the Reply Path TLV can indicate B
(Bidirectional) bit to describe reverse direction of the tested (Bidirectional) bit to describe reverse direction of the tested
bidirectional LSP. However, it is desired to have a new Reply Mode bidirectional LSP. However, it is desired to have a new Reply Mode
(TBD1 - Reply via reverse LSP) to indicate reverse direction of the (TBD1 - Reply via reverse LSP) to indicate reverse direction of the
tested bidirectional LSP without requiring to include additional TLV tested bidirectional LSP without requiring to include additional TLV
(i.e. Reply Path TLV). Therefore, a new Reply Mode (TBD1 - Reply via (i.e. Reply Path TLV). Therefore, a new Reply Mode (TBD1 - Reply
reverse LSP) has been added. via reverse LSP) has been added.
4.1.1. Reply Mode Order TLV Usage Example with Reply Path TLV
If the initiator was interested in encoding following return paths:
1. Reply via application level control channel
2. FEC X
3. FEC Y
4. Reply via an IPv4/IPv6 UDP packet
Then the MPLS echo request message is to carry:
o The Reply Mode Order TLV carrying Reply Modes {4, 5, 2}
o The 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 to
prefer "Reply via application level control channel (4)", followed by
FEC X, FEC Y and then "Reply via an IPv4/IPv6 UDP packet (2)".
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
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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 TBD2 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 and Ross Callon for also like to thank Sam Aldrin, Curtis Villamizar, Ross Callon,
providing valuable comments to influence the contents of the draft. Jeffrey Zhang, Jeremy Whittaker and Mustapha Alissaoui for providing
valuable comments to influence the contents of the draft.
8. Contributing Authors 8. Contributing Authors
Shaleen Saxena Shaleen Saxena
Cisco Systems Cisco Systems
Email: ssaxena@cisco.com Email: ssaxena@cisco.com
9. References 9. References
9.1. Normative References 9.1. Normative References
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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.
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-01 (work in Request", draft-ietf-mpls-proxy-lsp-ping-02 (work in
progress), January 2014. progress), July 2014.
[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, January 2014. RFC 7110, January 2014.
Appendix A. Reply Mode Order TLV Beneficial Scenarios
This section lists examples of how the Reply Mode Order TLV can
benefit.
A.1. Incorrect Forwarding Scenario
A network has a following LSP, and the LSP has a control channel.
A------B------C------D------E
|
|
F
Forward Paths: A-B-C-D-E
Figure 2: Incorrect Forwarding
Imagine that D is incorrectly label switching to F (instead of E).
In this scenario, LSP Traceroute with "Reply via application level
control channel (4)" will result in following result.
Success (Reply from B)
Success (Reply from C)
Success (Reply from D)
Timeout...
Complete
This is because F does not have a control channel to send the MPLS
echo reply message. With the extension described in this document,
same procedures can be performed with the Reply Mode Order TLV
carrying {4, 2}. When LSP Traceroute is issued, then following output
may be displayed without any unnecessary timeout.
Success (Reply from B, Reply Mode: 4)
Success (Reply from C, Reply Mode: 4)
Success (Reply from D, Reply Mode: 4)
FEC Mismatch (Reply from F, Reply Mode: 2)
Complete
The result provides more diagnostic information to the initiator, and
without any delay (i.e. timeout from one or more downstream LSRs).
A.2. Non-Co-Routed Bidirectional LSP Scenario
A network has a following bidirectional LSP where the forward LSP and
the reverse LSP are not fully co-routed.
+----C------D----+
/ \
A------B G------H
\ /
+----E------F----+
Forward Paths: A-B-C-D-G-H (upper path)
Reverse Paths: H-G-F-E-B-A (lower path)
Figure 3: Non-Co-Routed Bidirectional LSP
Some operators may prefer and configure the system to default the
Reply Mode to "Reply via reverse LSP (TBD1)" when MPLS echo request
messages are sent on bidirectional LSPs. Without extensions
described in this document, following behaviors will be seen:
o When LSP Ping is issued from A, reply will come back on the
reverse LSP from H.
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
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
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
has reverse LSP).
One can argue that the initiator can automatically generate a same
MPLS echo request with different Reply Mode value to those nodes that
timeout. However, such mechanism will result in extended time for
the entire operation to complete (i.e. multiple seconds to multiple
minutes). This is undesirable, and perhaps unacceptable if the
"user" is an application.
With the extension described in this document, same procedures can be
performed with the Reply Mode Order TLV carrying {TBD1, 2}. When LSP
Traceroute is issued, then following output may be displayed without
any unnecessary timeout.
Success (Reply Mode: TBD1)
Success (Reply Mode: 2)
Success (Reply Mode: 2)
Success (Reply Mode: TBD1)
Success (Reply Mode: TBD1)
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
Cisco Systems Cisco Systems
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