draft-ietf-mpls-lsp-ping-ttl-tlv-02.txt   draft-ietf-mpls-lsp-ping-ttl-tlv-03.txt 
Network Working Group Siva Sivabalan (Ed.) Network Working Group Sami Boutros
Internet Draft Sami Boutros (Ed.) INTERNET-DRAFT Siva Sivabalan
Intended status: Standards Track George Swallow Intended Status: Standards Track George Swallow
Expires: September 2012 Shaleen Saxena Shaleen Saxena
Cisco Systems, Inc. Cisco Systems
Vishwas Manral Vishwas Manral
IPInfusion, Inc. Netplane Systems
Sam Aldrin Sam Aldrin
Huawei Technologies, Inc. Huawei Technologies, Inc.
March 7, 2012 Expires: March 13, 2013 September 9, 2012
Definition of Time-to-Live TLV for LSP-Ping Mechanisms Definition of Time-to-Live TLV for LSP-Ping Mechanisms
draft-ietf-mpls-lsp-ping-ttl-tlv-02.txt draft-ietf-mpls-lsp-ping-ttl-tlv-03.txt
Abstract Abstract
LSP-Ping is a widely deployed Operation, Administration, and LSP-Ping is a widely deployed Operation, Administration, and
Maintenance (OAM) mechanism in MPLS networks. However, in the present Maintenance (OAM) mechanism in MPLS networks. However, in the present
form, this mechanism is inadequate to verify connectivity of a form, this mechanism is inadequate to verify connectivity of a
segment of a Multi-Segment PseudoWire (MS-PW) from any node on the segment of a Multi-Segment PseudoWire (MS-PW) from any node on the
path of the MS-PW. This document defines a TLV to address this path of the MS-PW. This document defines a TLV to address this
shortcoming. shortcoming.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119 [3].
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 7, 2012. Copyright and License Notice
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology....................................................3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Time To Live TLV...............................................4 3. Time To Live TLV . . . . . . . . . . . . . . . . . . . . . . . 4
4. Operation......................................................4 3.1. TTL TLV Format . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations........................................5 3.2. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations............................................5 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. References.....................................................5 4.1. Traceroute mode . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References......................................5 4.2. Error scenario . . . . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References.........Error! Bookmark not defined. 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
Author's Addresses................................................7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1 Normative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
A MS-PW can span across multiple service provider networks. In A MS-PW can span across multiple service provider networks. In order
order to allow Service Providers (SP) to verify segments of such MS- to allow Service Providers (SP) to verify segments of such MS-PW from
PW from any node on the path of the MS-PW, any node along the path of any node on the path of the MS-PW, any node along the path of the MS-
the MS-PW, should be able to originate an LSP-Ping echo request PW, should be able to originate an LSP-Ping echo request packet to
packet to any another node along the path of the MS-PW and receive any another node along the path of the MS-PW and receive the
the corresponding echo reply. If the originator of the echo request corresponding echo reply. If the originator of the echo request is at
is at the end of a MS-PW, the receiver of the request can send the the end of a MS-PW, the receiver of the request can send the reply
reply back to the sender without knowing the hop-count distance of back to the sender without knowing the hop-count distance of the
the originator. For example, the reply will be intercepted by the originator. For example, the reply will be intercepted by the
originator regardless of the TTL value on the reply packet. But, if originator regardless of the TTL value on the reply packet. But, if
the originator is not at the end of the MS-PW, the receiver of the the originator is not at the end of the MS-PW, the receiver of the
echo request MAY need to know how many hops away the originator of echo request MAY need to know how many hops away the originator of
the echo request is so that it can set the TTL value on the MPLS the echo request is so that it can set the TTL value on the MPLS
header for the echo reply to be intercepted at the originator node. header for the echo reply to be intercepted at the originator node.
In MPLS networks (also applicable to MPLS-TP), for bidirectional co- In MPLS networks, for bidirectional co-routed LSPs, if it is desired
routed LSPs, if it is desired to verify connectivity from any to verify connectivity from any intermediate node (LSR) on the LSP to
intermediate node (LSR) on the LSP to the any other LSR on the LSP the any other LSR on the LSP the receiver may need to know the TTL to
the receiver may need to know the TTL to send the Echo reply with, so send the Echo reply with, so as the packet is intercepted by the
as the packet is intercepted by the originator node. originator node.
A new optional TTL TLV is being proposed in this document this TLV A new optional TTL TLV is being proposed in this document this TLV
will be added by the originator of the echo request to inform the will be added by the originator of the echo request to inform the
receiver how many hops away the originator is on the path of the MS- receiver how many hops away the originator is on the path of the MS-
PW or Bidirectional LSP. PW or Bidirectional LSP.
Conventions used in this document The scope of this TTL TLV is currently limited to MS-PW or
Bidirectional co-routed MPLS LSPs.
2. Terminology
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-2119Error! document are to be interpreted as described in RFC 2119 [RFC2119].
Reference source not found.
2. Terminology
LSR: Label Switching Router LSR: Label Switching Router
MPLS-OAM: MPLS Operations, Administration and Maintenance MPLS-OAM: MPLS Operations, Administration and Maintenance
MPLS-TP: MPLS Transport Profile MPLS-TP: MPLS Transport Profile
MS-PW: Multi-Segment PseudoWire MS-PW: Multi-Segment PseudoWire
PW: PseudoWire PW: PseudoWire
skipping to change at page 3, line 43 skipping to change at page 4, line 4
MPLS-OAM: MPLS Operations, Administration and Maintenance MPLS-OAM: MPLS Operations, Administration and Maintenance
MPLS-TP: MPLS Transport Profile MPLS-TP: MPLS Transport Profile
MS-PW: Multi-Segment PseudoWire MS-PW: Multi-Segment PseudoWire
PW: PseudoWire PW: PseudoWire
TLV: Type Length Value TLV: Type Length Value
TTL: Time To Live TTL: Time To Live
3. Time To Live TLV 3. Time To Live TLV
0 1 2 3 3.1. TTL TLV Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| type = TBD | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| value |
+-+-+-+-+-+-+-+-+
Figure 1: Time To Live TLV format 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value | Reserved | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Time To Live TLV format
The TTL TLV has the format shown in Figure 1. This TLV shall be The TTL TLV has the format shown in Figure 1.
included in the echo request by the originator of request. The use of
this TLV is optional. If the value field is zero, the LSP Ping Echo
request packet will be dropped.
If a receiver does not understand the TTL TLV, it will simply ignore Value
the TLV (Type value of TLV is assumed to be in the range of optional
TLVs which SHOULD be ignored if an implementation does not support or The value of the TTL as specified by this TLV
understand them). In the absence of TTL TLV or if TTL TLV is ignored
by a receiver, the determination of the TTL value used in the MPLS Flags
label on the echo reply is beyond the scope of this document.
The Flags field is a bit vector with the following format:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ |R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
One flag is defined for now, the R bit; the rest MUST be set
to zero when sending and ignored on receipt.
The R flag (Reply TTL) is set signify that the value is
meant to be used as the TTL for the reply packet. Other bits
may be defined later to enhance the scope of this TLV.
3.2. Usage
This TLV shall be included in the echo request by the originator of
request. The use of this TLV is optional. If a receiver does not
understand the TTL TLV, it will simply ignore the TLV (Type value of
TLV is assumed to be in the range of optional TLV's which SHOULD be
ignored if an implementation does not support or understand them). In
the absence of TTL TLV or if TTL TLV is ignored by a receiver, the
determination of the TTL value used in the MPLS label on the echo
reply is beyond the scope of this document.
If a receiver understands the TTL TLV, and the TTL TLV is present in If a receiver understands the TTL TLV, and the TTL TLV is present in
the echo request, the receiver MUST use the TTL value specified in the echo request, and if the value field is zero, the LSP Ping Echo
TLV in the MPLS header of the echo reply. request packet SHOULD be dropped.
In the traceroute mode TTL value in the TLV is successively set to 1, If a receiver understands the TTL TLV, and the TTL TLV is present in
2, and so on. the echo request, the receiver MUST use the TTL value specified in
TLV in the MPLS header of the echo reply. In other words, if the
value of the TTL provided by this TLV does not match the TTL
determined by other means, such as Switching Point TLV in MS-PW, then
TTL TLV must be used. This will aid the originator of the echo
request in analyzing the return path.
4. Operation 4. Operation
In this section, we explain a use case for the TTL TLV with an MPLS In this section, we explain a use case for the TTL TLV with an MPLS
MS-PW. MS-PW.
<------------------MS-PW --------------------->
<------------------MS-PW ---------------------> A B C D E
o -------- o -------- o --------- o --------- o
A B C D E ------Echo Request----->
o -------- o -------- o --------- o --------- o <-----Echo Reply--------
------Echo Request----->
<-----Echo Reply--------
Figure 2: Use-case with MS-PWs Figure 2: Use-case with MS-PWs
Let us assume a MS-PW going through LSRs A, B, C, D, and E. Let us assume a MS-PW going through LSRs A, B, C, D, and E.
Furthermore, assume that an operator wants to perform a connectivity Furthermore, assume that an operator wants to perform a connectivity
check between B and D from B. Thus, an LSP-Ping request with the TTL check between B and D from B. Thus, an LSP-Ping request with the TTL
TLV is originated from B and sent towards D. The echo request packet TLV is originated from B and sent towards D. The echo request packet
contains the FEC of the PW Segment between C and D. The value field contains the FEC of the PW Segment between C and D. The value field
of the TTL TLV and the TTL field of the MPLS label are set to 2. The of the TTL TLV and the TTL field of the MPLS label are set to 2. The
echo request is intercepted at D because of TTL expiry. D detects the echo request is intercepted at D because of TTL expiry. D detects the
TTL TLV in the request, and use the TTL value (i.e., 2) specified in TTL TLV in the request, and use the TTL value (i.e., 2) specified in
the TLV on the MPLS label of the echo reply. The echo reply will be the TLV on the MPLS label of the echo reply. The echo reply will be
intercepted by B because of TTL expiry. intercepted by B because of TTL expiry.
The same operation will apply in the case a co-routed bidirectional The same operation will apply in the case a co-routed bidirectional
LSP and we want to check connectivity from an intermediate LSR B to LSP and we want to check connectivity from an intermediate LSR B to
another LSR D, from B. another LSR D, from B.
4.1. Traceroute mode
In the traceroute mode TTL value in the TLV is successively set to 1,
2, and so on. This is similar to the TTL values used for the label
set on the packet.
4.2. Error scenario
It is possible that the echo request packet was punted before the
intended destination. This could be due network faults,
misconfiguration or other reasons. In such cases, if the return TTL
is set to the value specified in the TTL TLV then the echo response
packet will continue beyond the originating node. This becomes a
security issue.
To prevent this issue, the TTL value used must be modified by
deducting the incoming label TTL. If the echo request packet is
punted before the incoming TTL is deducted, then another 1 must be
deducted. In other words:
Return TTL Value = (TTL TLV Value)-(Incoming Label TTL) + 1
5. Security Considerations 5. Security Considerations
This draft allows the setting of the TTL value in the MPLS Label of This draft allows the setting of the TTL value in the MPLS Label of
an echo reply, so that it can be intercepted by an intermediate an echo reply, so that it can be intercepted by an intermediate
device. This can cause a device to get a lot of LSP Ping packets device. This can cause a device to get a lot of LSP Ping packets
which get redirected to the CPU. which get redirected to the CPU.
However the same is possible even without the changes mentioned in However the same is possible even without the changes mentioned in
this document. A device should rate limit the LSP ping packets this document. A device should rate limit the LSP ping packets
redirected to the CPU so that the CPU is not overwhelmed. redirected to the CPU so that the CPU is not overwhelmed.
6. IANA Considerations 6. IANA Considerations
IANA is requested to assign TLV type value to the following TLV from IANA is requested to assign TLV type value to the following TLV from
the "Multiprotocol Label Switching Architecture (MPLS) Label Switched the "Multiprotocol Label Switching Architecture (MPLS) Label Switched
Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-TLVs" sub- Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-TLVs" sub-
registry. registry.
Time To Live TLV (See Section 3). Time To Live TLV (See Section 3). The Suggested value is 32769 as
suggested by RFC 4379 Section 3.
7. References 7. Acknowledgements
7.1. Normative References The authors would like to thank Greg Mirsky for his comments.
[1] K. Kompella, G. Swallow, "Detecting Multi-Protocol Label 8. References
Switched (MPLS) Data Plane Failures", RFC 4379, February
2006.
[2] T. Nadeau, et. al, "Pseudowire Virtual Circuit Connectivity 8.1 Normative References
Verification (VCCV): A Control Channel for Pseudowires ", RFC
5085, December 2007.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] K. Kompella, G. Swallow, "Detecting Multi-Protocol Label Switched
Levels", BCP 14, RFC 2119, March 1997. (MPLS) Data Plane Failures", RFC 4379, February 2006.
Author's Addresses [2] T. Nadeau, et. al, "Pseudowire Virtual Circuit Connectivity
Verification (VCCV): A Control Channel for Pseudowires ", RFC 5085,
December 2007.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Siva Sivabalan Siva Sivabalan
Cisco Systems, Inc. Cisco Systems, Inc.
2000 Innovation Drive 2000 Innovation Drive
Kanata, Ontario, K2K 3E8 Kanata, Ontario, K2K 3E8
Canada Canada
Email: msiva@cisco.com Email: msiva@cisco.com
Sami Boutros Sami Boutros
Cisco Systems, Inc. Cisco Systems, Inc.
skipping to change at page 7, line 34 skipping to change at page 8, line 4
Boxborough , MASSACHUSETTS 01719 Boxborough , MASSACHUSETTS 01719
United States United States
Email: swallow@cisco.com Email: swallow@cisco.com
Shaleen Saxena Shaleen Saxena
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Avenue 1414 Massachusetts Avenue
Boxborough , MASSACHUSETTS 01719 Boxborough , MASSACHUSETTS 01719
United States United States
Email: ssaxena@cisco.com Email: ssaxena@cisco.com
Vishwas Manral Vishwas Manral
IPInfusion, Inc. Netplane Systems
1188 E. Arques Ave., 189 Prashasan Nagar
Sunnyvale, CA 94085 Road number 72
Jubilee Hills
Hyderabad, India
vmanral@netplane.com
Michael Wildt
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough , MASSACHUSETTS 01719
United States United States
Email: vishwas@ipinfusion.com Email: mwildt@cisco.com
Sam Aldrin Sam Aldrin
Huawei Technologies, Inc. Huawei Technologies, Inc.
1188 Central Express Way, 1188 Central Express Way,
Santa Clara, CA 95051 Santa Clara, CA 95051
United States United States
Email: aldrin.ietf@gmail.com Email: aldrin.ietf@gmail.com
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