Network Working Group S. Boutros, Ed.
Internet-Draft S. Sivabalan, Ed.
Intended status: Standards Track Cisco Systems
Expires: June 12, 2011 V. Manral, Ed.
IPInfusion Inc.
G. Swallow
S. Saxena
Cisco Systems
December 09, 2010
Definition of Time-to-Live TLV for LSP-Ping Mechanisms
draft-boutros-mpls-lsp-ping-ttl-tlv-02
Abstract
LSP-Ping is a widely deployed Operation, Administration, and
Maintenance (OAM) mechanism in MPLS networks. However, in the
present form, this mechanism is inadequate to verify connectivity of
a 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
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 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 12, 2011.
Copyright Notice
Boutros, et al. Expires June 12, 2011 [Page 1]
Internet-Draft LSP-Ping TTL TLV December 2010
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Time to Live (TTL) . . . . . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Boutros, et al. Expires June 12, 2011 [Page 2]
Internet-Draft LSP-Ping TTL TLV December 2010
1. Introduction
A MS-PW can span across multiple service provider networks. In order
to allow Service Providers (SP) to verify segments of such MS-PW from
any node on the path of the MS-PW, any node along the path of the
MS-PW, should be able to originate an LSP-Ping echo request packet to
any another node along the path of the MS-PW and receive the
corresponding echo reply. If the originator of the echo request is
at the end of a MS-PW, the receiver of the request can send the reply
back to the sender without knowing the hop-count distance of the
originator. For example, the reply will be intercepted by the
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
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
header for the echo reply to be intercepted at the originator node.
In MPLS networks (also applicable to MPLS-TP) for bidirectional co-
routed LSPs, if it is desired to verify connectivity from any
intermediate node (LSR) on the LSP to the any other LSR on the LSP
the receiver may need to know the TTL to send the Echo reply with, so
as the packet is intercepted by the originator node.
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
receiver how many hops away the originator is on the path of the
MS-PW or Bidirectional LSP.
2. Terminology
LSR: Label Switching Router
MPLS-OAM: MPLS Operations, Administration and Maintenance
MPLS-TP: MPLS Transport Profile
MS-PW: Multi-Segment PseudoWire
PW: PseudoWire
TLV: Type Length Value
TTL: Time To Live
Boutros, et al. Expires June 12, 2011 [Page 3]
Internet-Draft LSP-Ping TTL TLV December 2010
3. Time to Live (TTL)
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 |
+-+-+-+-+-+-+-+-+
Figure 1: Time To Live TLV format
The TTL TLV has the format shown in Figure 1. This TLV shall be
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
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
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
the echo request, the receiver MUST use the TTL value specified in
TLV in the MPLS header of the echo reply.
In the traceroute mode TTL value in the TLV is successively set to 1,
2, and so on.
4. Operation
In this section, we explain a use case for the TTL TLV with an MPLS
MS-PW.
<------------------MS-PW --------------------->
A B C D E
o -------- o -------- o --------- o --------- o
------Echo Request----->
<-----Echo Reply--------
Figure 2: Use-case with MS-PWs
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
check between B and D from B. Thus, an LSP-Ping request with the TTL
Boutros, et al. Expires June 12, 2011 [Page 4]
Internet-Draft LSP-Ping TTL TLV December 2010
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
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 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 intercepted by B because of TTL expiry.
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
another LSR D, from B.
5. Security Considerations
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
device. This can cause a device to get a lot of LSP Ping packets
which get redirected to the CPU.
However the same is possible even without the changes mentioned in
this document. A device should rate limit the LSP ping packets
redirected to the CPU so that the CPU is not overwhelmed.
6. IANA Considerations
IANA is requested to assign TLV type value to the following TLV from
the "Multiprotocol Label Switching Architecture (MPLS) Label Switched
Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-TLVs" sub-
registry.
Optional Time To Live TLV (See Section 3). The Suggested value is
32769 as suggested by RFC 4379 Section 3.
7. Acknowledgements
The authors would like to thank Greg Mirsky, Laxmi Narasimaha Reddy
Devireddy and Mahesh Akula for their comments.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Boutros, et al. Expires June 12, 2011 [Page 5]
Internet-Draft LSP-Ping TTL TLV December 2010
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
8.2. Informative References
Authors' Addresses
Sami Boutros (editor)
Cisco Systems
3750 Cisco Way
San Jose, CA 95134
US
Phone: undefined
Fax:
Email: sboutros@cisco.com
URI:
Siva Sivabalan (editor)
Cisco Systems
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Phone: undefined
Fax:
Email: msiva@cisco.com
URI:
Vishwas Manral (editor)
IPInfusion Inc.
1188 E. Arques Ave.
Sunnyvale, CA 94085
USA
Phone: 408-400-1900
Fax:
Email: vishwas@ipinfusion.com
URI:
Boutros, et al. Expires June 12, 2011 [Page 6]
Internet-Draft LSP-Ping TTL TLV December 2010
George Swallow
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
USA
Phone: undefined
Fax:
Email: swallow@cisco.com
URI:
Shaleen Saxena
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
USA
Phone: undefined
Fax:
Email: ssaxena@cisco.com
URI:
Boutros, et al. Expires June 12, 2011 [Page 7]