Network Working Group Parag Jain, Ed.
Internet Draft Sami Boutros
Intended status: Standards Track Cisco Systems, Inc.
Expires: January 10, 2014
Sam Aldrin
Huawei Technologies
July 9, 2013
Definition of P2MP PW TLV for LSP-Ping Mechanisms
draft-jain-pwe3-p2mp-pw-lsp-ping-02.txt
Abstract
LSP-Ping is a widely deployed Operation, Administration, and
Maintenance (OAM) mechanism in MPLS networks. This document
describes a mechanism to verify connectivity of Point-to-Multipoint
(P2MP) Pseudowires (PW) using LSP Ping.
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Table of Contents
1. Introduction 2
2. Conventions used in this document 3
3. Terminology 3
4. Identifying a P2MP PW 3
4.1. FEC 130 Pseudowire Sub-TLV 4
5. Operations 4
6. Echo Reply using Downstream Assigned Label 6
7. Controlling Echo Responses 6
8. Security Considerations 6
9. IANA Considerations 6
10. References 6
10.1. Normative References 6
10.2. Informative References 7
11. Acknowledgments 7
1. Introduction
A Point-to-Multipoint (P2MP) Pseudowire (PW) emulates the essential
attributes of a unidirectional P2MP Telecommunications service such
as P2MP ATM over PSN. Requirements for P2MP PW are described in
[PPWREQ]. P2MP PWs are carried over P2MP MPLS LSP. The Procedure for
P2MP PW signaling using LDP for single segment P2MP PWs are
described in [PPWPWE3]. Many P2MP PWs can share the same P2MP MPLS
LSP and this arrangement is called Aggregate P-tree. The aggregate
P2MP trees require an upstream assigned label so that on the tail of
the P2MP LSP, the traffic can be associated with a VPN or a VPLS
instance. When a P2MP MPLS LSP carries only one VPN or VPLS service
instance, the arrangement is called Inclusive P-Tree. For Inclusive
P-Trees, P2MP MPLS LSP label itself can uniquely identify the VPN or
VPLS service being carried over P2MP MPLS LSP. The P2MP MPLS LSP can
also be used in Selective P-Tree arrangement for carrying multicast
traffic. In a Selective P-Tree arrangement, traffic to each
multicast group in a VPN or VPLS instance is carried by a separate
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unique P-tree. In Aggregate Selective P-tree arrangement, traffic to
a set of multicast groups from different VPN or VPLS instances is
carried over a same shared P-tree.
The P2MP MPLS LSP are setup either using MLDP [RFC6388] or P2MP RSVP-TE
[RFC4875]. Mechanisms for fault detection and isolation for data
plane failures for P2MP MPLS LSPs are specified in [RFC6425]. This
document describes a mechanism to detect data plane failures for
P2MP PW carried over P2MP MPLS LSPs.
This document defines a new FEC 130 Pseudowire sub-TLV for Target
FEC Stack for P2MP PW. The FEC 130 Pseudowire sub-TLV is added in
Target FEC Stack TLV by the originator of the echo request to inform
the receiver at P2MP MPLS LSP tail, of the P2MP PW being tested.
Multi-segment Pseudowires support is out of scope of this document
at present and may be included in future.
2. Conventions used in this document
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].
The term "FEC-Type" is used to refer to a tuple consisting of <FEC
Element Type, Address Family>.
3. Terminology
ATM: Asynchronous Transfer Mode
LSR: Label Switching Router
MPLS-OAM: MPLS Operations, Administration and Maintenance
P2MP-PW: Point-to-Multipoint PseudoWire
PW: PseudoWire
TLV: Type Length Value
4. Identifying a P2MP PW
This document introduces a new LSP Ping Target FEC Stack sub-TLV,
FEC 130 Pseudowire sub-TLV, to identify the P2MP PW under test at
the P2MP LSP Tail/Bud node.
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4.1. FEC 130 Pseudowire Sub-TLV
The FEC 130 Pseudowire sub-TLV fields are taken from P2MP PW FEC
Element (FEC Type 0x82) defined in [PPWPWE3]. The PW Type is a 15-
bit number indicating the encapsulation type. It is carried right
justified in the field below PW Type with the high-order bit set to
zero. All the other fields are treated as opaque values and copied
directly from P2MP PW FEC Element (FEC Type 0x82) format.
The FEC 130 Pseudowire sub-TLV has the format shown in Figure 1.
This TLV will be included in the echo request sent over P2MP PW by
the originator of request.
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| PW Type | AGI Type | AGI Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ AGI Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII Type | SAII Length | SAII Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ SAII Value (continued) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: FEC 130 Pseudowire sub-TLV format
For Inclusive and Selective P2MP MPLS P-trees, the echo request will
be sent using the P2MP MPLS LSP label.
For Aggregate Inclusive and Aggregate Selective P-trees, the echo
request will be sent using a label stack of <P2MP MPLS P-tree label,
upstream assigned P2MP PW label>. The P2MP MPLS P-tree label is the
outer label and upstream assigned P2MP PW label is inner label.
5. Operations
In this section, we explain the operation of the LSP Ping over P2MP
PW. Figure 2 shows a P2MP PW PW1 setup from T-PE1 to remote PEs (T-
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PE2, T-PE3 and T-PE4). The transport LSP associated with the P2MP PW1
can be MLDP P2MP MPLS LSP or P2MP TE tunnel.
|<--------------P2MP PW---------------->|
Native | | Native
Service | |<--PSN1->| |<--PSN2->| | Service
(AC) V V V V V V (AC)
| +-----+ +------+ +------+ |
| | | | P1 |=========|T-PE2 |AC3 | +---+
| | | | .......PW1.........>|-------->|CE3|
| |T-PE1|=========| . |=========| | | +---+
| | .......PW1........ | +------+ |
| | . |=========| . | +------+ |
| | . | | . |=========|T-PE3 |AC4 | +---+
+---+ |AC1 | . | | .......PW1.........>|-------->|CE4|
|CE1|------->|... | | |=========| | | +---+
+---+ | | . | +------+ +------+ |
| | . | +------+ +------+ |
| | . |=========| P2 |=========|T-PE4 |AC5 | +---+
| | .......PW1..............PW1.........>|-------->|CE5|
| | |=========| |=========| | | +---+
| +-----+ +------+ +------+ |
Figure 2: P2MP PW
When an operator wants to perform a connectivity check for the P2MP
PW1, the operator initiate a LSP-Ping request with the Target FEC
Stack TLV containing FEC 130 Pseudowire sub-TLV in the echo request
packet. The echo request packet is sent over the P2MP MPLS LSP using
the P2MP MPLS LSP label for Inclusive P-tree or with a label stack
with Upstream assigned P2MP PW label as bottom label and P2MP MPLS
LSP label as the top label. The intermediate P router will do swap
and replication based on the MPLS LSP label. Once the packet reaches
remote terminating PEs, the T-PEs will process the packet and perform
checks for the FEC 130 Pseudowire sub-TLV present in the Target FEC
Stack TLV as described in Section 4.4 in [RFC4379] and respond
according to [RFC4379] processing rules.
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6. Echo Reply using Downstream Assigned Label
Root of a P2MP PW may send an optional downstream assigned p2p MPLS
label in the LDP Label Mapping message for the P2MP PW signaling. If
the root of a P2MP PW expects leaf to send echo reply using the
downstream assigned label signaled in the Label Mapping message of
the P2MP PW message, the Reply Mode value of 4 "Reply via
application level control channel" should be used in Reply Mode
field described in Section 3 in [RFC4379] in echo request message
for the P2MP PW.
7. Controlling Echo Responses
The procedures described in [RFC6425] for preventing congestion of
Echo Responses (Echo Jitter TLV) and limiting the echo reply to a
single egress node (Node Address P2MP Responder Identifier TLV) can
be applied to P2MP PW LSP Ping.
8. Security Considerations
The proposal introduced in this document does not introduce any new
security considerations beyond that already apply to [RFC6425].
9. IANA Considerations
This document defines a new sub-TLV type to be included in Target
FEC Stack TLV (TLV Type 1) [RFC4379] in LSP Ping.
IANA is requested to assign a sub-TLV type value to the following
sub-TLV from the "Multiprotocol Label Switching (MPLS) Label
Switched Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-
TLVs" sub-registry.
FEC 130 Pseudowire sub-TLV (See Section 3). Suggested value 24.
10. References
10.1. Normative References
[RFC4379] K. Kompella, G. Swallow, "Detecting Multi-Protocol Label
Switched (MPLS) Data Plane Failures", RFC 4379, February
2006.
[PPWPWE3] Martini, L. et. al, "Signaling Root-Initiated Point-to-
Multipoint Pseudowires using LDP", draft-ietf-pwe3-p2mp-
pw-04.txt, Work in Progress, March 2012.
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[RFC6425] Saxena, S et. Al, "Detecting Data Plane Failures in Point-
to-Multipoint Multiprotocol Label Switching (MPLS) -
Extensions to LSP. RFC 6425, November 2011
10.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC2119, March 1997.
[RFC5085] T. Nadeau, et. al, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires ", RFC 5085, December 2007.
[RFC6388] Wijnands, I., Minei, I., Kompella, K., and Thomas, B.,
"LDP Extensions for Point-to-Multipoint and Multipoint-to-
Multipoint Label Switched Paths", RFC 6388, November 2011.
[RFC4875] Aggarwal, R., Papadimitriou, D., and Yasukawa, S.,
"Extensions to Resource Reservation Protocol" Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[PPWREQ] F. Jounay, et. al, "Requirements for Point to Multipoint
Pseudowire", draft-ietf-pwe3-p2mp-pw-requirements-05.txt,
Work in Progress, September 2011.
11. Acknowledgments
The authors would like to thank Shaleen Saxena, Michael Wildt,
Tomofumi Hayashi, Danny Prairie for their valuable input and
comments.
This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses
Parag Jain
Cisco Systems, Inc.,
2000 Innovation Drive,
Kanata, ON K2K3E8, Canada.
E-mail: paragj@cisco.com
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Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way,
San Jose, CA 95134, USA.
E-mail: sboutros@cisco.com
Sam Aldrin
Huawei Technologies, co.
2330 Central Express Way,
Santa Clara, CA 95051, USA.
E-mail: aldrin.ietf@gmail.com
Jain Expires January 2014 [Page 8]
