BESS Workgroup P. Jain
Internet-Draft S. Boutros
Intended status: Standards Track Cisco Systems, Inc.
Expires: September 9, 2015 March 8, 2015
Definition of P2MP PW TLV for LSP-Ping Mechanisms
draft-jain-bess-p2mp-pw-lsp-ping-00
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. Specification of Requirements . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Identifying a P2MP PW . . . . . . . . . . . . . . . . . . . . 3
4.1. FEC 130 Pseudowire Sub-TLV . . . . . . . . . . . . . . . 3
5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Encapsulation of OAM Ping Packets . . . . . . . . . . . . . . 5
7. Echo Reply using Downstream Assigned Label . . . . . . . . . 6
8. Controlling Echo Responses . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
12.1. Normative References . . . . . . . . . . . . . . . . . . 6
12.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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
[RFC7338]. P2MP PWs are carried over P2MP MPLS LSP. The Procedure
for P2MP PW signaling using LDP for single segment P2MP PWs are
described in [I-D.ietf-pwe3-p2mp-pw]. 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 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.
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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. Specification of Requirements
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 [RFC2119].
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.
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 [I-D.ietf-pwe3-p2mp-pw]. 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.
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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-
PE2, T-PE3 and T-PE4). The transport LSP associated with the P2MP
PW1 can be MLDP P2MP MPLS LSP or P2MP TE tunnel.
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|<--------------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 inner 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.
6. Encapsulation of OAM Ping Packets
The LSP Ping Echo request IPv4/UDP packets will be encapsulated with
the MPLS label stack as described in previous sections, followed by
the GAL Label [RFC6426]. The GAL label will be followed by the ACH
with the Pseudowire Associated Channel Type 16 bit value in the ACH
set to IPv4 indicating that the carried packet is an IPv4 packet.
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7. 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.
8. 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.
9. Security Considerations
The proposal introduced in this document does not introduce any new
security considerations beyond that already apply to [RFC6425].
10. 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:
o FEC 130 Pseudowire sub-TLV (See Section 3). Suggested value 24.
11. Acknowledgments
The authors would like to thank Shaleen Saxena, Michael Wildt,
Tomofumi Hayashi, Danny Prairie for their valuable input and
comments.
12. References
12.1. Normative References
[I-D.ietf-pwe3-p2mp-pw]
Sivabalan, S., Boutros, S., and L. Martini, "Signaling
Root-Initiated Point-to-Multipoint Pseudowire using LDP",
draft-ietf-pwe3-p2mp-pw-04 (work in progress), March 2012.
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[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC6425] Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa,
S., and T. Nadeau, "Detecting Data-Plane Failures in
Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC
6425, November 2011.
[RFC6426] Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
On-Demand Connectivity Verification and Route Tracing",
RFC 6426, November 2011.
12.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
[RFC7338] Jounay, F., Kamite, Y., Heron, G., and M. Bocci,
"Requirements and Framework for Point-to-Multipoint
Pseudowires over MPLS Packet Switched Networks", RFC 7338,
September 2014.
Authors' Addresses
Parag Jain
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, ON K2K-3E8
Canada
Email: paragj@cisco.com
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Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way
San Jose, CA 95134
USA
Email: sboutros@cisco.com
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