MPLS Working Group F. Zhang
Internet-Draft B. Wu
Intended status: Informational X. Dai
Expires: April 18, 2010 ZTE Corporation
October 15, 2009
LDP Extensions for MPLS-TP PW OAM configuration
draft-zhang-mpls-tp-pw-oam-config-00
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Abstract
This document describes a procedure for the configuration of the
pseudo wire (PW) virtual circuit connectivity verification (VCCV)
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Bidirectional Forwarding Detection (BFD) OAM mechanism through LDP
extensions. As the other MPLS-TP PW OAM functionalities develop, the
procedure may be changed to cover them.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. LDP extensions . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Operation overviews . . . . . . . . . . . . . . . . . . . 4
3.2. OAM configuration TLV . . . . . . . . . . . . . . . . . . 4
3.3. BFD CC OAM Configuration TLV . . . . . . . . . . . . . . . 5
3.3.1. Local Discriminator sub-TLV . . . . . . . . . . . . . 6
3.4. BFD CC&CV OAM Configuration TLV . . . . . . . . . . . . . 6
3.4.1. MEP_IDs . . . . . . . . . . . . . . . . . . . . . . . 7
3.4.2. ME_IDs . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4.2.1. IP Compatible ME-IDs . . . . . . . . . . . . . . . 8
3.4.2.2. ICC-based ME_IDs . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative references . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document describes a procedure for the configuration of the PW
VCCV BFD OAM mechanism through LDP extensions. As the other MPLS-TP
PW OAM functionalities develop, the procedure may be changed to cover
them.
PW VCCV provides end-to-end fault detection and diagnostics for PWs,
and currently supports the following OAM mechanisms: ICMP Ping, LSP
Ping, and BFD, as described in [RFC5085]. BFD has been chosen to
cover MPLS-TP CC functionality [base-BFD], and an extended version of
BFD, as described in [BFD-CV], can accomplish both MPLS-TP CC and CV,
even signal the AC status. BFD for VCCV supports two modes of
encapsulation - either IP/UDP encapsulated (with IP/UDP header) or
PW-ACH encapsulated (with no IP/UDP header).
The use of the VCCV control channel provides the context, based on
the MPLS-PW label, required to bind and bootstrap the BFD session to
a particular PW (FEC), see the analysis in [tp-oam-analysis]. But in
order to identify certain extreme cases of misconnectivity and fill
the requirements that the BFD mechanism MUST be the same for LSP,
(MS-)PW and Section as well as for LSP Tandem Connection and PW
Tandem Connection [BFD-CV], BFD still needs to use Discriminator
values to identify the connection being verified at both ends of the
PW.
The discriminator values can be statically configured, or signaled
via LSP-Ping [[tp-ping-bfd-procedure]. According to the requirements
in [RFC5654], "The MPLS-TP control plane MUST support the
configuration and modification of OAM maintenance points as well as
the activation/deactivation of OAM when the transport path or
transport service is established or modified", it is naturally to
extend LDP for setting up BFD or BFD extended version in order to
configure MPLS-TP CC and CV OAM functionalities during the PW setup.
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 RFC2119.
3. LDP extensions
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3.1. Operation overviews
Below, extension to LDP for setting up BFD or BFD extended version
are defined in order to configure MPLS-TP CC and CV OAM
functionalities during the PW setup. PW signaling [RFC4447] defines
two FECs used to signal PWs. Of these, FEC Type 129 along with AII
Type 2 as defined in [RFC5003] fits the identification requirements
of MPLS-TP, so the current version of this draft just focus on the
P2P PW (FEC 129) along with AII type 2, P2MP PW will be studied in
the future.
The terms "ingress LER" and "egress LER" will not refer in this
document to any direction in the forwarding plane, but only to the
LER triggering the PW setup (ingress LER) and the one receiving the
mapping message (egress LER).
During the PW signaling, the Control Plane instance in the ingress
and the egress LER announces the BFD OAM Configuration TLV (inside
the interface parameters TLV carried by the mapping message,
following the VCCV parameter field), which includes the "Local
Discriminator" sub-TLV.
During the BFD session the ingress LER will use as "MyDiscriminator"
the value announced in the "Local Discriminator" (mapping message
sent) and as "YourDiscriminator" the value received in the "Local
Discriminator" (mapping message received).
The interval value of BFD control packets both in transmission and
reception can be negotiated through BFD session itself, so the
mapping message does not need to carry these time values. In the
case BFD extended version should be configured, the ME ID and MEP ID
do not need to be carried also, for they can be deduced from the
advertised FEC(129) TLV, as described in the following sections.
3.2. OAM configuration TLV
This TLV, specified in [OAM-CONF-FWK], can be used to select which
OAM technology/method should be used for the PW here. [RSVP-TE-OAM]
defines BFD OAM Type and two types of allowed BFD OAM configuration
TLV, which can also be used for the PW:
"BFD CC OAM Configuration TLV" which MUST be used for configuring BFD
for setting up the proactive MPLS-TP CC OAM tool (TLV type = 4).
"BFD CC&CV OAM Configuration TLV" which MUST be used for configuring
BFD for setting up the proactive MPLS-TP CC&CV OAM tool (TLV type =
5).
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In case the receiving LER does not support the CC&CV functionality,
they must be silently ignored so as not to affect the setup of PW.
3.3. BFD CC OAM Configuration TLV
The BFD CC OAM Configuration TLV (depicted below) is defined for BFD
OAM specific configuration parameters. The BFD CC OAM Configuration
TLV is carried as a sub-TLV of the "OAM Configuration TLV" in the
"Interface Parameter TLV" in mapping messages, following "the VCCV
parameter field".
This new TLV accommodates generic BFD OAM information and carries
sub-TLVs.
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 (4) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers.|R| Reserved (set to all 0s) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD CC OAM Configuration TLV
Type: indicates a new type, the "BFD CC OAM Configuration TLV" (4)
(IANA to define).
Length: indicates the total length including sub-TLVs.
Version: identifies the BFD protocol version.
R Flag: Role Flag. If set, the receiving node is required to act
with an Active Role as described in [[base-BFD], sect. 6.1].
The BFD CC OAM Configuration TLV MUST include the following sub-TLVs
during the mapping message:
"Local Discriminator" sub-TLV (described in paragraph 3.3.1)
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3.3.1. Local Discriminator sub-TLV
The Local Discriminator sub-TLV is depicted below.
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 (1) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Local Discriminator sub-TLV
Type: indicates a new type, the Local Discriminator sub TLV (1) (IANA
to define)
Length: indicates the total length of the TLV including padding.
Local Discriminator: A unique, nonzero discriminator value generated
by the transmitting system and referring to itself, used to
demultiplex multiple BFD sessions between the same pair of systems.
This Discriminator will be signaled both by the ingress LSR and the
egress LSR in the mapping message respectively.
3.4. BFD CC&CV OAM Configuration TLV
The BFD CC&CV OAM Configuration TLV (depicted below) is defined for
BFD OAM specific configuration parameters. The BFD CC&CV OAM
Configuration TLV is carried as a sub-TLV of the "OAM Configuration
TLV" in the "Interface Parameter TLV" in mapping messages, following
"the VCCV parameter field".
This new TLV accommodates generic BFD OAM information and carries
sub-TLVs.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFD CC&CV Type (5) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers.|R| Reserved (set to all 0s) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: BFD CC&CV OAM Configuration TLV
Type: indicates a new type, the "BFD CC&CV OAM Configuration TLV" (5)
(IANA to define).
Length: indicates the total length including sub-TLVs.
Version: identifies the BFD protocol version.
R Flag: Role Flag. If set, the receiving node is required to act
with an Active Role as described in [[base-BFD], sect. 6.1].
The BFD CC OAM Configuration TLV MUST include the following sub-TLVs
during the mapping message:
"Local Discriminator" sub-TLV (described in paragraph 3.3.1)
The BFD CC&CV OAM Configuration TLV May include the following sub-
TLVs during the mapping message:
"ICC based ME-IDs" sub-TLV (described in paragraph 3.4.2)
3.4.1. MEP_IDs
In order to automatically generate MEP_IDs for MPLS-TP PWs, this
draft is apt to use the AII associated with that end of the PW. The
AII is composed of three fields. These are the Global_ID, the
Prefix, and the AC_ID. The Global_ID used in this document is
identical to the Global_ID defined in [RFC5003]. The Node_ID is used
as the Prefix. The AC_ID is as defined in [RFC5003]. In this way,
the definition is in accordance with the suggestion in the draft
[tp-identifier], and there is no need to carry MEP_ID in the mapping
message.
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3.4.2. ME_IDs
3.4.2.1. IP Compatible ME-IDs
In order to automatically generate ME_IDs for MPLS-TP PWs, it is
convenient to use the corresponding PW identifier. In an MPLS-TP
environment, a PW is identified by a set of identifiers which can be
mapped directly to the elements required by FEC 129 and AII Type 2,
so there is no need to carry ME_IDs in the mapping messages also.
3.4.2.2. ICC-based ME_IDs
ME ID for PWs MAY use the globally unique ICC-based format. This ME
ID format MAY be used to identify SME, LME, LTCME, PME and PTCME (as
defined in [OAM-CONF-FWK]) independently on LER/T-PE addressing
schemes as well as of the FECs used to identify the PW.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ME ID Type | Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| MEG ID |
+ (13 bytes) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: ICC-based ME_ID TLV
ME ID Type: it identifies the specific format, value = TBD.
Length: indicates the total length and it is set to 20.
ME ID value: the ME ID is a string of up to thirteen characters, each
character being either alphabetic (i.e. A-Z) or numeric (i.e. 0-9)
characters. It consists of two subfields: the ICC (as defined in
section 3) followed by a unique ME ID code (UMC). The UMC MUST be
unique within the organization identified by the ICC.
If the receiving LER does not support this ME ID format, it must be
silently ignored.
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4. IANA Considerations
TBD.
5. Security Considerations
TBD.
6. Acknowledgement
The author would like to thank Hongbo Wei for his useful discussion.
7. References
7.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto,
"Attachment Individual Identifier (AII) Types for
Aggregation", RFC 5003, September 2007.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009.
7.2. Informative References
[BFD-CV] Fulignoli, A., Boutros, S., and M. Vigoureux, "MPLS-TP BFD
for Proactive CC-CV and RDI", July 2009.
[OAM-CONF-FWK]
Takacs, A., Fedyk, D., and J. He, "OAM Configuration
Framework and Requirements for GMPLS RSVP-TE", March 2009.
[RSVP-TE-OAM]
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Bellagamba, E., Andersson, L., and P. Skoldstrom, "RSVP-TE
Extensions for MPLS-TP OAM Configuration", September 2009.
[base-BFD]
Katz, D. and D. Ward, "Bidirectional Forwarding
Detection", February 2009.
[tp-identifier]
Bocci, M. and G. Swallow, "MPLS-TP Identifiers",
July 2009.
[tp-oam-analysis]
Sprecher, N., Van Helvoort, H., Bellagamba, E., and Y.
Weingarten, "MPLS-TP OAM Analysis", October 2009.
[tp-ping-bfd-procedure]
Bahadur, N., Aggarwal, R., Nadeau, T., Sprecher, N., and
Y. Weingarten, "LSP-Ping and BFD for MPLS-TP", July 2009.
Authors' Addresses
Fei Zhang
ZTE Corporation
4F,RD Building 2,Zijinghua Road
Yuhuatai District,Nanjing 210012
P.R.China
Phone: +86 025 52877612
Email: zhang.fei3@zte.com.cn
Bo Wu
ZTE Corporation
4F,RD Building 2,Zijinghua Road
Yuhuatai District,Nanjing 210012
P.R.China
Phone: +86 025 52877276
Email: wu.bo@zte.com.cn
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Xuehui Dai
ZTE Corporation
4F,RD Building 2,Zijinghua Road
Yuhuatai District,Nanjing 210012
P.R.China
Phone: +86 025 52877612
Email: dai.xuehui@zte.com.cn
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