CCAMP Working Group E. Bellagamba, Ed.
Internet-Draft L. Andersson, Ed.
Intended status: Experimental Ericsson
Expires: January 3, 2010 P. Skoldstrom
Acreo
July 2, 2009
RSVP-TE Extensions for MPLS-TP OAM Configuration
draft-bellagamba-ccamp-rsvp-te-mpls-tp-oam-ext-00
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Abstract
This document defines a method for the configuration of the
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Bidirectional Forwarding Detection (BFD) OAM mechanism through
RSVP-TE Control Plane. The procedures described are experimental and
are intended to be possibly updated with other proposed OAM tools and
BFD future extensions.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
1.2. Contributing Authors . . . . . . . . . . . . . . . . . . . 3
1.3. Background . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of BFD OAM operation . . . . . . . . . . . . . . . . . 4
3. RSVP-TE Extensions . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Operation overview . . . . . . . . . . . . . . . . . . . . 4
3.2. OAM Configuration TLV . . . . . . . . . . . . . . . . . . . 6
3.3. BFD OAM Configuration TLV . . . . . . . . . . . . . . . . . 6
3.4. Local Discriminator Sub-TLV . . . . . . . . . . . . . . . . 7
3.5. Required TX interval . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
This document defines a method for the configuration of the
Bidirectional Forwarding Detection (BFD) OAM mechanism through GMPLS
Control Plane.
The procedures described are experimental and are intended to be
possibly updated with other proposed OAM tools and BFD future
extensions.
The document intent is both disseminating experimental results
carried out within Ericsson Research and provide an initial input for
further Control Plane extension in CCAMP IETF group.
1.1. 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].
1.2. Contributing Authors
The editors gratefully acknowledge the contributions of Benoit C
Tremblay, Andras Kern, Attila Takacs and David Jocha.
1.3. Background
MPLSTransport Profile (MPLS-TP), describes a profile of MPLS that
enables operational models typical in transport networks, while
providing additional OAM, survivability and other maintenance
functions not currently supported by MPLS.
[MPLS-TP-OAM-REQ] defines the requirements by which the OAM
functionality of MPLS-TP should abide. The requirements listed may
be met by one or more OAM Protocols.
Bidirectional Forwarding Detection, as described in [BFD], defines a
protocol that provides low-overhead, short-duration detection of
failures in the path between two forwarding engines, including the
interfaces, data link(s), and to the extent possible the forwarding
engines themselves. BFD can be used to track the liveliness of
MPLS-TP point-to-point and p2mp connections and detect data plane
failures. This version of the draft is focused on unidirectional and
bidirectional p2p connection.
There are no OAM mechanisms designated to operate in conjunction with
MPLS-TP yet. BFD meets several of the requirements listed so far in
[MPLS-TP-OAM-REQ] and can be a good candidate for Continuity Check in
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MPLS-TP.
Other proposed OAM tools and BFD future extensions will be possibly
taken into account in this document during the next releases.
RSVP-TE control plane [RFC3471] has been chosen to support the
establishment of MPLS-TP LSPs.
2. Overview of BFD OAM operation
BFD is a simple hello protocol that in many respects is similar to
the detection components of well-known routing protocols. A pair of
systems transmit BFD packets periodically over each path between the
two systems, and if a system stops receiving BFD packets for long
enough, some component in that particular bidirectional path to the
neighboring system is assumed to have failed. Systems may also
negotiate to not send periodic BFD packets in order to reduce
overhead.
A path is only declared to be operational when two-way communication
has been established between systems, though this does not preclude
the use of unidirectional links.
Section 3 in [BFD] states that a separate BFD session is created for
each communications path and data protocol in use between two
systems.
Each system estimates how quickly it can send and receive BFD packets
in order to come to an agreement with its neighbor about how rapidly
detection of failure will take place. These estimates can be
modified in real time in order to adapt to unusual situations. This
design also allows for fast systems on a shared medium with a slow
system to be able to more rapidly detect failures between the fast
systems while allowing the slow system to participate to the best of
its ability.
The ability of each system to control the BFD packet transmission
rate in both directions provides a mechanism for congestion control,
particularly when BFD is used across multiple network hops.
3. RSVP-TE Extensions
3.1. Operation overview
A BFD session may be established for a FEC associated with a MPLS
LSP. In case of:
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o PHP
o when the egress LSR distributes an explicit null label to the
penultimate hop router
o next-hop label allocation
the BFD control packet received by the egress LSR does not contain
sufficient information to associate it with a BFD session. Hence the
demultiplexing MUST be done using the remote discriminator field in
the received BFD control packet.
The exchange of BFD discriminators for this purpose can be achieved
with LSP Ping as described in [LSP Ping]. However, LSP Ping presents
some drawbacks such as high computational complexity and the
dependency to the IP protocol, as described in [MPLS-TP OAM
Analysis]. Such dependency should be avoided in a MPLS-TP context,
since MPLS-TP can not count on IP as forwarding mechanism in the data
plane.
Below, we define some simple additions that can be done in GMPLS
RSVP-TE in order to carry out a BFD session setup at the same time as
the setup of the LSP related to the BFD session.
With the terms "ingress LSR" and "egress LSR" we will not refer to
any direction in the forwarding plane, but only to the LSR triggering
the LSP setup (ingress LSR) and the one triggering the response to it
(egress LSR).
During the LSP signaling, the Control Plane instance in the ingress
and the egress LSR announces the BFD OAM Configuration TLV (inside
the LSP_ATTRIBUTES object carried by the Path and Resv message
respectively), which includes the "Local Discriminator" sub-TLV.
During the BFD session the ingress LSR will use as "MyDiscriminator"
the value announced in the "Local Discriminator"(Path message) and as
"YourDiscriminator" the value received in the "Local Discriminator"
(Resv message).
Moreover, in the BFD protocol, the time values used to determine BFD
packet transmission intervals and the session Detection Time are
continuously negotiated by the BFD protocol itself, and thus may be
changed at any time. The negotiation and time values are independent
in each direction for each session, as described in [BFD] section
6.8.2.
It is introduced the possibility of advertising the initial time
values, together with the Discriminator values, during the control
plane session setup. The Control Plane instance in the ingress LSR
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will advertise its timing requirements in the Path messages. It will
be signaled a single value for both directions in asynchronous and
echo mode. The egress LSR will acknowledge them or reply with an
error message.
3.2. OAM Configuration TLV
This TLV is specified in [OAM-CONF-FWK] and is used to select which
OAM technology/method should be used for the LSP. In this document a
new OAM Type: BFD OAM is defined.
+----------+--------------+
| OAM Type | Description |
+----------+--------------+
| 0 | Reserved |
| 1 | Ethernet OAM |
| 2 | BFD |
| 2-256 | Reserved |
+----------+--------------+
The receiving node when the BFD OAM Type is requested should look for
the corresponding technology specific BFD OAM configuration TLV.
3.3. BFD OAM Configuration TLV
The BFD OAM Configuration TLV (depicted below) is defined for BFD OAM
specific configuration parameters. The BFD OAM Configuration TLV is
carried in the LSP_ATTRIBUTES object both in Path and Resv messages.
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 ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the BFD OAM Configuration TLV (4) (IANA
to define).
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Length: indicates the total length including sub-TLVs.
Version: identifies the BFD protocol version. If a node does not
support a specific BFD version an error must be generated: "OAM
Problem/Unsupported OAM Version "
R Flag: Role Flag. If set, the receiving node is required to act
with an Active Role as described in [BFD], section 6.1. When the BFD
OAM Configuration TLV is carried in the Resv message, the flag it not
taken into consideration by the receiving node.
3.4. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 Path and Resv message respectively.
3.5. Required TX interval
The Required TX interval sub-TLV is depicted below.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (3) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Asynchronous TX interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Echo TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Detect. Mult | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: indicates a new type, the Required TX interval sub TLV (3)
(IANA to define).
Length: indicates the total length of the TLV including padding.
Required Asynchronous TX interval: the interval, in microseconds,
that the local system would like to have when both transmitting and
receiving BFD Control packets, less any jitter applied. The value
zero is reserved. If the receiving system can not support this value
it will return an error.
Required Echo TX Interval: the minimum interval, in microseconds,
between received BFD Echo packets that this system is capable of
supporting, less any jitter applied by the sender as described in
[BFD], section 6.8.9. This value is also an indication for the
receiving system of the minimum interval between transmitted BFD Echo
packets. If this value is zero, the transmitting system does not
support the receipt of BFD Echo packets. If the receiving system can
not support this value it will return an error.
Detect Mult: detection time multiplier. The transmit interval,
multiplied by this value, provides the Detection Time for the
transmitting and receiving system in Asynchronous mode.
4. IANA Considerations
This document specifies a new BFD OAM Configuration TLV to be carried
in the OAM Configuration TLV in LSP_ATTRIBUTES and
LSP_REQUIRED_ATTRIBUTES objects in Path messages.
5. Security Considerations
This document does not introduce any new security considerations.
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6. References
6.1. Normative References
[BFD] Katz, D. and D. Ward, "Bidirectional Forwarding
Detection", 2009, <draft-ietf-bfd-base-09.txt>.
[MPLS-TP-OAM-REQ]
Vigoureux, M., Ward, D., and M. Betts, "Requirements for
OAM in MPLS Transport Networks", 2009,
<http://www.example.com/dominator.html>.
[OAM-CONF-FWK]
Takacs, A., Fedyk, D., and J. van He, "OAM Configuration
Framework for GMPLS RSVP-TE", 2009,
<draft-ietf-ccamp-oam-configuration-fwk-01>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
6.2. Informative References
[LSP Ping]
Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", 2006, <RFC
3479>.
[MPLS-TP OAM Analysis]
Sprecher, N., Nadeau, T., van Helvoort, H., and
Weingarten, "MPLS-TP OAM Analysis", 2006,
<draft-sprecher-mpls-tp-oam-analysis-04.txt>.
Appendix A. Additional Stuff
This becomes an Appendix.
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Authors' Addresses
Elisa Bellagamba (editor)
Ericsson
Farogatan 6
Stockholm, 164 40
Sweden
Phone: +46 761440785
Email: elisa.bellagamba@ericsson.com
Loa Andersson (editor)
Ericsson
Farogatan 6
Stockholm, 164 40
Sweden
Phone:
Email: loa.andersson@ericsson.com
Pontus Skoldstrom
Acreo
Stockholm, 164 40
Sweden
Phone:
Email: pontus.skoldstrom@acreo.com
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