Network Working Group A. Takacs
Internet-Draft F. Fondelli
Intended status: Standards Track B. Tremblay
Expires: April 29, 2010 Ericsson
October 26, 2009
GMPLS RSVP-TE Recovery Extension for data plane initiated reversion and
protection timer signalling
draft-takacs-ccamp-revertive-ps-04
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Abstract
GMPLS RSVP-TE recovery extensions are specified in [RFC4872] and
[RFC4873]. Currently recovery signalling does not support the
request for revertive protection, neither the configuration of
recovery timers. This document extends the PROTECTION Object format
allowing sub-TLVs, and defines two sub-TLVs to carry wait-to-restore
and hold-off intervals.
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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
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Updated PROTECTION Object format and sub-TLVs . . . . . . . . 6
3. Error handling . . . . . . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Generalised MPLS (GMPLS) extends MPLS to include support for
different switching technologies [RFC3471]. These switching
technologies provide several protection schemes [RFC4426][RFC4427]
(e.g. 1+1, 1:N, M:N). Many characteristics of those protection
schemes are common disregard of the switching technology (e.g. TDM,
LSC, etc). GMPLS RSVP-TE signalling has been extended to support the
various protection schemes and establish connections (Label Switched
Paths (LSPs)) configuring its specific protection characteristics
[RFC4426][RFC4872].
Currently RSVP-TE extensions do not address the configuration of
protection switching timers neither provide information on the
protection switching operation mode (i.e., revertive or non-
revertive).
The Hold-off time (HOFF) is defined as the time between the reporting
of signal fail or degrade, and the initialization of the recovery
switching operation [RFC4427]. This timer is useful to limit the
number of switch actions when multiple layers of recovery are being
used, or in case of 1+1 unidirectional protection scheme [G.808.1] to
prevent too early switching due to the differential delay difference
between the short and long path.
The Wait-to-Restore time (WTR) is defined as a period of time that
must elapse after a recovered fault before an LSP can be used again
to transport the normal traffic and/or to select the normal traffic
from the LSP [RFC4427]. The WTR time is fundamental in revertive
mode of operation, to prevent frequent operation of the protection
switch due to an intermittent defect [G.808.1].
Reversion refers to the process of moving normal traffic back to the
original working LSP after the failure is cleared and the path is
repaired [RFC4426][RFC4427][RFC4872]. In transport networks
reversion is desirable since the protection path may not be optimal
from a routing and resource consumption point of view, additionally,
moving traffic back to the working LSP allows the protection
resources to be used to protect other LSPs. On the other hand,
reversion requires that the working resources remain allocated during
failure. The operator needs to have the choice between revertive and
non-revertive protection to balance the pros and cons in a given
situation.
WTR and HOFF timers must be accurately configured at both ends of the
LSP. Operators may need to tune these timers on a per LSP basis to
ensure best protection switching performance (e.g., account for
differential delays between worker and protection paths). Currently
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these values are either pre-configured to a default value (and so may
be suboptimal for some of the LSPs) or need to be manually set/tuned
after the connections have been established. Since these parameters
are important for recovery in transport networks, it is desirable
that GMPLS RSVP-TE protection signalling carries the necessary
information.
This document extends the PROTECTION Object format allowing sub-TLVs,
and defines two sub-TLVs to carry WTR and HOFF values.
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2. Updated PROTECTION Object format and sub-TLVs
In [RFC4872] and [RFC4873] the PROTECTION object is specified to
support end-to-end and segment recovery. In order to ease addition
of protection attributes the PROTECTION Object is extended to carry
sub-TLVs. The new format updates the PROTECTION Object format of
C-Type 2. The updated format is depicted below. IANA is requested
to maintain the TLV space for the PROTECTION Object.
We retained C-Type to ensure that nodes not capable of interpreting
the new format (sub-TLVs) will still be able to process the object
without being required to generate an error; while nodes recognising
the new format will process the TLVs accordingly. The processed sub-
TLV MUST be included in the PROTECTION Object sent in the Resv
message upstream, to ensure that the sender can maintain a consistent
view of the actual protection configuration of the LSP.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(37) | C-Type(2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|P|N|O| Reserved | LSP Flags | Reserved | Link Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I|R| Reserved | Seg.Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ sub-TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This document specifies two new sub-TLVs.
WTR - Wait-to-Restore time sub-TLV specifies the WTR time. If the
WTR field is 0 the protection switching operation mode is non-
revertive, otherwise revertive operation with the signalled timer (in
milliseconds) is requested. The value 0xffffffff is reserved, and
refers to a locally pre-configured WTR value.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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HOFF - Hold-off time sub-TLV specifies the HOFF time. The values are
in milliseconds. The value 0xffffffff is reserved, and refers to a
locally pre-configured HOFF value.
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 (2) (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HOFF |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the case of end-to-end protection the PROTECTION Object is
inserted at the top level in the Path message, the WTR and HOFF
fields correspond to the end-to-end protection. In the case when a
segment of the LSP is to be protected and the WTR and HOFF timers for
the protection segment are to be set by signalling, explicit segment
recovery control has to be used, i.e., the PROTECTION Object with the
desired timers set must be inserted in the appropriate Secondary
Explicit Route Object (SERO).
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3. Error handling
In the case a specific configuration of the timers is not supported
the corresponding error should be generated and sent in the PathErr
message: "Routing Problem/Unsupported WTR value" and/or "Routing
Problem/Unsupported HOFF value".
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4. IANA Considerations
A new TLV space needs to be opened and maintained for the PROTECTION
Object in the "Class Names, Class Numbers, and Class Types "
Registry.
New error values need to be added to "Error Codes and Globally-
Defined Error Value Sub-Codes " Registry for the "Routing Problem"
Error Code: "Unsupported WTR value" and "Unsupported HOFF value".
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5. Security Considerations
This document introduces no new security issues. The considerations
in [RFC4872] and [RFC4873] apply.
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6. References
[G.808.1] "Generic protection switching -- Linear trail and
subnetwork protection", ITU-T Recommendation G.808.1,
March 2006.
[IEEE-PBBTE]
"IEEE 802.1Qay Draft Standard for Provider Backbone
Bridging Traffic Engineering", work in progress.
[RFC3471] "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Functional Description", RFC 3471, January 2003.
[RFC4426] "Generalized Multi-Protocol Label Switching (GMPLS)
Recovery Functional Specification", RFC 4426, March 2006.
[RFC4427] "Recovery (Protection and Restoration) Terminology for
Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4427, March 2006.
[RFC4872] "RSVP-TE Extensions in Support of End-to-End Generalized
Multi-Protocol Label Switching (GMPLS) Recovery",
RFC 4872, May 2007.
[RFC4873] "GMPLS Segment Recovery", RFC 4873, May 2007.
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Authors' Addresses
Attila Takacs
Ericsson
Laborc u. 1.
Budapest, 1037
Hungary
Email: attila.takacs@ericsson.com
Francesco Fondelli
Ericsson
Via Negrone
Genova, 16153
Italy
Email: francesco.fondelli.ericsson.com
Benoit Tremblay
Ericsson
8400 Decarie.
Montreal, Quebec H4P 2N2
Canada
Email: benoit.c.tremblay@ericsson.com
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