Network Working Group P. Ashwood-Smith, Editor
Request for Comments: 3472 Nortel Networks
Category: Standards Track L. Berger, Editor
Movaz Networks
January 2003
Generalized Multi-Protocol Label Switching (GMPLS) Signaling
Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes extensions to Multi-Protocol Label Switching
(MPLS) Constraint-based Routed Label Distribution Protocol (CR-LDP)
signaling required to support Generalized MPLS. Generalized MPLS
extends the MPLS control plane to encompass time-division (e.g.,
Synchronous Optical Network and Synchronous Digital Hierarchy,
SONET/SDH), wavelength (optical lambdas) and spatial switching (e.g.,
incoming port or fiber to outgoing port or fiber). This document
presents a CR-LDP specific description of the extensions. A generic
functional description can be found in separate documents.
Table of Contents
1. Introduction .............................................. 22. Label Related Formats .................................... 32.1 Generalized Label Request ............................... 32.2 Generalized Label ....................................... 42.3 Waveband Switching ...................................... 52.4 Suggested Label ......................................... 62.5 Label Set ............................................... 63. Bidirectional LSPs ........................................ 83.1 Procedures .............................................. 84. Notification on Label Error ............................... 95. Explicit Label Control .................................. 95.1 Procedures .............................................. 9
Ashwood-Smith & Berger Standards Track [Page 1]
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6. Protection TLV ............................................ 106.1 Procedures .............................................. 117. Administrative Status Information ......................... 117.1 Admin Status TLV ........................................ 117.2 REQUEST and MAPPING Message Procedures .................. 127.3 Notification Message Procedures ......................... 138. Control Channel Separation ................................ 148.1 Interface Identification ................................ 148.2 Errored Interface Identification ........................ 159. Fault Handling ......................................... 17
10 Acknowledgments ........................................... 1711. Security Considerations ................................... 1712. IANA Considerations ....................................... 1713. Intellectual Property Considerations ...................... 1814. References ................................................ 1814.1 Normative References ................................... 1814.2 Informative References ................................. 1915. Contributors .............................................. 1916. Editors' Addresses ........................................ 2217. Full Copyright Statement ................................... 23
Generalized MPLS extends MPLS from supporting packet (PSC) interfaces
and switching to include support of three new classes of interfaces
and switching: Time-Division Multiplex (TDM), Lambda Switch (LSC) and
Fiber-Switch (FSC). A functional description of the extensions to
MPLS signaling needed to support the new classes of interfaces and
switching is provided in [RFC3471]. This document presents CR-LDP
specific formats and mechanisms needed to support all four classes of
interfaces. RSVP-TE extensions can be found in [RFC3473].
[RFC3471] should be viewed as a companion document to this document.
The format of this document parallels [RFC3471]. It should be noted
that the RSVP-TE specific version of Generalized MPLS includes RSVP
specific support for rapid failure notification, see Section 4
[RFC3473]. For CR-LDP there is not currently a similar mechanism.
When a failure is detected it will be propagated with
RELEASE/WITHDRAW messages radially outward from the point of failure.
Resources are to be released in this phase and actual resource
information may be fed back to the source using a feedback
mechanisms.
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].
Ashwood-Smith & Berger Standards Track [Page 2]
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A REQUEST message SHOULD contain as specific an LSP (Label Switched
Path) Encoding Type as possible to allow the maximum flexibility in
switching by transit LSRs. A Generalized Label Request Type, Length,
and Value (TLV) is set by the ingress node, transparently passed by
transit nodes, and used by the egress node. The Switching Type field
may also be updated hop-by-hop.
The format of a Generalized Label Request is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type (0x0824) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
A node processing a REQUEST message containing a Generalized Label
Request must verify that the requested parameters can be satisfied by
the incoming interface, the node and by the outgoing interface. The
node may either directly support the LSP or it may use a tunnel (FA),
i.e., another class of switching. In either case, each parameter
must be checked.
Note that local node policy dictates when tunnels may be used and
when they may be created. Local policy may allow for tunnels to be
dynamically established or may be solely administratively controlled.
For more information on tunnels and processing of ER (Explicit Route)
hops when using tunnels see [MPLS-HIERARCHY].
Transit and egress nodes MUST verify that the node itself and, where
appropriate, that the outgoing interface or tunnel can support the
requested LSP Encoding Type. If encoding cannot be supported, the
node MUST generate a NOTIFICATION message, with a "Routing
problem/Unsupported Encoding" indication.
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Nodes MUST verify that the type indicated in the Switching Type
parameter is supported on the corresponding incoming interface. If
the type cannot be supported, the node MUST generate a NOTIFICATION
message with a "Routing problem/Switching Type" indication.
The G-PID parameter is normally only examined at the egress. If the
indicated G-PID cannot be supported then the egress MUST generate a
NOTIFICATION message, with a "Routing problem/Unsupported G-PID"
indication. In the case of PSC and when penultimate hop popping
(PHP) is requested, the penultimate hop also examines the (stored)
G-PID during the processing of the MAPPING message. In this case if
the G-PID is not supported, then the penultimate hop MUST generate a
NOTIFICATION message with a "Routing problem/Unacceptable label
value" indication. The generated NOTIFICATION message MAY include an
Acceptable Label Set, see Section 4.
When an error message is not generated, normal processing occurs. In
the transit case this will typically result in a REQUEST message
being propagated. In the egress case and PHP special case this will
typically result in a MAPPING message being generated.
Bandwidth encodings are carried in the CR-LDP Traffic Parameters TLV.
See [RFC3471] for a definition of values to be used for specific
signal types. These values are set in the Peak and Committed Data
Rate fields of the Traffic Parameters TLV. Other bandwidth/service
related parameters in the TLV are ignored and carried transparently.
The Generalized Label travels in the upstream direction in MAPPING
messages.
The presence of both a generalized and normal label TLV in a MAPPING
message is a protocol error and should treated as a malformed message
by the recipient.
The recipient of a MAPPING message containing a Generalized Label
verifies that the values passed are acceptable. If the label is
unacceptable then the recipient MUST generate a NOTIFICATION message
with a "Routing problem/MPLS label allocation failure" indication.
The generated NOTIFICATION message MAY include an Acceptable Label
Set, see Section 4.
Waveband switching uses the same format as the generalized label, see
section 2.2. The type 0x0828 is assigned for the Waveband Label.
In the context of waveband switching, the generalized label has the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type (0x0828) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Waveband Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
The procedures defined in Section 2.2.1 apply to waveband switching.
This includes generating a NOTIFICATION message with a "Routing
problem/MPLS label allocation failure" indication if any of the label
fields are unrecognized or unacceptable.
Additionally, when a waveband is switched to another waveband, it is
possible that the wavelengths within the waveband will be mirrored
about a center frequency. When this type of switching is employed,
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the start and end label in the waveband label TLV MUST be swapped
before forwarding the label TLV with the new waveband Id. In this
manner an egress/ingress LSR that receives a waveband label which has
these values inverted, knows that it must also invert its egress
association to pick up the proper wavelengths. Without this
mechanism and with an odd number of mirrored switching operations,
the egress LSRs will not know that an input wavelength of say L1 will
emerge from the waveband tunnel as L100.
This operation MUST be performed in both directions when a
bidirectional waveband tunnel is being established.
The format of a suggested label is identical to a generalized label.
It is used in REQUEST messages. Suggested Label uses type = 0x904.
Errors in received Suggested Labels MUST be ignored. This includes
any received inconsistent or unacceptable values.
Per [RFC3471], if a downstream node passes a label value that differs
from the suggested label upstream, the upstream LSR MUST either
reconfigure itself so that it uses the label specified by the
downstream node or generate a NOTIFICATION message with a "Routing
problem/Unacceptable label value" indication. Furthermore, an
ingress node SHOULD NOT transmit data traffic using a suggested label
until the downstream node passes corresponding a label upstream.
The format of a Label Set is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type (0x0827) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Reserved | Label Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel 1 |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: : :
: : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel N |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Label Type: 14 bits
Indicates the type and format of the labels carried in the TLV.
Values match the TLV type of the appropriate Label TLV.
See [RFC3471] for a description of other parameters.
A Label Set is defined via one or more Label Set TLVs. Specific
labels/subchannels can be added to or excluded from a Label Set via
Action zero (0) and one (1) TLVs respectively. Ranges of
labels/subchannels can be added to or excluded from a Label Set via
Action two (2) and three (3) TLVs respectively. When the Label Set
TLVs only list labels/subchannels to exclude, this implies that all
other labels are acceptable.
The absence of any Label Set TLVs implies that all labels are
acceptable. A Label Set is included when a node wishes to restrict
the label(s) that may be used downstream.
On reception of a REQUEST message, the receiving node will restrict
its choice of labels to one, which is in the Label Set. Nodes
capable of performing label conversion may also remove the Label Set
prior to forwarding the REQUEST message. If the node is unable to
pick a label from the Label Set or if there is a problem parsing the
Label Set TLVs, then the request is terminated and a NOTIFICATION
message with a "Routing problem/Label Set" indication MUST be
generated. It is a local matter if the Label Set is stored for later
selection on the MAPPING message or if the selection is made
immediately for propagation in the MAPPING message.
On reception of a REQUEST message, the Label Set represented in the
message is compared against the set of available labels at the
downstream interface and the resulting intersecting Label Set is
forwarded in a REQUEST message. When the resulting Label Set is
empty, the REQUEST must be terminated, and a NOTIFICATION message,
and a "Routing problem/Label Set" indication MUST be generated. Note
that intersection is based on the physical labels (actual
wavelength/band values) which may have different logical values on
different links, as a result it is the responsibility of the node to
map these values so that they have a consistent physical meaning, or
to drop the particular values from the set if no suitable logical
label value exists.
When processing a MAPPING message at an intermediate node, the label
propagated upstream MUST fall within the Label Set.
Ashwood-Smith & Berger Standards Track [Page 7]
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Note, on reception of a MAPPING message a node that is incapable of
performing label conversion has no other choice than to use the same
physical label (wavelength/band) as received in the MAPPING message.
In this case, the use and propagation of a Label Set will
significantly reduce the chances that this allocation will fail.
Bidirectional LSP setup is indicated by the presence of an Upstream
Label in the REQUEST message. An Upstream Label has the same format
as the generalized label, see Section 2.2. Upstream Label uses type
= 0x0826.
The process of establishing a bidirectional LSP follows the
establishment of a unidirectional LSP with some additions. To
support bidirectional LSPs an Upstream Label is added to the REQUEST
message. The Upstream Label MUST indicate a label that is valid for
forwarding at the time the REQUEST message is sent.
When a REQUEST message containing an Upstream Label is received, the
receiver first verifies that the upstream label is acceptable. If
the label is not acceptable, the receiver MUST issue a NOTIFICATION
message with a "Routing problem/Unacceptable label value" indication.
The generated NOTIFICATION message MAY include an Acceptable Label
Set, see Section 4.
An intermediate node must also allocate a label on the outgoing
interface and establish internal data paths before filling in an
outgoing Upstream Label and propagating the REQUEST message. If an
intermediate node is unable to allocate a label or internal
resources, then it MUST issue a NOTIFICATION message with a "Routing
problem/Label allocation failure" indication.
Terminator nodes process REQUEST messages as usual, with the
exception that the upstream label can immediately be used to
transport data traffic associated with the LSP upstream towards the
initiator.
When a bidirectional LSP is removed, both upstream and downstream
labels are invalidated and it is no longer valid to send data using
the associated labels.
Ashwood-Smith & Berger Standards Track [Page 8]
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This section defines the Acceptable Label Set TLV to support
Notification on Label Error per [RFC3471]. An Acceptable Label Set
TLV uses a type value of 0x082a. The remaining contents of the TLV
have the identical format as the Label Set TLV, see Section 2.5.
Acceptable Label Set TLVs may be carried in NOTIFICATION messages.
The procedures for defining an Acceptable Label Set follow the
procedures for defining a Label Set, see Section 2.5.1.
Specifically, an Acceptable Label Set is defined via one or more
Acceptable Label Set TLVs. Specific labels/subchannels can be added
to or excluded from an Acceptable Label Set via Action zero (0) and
one (1) TLVs respectively. Ranges of labels/subchannels can be added
to or excluded from an Acceptable Label Set via Action two (2) and
three (3) TLVs respectively. When the Acceptable Label Set TLVs only
list labels/subchannels to exclude, this implies that all other
labels are acceptable.
The inclusion of Acceptable Label Set TLVs is optional. If included,
the NOTIFICATION message SHOULD contain a "Routing
problem/Unacceptable label value" indication. The absence of
Acceptable Label Set TLVs does not have any specific meaning.
The Label ER-Hop follows a ER-Hop containing the IP address, or the
interface identifier [MPLS-UNNUM], associated with the link on which
it is to be used. Up to two label ER-Hops may be present, one for
the downstream label and one for the upstream label. The following
SHOULD result in "Bad EXPLICIT_ROUTE" errors:
Ashwood-Smith & Berger Standards Track [Page 9]
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o If the first label ER-Hop is not preceded by a ER-Hop containing
an IP address, or a interface identifier [MPLS-UNNUM], associated
with an output link.
o For a label ER-Hop to follow a ER-Hop that has the L-bit set.
o On unidirectional LSP setup, for there to be a label ER-Hop with
the U-bit set.
o For there to be two label ER-Hops with the same U-bit values.
To support the label ER-Hop, a node must check to see if the ER-Hop
following its associate address/interface is a label ER-Hop. If it
is, one ER-Hop is examined for unidirectional LSPs and two ER-Hops
for bidirectional LSPs. If the U-bit of the ER-Hop being examined is
clear (0), then value of the label is copied into a new Label Set
TLV. This Label Set TLV MUST be included on the corresponding
outgoing REQUEST message.
If the U-bit of the ER-Hop being examined is set (1), then value of
the label is label to be used for upstream traffic associated with
the bidirectional LSP. If this label is not acceptable, a "Bad
EXPLICIT_ROUTE" error SHOULD be generated. If the label is
acceptable, the label is copied into a new Upstream Label TLV. This
Upstream Label TLV MUST be included on the corresponding outgoing
REQUEST message.
After processing, the label ER-Hops are removed from the ER.
Note an implication of the above procedures is that the label ER-Hop
should never be the first ER-Hop in a newly received message. If the
label ER-Hop is the first ER-Hop an a received ER, then it SHOULD be
treated as a "Bad strict node" error.
Procedures by which an LSR at the head-end of an LSP obtains the
information needed to construct the Label ER-Hop are outside the
scope of this document.
The use of the Protection TLV is optional. The TLV is included to
indicate specific protection attributes of an LSP.
The format of Protection Information TLV is:
Ashwood-Smith & Berger Standards Track [Page 10]
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type (0x0835) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | Link Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
Transit nodes processing a REQUEST message containing a Protection
TLV MUST verify that the requested protection can be satisfied by the
outgoing interface or tunnel (FA). If it cannot, the node MUST
generate a NOTIFICATION message, with a "Routing problem/Unsupported
Link Protection" indication.
Administrative Status Information is carried in the Admin Status TLV.
The TLV provides information related to the administrative state of a
particular LSP. The information is used in two ways. In the first,
the TLV is carried in REQUEST and MAPPING messages to indicate the
administrative state of an LSP. In the second, the TLV is carried in
Notification message to request a change to the administrative state
of an LSP.
The use of the Admin Status TLV is optional. It uses Type = 0x082b.
The format of the TLV is:
The format of Admin Status TLV in REQUEST, MAPPING and Notification
Messages is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type (0x082b) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R| Reserved |T|A|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
Ashwood-Smith & Berger Standards Track [Page 11]
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The Admin Status TLV is used to notify each node along the path of
the status of the LSP. Each node processes status information based
on local policy and then propagated in the corresponding outgoing
messages. The TLV is inserted in REQUEST messages at the discretion
of the ingress node. The absence of the TLV is the equivalent to
receiving a TLV containing values all set to zero.
Transit nodes receiving a REQUEST message containing an Admin Status
TLV, update their local state, take any appropriate local action
based on the indicated status and then propagate the received Admin
Status TLV in the outgoing REQUEST message.
Edge nodes receiving a REQUEST message containing an Admin Status
TLV, also update their local state and take any appropriate local
action based on the indicated status. When the ADMIN Status TLV is
received with the R bit set, the receiving edge node should reflect
the received values in a corresponding MAPPING message.
Specifically, if an egress node receives a Request message with the R
bit of the Admin_Status TLV set and the node the node SHOULD send a
Mapping message containing an Admin_Status TLV with the same values
set, with the exception of the R bit, as received in the
corresponding Request message.
In some circumstances, particularly optical networks, it is useful to
set the administrative status of an LSP before tearing it down.
In such circumstances the procedure SHOULD be followed when deleting
an LSP from the ingress:
o The ingress node precedes an LSP deletion by inserting an Admin
Status TLV in a Notification Message setting the Reflect (R) and
Delete (D) bits.
o Transit nodes process the Admin Status TLV by passing the
Notification message. The egress node May respond with a
Notification message with the Admin Status TLV.
o Upon receiving the Admin Status TLV with the Delete (D) bit set
in the Notification message, the egress SHOULD respond with a
LABEL WITHDRAW message and normal CR-LDP processing takes place.
In such circumstances the procedure SHOULD be followed when deleting
an LSP from the egress:
Ashwood-Smith & Berger Standards Track [Page 12]
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o The egress node indicates its desire for deletion by inserting an
Admin Status TLV in a Notification message and setting Delete (D)
bit.
o Transit nodes process the Admin Status TLV as described above.
o Upon receiving the Admin Status TLV with the Delete (D) bit set
in the Notification message, the ingress node sends a LABEL
RELEASE message downstream to remove the LSP and normal CR-LDP
processing takes place.
Subsequent messaging Admin Status messaging may be performed by
Notification Messages. The ingress may begin the propagation of a
Notification Message with an Admin Status TLV. Each subsequent node
propagates the Notification with the Admin Status TLV from the
ingress to the egress and then the egress node returns the
Notification messages back Upstream carrying the Admin Status TLV.
Intermediate and egress nodes may trigger the setting of
administrative status via the use of Notification messages. To
accomplish this, an intermediate or egress node generates a
Notification message with the corresponding upstream notify session
information. The Admin Status TLV MUST be included in the session
information, with the appropriate bit or bits set. The Reflect (R)
bit MUST NOT be set.
An ingress or egress node receiving a Notification message containing
an Admin Status TLV with the Delete (D) bit set, SHOULD initiate the
deletion procedure described in the previous section.
Some special processing is required in order to cover the case of
nodes that do not support the Admin Status TLV and other error
conditions. Specifically, a node that sends a Notification message
containing an Admin Status TLV with the Down (D) bit set MUST verify
that it receives a corresponding LABEL RELEASE message within a
configurable period of time. By default this period of time SHOULD
be 30 seconds. If the node does not receive such a LABEL RELEASE
message, it SHOULD send a Label Release message downstream and a
LABEL WITHDRAW message upstream.
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The choice of the data interface to use is always made by the sender
of the REQUEST message. The choice of the data interface is
indicated by the sender of the REQUEST message by including the data
channel's interface identifier in the message using a new Interface
TLV type. For bidirectional LSPs, the sender chooses the data
interface in each direction. In all cases but bundling, the upstream
interface is implied by the downstream interface. For bundling, the
REQUEST sender explicitly identifies the component interface used in
each direction.
An IF_ID TLV is used on links where there is not a one-to-one
association of a control channel to a data channel, see [RFC3471].
The LDP session uses the IF_ID TLV to identify the data channel(s)
associated with the LSP. For a unidirectional LSP, a downstream data
channel MUST be indicated. For bidirectional LSPs, a common
downstream and upstream data channel is normally indicated. In the
special case where a bidirectional LSP that traverses a bundled link,
it is possible to specify a downstream data channel that differs from
the upstream data channel. Data channels are specified from the
viewpoint of the sender of a REQUEST message. The IF_ID TLV SHOULD
NOT be used when no TLVs are needed.
A node receiving one or more IF_ID TLVs in a REQUEST message saves
their values and returns them in the subsequent MAPPING message sent
to the node that originated the TLVs.
Note, the node originating an IF_ID TLV MUST ensure that the selected
outgoing interface, as specified in the IF_ID TLV, is consistent with
an ERO. A node that receives an IF_ID TLV SHOULD check whether the
information carried in this TLV is consistent with the information
carried in a received ERO, and if not it MUST send a LABEL ABORT
Message with the error code "Routing Error" and error value of "Bad
Explicit Routing TLV Error" toward the sender. This check CANNOT be
performed when the initial ERO subobject is not the incoming
interface.
There are cases where it is useful to indicate a specific interface
associated with an error. To support these cases the IF_ID Status
TLV are defined.
Ashwood-Smith & Berger Standards Track [Page 15]
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Nodes wishing to indicate that an error is related to a specific
interface SHOULD use the appropriate IF_ID Status TLV in the
corresponding LABEL WITHDRAW or LABEL RELEASE message. IF_ID Status
TLV SHOULD be generated and processed as any other Status TLV, see
[RFC3036].
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In optical transport networks, failures in the out-of-fiber signaling
communication or optical control plane should not have service impact
on the existing optical connections. Under such circumstances, a
mechanism MUST exist to detect a signaling communication failure and
a recovery procedure SHALL guarantee connection integrity at both
ends of the signaling channel.
The LDP Fault tolerant document [LDP-FT] specifies the procedures for
recovering LDP and CR-LDP sessions under failure. Please refer to
his document for procedures on recovering optical connections.
Currently the Fault tolerant document covers many of the common
failure modes for a separated control and data plane.
This document is the work of numerous authors and consists of a
composition of a number of previous documents in this area.
Valuable comments and input were received from a number of people,
notably Adrian Farrel.
This document uses the LDP [RFC3036] name spaces, see
http://www.iana.org/assignments/ldp-namespaces, which lists the
assignments for the following TLVs:
o Generalized Label Request (TLV 0x0824)
o Generalized Label (TLV 0x0825)
o Upstream Label (TLV 0x0826)
o Label Set (TLV 0x0827)
o Waveband Label (TLV 0x0828)
o ER-Hop (TLV 0x0829)
o Acceptable Label Set (TLV 0x082a)
o Admin Status (TLV 0x082b)
o Interface ID (TLV 0x082c)
o IPV4 Interface ID (TLV 0x082d)
o IPV6 Interface ID (TLV 0x082e)
o IPv4 IF_ID Status (TLV 0x082f)
o IPv6 IF_ID Status (TLV 0x0830)
o Protection (TLV 0x0835)
Ashwood-Smith & Berger Standards Track [Page 17]
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This section is taken from Section 10.4 of [RFC2026].
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this standard. Please address the information to the IETF Executive
Director.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels," BCP 14, RFC 2119. March 1997.
[RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A.
and B. Thomas, "LDP Specification", RFC 3036,
January 2001.
[RFC3212] Jamoussi, B., Andersson, L., Callon, R., Dantu, R.,
Wu, L., Doolan, P., Worster, T., Feldman, N.,
Fredette, A., Girish, M., Gray, E., Heinanen, J.,
Kilty, T. and A. Malis, "Constraint-Based LSP Setup
using LDP", RFC 3212, January 2002.
[RFC3471] Berger, L., Editor, "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling Functional
Description", RFC 3471, January 2003.
Ashwood-Smith & Berger Standards Track [Page 18]
RFC 3472 GMPLS Signaling - CR-LDP Extensions January 2003
[LDP-FT] Farrel, A., et al, "Fault Tolerance for LDP and CR-
LDP", Work in Progress.
[MPLS-HIERARCHY] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
MPLS TE", Work in Progress.
[MPLS-UNNUM] Kompella, K., Rekhter, Y. and A. Kullberg,
"Signalling Unnumbered Links in CR-LDP", Work in
Progress.
[RFC2026] Bradner, S., "The Internet Standards Process --
Revision 3," BCP 9, RFC 2026, October 1996.
[RFC3473] Berger, L., Editor, "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling - Resource
ReserVation Protocol-Traffic Engineering (RSVP-TE)
Extensions", RFC 3473, January 2003.
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Ashwood-Smith & Berger Standards Track [Page 23]