Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions :: RFC3473
Network Working Group L. Berger, Editor
Request for Comments: 3473 Movaz Networks
Category: Standards Track January 2003
Generalized Multi-Protocol Label Switching (GMPLS) Signaling
Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) 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) Resource ReserVation Protocol - Traffic Engineering (RSVP-TE)
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 RSVP-TE specific description of the extensions. A generic
functional description can be found in separate documents.
Table of Contents
1. Introduction .............................................. 2
2. Label Related Formats .................................... 3
2.1 Generalized Label Request Object ........................ 3
2.2 Bandwidth Encoding ...................................... 4
2.3 Generalized Label Object ................................ 5
2.4 Waveband Switching ...................................... 5
2.5 Suggested Label ......................................... 6
2.6 Label Set ............................................... 7
3. Bidirectional LSPs ........................................ 8
3.1 Procedures .............................................. 9
3.2 Contention Resolution ................................... 9
4. Notification .............................................. 9
4.1 Acceptable Label Set Object ............................. 10
4.2 Notify Request Objects .................................. 10
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4.3 Notify Message .......................................... 12
4.4 Removing State with a PathErr message ................... 14
5. Explicit Label Control .................................... 15
5.1 Label ERO subobject ..................................... 15
5.2 Label RRO subobject ..................................... 16
6. Protection Object ......................................... 17
6.1 Procedures .............................................. 18
7. Administrative Status Information ......................... 18
7.1 Admin Status Object ..................................... 18
7.2 Path and Resv Message Procedures ........................ 18
7.3 Notify Message Procedures ............................... 20
8. Control Channel Separation ................................ 21
8.1 Interface Identification ................................ 21
8.2 Errored Interface Identification ........................ 23
9. Fault Handling ............................................ 25
9.1 Restart_Cap Object ...................................... 25
9.2 Processing of Restart_Cap Object ........................ 26
9.3 Modification to Hello Processing to Support
State Recovery .......................................... 26
9.4 Control Channel Faults .................................. 27
9.5 Nodal Faults ............................................ 27
10. RSVP Message Formats and Handling ......................... 30
10.1 RSVP Message Formats ................................... 30
10.2 Addressing Path and PathTear Messages ................. 32
11. Acknowledgments ........................................... 32
12. Security Considerations ................................... 33
13. IANA Considerations ....................................... 34
13.1 IANA Assignments ....................................... 35
14. Intellectual Property Considerations ...................... 36
15. References ................................................ 37
15.1 Normative References ................................... 37
15.2 Informative References ................................. 38
16. Contributors .............................................. 38
17. Editor's Address .......................................... 41
18. Full Copyright Statement .................................. 42
1. Introduction
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 RSVP-TE
specific formats and mechanisms needed to support all four classes of
interfaces.
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[RFC3471] should be viewed as a companion document to this document.
The format of this document parallels [RFC3471]. In addition to the
other features of Generalized MPLS, this document also defines RSVP-
TE specific features to support rapid failure notification, see
Sections 4.2 and 4.3.
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].
2. Label Related Formats
This section defines formats for a generalized label request, a
generalized label, support for waveband switching, suggested label
and label sets.
2.1. Generalized Label Request Object
A Path 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 object 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 object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (19)| C-Type (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
2.1.1. Procedures
A node processing a Path message containing a Generalized Label
Request must verify that the requested parameters can be satisfied by
the interface on which the incoming label is to be allocated, the
node itself, and by the interface on which the traffic will be
transmitted. 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.
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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 hops when using
tunnels see [MPLS-HIERARCHY].
Transit and egress nodes MUST verify that the node itself and, where
appropriate, that the interface or tunnel on which the traffic will
be transmitted can support the requested LSP Encoding Type. If
encoding cannot be supported, the node MUST generate a PathErr
message, with a "Routing problem/Unsupported Encoding" indication.
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 PathErr
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
PathErr message, with a "Routing problem/Unsupported L3PID"
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 Resv message. In this case if the
G-PID is not supported, then the penultimate hop MUST generate a
ResvErr message with a "Routing problem/Unacceptable label value"
indication. The generated ResvErr message MAY include an Acceptable
Label Set, see Section 4.1.
When an error message is not generated, normal processing occurs. In
the transit case this will typically result in a Path message being
propagated. In the egress case and PHP special case this will
typically result in a Resv message being generated.
2.2. Bandwidth Encoding
Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC
objects. See [RFC3471] for a definition of values to be used for
specific signal types. These values are set in the Peak Data Rate
field of Int-Serv objects, see [RFC2210]. Other bandwidth/service
related parameters in the object are ignored and carried
transparently.
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2.3. Generalized Label Object
The format of a Generalized Label object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (16)| C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters and encoding of labels.
2.3.1. Procedures
The Generalized Label travels in the upstream direction in Resv
messages.
The presence of both a generalized and normal label object in a Resv
message is a protocol error and should treated as a malformed message
by the recipient.
The recipient of a Resv message containing a Generalized Label
verifies that the values passed are acceptable. If the label is
unacceptable then the recipient MUST generate a ResvErr message with
a "Routing problem/MPLS label allocation failure" indication.
2.4. Waveband Switching Object
Waveband switching uses the same format as the generalized label, see
section 2.2. Waveband Label uses C-Type (3),
In the context of waveband switching, the generalized label has the
following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (16)| C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Waveband Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
2.4.1. Procedures
The procedures defined in Section 2.3.1 apply to waveband switching.
This includes generating a ResvErr 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,
the start and end label in the waveband label object MUST be flipped
before forwarding the label object with the new waveband Id. In this
manner an egress/ingress LSR which receives a waveband label which
has these values inverted, knows that it must also invert its egress
association to pick up the proper wavelengths.
This operation MUST be performed in both directions when a
bidirectional waveband tunnel is being established.
2.5. Suggested Label Object
The format of a Suggested_Label object is identical to a generalized
label. It is used in Path messages. A Suggested_Label object uses
Class-Number 129 (of form 10bbbbbb) and the C-Type of the label being
suggested.
Errors in received Suggested_Label objects 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 ResvErr message with a "Routing
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problem/Unacceptable label value" indication. Furthermore, an
ingress node SHOULD NOT transmit data traffic using a suggested label
until the downstream node passes a corresponding label upstream.
2.6. Label Set Object
The Label_Set object uses Class-Number 36 (of form 0bbbbbbb) and the
C-Type of 1. It is used in Path messages.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (36)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Reserved | Label Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel 1 |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: : :
: : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel N |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label Type: 14 bits
Indicates the type and format of the labels carried in the object.
Values match the C-Type of the appropriate RSVP_LABEL object.
Only the low order 8 bits are used in this field.
See [RFC3471] for a description of other parameters.
2.6.1. Procedures
A Label Set is defined via one or more Label_Set objects. Specific
labels/subchannels can be added to or excluded from a Label Set via
Action zero (0) and one (1) objects respectively. Ranges of
labels/subchannels can be added to or excluded from a Label Set via
Action two (2) and three (3) objects respectively. When the
Label_Set objects only list labels/subchannels to exclude, this
implies that all other labels are acceptable.
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The absence of any Label_Set objects 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 Path 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 Path message. If the node is unable to pick a label
from the Label Set or if there is a problem parsing the Label_Set
objects, then the request is terminated and a PathErr 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
Resv or if the selection is made immediately for propagation in the
Resv.
On reception of a Path 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 Path message. When the resulting Label Set is empty,
the Path must be terminated, and a PathErr 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 Resv message at an intermediate node, the label
propagated upstream MUST fall within the Label Set.
Note, on reception of a Resv 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 Resv message. In
this case, the use and propagation of a Label Set will significantly
reduce the chances that this allocation will fail.
3. Bidirectional LSPs
Bidirectional LSP setup is indicated by the presence of an Upstream
Label in the Path message. An Upstream_Label object has the same
format as the generalized label, see Section 2.3. The Upstream_Label
object uses Class-Number 35 (of form 0bbbbbbb) and the C-Type of the
label being used.
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3.1. Procedures
The process of establishing a bidirectional LSP follows the
establishment of a unidirectional LSP with some additions. To
support bidirectional LSPs an Upstream_Label object is added to the
Path message. The Upstream_Label object MUST indicate a label that
is valid for forwarding at the time the Path message is sent.
When a Path message containing an Upstream_Label object is received,
the receiver first verifies that the upstream label is acceptable.
If the label is not acceptable, the receiver MUST issue a PathErr
message with a "Routing problem/Unacceptable label value" indication.
The generated PathErr message MAY include an Acceptable Label Set,
see Section 4.1.
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 Path message. If an
intermediate node is unable to allocate a label or internal
resources, then it MUST issue a PathErr message with a "Routing
problem/MPLS label allocation failure" indication.
Terminator nodes process Path 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.
3.2. Contention Resolution
There are two additional contention resolution related considerations
when controlling bidirectional LSP setup via RSVP-TE. The first is
that for the purposes of RSVP contention resolution, the node ID is
the IP address used in the RSVP_HOP object. The second is that a
neighbor's node ID might not be known when sending an initial Path
message. When this case occurs, a node should suggest a label chosen
at random from the available label space.
4. Notification
This section covers several notification related extensions. The
first extension defines the Acceptable Label Set object to support
Notification on Label Error, per [RFC3471]. The second and third
extensions enable expedited notification of failures and other events
to nodes responsible for restoring failed LSPs. (The second
extension, the Notify Request object, identifies where event
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notifications are to be sent. The third extension, the Notify
message, provides for general event notification.) The final
notification related extension allows for the removal of Path state
on handling of PathErr messages.
4.1. Acceptable Label Set Object
Acceptable_Label_Set objects use a Class-Number 130 (of form
10bbbbbb). The remaining contents of the object, including C-Type,
have the identical format as the Label_Set object, see Section 2.6.
Acceptable_Label_Set objects may be carried in PathErr and ResvErr
messages. The procedures for defining an Acceptable Label Set follow
the procedures for defining a Label Set, see Section 2.6.1.
Specifically, an Acceptable Label Set is defined via one or more
Acceptable_Label_Set objects. Specific labels/subchannels can be
added to or excluded from an Acceptable Label Set via Action zero
(0) and one (1) objects respectively. Ranges of labels/subchannels
can be added to or excluded from an Acceptable Label Set via Action
two (2) and three (3) objects respectively. When the
Acceptable_Label_Set objects only list labels/subchannels to exclude,
this implies that all other labels are acceptable.
The inclusion of Acceptable_Label_Set objects is optional. If
included, the PathErr or ResvErr message SHOULD contain a "Routing
problem/Unacceptable label value" indication. The absence of
Acceptable_Label_Set objects does not have any specific meaning.
4.2. Notify Request Objects
Notifications may be sent via the Notify message defined below. The
Notify Request object is used to request the generation of
notifications. Notifications, i.e., the sending of a Notify message,
may be requested in both the upstream and downstream directions.
4.2.1. Required Information
The Notify Request Object may be carried in Path or Resv Messages,
see Section 7. The Notify_Request Class-Number is 195 (of form
11bbbbbb). The format of a Notify Request is:
o IPv4 Notify Request Object
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (1) | C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Notify Node Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Notify Node Address: 32 bits
The IP address of the node that should be notified when generating
an error message.
o IPv6 Notify Request Object
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 (2) | C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Notify Node Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Notify Node Address: 16 bytes
The IP address of the node that should be notified when generating
an error message.
If a message contains multiple Notify_Request objects, only the first
object is meaningful. Subsequent Notify_Request objects MAY be
ignored and SHOULD NOT be propagated.
4.2.2. Procedures
A Notify Request object may be inserted in Path or Resv messages to
indicate the address of a node that should be notified of an LSP
failure. As previously mentioned, notifications may be requested in
both the upstream and downstream directions. Upstream notification
is indicated via the inclusion of a Notify Request Object in the
corresponding Path message. Downstream notification is indicated via
the inclusion of a Notify Request Object in the corresponding Resv
message.
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A node receiving a message containing a Notify Request object SHOULD
store the Notify Node Address in the corresponding state block. If
the node is a transit node, it SHOULD also included a Notify Request
object in the outgoing Path or Resv message. The outgoing Notify
Node Address MAY be updated based on local policy.
Note that the inclusion of a Notify Request object does not guarantee
that a Notify message will be generated.
4.3. Notify Message
The Notify message provides a mechanism to inform non-adjacent nodes
of LSP related events. Notify messages are normally generated only
after a Notify Request object has been received. The Notify message
differs from the currently defined error messages (i.e., PathErr and
ResvErr messages) in that it can be "targeted" to a node other than
the immediate upstream or downstream neighbor and that it is a
generalized notification mechanism. The Notify message does not
replace existing error messages. The Notify message may be sent
either (a) normally, where non-target nodes just forward the Notify
message to the target node, similar to ResvConf processing in
[RFC2205]; or (b) encapsulated in a new IP header whose destination
is equal to the target IP address. Regardless of the transmission
mechanism, nodes receiving a Notify message not destined to the node
forward the message, unmodified, towards the target.
To support reliable delivery of the Notify message, an Ack Message
[RFC2961] is used to acknowledge the receipt of a Notify Message.
See [RFC2961] for details on reliable RSVP message delivery.
4.3.1. Required Information
The Notify message is a generalized notification message. The IP
destination address is set to the IP address of the intended
receiver. The Notify message is sent without the router alert
option. A single Notify message may contain notifications being
sent, with respect to each listed session, both upstream and
downstream.
The Notify message has a Message Type of 21. The Notify message
format is as follows:
::= []
[ [ | ] ... ]
[ ]
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::= [ ]
|
::= [ ]
[...]
::= [...]
The ERROR_SPEC object specifies the error and includes the IP address
of either the node that detected the error or the link that has
failed. See ERROR_SPEC definition in [RFC2205]. The MESSAGE_ID and
related objects are defined in [RFC2961] and are used when [RFC2961]
is supported.
4.3.2. Procedures
Notify messages are most commonly generated at nodes that detect an
error that will trigger the generation of a PathErr or ResvErr
message. If a PathErr message is to be generated and a Notify
Request object has been received in the corresponding Path message,
then a Notify message destined to the recorded node SHOULD be
generated. If a ResvErr message is to be generated and a Notify
Request object has been received in the corresponding Resv message,
then a Notify message destined to the recorded node SHOULD be
generated. As previously mentioned, a single error may generate a
Notify message in both the upstream and downstream directions. Note
that a Notify message MUST NOT be generated unless an appropriate
Notify Request object has been received.
When generating Notify messages, a node SHOULD attempt to combine
notifications being sent to the same Notify Node and that share the
same ERROR_SPEC into a single Notify message. The means by which a
node determines which information may be combined is implementation
dependent. Implementations may use event, timer based or other
approaches. If using a timer based approach, the implementation
SHOULD allow the user to configure the interval over which
notifications are combined. When using a timer based approach, a
default "notification interval" of 1 ms SHOULD be used. Notify
messages SHOULD be delivered using the reliable message delivery
mechanisms defined in [RFC2961].
Upon receiving a Notify message, the Notify Node SHOULD send a
corresponding Ack message.
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4.4. Removing State with a PathErr message
The PathErr message as defined in [RFC2205] is sent hop-by-hop to the
source of the associated Path message. Intermediate nodes may
inspect this message, but take no action upon it. In an environment
where Path messages are routed according to an IGP and that route may
change dynamically, this behavior is a fine design choice.
However, when RSVP is used with explicit routes, it is often the case
that errors can only be corrected at the source node or some other
node further upstream. In order to clean up resources, the source
must receive the PathErr and then either send a PathTear (or wait for
the messages to timeout). This causes idle resources to be held
longer than necessary and increases control message load. In a
situation where the control plane is attempting to recover from a
serious outage, both the message load and the delay in freeing
resources hamper the ability to rapidly reconverge.
The situation can be greatly improved by allowing state to be removed
by intermediate nodes on certain error conditions. To facilitate
this a new flag is defined in the ERROR_SPEC object. The two
currently defined ERROR_SPEC objects (IPv4 and IPv6 error spec
objects) each contain a one byte flag field. Within that field two
flags are defined. This specification defines a third flag, 0x04,
Path_State_Removed.
The semantics of the Path_State_Removed flag are simply that the node
forwarding the error message has removed the Path state associated
with the PathErr. By default, the Path_State_Removed flag is always
set to zero when generating or forwarding a PathErr message. A node
which encounters an error MAY set this flag if the error results in
the associated Path state being discarded. If the node setting the
flag is not the session endpoint, the node SHOULD generate a
corresponding PathTear. A node receiving a PathErr message
containing an ERROR_SPEC object with the Path_State_Removed flag set
MAY also remove the associated Path state. If the Path state is
removed the Path_State_Removed flag SHOULD be set in the outgoing
PathErr message. A node which does not remove the associated Path
state MUST NOT set the Path_State_Removed flag. A node that receives
an error with the Path_State_Removed flag set to zero MUST NOT set
this flag unless it also generates a corresponding PathTear message.
Note that the use of this flag does not result in any
interoperability incompatibilities.
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5. Explicit Label Control
The Label ERO (Explicit Route Object) and RRO (Record Route Object)
subobjects are defined to support Explicit Label Control. Note that
the Label RRO subobject was defined in [RFC3209] and is being
extended to support bidirectional LSPs.
5.1. Label ERO subobject
The Label ERO subobject is defined as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length |U| Reserved | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of L, U and Label parameters.
Type
3 Label
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The Length is always
divisible by 4.
C-Type
The C-Type of the included Label Object. Copied from the Label
Object.
5.1.1. Procedures
The Label subobject follows a subobject containing the IP address, or
the interface identifier [RFC3477], associated with the link on which
it is to be used. Up to two label subobjects may be present, one for
the downstream label and one for the upstream label. The following
SHOULD result in "Bad EXPLICIT_ROUTE object" errors:
o If the first label subobject is not preceded by a subobject
containing an IP address, or an interface identifier [RFC3477],
associated with an output link.
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o For a label subobject to follow a subobject that has the L-bit set
o On unidirectional LSP setup, for there to be a label subobject with
the U-bit set
o For there to be two label subobjects with the same U-bit values
To support the label subobject, a node must check to see if the
subobject following its associate address/interface is a label
subobject. If it is, one subobject is examined for unidirectional
LSPs and two subobjects for bidirectional LSPs. If the U-bit of the
subobject being examined is clear (0), then value of the label is
copied into a new Label_Set object. This Label_Set object MUST be
included on the corresponding outgoing Path message.
If the U-bit of the subobject 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 object" error SHOULD be generated. If the label is
acceptable, the label is copied into a new Upstream_Label object.
This Upstream_Label object MUST be included on the corresponding
outgoing Path message.
After processing, the label subobjects are removed from the ERO.
Note an implication of the above procedures is that the label
subobject should never be the first subobject in a newly received
message. If the label subobject is the the first subobject an a
received ERO, 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 subobject are outside the
scope of this document.
5.2. Label RRO subobject
The Label RRO subobject is defined as follows:
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 | Length |U| Flags | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of U and Label parameters.
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Type
3 Label
Length
See [RFC3209].
Flags
See [RFC3209].
C-Type
The C-Type of the included Label Object. Copied from the Label
Object.
5.2.1. Procedures
Label RRO subobjects are included in RROs as described in [RFC3209].
The only modification to usage and processing from [RFC3209] is that
when labels are recorded for bidirectional LSPs, label ERO subobjects
for both downstream and upstream labels MUST be included.
6. Protection Object
The use of the Protection Object is optional. The object is included
to indicate specific protection attributes of an LSP. The Protection
Object uses Class-Number 37 (of form 0bbbbbbb).
The format of the Protection Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (37)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | Link Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
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6.1. Procedures
Transit nodes processing a Path message containing a Protection
Object MUST verify that the requested protection can be satisfied by
the outgoing interface or tunnel (FA). If it cannot, the node MUST
generate a PathErr message, with a "Routing problem/Unsupported Link
Protection" indication.
7. Administrative Status Information
Administrative Status Information is carried in the Admin_Status
object. The object provides information related to the
administrative state of a particular LSP. The information is used in
two ways. In the first, the object is carried in Path and Resv
messages to indicate the administrative state of an LSP. In the
second, the object is carried in a Notification message to request
that the ingress node change the administrative state of an LSP.
7.1. Admin Status Object
The use of the Admin_Status Object is optional. It uses Class-Number
196 (of form 11bbbbbb).
The format of the Admin_Status Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(196)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R| Reserved |T|A|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC3471] for a description of parameters.
7.2. Path and Resv Message Procedures
The Admin_Status object is used to notify each node along the path of
the status of the LSP. Status information is processed by each node
based on local policy and then propagated in the corresponding
outgoing messages. The object may be inserted in either Path or Resv
messages at the discretion of the ingress (for Path messages) or
egress (for Resv messages) nodes. The absence of the object is
equivalent to receiving an object containing values all set to zero
(0).
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Transit nodes receiving a non-refresh Path or Resv message containing
an Admin_Status object, update their local state, take any
appropriate local action based on the indicated status and then
propagate the received Admin_Status object in the corresponding
outgoing Path or Resv message. If the values of an Admin_Status
object received in a Resv message differs from the values received in
a Path message then, with one exception, no local action should be
taken but the values should still be propagated. The one case where
values received in the Resv message should result in local action is
when both the received R and D bits are set, i.e., are one (1).
Edge nodes receiving a non-refresh Path or Resv message containing an
Admin_Status object, also update their local state and take any
appropriate local action based on the indicated status. When an
Admin Status object is received with the R bit set, the receiving
edge node should reflect the received values in a corresponding
outgoing message. Specifically, if an egress node receives a Path
message with the R bit of the Admin_Status object set and the node
has previously issued a Resv message corresponding to the Path
message, the node SHOULD send an updated Resv message containing an
Admin_Status object with the same values set, with the exception of
the R bit, as received in the corresponding Path message.
Furthermore, the egress node SHOULD also ensure that subsequent Resv
messages sent by the node contain the same Admin Status Object.
Additionally, if an ingress node receives a Resv message with the R
bit of the Admin_Status object set, the node SHOULD send an updated
Path message containing an Admin_Status object with the same values
set, with the exception of the R bit, as received in the
corresponding Resv message. Furthermore, the ingress node SHOULD
also ensure that subsequent Path messages sent by the node contain
the same Admin Status Object.
7.2.1. Deletion procedure
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:
1. The ingress node precedes an LSP deletion by inserting an Admin
Status Object in a Path message and setting the Reflect (R) and
Delete (D) bits.
2. Transit and egress nodes process the Admin Status Object as
described above. (Alternatively, the egress MAY respond with a
PathErr message with the Path_State_Removed flag set, see section
4.4.)
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3. Upon receiving the Admin Status Object with the Delete (D) bit set
in the Resv message, the ingress node sends a PathTear message
downstream to remove the LSP and normal RSVP processing takes
place.
In such circumstances the procedure SHOULD be followed when deleting
an LSP from the egress:
1. The egress node indicates its desire for deletion by inserting an
Admin Status Object in a Resv message and setting the Reflect (R)
and Delete (D) bits.
2. Transit nodes process the Admin Status Object as described above.
3. Upon receiving the Admin Status Object with the Delete (D) bit set
in the Resv message, the ingress node sends a PathTear message
downstream to remove the LSP and normal RSVP processing takes
place.
7.2.2. Compatibility and Error Procedures
It is possible that some nodes along an LSP will not support the
Admin Status Object. In the case of a non-supporting transit node,
the object will pass through the node unmodified and normal
processing can continue. In the case of a non-supporting egress
node, the Admin Status Object will not be reflected back in the Resv
Message. To support the case of a non-supporting egress node, the
ingress SHOULD only wait a configurable period of time for the
updated Admin Status Object in a Resv message. Once the period of
time has elapsed, the ingress node sends a PathTear message. By
default this period of time SHOULD be 30 seconds.
7.3. Notify Message Procedures
Intermediate and egress nodes may trigger the setting of
administrative status via the use of Notify messages. To accomplish
this, an intermediate or egress node generates a Notify message with
the corresponding upstream notify session information. The Admin
Status Object MUST be included in the session information, with the
appropriate bit or bits set. The Reflect (R) bit MUST NOT be set.
The Notify message may be, but is not required to be, encapsulated,
see Section 4.3.
An ingress node receiving a Notify message containing an Admin Status
Object with the Delete (D) bit set, SHOULD initiate the deletion
procedure described in the previous section. Other bits SHOULD be
propagated in an outgoing Path message as normal.
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7.3.1. Compatibility and Error Procedures
Some special processing is required in order to cover the case of
nodes that do not support the Admin Status Object and other error
conditions. Specifically, a node that sends a Notify message
containing an Admin Status Object with the Down (D) bit set MUST
verify that it receives a corresponding Path message with the Down
(D) bit set within a configurable period of time. By default this
period of time SHOULD be 30 seconds. If the node does not receive
such a Path message, it SHOULD send a PathTear message downstream and
either a ResvTear message or a PathErr message with the
Path_State_Removed flag set upstream.
8. Control Channel Separation
This section provides the protocol specific formats and procedures to
required support a control channel not being in-band with a data
channel.
8.1. Interface Identification
The choice of the data interface to use is always made by the sender
of the Path message. The choice of the data interface is indicated by
the sender of the Path message by including the data channel's
interface identifier in the message using a new RSVP_HOP object sub-
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 path
sender explicitly identifies the component interface used in each
direction. The new RSVP_HOP object is used in Resv message to
indicate the downstream node's usage of the indicated interface(s).
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8.1.1. IF_ID RSVP_HOP Objects
The format of the IPv4 IF_ID RSVP_HOP Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (3) | C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Next/Previous Hop Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Logical Interface Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the IPv6 IF_ID RSVP_HOP Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (3) | C-Type (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Next/Previous Hop Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Logical Interface Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC2205] for a description of hop address and handle fields.
See [RFC3471] for a description of parameters and encoding of
TLVs.
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8.1.2. Procedures
An IF_ID RSVP_HOP object is used in place of previously defined
RSVP_HOP objects. It is used on links where there is not a one-to-
one association of a control channel to a data channel, see
[RFC3471]. The Hop Address and Logical Interface Handle fields are
used per standard RSVP [RFC2205].
TLVs are used to identify the data channel(s) associated with an 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 the Path message. The IF_ID RSVP_HOP object SHOULD NOT be
used when no TLVs are needed.
A node receiving one or more TLVs in a Path message saves their
values and returns them in the HOP objects of subsequent Resv
messages sent to the node that originated the TLVs.
Note, the node originating an IF_ID object MUST ensure that the
selected outgoing interface, as specified in the IF_ID object, is
consistent with an ERO. A node that receives an IF_ID object SHOULD
check whether the information carried in this object is consistent
with the information carried in a received ERO, and if not it MUST
send a PathErr Message with the error code "Routing Error" and error
value of "Bad Explicit Route Object" toward the sender. This check
CANNOT be performed when the initial ERO subobject is not the
incoming interface.
8.2. Errored Interface Identification
There are cases where it is useful to indicate a specific interface
associated with an error. To support these cases the IF_ID
ERROR_SPEC Objects are defined.
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8.2.1. IF_ID ERROR_SPEC Objects
The format of the IPv4 IF_ID ERROR_SPEC Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (6) | C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Error Node Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Error Code | Error Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of the IPv6 IF_ID ERROR_SPEC Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (6) | C-Type (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Error Node Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Error Code | Error Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [RFC2205] for a description of address, flags, error code and
error value fields. See [RFC3471] for a description of parameters
and encoding of TLVs.
8.2.2. Procedures
Nodes wishing to indicate that an error is related to a specific
interface SHOULD use the appropriate IF_ID ERROR_SPEC Object in the
corresponding PathErr or ResvErr message. IF_ID ERROR_SPEC Objects
SHOULD be generated and processed as any other ERROR_SPEC Object, see
[RFC2205].
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9. Fault Handling
The handling of two types of control communication faults is
described in this section. The first, referred to as nodal faults,
relates to the case where a node losses its control state (e.g.,
after a restart) but does not loose its data forwarding state. In
the second, referred to as control channel faults, relates to the
case where control communication is lost between two nodes. The
handling of both faults is supported by the Restart_Cap object
defined below and require the use of Hello messages.
Note, the Restart_Cap object MUST NOT be sent when there is no
mechanism to detect data channel failures independent of control
channel failures.
Please note this section is derived from [PAN-RESTART].
9.1. Restart_Cap Object
The Restart_Cap Object is carried in Hello messages.
The format of the Restart_Cap Object 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(131)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Restart Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Recovery Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Restart Time: 32 bits
Restart Time is measured in milliseconds. Restart Time SHOULD be
set to the sum of the time it takes the sender of the object to
restart its RSVP-TE component (to the point where it can exchange
RSVP Hello with its neighbors) and the communication channel that
is used for RSVP communication. A value of 0xffffffff indicates
that the restart of the sender's control plane may occur over an
indeterminate interval and that the operation of its data plane is
unaffected by control plane failures. The method used to ensure
continued data plane operation is outside the scope of this
document.
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Recovery Time: 32 bits
The period of time, in milliseconds, that the sender desires for
the recipient to re-synchronize RSVP and MPLS forwarding state
with the sender after the re-establishment of Hello
synchronization. A value of zero (0) indicates that MPLS
forwarding state was not preserved across a particular reboot.
9.2. Processing of Restart_Cap Object
Nodes supporting state recovery advertise this capability by carrying
the Restart_Cap object in Hello messages. Such nodes MUST include
the Restart_Cap object in all Hello messages. (Note that this
includes Hello messages containing ACK objects.) Usage of the
special case Recovery Time values is described in greater detail
below.
When a node receives a Hello message with the Restart_Cap object, it
SHOULD record the values of the parameters received.
9.3. Modification to Hello Processing to Support State Recovery
When a node determines that RSVP communication with a neighbor has
been lost, and the node previously learned that the neighbor supports
state recovery, the node SHOULD wait at least the amount of time
indicated by the Restart Time indicated by the neighbor before
invoking procedures related to communication loss. A node MAY wait a
different amount of time based on local policy or configuration
information.
During this waiting period, all Hello messages MUST be sent with a
Dst_Instance value set to zero (0), and Src_Instance should be
unchanged. While waiting, the node SHOULD also preserve the RSVP and
MPLS forwarding state for (already) established LSPs that traverse
the link(s) between the node and the neighbor. In a sense with
respect to established LSPs the node behaves as if it continues to
receive periodic RSVP refresh messages from the neighbor. The node
MAY clear RSVP and forwarding state for the LSPs that are in the
process of being established when their refresh timers expire.
Refreshing of Resv and Path state SHOULD be suppressed during this
waiting period.
During this waiting period, the node MAY inform upstream nodes of the
communication loss via a PathErr and/or upstream Notify message with
"Control Channel Degraded State" indication. If such notification
has been sent, then upon restoration of the control channel the node
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MUST inform other nodes of the restoration via a PathErr and/or
upstream Notify message with "Control Channel Active State"
indication. (Specific error codes have been assigned by IANA.)
When a new Hello message is received from the neighbor, the node must
determine if the fault was limited to the control channel or was a
nodal fault. This determination is based on the Src_Instance
received from the neighbor. If the value is different than the value
that was received from the neighbor prior to the fault, then the
neighbor should be treated as if it has restarted. Otherwise, the
the fault was limited control channel. Procedures for handling each
case are described below.
9.4. Control Channel Faults
In the case of control channel faults, the node SHOULD refresh all
state shared with the neighbor. Summary Refreshes [RFC2961] with the
ACK_Desired flag set SHOULD be used, if supported. Note that if a
large number of messages are need, some pacing should be applied.
All state SHOULD be refreshed within the Recovery time advertised by
the neighbor.
9.5. Nodal Faults
Recovering from nodal faults uses one new object and other existing
protocol messages and objects.
9.5.1. Recovery Label
The Recovery_Label object is used during the nodal fault recovery
process. The format of a Recovery_Label object is identical to a
generalized label. A Recovery_Label object uses Class-Number 34 (of
form 0bbbbbbb) and the C-Type of the label being suggested.
9.5.2. Procedures for the Restarting node
After a node restarts its control plane, a node that supports state
recovery SHOULD check whether it was able to preserve its MPLS
forwarding state. If no forwarding state from prior to the restart
was preserved, then the node MUST set the Recovery Time to 0 in the
Hello message the node sends to its neighbors.
If the forwarding state was preserved, then the node initiates the
state recovery process. The period during which a node is prepared
to support the recovery process is referred to as the Recovery
Period. The total duration of the Recovery Period is advertised by
the recovering node in the Recovery Time parameter of the Restart_Cap
object. The Recovery Time MUST be set to the duration of the
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Recovery Period in all Hello messages sent during the Recovery
Period. State that is not resynchronized during the Recovery Period
SHOULD be removed at the end of the Period.
Note that if during Hello synchronization the restarting node
determines that a neighbor does not support state recovery, and the
restarting node maintains its MPLS forwarding state on a per neighbor
basis, the restarting node should immediately consider the Recovery
Period with that neighbor completed. Forwarding state may be
considered to be maintained on a per neighbor basis when per
interface labels are used on point-to-point interfaces.
When a node receives a Path message during the Recovery Period, the
node first checks if it has an RSVP state associated with the
message. If the state is found, then the node handles this message
according to previously defined procedures.
If the RSVP state is not found, and the message does not carry a
Recovery_Label object, the node treats this as a setup for a new LSP,
and handles it according to previously defined procedures.
If the RSVP state is not found, and the message carries a
Recovery_Label object, the node searches its MPLS forwarding table
(the one that was preserved across the restart) for an entry whose
incoming interface matches the Path message and whose incoming label
is equal to the label carried in the Recovery_Label object.
If the MPLS forwarding table entry is not found, the node treats this
as a setup for a new LSP, and handles it according to previously
defined procedures.
If the MPLS forwarding table entry is found, the appropriate RSVP
state is created, the entry is bound to the LSP associated with the
message, and related forwarding state should be considered as valid
and refreshed. Normal Path message processing should also be
conducted. When sending the corresponding outgoing Path message the
node SHOULD include a Suggested_Label object with a label value
matching the outgoing label from the now restored forwarding entry.
The outgoing interface SHOULD also be selected based on the
forwarding entry. In the special case where a restarting node also
has a restating downstream neighbor, a Recovery_Label object should
be used instead of a Suggested_Label object.
Additionally, for bidirectional LSPs, the node extracts the label
from the UPSTREAM_LABEL object carried in the received Path message,
and searches its MPLS forwarding table for an entry whose outgoing
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label is equal to the label carried in the object (in the case of
link bundling, this may also involved first identifying the
appropriate incoming component link).
If the MPLS forwarding table entry is not found, the node treats this
as a setup for a new LSP, and handles it according to previously
defined procedures.
If the MPLS forwarding table entry is found, the entry is bound to
the LSP associated with the Path message, and the entry should be
considered to be re-synchronized. In addition, if the node is not
the tail-end of the LSP, the corresponding outgoing Path messages is
sent with the incoming label from that entry carried in the
UPSTREAM_LABEL object.
During the Recovery Period, Resv messages are processed normally with
two exceptions. In the case that a forwarding entry is recovered, no
new label or resource allocation is required while processing the
Resv message. The second exception is that ResvErr messages SHOULD
NOT be generated when a Resv message with no matching Path state is
received. In this case the Resv message SHOULD just be silently
discarded.
9.5.3. Procedures for the Neighbor of a Restarting node
The following specifies the procedures that apply when the node
reestablishes communication with the neighbor's control plane within
the Restart Time, the node determines (using the procedures defined
in Section 5 of [RFC3209]) that the neighbor's control plane has
restarted, and the neighbor was able to preserve its forwarding state
across the restart (as was indicated by a non-zero Recovery Time
carried in the Restart_Cap object of the RSVP Hello messages received
from the neighbor). Note, a Restart Time value of 0xffffffff
indicates an infinite Restart Time interval.
Upon detecting a restart with a neighbor that supports state
recovery, a node SHOULD refresh all Path state shared with that
neighbor. The outgoing Path messages MUST include a Recovery_Label
object containing a label value corresponding to the label value
received in the most recently received corresponding Resv message.
All Path state SHOULD be refreshed within approximately 1/2 of the
Recovery time advertised by the restarted neighbor. If there are
many LSP's going through the restarting node, the neighbor node
should avoid sending Path messages in a short time interval, as to
avoid unnecessary stressing the restarting node's CPU. Instead, it
should spread the messages across 1/2 the Recovery Time interval.
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After detecting a restart of a neighbor that supports state recovery,
all Resv state shared with the restarting node MUST NOT be refreshed
until a corresponding Path message is received. This requires
suppression of normal Resv and Summary Refresh processing to the
neighbor during the Recovery Time advertised by the restarted
neighbor. As soon as a corresponding Path message is received a Resv
message SHOULD be generated and normal state processing SHOULD be
re-enabled.
10. RSVP Message Formats and Handling
This message summarizes RSVP message formats and handling as modified
by GMPLS.
10.1. RSVP Message Formats
This section presents the RSVP message related formats as modified by
this document. Where they differ, formats for unidirectional LSPs
are presented separately from bidirectional LSPs. Unmodified formats
are not listed. Again, MESSAGE_ID and related objects are defined in
[RFC2961].
The format of a Path message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ]
[ ]
[ ... ]
[ ]
[ ]
[ ]
[ ... ]
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The format of the sender description for unidirectional LSPs is:
::=
[ ]
[ ]
[ ]
[ ]
The format of the sender description for bidirectional LSPs is:
::=
[ ]
[ ]
[ ]
[ ]
The format of a PathErr message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ... ]
[ ... ]
The format of a Resv message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ] [ ]
[ ]
[ ]
[ ... ]
