Internet Draft
Network Working Group Peter Ashwood-Smith (Nortel Networks Corp.)
Internet Draft Ayan Banerjee (Calient Networks)
Expiration Date: May 2001 Lou Berger (Movaz Networks)
Greg Bernstein (Ciena Corporation)
John Drake (Calient Networks)
Yanhe Fan (Axiowave Networks)
Kireeti Kompella (Juniper Networks, Inc.)
Eric Mannie (GTS)
Jonathan P. Lang (Calient Networks)
Bala Rajagopalan (Tellium, Inc.)
Yakov Rekhter (Cisco Systems)
Debanjan Saha (Tellium, Inc.)
Vishal Sharma (Tellabs)
George Swallow (Cisco Systems)
Z. Bo Tang (Tellium, Inc.)
November 2000
Generalized MPLS Signaling - RSVP-TE Extensions
draft-ietf-mpls-generalized-rsvp-te-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract
This document describes extensions to RSVP-TE signaling required to
support Generalized MPLS. Generalized MPLS extends MPLS to encompass
time-division (e.g. SONET ADMs), wavelength (optical lambdas) and
spatial switching (e.g. incoming port or fiber to outgoing port or
fiber). This document presents an RSVP-TE specific description of
the extensions. A CR-LDP specific description can be found in
[GMPLS-LDP]. A generic functional description is presented in
[GMPLS-SIG].
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Contents
1 Introduction .............................................. 3
2 Label Related Formats .................................... 3
2.1 Generalized Label Request ................................ 3
2.1.1 Generalized Label Request with SONET/SDH Label Range ...... 4
2.1.2 Procedures ................................................ 4
2.1.3 Bandwidth Encoding ........................................ 5
2.2 Generalized Label ......................................... 5
2.2.1 Procedures ................................................ 6
2.3 Waveband Switching ........................................ 6
2.3.1 Procedures ................................................ 7
2.4 Suggested Label ........................................... 7
2.5 Label Set ................................................. 7
2.5.1 Procedures ................................................ 8
3 Bidirectional LSPs ........................................ 9
3.1 Procedures ................................................ 9
3.2 Contention Resolution ..................................... 10
4 Notification .............................................. 10
4.1 Notify Request Object ..................................... 10
4.1.1 Required Information ...................................... 11
4.1.2 Procedures ................................................ 11
4.2 Notify Message ............................................ 12
4.2.1 Required Information ...................................... 12
4.2.2 Procedures ................................................ 13
4.3 Removing State with a PathErr message ..................... 13
5 Explicit Label Control .................................... 14
5.1 Procedures ................................................ 15
6 RSVP Message Formats ...................................... 16
7 Acknowledgments ........................................... 17
8 Security Considerations ................................... 17
9 References ................................................ 18
10 Authors' Addresses ........................................ 18
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Changes from previous version:
o Moved protocol specific details into two documents, one for RSVP-TE
and one for CR-LDP.
o Fixed bandwidth encodings
o Revised Notify message format to disambiguate upstream and
downstream notifications.
o Minor text cleanup
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 [GMPLS-SIG]. This document presents RSVP-TE
specific formats and mechanisms needed to support all four classes of
interfaces. CR-LDP extensions can be found in [GMPLS-LDP].
[GMPLS-SIG] should be viewed as a companion document to this
document. The format of this document parallels [GMPLS-SIG]. In
addition to the other features of Generalized MPLS, this document
also defines RSVP-TE specific features to support rapid failure
notification, see Section 4.
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
A Path message SHOULD contain as specific an LSP 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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (19)|C-Type (4)[TBA]|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [GMPLS-SIG] for a description of parameters.
2.1.1. Generalized Label Request with SONET/SDH Label Range
The format of a Generalized Label Request with SONET/SDH Label Range
(in RSVP) 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 (5)[TBA]|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Link Prot.Flags| G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RGT | RT | Reserved | RNC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [GMPLS-SIG] for a description of parameters.
2.1.2. Procedures
A node processing the Path message containing the 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 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
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requested LSP Encoding Type. If encoding cannot be supported, the
node MUST generate a PathErr message, with a "Routing
problem/Unsupported Encoding" indication.
Transit nodes MUST verify that the outgoing interface or tunnel can
support the requested Link Protection Flags. If it cannot, the node
MUST generate a PathErr message, with a "Routing problem/Unsupported
Link Protection" 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 GPID"
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.
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.
2.1.3. Bandwidth Encoding
Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC
objects. See [GMPLS-SIG] 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. Other bandwidth/service related
parameters in the object are ignored and carried transparently.
2.2. Generalized Label
The format of a Generalized Label 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 |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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See [GMPLS-SIG] for a description of parameters and encoding of
SDH, SONET, port, wavelength and other labels.
2.2.1. 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.
2.3. Waveband Switching
Waveband switching uses the same format as the generalized label, see
section 2.2. For compatibility reasons, a new RSVP c-type (3) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num (16)| C-Type (3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Waveband Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
See [GMPLS-SIG] for a description of parameters.
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2.3.1. Procedures
The procedures defined in Section 2.2.1 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. 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.
2.4. Suggested Label
The format of a suggested label is identical to a generalized label.
It is used in Path messages. Suggested Label uses a new Class-Number
(TBD of form 10bbbbbb) and the C-type of the label being suggested.
Errors in received Suggested Labels MUST be ignored. This includes
any received inconsistent or unacceptable values.
2.5. Label Set
The Label_Set object uses a Class-Number TBA (of form 0bbbbbbb) and
the C-type of the label type being described.
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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(TBA)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Label Type | Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel 1 |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: : :
: : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel N |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Label Type: 8 bits
Indicates the type and format of the labels carried in the
object. Values match the C-Type of the appropriate Label
object.
See [GMPLS-SIG] for a description of other parameters.
2.5.1. 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.
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 a CI-capable interface will restrict
its choice of labels to one which is in the Label Set. The CI-
capable receiver 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
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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 for a CI-incapable interface, 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 for an interface which is CI-
incapable it has no other choice than to use the same physical label
(wavelength/band) as received in the Resv. In this case, the use and
propagation of a Label Set will significantly reduce the chances that
this allocation will fail when CI-incapable nodes are traversed.
3. Bidirectional LSPs
Bidirectional LSP setup is indicated by the presence of an Upstream
Label in the Path message. An Upstream Label has the same format as
the generalized label, see Section 2.2. The Upstream Label uses
Class-Number TBD (of form 0bbbbbbb) and the C-type of the label being
suggested.
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 is added to the Path
message. The Upstream Label 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 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.
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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/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 LSPs 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 defines three signaling extensions that modify error
handling, enable expedited notification of failures and other events
to nodes responsible for restoring failed LSPs. The first extension,
the Notify Request object, identifies where event notifications are
to be sent. The second, the Notify message, provides for general
event notification. The final extension allows for the removal of
Path state on handling of PathErr messages.
4.1. Notify Request Object
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.
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4.1.1. Required Information
The Notify Request Object may be carried in Path or Resv Messages,
see Section 6. The NOTIFY_REQUEST Class-Number is TBA (of form
11bbbbbb). The format of a Notify 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(TBD)| 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.
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.
4.1.2. 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.
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.
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4.2. Notify Message
The Notify message provides a mechanism to inform non-adjacent nodes
of LSP related events. Notify messages are only generated after a
Notify Request object has been received. The Notify message differs
from the currently defined error messages (i.e., PathErr and ResvErr
messages of RSVP) 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 [RSVP];
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
[RSVP-RR] is used to acknowledge the receipt of a Notify Message.
See [RSVP-RR] for details on reliable RSVP message delivery.
4.2.1. 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 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
object is defined in [RSVP-RR].
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4.2.2. Procedures
Notify messages are 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 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 [RSVP-RR].
Upon receiving a Notify message, the Notify Node SHOULD send a
corresponding Ack message.
4.3. 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 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.
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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.
5. Explicit Label Control
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 [GMPLS-SIG] for a description of L, U and Label parameters.
Type
3 Label
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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. Procedures
The Label subobject follows a subobject containing the IP address, or
the interface identifier [MPLS-UNNUM], associated with the link on
which it is to be used. The preceding subobject must be a strict
object. 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:
- If the first label subobject is not preceded by a subobject
containing an IP address, or a interface identifier
[MPLS-UNNUM], associated with an output link.
- For a label subobject to follow a subobject that has the L-bit
set
- On unidirectional LSP setup, for there to be a label subobject
with the U-bit set
- 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 it's 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
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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.
6. 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.
The format of a Path message is as follows:
::= [ ]
[ ]
[ ... ]
[ ]
[ ]
[ ... ]
The format of the sender description for unidirectional LSPs is:
::=
[ ]
[ ]
[ ]
The format of the sender description for bidirectional LSPs is:
::=
[ ]
[ ]
[ ]
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The format of a Resv message is as follows:
::= [ ]
[ ] [ ]
[ ]
[ ... ]