Network Working Group Adrian Farrel (Editor)
Internet Draft Old Dog Consulting
Category: Standards Track Dimitri Papadimitriou
Expires: January 2005 Alcatel
Jean-Philippe Vasseur
Cisco Systems, Inc.
Arthi Ayyangar
Juniper Networks
July 2004
Encoding of Attributes for Multiprotocol Label Switching (MPLS)
Label Switched Path (LSP) Establishment Using RSVP-TE
draft-ietf-mpls-rsvpte-attributes-04.txt
Status of this Memo
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Abstract
Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs) may
be established using the Resource Reservation Protocol Traffic
Engineering extensions (RSVP-TE). This protocol includes an object
(the SESSION_ATTRIBUTE object) which carries a flags field used to
indicate options and attributes of the LSP. That flags field has
eight bits allowing for eight options to be set. Recent proposals in
many documents that extend RSVP-TE have suggested uses for each of
the previously unused bits.
This document defines a new object for RSVP-TE messages that allows
the signaling of further attribute bits and also the carriage of
arbitrary attribute parameters to make RSVP-TE easily extensible to
support new requirements. Additionally, this document defines a way
to record the attributes applied to the LSP on a hop-by-hop basis.
The object mechanisms defined in this document are equally applicable
to Generalized MPLS (GMPLS) Packet Switch Capable (PSC) LSPs and to
GMPLS non-PSC LSPs.
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draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
0. Change History
This section to be removed before publication as an RFC.
0.1 Changes from 03 to 04 Version
- New IPR and copyright text
- Update referneces
0.2 Changes from 02 to 03 Version
- Allow LSP_ATTRIBUTES object on Resv message.
- Document inheritance rules.
- Add table of Contents.
- New IPR and Copyright boiler-plate.
0.3 Changes from 01 to 02 Version
- Minor typographical changes.
0.4 Changes from 00 to 01 Version
- Change Attributes Flags TLV to be variable length so that more bits
can easily be added in the future.
- Define default behaviors for bits absent from the TLV and for
absence of the TLV.
- Clarify the IANA requirements for tracking Attributes Flags bits.
- Introduce RRO Attributes Subobject and describe usage.
- Move Fast Reroute reference to informational.
- Update security considerations to handle new RRO subobject
- Remove section that explained the need for this document in
advance of any definitive bit definitions.
- Tighten rules for processing LSP_ATTRIBUTES object in cases where
TLVs are unknown or unsupported.
- Clarify that LSP Attributes apply to individual LSPs and not to
entire sessions.
Contents
1. Introduction and Problem Statement 3
1.1 Applicability to Generalized MPLS 4
1.2 A Rejected Alternate Solution 4
2. Terminology 5
3. Attributes TLVs 5
3.1 Attributes Flags TLV 5
4. LSP_ATTRIBUTES Object 6
4.1 Format 7
4.2 Generic Processing Rules for Path Messages 7
4.3 Generic Processing Rules for Resv Messages 7
5. LSP_REQUIRED_ATTRIBUTES Object 8
5.1 Format 8
5.2 Generic Processing Rules 9
6. Inheritance Rules 9
7. Recording Attributes Per-LSP 9
7.1 Requirements 9
7.2 RRO Attributes Subobject 10
7.3 Procedures 10
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7.3.1 Subobject Presence Rules 10
7.3.2 Reporting Compliance with LSP Attributes 11
7.3.3 Reporting Per-Hop Attributes 11
7.3.4 Default Behavior 11
8. Summary of Attribute Bit Allocation 11
9. Message Formats 12
10. IANA Considerations 13
10.1 New RSVP C-Nums and C-Types 13
10.2 New TLV Space 13
10.3 Attributes Flags 14
10.4 SESSION_ATTRIBUTE Flags Field 14
10.5 New Error Codes 14
10.6 New Record Route Subobject Identifier 14
11. Security Considerations 15
12. Acknowledgements 15
13. Intellectual Property Consideration 15
13.1 IPR Disclosure Acknowledgement 16
14. Normative References 16
15. Informative References 16
16. Authors' Addresses 16
17. Full Copyright Statement 17
1. Introduction and Problem Statement
Traffic Engineered Multiprotocol Label Switching (MPLS) Label
Switched Paths (LSPs) [RFC3031] may be set up using the Path message
of the RSVP-TE signaling protocol [RFC3209]. The Path message
includes the SESSION_ATTRIBUTE object which carries a flags field
used to indicate desired options and attributes of the LSP.
The flags field in the SESSION_ATTRIBUTE object has eight bits. Just
three of those bits are assigned in [RFC3209]. A further two bits are
assigned in [FRR] for fast re-reroute functionality leaving only
three bits available. Several recent proposals and Internet Drafts
have demonstrated that there is a high demand for the use of the
other three bits. Some, if not all, of those proposals are likely to
go forward as RFCs resulting in depletion or near depletion of the
flags field and a consequent difficulty in signaling new options and
attributes that may be developed in the future.
This document defines a new object for RSVP-TE messages that allows
the signaling of further attributes bits. The new object is
constructed from TLVs, and a new TLV is defined to carry a variable
number of attributes bits. Because of the nature of the TLV
construction the object is flexible and allows the future definition
of:
- further bit flags if further, distinct uses are discovered
- arbitrary options and attributes parameters carried as individual
TLVs.
Note that the LSP Attributes defined in this document are
specifically scoped to an LSP. They may be set differently on
separate LSPs with the same Tunnel ID between the same source and
destination (that is, within the same Session).
It is noted that some options and attributes do not need to be
acted on by all Label Switched Routers (LSRs) along the path of the
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draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
LSP. In particular, these options and attributes may apply only to
key LSRs on the path such as the ingress and egress. Special transit
LSRs, such as Area or AS Border Routers (ABRs/ASBRs) may also fall
into this category. This means that the new options and attributes
should be signaled transparently, and only examined at those points
that need to act on them.
On the other hand, other options and attributes may require action
at all transit LSRs along the path of the LSP. Inability to support
the required attributes by one of those transit LSRs may require the
LSR to refuse the establishment of the LSP.
These considerations are particularly important in the context of
backwards compatibility. In general, it should be possible to provide
new MPLS services across a legacy network without upgrading those
LSRs that do not need to participate actively in the new services.
Moreover, some features just require action on specific intermediate
hops, and not on every visited LSR.
Note that options already specified for the SESSION_ATTRIBUTE object
in pre-existing RFCs are not migrated to the new mechanisms described
in this document.
RSVP includes a way for unrecognized objects to be transparently
forwarded by transit nodes without them refusing the incoming
protocol messages and without the objects being stripped from the
outgoing protocol message (see [RFC2205] Section 3.10). This
capability extends to RSVP-TE and provides a good way to ensure that
only those LSRs that understand a particular object examine it.
This document distinguishes between options and attributes that are
only required at key LSRs along the path of the LSP, and those that
must be acted on by every LSR along the LSP. Two LSP Attributes
objects are defined in this document: the first may be passed
transparently by LSRs that do not recognize it, the second must cause
LSP setup failure with the generation of a PathErr message with an
appropriate Error Code if an LSR does not recognize it.
1.1 Applicability to Generalized MPLS
The RSVP-TE signaling protocol also forms the basis of a signaling
protocol for Generalized MPLS (GMPLS) as described in [RFC3471] and
[RFC3473]. The extensions described in this document are intended to
be equally applicable to MPLS and GMPLS.
1.2 A Rejected Alternate Solution
A rejected alternate solution was to define a new C-Type for the
existing SESSION_ATTRIBUTE object. This new C-Type could allow a
larger Flags field and address the immediate problem.
This solution was rejected because:
- A new C-Type is not backward compatible with deployed
implementations that expect to see a C-Type of 1 or 7. It is
important that any solution be capable of carrying new attributes
transparently across legacy LSRs if those LSRs are not required to
act on the attributes.
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- Support for arbitrary attributes parameters through TLVs would
have meant a significant change of substance to the existing
object.
2. Terminology
This document uses terminology from the MPLS architecture document
[RFC3031] and from the RSVP-TE protocol specification [RFC3209] which
inherits from the RSVP specification [RFC2205]. It also makes uses of
the Generalized MPLS RSVP-TE terminology introduced in [RFC3471] and
[RFC3473].
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 [RFC2219].
3. Attributes TLVs
Attributes carried by the new objects defined in this document are
encoded within TLVs. One or more TLVs may be present in each object.
There are no ordering rules for TLVs and no interpretation should be
placed on the order in which TLVs are received.
Each TLV is encoded 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Value //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
The identifier of the TLV.
Length
The length of the value field in bytes. Thus if no value
field is present the length field contains the value zero.
Each value field must be zero padded at the end to take it
up to a four byte boundary - the padding is not included in
the length so that a one byte value would be encoded in an
eight byte TLV with length field set to one.
Value
The data for the TLV padded as described above.
3.1 Attributes Flags TLV
This document defines only one TLV type value. Type 1 indicates the
Attributes Flags TLV. Other TLV types may be defined in future with
type values assigned by IANA.
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The Attributes Flags TLV may be present in an LSP_ATTRIBUTES object
and/or an LSP_REQUIRED_ATTRIBUTES object defined in Sections 4 and 5.
The bits in the TLV represent the same attributes regardless of which
object carries the TLV. Documents that define individual bits MUST
specify whether the bit may be set in one object or the other, or
both. It is not expected that a bit will be set in both objects on a
single Path message at the same time, but this is not ruled out by
this document.
The Attributes Flags TLV value field is a variable length array of
flags numbered from the MSB as bit zero. The length field for this
TLV is always a multiple of 4 bytes, regardless of the number bits
carried.
Unassigned bits are considered as reserved and MUST be set to zero
on transmission by the originator of the object. Bits not contained
in the TLV MUST be assumed to be set to zero. If the TLV is absent
either because it is not contained in the LSP_ATTRIBUTES or LSP_
REQUIRED_ATTRIBUTES object, or because those objects are themselves
absent, all processing MUST be performed as though the bits were
present and set to zero.
No bits are defined in this document. The assignment of bits is
managed by IANA.
4. LSP_ATTRIBUTES Object
The LSP_ATTRIBUTES object is used to signal attributes required in
support of an LSP, or to indicate the nature or use of an LSP where
that information is not required to be acted on by all transit LSRs.
Specifically, if an LSR does not support the object, it forwards it
unexamined and unchanged. This facilitates the exchange of attributes
across legacy networks that do not support this new object.
This object effectively extends the flags field in the SESSION_
ATTRIBUTE object and allows for the future inclusion of more complex
objects through TLVs.
Note that some function may require an LSR to inspect both the
SESSION_ATTRIBUTE object, and the LSP_ATTRIBUTES or
LSP_REQUIRED_ATTRIBUTES object.
The LSP_ATTRIBUTES object may also be used to report LSP operational
state on a Resv even when no LSP_ATTRIBUTES or LSP_REQUIRED_
ATTRIBUTES object was carried on the corresponding Path message. The
object is added or updated by LSRs that support the object. LSRs that
do not understand the object or have nothing to report, do not add
the object and forward it unchanged on Resv messages that they
generate.
The LSP_ATTRIBUTES object class is TBD of the form 11bbbbbb. This
C-Num value (see Section 8) ensures that LSRs that do not recognize
the object pass it on transparently.
One C-Type is defined, C-Type = 1 for LSP Attributes.
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This object is optional and may be placed on Path messages to convey
additional information about the desired attributes of the LSP, and.
on Resv messages to report operational state.
4.1 Format
LSP_ATTRIBUTES class = TBD, C-Type = 1
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Attributes TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Attributes TLVs are encoded as described in Section 3.
4.2 Generic Processing Rules for Path Messages
An LSR that does not support this object will pass it on unaltered
because of the C-Num.
An LSR that does support this object, but does not recognize a TLV
type code carried in this object MUST pass the TLV on unaltered
in the LSP_ATTRIBUTES object that it places in the Path message
that it sends downstream.
An LSR that does support this object and recognizes a TLV but does
not support the attribute defined by the TLV MUST act as specified in
the document that defines the TLV.
An LSR that supports the Attributes Flags TLV, but does not
recognize a bit set in the Attributes Flags TLV MUST forward the
TLV unchanged.
An LSR that supports the Attributes Flags TLV and recognizes a bit
that is set but does not support the indicated attribute MUST act as
specified in the document that defines the bit.
4.3 Generic Processing Rules for Resv Messages
An LSR that wishes to report operational status of an LSP may include
this object in a Resv message, or update the object that is already
carried in a Resv message.
Note that this usage reports the state of the entire LSP and not the
state of the LSP at an individual LSR. This latter function is
achieved using the LSP Attributes subobject of the Record Route
object as described in Section 7.
The bits in the Attributes TLV may be used to report operational
status for the whole LSP. For example, an egress may report a
particular status by setting a bit. LSRs within the network that
determine that this status has not been achieved may clear the bit
as they forward the Resv message.
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Observe that LSRs that do not support the object or do not support
the function characterized by a particular bit in the Attributes TLV
will not clear the bit when forwarding the Resv. Thus, care must be
taken in defining the usage of this object on a Resv. The usage of
an individual bit in the Attributes TLV of the LSP_ATTRIBUTES object
on a Resv must be fully defined in the document that defines the bit.
Additional TLVs may also be defined to be carried in this object on
a Resv.
An LSR that does not support this object will pass it on unaltered
because of the C-Num.
5. LSP_REQUIRED_ATTRIBUTES Object
The LSP_REQUIRED_ATTRIBUTES object is used to signal attributes
required in support of an LSP, or to indicate the nature or use of
an LSP where that information MUST be inspected at each transit LSR.
Specifically, each transit LSR MUST examine the attributes in the
LSP_REQUIRED_ATTRIBUTES object and MUST NOT forward the object
transparently.
This object effectively extends the flags field in the SESSION_
ATTRIBUTE object and allows for the future inclusion of more complex
objects through TLVs. It complements the LSP_ATTRIBUTES object.
The LSP_REQUIRED_ATTRIBUTES object class is TBD of the form 0bbbbbbb.
This C-Num value ensures that LSRs that do not recognize the object
reject the LSP setup effectively saying that they do not support the
attributes requested. This means that this object SHOULD only be used
for attributes that require support at some transit LSRs and so
require examination at all transit LSRs. See Section 4 for how end-
to-end and selective attributes are signaled.
One C-Type is defined, C-Type = 1 for LSP Required Attributes.
This object is optional and may be placed on Path messages to convey
additional information about the desired attributes of the LSP.
5.1 Format
LSP_REQUIRED_ATTRIBUTES class = TBD, C-Type = 1
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Attributes TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Attributes TLVs are encoded as described in Section 3.
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5.2 Generic Processing Rules
An LSR that does not support this object will use a PathErr to reject
the Path message based on the C-Num using the error code "Unknown
Object Class".
An LSR that does not recognize a TLV type code carried in this object
MUST reject the Path message using a PathErr with Error Code
"Unknown Attributes TLV" and Error Value set to the value of the
unknown TLV type code.
An LSR that does not recognize a bit set in the Attributes Flags
TLV MUST reject the Path message using a PathErr with Error Code
"Unknown Attributes Bit" and Error Value set to the bit number of
the unknown bit in the Attributes Flags.
An LSR that recognizes an attribute, however encoded, but which does
not support that attribute MUST act according to the behavior
specified in the document that defines that specific attribute.
Note that this object is not used on a Resv. In order to report the
status of an LSP either the LSP_ATTRIBUTES object on a Resv or the
Attributes subobject in the Record Route object (see Section 7) must
be used.
6. Inheritance Rules
In certain circumstances, when reaching an LSP region boundary, a
FA-LSP (see [MPLS-HIER]) is initially setup to allow the establishment
of the LSP carrying the LSP ATTRIBUTES and/or LSP_REQUIRED_ATTRIBUTES
objects. In this case, when the boundary LSR supports LSP_ATTRIBUTES
and LSP_REQUIRED_ATTRIBUTES processing, the FA-LSP MAY upon local
policy inherit a subset of the Attributes TLVs, in particular when the
FA-LSP belongs to the same switching capability class than the
triggering LSP.
When these conditions are met, the LSP_ATTRIBUTES and/or
LSP_REQUIRED_ATTRIBUTES objects are simply copied with the inherited
Attributes TLVs in the Path message used to establish the FA-LSP. By
default (and in order to simplify deployment), none of the incoming
LSP Attributes TLV are considered as inheritable. Note that when the
FA-LSP establishment itself requires one or more Attributes TLVs, an
'OR' operation is performed with the inherited set of values.
Documents that define individual bits for the LSP Attributes Flags
TLV MUST specify whether these bits MAY be inherited or not (including
the condition to be met in order for this inheritance to occur). The
same applies for any other TLV that will be defined following the
rules specified in Section 3.
7. Recording Attributes Per-LSP
7.1 Requirements
In some circumstances it is useful to determine which of the
requested LSP attributes have been applied at which LSRs along the
path of the LSP. For example, an attribute may be requested in the
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LSP_ATTRIBUTES object such that LSRs that do not support the object
are not required to support the attribute or provide the requested
function. In this case, it may be useful to the ingress LSR to know
which LSRs acted on the request and which ignored it.
Additionally, there may be other qualities that need to be reported
on a hop-by-hop basis. These are currently indicated in the Flags
field of RRO subobjects. Since there are only eight bits available
in this field, and since some are already assigned and there is also
likely to be an increase in allocations in new documents, there is a
need for some other method to report per-hop attributes.
7.2 RRO Attributes Subobject
The RRO Attributes Subobject may be carried in the RECORD_ROUTE
object if it is present. The subobject uses the standard format of
an RRO subobject.
The length is variable as for the Attributes Flags TLV. The content
is the same as the Attribute Flags TLV - that is, it is a series of
bit flags.
There is a one-to-one correspondence between bits in the Attributes
Flags TLV and the RRO Attributes Subobject. If a bit is only required
in one of the two places, it is reserved in the other place. See
the procedures sections, below, for more information.
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 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Attribute Flags //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
0x?? TBD RRO Attribute Subobject
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. This length must be a
multiple of 4 and must be at least 8.
Attribute Flags
The attribute flags recorded for the specific hop.
7.3 Procedures
7.3.1 Subobject Presence Rules
The Attributes subobject is pushed onto the RECORD_ROUTE object
immediately prior to pushing the node's IP address or link
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identifier. Thus, if label recording is being used, the Attributes
subobject SHOULD be pushed onto the RECORD_ROUTE object after the
Record Label subobject(s).
A node MUST NOT push an Attributes subobject on to the RECORD_ROUTE
object without also pushing an IPv4, IPv6 or Unnumbered Interface ID
subobject.
This means that an Attributes subobject is bound to the LSR
identified by the subobject found in the RRO immediately before the
Attributes subobject.
If the new subobject causes the RRO to be too big to fit in a Path
(or Resv) message, the processing MUST be as described in [RFC3209].
If more than one Attributes subobject is found between a pair of
subobjects that identify LSRs, only the first one found (that is, the
nearest to the stop of the stack) SHALL have any meaning within the
context of this document. All such subobjects MUST be forwarded
unmodified by transit LSRs.
7.3.2 Reporting Compliance with LSP Attributes
To report compliance with an attribute requested in the Attributes
Flags TLV, an LSR MAY set the corresponding bit (see Section 8) in
the Attributes subobject. To report non-compliance, an LSR MAY clear
the corresponding bit in the Attributes subobject.
The requirement to report compliance MUST be specified in the
document that defines the usage of any bit. This will reduce to a
statement of whether hop-by-hop acknowledgement is required.
7.3.3 Reporting Per-Hop Attributes
To report a per-hop attribute, an LSR sets the appropriate bit in the
Attributes subobject.
The requirement to report a per-hop attribute MUST be specified in
the document that defines the usage of the bit.
7.3.4 Default Behavior
By default all bits in an Attributes subobject SHOULD be set to zero.
If a received Attribute subobject is not long enough to include a
specific numbered bit, that bit MUST be treated as though present and
as if set to zero.
If the RRO subobject is not present for a hop in the LSP, all bits
MUST be assumed to be set to zero.
8. Summary of Attribute Bit Allocation
This document defines two uses of per-LSP attribute flag bit fields.
The bit numbering in the Attributes Flags TLV and the RRO Attributes
subobject is identical. That is, the same attribute is indicated by
the same bit in both places. This means that only a single registry
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of bits is maintained.
The consequence is a degree of clarity in implementation and
registration.
Note, however, that it is not always the case that a bit will be used
in both the Attributes Flags TLV and the RRO Attributes subobject.
For example, an attribute may be requested using the Attributes Flags
TLV, but there is no requirement to report the handling of the
attribute on a hop-by-hop basis. Conversely, there may be a
requirement to report the attributes of an LSP on a hop-by-hop basis,
but there is no corresponding request attribute.
In these cases, a single bit number is still assigned for both the
Attributes Flags TLV and the RRO Attributes subobject even though the
bit may be irrelevant in either the Attributes Flags or the RRO
Attributes subobject. The document that defines the usage of the new
bit MUST state in which places it is used and MUST handle a default
setting of zero.
9. Message Formats
The LSP_ATTRIBUTES object and the LSP_REQUIRED_ATTRIBUTES object MAY
be carried in a Path message. The LSP_ATTRIBUTES object MAY be
carried in a Resv message.
The order of objects in RSVP-TE messages is recommended, but
implementations must be capable of receiving the objects in any
meaningful order.
On a Path message, the LSP_ATTRIBUTES object and LSP_REQUIRED_
ATTRIBUTES objects are RECOMMENDED to be placed immediately after the
SESSION_ATTRIBUTE object if it is present, or otherwise immediately
after the LABEL_REQUEST object.
If both the LSP_ATTRIBUTES object and the LSP_REQUIRED_ATTRIBUTES
object are present, the LSP_REQUIRED_ATTRIBUTES object is RECOMMENDED
to be placed first.
LSRs SHOULD be prepared to receive these objects in any order in any
position within a Path message. Subsequent instances of these objects
within a Path message SHOULD be ignored and those objects MUST be
forwarded unchanged.
On a Resv message, the LSP_ATTRIBUTES object is placed in the flow
descriptor and is associated with the FILTER_SPEC object that
precedes it. It is RECOMMENDED that the LSP_ATTRIBUTES object be
placed immediately after the LABEL object.
LSRs SHOULD be prepared to receive this object in any order in any
position within a Resv message subject to the previous note. Only
one instance of the LSP_ATTRIBUTES object is meaningful within the
context of a FILTER_SPEC object. Subsequent instances of the object
SHOULD be ignored and MUST be forwarded unchanged.
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10. IANA Considerations
10.1 New RSVP C-Nums and C-Types
Two new RSVP C-Nums are defined in this document and should be
assigned by IANA.
o LSP_ATTRIBUTES object
The C-Num should be of the form 11bbbbbb so that LSRs that do not
recognize the object will ignore the object but forward it,
unexamined and unmodified, in all messages resulting from this
message.
One C-Type is defined for this object and should be assigned by
IANA.
o LSP Attributes TLVs
Recommended C-Type value 1.
o LSP_REQUIRED_ATTRIBUTES object
The C-Num should be of the form 0bbbbbbb so that LSRs that do not
recognize the object will reject the message that carries it with
an "Unknown Object Class" error.
One C-Type is defined for this object and should be assigned by
IANA.
o LSP Required Attributes TLVs
Recommended C-Type value 1.
10.2 New TLV Space
The two new objects referenced above are constructed from TLVs. Each
TLV includes a 16-bit type identifier (the T-field). The same T-field
values are applicable to both objects.
IANA is requested to manage TLV type identifiers as follows:
- TLV Type (T-field value)
- TLV Name
- Whether allowed on LSP_ATTRIBUTES object
- Whether allowed on LSP_REQUIRED_ATTRIBUTES object.
This document defines one TLV type as follows:
- TLV Type = 1
- TLV Name = Attributes Flags TLV
- allowed on LSP_ATTRIBUTES object
- allowed on LSP_REQUIRED_ATTRIBUTES object.
Farrel, Papadimitriou, Vasseur and Ayyangar Page 13
draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
10.3 Attributes Flags
This document provides new attributes bit flags for use in other
documents that specify new RSVP-TE attributes. These flags are
present in the Attributes Flags TLV referenced in the previous
section.
IANA is requested to manage the space of attributes bit flags
numbering them in the usual IETF notation starting at zero and
continuing through 2039.
Each bit should be tracked with the following qualities:
- Bit number
- Defining RFC
- Name of bit
- Whether there is meaning in the Attribute Flags TLV on a Path
- Whether there is meaning in the Attribute Flags TLV on a Resv
- Whether there is meaning in the RRO Attributes Subobject.
Note that this means that all bits in the Attribute Flags TLV and the
RRO Attributes Subobject use the same bit number regardless of
whether they are used in one or both places. Thus, only one list of
bits is required to be maintained. (It would be meaningless in the
context of this document for a bit to have no meaning in neither the
Attribute Flags TLV nor the RRO Attributes Subobject.)
10.4 SESSION_ATTRIBUTE Flags Field
This document does not make any alterations to the definition of the
existing SESSION_ATTRIBUTE object nor to the definition of meanings
assigned to the flags in the Flags field of that object. These flags
are assigned meanings in various other RFCs and Internet Drafts.
It is suggested that IANA manage the allocation of meaning to the
bits in the Flags field of the SESSION_ATTRIBUTE object to prevent
accidental double allocation of any one bit.
10.5 New Error Codes
This document defines the following new error codes and error values.
Numeric values should be assigned by IANA.
Error Code Error Value
"Unknown Attributes TLV" Identifies the unknown TLV type code.
"Unknown Attributes Bit" Identifies the unknown Attribute Bit.
10.6 New Record Route Subobject Identifier
A new subobject is defined for inclusion in the RECORD_ROUTE object.
The RRO Attributes subobject is identified by a Type value of TBD.
Farrel, Papadimitriou, Vasseur and Ayyangar Page 14
draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
11. Security Considerations
This document adds two new objects to the RSVP Path message as used
in MPLS and GMPLS signaling, and a new subobject to the RECORD_ROUTE
object carried on may RSVP messages. It does not introduce any new
direct security issues and the reader is referred to the security
considerations expressed in [RFC2205], [RFC3209] and [RFC3473].
It is of passing note that any signaling request that indicates the
functional preferences or attributes of an MPLS LSP may provide
anyone with unauthorized access to the contents of the message with
information about the LSP that an administrator may wish to keep
secret. Although this document adds new objects for signaling desired
LSP attributes, it does not contribute to this issue which can
only be satisfactorily handled by encrypting the content of the
signaling message.
Similarly, the addition of attribute recording information to the
RRO may reveal information about the status of the LSP and the
capabilities of individual LSRs that operators wish to keep secret.
The same strategy that applies to other RRO subobjects also applies
here. Note, however, that there is a tension between notifying the
head end of the LSP status at transit LSRs, and hiding the existence
or identity of the transit LSRs.
12. Acknowledgements
Credit to the OSPF Working Group for inspiration from their solution
to a similar problem. Thanks to Rahul Aggarwal for his careful review
and support of this work. Thanks also to Raymond Zhang, Kireeti
Kompella, Philip Matthews, Jim Gibson and Alan Kullberg for their
input. As so often, thanks to John Drake for useful offline
discussions.
13. Intellectual Property Consideration
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
Farrel, Papadimitriou, Vasseur and Ayyangar Page 15
draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
14. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, R. (Ed.), Zhang, L., Berson, S., Herzog, S.
and S. Jamin, "Resource ReserVation Protocol --
Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions
to RSVP for LSP Tunnels", RFC 3209, December 2001.
[RFC3471] Berger, L. (Editor), "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, January 2003.
[RFC3473] Berger, L. (Editor), "Generalized MPLS Signaling -
RSVP-TE Extensions", RFC 3473 January 2003.
[RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004.
[RFC3668] Bradner, S., Ed., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3668, February 2004.
15. Informative References
[RFC2026] Bradner, S., "The Internet Standards Process
-- Revision 3", RFC 2026, October 1996.
[RFC3031] Rosen, E., Viswanathan, A., and Callon, R.,
"Multiprotocol Label Switching
Architecture", RFC 3031, January 2001.
[FRR] Pan, P. (Ed.), "Fast Reroute Extensions to RSVP-TE for
LSP Tunnels", <draft-ietf-mpls-rsvp-lsp-fastreroute-06
.txt>, Internet Draft, work in progress.
[MPLS-HIER] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
MPLS TE", Work in Progress.
16. Authors' Addresses
Adrian Farrel
Old Dog Consulting
Phone: +44 (0) 1978 860944
EMail: adrian@olddog.co.uk
Dimitri Papadimitriou (Alcatel)
Fr. Wellesplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 240-8491
EMail: dimitri.papadimitriou@alcatel.be
Farrel, Papadimitriou, Vasseur and Ayyangar Page 16
draft-ietf-mpls-rsvpte-attributes-04.txt July 2004
Jean Philippe Vasseur
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
EMail: jpv@cisco.com
Arthi Ayyangar
Juniper Networks, Inc.
1194 N.Mathilda Ave
Sunnyvale, CA 94089
USA
EMail: arthi@juniper.net
17. Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
18. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Farrel, Papadimitriou, Vasseur and Ayyangar Page 17
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