draft-ietf-pce-pcep-xro-01.txt   draft-ietf-pce-pcep-xro-02.txt 
Network Working Group E. Oki Network Working Group E. Oki
Internet Draft NTT Internet Draft NTT
Category: Standards Track A. Farrel Category: Standards Track A. Farrel
Expires: January 2008 Old Dog Consulting Expires: March 2008 Old Dog Consulting
September 2007
Extensions to the Path Computation Element Communication Protocol Extensions to the Path Computation Element Communication Protocol
(PCEP) for Route Exclusions (PCEP) for Route Exclusions
draft-ietf-pce-pcep-xro-01.txt draft-ietf-pce-pcep-xro-02.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 42 skipping to change at page 1, line 46
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
The Path Computation Element (PCE) provides functions of path The Path Computation Element (PCE) provides functions of path
computation in support of traffic engineering in Multi-Protocol computation in support of traffic engineering in Multi-Protocol
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.
When a Path Computation Client (PCC) requests a PCE for a route, it When a Path Computation Client (PCC) requests a PCE for a route, it
may be useful for the PCC to specify, as constraints to the path may be useful for the PCC to specify, as constraints to the path
computation abstract nodes, resources, and Shared Risk Link Groups computation, abstract nodes, resources, and Shared Risk Link Groups
(SRLGs) that are to be explicitly excluded from the computed route. (SRLGs) that are to be explicitly excluded from the computed route.
Such constraints are termed route exclusions. Such constraints are termed route exclusions.
The PCE Communication Protocol (PCEP) is designed as a communication The PCE Communication Protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs. This document presents PCEP protocol between PCCs and PCEs. This document presents PCEP
extensions for route exclusions. extensions for route exclusions.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119 this document are to be interpreted as described in RFC 2119
[RFC2119]. [RFC2119].
Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction...................................................2
2. Protocol Procedures and Extensions.............................3 2. Protocol Procedures and Extensions.............................3
2.1. Exclude Route Object (XRO)..................................3 2.1. Exclude Route Object (XRO)..................................4
2.1.1. Definition................................................3 2.1.1. Definition................................................4
2.1.2. Processing Rules..........................................7 2.1.2. Processing Rules..........................................8
2.2. Explicit Route Exclusion....................................8 2.2. Explicit Route Exclusion....................................9
2.2.1. Definition..................................................8 2.2.1. Definition..................................................9
2.2.2. Processing Rules............................................8 2.2.2. Processing Rules...........................................10
3. Exclude Route with Confidentiality.............................9 3. Exclude Route with Confidentiality............................11
3.1. Exclude Route Object (XRO) carrying Path Key................9 3.1. Exclude Route Object (XRO) Carrying Path Key...............11
3.3.1. Definition..................................................9 3.1.1. Definition.................................................11
3.3.2. Processing Rules...........................................10 3.1.2. Processing Rules...........................................11
4. IANA Considerations...........................................10 4. IANA Considerations...........................................12
4.1. PCEP Objects...............................................10 4.1. PCEP Objects...............................................12
4.2. Error Object Field Values..................................11 4.2. Explicit Exclusion Route Subobject (EXRS)..................13
5. Manageability considerations..................................11 4.3. Error Object Field Values..................................13
6. Security Considerations.......................................11 5. Manageability Considerations..................................13
7. References....................................................11 6. Security Considerations.......................................13
7.1. Normative Reference........................................11 7. References....................................................14
7.2. Informative Reference......................................12 7.1. Normative Reference........................................14
8. Acknowledgements..............................................12 7.2. Informative Reference......................................14
9. AuthorsEAddresses............................................12 8. Acknowledgements..............................................15
10. Intellectual Property Statement.............................12 9. Authors' Addresses............................................15
10. Intellectual Property Statement.............................15
1. Introduction 1. Introduction
The Path Computation Element (PCE) defined in [RFC4655] is an entity The Path Computation Element (PCE) defined in [RFC4655] is an entity
that is capable of computing a network path or route based on a that is capable of computing a network path or route based on a
network graph, and applying computational constraints. A Path network graph, and applying computational constraints. A Path
Oki and Farrel Expires March 2008 2
Computation Client (PCC) may make requests to a PCE for paths to be Computation Client (PCC) may make requests to a PCE for paths to be
computed. computed.
When a PCC requests a PCE for a route, it may be useful for the PCC When a PCC requests a PCE for a route, it may be useful for the PCC
to specify abstract nodes, resources, and Shared Risk Link Groups to specify abstract nodes, resources, and Shared Risk Link Groups
(SRLGs) that are to be explicitly excluded from the route. (SRLGs) that are to be explicitly excluded from the route.
For example, disjoint paths for inter-domain LSPs may be computed by For example, disjoint paths for inter-domain LSPs may be computed by
cooperation between PCEs, each of which computes segments of the cooperation between PCEs, each of which computes segments of the
paths across one domain. In order to achieve path computation for a paths across one domain. In order to achieve path computation for a
secondary (backup) path, a PCE may act as a PCC to request another secondary (backup) path, a PCE may act as a PCC to request another
PCE for a route that must be a node/link/SRLG disjoint from the PCE for a route that must be node/link/SRLG disjoint from the
primary (working) path. Another example is where a network operator primary (working) path. Another example is where a network operator
wants a path to avoid specified nodes for administrative reasons, wants a path to avoid specified nodes for administrative reasons,
perhaps because the specified nodes will be out-of-services in the perhaps because the specified nodes will be out-of-services in the
near future. near future.
[RFC4657] specifies generic requirements for a communication [RFC4657] specifies generic requirements for a communication
protocol between PCCs and PCEs. Generic constraints described in protocol between PCCs and PCEs. Generic constraints described in
[RFC4657] include route exclusions for links, nodes, and SRLGs. That [RFC4657] include route exclusions for links, nodes, and SRLGs. That
is, the requirement for support of route exclusions within the PCC- is, the requirement for support of route exclusions within the PCC-
PCE communication protocol is already established. PCE communication protocol is already established.
Oki and Farrel Expires January 2008 2
The PCE communication protocol (PCEP) is designed as a communication The PCE communication protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs and is defined in [PCEP]. This protocol between PCCs and PCEs and is defined in [PCEP]. This
document presents PCEP extensions to satisfy the requirements for document presents PCEP extensions to satisfy the requirements for
route exclusions as described in Sections 5.1.4 and 5.1.16 of route exclusions as described in Sections 5.1.4 and 5.1.16 of
[RFC4657]. [RFC4657].
Note that MPLS-TE and GMPLS signaling extensions for communicating Note that MPLS-TE and GMPLS signaling extensions for communicating
route exclusions between network nodes for specific Label Switched route exclusions between network nodes for specific Label Switched
Paths (LSPs) are described in [RFC4874]. Route exclusions may be Paths (LSPs) are described in [RFC4874]. Route exclusions may be
specified during provisioning requests for specific LSPs setting the specified during provisioning requests for specific LSPs by setting
mplsTunnelHopInclude object of MPLS-TE-STD-MIB defined in [RFC3812] the mplsTunnelHopInclude object of MPLS-TE-STD-MIB defined in
to false. [RFC3812] to false (2).
2. Protocol Procedures and Extensions 2. Protocol Procedures and Extensions
This section describes the procedures adopted by a PCE handling a This section describes the procedures adopted by a PCE handling a
request for path computation with route exclusions received from a request for path computation with route exclusions received from a
PCC, and defines how those exclusions are encoded. PCC, and defines how those exclusions are encoded.
There are two types of route exclusion described in [RFC4874]. There are two types of route exclusion described in [RFC4874].
1. Exclusion of certain abstract nodes or resources on the whole 1. Exclusion of certain abstract nodes or resources from the whole
path. This set of abstract nodes is referred to as the Exclude path. This set of abstract nodes is referred to as the Exclude
Route List. Route List.
2. Exclusion of certain abstract nodes or resources between a 2. Exclusion of certain abstract nodes or resources between a
Oki and Farrel Expires March 2008 3
specific pair of abstract nodes present in an explicit path. Such specific pair of abstract nodes present in an explicit path. Such
specific exclusions are referred to as an Explicit Route specific exclusions are referred to as an Explicit Route
Exclusion. Exclusion.
This document defines protocol extensions to allow a PCC to specify This document defines protocol extensions to allow a PCC to specify
both types of route exclusions to a PCE on a path computation both types of route exclusions to a PCE on a path computation
request. request.
A new PCEP object is defined as the Exclude Route Object (XRO) to A new PCEP object, the Exclude Route Object (XRO), is defined to
convey the Exclude Route List. The existing Include Route Object convey the Exclude Route List. The existing Include Route Object
(IRO) in PCEP [PCEP] is modified by introducing a new IRO subobject, (IRO) in PCEP [PCEP] is modified by introducing a new IRO subobject,
the Explicit Exclusion Route Subobject (EXRS), to convey Explicit the Explicit Exclusion Route Subobject (EXRS), to convey Explicit
Route Exclusions. Route Exclusions.
2.1. Exclude Route Object (XRO) 2.1. Exclude Route Object (XRO)
2.1.1. Definition 2.1.1. Definition
The XRO is OPTIONAL and MAY be carried within PCReq and PCRep The XRO is OPTIONAL and MAY be carried within PCReq and PCRep
messages. messages.
When present in a PCReq message, the XRO provides a list of network When present in a PCReq message, the XRO provides a list of network
resources that the PCE is requested to exclude from the path that it resources that the PCE is requested to exclude from the path that it
computes. Flags associated with each list member instruct the PCE as computes. Flags associated with each list member instruct the PCE as
to whether the network resources must be excluded from the computed to whether the network resources must be excluded from the computed
path or whether the PCE should make best efforts to exclude the path, or whether the PCE should make best efforts to exclude the
resources from the computed path. resources from the computed path.
Oki and Farrel Expires January 2008 3 The XRO MAY be used on a PCRep message that carries the NO-PATH
The XRO MAY be used on PCRep message with the NO-PATH object to object (i.e., one that reports a path computation failure) to
indicate the set of elements of the original XRO that prevented the indicate the set of elements of the original XRO that prevented the
PCE from finding a path. The XRO MAY also be used on a PCRep message PCE from finding a path.
for a successful path computation when the PCE wishes to provide a
set of exclusions to be signaled during LSP setup using the The XRO MAY also be used on a PCRep message for a successful path
extensions to RSVP-TE [RFC4874]. computation when the PCE wishes to provide a set of exclusions to be
signaled during LSP setup using the extensions to RSVP-TE [RFC4874].
The XRO Object-Class is to be assigned by IANA (recommended The XRO Object-Class is to be assigned by IANA (recommended
value=17) value=17)
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The XRO Object-Type is to be assigned by IANA (recommended value=1) The XRO Object-Type is to be assigned by IANA (recommended value=1)
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |F| | Reserved | Flags |F|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// (Subobjects) // // (Subobjects) //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: XRO body format Figure 1: XRO body format
Reserved: 16 bits EMUST be set to zero on transmission and SHOULD
be ignored on receipt.
Flags: 16 bits - The following flags are currently defined: Flags: 16 bits - The following flags are currently defined:
F (Fail - 1 bit): when set, the requesting PCC requires the F (Fail - 1 bit): when set, the requesting PCC requires the
computation of a new path for an existing TE LSP that has failed. If computation of a new path for an existing TE LSP that has failed.
the F bit is set, the path of the existing TE LSP MUST be provided If the F bit is set, the path of the existing TE LSP MUST be
in the PCReq message by means of an RRO object defined in [PCEP]. provided in the PCReq message by means of an RRO object defined in
This allows the path computation to take into account the previous [PCEP]. This allows the path computation to take into account the
path and reserved resources to avoid double bandwidth booking should previous path and reserved resources to avoid double bandwidth
the TED have not yet been updated or the corresponding resources not booking should the TED have not yet been updated or the
be yet been released. This will usually be used in conjunction with corresponding resources not be yet been released. This will
the exclusion from the path computation of the failed resource that usually be used in conjunction with the exclusion from the path
caused the LSP to fail. computation of the failed resource that caused the LSP to fail.
Subobjects. The XRO is up made of one or more subobject(s). An XRO Subobjects. The XRO is up made of one or more subobject(s). An XRO
with no subobjects MUST NOT be sent and SHOULD be ignored on receipt. with no subobjects MUST NOT be sent and SHOULD be ignored on receipt.
In the following subobject definitions a set of fields have In the following subobject definitions a set of fields have
consistent meaning as follows: consistent meaning as follows:
X X
The X-bit indicates whether the exclusion is mandatory or The X-bit indicates whether the exclusion is mandatory or
desired. 0 indicates that the resource specified MUST be desired. 0 indicates that the resource specified MUST be
excluded from the path computed by the PCE. 1 indicates that excluded from the path computed by the PCE. 1 indicates that
the resource specified SHOULD be excluded from the path the
computed by the PCE, but MAY be included subject to PCE policy resource specified SHOULD be excluded from the path computed by
and the absence of a viable path that meets the other the PCE, but MAY be included subject to PCE policy and the
constraints and excludes the resource. absence of a viable path that meets the other constraints and
excludes the resource.
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Type Type
The type of the subobject. The following subobject types are The type of the subobject. The following subobject types are
defined. defined.
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Type Subobject Type Subobject
-------------+------------------------------- -------------+-------------------------------
1 IPv4 prefix 1 IPv4 prefix
2 IPv6 prefix 2 IPv6 prefix
3 Unnumbered Interface ID 3 Unnumbered Interface ID
4 Autonomous system number 4 Autonomous system number
5 SRLG 5 SRLG
Length Length
The length of the subobject including the Type and Length The length of the subobject including the Type and Length
skipping to change at line 247 skipping to change at line 261
addresses matching a prefix. If the subobject indicates a addresses matching a prefix. If the subobject indicates a
single address, the prefix length MUST be set to the full single address, the prefix length MUST be set to the full
length of the address. length of the address.
Attribute Attribute
The Attribute field indicates how the exclusion subobject is to The Attribute field indicates how the exclusion subobject is to
be interpreted. be interpreted.
0 Interface 0 Interface
The subobject is to be interpreted as an interface or set of The subobject is to be interpreted as an interface or set of
interfaces. All interfaces identified by the subobject are to interfaces. All interfaces identified by the subobject are
to
be excluded from the computed path according to the setting be excluded from the computed path according to the setting
of the X-bit. This value is valid only for subobject types 1, of the X-bit. This value is valid only for subobject types 1,
2, and 3. 2, and 3.
1 Node 1 Node
The subobject is to be interpreted as a node or set of nodes. The subobject is to be interpreted as a node or set of nodes.
All nodes identified by the subobject are to be excluded from All nodes identified by the subobject are to be excluded
the computed path according to the setting of the X-bit. This from
the computed path according to the setting of the X-bit.
This
value is valid only for subobject types 1, 2, 3, and 4. value is valid only for subobject types 1, 2, 3, and 4.
2 SRLG 2 SRLG
The subobject identifies an SRLG explicitly or indicates all The subobject identifies an SRLG explicitly or indicates all
of the SRLGs associated with the resource or resources of the SRLGs associated with the resource or resources
identified by the subobject. Resources that share any SRLG identified by the subobject. Resources that share any SRLG
with those identified are to be excluded from the computed with those identified are to be excluded from the computed
path according to the setting path according to the setting of the X-bit. This value is
of the X-bit. This value is valid for all subobjects. valid for all subobjects.
Reserved Reserved
Reserved fields MUST be transmitted as zero and SHOULD be Reserved fields within subobjects MUST be transmitted as zero
ignored on receipt.
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and SHOULD be ignored on receipt.
The subobjects are encoded as follows: The subobjects are encoded as follows:
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IPv4 prefix Subobject IPv4 prefix Subobject
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 1 | Length | IPv4 address (4 bytes) | |X| Type = 1 | Length | IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address (continued) | Prefix Length | Attribute | | IPv4 address (continued) | Prefix Length | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at line 314 skipping to change at line 332
|X| Type = 3 | Length | Reserved | Attribute | |X| Type = 3 | Length | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Router ID | | TE Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID | | Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The TE Router ID and Interface ID fields are as defined in The TE Router ID and Interface ID fields are as defined in
[RFC3477]. [RFC3477].
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Autonomous System Number Subobject Autonomous System Number Subobject
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 4 | Length | Reserved | Attribute | |X| Type = 4 | Length | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional AS Number High Octets| 2-Octet AS Number | | Optional AS Number High Octets| 2-Octet AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If a two-octet AS number is used, the optional AS Number High If a two-octet AS number is used, the optional AS Number High
Octets MUST be set to zero. Octets MUST be set to zero.
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SRLG Subobject SRLG Subobject
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type = 5 | Length | SRLG Id (4 bytes) | |X| Type = 5 | Length | SRLG Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG Id (continued) | Reserved | Attribute | | SRLG Id (continued) | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at line 364 skipping to change at line 382
use the first one in the message and MUST ignore subsequent use the first one in the message and MUST ignore subsequent
instances. instances.
If the PCE does not recognize the XRO it MUST return a PCErr message If the PCE does not recognize the XRO it MUST return a PCErr message
with Error-Type "Unknown Object" as described in [PCEP]. with Error-Type "Unknown Object" as described in [PCEP].
If the PCE is unwilling on unable to process the XRO it MUST return If the PCE is unwilling on unable to process the XRO it MUST return
a PCErr message with the Error-Type "Not supported object" and a PCErr message with the Error-Type "Not supported object" and
follow the relevant procedures described in [PCEP]. follow the relevant procedures described in [PCEP].
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If the PCE processes the XRO and attempts to compute a path, it MUST If the PCE processes the XRO and attempts to compute a path, it MUST
adhere to the requested exclusions as expressed in the XRO. That is, adhere to the requested exclusions as expressed in the XRO. That is,
the returned path MUST NOT include any resources encoded with the X- the returned path MUST NOT include any resources encoded with the X-
bit clear, and SHOULD NOT include any with the X-bit set unless bit clear, and SHOULD NOT include any with the X-bit set unless
alternate paths that match the other constraints expressed in the alternate paths that match the other constraints expressed in the
PCReq are unavailable. PCReq are unavailable.
When a PCE returns a path in a PCRep it MAY also supply an XRO. An When a PCE returns a path in a PCRep it MAY also supply an XRO. An
XRO in a PCRep message with the NO-PATH object indicates that the XRO in a PCRep message with the NO-PATH object indicates that the
set of elements of the original XRO prevented the PCE from finding a set of elements of the original XRO prevented the PCE from finding a
path. On the other hand, if an XRO is present in a PCRep message path. On the other hand, if an XRO is present in a PCRep message
without a NO-PATH object, the PCC SHOULD apply the contents using without a NO-PATH object, the PCC SHOULD apply the contents using
the same rules as in [RFC4874] and the PCC or a corresponding LSR the same rules as in [RFC4874] and the PCC or a corresponding LSR
SHOULD signal an RSVP-TE XRO to indicate the exclusions that SHOULD signal an RSVP-TE XRO to indicate the exclusions that
downstream LSRs should apply. This may be particularly useful in downstream LSRs should apply. This may be particularly useful in
per-domain path computation scenarios. per-domain path computation scenarios [PD-PATH].
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In the event that no suitable path can be computed and the PCE
returns a PCRep message containing a NO-PATH object, the PCE MAY
also include an XRO that lists one or more subobjects from the
original XRO that have contributed to the PCE's inability to select
a path.
2.2. Explicit Route Exclusion 2.2. Explicit Route Exclusion
2.2.1. Definition 2.2.1. Definition
Explicit Route Exclusion defines network elements that must not or Explicit Route Exclusion defines network elements that must not or
should not be used on the path between two abstract nodes or should not be used on the path between two abstract nodes or
resources explicitly indicated in the Include Route Object (IRO) resources explicitly indicated in the Include Route Object (IRO)
[PCEP]. This information is encoded by defining a new subobject for [PCEP]. This information is encoded by defining a new subobject for
the IRO. the IRO.
The new IRO subobject, the Explicit Exclusion Route Subobject (EXRS), The new IRO subobject, the Explicit Exclusion Route Subobject (EXRS),
has type defined by IANA (see Section 3.). The EXRS contains one or has type defined by IANA (see Section 3.). The EXRS contains one or
more subobjects in its own right. An EXRS MUST NOT be sent with no more subobjects in its own right. An EXRS MUST NOT be sent with no
subobjects, and if received with no subobjects MUST be ignored. subobjects, and if received with no subobjects MUST be ignored.
skipping to change at line 417 skipping to change at line 431
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// One or more EXRS subobjects // // One or more EXRS subobjects //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L L
MUST be set to zero on transmission and MUST be ignored on MUST be set to zero on transmission and MUST be ignored on
receipt. receipt.
Oki and Farrel Expires March 2008 9
Reserved Reserved
MUST be set to zero on transmission and MUST be ignored on MUST be set to zero on transmission and SHOULD be ignored on
receipt. receipt.
The EXRS subobject may carry any of the subobjects defined for The EXRS subobject may carry any of the subobjects defined for
inclusion in the XRO by this document or by future documents. The inclusion in the XRO by this document or by future documents. The
meanings of the fields of the XRO subobjects are unchanged when the meanings of the fields of the XRO subobjects are unchanged when the
subobjects are included in an EXRS, except that scope of the subobjects are included in an EXRS, except that scope of the
exclusion is limited to the single hop between the previous and exclusion is limited to the single hop between the previous and
subsequent elements in the IRO. subsequent elements in the IRO.
2.2.2. Processing Rules 2.2.2. Processing Rules
A PCC that supplies a partial explicit route to a PCE in an IRO MAY A PCC that supplies a partial explicit route to a PCE in an IRO MAY
also specify explicit exclusions by including one or more EXRSes in also specify explicit exclusions by including one or more EXRSes in
the IRO. the IRO.
If a PCE parses an IRO in a received PCReq message and encounters an If a PCE parses an IRO in a received PCReq message and encounters an
EXRS and does not recognize the subobject it MUST respond with a EXRS and does not recognize the subobject it MUST respond with a
PCErr message using the Error-Type "Unrecognized IRO subobject" and PCErr message using the Error-Type "Unrecognized IRO subobject" and
set the Error-Value to the subobject type code of the EXRS (see set the Error-Value to the subobject type code of the EXRS.
Section 3).
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If a PCE parses an IRO and encounters an EXRS that it recognizes, If a PCE parses an IRO and encounters an EXRS that it recognizes,
but detects an EXRS subobject that it does not recognize it MUST act but detects an EXRS subobject that it does not recognize it MUST act
according to the setting of the X-bit in the subobject. If the X-bit according to the setting of the X-bit in the subobject. If the X-bit
is clear, the PCE MUST respond with a PCErr with Error-Type is clear, the PCE MUST respond with a PCErr with Error-Type
"Unrecognized EXRS subobject" and set the Error-Value to the EXRS "Unrecognized EXRS subobject" and set the Error-Value to the EXRS
subobject type code (see Section 3). If the X-bit is set, the PCE subobject type code (see Section 4). If the X-bit is set, the PCE
MAY respond with a PCErr as already stated or MAY ignore the EXRS MAY respond with a PCErr as already stated or MAY ignore the EXRS
subobject: this choice is a local policy decision. subobject: this choice is a local policy decision.
If a PCE parses an IRO and encounters an EXRS subobject that it If a PCE parses an IRO and encounters an EXRS subobject that it
recognizes, it MUST act according to the requirements expressed in recognizes, it MUST act according to the requirements expressed in
the subobject. That is, if the X-bit is clear, the PCE MUST NOT the subobject. That is, if the X-bit is clear, the PCE MUST NOT
produce a path that includes any resource identified by the EXRS produce a path that includes any resource identified by the EXRS
subobject in the path between the previous abstract node in the IRO subobject in the path between the previous abstract node in the IRO
and the next abstract node in the IRO. If the X-bit is set, the PCE and the next abstract node in the IRO. If the X-bit is set, the PCE
SHOULD NOT produce a path that includes any resource identified by SHOULD NOT produce a path that includes any resource identified by
the EXRS subobject in the path between the previous abstract node in the EXRS subobject in the path between the previous abstract node in
the IRO and the next abstract node in the IRO unless it is not the IRO and the next abstract node in the IRO unless it is not
possible to construct a path that avoids that resource while still possible to construct a path that avoids that resource while still
complying with the other constraints expressed in the PCReq message. complying with the other constraints expressed in the PCReq message.
A successful path computation reported in a PCRep message MUST A successful path computation reported in a PCRep message MUST
include an ERO to specify the path that has been computed. That ERO include an ERO to specify the path that has been computed as
MAY contain specific route exclusions using the EXRS as specified in specified in [PCEP]. That ERO MAY contain specific route exclusions
[RFC4874]. using the EXRS as specified in [RFC4874].
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If the path computation fails and a PCErr is returned with a NO-PATH If the path computation fails and a PCErr is returned with a NO-PATH
object, the PCE MAY include an IRO to report the hops that could not object, the PCE MAY include an IRO to report the hops that could not
be complied with, and that IRO MAY include EXRSes. be complied with as described in [PCEP], and that IRO MAY include
EXRSes.
3. Exclude Route with Confidentiality 3. Exclude Route with Confidentiality
3.1. Exclude Route Object (XRO) carrying Path Key 3.1. Exclude Route Object (XRO) Carrying Path Key
3.3.1. Definition 3.1.1. Definition
In PCE-based inter-domain diverse path computation, an XRO may be In PCE-based inter-domain diverse path computation, an XRO may be
used to find a backup (secondary) path. A sequential path used to find a backup (secondary) path. A sequential path
computation approach may be applied for this purpose, where a computation approach may be applied for this purpose, where a
working (primary) path route is computed first and a backup path working (primary) path route is computed first and a backup path
route that must be a node/link/SRLG disjoint route from the working route that must be a node/link/SRLG disjoint route from the working
path is then computed [INTER-DOMAIN-REC-ANA]. Backward Recursive path is then computed [INTER-DOMAIN-REC-ANA]. Backward Recursive
Path Computation (BRPC) may be used for inter-domain path Path Computation (BRPC) may be used for inter-domain path
computation [BRPC]. computation [BRPC].
skipping to change at line 499 skipping to change at line 514
instead of explicitly expressing the computed route, Path Key instead of explicitly expressing the computed route, Path Key
Subobjects (PKSs) [PCE-PATH-KEY] are carried in the Explicit Route Subobjects (PKSs) [PCE-PATH-KEY] are carried in the Explicit Route
Object (ERO) in the PCRep Message. Object (ERO) in the PCRep Message.
Therefore, during inter-domain diverse path computation, it may be Therefore, during inter-domain diverse path computation, it may be
necessary to request diversity from a path that is not fully known necessary to request diversity from a path that is not fully known
and where a segment of the path is represented by a PKS. This means and where a segment of the path is represented by a PKS. This means
that a PKS may be present as a subobject of the XRO on a PCReq that a PKS may be present as a subobject of the XRO on a PCReq
message. message.
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The format and definition of PKS when it appears as an XRO subobject The format and definition of PKS when it appears as an XRO subobject
are as defined in [PCE-PATH-KEY], except for the definition of L bit. are as defined in [PCE-PATH-KEY], except for the definition of L bit.
The L bit of the PKS subobject in the XRO is defined as follows. The L bit of the PKS subobject in the XRO is defined as follows.
L L
The L bit MUST be ignored. The L bit MUST be ignored.
3.3.2. Processing Rules 3.1.2. Processing Rules
Consider that BRPC is applied for both working and backup path Consider that BRPC is applied for both working and backup path
computation in a sequential manner. First, PCC requests PCE for the computation in a sequential manner. First, PCC requests PCE for the
computation of a working path. After BRPC processing has completed, computation of a working path. After BRPC processing has completed,
the PCC receives the results of the working-path computation the PCC receives the results of the working-path computation
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expressed in an ERO in a PCRep message. The ERO may include PKSs if expressed in an ERO in a PCRep message. The ERO may include PKSs if
certain segments of the path are to be kept confidential. certain segments of the path are to be kept confidential.
For backup path computation, when the PCC constructs a PCReq Message, For backup path computation, when the PCC constructs a PCReq Message,
it includes the entire working-path in the XRO so that the computed it includes the entire working-path in the XRO so that the computed
path is node/link disjoint from the working path. The XRO may also path is node/link disjoint from the working path. The XRO may also
include SRLGs to ensure SRLG diversity from the working path. If the include SRLGs to ensure SRLG diversity from the working path. If the
working path ERO includes PKS subobjects, these are also included in working path ERO includes PKS subobjects, these are also included in
the XRO to allow the PCE to ensure diversity. the XRO to allow the PCE to ensure diversity.
skipping to change at line 558 skipping to change at line 574
this way MUST NOT be shared with other PCEs. this way MUST NOT be shared with other PCEs.
4. IANA Considerations 4. IANA Considerations
4.1. PCEP Objects 4.1. PCEP Objects
The "PCEP Parameters" registry contains a subregistry "PCEP Objects". The "PCEP Parameters" registry contains a subregistry "PCEP Objects".
IANA is requested to make the following allocations from this IANA is requested to make the following allocations from this
registry. registry.
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Object Name Object Name Object Name Object Name
Class Type Class Type
17 XRO 1 Route exclusion 17 XRO 1 Route exclusion
4.2. Error Object Field Values. Oki and Farrel Expires March 2008 12
4.2. Explicit Exclusion Route Subobject (EXRS)
The "PCEP Parameters" registry contains a subregistry “IRO
subobjectE IANA is requested to make the following allocation from
this registry for the Explicit Exclusion Route Subobject (EXRS).
Subobject Name
Type 33 EXRS
4.3. Error Object Field Values.
The "PCEP Parameters" registry contains a subregistry "PCEP Errors". The "PCEP Parameters" registry contains a subregistry "PCEP Errors".
IANA is requested to make the following allocations from this IANA is requested to make the following allocations from this
registry. registry.
Values in this section are recommended and to be confirmed by IANA. Values in this section are recommended and to be confirmed by IANA.
Error Meaning and Error-Values Error Meaning and Error-Values
Type Type
11 Unrecognized IRO subobject 11 Unrecognized IRO subobject
Note that this Error-Type has been omitted from [PCEP] where it is Note that this Error-Type has been omitted from [PCEP] where it is
required. It is expected that it will be added to a later version of required. It is expected that it will be added to a later version of
[PCEP] and removed from this document. [PCEP] and removed from this document.
12 Unrecognized EXRS subobject 12 Unrecognized EXRS subobject
5. Manageability considerations 5. Manageability Considerations
A MIB module for management of the PCEP is specified in a separate A MIB module for management of the PCEP is specified in a separate
document. This MIB module allows examination of individual PCEP document. This MIB module allows examination of individual PCEP
messages, in particular requests, responses and errors. messages, in particular requests, responses and errors.
The MIB module MUST be extended to include the ability to view the The MIB module MUST be extended to include the ability to view the
route exclusion extensions defined in this document. route exclusion extensions defined in this document.
Several local policy decisions should be made at the PCE. Firstly,
the exact behavior with regard to desired exclusions must be
available for examination by an operator and may be configurable.
Second, the behavior on receipt of an unrecognized XRO or EXRS
subobject with the X-bit set should be configurable and must be
available for inspection. The inspection and control of these local
policy choices may be part of the PCEP MIB module.
6. Security Considerations 6. Security Considerations
The new exclude route mechanisms defined in this document allow The new exclude route mechanisms defined in this document allow
finer and more specific control of the path computed by a PCE. Such finer and more specific control of the path computed by a PCE. Such
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control increases the risk if a PCEP message is intercepted, control increases the risk if a PCEP message is intercepted,
modified, or spoofed. Therefore, the security techniques described modified, or spoofed. Therefore, the security techniques described
in [PCEP] are considered more important. in [PCEP] are considered more important.
Note, however, that the roue exclusion mechanisms also provide the
operator with the ability to route around vulnerable parts of the
network and may be used to increase overall network security.
7. References 7. References
7.1. Normative Reference 7.1. Normative Reference
[RFC2119] Bradner, S., "Key words for use in RFCs to indicate [RFC2119] Bradner, S., "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997. requirements levels", RFC 2119, March 1997.
[PCEP] JP. Vasseur et al, "Path Computation Element (PCE) [PCEP] JP. Vasseur et al, "Path Computation Element (PCE)
communication Protocol (PCEP) - Version 1 -" draft-ietf-pce-pcep communication Protocol (PCEP) - Version 1 -" draft-ietf-pce-pcep
(work in progress). (work in progress).
[INTER-DOMAIN-REC-ANA] T. Takeda et al., "Analysis of Inter-domain [INTER-DOMAIN-REC-ANA] T. Takeda et al., "Analysis of Inter-domain
Label Switched Path (LSP) Recovery" draft-ietf-ccamp-inter-domain- Label Switched Path (LSP) Recovery" draft-ietf-ccamp-inter-domain-
recovery-analysis (work in progress). recovery-analysis (work in progress).
[PCE-PATH-KEY] R. Bradford, JP Vasseur, and A. Farrel, "Preserving [PCE-PATH-KEY] R. Bradford, JP Vasseur, and A. Farrel, “Preserving
Topology Confidentiality in Inter-Domain Path Computation using a Topology Confidentiality in Inter-Domain Path Computation using a
key based mechanism", draft-ietf-pce-path-key (work in progress). key based mechanismE draft-ietf-pce-path-key (work in progress).
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[BRPC] JP. Vasseur et al, "A Backward Recursive PCE-based [BRPC] JP. Vasseur et al, "A Backward Recursive PCE-based
Computation (BRPC) procedure to compute shortest inter-domain Computation (BRPC) procedure to compute shortest inter-domain
Traffic Engineering Label Switched Paths", draft-ietf-pce-brpc Traffic Engineering Label Switched Paths", draft-ietf-pce-brpc (work
in progress).
[PD-PATH] JP. Vasseur et al, " A Per-domain path computation method
for establishing Inter-domain Traffic Engineering (TE) Label
Switched Paths (LSPs)", draft-ietf-ccamp-inter-domain-pd-path-comp
(work in progress). (work in progress).
7.2. Informative Reference 7.2. Informative Reference
[RFC3477] K. Kompella and Y. Rekhter, "Signalling Unnumbered Links [RFC3477] K. Kompella and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)", in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)",
RFC 3477, January 2003. RFC 3477, January 2003.
[RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau, [RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) "Multiprotocol Label Switching (MPLS) Traffic Engineering (TE)
Management Information Base (MIB)", RFC 3812, June 2004. Management Information Base (MIB)", RFC 3812, June 2004.
[RFC4655] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation [RFC4655] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, September 2006. Element (PCE)-Based Architecture", RFC 4655, September 2006.
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[RFC4657] J. Ash and J.L. Le Roux, "Path Computation Element (PCE) [RFC4657] J. Ash and J.L. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657, September Communication Protocol Generic Requirements", RFC 4657, September
2006. 2006.
[RFC4874] Lee et al, "Exclude Routes - Extension to Resource [RFC4874] Lee et al, "Exclude Routes - Extension to Resource
ReserVation Protocol-Traffic Engineering (RSVP-TE)", RFC 4874, April ReserVation Protocol-Traffic Engineering (RSVP-TE)", RFC 4874, April
2007. 2007.
8. Acknowledgements 8. Acknowledgements
skipping to change at line 682 skipping to change at line 726
Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr. at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
Oki and Farrel Expires March 2008 15
this standard. Please address the information to the IETF at ietf- this standard. Please address the information to the IETF at ietf-
ipr@ietf.org. ipr@ietf.org.
Disclaimer of Validity Disclaimer of Validity
This document and the information contained herein are provided on This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
skipping to change at line 704 skipping to change at line 750
FOR A PARTICULAR PURPOSE. FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
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