draft-ietf-pce-inter-layer-req-05.txt   draft-ietf-pce-inter-layer-req-06.txt 
Network Working Group Eiji Oki (Editor) Network Working Group Eiji Oki (Editor)
Internet Draft NTT Internet Draft NTT
Category: Informational Category: Informational
Expires: January 2008 November 2007
PCC-PCE Communication and PCE Discovery Requirements for Inter-Layer
Traffic Engineering
draft-ietf-pce-inter-layer-req-05.txt PCC-PCE Communication and PCE Discovery Requirements for Inter-
Layer Traffic Engineering
draft-ietf-pce-inter-layer-req-06.txt
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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.
MPLS and GMPLS networks may be constructed from layered MPLS and GMPLS networks may be constructed from layered
client/servicr networks. It is advantageous for overall network client/server networks. It is advantageous for overall network
efficiency to provide end-to-end traffic engineering across multiple efficiency to provide end-to-end traffic engineering across
network layers. PCE is a candidate solution for such requirements. multiple network layers. PCE is a candidate solution for such
requirements.
Generic requirements for a communication protocol between Path Generic requirements for a communication protocol between Path
Computation Clients (PCCs) and PCEs are presented in "PCE Computation Clients (PCCs) and PCEs are presented in “PCE
Communication Protocol Generic Requirements". Generic requirements Communication Protocol Generic Requirements". Generic requirements
for PCE discovery protocol are presented in "Requirements for Path for PCE discovery protocol are presented in “Requirements for Path
Computation Element (PCE) Discovery". Computation Element (PCE) DiscoveryE
This document complements the generic requirements and presents This document complements the generic requirements and presents
detailed sets of PCC-PCE communication protocol requirements and PCE detailed sets of PCC-PCE communication protocol requirements and
discovery protocol requirements for inter-layer traffic engineering. PCE discovery protocol requirements for inter-layer traffic
engineering.
Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction.................................................3
1.1. Terminology.................................................3 1.1. Terminology...............................................4
2. Motivation for PCE-Based Inter-Layer Path Computation..........4 2. Motivation for PCE-Based Inter-Layer Path Computation........4
3. PCC-PCE Communication and Discovery Requirements for Inter-Layer 3. PCC-PCE Communication and Discovery Requirements for Inter-
Traffic Engineering................................................5 Layer Traffic Engineering........................................5
3.1. PCC-PCE Communication.......................................5 3.1. PCC-PCE Communication.....................................5
3.1.1. Control of Inter-Layer Path Computation...................5 3.1.1. Control of Inter-Layer Path Computation.................5
3.1.2. Control of The Type of Path to be Computed................5 3.1.2. Control of The Type of Path to be Computed..............6
3.1.3. Communication of Inter-Layer Constraints..................6 3.1.3. Communication of Inter-Layer Constraints................7
3.1.4. Adaptation Capability.....................................6 3.1.4. Adaptation Capability...................................7
3.1.5. Cooperation Between PCEs..................................6 3.1.5. Cooperation Between PCEs................................7
3.1.6. Inter-Layer Diverse paths.................................7 3.1.6. Inter-Layer Diverse paths...............................7
3.2. Capabilities Advertisements for PCE Discovery...............7 3.2. Capabilities Advertisements for PCE Discovery.............8
3.3. Supported Network Models....................................7 3.3. Supported Network Models..................................8
4. Manageability considerations...................................7 4. Manageability considerations.................................8
4.1. Control of Function and Policy..............................7 4.1. Control of Function and Policy............................8
4.2. Information and Data Models.................................8 4.2. Information and Data Models...............................9
4.3. Liveness Detection and Monitoring...........................8 4.3. Liveness Detection and Monitoring.........................9
4.4. Verifying Correct Operation.................................8 4.4. Verifying Correct Operation...............................9
4.5. Requirements on Other Protocols and Functional Components...9 4.5. Requirements on Other Protocols and Functional Components 10
4.6. Impact on Network Operation.................................9 4.6. Impact on Network Operation..............................10
5. Security Considerations........................................9 5. Security Considerations.....................................10
6. Acknowledgments................................................9 6. Acknowledgments.............................................11
7. References....................................................10 7. References..................................................11
7.1. Normative Reference........................................10 7.1. Normative Reference......................................11
7.2. Informative Reference......................................10 7.2. Informative Reference....................................11
8. Authors' Addresses............................................11 8. AuthorsEAddresses..........................................12
9. Intellectual Property Statement...............................11 9. Intellectual Property Statement.............................12
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
that is capable of computing a network path or route based on a entity that is capable of computing a network path or route based
network graph, and applying computational constraints. on a network graph, and applying computational constraints.
A network may comprise of multiple layers. These layers may A network may comprise multiple layers. These layers may represent
represent separations of technologies (e.g., packet switch capable separations of technologies (e.g., packet switch capable (PSC),
(PSC), time division multiplex (TDM), lambda switch capable (LSC)) time division multiplex (TDM), lambda switch capable (LSC))
[RFC3945], separation of data plane switching granularity levels [RFC3945], separation of data plane switching granularity levels
(e.g., PSC-1 and PSC-2, or VC4 and VC12) [MRN-REQ], or a (e.g., PSC-1 and PSC-2, or VC4 and VC12) [MLN-REQ], or a
distinction between client and server networking roles (e.g., distinction between client and server networking roles (e.g.,
commercial or administrative separation of client and server commercial or administrative separation of client and server
networks). In this multi-layer network, LSP in lower layers are used networks). In this multi-layer network, LSP in lower layers are
to carry upper-layer LSPs. The network topology formed by lower- used to carry upper-layer LSPs. The network topology formed by
layer LSPs and advertised to the higher layer is called a Virtual lower-layer LSPs and advertised to the higher layer is called a
Network Topology (VNT) [MRN-REQ]. Virtual Network Topology (VNT) [MLN-REQ].
It is important to optimize network resource utilization globally, It is important to optimize network resource utilization globally,
i.e. taking into account all layers, rather than optimizing resource i.e. taking into account all layers, rather than optimizing
utilization at each layer independently. This allows achieving resource utilization at each layer independently. This allows
better network efficiency. This is what we call Inter-layer traffic achieving better network efficiency. This is what we call Inter-
engineering. This includes mechanisms allowing to compute end-to-end layer traffic engineering. This includes mechanisms allowing to
paths across layers, as known as inter-layer path computation, and compute end-to-end paths across layers, as known as inter-layer
mechanisms for control and management of the VNT by setting up and path computation, and mechanisms for control and management of the
releasing LSPs in the lower layers [MRN-REQ]. VNT by setting up and releasing LSPs in the lower layers [MLN-REQ].
Inter-layer traffic engineering is included in the scope of the PCE Inter-layer traffic engineering is included in the scope of the
architecture [RFC4655], and PCE can provide a suitable mechanism for PCE architecture [RFC4655], and PCE can provide a suitable
resolving inter-layer path computation issues. The applicability of mechanism for resolving inter-layer path computation issues. The
the PCE-based path computation architecture to inter-layer traffic applicability of the PCE-based path computation architecture to
engineering is described in [PCE-INTER-LAYER-FRWK]. inter-layer traffic engineering is described in [PCE-INTER-LAYER-
FRWK].
This document presents sets of PCC-PCE communication protocol This document presents sets of PCC-PCE communication protocol
(PCECP) and PCE Discovery protocol requirements for inter-layer (PCECP) and PCE Discovery protocol requirements for inter-layer
traffic engineering. It supplements the generic requirements traffic engineering. It supplements the generic requirements
documented in [RFC4657] and [RFC4674]. documented in [RFC4657] and [RFC4674].
1.1. Terminology 1.1. Terminology
LSP: Label Switched Path. LSP: Label Switched Path.
LSR: Label Switching Router. LSR: Label Switching Router.
PCC: Path Computation Client: any client application requesting a PCC: Path Computation Client: any client application requesting a
path computation to be performed by a Path Computation Element. path computation to be performed by a Path Computation Element.
PCE: Path Computation Element: an entity (component, application or PCE: Path Computation Element: an entity (component, application
network node) that is capable of computing a network path or route or network node) that is capable of computing a network path or
based on a network graph and applying computational constraints. route based on a network graph and applying computational
constraints.
PCECP: PCE Communication Protocol, a protocol for communication PCECP: PCE Communication Protocol, a protocol for communication
between PCCs and PCEs. between PCCs and PCEs.
TED: Traffic Engineering Database which contains the topology and TED: Traffic Engineering Database which contains the topology and
resource information of the domain. The TED may be fed by IGP resource information of the domain. The TED may be fed by IGP
extensions or potentially by other means. extensions or potentially by other means.
TE LSP: Traffic Engineering Label Switched Path. TE LSP: Traffic Engineering Label Switched Path.
TE LSP head-end: head/source/ingress of the TE LSP. TE LSP head-end: head/source/ingress of the TE LSP.
TE LSP tail-end: tail/destination/egress of the TE LSP. TE LSP tail-end: tail/destination/egress of the TE LSP.
Although this requirements document is an informational document not Although this requirements document is an informational document
a protocol specification, the key words "MUST", "MUST NOT", not a protocol specification, the key words "MUST", "MUST NOT",
"REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC 2119 [RFC2119] for clarity of interpreted as described in RFC 2119 [RFC2119] for clarity of
requirement specification. requirement specification.
2. Motivation for PCE-Based Inter-Layer Path Computation 2. Motivation for PCE-Based Inter-Layer Path Computation
[RFC4206] defines a way to signal a Multiprotocol Label Switching [RFC4206] defines a way to signal a Multiprotocol Label Switching
(MPLS) or Generalized MPLS (GMPLS) LSP with an explicit route in a (MPLS) or Generalized MPLS (GMPLS) LSP with an explicit route in a
higher layer of a network that includes hops traversed by LSPs in higher layer of a network that includes hops traversed by LSPs in
lower layers of the network. The computation of end-to-end paths lower layers of the network. The computation of end-to-end paths
across layers is called Inter-Layer Path Computation. across layers is called Inter-Layer Path Computation.
An LSR in the higher-layer might not have information on the An LSR in the higher-layer might not have information on the
topology of lower-layers, particularly in an overlay or augmented topology of lower-layers, particularly in an overlay or augmented
model, and hence might not be able to compute an end-to-end path model, and hence might not be able to compute an end-to-end path
across layers. across layers.
PCE-based inter-layer path computation, consists of relying on one PCE-based inter-layer path computation, consists of relying on one
or more PCEs to compute an end-to-end path across layers. This could or more PCEs to compute an end-to-end path across layers. This
rely on a single PCE path computation where the PCE has topology could rely on a single PCE path computation where the PCE has
information about multiple layers and can directly compute an end- topology information about multiple layers and can directly
to-end path across layers considering the topology of all of the compute an end-to-end path across layers considering the topology
layers. Alternatively, the inter-layer path computation could be of all of the layers. Alternatively, the inter-layer path
performed as a multiple PCE computation where each member of a set computation could be performed as a multiple PCE computation where
of PCEs has information about the topology of one or more layers, each member of a set of PCEs has information about the topology of
but not all layers, and collaborate to compute an end-to-end path. one or more layers, but not all layers, and collaborate to compute
an end-to-end path.
Consider a two-layer network where the higher-layer network is a Consider a two-layer network where the higher-layer network is a
packet-based IP/MPLS or GMPLS network and the lower-layer network is packet-based IP/MPLS or GMPLS network and the lower-layer network
a GMPLS optical network. An ingress LSR in the higher-layer network is a GMPLS optical network. An ingress LSR in the higher-layer
tries to set up an LSP to an egress LSR also in the higher-layer network tries to set up an LSP to an egress LSR also in the
network across the lower-layer network, and needs a path in the higher-layer network across the lower-layer network, and needs a
higher-layer network. However, suppose that there is no TE link path in the higher-layer network. However, suppose that there is
between border LSRs, which are located on the boundary between the no TE link between border LSRs, which are located on the boundary
higher-layer and lower-layer networks, and that the ingress LSR does between the higher-layer and lower-layer networks, and that the
not have topology visibility in the lower layer. If a single-layer ingress LSR does not have topology visibility in the lower layer.
path computation is applied for the higher-layer, the path If a single-layer path computation is applied for the higher-layer,
computation fails. On the other hand, inter-layer path computation the path computation fails. On the other hand, inter-layer path
is able to provide a route in the higher-layer and a suggestion that computation is able to provide a route in the higher-layer and a
a lower-layer LSP be setup between border LSRs, considering both suggestion that a lower-layer LSP be setup between border LSRs,
layers' TE topologies. considering both layersETE topologies.
Further discussion of the application of PCE to inter-layer path Further discussion of the application of PCE to inter-layer path
computation can be found in [PCE-INTER-LAYER-FRWK]. computation can be found in [PCE-INTER-LAYER-FRWK].
3. PCC-PCE Communication and Discovery Requirements for Inter-Layer 3. PCC-PCE Communication and Discovery Requirements for Inter-Layer
Traffic Engineering Traffic Engineering
This section sets out additional requirements specific to the This section sets out additional requirements specific to the
problems of multi-layer TE that are not covered in [RFC4657] or problems of multi-layer TE that are not covered in [RFC4657] or
[RFC4674]. [RFC4674].
skipping to change at page 5, line 27 skipping to change at page 6, line 4
This requires no additional messages, but implies the following This requires no additional messages, but implies the following
additional constraints to be added to the PCC-PCE communication additional constraints to be added to the PCC-PCE communication
protocol. protocol.
3.1.1. 3.1.1.
Control of Inter-Layer Path Computation Control of Inter-Layer Path Computation
A request from a PCC to a PCE SHOULD indicate whether inter-layer A request from a PCC to a PCE SHOULD indicate whether inter-layer
path computation is allowed. In the absence of such an indication, path computation is allowed. In the absence of such an indication,
the default is that inter-layer path computation is not allowed. the default is that inter-layer path computation is not allowed.
Therefore, a request from a PCC to a PCE MUST support the inclusion
of such an indication. Therefore, a request from a PCC to a PCE MUST support the
inclusion of such an indication.
3.1.2. 3.1.2.
Control of The Type of Path to be Computed Control of The Type of Path to be Computed
The PCE computes and returns a path to the PCC that the PCC can use The PCE computes and returns a path to the PCC that the PCC can
to build a higher-layer or lower-layer LSP once converted to an use to build a higher-layer or lower-layer LSP once converted to
Explicit Route Object (ERO) for use in RSVP-TE signaling. There are an Explicit Route Object (ERO) for use in RSVP-TE signaling. There
two options [PCE-INTER-LAYER-FRWK]. are two options [PCE-INTER-LAYER-FRWK].
- Option 1: Mono-layer path. The PCE computes a "mono layer" path, - Option 1: Mono-layer path. The PCE computes a "mono layer" path,
i.e. a path that includes only TE-links from the same layer. i.e. a path that includes only TE-links from the same layer.
- Option 2: Multi-layer path. The PCE computes a "multi-layer" path, - Option 2: Multi-layer path. The PCE computes a "multi-layer"
i.e. a path that includes TE links from distinct layers [RFC4206]. path, i.e. a path that includes TE links from distinct layers
[RFC4206].
A request from a PCC to a PCE MUST allow control of the type of the It may be necessary or desirable for a PCC to control the type of
path to be computed by selection from the following list: path that is produced by a PCE. For example, a PCC may know that
- A mono-layer path that is specified by strict hop(s). The path may it is not possible for technological or policy reasons to signal a
include virtual TE link(s). multi-layer path and that a mono-layer path is required, or the
PCC may know that it does not wish the layer border node to have
control of path computation. In order to make this level of
control possible, the PCECP MUST allow the PCC to select the path
types that may be returned by choosing one or more from the
following list:
- A mono-layer path that is specified by strict hop(s). The path
may include virtual TE link(s).
- A mono-layer path that includes loose hop(s). - A mono-layer path that includes loose hop(s).
- A multi-layer path that can include the complete path of one or - A multi-layer path that can include the path (as strict or loose
more lower-layer LSPs not yet established. hops) of one or more lower-layer LSPs not yet established.
When multi-layer path computation is requested, a response from a The path computation response from a PCE to a PCC MUST report the
PCE to a PCC MUST support the inclusion, as part of end-to-end path, type of path computed, and where a multi-layer path is returned,
of the path of the lower-layer LSPs to be established. PCECP MUST support the inclusion, as part of end-to-end path, of
the path of the lower-layer LSPs to be established.
If a response message from a PCE to PCC carries a mono-layer path If a response message from a PCE to PCC carries a mono-layer path
that is specified by strict hops but includes virtual TE link(s), or that is specified by strict hops but includes virtual TE link(s),
includes loose hop(s), or carries a multi-layer path that can or includes loose hop(s), or carries a multi-layer path that can
include the complete path of one or more lower-layer LSPs not yet include the complete path of one or more lower-layer LSPs not yet
established, the signaling of the higher-layer LSP may trigger the established, the signaling of the higher-layer LSP may trigger the
establishment of the lower-layer LSPs (nested signaling). The nested establishment of the lower-layer LSPs (nested signaling). The
signaling may increase the higher-layer connection setup latency. An nested signaling may increase the higher-layer connection setup
ingress LSR for the higher-layer LSP, or a PCC, needs to know latency. An ingress LSR for the higher-layer LSP, or a PCC, needs
whether nested signaling is required or not. to know whether nested signaling is required or not.
A request from a PCC to a PCE MUST allow indicating whether nested A request from a PCC to a PCE MUST allow indicating whether nested
signaling is acceptable or not. signaling is acceptable or not.
A response from a PCE to a PCC MUST allow indicating whether the A response from a PCE to a PCC MUST allow indicating whether the
computed path triggers nested signaling or not. computed path triggers nested signaling or not.
3.1.3. 3.1.3.
Communication of Inter-Layer Constraints Communication of Inter-Layer Constraints
A request from a PCC to a PCE MUST support the inclusion of A request from a PCC to a PCE MUST support the inclusion of
constraints for a multi-layer path. This includes control over which constraints for a multi-layer path. This includes control over
network layers may, must, or must not be included in the computed which network layers may, must, or must not be included in the
path. Such control may be expressed in terms of the switching types computed path. Such control may be expressed in terms of the
of the layer networks. switching types of the layer networks.
The path computation request MUST also allow for different objective The path computation request MUST also allow for different
functions to be applied within different network layers. For example, objective functions to be applied within different network layers.
the path in a packet-network may need to be optimized for least For example, the path in a packet-network may need to be optimized
delay using the IGP metric as a measure of delay, while the path in for least delay using the IGP metric as a measure of delay, while
an under-lying TDM network might be optimized for fewest hops. the path in an under-lying TDM network might be optimized for
fewest hops.
3.1.4. 3.1.4.
Adaptation Capability Adaptation Capability
It MUST be possible for the path computation request to indicate the It MUST be possible for the path computation request to indicate
desired adaptation function at the end points of the lower-layer LSP the desired adaptation function at the end points of the lower-
that is being computed. This will be particularly important where layer LSP that is being computed. This will be particularly
the ingress and egress LSR participate in more than one layer important where the ingress and egress LSR participate in more
network but may not be capable of all associated adaptations. than one layer network but may not be capable of all associated
adaptations.
3.1.5. 3.1.5.
Cooperation Between PCEs Cooperation Between PCEs
When each layer is controlled by a PCE, which only has access to the When each layer is controlled by a PCE, which only has access to
topology information of its layer, the PCEs of each layer need to the topology information of its layer, the PCEs of each layer need
cooperate to perform inter-layer path computation. In this case, to cooperate to perform inter-layer path computation. In this case,
communication between PCEs is required for inter-layer path communication between PCEs is required for inter-layer path
computation. A PCE that behaves as a client is defined as a PCC computation. A PCE that behaves as a client is defined as a PCC
[RFC4655]. [RFC4655].
The PCC-PCE communication protocol MUST allow requests and replies The PCC-PCE communication protocol MUST allow requests and replies
for multiple PCE inter-layer path computation. for multiple PCE inter-layer path computation.
3.1.6. 3.1.6.
Inter-Layer Diverse paths Inter-Layer Diverse paths
The PCE communication protocol MUST allow for the computation of The PCE communication protocol MUST allow for the computation of
diverse inter-Layer paths. A request from a PCC to a PCE MUST diverse inter-Layer paths. A request from a PCC to a PCE MUST
support the inclusion of multiple path requests, with the desired support the inclusion of multiple path requests, with the desired
level of diversity at each layer (link, node, SRLG). level of diversity at each layer (link, node, SRLG).
3.2. Capabilities Advertisements for PCE Discovery 3.2. Capabilities Advertisements for PCE Discovery
In the case where there are several PCEs with distinct capabilities In the case where there are several PCEs with distinct
available, a PCC has to select one or more appropriate PCEs. capabilities available, a PCC has to select one or more
appropriate PCEs.
For that purpose, the PCE discovery mechanism MAY support the For that purpose, the PCE discovery mechanism MAY support the
disclosure of some detailed PCE capabilities. disclosure of some detailed PCE capabilities.
A PCE MAY (to be consistent with the above text and RFC4674) be able A PCE MAY (to be consistent with the above text and RFC4674) be
to advise the following inter-layer-path-computation-related PCE able to advise the following inter-layer-path-computation-related
capabilities: PCE capabilities:
- Support for inter-layer path computation - Support for inter-layer path computation
- Support for mono-layer/multi-layer paths - Support for mono-layer/multi-layer paths
- Support for Adaptation Capability - Support for Adaptation Capability
- Support for Inter-PCE communication - Support for Inter-PCE communication
- Support for inter-layer diverse path computation - Support for inter-layer diverse path computation
3.3. Supported Network Models 3.3. Supported Network Models
The PCC-PCE communication protocol SHOULD allow several The PCC-PCE communication protocol SHOULD allow several
architectural alternatives for interworking between MPLS and GMPLS architectural alternatives for interworking between MPLS and GMPLS
networks: overlay, integrated and augmented models networks: overlay, integrated and augmented models
[RFC3945][INTWORK-FRWK][INTWORK-REQ]. [RFC3945][INTWORK-FRWK][INTWORK-REQ].
4. Manageability considerations 4. Manageability considerations
4.1. Control of Function and Policy 4.1. Control of Function and Policy
An individual PCE MAY elect to support inter-layer computations and An individual PCE MAY elect to support inter-layer computations
advertise its capabilities as described in the previous sections. and advertise its capabilities as described in the previous
PCE implementations MAY provide a configuration switch to allow sections. PCE implementations MAY provide a configuration switch
support of inter-layer path computations to be enabled or disabled. to allow support of inter-layer path computations to be enabled or
When the level of support is changed, this SHOULD be re-advertised. disabled. When the level of support is changed, this SHOULD be re-
advertised.
However, a PCE MAY also elect to support inter-layer computations, However, a PCE MAY also elect to support inter-layer computations,
but not to advertise the fact, so that only those PCCs configured to but not to advertise the fact, so that only those PCCs configured
know of the PCE and its capabilities can use it. to know of the PCE and its capabilities can use it.
Support for, and advertisement of support for, inter-layer path Support for, and advertisement of support for, inter-layer path
computation MAY be subject to policy and a PCE MAY hide its inter- computation MAY be subject to policy and a PCE MAY hide its inter-
layer capabilities from certain PCCs by not advertising them through layer capabilities from certain PCCs by not advertising them
the discovery protocol, and not reporting them to the specific PCCs through the discovery protocol, and not reporting them to the
in any PCECP capabilities exchange. Further, a PCE MAY be directed specific PCCs in any PCECP capabilities exchange. Further, a PCE
by policy to refuse an inter-layer path computation request for any MAY be directed by policy to refuse an inter-layer path
reason including, but not limited to, the identity of the PCC that computation request for any reason including, but not limited to,
makes the request. the identity of the PCC that makes the request.
4.2. Information and Data Models 4.2. Information and Data Models
PCECP protocol extensions to support inter-layer computations MUST PCECP protocol extensions to support inter-layer computations MUST
be accompanied by MIB objects for the control and monitoring of the be accompanied by MIB objects for the control and monitoring of
protocol and of the PCE that performs the computations. The MIB the protocol and of the PCE that performs the computations. The
objects MAY be provided in the same MIB module as used for general MIB objects MAY be provided in the same MIB module as used for
PCECP control and monitoring [PCEP-MIB] or MAY be provided in a new general PCECP control and monitoring [PCEP-MIB] or MAY be
MIB module. provided in a new MIB module.
The MIB objects MUST provide the ability to control and monitor all The MIB objects MUST provide the ability to control and monitor
aspects of PCECP relevant to inter-layer path computation. all aspects of PCECP relevant to inter-layer path computation.
4.3. Liveness Detection and Monitoring 4.3. Liveness Detection and Monitoring
No changes are necessary to the liveness detection and monitoring No changes are necessary to the liveness detection and monitoring
requirements as already embodied in [RFC4657]. It should be noted, requirements as already embodied in [RFC4657]. It should be noted,
however, that inter-layer path computations might require extended however, that inter-layer path computations might require extended
cooperation between PCEs (as is also the case for inter-AS and cooperation between PCEs (as is also the case for inter-AS and
inter-area computations) and so the liveness detection and inter-area computations) and so the liveness detection and
monitoring SHOULD be applied to each PCECP communication and monitoring SHOULD be applied to each PCECP communication and
aggregated to report the behavior of an individual PCECP request to aggregated to report the behavior of an individual PCECP request
the originating PCC. to the originating PCC.
In particular, where a request is forwarded between multiple PCEs In particular, where a request is forwarded between multiple PCEs
neither the PCC not the first PCE can monitor the liveness of all neither the PCC not the first PCE can monitor the liveness of all
inter-PCE-PCE connections or of the PCEs themselves. In this case, inter-PCE-PCE connections or of the PCEs themselves. In this case,
suitable performance of the original PCECP request relies on each suitable performance of the original PCECP request relies on each
PCE operating correct monitoring procedures and correlating any PCE operating correct monitoring procedures and correlating any
failures back to the PCECP requests that are outstanding. These failures back to the PCECP requests that are outstanding. These
requirements are no different from those for any cooperative PCE requirements are no different from those for any cooperative PCE
usage, and are expected to be already covered by general, and by usage, and are expected to be already covered by general, and by
inter-AS and inter-area implementations. inter-AS and inter-area implementations.
4.4. Verifying Correct Operation 4.4. Verifying Correct Operation
There are no additional requirements beyond those expressed in There are no additional requirements beyond those expressed in
[RFC4657] for verifying the correct operation of the PCECP. Note [RFC4657] for verifying the correct operation of the PCECP. Note
that verification of the correct operation of the PCE and its that verification of the correct operation of the PCE and its
algorithms is out of scope for the protocol requirements, but a PCC algorithms is out of scope for the protocol requirements, but a
MAY send the same request to more than one PCE and compare the PCC MAY send the same request to more than one PCE and compare the
results. results.
4.5. Requirements on Other Protocols and Functional Components 4.5. Requirements on Other Protocols and Functional Components
A PCE operates on a topology graph that may be built using A PCE operates on a topology graph that may be built using
information distributed by TE extensions to the routing protocol information distributed by TE extensions to the routing protocol
operating within the network. In order that the PCE can select a operating within the network. In order that the PCE can select a
suitable path for the signaling protocol to use to install the suitable path for the signaling protocol to use to install the
inter-layer LSP, the topology graph must include information about inter-layer LSP, the topology graph must include information about
the inter-layer signaling and forwarding (i.e. adaptation) the inter-layer signaling and forwarding (i.e. adaptation)
capabilities of each LSR in the network. capabilities of each LSR in the network.
Whatever means is used to collect the information to build the Whatever means is used to collect the information to build the
topology graph MUST include the requisite information. If the TE topology graph MUST include the requisite information. If the TE
extensions to the routing protocol are used, these SHOULD satisfy extensions to the routing protocol are used, these SHOULD satisfy
the requirements as described in [MRN-REQ]. the requirements as described in [MLN-REQ].
4.6. Impact on Network Operation 4.6. Impact on Network Operation
The use of a PCE to compute inter-layer paths is not expected to The use of a PCE to compute inter-layer paths is not expected to
have significant impact on network operations. But it should be have significant impact on network operations. But it should be
noted that the introduction of inter-layer support to a PCE that noted that the introduction of inter-layer support to a PCE that
already provides mono-layer path computation might change the already provides mono-layer path computation might change the
loading of the PCE and that might have an impact on the network loading of the PCE and that might have an impact on the network
behavior especially during recovery periods immediately after a behavior especially during recovery periods immediately after a
network failure. network failure.
On the other hand, it is envisioned that the use of inter-layer path On the other hand, it is envisioned that the use of inter-layer
computation will have significant benefits to the operation of a path computation will have significant benefits to the operation
multi-layer network including improving the network resource usage of a multi-layer network including improving the network resource
and enabling a greater number of higher-layer LSPs to be supported. usage and enabling a greater number of higher-layer LSPs to be
supported.
5. Security Considerations 5. Security Considerations
Inter-layer traffic engineering with PCE may raise new security Inter-layer traffic engineering with PCE may raise new security
issues when PCE-PCE communication is done between different layer issues when PCE-PCE communication is done between different layer
networks for inter-layer path computation. Security issues may also networks for inter-layer path computation. Security issues may
exist when a single PCE is granted full visibility of TE information also exist when a single PCE is granted full visibility of TE
that applies to multiple layers. information that applies to multiple layers.
The formal introduction of a VNT Manager component as described in The formal introduction of a VNT Manager component as described in
[PCE-INTER-LAYER-FRWK] provides the basis for the application of [PCE-INTER-LAYER-FRWK] provides the basis for the application of
inter-layer security and policy. inter-layer security and policy.
It is expected that solutions for inter-layer protocol extensions It is expected that solutions for inter-layer protocol extensions
will address these issues in detail. will address these issues in detail.
6. Acknowledgments 6. Acknowledgments
We would like to thank Kohei Shiomoto, Ichiro Inoue, and Dean Cheng We would like to thank Kohei Shiomoto, Ichiro Inoue, and Dean
for their useful comments. Cheng for their useful comments.
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.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
Architecture", RFC 3945, October 2004. Architecture", RFC 3945, October 2004.
[RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths (LSP) [RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths
Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) (LSP) Hierarchy with Generalized Multi-Protocol Label Switching
Traffic Engineering (TE)", RFC 4206, October 2005. (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
7.2. Informative Reference 7.2. Informative Reference
[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.
[RFC4657] J. Ash, J.L Le Roux et al., " Path Computation Element [RFC4657] J. Ash, J.L Le Roux et al., " Path Computation Element
(PCE) Communication Protocol Generic Requirements", RFC 4657, (PCE) Communication Protocol Generic Requirements", RFC 4657,
September 2006. September 2006.
[RFC4674] JL Le Roux et al., "Requirements for Path Computation [RFC4674] JL Le Roux et al., "Requirements for Path Computation
Element (PCE) Discovery", RFC 4674, September 2006. Element (PCE) Discovery", RFC 4674, September 2006.
[MRN-REQ] K. Shiomoto et al., "Requirements for GMPLS-based multi- [MLN-REQ] K. Shiomoto et al., "Requirements for GMPLS-based multi-
region and multi-layer networks (MRN/MLN)", draft-ietf-ccamp-gmpls- region and multi-layer networks (MRN/MLN)", draft-ietf-ccamp-
mln-reqs (work in progress). gmpls-mln-reqs (work in progress).
[PCE-INTER-LAYER-FRWK] E. Oki et al., "Framework for PCE-Based [PCE-INTER-LAYER-FRWK] E. Oki et al., "Framework for PCE-Based
Inter-Layer MPLS and GMPLS Traffic Engineering", draft-oki-pce- Inter-Layer MPLS and GMPLS Traffic Engineering", draft-ietf-pce-
inter-layer-frwk (work in progress). inter-layer-frwk (work in progress).
[PCEP-MIB] Koushik, A., and Stephan, E., "PCE communication [PCEP-MIB] A. Koushik, and E. Stephan, "PCE communication
protocol(PCEP) Management Information Base", draft-kkoushik-pce- protocol(PCEP) Management Information Base", draft-kkoushik-pce-
pcep-mib (work in progress). pcep-mib (work in progress).
[INTWORK-FRWK] K. Shiomoto et al. "Framework for MPLS-TE to GMPLS [INTWORK-FRWK] K. Shiomoto, “Framework for MPLS-TE to GMPLS
migration", draft-ietf-ccamp-mpls-gmpls-interwork-fmwk-02.txt (work migration,Edraft-ietf-ccamp-mpls-gmpls-interwork-fmwk (work in
in progress). progress).
[INTWORK-REQ] Kenji Kumaki et al., "Interworking Requirements to [INTWORK-REQ] K. Kumaki et al., “Interworking Requirements to
Support operation of MPLS-TE over GMPLS Networks", draft-ietf-ccamp- Support operation of MPLS-TE over GMPLS Networks,Edraft-ietf-
mpls-gmpls-interwork-reqts-01.txt (work in progress). ccamp-mpls-gmpls-interwork-reqts (work in progress).
8. Authors' Addresses 8. AuthorsEAddresses
Eiji Oki Eiji Oki
NTT NTT
3-9-11 Midori-cho, 3-9-11 Midori-cho,
Musashino-shi, Tokyo 180-8585, Japan Musashino-shi, Tokyo 180-8585, Japan
Email: oki.eiji@lab.ntt.co.jp Email: oki.eiji@lab.ntt.co.jp
Jean-Louis Le Roux Jean-Louis Le Roux
France Telecom R&D, France Telecom R&D,
Av Pierre Marzin, Av Pierre Marzin,
skipping to change at page 11, line 35 skipping to change at page 12, line 39
Email: ke-kumaki@kddi.com Email: ke-kumaki@kddi.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
Email: adrian@olddog.co.uk Email: adrian@olddog.co.uk
9. Intellectual Property Statement 9. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described to pertain to the implementation or use of the technology
in this document or the extent to which any license under such described in this document or the extent to which any license
rights might or might not be available; nor does it represent that under such rights might or might not be available; nor does it
it has made any independent effort to identify any such rights. represent that it has made any independent effort to identify any
Information on the procedures with respect to rights in RFC such rights. Information on the procedures with respect to rights
documents can be found in BCP 78 and BCP 79. in RFC documents can be found in BCP 78 and BCP 79.
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
copyrights, patents or patent applications, or other proprietary any copyrights, patents or patent applications, or other
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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
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Copyright Statement Copyright Statement
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