draft-ietf-pce-inter-layer-req-06.txt   draft-ietf-pce-inter-layer-req-07.txt 
Network Working Group Eiji Oki (Editor) Network Working Group Eiji Oki (Editor)
Internet Draft NTT Internet Draft NTT
Category: Informational Category: Informational
November 2007 Expires: October 9th, 2008 April 9th, 2008
PCC-PCE Communication and PCE Discovery Requirements for Inter- PCC-PCE Communication and PCE Discovery Requirements for
Layer Traffic Engineering Inter-Layer Traffic Engineering
draft-ietf-pce-inter-layer-req-06.txt draft-ietf-pce-inter-layer-req-07.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
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. 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/server
client/server networks. It is advantageous for overall network networks. It is advantageous for overall network efficiency to
efficiency to provide end-to-end traffic engineering across provide end-to-end traffic engineering across multiple network
multiple network layers. PCE is a candidate solution for such layers. PCE is a candidate solution for such requirements.
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E Computation Element (PCE) Discovery".
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 detailed sets of PCC-PCE communication protocol requirements and PCE
PCE discovery protocol requirements for inter-layer traffic discovery protocol requirements for inter-layer traffic engineering.
engineering.
Table of Contents Table of Contents
1. Introduction.................................................3 1. Introduction.................................................3
1.1. Terminology...............................................4 1.1. Terminology............................................... 3
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- 3. PCC-PCE Communication and Discovery Requirements for Inter-
Layer 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..............6 3.1.2. Control of The Type of Path to be Computed.............. 5
3.1.3. Communication of Inter-Layer Constraints................7 3.1.3. Communication of Inter-Layer Constraints................7
3.1.4. Adaptation Capability...................................7 3.1.4. Adaptation Capability...................................7
3.1.5. Cooperation Between PCEs................................7 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.............8 3.2. Capabilities Advertisements for PCE Discovery.............8
3.3. Supported Network Models..................................8 3.3. Supported Network Models..................................8
4. Manageability considerations.................................8 4. Manageability considerations.................................8
4.1. Control of Function and Policy............................8 4.1. Control of Function and Policy............................8
4.2. Information and Data Models...............................9 4.2. Information and Data Models...............................9
4.3. Liveness Detection and Monitoring.........................9 4.3. Liveness Detection and Monitoring.........................9
4.4. Verifying Correct Operation...............................9 4.4. Verifying Correct Operation...............................9
4.5. Requirements on Other Protocols and Functional Components 10 4.5. Requirements on Other Protocols and Functional
Components................................................ 9
4.6. Impact on Network Operation..............................10 4.6. Impact on Network Operation..............................10
5. Security Considerations.....................................10 5. Security Considerations.....................................10
6. Acknowledgments.............................................11 6. IANA Considerations......................................... 10
7. References..................................................11 7. Acknowledgments............................................. 10
7.1. Normative Reference......................................11 8. References.................................................. 11
7.2. Informative Reference....................................11 8.1. Normative Reference...................................... 11
8. AuthorsEAddresses..........................................12 8.2. Informative Reference.................................... 11
9. Intellectual Property Statement.............................12 9. Authors' Addresses.......................................... 12
10. Intellectual Property Statement............................ 12
1. Introduction 1. Introduction
The Path Computation Element (PCE) defined in [RFC4655] is an The Path Computation Element (PCE) defined in [RFC4655] is an entity
entity that is capable of computing a network path or route based that is capable of computing a network path or route based on a
on a network graph, and applying computational constraints. network graph, and applying computational constraints.
A network may comprise multiple layers. These layers may represent A network may comprise multiple layers. These layers may represent
separations of technologies (e.g., packet switch capable (PSC), separations of technologies (e.g., packet switch capable (PSC), time
time division multiplex (TDM), lambda switch capable (LSC)) division multiplex (TDM), lambda switch capable (LSC)) [RFC3945],
[RFC3945], separation of data plane switching granularity levels separation of data plane switching granularity levels (e.g., PSC-1
(e.g., PSC-1 and PSC-2, or VC4 and VC12) [MLN-REQ], or a and PSC-2, or VC4 and VC12) [MLN-REQ], or a distinction between
distinction between client and server networking roles (e.g., client and server networking roles (e.g., commercial or
commercial or administrative separation of client and server administrative separation of client and server networks). In this
networks). In this multi-layer network, LSP in lower layers are multi-layer network, LSP in lower layers are used to carry upper-
used to carry upper-layer LSPs. The network topology formed by layer LSPs. The network topology formed by lower-layer LSPs and
lower-layer LSPs and advertised to the higher layer is called a advertised to the higher layer is called a Virtual Network Topology
Virtual Network Topology (VNT) [MLN-REQ]. (VNT) [MLN-REQ].
It is important to optimize network resource utilization globally, In layered networks under the operation of MPLS-TE and GMPLS
i.e. taking into account all layers, rather than optimizing protocols, it is important to provide mechanisms to allow global
resource utilization at each layer independently. This allows optimization of network resources. That is, to take into account all
achieving better network efficiency. This is what we call Inter- layers, rather than optimizing resource utilization at each layer
layer traffic engineering. This includes mechanisms allowing to independently. This allows better network efficiency to be achieved.
compute end-to-end paths across layers, as known as inter-layer This is what we call Inter-layer traffic engineering. This includes
path computation, and mechanisms for control and management of the mechanisms allowing computation of end-to-end paths across layers
VNT by setting up and releasing LSPs in the lower layers [MLN-REQ]. (known as inter-layer path computation), and mechanisms for control
and management of the VNT by setting up and releasing LSPs in the
lower layers [MLN-REQ].
Inter-layer traffic engineering is included in the scope of the Inter-layer traffic engineering is included in the scope of the PCE
PCE architecture [RFC4655], and PCE can provide a suitable architecture [RFC4655], and PCE can provide a suitable mechanism for
mechanism for resolving inter-layer path computation issues. The resolving inter-layer path computation issues. The applicability of
applicability of the PCE-based path computation architecture to the PCE-based path computation architecture to inter-layer traffic
inter-layer traffic engineering is described in [PCE-INTER-LAYER- engineering is described in [PCE-INTER-LAYER-FRWK].
FRWK].
This document presents sets of PCC-PCE communication protocol This document presents sets of PCC-PCE communication protocol (PCECP)
(PCECP) and PCE Discovery protocol requirements for inter-layer and PCE Discovery protocol requirements for inter-layer traffic
traffic engineering. It supplements the generic requirements engineering. It supplements the generic requirements documented in
documented in [RFC4657] and [RFC4674]. [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 PCE: Path Computation Element: an entity (component, application or
or network node) that is capable of computing a network path or network node) that is capable of computing a network path or route
route based on a network graph and applying computational based on a network graph and applying computational constraints.
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 Although this requirements document is an informational document not
not a protocol specification, the key words "MUST", "MUST 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
topology of lower-layers, particularly in an overlay or augmented of lower-layers, particularly in an overlay or augmented model, and
model, and hence might not be able to compute an end-to-end path 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
or more PCEs to compute an end-to-end path across layers. This more PCEs to compute an end-to-end path across layers. This could
could rely on a single PCE path computation where the PCE has rely on a single PCE path computation where the PCE has topology
topology information about multiple layers and can directly information about multiple layers and can directly compute an end-to-
compute an end-to-end path across layers considering the topology end path across layers considering the topology of all of the layers.
of all of the layers. Alternatively, the inter-layer path Alternatively, the inter-layer path computation could be performed as
computation could be performed as a multiple PCE computation where a multiple PCE computation where each member of a set of PCEs has
each member of a set of PCEs has information about the topology of information about the topology of one or more layers, but not all
one or more layers, but not all layers, and collaborate to compute layers, and collaborate to compute an end-to-end path.
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 packet-based IP/MPLS or GMPLS network and the lower-layer network is
is a GMPLS optical network. An ingress LSR in the higher-layer a GMPLS optical network. An ingress LSR in the higher-layer network
network tries to set up an LSP to an egress LSR also in the tries to set up an LSP to an egress LSR also in the higher-layer
higher-layer network across the lower-layer network, and needs a network across the lower-layer network, and needs a path in the
path in the higher-layer network. However, suppose that there is higher-layer network. However, suppose that there is no TE link
no TE link between border LSRs, which are located on the boundary between border LSRs, which are located on the boundary between the
between the higher-layer and lower-layer networks, and that the higher-layer and lower-layer networks, and that the ingress LSR does
ingress LSR does not have topology visibility in the lower layer. not have topology visibility in the lower layer. If a single-layer
If a single-layer path computation is applied for the higher-layer, path computation is applied for the higher-layer, the path
the path computation fails. On the other hand, inter-layer path computation fails. On the other hand, inter-layer path computation is
computation is able to provide a route in the higher-layer and a able to provide a route in the higher-layer and a suggestion that a
suggestion that a lower-layer LSP be setup between border LSRs, lower-layer LSP be setup between border LSRs, considering both layers
considering both layersETE topologies. as TE 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].
3.1. PCC-PCE Communication 3.1. PCC-PCE Communication
The PCC-PCE communication protocol MUST allow requests and replies The PCC-PCE communication protocol MUST allow requests and replies
for inter-layer path computation. for inter-layer path computation.
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 Therefore, a request from a PCC to a PCE MUST support the inclusion
inclusion of such an indication. 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 The PCE computes and returns a path to the PCC that the PCC can use
use to build a higher-layer or lower-layer LSP once converted to to build a higher-layer or lower-layer LSP once converted to an
an Explicit Route Object (ERO) for use in RSVP-TE signaling. There Explicit Route Object (ERO) for use in RSVP-TE signaling. There are
are two options [PCE-INTER-LAYER-FRWK]. 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, i.e. a path that includes TE links from distinct layers - Option 2: Multi-layer path. The PCE computes a "multi-layer" path,
[RFC4206]. i.e., a path that includes TE links from distinct layers [RFC4206].
It may be necessary or desirable for a PCC to control the type of It may be necessary or desirable for a PCC to control the type of
path that is produced by a PCE. For example, a PCC may know that path that is produced by a PCE. For example, a PCC may know that it
it is not possible for technological or policy reasons to signal a is not possible for technological or policy reasons to signal a
multi-layer path and that a mono-layer path is required, or the multi-layer path and that a mono-layer path is required, or the PCC
PCC may know that it does not wish the layer border node to have may know that it does not wish the layer border node to have control
control of path computation. In order to make this level of of path computation. In order to make this level of control possible,
control possible, the PCECP MUST allow the PCC to select the path the PCECP MUST allow the PCC to select the path types that may be
types that may be returned by choosing one or more from the returned by choosing one or more from the following list:
following list:
- A mono-layer path that is specified by strict hop(s). The path - A mono-layer path that is specified by strict hop(s). The path may
may include virtual TE link(s). 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 path (as strict or loose - A multi-layer path that can include the path (as strict or loose
hops) of one or more lower-layer LSPs not yet established. hops) of one or more lower-layer LSPs not yet established.
The path computation response from a PCE to a PCC MUST report the The path computation response from a PCE to a PCC MUST report the
type of path computed, and where a multi-layer path is returned, type of path computed, and where a multi-layer path is returned,
PCECP MUST support the inclusion, as part of end-to-end path, of PCECP MUST support the inclusion, as part of end-to-end path, of the
the path of the lower-layer LSPs to be established. 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), that is specified by strict hops but includes virtual TE link(s), or
or includes loose hop(s), or carries a multi-layer path that can includes loose hop(s), or carries a multi-layer path that can include
include the complete path of one or more lower-layer LSPs not yet 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 establishment of the lower-layer LSPs (nested signaling). The nested
nested signaling may increase the higher-layer connection setup signaling may increase the higher-layer connection setup latency. An
latency. An ingress LSR for the higher-layer LSP, or a PCC, needs ingress LSR for the higher-layer LSP, or a PCC, needs to know whether
to know whether nested signaling is required or not. 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. Note that a nead-end node may be present in multiple layers. Thus,
Communication of Inter-Layer Constraints when a mono-layer path is requested or supplied, PCEP MUST be able to
indicate the required/provided path layer.
3.1.3. 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 constraints for a multi-layer path. This includes control over which
which network layers may, must, or must not be included in the network layers may, must, or must not be included in the computed
computed path. Such control may be expressed in terms of the path. Such control may be expressed in terms of the switching types
switching types of the layer networks. of the layer networks. Furthermore, it may be desirable to constrain
the number of layer boundaries crossed (i.e., the number of
adaptations performed on the end-to-end path), so PCEP SHOULD include
a constraint or objective function to minimize or cap the number of
adaptations on a path, and a mechanism to report that number when a
path is supplied.
The path computation request MUST also allow for different The path computation request MUST also allow for different objective
objective functions to be applied within different network layers. functions to be applied within different network layers. For example,
For example, the path in a packet-network may need to be optimized the path in a packet-network may need to be optimized for least delay
for least delay using the IGP metric as a measure of delay, while using the IGP metric as a measure of delay, while the path in an
the path in an under-lying TDM network might be optimized for under-lying TDM network might be optimized for fewest hops.
fewest hops.
3.1.4. 3.1.4. Adaptation Capability
Adaptation Capability
It MUST be possible for the path computation request to indicate It MUST be possible for the path computation request to indicate the
the desired adaptation function at the end points of the lower- desired adaptation function at the end points of the lower-layer LSP
layer LSP that is being computed. This will be particularly that is being computed. This will be particularly important where the
important where the ingress and egress LSR participate in more ingress and egress LSR participate in more than one layer network but
than one layer network but may not be capable of all associated may not be capable of all associated adaptations.
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 When each layer is controlled by a PCE, which only has access to the
the topology information of its layer, the PCEs of each layer need topology information of its layer, the PCEs of each layer need to
to cooperate to perform inter-layer path computation. In this case, 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
support the inclusion of multiple path requests, with the desired the inclusion of multiple path requests, with the desired level of
level of diversity at each layer (link, node, SRLG). 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 In the case where there are several PCEs with distinct capabilities
capabilities available, a PCC has to select one or more available, a PCC has to select one or more appropriate PCEs.
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
architectural alternatives for interworking between MPLS and GMPLS alternatives for interworking between MPLS and GMPLS networks:
networks: overlay, integrated and augmented models overlay, integrated and augmented models [RFC3945], [RFC5145],
[RFC3945][INTWORK-FRWK][INTWORK-REQ]. [RFC5146].
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 An individual PCE MAY elect to support inter-layer computations and
and advertise its capabilities as described in the previous advertise its capabilities as described in the previous sections. PCE
sections. PCE implementations MAY provide a configuration switch implementations MAY provide a configuration switch to allow support
to allow support of inter-layer path computations to be enabled or of inter-layer path computations to be enabled or disabled. When the
disabled. When the level of support is changed, this SHOULD be re- level of support is changed, this SHOULD be re-advertised.
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 but not to advertise the fact, so that only those PCCs configured to
to know of the PCE and its capabilities can use it. 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 layer capabilities from certain PCCs by not advertising them through
through the discovery protocol, and not reporting them to the the discovery protocol, and not reporting them to the specific PCCs
specific PCCs in any PCECP capabilities exchange. Further, a PCE in any PCECP capabilities exchange. Further, a PCE MAY be directed by
MAY be directed by policy to refuse an inter-layer path policy to refuse an inter-layer path computation request for any
computation request for any reason including, but not limited to, reason including, but not limited to, the identity of the PCC that
the identity of the PCC that makes the request. 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
be accompanied by MIB objects for the control and monitoring of accompanied by MIB objects for the control and monitoring of the
the protocol and of the PCE that performs the computations. The protocol and of the PCE that performs the computations. The MIB
MIB objects MAY be provided in the same MIB module as used for objects MAY be provided in the same MIB module as used for general
general PCECP control and monitoring [PCEP-MIB] or MAY be PCECP control and monitoring [PCEP-MIB] or MAY be provided in a new
provided in a new MIB module. MIB module.
The MIB objects MUST provide the ability to control and monitor The MIB objects MUST provide the ability to control and monitor all
all aspects of PCECP relevant to inter-layer path computation. 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-
inter-area computations) and so the liveness detection and area computations) and so the liveness detection and monitoring
monitoring SHOULD be applied to each PCECP communication and SHOULD be applied to each PCECP communication and aggregated to
aggregated to report the behavior of an individual PCECP request report the behavior of an individual PCECP request to the originating
to the originating PCC. 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
PCE operating correct monitoring procedures and correlating any operating correct monitoring procedures and correlating any failures
failures back to the PCECP requests that are outstanding. These back to the PCECP requests that are outstanding. These requirements
requirements are no different from those for any cooperative PCE are no different from those for any cooperative PCE usage, and are
usage, and are expected to be already covered by general, and by expected to be already covered by general, and by inter-AS and inter-
inter-AS and inter-area implementations. 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
that verification of the correct operation of the PCE and its verification of the correct operation of the PCE and its algorithms
algorithms is out of scope for the protocol requirements, but a is out of scope for the protocol requirements, but a PCC MAY send the
PCC MAY send the same request to more than one PCE and compare 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-
inter-layer LSP, the topology graph must include information about layer LSP, the topology graph must include information about the
the inter-layer signaling and forwarding (i.e. adaptation) inter-layer signaling and forwarding (i.e. adaptation) capabilities
capabilities of each LSR in the network. 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
the requirements as described in [MLN-REQ]. 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
have significant impact on network operations. But it should be significant impact on network operations. But it should be noted that
noted that the introduction of inter-layer support to a PCE that the introduction of inter-layer support to a PCE that already
already provides mono-layer path computation might change the provides mono-layer path computation might change the loading of the
loading of the PCE and that might have an impact on the network PCE and that might have an impact on the network behavior especially
behavior especially during recovery periods immediately after a during recovery periods immediately after a network failure.
network failure.
On the other hand, it is envisioned that the use of inter-layer On the other hand, it is envisioned that the use of inter-layer path
path computation will have significant benefits to the operation computation will have significant benefits to the operation of a
of a multi-layer network including improving the network resource multi-layer network including improving the network resource usage
usage and enabling a greater number of higher-layer LSPs to be and enabling a greater number of higher-layer LSPs to be supported.
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 networks for inter-layer path computation. Security issues may also
also exist when a single PCE is granted full visibility of TE exist when a single PCE is granted full visibility of TE information
information that applies to multiple layers. 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. IANA Considerations
We would like to thank Kohei Shiomoto, Ichiro Inoue, and Dean This Informational document makes no requests for IANA action.
Cheng for their useful comments.
7. References 7. Acknowledgments
7.1. Normative Reference We would like to thank Kohei Shiomoto, Ichiro Inoue, and Dean Cheng
for their useful comments. Thanks to members of ITU-T Study Group 15
Question 14 for their constructive comments during the liaison
process.
8. References
8.1. 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 [RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths (LSP)
(LSP) Hierarchy with Generalized Multi-Protocol Label Switching Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
7.2. Informative Reference 8.2. 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
September 2006. 4657, 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.
[MLN-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- region and multi-layer networks (MRN/MLN)", draft-ietf-
gmpls-mln-reqs (work in progress). ccamp-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-ietf-pce- Inter-Layer MPLS and GMPLS Traffic Engineering", draft-
inter-layer-frwk (work in progress). ietf-pce-inter-layer-frwk (work in progress).
[PCEP-MIB] A. Koushik, and E. Stephan, "PCE communication [PCEP-MIB] A. Koushik, and E. Stephan, "PCE communication protocol
protocol(PCEP) Management Information Base", draft-kkoushik-pce- (PCEP) Management Information Base", draft-kkoushik-pce-
pcep-mib (work in progress). pcep-mib (work in progress).
[INTWORK-FRWK] K. Shiomoto, “Framework for MPLS-TE to GMPLS [RFC5145] K. Shiomoto, "Framework for MPLS-TE to GMPLS Migration",
migration,Edraft-ietf-ccamp-mpls-gmpls-interwork-fmwk (work in RFC 5145, March 2008.
progress).
[INTWORK-REQ] K. Kumaki et al., “Interworking Requirements to [RFC5146] K. Kumaki et al., "Interworking Requirements to Support
Support operation of MPLS-TE over GMPLS Networks,Edraft-ietf- Operation of MPLS-TE over GMPLS Networks", RFC 5146, March
ccamp-mpls-gmpls-interwork-reqts (work in progress). 2008.
8. AuthorsEAddresses 9. Authors' Addresses
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 12, line 35 skipping to change at page 12, line 31
Garden Air Tower Garden Air Tower
Iidabashi, Chiyoda-ku, Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN Tokyo 102-8460, JAPAN
Phone: +81-3-6678-3103 Phone: +81-3-6678-3103
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 Tomonori Takeda
NTT
3-9-11 Midori-cho,
Musashino-shi, Tokyo 180-8585, Japan
Email: takeda.tomonori@lab.ntt.co.jp
10. Intellectual Property Statement
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Intellectual Property Rights or other rights that might be claimed Intellectual Property Rights or other rights that might be claimed to
to pertain to the implementation or use of the technology pertain to the implementation or use of the technology described in
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Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
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Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
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