draft-ietf-pce-inter-layer-frwk-01.txt   draft-ietf-pce-inter-layer-frwk-02.txt 
Network Working Group Eiji Oki Network Working Group Eiji Oki
Internet Draft NTT Internet Draft NTT
Category: Informational Jean-Louis Le Roux Category: Informational Jean-Louis Le Roux
Expires: December 2006 France Telecom Expires: April 2007 France Telecom
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
October 2006
Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic
Engineering Engineering
draft-ietf-pce-inter-layer-frwk-01.txt draft-ietf-pce-inter-layer-frwk-02.txt
Status of this Memo Status of this Memo
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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 48 skipping to change at page 1, line 50
Abstract Abstract
A network may comprise of multiple layers. It is important to A network may comprise of multiple layers. It is important to
globally optimize network resources utilization, taking into globally optimize network resources utilization, taking into
account all layers, rather than optimizing resource utilization at account all layers, rather than optimizing resource utilization at
each layer independently. This allows better network efficiency to each layer independently. This allows better network efficiency to
be achieved through a process that we call inter-layer traffic be achieved through a process that we call inter-layer traffic
engineering. The Path Computation Element (PCE) can be a powerful engineering. The Path Computation Element (PCE) can be a powerful
tool to achieve inter-layer traffic engineering. tool to achieve inter-layer traffic engineering.
This document describes a framework for the PCE-based path This document describes a framework for applying the PCE-based path
computation architecture to inter-layer MPLS and GMPLS traffic computation architecture to inter-layer MPLS and GMPLS traffic
engineering. It provides suggestions for the deployment of PCE in engineering. It provides suggestions for the deployment of PCE in
support of multi-layer networks. This document also describes support of multi-layer networks. This document also describes
network models where PCE performs inter-layer traffic engineering, network models where PCE performs inter-layer traffic engineering,
and the relationship between PCE and a functional component called and the relationship between PCE and a functional component called
the Virtual Network Topology Manager (VNTM). the Virtual Network Topology Manager (VNTM).
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119
[RFC2119].
Table of Contents Table of Contents
1. Terminology.....................................................2 1. Terminology.....................................................2
2. Introduction....................................................2 2. Introduction....................................................2
3. Inter-Layer Path Computation....................................3 3. Inter-Layer Path Computation....................................3
4. Inter-layer Path Computation Models.............................5 4. Inter-layer Path Computation Models.............................5
4.1. Single PCE Inter-Layer Path Computation......................5 4.1. Single PCE Inter-Layer Path Computation......................5
4.2. Multiple PCE Inter-Layer Path Computation....................6 4.2. Multiple PCE Inter-Layer Path Computation....................6
4.3. General observation..........................................7 4.3. General observations.........................................7
5. Inter-Layer Path Control........................................7 5. Inter-Layer Path Control........................................7
5.1. VNT Management...............................................7 5.1. VNT Management...............................................8
5.2. Inter-Layer Path Control Models..............................7 5.2. Inter-Layer Path Control Models..............................8
5.2.1. Cooperation model between PCE and VNTM.....................7 5.2.1. Cooperation model between PCE and VNTM.....................8
5.2.2. Higher-Layer Signaling Trigger Model.......................9 5.2.2. Higher-Layer Signaling Trigger Model......................10
5.2.3. Examples of multi-layer ERO...............................11 5.2.3. Examples of multi-layer ERO...............................12
6. Choosing between inter-layer path control models...............12 6. Choosing between inter-layer path control models...............12
7. Security Considerations........................................13 6.1. VNTM functions:.............................................13
8. Acknowledgment.................................................14 6.2. Border LSR functions:.......................................13
9. References.....................................................14 6.3. Complete inter-layer LSP setup time:........................13
9.1. Normative Reference.........................................14 6.4. Network complexity..........................................14
9.2. Informative Reference.......................................14 7. Security Considerations........................................14
10. Authors' Addresses...........................................14 8. Acknowledgment.................................................15
11. Intellectual Property Statement..............................15 9. References.....................................................15
9.1. Normative Reference.........................................15
9.2. Informative Reference.......................................15
10. Authors' Addresses...........................................16
11. Intellectual Property Statement..............................16
1. Terminology 1. Terminology
This document uses terminology from the PCE-based path computation This document uses terminology from the PCE-based path computation
Architecture [PCE-ARCH] and also common terminology from Multi architecture [RFC4655] and also common terminology from Multi
Protocol Label Switching (MPLS) [RFC3031], Generalized MPLS (GMPLS) Protocol Label Switching (MPLS) [RFC3031], Generalized MPLS (GMPLS)
[RFC3945] and Multi-Layer Networks [MLN-REQ]. [RFC3945] and Multi-Layer Networks [MLN-REQ].
2. Introduction 2. Introduction
A network may comprise of multiple layers. These layers may A network may comprise of multiple layers. These layers may
represent separations of technologies (e.g., packet switch capable represent separations of technologies (e.g., packet switch capable
(PSC), time division multiplex (TDM) lambda switch capable (LSC)) (PSC), 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, PSC-2, VC4, VC12) [MLN-REQ], or a distinction between (e.g. PSC-1, PSC-2, VC4, VC12) [MLN-REQ], or a distinction between
client and server networking roles. In this multi-layer network, client and server networking roles. In this multi-layer network,
LSPs in a lower layer are used to carry higher-layer LSPs across Label Switched Paths (LSPs) in a lower layer are used to carry
higher-layer LSPs across the lower-layer network. The network
Oki et al Expires December 2006 2 Oki et al Expires April 2007 2
the lower-layer network. The network topology formed by lower-layer topology formed by lower-layer LSPs and advertised to the higher
LSPs and advertised to the higher layer is called a Virtual Network layer is called a Virtual Network Topology (VNT) [MLN-REQ].
Topology (VNT) [MLN-REQ].
It may be effective to optimize network resource utilization It may be effective to optimize network resource utilization
globally, i.e. taking into account all layers, rather than globally, i.e. taking into account all layers, rather than
optimizing resource utilization at each layer independently. This optimizing resource utilization at each layer independently. This
allows better network efficiency to be achieved and is what we call allows better network efficiency to be achieved and is what we call
inter-layer traffic engineering. This includes mechanisms allowing inter-layer traffic engineering. This includes mechanisms allowing
the computation of end-to-end paths across layers (known as inter- the computation of end-to-end paths across layers (known as inter-
layer path computation), and mechanisms for control and management layer path computation), and mechanisms for control and management
of the VNT by setting up and releasing LSPs in the lower layers of the VNT by setting up and releasing LSPs in the lower layers
[MLN-REQ]. [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-based path computation architecture [PCE-ARCH], and PCE can PCE-based path computation architecture [RFC4655], and PCE can
provide a suitable mechanism for resolving inter-layer path provide a suitable mechanism for resolving inter-layer path
computation issues. computation issues.
PCE Communication Protocol requirements for inter-layer traffic PCE Communication Protocol requirements for inter-layer traffic
engineering are set forth in [PCE-INTER-LAYER-REQ]. engineering are set forth in [PCE-INTER-LAYER-REQ].
This document describes a framework for the PCE-based path This document describes a framework for applying the PCE-based path
computation Architecture to inter-layer traffic engineering. It computation architecture to inter-layer traffic engineering. It
provides suggestions for the deployment of PCE in support of multi- provides suggestions for the deployment of PCE in support of multi-
layer networks. This document also describes network models where layer networks. This document also describes network models where
PCE performs inter-layer traffic engineering, and the relationship PCE performs inter-layer traffic engineering, and the relationship
between PCE and a functional component in charge of the control and between PCE and a functional component in charge of the control and
management of the VNT, and called the Virtual Network Topology management of the VNT, and called the Virtual Network Topology
Manager (VNTM). Manager (VNTM).
3. Inter-Layer Path Computation 3. Inter-Layer Path Computation
This section describes key topics of inter-layer path computation This section describes key topics of inter-layer path computation
in MPLS and GMPLS networks. in MPLS and GMPLS networks.
[RFC4206] defines a way to signal a higher-layer LSP, whose [RFC4206] defines a way to signal a higher-layer LSP, whose
explicit route includes hops traversed by LSPs in lower layers. The explicit route includes hops traversed by LSPs in lower layers. The
computation of end-to-end paths across layers is called Inter-Layer computation of end-to-end paths across layers is called Inter-Layer
Path Computation. Path Computation.
An LSR in the higher-layer may not have information on the lower- A Label Switching Router (LSR) in the higher-layer might not have
layer topology, particularly in an overlay or augmented model, and information on the lower-layer topology, particularly in an overlay
hence may not be able to compute an end-to-end path across layers. or augmented model, and hence may not be able to compute an end-to-
end path 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 or more PCEs to compute an end-to-end path across layers. This
could rely on a single PCE path computation where the PCE has could be achieved by rely on a single PCE path computation where
topology information about multiple layers and can directly compute the PCE has topology information about multiple layers and can
an end-to-end path across layers considering the topology of all of directly compute an end-to-end path across layers considering the
the layers. Alternatively, the inter-layer path computation could topology of all of the layers. Alternatively, the inter-layer path
be performed as a multiple PCE computation where each member of a computation could be performed as a multiple PCE computation where
set of PCEs have information about the topology of one or more each member of a set of PCEs have information about the topology of
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layers, but not all layers, and collaborate to compute an end-to- one or more layers, but not all layers, and collaborate to compute
end path. an end-to-end path.
Consider, for instance, a two-layer network where the higher-layer Consider, for instance, a two-layer network where the higher-layer
network is a packet-based IP/MPLS network or GMPLS network and the network is a packet-based IP/MPLS network or GMPLS network and the
lower-layer network is a GMPLS optical network. An ingress LSR in lower-layer network is a GMPLS optical network. An ingress LSR in
the higher-layer network tries to set up an LSP to an egress LSR the higher-layer network tries to set up an LSP to an egress LSR
also in the higher-layer network across the lower-layer network, also in the higher-layer network across the lower-layer network,
and needs a path in the higher-layer network. However, suppose that and needs a path in the higher-layer network. However, suppose that
there is no TE link between border LSRs, which are located on the there is no Traffic Engineering (TE) link between border LSRs,
boundary between the higher-layer and lower-layer networks, and which are located on the boundary between the higher-layer and
that the ingress LSR does not have topology visibility in the lower lower-layer networks, and that the ingress LSR does not have
layer. If a single-layer path computation is applied for the topology visibility in the lower layer. If a single-layer path
higher-layer, the path computation fails. On the other hand, inter- computation is applied for the higher-layer, the path computation
layer path computation is able to provide a route in the higher- fails. On the other hand, inter-layer path computation is able to
layer and a suggestion that a lower-layer LSP be setup between provide a route in the higher-layer and a suggestion that a lower-
border LSRs, considering both layers' TE topologies. layer LSP be setup between border LSRs, considering both layers' TE
topologies.
Lower-layer LSPs form a Virtual Network Topology (VNT), which can Lower-layer LSPs form a Virtual Network Topology (VNT), which can
be used for routing higher-layer LSPs or to carry IP traffic. be used for routing higher-layer LSPs or to carry IP traffic.
Inter-layer path computation for end-to-end LSPs in the higher- Inter-layer path computation for end-to-end LSPs in the higher-
layer network that span the lower-layer network may utilize the VNT, layer network that span the lower-layer network may utilize the VNT,
and PCE is a candidate for computing the paths of such higher-layer and PCE is a candidate for computing the paths of such higher-layer
LSPs within the higher-layer network. The PCE-based path LSPs within the higher-layer network. The PCE-based path
computation model can: computation model can:
- Perform a single computation on behalf of the ingress LSR using - Perform a single computation on behalf of the ingress LSR using
information gathered from more than one layer. This mode is information gathered from more than one layer. This mode is
referred to as Single PCE Computation in [PCE-ARCH]. referred to as Single PCE Computation in [RFC4655].
- Compute a path on behalf of the ingress LSR through cooperation - Compute a path on behalf of the ingress LSR through cooperation
between PCEs responsible for each layer. This mode is referred to between PCEs responsible for each layer. This mode is referred to
as Multiple PCE Computation with inter-PCE communication in [PCE- as Multiple PCE Computation with inter-PCE communication in
ARCH]. [RFC4655].
- Perform separate path computations on behalf of the TE-LSP head- - Perform separate path computations on behalf of the TE-LSP head-
end and each transit LSR that is the entry point to a new layer. end and each transit LSR that is the entry point to a new layer.
This mode is referred to as Multiple PCE Computation (without This mode is referred to as Multiple PCE Computation (without
inter-PCE communication) in [PCE-ARCH]. This option utilizes per- inter-PCE communication) in [RFC4655]. This option utilizes per-
layer path computation performed independently by successive PCEs. layer path computation performed independently by successive PCEs.
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 use
to build an MPLS or GMPLS LSP once converted to an Explicit Route to build an MPLS or GMPLS LSP once converted to an Explicit Route
Object (ERO) for use in RSVP-TE signaling. There are two options. Object (ERO) for use in RSVP-TE signaling. There are two options.
- Option 1: Mono-layer path. - Option 1: Mono-layer path.
The PCE computes a "mono layer" path, i.e. a path that includes The PCE computes a "mono-layer" path, i.e., a path that includes
only TE-links from the same layer. There are two cases for this only TE links from the same layer. There are two cases for this
option. In the first case the PCE computes a path that includes option. In the first case the PCE computes a path that includes
already established lower-layer LSPs or expected lower-layer LSPs already established lower-layer LSPs or expected lower-layer LSPs
to be estblished: that is the resulting ERO includes sub-object(s) to be established: that is the resulting ERO includes sub-object(s)
corresponding to lower-layer hierarchical LSPs expressed as the TE corresponding to lower-layer hierarchical LSPs expressed as the TE
link identifiers, which can be numbered or unnumbered ones, of the link identifiers, which can be numbered or unnumbered ones, of the
hierarchical LSPs when advertised as TE links in the higher-layer
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hierarchical LSPs when advertised as TE links in the higher-layer
network. The TE link may be a regular TE link that is actually network. The TE link may be a regular TE link that is actually
established, or a virtual TE link that is not established yet (see established, or a virtual TE link that is not established yet (see
[MLN-REQ]). If it is a regular TE link, this does not trigger new [MLN-REQ]). If it is a regular TE link, this does not trigger new
lower-layer LSP setup, but the utilization of existing lower-layer lower-layer LSP setup, but the utilization of existing lower-layer
LSPs. If it is a virtual TE link, this triggers a new lower-layer LSPs. If it is a virtual TE link, this triggers a new lower-layer
LSP setup (provided that there are available resources in the lower LSP setup (provided that there are available resources in the lower
layer). A transit LSR corresponding to the entry point of the layer). A transit LSR corresponding to the entry point of the
virtual TE link is expected to trigger the new lower-layer LSP virtual TE link is expected to trigger the new lower-layer LSP
setup. Note that the path of a virtual TE link is not necessarily setup. Note that the path of a virtual TE link is not necessarily
known in advance, and this may require path computation either on known in advance, and this may require path computation either on
the entry point or on a PCE. The second case is that the PCE the entry point or on a PCE. The second case is that the PCE
computes a path that includes loose hop(s). The higher layer would computes a path that includes loose hop(s). The higher layer path
select which lower layers to use and would select the entry and would select which lower layer paths to use and would select the
exit points from those layers, but would not select the path across entry and exit points from those layers, but would not select the
the layers. A transit LSR corresponding to the entry point is path across the layers. A transit LSR corresponding to the entry
expected to expand the loose hop (either itself or relying on the point is expected to expand the loose hop (either itself or relying
services of a PCE). Path expansion process on border LSR may result on the services of a PCE). The path expansion process on the border
either in the selection of an existing lower-layer LSP, or in the LSR may result either in the selection of an existing lower-layer
computation and setup of a new lower-layer LSP. LSP, or in the computation and setup of a new lower-layer LSP.
- Option 2: Multi-layer path. The PCE computes a "multi-layer" path, - Option 2: Multi-layer path. The PCE computes a "multi-layer" path,
i.e. a path that includes TE links from distinct layers [RFC4206]. i.e. a path that includes TE links from distinct layers [RFC4206].
Such a path can include the complete path of one or more lower- Such a path can include the complete path of one or more lower-
layer LSPs that already exist or are not yet established. In the layer LSPs that already exist or are not yet established. In the
latter case, the signaling of the higher-layer LSP will trigger the latter case, the signaling of the higher-layer LSP will trigger the
establishment of the lower-layer LSPs. establishment of the lower-layer LSPs.
4. Inter-layer Path Computation Models 4. Inter-layer Path Computation Models
skipping to change at line 263 skipping to change at line 264
In Figure 1, the network is comprised of two layers. LSR H1, H2, H3 In Figure 1, the network is comprised of two layers. LSR H1, H2, H3
and H4 belong to the higher layer, and LSRs L1 and L2 belong to the and H4 belong to the higher layer, and LSRs L1 and L2 belong to the
lower layer. The PCE is a multi-layer PCE that has visibility into lower layer. The PCE is a multi-layer PCE that has visibility into
both layers. It can perform end-to-end path computation across both layers. It can perform end-to-end path computation across
layers (single PCE path computation). For instance, it can compute layers (single PCE path computation). For instance, it can compute
an optimal path H2-L1-L2-H3-H4, for a higher layer LSP from H1 to an optimal path H2-L1-L2-H3-H4, for a higher layer LSP from H1 to
H4. This path includes the path of a lower layer LSP from H2 to H3, H4. This path includes the path of a lower layer LSP from H2 to H3,
already established or not. already established or not.
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----- -----
| PCE | | PCE |
----- -----
----- ----- ----- ----- ----- ----- ----- -----
| LSR |--| LSR |................| LSR |--| LSR | | LSR |--| LSR |................| LSR |--| LSR |
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| H1 | | H2 | | H3 | | H4 | | H1 | | H2 | | H3 | | H4 |
----- -----\ /----- ----- ----- -----\ /----- -----
\----- -----/ \----- -----/
| LSR |--| LSR | | LSR |--| LSR |
| L1 | | L2 | | L1 | | L2 |
----- ----- ----- -----
Figure 1 : Multi-Layer PCE - A single PCE with multi-layer Figure 1 : Multi-Layer PCE - A single PCE with multi-layer
visibility visibility
skipping to change at line 297 skipping to change at line 297
be driven by scalability considerations, as in this mode a PCE only be driven by scalability considerations, as in this mode a PCE only
needs to maintain topology information of one layer (TED size needs to maintain topology information of one layer (TED size
reduction). reduction).
These PCEs are called mono-layer PCEs. Mono-layer PCEs collaborate These PCEs are called mono-layer PCEs. Mono-layer PCEs collaborate
to compute an end-to-end optimal path across layers. to compute an end-to-end optimal path across layers.
In Figure 2, there is one PCE in each layer. The PCEs from each In Figure 2, there is one PCE in each layer. The PCEs from each
layer collaborate to compute an end-to-end path across layers. PCE layer collaborate to compute an end-to-end path across layers. PCE
Hi is responsible for computations in the higher layer and may Hi is responsible for computations in the higher layer and may
“consult” with PCE Lo to compute paths across the lower layer. PCE "consult" with PCE Lo to compute paths across the lower layer. PCE
Lo is responsible for path computation in the lower layer. A simple Lo is responsible for path computation in the lower layer. A simple
example of cooperation between the PCEs could be: PCE Hi requests a example of cooperation between the PCEs could be: PCE Hi requests a
path H2-H3 from PCE Lo. Of course more complex cooperation may be path H2-H3 from PCE Lo. Of course more complex cooperation may be
required if an end-to-end optimal path is desired. required if an end-to-end optimal path is desired.
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----- -----
| PCE | | PCE |
| Hi | | Hi |
--+-- --+--
| |
----- ----- | ----- ----- ----- ----- | ----- -----
| LSR |--| LSR |............|...........| LSR |--| LSR | | LSR |--| LSR |............|...........| LSR |--| LSR |
| H1 | | H2 | | | H3 | | H4 | | H1 | | H2 | | | H3 | | H4 |
----- -----\ --+-- /----- ----- ----- -----\ --+-- /----- -----
\ | PCE | / \ | PCE | /
\ | Lo | / \ | Lo | /
\ ----- / \ ----- /
\ / \ /
\----- -----/ \----- -----/
| LSR |--| LSR | | LSR |--| LSR |
| L1 | | L2 | | L1 | | L2 |
----- ----- ----- -----
Figure 2 : Cooperating Mono-Layer PCEs Multiple PCEs with single- Figure 2 : Cooperating Mono-Layer PCEs - Multiple PCEs with single-
layer visibility layer visibility
Oki et al Expires December 2006 6 4.3. General observations
4.3. General observation
- Depending on implementation details, inter-layer path computation - Depending on implementation details, inter-layer path computation
time in the Single PCE inter-layer path computation model may be time in the Single PCE inter-layer path computation model may be
less than that of the Multiple PCE model with cooperating mono- less than that of the Multiple PCE model with cooperating mono-
layer PCEs, because there is no requirement to exchange messages layer PCEs, because there is no requirement to exchange messages
between cooperating PCEs. between cooperating PCEs.
- When TE topology for all layered networks is visible within one - When TE topology for all layered networks is visible within one
routing domain, the single PCE inter-layer path computation model routing domain, the single PCE inter-layer path computation model
may be adopted because a PCE is able to collect all layers' TE may be adopted because a PCE is able to collect all layers' TE
topologies by participating in only one routing domain. topologies by participating in only one routing domain.
- As the single PCE inter-layer path computation model uses more TE - As the single PCE inter-layer path computation model uses more TE
topology information than is used by PCEs in the Multiple PCE path topology information than is used by PCEs in the Multiple PCE path
computation model, it requires more computation power and memory. computation model, it requires more computation power and memory.
When there are multiple candidate layer border nodes (we may say
that the higher layer is multi-homed), optimal path computation
requires that all the possible paths transiting different layer
border nodes or links be examined. This is relatively simple in the
single PCE inter-layer path computation model because the PCE has
full visibility - the computation is similar to the computation
within a single domain of a single layer. In the multiple PCE
inter-layer path computation model, backward recursive techniques
described in [BRPC] could be used, by considering layers as
separate domains.
5. Inter-Layer Path Control 5. Inter-Layer Path Control
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5.1. VNT Management 5.1. VNT Management
As a result of inter-layer path computation, a PCE may determine As a result of inter-layer path computation, a PCE may determine
that there is insufficient bandwidth available in the higher-layer that there is insufficient bandwidth available in the higher-layer
network to support this or future higher-layer LSPs. The problem network to support this or future higher-layer LSPs. The problem
might be resolved if new LSPs are provisioned across the lower- might be resolved if new LSPs are provisioned across the lower-
layer network. Further, the modification, re-organization and new layer network. Further, the modification, re-organization and new
provisioning of lower-layer LSPs may enable better utilization of provisioning of lower-layer LSPs may enable better utilization of
lower-layer network resources given the demands of the higher-layer lower-layer network resources given the demands of the higher-layer
network. In other words, the VNT needs to be controlled or managed network. In other words, the VNT needs to be controlled or managed
in cooperation with inter-layer path computation. in cooperation with inter-layer path computation.
A VNT Manager (VNTM) is defined as a network element that manages A VNT Manager (VNTM) is defined as a network element that manages
and controls the VNT. PCE and "VNT Management" are distinct and controls the VNT. PCE and "VNT Management" are distinct
functions that may or may not be co-located. To describe each functions that may or may not be co-located. To describe each
function clearly, VNTM is considered as a functional element in function clearly, VNTM is considered as a functional element in
this draft. this draft.
5.2. Inter-Layer Path Control Models 5.2. Inter-Layer Path Control Models
5.2.1. 5.2.1. Cooperation model between PCE and VNTM
Cooperation model between PCE and VNTM
----- ------ ----- ------
| PCE |--->| VNTM | | PCE |--->| VNTM |
----- ------ ----- ------
^ : ^ :
: : : :
: : : :
v V v V
----- ----- ----- ----- ----- ----- ----- -----
| LSR |----| LSR |................| LSR |----| LSR | | LSR |----| LSR |................| LSR |----| LSR |
| H1 | | H2 | | H3 | | H4 | | H1 | | H2 | | H3 | | H4 |
----- -----\ /----- ----- ----- -----\ /----- -----
\----- -----/ \----- -----/
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| LSR |--| LSR | | LSR |--| LSR |
| L1 | | L2 | | L1 | | L2 |
----- ----- ----- -----
Figure 3: Cooperation model between PCE and VNTM Figure 3: Cooperation model between PCE and VNTM
A multi-layer network consists of higher-layer and lower-layer A multi-layer network consists of higher-layer and lower-layer
networks. LSRs H1, H2, H3, and H4 belong to the higher-layer networks. LSRs H1, H2, H3, and H4 belong to the higher-layer
network, LSRs H2, L1, L2, and H3 belong to the lower-layer network, network, LSRs H2, L1, L2, and H3 belong to the lower-layer network,
as shown in Figure 3. Consider that H1 requests PCE to compute an as shown in Figure 3. Consider that H1 requests PCE to compute an
inter-layer path between H1 and H4. There is no TE link in the inter-layer path between H1 and H4. There is no TE link in the
higher-layer between H2 and H3 before the path computation request. higher-layer between H2 and H3 before the path computation request.
The roles of PCE and VNTM are as follows. PCE performs inter-layer The roles of PCE and VNTM are as follows. PCE performs inter-layer
path computation and is unable to supply a path because there is path computation and is unable to supply a path because there is no
not TE link between H2 and H3. The computation fails, but PCE TE link between H2 and H3. The computation fails, but PCE suggests
suggests to VNTM that a lower-layer LSP (H2-H3) should be to VNTM that a lower-layer LSP (H2-H3) should be established to
established to support future LSP requests. VNTM uses local policy support future LSP requests. VNTM uses local policy and possibly
and possibly management/configuration input to determine how to management/configuration input to determine how to process the
process the suggestion from PCE, and may request an ingress LSR suggestion from PCE, and may request an ingress LSR (e.g. H2) to
(e.g. H2) to establish a lower-layer LSP. VNTM or the ingress LSR
(H2) may use a PCE with visibility into the lower layer to compute Oki et al Expires April 2007 8
the path of this new LSP. establish a lower-layer LSP. VNTM or the ingress LSR (H2) may use a
PCE with visibility into the lower layer to compute the path of
this new LSP.
If the PCE cannot compute a path for the higher-layer LSP without If the PCE cannot compute a path for the higher-layer LSP without
the establishment of a further lower-layer LSP, the PCE may notify the establishment of a further lower-layer LSP, the PCE may notify
VNTM and wait for the lower-layer LSP to be set up and advertised VNTM and wait for the lower-layer LSP to be set up and advertised
as a TE link. It can then compute the complete end-to-end path for as a TE link. It can then compute the complete end-to-end path for
the higher-layer LSP and return the result to the PCC. In this case, the higher-layer LSP and return the result to the PCC. In this case,
the PCC may be kept waiting some time, and it is important that the the PCC may be kept waiting some time, and it is important that the
PCC understands this. It is also important that the PCE and VNTM PCC understands this. It is also important that the PCE and VNTM
have an agreement that the lower-layer LSP will be set up in a have an agreement that the lower-layer LSP will be set up in a
timely manner, the PCE operates a timeout, or the PCE will be timely manner, the PCE operates a timeout, or the PCE will be
skipping to change at line 425 skipping to change at line 436
of such a cooperative procedure between PCE and VNTM is as follows. of such a cooperative procedure between PCE and VNTM is as follows.
Step 1: H1 (PCC) requests PCE to compute a path between H1 and H4. Step 1: H1 (PCC) requests PCE to compute a path between H1 and H4.
In the request, it indicates that inter-layer path computation is In the request, it indicates that inter-layer path computation is
allowed. allowed.
Step 2: As a result of the inter-layer path computation, PCE judges Step 2: As a result of the inter-layer path computation, PCE judges
that a new lower-layer LSP needs to be established. that a new lower-layer LSP needs to be established.
Step 3: PCE suggests to VNTM that a new lower-layer LSP should be Step 3: PCE suggests to VNTM that a new lower-layer LSP should be
established if necessary and if acceptable within VNTM' policy established if necessary and if acceptable within VNTM's policy
constraints. The inter-layer path route computed by PCE may include constraints. The inter-layer path route computed by PCE may include
one or more virtual TE links. If PCE knows the inclusion of the one or more virtual TE links. If PCE knows the inclusion of the
virtual TE link(s) in the inter-layer route, PCE may suggest VNTM virtual TE link(s) in the inter-layer route, PCE may suggest VNTM
that the corresponding new lower-layer LSP(s) should be established. that the corresponding new lower-layer LSP(s) should be established.
Otherwise, new lower-layer LSP(s) may be setup according to the Otherwise, new lower-layer LSP(s) may be setup according to the
higher-layer signaling trigger model. higher-layer signaling trigger model.
In the above description, it is assumed that a higher layer LSP is In the above description, it is assumed that a higher layer LSP is
supported by a single lower layer LSP. However, in case of VCAT, supported by a single lower layer LSP. However, in case of VCAT,
Oki et al Expires December 2006 8
several lower layer LSPs may be used to transport a single higher several lower layer LSPs may be used to transport a single higher
layer LSP. layer LSP.
Step 4: VNTM requests an ingress LSR (e.g. H2) to establish a Step 4: VNTM requests an ingress LSR (e.g. H2) to establish a
lower-layer LSP. The request message may include a pre-computed lower-layer LSP. The request message may include a pre-computed
lower-layer LSP route obtained from the PCE responsible for the lower-layer LSP route obtained from the PCE responsible for the
lower-layer network. lower-layer network.
Step 5: The ingress LSR starts signaling to establish a lower-layer Step 5: The ingress LSR starts signaling to establish a lower-layer
LSP. LSP.
Step 6: If the lower-layer LSP setup is completed, the ingress LSR Step 6: If the lower-layer LSP setup is completed, the ingress LSR
notifies VNTM that the LSP is complete and supplies the tunnel notifies VNTM that the LSP is complete and supplies the tunnel
information. information.
Step 7: VNTM replies to PCE to inform it that the lower-layer LSP Step 7: VNTM replies to PCE to inform it that the lower-layer LSP
is now established, and includes the lower-layer tunnel information. is now established, and includes the lower-layer tunnel information.
Alternatively, PCE may get to know about the existence of the Alternatively, PCE may get to know about the existence of the
lower-layer LSP when a new TE link in the higher-layer lower-layer LSP when a new TE link in the higher-layer
Oki et al Expires April 2007 9
corresponding to the lower-layer LSP is advertised to PCE through corresponding to the lower-layer LSP is advertised to PCE through
the IGP. the IGP.
Step 8: PCE replies to H1 (PCC) with a computed higher-layer LSP Step 8: PCE replies to H1 (PCC) with a computed higher-layer LSP
route. The computed path is categorized as a mono-layer path that route. The computed path is categorized as a mono-layer path that
includes the already-established lower layer-LSP. The higher-layer includes the already-established lower layer-LSP. The higher-layer
route is specified as H2-H3-H4, where all hops are strict. route is specified as H2-H3-H4, where all hops are strict.
Step 9: H1 initiates signaling with the computed path H2-H3-H4 to Step 9: H1 initiates signaling with the computed path H2-H3-H4 to
establish the higher-layer LSP. establish the higher-layer LSP.
5.2.2. 5.2.2. Higher-Layer Signaling Trigger Model
Higher-Layer Signaling Trigger Model
----- -----
| PCE | | PCE |
----- -----
^ ^
: :
: :
v v
----- ----- ----- ----- ----- ----- ----- -----
| LSR |----| LSR |................| LSR |--| LSR | | LSR |----| LSR |................| LSR |--| LSR |
skipping to change at line 491 skipping to change at line 501
\----- -----/ \----- -----/
| LSR |--| LSR | | LSR |--| LSR |
| L1 | | L2 | | L1 | | L2 |
----- ----- ----- -----
Figure 4: Higher-layer signaling trigger model Figure 4: Higher-layer signaling trigger model
Figure 4 shows the higher-layer signaling trigger model. As in the Figure 4 shows the higher-layer signaling trigger model. As in the
case described in section 5.2.1, consider that H1 requests PCE to case described in section 5.2.1, consider that H1 requests PCE to
compute an inter-layer path between H1 and H4. There is no TE link compute an inter-layer path between H1 and H4. There is no TE link
Oki et al Expires December 2006 9
in the higher-layer between H2 and H3 before the path computation in the higher-layer between H2 and H3 before the path computation
request. request.
If PCE judges that a lower-layer LSP needs to be established based If PCE judges that a lower-layer LSP needs to be established based
on the inter-layer path computation result, a lower-layer LSP is on the inter-layer path computation result, a lower-layer LSP is
established during the higher-layer signaling procedure. After PCE established during the higher-layer signaling procedure. After PCE
completes inter-layer path computation, PCE sends a reply message completes inter-layer path computation, PCE sends a reply message
including explicit route to the ingress LSR (PCC). There are two including explicit route to the ingress LSR (PCC). There are two
ways to express the higher-layer LSP route, which are a multi-layer ways to express the higher-layer LSP route, which are a multi-layer
path and a mono-layer path that includes loose hop(s). path and a mono-layer path that includes loose hop(s).
skipping to change at line 514 skipping to change at line 522
In the higher-layer signaling trigger model with a multi-layer path, In the higher-layer signaling trigger model with a multi-layer path,
a high-layer LSP route includes a route for a lower-layer LSP that a high-layer LSP route includes a route for a lower-layer LSP that
is not yet established. An LSR that is located at the boundary is not yet established. An LSR that is located at the boundary
between the higher-layer and lower-layer networks, called a border between the higher-layer and lower-layer networks, called a border
LSR, receives a higher-layer signaling message and then may start LSR, receives a higher-layer signaling message and then may start
to setup the lower-layer LSP. Note that it depends on a policy at to setup the lower-layer LSP. Note that it depends on a policy at
the border LSR whether the higher-layer signaling triggers a lower- the border LSR whether the higher-layer signaling triggers a lower-
layer LSP setup. An example procedure of the signaling trigger layer LSP setup. An example procedure of the signaling trigger
model with a multi-layer path is as follows. model with a multi-layer path is as follows.
Oki et al Expires April 2007 10
Step 1: H1 (PCC) requests PCE to compute a path between H1 and H4. Step 1: H1 (PCC) requests PCE to compute a path between H1 and H4.
The request indicates that inter-layer path computation is allowed. The request indicates that inter-layer path computation is allowed.
Step 2: As a result of the inter-layer path computation, PCE judges Step 2: As a result of the inter-layer path computation, PCE judges
that a new lower-layer LSP needs to be established. that a new lower-layer LSP needs to be established.
Step 3: PCE replies to H1 (PCC) with a computed multi-layer route Step 3: PCE replies to H1 (PCC) with a computed multi-layer route
including higher-layer and lower-layer LSP routes. The route may be including higher-layer and lower-layer LSP routes. The route may be
specified as H2-L1-L2-H3-H4, where all hops are strict. specified as H2-L1-L2-H3-H4, where all hops are strict.
skipping to change at line 545 skipping to change at line 554
time that the computation was performed and the moment when the time that the computation was performed and the moment when the
higher-layer signaling message reached the border LSR. In this case, higher-layer signaling message reached the border LSR. In this case,
the border LSR may select such a lower-layer LSP without the need the border LSR may select such a lower-layer LSP without the need
to signal a new LSP provided that the lower-layer LSP satisfies the to signal a new LSP provided that the lower-layer LSP satisfies the
explicit route in the higher-layer signaling request. explicit route in the higher-layer signaling request.
Step 6: After the lower-layer LSP is established, the higher-layer Step 6: After the lower-layer LSP is established, the higher-layer
signaling continues along the specified higher-layer route of H2- signaling continues along the specified higher-layer route of H2-
H3-H4. H3-H4.
On the other hand, in the signaling trigger model with mono-layer On the other hand, in the signaling trigger model with a mono-layer
path, a higher-layer LSP route includes a loose or strict hop to path, a higher-layer LSP route includes a loose or strict hop to
Oki et al Expires December 2006 10
traverse the lower-layer network between the two border LSRs. In traverse the lower-layer network between the two border LSRs. In
the strict hop case, a virtual TE link may be advertised, but a the strict hop case, a virtual TE link may be advertised, but a
lower-layer LSP is not setup. A border LSR that receives a higher- lower-layer LSP is not setup. A border LSR that receives a higher-
layer signaling message needs to determine a path for a new lower- layer signaling message needs to determine a path for a new lower-
layer LSP. It applies local policy to verify that a new LSP is layer LSP. It applies local policy to verify that a new LSP is
acceptable and then either consults a PCE with responsibility for acceptable and then either consults a PCE with responsibility for
the lower-layer network or computes the path by itself, and the lower-layer network or computes the path by itself, and
initiates signaling to establish a lower-layer LSP. Again, it is initiates signaling to establish a lower-layer LSP. Again, it is
possible that a suitable lower-layer LSP has been established (or possible that a suitable lower-layer LSP has been established (or
become available) between the time that the higher-layer become available) between the time that the higher-layer
computation was performed and the moment when the higher-layer computation was performed and the moment when the higher-layer
signaling message reached the border LSR. In this case, the border signaling message reached the border LSR. In this case, the border
LSR may select such a lower-layer LSP without the need to signal a LSR may select such a lower-layer LSP without the need to signal a
new LSP provided that the lower-layer LSP satisfies the explicit new LSP provided that the lower-layer LSP satisfies the explicit
route in the higher-layer signaling request. Since the higher-layer route in the higher-layer signaling request. Since the higher-layer
signaling request used a loose hop without specifying any specifics signaling request used a loose hop without specifying any specifics
of the path within the lower-layer network, the border LSR has of the path within the lower-layer network, the border LSR has
greater freedom to choose a lower-layer LSP than in the previous greater freedom to choose a lower-layer LSP than in the previous
example. example.
Oki et al Expires April 2007 11
The difference between procedures of the signaling trigger model The difference between procedures of the signaling trigger model
with a multi-layer path and a mono-layer path is Step 5. Step 5 of with a multi-layer path and a mono-layer path is Step 5. Step 5 of
the signaling trigger model with a mono layer path is as follows: the signaling trigger model with a mono layer path is as follows:
Step 5': The border LSR (H2) that receives the higher-layer Step 5' The border LSR (H2) that receives the higher-layer
signaling message applies local policy to verify that a new LSP is signaling message applies local policy to verify that a new LSP is
acceptable and then initiates establishment of a lower-layer LSP. acceptable and then initiates establishment of a lower-layer LSP.
It either consults a PCE with responsibility for the lower-layer It either consults a PCE with responsibility for the lower-layer
network or computes the route by itself to expand the loose hop network or computes the route by itself to expand the loose hop
route in the higher-layer path. route in the higher-layer path.
5.2.3. 5.2.3. Examples of multi-layer ERO
Examples of multi-layer ERO
PCE PCE
^ ^
: :
: :
V V
H1--H2 H3--H4 H1--H2 H3--H4
\ / \ /
L1==L2==L3--L4--L5 L1==L2==L3--L4--L5
| |
skipping to change at line 604 skipping to change at line 611
\ \
H5--H6 H5--H6
Figure 5 Example of multi-layer network Figure 5 Example of multi-layer network
This section describes how lower-layer LSP setup is performed in This section describes how lower-layer LSP setup is performed in
the higher-layer signaling trigger model using an ERO that can the higher-layer signaling trigger model using an ERO that can
include subobjects in both the higher and lower layers. It gives include subobjects in both the higher and lower layers. It gives
rise to several options for the ERO when it reaches the last LSR in rise to several options for the ERO when it reaches the last LSR in
the higher layer network (H2). the higher layer network (H2).
Oki et al Expires December 2006 11
1. The next subobject is a loose hop to H3 (mono layer ERO). 1. The next subobject is a loose hop to H3 (mono layer ERO).
2. The next subobject is a strict hop to L1 followed by a loose hop 2. The next subobject is a strict hop to L1 followed by a loose hop
to H3. to H3.
3. The next subobjects are a series of hops (strict or loose) in 3. The next subobjects are a series of hops (strict or loose) in
the lower-layer network followed by H3. For example, {L1(strict), the lower-layer network followed by H3. For example, {L1(strict),
L3(loose), L5(loose), H3(strict)} L3(loose), L5(loose), H3(strict)}
In the first, the lower layer can utilize any LSP tunnel that will In the first, the lower layer can utilize any LSP tunnel that will
deliver the end-to-end LSP to H3. In the third case, the lower deliver the end-to-end LSP to H3. In the third case, the lower
layer must select an LSP tunnel that traverses L3 and L5. However, layer must select an LSP tunnel that traverses L3 and L5. However,
this does not mean that the lower layer can or should use an LSP this does not mean that the lower layer can or should use an LSP
from L1 to L3 and another from L3 to L5. from L1 to L3 and another from L3 to L5.
6. Choosing between inter-layer path control models 6. Choosing between inter-layer path control models
This section compares the cooperation model between PCE and VNTM, This section compares the cooperation model between PCE and VNTM,
and the higher-layer signaling trigger model, in terms of VNTM and the higher-layer signaling trigger model, in terms of VNTM
functions, border LSR functions, and higher-layer signaling time. functions, border LSR functions, higher-layer signaling time, and
complexity (in terms of number of states and messages). An
appropriate model is chosen, taking into all these considerations.
VNTM functions: Oki et al Expires April 2007 12
6.1. VNTM functions:
In the cooperation model, VNTM functions are required. In this In the cooperation model, VNTM functions are required. In this
model, additional overhead communications between PCE and VNTM and model, additional overhead communications between PCE and VNTM and
between VNTM and a border LSR are required. between VNTM and a border LSR are required.
In the higher-layer signaling trigger model, no VNTM functions are In the higher-layer signaling trigger model, no VNTM functions are
required, and no such communications are required. required, and no such communications are required.
If VNTM functions are not supported in a multi-layer network, the If VNTM functions are not supported in a multi-layer network, the
higher-layer signaling trigger model has to be chosen. higher-layer signaling trigger model has to be chosen.
The inclusion of VNTM functionality allows better coordination of The inclusion of VNTM functionality allows better coordination of
cross-network LSP tunnels and application of network-wide policy cross-network LSP tunnels and application of network-wide policy
that is not available in the trigger model. that is not available in the trigger model.
Border LSR functions: 6.2. Border LSR functions:
In the higher-layer signaling trigger model, a border LSR must have In the higher-layer signaling trigger model, a border LSR must have
some additional functions. It needs to trigger lower-layer some additional functions. It needs to trigger lower-layer
signaling when a higher-layer path message suggests that lower- signaling when a higher-layer path message suggests that lower-
layer LSP setup is necessary. The triggering signaling is also layer LSP setup is necessary. The triggering signaling is also
required in the cooperation case when the VNTM support virtual TE required in the cooperation case when the VNTM support virtual TE
links. Note that, if only the cooperation model is applied, it is links. Note that, if only the cooperation model is applied, it is
required that a PCE knows whether a link is a regular TE link or required that a PCE knows whether a link is a regular TE link or
virtual TE link. virtual TE link.
If the ERO in the higher-layer Path message uses a mono-layer path If the ERO in the higher-layer Path message uses a mono-layer path
or specifies loose hop, a border LSR receiving the Path message or specifies loose hop, a border LSR receiving the Path message
MUST obtain a lower-layer route either by consulting PCE or by MUST obtain a lower-layer route either by consulting PCE or by
using its own computation engine. If the ERO in the higher-layer using its own computation engine. If the ERO in the higher-layer
Path message uses multi-layer path, the border LSR MUST judge Path message uses multi-layer path, the border LSR MUST judge
whether lower-layer signaling is needed. whether lower-layer signaling is needed.
Oki et al Expires December 2006 12
In the cooperation model, no additional function for triggered In the cooperation model, no additional function for triggered
signaling in border LSRs is required except when virtual TE links signaling in border LSRs is required except when virtual TE links
are used. Therefore, if these additional functions are not are used. Therefore, if these additional functions are not
supported in border LSRs, the cooperation model, where a border LSR supported in border LSRs, the cooperation model, where a border LSR
is controlled by VNTM to set up a lower-layer LSP, has to be chosen. is controlled by VNTM to set up a lower-layer LSP, has to be chosen.
Complete inter-layer LSP setup time: 6.3. Complete inter-layer LSP setup time:
Complete inter-layer LSP setup time includes inter-layer path Complete inter-layer LSP setup time includes inter-layer path
computation, signaling, and communication time between PCC and PCE, computation, signaling, and communication time between PCC and PCE,
PCE and VNTM, and VNTM and LSR. In the cooperation model, the PCE and VNTM, and VNTM and LSR. In the cooperation model, the
additional communication steps are required compared with the additional communication steps are required compared with the
higher-layer signaling trigger model. On the other hand, the higher-layer signaling trigger model. On the other hand, the
cooperation model provides better control at the cost of a longer cooperation model provides better control at the cost of a longer
service setup time. service setup time.
Note that, in terms of higher-layer signaling time, in the higher- Note that, in terms of higher-layer signaling time, in the higher-
layer signaling trigger model, the required time from when higher- layer signaling trigger model, the required time from when higher-
layer signaling starts to when it is completed, is more than that layer signaling starts to when it is completed, is more than that
Oki et al Expires April 2007 13
of the cooperation model except when any virtual TE link is of the cooperation model except when any virtual TE link is
included. This is because the former model requires lower-layer included. This is because the former model requires lower-layer
signaling to take place during the higher-layer signaling. A signaling to take place during the higher-layer signaling. A
higher-layer ingress LSR has to wait for more time until the higher-layer ingress LSR has to wait for more time until the
higher-layer signaling is completed. A higher-layer ingress LSR is higher-layer signaling is completed. A higher-layer ingress LSR is
required to be tolerant of longer path setup times. required to be tolerant of longer path setup times.
An appropriate model is chosen, taking into all of the above An appropriate model is chosen, taking into all of the above
considerations. considerations.
6.4. Network complexity
If the higher and lower layer networks have multiple interconnects
then optimal path computation for end-to-end LSPs that cross the
layer boundaries is non-trivial. The higher layer LSP must be
routed to the correct layer border nodes to achieve optimality in
both layers.
Where the lower layer LSPs are advertised into the higher layer
network as TE links, the computation can be resolved in the higher
layer network. Care needs to be taken in the allocation of TE
metrics (i.e., costs) to the lower layer LSPs as they are
advertised as TE links into the higher layer network, and this
might be an issue for a VNT Manager component.
In the single PCE model an end-to-end path can be found in a single
computation because there is full visibility into both layers and
all possible paths through all layer interconnects can be
considered.
Where PCEs cooperate to determine a path, an iterative computation
model such as [BRPC] can be used to select an optimal path across
layers.
When non-cooperating mono-layer PCEs, each of which is in each
layer, are used with a triggered LSP model, it is not possible to
determine the best border LSRs, and connectivity cannot even be
guaranteed. In this case, signaling crankback techniques [CRANK]
can be used to eventually achieve connectivity, but optimality is
far harder to achieve. In this model, a PCE that is requested to
compute a path by an ingress LSR expects a border LSR to setup a
lower-layer path triggered by high-layer signaling when there is no
TE link between border LSRs.
7. Security Considerations 7. Security Considerations
Inter-layer traffic engineering with PCE may raise new security Inter-layer traffic engineering with PCE may raise new security
issues in both inter-layer path control models. issues in both inter-layer path control models.
In the cooperation model between PCE and VNTM, when PCE judges a In the cooperation model between PCE and VNTM, when PCE judges a
new lower-layer LSP, communications between PCE and VNTM and new lower-layer LSP, communications between PCE and VNTM and
between VNTM and a border LSR are needed. In this case, there are between VNTM and a border LSR are needed. In this case, there are
some security concerns that need to be addressed for these some security concerns that need to be addressed for these
Oki et al Expires April 2007 14
communications. These communications should have some security communications. These communications should have some security
mechanisms to ensure authenticity, privacy and integrity. mechanisms to ensure authenticity, privacy and integrity.
In the higher-layer signaling trigger model, there are several In the higher-layer signaling trigger model, there are several
security concerns. First, PCE may inform PCC, which is located in security concerns. First, PCE may inform PCC, which is located in
the higher-layer network, of multi-layer path information that the higher-layer network, of multi-layer path information that
includes an ERO in the lower-layer network, while the PCC may not includes an ERO in the lower-layer network, while the PCC may not
have TE topology visibility into the lower-layer network. This have TE topology visibility into the lower-layer network. This
raises a security concern, where lower-layer hop information is raises a security concern, where lower-layer hop information is
known to transit LSRs supporting a higher-layer LSP. Some security known to transit LSRs supporting a higher-layer LSP. Some security
mechanisms to ensure authenticity, privacy and integrity may be mechanisms to ensure authenticity, privacy and integrity may be
used. used.
Security issues may also exist when a single PCE is granted full Security issues may also exist when a single PCE is granted full
visibility of TE information that applies to multiple layers. visibility of TE information that applies to multiple layers.
Oki et al Expires December 2006 13
8. Acknowledgment 8. Acknowledgment
We would like to thank Kohei Shiomoto, Ichiro Inoue, Julien Meuric, We would like to thank Kohei Shiomoto, Ichiro Inoue, Julien Meuric,
Jean-Francois Peltier, and Young Lee for their useful comments. Jean-Francois Peltier, Young Lee, and Ina Minei for their useful
comments.
9. References 9. References
9.1. Normative Reference 9.1. 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) Hierarchy with Generalized Multi-Protocol Label Switching (LSP) Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4208] G. Swallow et al., "Generalized Multiprotocol Label [RFC4208] G. Swallow et al., "Generalized Multiprotocol Label
Switching (GMPLS) User-Network Interface (UNI): Resource Switching (GMPLS) User-Network Interface (UNI): Resource
ReserVation Protocol-Traffic Engineering (RSVP-TE) Support for the ReserVation Protocol-Traffic Engineering (RSVP-TE) Support for the
Overlay Model", RFC 4208, October 2005. Overlay Model", RFC 4208, October 2005.
[PCE-ARCH] A. Farrel, JP. Vasseur and J. Ash, "Path Computation [RFC4655] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation
Element (PCE) Architecture", draft-ietf-pce-architecture (work in Element (PCE)-Based Architecture", RFC 4655, August 2006.
progress).
9.2. Informative Reference 9.2. Informative Reference
[PCE-COM-REQ] J. Ash, J.L Le Roux et al., "PCE Communication [RFC4657] J. Ash, J.L Le Roux et al., " Path Communication Element
Protocol Generic Requirements", draft-ietf-pce-comm-protocol-gen- (PCE) Communication Protocol Generic Requirements", RFC 4657,
reqs (work in progress). September 2006.
[PCE-DISC-REQ] JL Le Roux et al., "Requirements for Path [RFC4674] JL Le Roux et al., "Requirements for Path Computation
Computation Element (PCE) Discovery", draft-ietf-pce-discovery-reqs Element (PCE) Discovery", RFC 4674, September 2006.
(work in progress).
Oki et al Expires April 2007 15
[MLN-REQ] K. Shiomoto et al., "Requirements for GMPLS-based multi- [MLN-REQ] K. Shiomoto et al., "Requirements for GMPLS-based multi-
region networks (MRN) ", draft-ietf-ccamp-gmpls-mln-reqs (work in region networks (MRN) ", draft-ietf-ccamp-gmpls-mln-reqs (work in
progress). progress).
[PCE-INTER-LAYER-REQ] E. Oki et al., "PCC-PCE Communication [PCE-INTER-LAYER-REQ] E. Oki et al., "PCC-PCE Communication
Requirements for Inter-Layer Traffic Engineering," draft-ietf-pce- Requirements for Inter-Layer Traffic Engineering", draft-ietf-pce-
inter-layer-req (work in progress). inter-layer-req (work in progress).
[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).
[BRPC] JP. Vasseur et al., "A Backward Recursive PCE-based
Computation (BRPC) procedure to compute shortest inter-domain
Traffic Engineering Label Switched Paths", draft-ietf-pce-brpc
(work in progress). (work in progress).
[CRANK] A. Farrel et al., "Crankback Signaling Extensions for MPLS
and GMPLS RSVP-TE", draft-ietf-ccamp-crankback (work in progress).
10. Authors' Addresses 10. Authors' Addresses
Eiji Oki Eiji Oki
NTT NTT
Oki et al Expires December 2006 14
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,
22300 Lannion, France 22300 Lannion, France
Email: jeanlouis.leroux@francetelecom.com Email: jeanlouis.leroux@orange-ft.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
Email: adrian@olddog.co.uk Email: adrian@olddog.co.uk
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Oki et al Expires April 2007 16
specification can be obtained from the IETF on-line IPR repository specification can be obtained from the IETF on-line IPR repository
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skipping to change at line 824 skipping to change at line 876
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Copyright (C) The Internet Society (2006). This document is Copyright (C) The Internet Society (2006). This document is
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Oki et al Expires December 2006 15
78, and except as set forth therein, the authors retain all their 78, and except as set forth therein, the authors retain all their
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Oki et al Expires December 2006 16 Oki et al Expires April 2007 17
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