TEAS Working Group Fabio Peruzzini
Internet Draft TIM
Intended status: Informational Daniel King
Old Dog Consulting
Gabriele Galimberti
Cisco
Expires: January 2020 July 8, 2019
Applicability of Abstraction and Control of Traffic Engineered
Networks (ACTN) to Packet Optical Integration (POI)
draft-peru-teas-actn-poi-applicability-00.txt
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Abstract
This document considers the applicability of ACTN to Packet Optical
Integration (POI) and IP and Optical DWDM domain internetworking,
and specifically the YANG models being defined by the IETF to
support this deployment architecture.
In this document we highlight the IETF protocols and data models
that may be used for the ACTN and control of POI networks, with
particular focus on the interfaces between the MDSC (Multi-Domain
Service Coordinator) and the underlying Packet and Optical Domain
Controllers (P-PNC and O-PNC) to support Packet Optical Integration
(POI) use cases.
Table of Contents
1. Introduction...................................................3
2. Reference Scenario.............................................3
2.1. Generic Assumptions.......................................5
3. Scenario 1 - Topology discovery, network inventory and
multilayer correlation.........................................5
3.1. Common YANG models used at the MPIs.......................6
3.1.1. YANG models used at the Optical MPIs.................6
3.1.2. Required YANG models at the Packet MPIs..............7
3.2. Inter-domain link Discovery...............................7
4. Scenario 2 - Provisioning of an IP Link over DWDM..............8
4.1. YANG models used at the MPIs..............................8
4.1.1. YANG models used at the Optical MPIs.................8
4.1.2. Required YANG models at the Packet MPIs..............9
4.2. IP Link Setup Procedure...................................9
5. Security Considerations.......................................10
6. Operational Considerations....................................10
7. IANA Considerations...........................................10
8. References....................................................10
8.1. Normative References.....................................10
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8.2. Informative References...................................12
9. Acknowledgments...............................................12
10. Authors' Addresses...........................................12
1. Introduction
This document aims to collect information about the level of
protocols and data models standardization implementations of ACTN
architecture, with particular focus on the interfaces between the
MDSC (Multi-Domain Service Coordinator) and underlying Packet and
Optical Domain Controllers (P-PNC and O-PNC), for Packet Optical
Integration (POI).
Understanding the level of standardization and the gaps will help to
better assess the feasibility of integration between IP and Optical
DWDM domain, in an end-to-end multi-vendor service provisioning
perspective.
In this document, key use cases will be described, and for each use
case according to the ACTN architecture shown in Figure 1, the scope
will address the interactions with both the IP and optical domains.
For both domains, information on functions, protocols and data
models, available on each use case, must be reported.
2. Reference Scenario
This document is considering a network scenario with multiple
Optical domains and multiple Packet domains.
Figure 1 shows this scenario in case of two Optical domains and two
Packet domains:
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+----------+
| MDSC |
+-----+----+
|
+-----------+-----+------+-----------+
| | | |
+----+----+ +----+----+ +----+----+ +----+----+
| P-PNC 1 | | O-PNC 1 | | O-PNC 2 | | P-PNC 2 |
+----+----+ +----+----+ +----+----+ +----+----+
| | | |
| \ / |
+-------------------+ \ / +-------------------+
CE / PE ASBR \ | / / ASBR PE \ CE
o--/---o o---\-|-------|--/---o o---\--o
\ : : / | | \ : : /
\ : AS Domain 1 : / | | \ : AS Domain 2 : /
+-:---------------:-+ | | +-:---------------:--+
: : | | : :
: : | | : :
+-:---------------:------+ +-------:---------------:--+
/ : : \ / : : \
/ o...............o \ / o...............o \
\ Optical Domain 1 / \ Optical Domain 2 /
\ / \ /
+------------------------+ +--------------------------+
Figure 1 - Reference Scenario
The ACTN architecture, defined in [RFC8453], is used to control this
multi-domain network where each P-PNC is responsible for controlling
its IP domain (AS), and each O-PNC is responsible for controlling
its Optical Domain. The MDSC is responsible for coordinating the
whole multi-domain multi-layer (Packet and Optical) network. A
specific standard interface (MPI) permits MDSC to interact with the
different Provisioning Network Controller (O/P-PNCs). The MPI
interface presents an abstracted topology to MDSC hiding technology-
specific aspects of the network and hiding topology details
depending on the policy chosen regarding the level of abstraction
supported. The level of abstraction can be obtained based on P-PNC
and O-PNC configuration parameters (e.g. provide the potential
connectivity between any PE and any ABSR in an MPLS-TE network).
In this scenario it is assumed that:
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o The domain boundaries between the IP and Optical domains are
congruent. In other words, one Optical domain supports
connectivity between Routers in one and only one Packet Domain.
o Inter-domain links exist only between Packet domains (i.e.,
between ASBR routers) and between Packet and Optical domains
(i.e., between routers and ROADMs). In other words, there are no
inter-domain links between Optical domains
o The interfaces between the routers and the ROADM's are "Ethernet"
physical interfaces
o The interfaces between the ASBR routers are "Ethernet" physical
interfaces
2.1. Generic Assumptions
This section describes general assumptions which are applicable at
all the MPI interfaces, between each PNC (Optical or Packet) and the
MDSC, and also to all the scenarios discussed in this document.
The data models used on these interfaces are assumed to use the YANG
1.1 Data Modeling Language, as defined in [RFC7950].
The RESTCONF protocol, as defined in [RFC8040], using the JSON
representation, defined in [RFC7951], is assumed to be used at these
interfaces.
As required in [RFC8040], the "ietf-yang-library" YANG module
defined in [RFC8525] is used to allow the MDSC to discover the set
of YANG modules supported by each PNC at its MPI.
3. Scenario 1 - Topology discovery, network inventory and multilayer
correlation
In this scenario, the MSDC needs to discover the network topology,
at both WDM and IP layers, in terms of nodes (NEs) and links,
including inter-domain links.
Each PNC provides to the MDSC an abstract topology view of the WDM
or of the IP topology of the domain it controls. This topology is
abstract in the sense that some detailed NE information is hidden at
the MPI, but all the NEs and physical links are exposed as abstract
nodes and links within the abstract topology.
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The MDSC also keeps an up-to-date network inventory of both IP and
WDM layers and correlates such information (e.g., which port,
lambda, and the direction being used by a specific IP service on the
WDM equipment).
3.1. Common YANG models used at the MPIs
Both Optical and Packet PNCs use the following common topology YANG
models at the MPI to report their abstract topologies:
o The Base Network Model, defined in the "ietf-network" YANG module
of [RFC8345]
o The Base Network Topology Model, defined in the "ietf-network-
topology" YANG module of [RFC8345], which augments the Base
Network Model
o The TE Topology Model, defined in the "ietf-te-topology" YANG
module of [TE-TOPO], which augments the Base Network Topology
Model
These common YANG models are generic and augmented by technology-
specific YANG modules as described in the following sections.
3.1.1. YANG models used at the Optical MPIs
The Optical PNC also uses at least the following technology-specific
topology YANG models, providing WDM and Ethernet technology-specific
augmentations of the generic TE Topology Model:
o The WSON Topology Model, defined in the "ietf-wson-topology" YANG
modules of [WSON-TOPO], or the Flexi-grid Topology Model, defined
in the "ietf-flexi-grid-topology" YANG module of [Flexi-TOPO].
o The Ethernet Topology Model, defined in the "ietf-eth-te-
topology" YANG module of [CLIENT-TOPO]
The WSON Topology Model or, alternatively, the Flexi-grid Topology
model is used to report the DWDM network topology (e.g., ROADMs and
links) depending on whether the DWDM optical network is based on
fixed grid or flexible-grid.
The Ethernet Topology is used to report the access links between the
IP routers and the edge ROADMs.
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3.1.2. Required YANG models at the Packet MPIs
The Packet PNC also uses at least the following technology-specific
topology YANG models, providing IP and Ethernet technology-specific
augmentations of the generic Topology Models:
o The L3 Topology Model, defined in the "ietf-l3-unicast-topology"
YANG modules of [RFC8346], which augments the Base Network
Topology Model
o The Ethernet Topology Model, defined in the "ietf-eth-te-
topology" YANG module of [CLIENT-TOPO], which augments the TE
Topology Model
The Ethernet Topology Model is used to report the access links
between the IP routers and the edge ROADMs as well as the
inter-domain links between ASBRs, while the L3 Topology Model is
used to report the IP network topology (e.g., IP routers and links).
3.2. Inter-domain link Discovery
In the reference network of Figure 1, there are two types of
inter-domain links:
o Links between two IP domains (ASes)
o Links between an IP router and a ROADM
Both types of links are Ethernet physical links.
The inter-domain link information is reported to the MDSC by the two
adjacent PNCs, controlling the two ends of the inter-domain link.
The MDSC can understand how to merge these inter-domain links
together using the plug-id attribute defined in the TE Topology
Model [TE-TOPO], as described in as described in section 4.3 of [TE-
TOPO].
A more detailed description of how the plug-id can be used to
discover inter-domain link is also provided in section 5.1.4 of
[TNBI].
Both types of inter-domain links are discovered using the plug-id
attributes reported in the Ethernet Topologies exposed by the two
adjacent PNCs. The MDSC can also discover an inter-domain IP
link/adjacency between the two IP LTPs, reported in the IP
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Topologies exposed by the two adjacent P-PNCs, supported by the two
ETH LTPs of an Ethernet Link discovered between these two P-PNCs.
Two options are possible to discover these inter-domain links:
1. Static configuration
2. LLDP [IEEE 802.1AB] automatic discovery
Since the static configuration requires an administrative burden to
configure network-wide unique identifiers, the automatic discovery
solution based on LLDP is preferable when LLDP is supported.
As outlined in [TNBI], the encoding of the plug-id namespace as well
as of the LLDP information within the plug-id value is
implementation specific and needs to be consistent across all the
PNCs.
4. Scenario 2 - Provisioning of an IP Link over DWDM
In this scenario, the MSDC needs to coordinate the creation of an IP
link, or a LAG, between two routers through a DWDM network.
It is assumed that the MDSC has already discovered the whole network
topology as described in section 3.
4.1. YANG models used at the MPIs
4.1.1. YANG models used at the Optical MPIs
The Optical PNC uses at least the following YANG models:
o The TE Tunnel Model, defined in the "ietf-te" YANG module of
[TE-TUNNEL]
o The WSON Tunnel Model, defined in the "ietf-wson-tunnel" YANG
modules of [WSON-TUNNEL], or the Flexi-grid Media Channel Model,
defined in the "ietf-flexi-grid-media-channel" YANG module of
[Flexi-MC]
o The Ethernet Client Signal Model, defined in the "ietf-eth-tran-
service" YANG module of [CLIENT-SIGNAL]
The TE Tunnel model is generic and augmented by technology-specific
models such as the WSON Tunnel Model and the Flexi-grid Media
Channel Model.
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The WSON Tunnel Model or, alternatively, the Flexi-grid Media
Channel Model are used to setup connectivity within the DWDM network
depending on whether the DWDM optical network is based on fixed grid
or flexible-grid.
The Ethernet Client Signal Model is used to configure the steering
of the Ethernet client traffic between Ethernet access links and TE
Tunnels, which in this case could be either WSON Tunnels or
Flexi-Grid Media Channels. This model is generic and applies to any
technology-specific TE Tunnel: technology-specific attributes are
provided by the technology-specific models which augment the generic
TE-Tunnel Model.
4.1.2. Required YANG models at the Packet MPIs
The Packet PNC uses at least the following topology YANG models:
o The Base Network Model, defined in the "ietf-network" YANG module
of [RFC8345] (see section 3.1)
o The Base Network Topology Model, defined in the "ietf-network-
topology" YANG module of [RFC8345] (see section 3.1)
o The L3 Topology Model, defined in the "ietf-l3-unicast-topology"
YANG modules of [RFC8346] (see section 3.1.1)
If, as discussed in section 4.2, IP Links created over DWDM can be
automatically discovered by the P-PNC, the IP Topology is needed
only to report these IP Links after being discovered by the P-PNC.
The IP Topology can also be used to configure the IP Links created
over DWDM.
4.2. IP Link Setup Procedure
The MDSC requires the O-PNC to setup a WDM Tunnel (either a WSON
Tunnel or a Flexi-grid Tunnel) within the DWDM network between the
two Optical Transponders (OTs) associated with the two access links.
The Optical Transponders are reported by the O-PNC as Trail
Termination Points (TTPs), defined in [TE-TOPO], within the WDM
Topology. The association between the Ethernet access link and the
WDM TTP is reported by the Inter-Layer Lock (ILL) identifiers,
defined in [TE-TOPO], reported by the O-PNC within the Ethernet
Topology and WDM Topology.
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The MDSC also requires the O-PNC to steer the Ethernet client
traffic between the two access Ethernet Links over the WDM Tunnel.
After the WDM Tunnel has been setup and the client traffic steering
configured, the two IP routers can exchange Ethernet packets between
themselves, including LLDP messages.
If LLDP [IEEE 802.1AB] is used between the two routers, the P-PNC
can automatically discover the IP Link being setup by the MDSC. The
IP LTPs terminating this IP Link are supported by the ETH LTPs
terminating the two access links.
Otherwise, the MDSC needs to require the P-PNC to configure an IP
Link between the two routers: the MDSC also configures the two ETH
LTPs which support the two IP LTPs terminating this IP Link.
5. Security Considerations
Several security considerations have been identified and will be
discussed in future versions of this document.
6. Operational Considerations
Telemetry data, such as the collection of lower-layer networking
health and consideration of network and service performance from POI
domain controllers, may be required. These requirements and
capabilities will be discussed in future versions of this document.
7. IANA Considerations
This document requires no IANA actions.
8. References
8.1. Normative References
[RFC7950] Bjorklund, M. et al., "The YANG 1.1 Data Modeling
Language", RFC 7950, August 2016.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC
7951, August 2016.
[RFC8040] Bierman, A. et al., "RESTCONF Protocol", RFC 8040, January
2017.
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[RFC8345] Clemm, A., Medved, J. et al., "A Yang Data Model for
Network Topologies", RFC8345, March 2018.
[RFC8346] Clemm, A. et al., "A YANG Data Model for Layer 3
Topologies", RFC8346, March 2018.
[RFC8453] Ceccarelli, D., Lee, Y. et al., "Framework for Abstraction
and Control of TE Networks (ACTN)", RFC8453, August 2018.
[RFC8525] Bierman, A. et al., "YANG Library", RFC 8525, March 2019.
[IEEE 802.1AB] IEEE 802.1AB-2016, "IEEE Standard for Local and
metropolitan area networks - Station and Media Access
Control Connectivity Discovery", March 2016.
[TE-TOPO] Liu, X. et al., "YANG Data Model for TE Topologies",
draft-ietf-teas-yang-te-topo, work in progress.
[WSON-TOPO] Lee, Y. et al., " A YANG Data Model for WSON (Wavelength
Switched Optical Networks)", draft-ietf-ccamp-wson-yang,
work in progress.
[Flexi-TOPO] Lopez de Vergara, J. E. et al., "YANG data model for
Flexi-Grid Optical Networks", draft-ietf-ccamp-flexigrid-
yang, work in progress.
[CLIENT-TOPO] Zheng, H. et al., "A YANG Data Model for Client-layer
Topology", draft-zheng-ccamp-client-topo-yang, work in
progress.
[TE-TUNNEL] Saad, T. et al., "A YANG Data Model for Traffic
Engineering Tunnels and Interfaces", draft-ietf-teas-yang-
te, work in progress.
[WSON-TUNNEL] Lee, Y. et al., "A Yang Data Model for WSON Tunnel",
draft-ietf-ccamp-wson-tunnel-model, work in progress.
[Flexi-MC] Lopez de Vergara, J. E. et al., "YANG data model for
Flexi-Grid media-channels", draft-ietf-ccamp-flexigrid-
media-channel-yang, work in progress.
[CLIENT-SIGNAL] Zheng, H. et al., "A YANG Data Model for Transport
Network Client Signals", draft-ietf-ccamp-client-signal-
yang, work in progress.
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8.2. Informative References
[TNBI] Busi, I., Daniel, K. et al., "Transport Northbound
Interface Applicability Statement", draft-ietf-ccamp-
transport-nbi-app-statement, work in progress.
9. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
Some of this analysis work was supported in part by the European
Commission funded H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727).
10. Authors' Addresses
Fabio Peruzzini
TIM
Email: fabio.peruzzini@telecomitalia.it
Daniel King
Old Dog Consulting
Email: daniel@olddog.co.uk
Zheng Yanlei
China Unicom
Email: zhengyanlei@chinaunicom.cn
Gabriele Galimberti
Cisco
Email: ggalimbe@cisco.com
Washington Costa Pereira Correia
TIM Brasil
Email: wcorreia@timbrasil.com.br
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