CCAMP Working Group I. Busi (Ed.)
Internet-Draft Huawei
Intended status: Informational D. King (Ed.)
Expires: August, 2017 Lancaster University
February 7, 2017
A Service YANG Model for Connection-oriented Transport Networks
draft-tnbidt-ccamp-transport-nbi-use-cases-00
Abstract
Transport network domains, including Optical Transport Network (OTN)
and Wavelength Division Multiplexing (WDM) networks, are typically
deployed based on a single vendor or technology platforms. They are
often managed using proprietary interfaces to dedicated Element
Management Systems (EMS), Network Management Systems (NMS) and
increasingly Software Defined Network (SDN) controllers.
A well-defined open interface to each domain management system or
controller is required for network operators to facilitate control
automation and orchestrate end-to-end services across multi-domain
networks. These functions may enabled using standardized data models
(e.g. YANG), and appropriate protocol (e.g., RESTCONF).
This document describes the key use cases and requirements for
transport network control and management. It reviews proposed and
existing IETF transport network data models, their applicability,
and highlights gaps and requirements.
Status of This Memo
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This Internet-Draft will expire on August 7, 2017.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. This document is subject
to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF
Documents (http://trustee.ietf.org/license-info) in effect on the
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to this document.
Table of Contents
1. Introduction.................................................2
2. Conventions used in this document............................3
3. Use Case 1: Single-domain with single-layer..................3
3.1. Reference Network.......................................3
3.1.1. Single Transport Domain - OTN Network..............3
3.1.2. Single Domain - ROADM Network......................3
3.2. Topology Abstractions...................................6
3.3. Service Configuration...................................7
3.3.1. ODU Transit........................................7
3.3.2. EPL over ODU.......................................8
3.3.3. Other OTN Client Services..........................8
3.3.4. EVPL over ODU......................................9
3.3.5. EVPLAN and EVPTree Services........................9
3.3.6. Virtual Network Services...........................9
3.4. Multi-functional Access Links...........................9
4. Use Case 2: Single-domain with multi-layer...................9
5. Use Case 3: Multi-domain with single-layer...................9
6. Use Case 4: Multi-domain and multi-layer.....................9
7. Security Considerations......................................9
8. IANA Considerations..........................................9
9. References...................................................9
9.1. Normative References....................................10
9.2. Informative References..................................10
10. Acknowledgments.............................................10
Authors' Addresses..............................................11
1. Introduction
A common open interface to each domain controller/management system
is pre-requisite for network operators to control multi-vendor and
multi-domain networks and enable also service provisioning
coordination/automation. This can be achieved by using standardized
YANG models, used together with an appropriate protocol (e.g.,
RESTCONF).
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This document assumes a reference architecture, including interfaces,
based on the Abstraction and Control of Traffic-Engineered Networks
(ACTN), defined in [ACTN-Frame].
The focus of the current version is on the MPI (interface between
the Multi Domain Service Coordinator (MDSC) and a Physical Network
Controller (PNC), controlling a transport network domain).
The relationship between the current IETF YANG models and the type of
ACTN interfaces can be found in [ACTN-YANG].
The ONF Technical Recommendations for Functional Requirements
for the transport API, may be found in [ONF TR-527].
Furthermore, ONF transport API multi-layer examples may be
found in [ONF GitHub].
This document describes use cases that could be used for analyzing
the applicability of the existing models defined by the IETF for
transport networks
Considerations about the CMI (interface between the Customer Network
Controller (CNC) and the MDSC) are for further study.
2. Conventions used in this document
For discussion in future revisions of this document.
3. Use Case 1: Single-domain with single-layer
3.1. Reference Network
The current considerations discussed in this document are
based on the following reference networks:
- single transport domain: OTN network
It is expected that future revisions of the document will
include additional reference networks.
3.1.1. Single Transport Domain - OTN Network
Figure 1 shows the network physical topology composed of a
single-domain transport network providing transport services to an
IP network through five access links.
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................................................
: IP domain :
: .............................. :
: : ........................ : :
: : : : : :
: : : S1 -------- S2 ------ C-R4 :
: : : / | : : :
: : : / | : : :
: C-R1 ------ S3 ----- S4 | : : :
: : : \ \ | : : :
: : : \ \ | : : :
: : : S5 \ | : : :
: C-R2 -----+ / \ \ | : : :
: : : \ / \ \ | : : :
: : : S6 ---- S7 ---- S8 ------ C-R5 :
: : : / : : :
: C-R3 -----+ : : :
: : : Transport domain : : :
: : : : : :
:........: :......................: :........:
Figure 1 Reference network for Use Case 1
The IP and transport (OTN) domains are respectively composed by five
routers C-R1 to C-R5 and by eight ODU switches S1 to S8. The
transport domain acts as a transit domain providing connectivity to
the IP layer.
The behavior of the transport domain is the same whether the
ingress/egress nodes in the IP domain, supporting an IP service, are
directly attached to the transport domain or there are other routers
in between the ingress/egress nodes of the IP domain and the routers
directly attached to the transport network.
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+-----+
| CNC |
+-----+
|
|CMI I/F
|
+-----------------------+
| MDSC |
+-----------------------+
|
|MPI I/F
|
+-------+
| PNC |
+-------+
|
-----
( )
( OTN )
( Physical )
( Network )
( )
-----
Figure 2 Controlling Hierarchy for Use Case 1
The mapping of the client IP traffic on the physical link between the
routers and the transport network is made in the IP routers only and
is not controlled by the transport PNC and is transparent to the
transport nodes.
The control plane architecture follows the ACTN architecture and
framework document [ACTN-Frame]. The Client Controller act as a
client with respect to the Multi-Domain Service Coordinator (MDSC)
via the Controller-MDSC Interface (CMI). The MDSC is connected to a
plurality of Physical Network Controllers (PNCs), one for each
domain, via a MDSC-PNC Interface (MPI). Each PNC is responsible
only for the control of its domain and the MDSC is the only entity
capable of multi-domain functionalities as well as of managing the
inter-domain links. The key point of the whole ACTN framework is
detaching the network and service control from the underlying
technology and help the customer express the network as desired
by business needs. Therefore care must be taken to keep minimal
dependency on the CMI (or no dependency at all) with respect to
the network domain technologies. The MPI instead requires some
specialization according to the domain technology.
In this section, we address the case of an IP and a Transport PNC
having respectively an IP a Transport MPI. The interface within
the scope of this document is the Transport MPI while the IP
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Network MPI is out of its scope and considerations about the CMI
are for further study.
3.2. Topology Abstractions
Abstraction is defined in [RFC7926] as:
Abstraction is the process of applying policy to the available TE
information within a domain, to produce selective information that
represents the potential ability to connect across the domain.
Thus, abstraction does not necessarily offer all possible
connectivity options, but presents a general view of potential
connectivity according to the policies that determine how the
domain's administrator wants to allow the domain resources to be
used.
[TE-Topo] describes YANG models for TE-network abstraction.
[ACTN-Abstraction] provides the context of topology abstraction in
the ACTN architecture and discusses a few alternatives for the
methods of abstraction for both packet and optical networks. This
is an important consideration since the choice of the abstraction
method impacts protocol design and the information it carries.
According to [ACTN-Abstraction], there are three types of topology:
o White topology: This is a case where the PNC provides the actual
network topology to the MDSC without any hiding or filtering. In
this case, the MDSC has the full knowledge of the underlying
network topology and as such there is no need for the MDSC to
send a path computation request to the PNC. The computation
burden will fall on the MDSC to find an optimal end-to-end path
and optimal per domain paths.
o Black topology: The entire domain network is abstracted as a
single virtual node with the access/egress links without
disclosing any node internal connectivity information.
o Grey topology: This abstraction level is between black topology
and white topology from a granularity point of view. This is
basically abstraction of TE tunnels for all pairs of border
nodes.
We may further differentiate from a perspective of how to
abstract internal TE resources between the pairs of border nodes:
- Grey topology type A: border nodes with a TE links between
them in a full mesh fashion.
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- Grey topology type B: border nodes with some internal
abstracted nodes and abstracted links.
For single-domain with single-layer use-case, the white topology may
be disseminated from the PNC to the MDSC in most cases. There may be
some exception to this in the case where the underlay network may
have complex optical parameters which do not warrant the distribution
of such details to the MDSC. In such case, the topology disseminated
from the PNC to the MDSC may not have the entire TE information but a
streamlined TE information. This case would incur another action from
the MDSC's standpoint when provisioning a path.
The MDSC may make a path compute request to the PNC in order to
verify the feasibility of the estimated path before making the final
provisioning request to the PNC, as outlined in [Path-Compute].
Topology abstraction for the CMI is for further study (to be
addressed in future revisions of this document).
3.3. Service Configuration
In the following use cases, the Multi Domain Service Coordinator
(MDSC) needs to be capable to request service connectivity from the
transport Physical Network Controller (PNC) to support IP routers
connectivity. The type of services could depend of the type of
physical links (e.g. OTN link, ETH link or SDH link) between the
routers and transport network.
As described in section 3.1.1, the control of different adaptations
inside IP routers, C-Ri (PKT -> foo) and C-Rj (foo -> PKT), are
assumed to be performed by means that are not under the control of,
and not visible to, transport PNC. Therefore, these mechanisms are
outside the scope of this document.
3.3.1. ODU Transit
This use case assumes that the physical link interconnecting IP
routers and transport network is an OTN link.
The physical/optical interconnection is supposed to be a
pre-configured and not exposed via MPI to MDSC.
If we consider the case of a 10Gb IP link between C-R1 to C-R3,
we need to instantiate an ODU2 end-to-end connection between C-R1
and C-R3, crossing transport nodes S3, S5, and S6.
The traffic flow between C-R1 and C-R3 can be summarized as:
C-R1 (PKT -> ODU2), S3 (ODU2), S5 (ODU2), S6 (ODU2),
C-R3 (ODU2 -> PKT)
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The MDSC should be capable via MPI i/f to request the setup of ODU2
transit service with enough information that can permit transport
PNC to instantiate and control the ODU2 segment through nodes S3,
S5, S6.
3.3.2. EPL over ODU
This use case assumes that the physical link interconnecting IP
routers and transport network is an Ethernet link.
If we consider the case of a 10Gb IP link between C-R1 to C-R3, we
need to instantiate an EPL service between C-R1 and C-R3 supported
by an ODU2 end-to-end connection between S3 and S6, crossing
transport node S5.
The traffic flow between C-R1 and C-R3 can be summarized as:
C-R1 (PKT -> ETH), S3 (ETH -> ODU2), S5 (ODU2),
S6 (ODU2 -> ETH), C-R3 (ETH-> PKT)
The MDSC should be capable via MPI i/f to request the setup of EPL
service with enough information that can permit transport PNC to
instantiate and control the ODU2 end-to-end connection through nodes
S3, S5, S6, as well as the adaptation functions inside S3 and S6:
S3&S6 (ETH -> ODU2) and S9&S6 (ODU2 -> ETH).
3.3.3. Other OTN Client Services
[ITU-T G.709-2016] defines mappings of different client layers into
ODU. Most of them are used to provide Private Line services over
an OTN transport network supporting a variety of types of physical
access links (e.g., Ethernet, SDH STM-N, Fibre Channel,
InfiniBand,).
This use case assumes that the physical links interconnecting IP
routers and transport network are any one of these possible
options.
If we consider the case of a 10Gb IP link between C-R1 to C-R3
using SDH physical links, we need to instantiate an STM-64 Private
Line service between C-R1 and C-R3 supported by an ODU2 end-to-end
connection between S3 and S6, crossing transport node S5.
The traffic flow between C-R1 and C-R3 can be summarized as:
C-R1 (PKT -> STM-64), S3 (STM-64 -> ODU2), S5 (ODU2),
S6 (ODU2 -> STM-64), C-R3 (STM-64 -> PKT)
The MDSC should be capable via MPI i/f to request the setup of an
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STM-64 Private Line service with enough information that can permit
transport PNC to instantiate and control the ODU2 end-to-end
connection through nodes S3, S5, S6, as well as the adaptation
functions inside S3 and S6: S3&S6 (STM-64 -> ODU2) and S9&S3
(STM-64 -> PKT).
3.3.4. EVPL over ODU
For future revision.
3.3.5. EVPLAN and EVPTree Services
For future revision.
3.3.6. Virtual Network Services
For future revision
3.4. Multi-functional Access Links
For future revision
4. Use Case 2: Single-domain with multi-layer
For future revision
5. Use Case 3: Multi-domain with single-layer
For future revision
6. Use Case 4: Multi-domain and multi-layer
For future revision
7. Security Considerations
For further study
8. IANA Considerations
This document requires no IANA actions.
9. References
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9.1. Normative References
[RFC7926] Farrel, A. et al., "Problem Statement and Architecture for
Information Exchange between Interconnected Traffic-Engineered
Networks", BCP 206, RFC 7926, July 2016.
[ITU-T G.709-2016] ITU-T Recommendation G.709 (06/16), "Interfaces
for the optical transport network", June 2016.
[ACTN-Frame] Ceccarelli, D., Lee, Y. et al., "Framework for
Abstraction and Control of Transport Networks",
draft-ietf-teas-actn-framework, work in progress.
[ACTN-Abstraction] Lee, Y. et al., " Abstraction and Control of
TE Networks (ACTN) Abstraction Methods",
draft-lee-teas-actn-abstraction, work in progress.
9.2. Informative References
[TE-Topo] Liu, X. et al., "YANG Data Model for TE Topologies",
draft-ietf-teas-yang-te-topo, work in progress.
[ACTN-YANG] Zhang, X. et al., "Applicability of YANG models for
Abstraction and Control of Traffic Engineered Networks",
draft-zhang-teas-actn-yang, work in progress.
[Path-Compute] Busi, I., Belotti, S. et al., " Yang model for
requesting Path Computation", draft-busibel-teas-yang-path-
computation, work in progress.
[ONF TR-527] ONF Technical Recommendation TR-527, "Functional
Requirements for Transport API", June 2016
[ONF GitHub] ONF Open Transport (SNOWMASS)
https://github.com/OpenNetworkingFoundation/Snowmass-
ONFOpenTransport
10. Acknowledgments
The authors would like to thank all members of the Transport NBI
Design Team involved in the definition of use cases, gap analysis
and guidelines for using the IETF YANG models at the Northbound
Interface (NBI) of a Transport SDN Controller.
The authors would like to thank Xian Zhang, Anurag Sharma, Michael
Scharf, Karthik Sethuraman, Oscar Gonzalez de Dios, Tara Cummings
and Hans Bjursrom, for having initiated work on gap analysis for
transport NBI and having provided foundations work for the
development of this document.
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Authors' Addresses
Italo Busi (Editor)
Huawei
Email: italo.busi@huawei.com
Daniel King (Editor)
Lancaster University
Email: d.king@lancaster.ac.uk
Sergio Belotti
Nokia
Email: sergio.belotti@nokia.com
Gianmarco Bruno
Ericsson
Email: gianmarco.bruno@ericsson.com
Young Lee
Huawei
Email: leeyoung@huawei.com
Victor Lopez
Telefonica
Email: victor.lopezalvarez@telefonica.com
Carlo Perocchio
Ericsson
Email: carlo.perocchio@ericsson.com
Haomian Zheng
Huawei
Email: zhenghaomian@huawei.com
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