Internet DRAFT - draft-sambo-ccamp-yang-fsm-transponder-reconf
draft-sambo-ccamp-yang-fsm-transponder-reconf
CCAMP Working Group N. Sambo
Internet-Draft P. Castoldi
Intended status: Standards Track A. Sgambelluri
Expires: April 25, 2019 Scuola Superiore Sant'Anna
G. Fioccola
Huawei Technologies
F. Cugini
CNIT
D. Ceccarelli
Ericsson
H. Song
T. Zhou
Huawei
October 22, 2018
Finite state machine YANG model augmentation for Transponder
Reconfiguration
draft-sambo-ccamp-yang-fsm-transponder-reconf-02
Abstract
YANG enables to compile a set of consistent vendor-neutral data
models for optical networks and components based on actual
operational needs emerging from heterogeneous use cases. A YANG
model has been also proposed to describe finite state machine to
program network elements that are modeled with YANG. This document
augments the more generic YANG model for finite state machine
[I-D.sambo-netmod-yang-fsm], in order to pre-instruct an optical
transponder on the actions to be performed (e.g., code adaptation) in
case some events, such as physical layer degradations, occur.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 25, 2019.
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Copyright Notice
Copyright (c) 2018 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Flexible Transponders . . . . . . . . . . . . . . . . . . . . 4
5. Augmenting the FSM YANG model for transponder reconfiguration 7
6. Code of the YANG model for transponder reconfiguration . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
Networks are evolving toward more programmability, flexibility, and
multi-vendor interoperability. Multi-vendor interoperability can be
applied in the context of nodes, i.e. a node composed of components
provided by different vendors (named fully disaggregated white box)
is assembled under the same control system. This way, operators can
optimize costs and network performance without the need of being tied
to single vendor equipment. NETCONF protocol RFC6241 [RFC6241] based
on YANG data modeling language RFC6020 [RFC6020] is emerging as a
candidate Software Defined Networking (SDN) enabled protocol. First,
NETCONF supports both control and management functionalities, thus
permits high programmability. Then, YANG enables data modeling in a
vendor-neutral way. Some recent works have provided YANG models to
describe attributes of links (e.g., identification), nodes (e.g.,
connectivity matrix), media channels, and transponders (e.g.,
supported forward error correction - FEC) of networks
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([I-D.ietf-i2rs-yang-network-topo] [I-D.vergara-ccamp-flexigrid-yang]
[I-D.zhang-ccamp-l1-topo-yang]), also including optical technologies.
A YANG model [I-D.sambo-netmod-yang-fsm] has been also proposed to
describe finite state machines (FSMs) in order to program actions
based on conditions and events in YANG-described devices. Such draft
mainly refers to elastic optical networks (EONs), i.e. optical
networks based on flexible grid where circuits with different
bandwidth requirements are switched. EONs are expected to employ
flexible transponders, i.e. transponders supporting multiple bit
rates, multiple modulation formats, and multiple codes. Such
transponders permits the (re-) configuration of the bit rate value
based on traffic requirements, as well as the configuration of the
modulation format and code based on the physical characteristics of a
path (e.g., quadrature phase shift keying is more robust than 16
quadrature amplitude modulation). This document augments the YANG
model for FSM [I-D.sambo-netmod-yang-fsm] to be applied in
programming reconfiguration of transponders in EONs based on physical
layer conditions. In particular, the model enables a centralized
remote network controller (managed by a network operator) to instruct
a transponder controller about the actions to perform when certain
events (e.g., failures) occur. The actions to be taken and the
events can be re-programmed on the device.
2. 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 RFC2119 [RFC2119].
3. Terminology
ABNO: Application-Based Network Operations
BER: Bit Error Rate
EON: Elastic Optical Network
FEC: Forward Error Correction
FSM: Finite State Machine
NETCONF: Network Configuration Protocol
OAM: Operation Administration and Maintenance
SDN: Software Defined Network
YANG: Yet Another Network Generator
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4. Flexible Transponders
Flexible transponders enable several parameters' configurations,
through the support of multiple modulation formats, baud rate, and
forward error correction (FEC) schemes. This way, transmission
parameters can be (re-)configured based on the physical layer
conditions. The YANG model presented in this draft enables to pre-
program reconfiguration settings of data plane devices in case of
changes in the physical layer conditions. In particular, soft
failures can be assumed. Soft failures imply transmission
performance degradation, in turns a bit error rate (BER) increase,
e.g. due to the ageing of some network devices. Without loosing
generality, the ABNO architecture is assumed for the control and
management of EONs (RFC7491 [RFC7491]). Considering the state of the
art, when pre-FEC BER passes above a predefined threshold, it is
expected that an alarm is sent to the OAM Handler, which communicates
with the ABNO controller that may trigger an SDN controller (that
could be the Provisioning Manager of ABNO RFC7491 [RFC7491]) for
computing new transmission parameters. The involved ABNO modules are
shown in the simplified ABNO architecture of Fig. 1. Then,
transponders are reconfigured. When alarms related to several
connections impacted by the soft failure are generated, this
procedure may be particularly time consuming. The related workflow
for transponder reconfiguration is shown in Fig. 2. The proposed
model enables an SDN controller to instruct the transponder about
reconfiguration of new transmission parameters values if a soft
failure occurs. This can be done before the failure occurs (e.g.,
during the connection instantiation phase or during the connection
service), so that data plane devices can promptly reconfigure
themselves without querying the SDN controller to trigger an on-
demand recovery. This is expected to speed up the recovery process
from soft failures. The related flow chart is shown in Fig. 3.
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___________ ___________
| ABNO | | OAM |
|controller | ------ | Handler |
|___________| |___________|
| |
| |
| |
____________ |
| SDN | |
| controller | |
|____________| |
|
| |
| |
| |
_____________________________
| Client |
| network |
|_____________________________|
Figure 1: Assumed ABNO functional modules
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_____________________
| 1 |
|Sending alarm to the |
| OAM Handler |
| |
|_____________________|
|
|
|
_____________________
| 2 |
| Trigger |
| SDN Controller |
| |
|_____________________|
|
|
|
_____________________
| 3 |
| Computation of |
| new transmission |
| parameters |
|_____________________|
|
|
|
_____________________
| 4 |
| Data plane |
| reconfiguration |
| |
|_____________________|
Figure 2: Flow chart of the expected state-of-the-art approach
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_______________________
| 1 |
| Instructing the local |
| controller of |
| data plane devices |
|_______________________|
|
|
|
_______________________
| 2 |
| Local reconfiguration |
| upon failure |
| detection |
|_______________________|
|
|
|
_______________________
| 3 |
| |
| notification |
| |
|_______________________|
Figure 3: Flow chart of the approach exploiting YANG models in this
draft
5. Augmenting the FSM YANG model for transponder reconfiguration
This section augments the FSM YANG model presented in
[I-D.sambo-netmod-yang-fsm] to address the specific use case of
transponder reconfiguration triggered by physical layer changes. The
FSM is installed by the SDN controller in the local controller of the
transponder and then runs there. The installation of the FSM can be
enabled through a NETCONF <edit-config> message. Through FSM, the
SDN controller instructs the transponder about the possible events
(e.g., BER above a threshold) and reactions (e.g., change of
modulation format) by setting the thresholds (e.g., BER threshold)
and the reconfiguration settings. The FSM model is based on the
following main attributes: states, transitions (corresponding to some
specific event), and actions. In particular, more specifically with
respect to [I-D.sambo-netmod-yang-fsm], in such a use case, a state
corresponds to a specific configuration of transponder transmission
parameters: e.g., given by the modulation format and the FEC. A
transition is triggered when the pre-FEC BER (or another parameter
such as the OSNR) is below or above a threshold. To this purpose,
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with respect to [I-D.sambo-netmod-yang-fsm], the attribute <filter>
is expressed by the definition of thresholds and operators. The
action mainly consists of the change of modulation format and/or FEC.
The Tree of the YANG model for transponder reconfiguration
(augmentation of the YANG model for FSM) is reported below.
module: ietf-treconf
+--rw current-state? leafref
+--rw states
+--rw state [id]
+--rw id state-id-type
+--rw description? string
+--rw transitions
+--rw transition [name]
+--rw name string
+--rw description? string
+--rw threshold-parameter? decimal64
+--rw threshold-operator? string
+--rw transition-action
+--rw action [id]
+--rw id transition-id-type
+--rw type enumeration
+--rw simple
+--rw execute
+--rw next-action? transition-id-type
+--rw next-state? Leafref
More specifically, the attribute <state> is a list defining all the
transponder states. <transitions> is an attribute defining a list of
events that may trigger the change of transponder state (e.g., BER
change). <threshold-parameter> defines a threshold value, while
<threshold-operator> defines the operator <,>,<=,>=. Thus, if the
event BER>TH has to be modeled, the attribute <threshold-parameter>
has to be set to "TH" while <threshold-operator> to ">". <actions>
defines a list of actions to take during the transition (e.g. change
of modulation format) <next-state> defines the next transponder state
when an action is executed (e.g., new modulation format and FEC).
For more details about the other model attributes, the reader can
refer to [I-D.sambo-netmod-yang-fsm].
In such a use case, we assume that an event (e.g., BER>TH) is
revealed by the digital signal processing (DSP) of the receiver.
Once the event is recognized, the modulation format and/or the FEC
have to be changed, both at the receiver and the transmitter. Thus,
the list of actions to be executed includes the change of
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transmission parameters at the receiver side. Moreover, transmission
and receiver must be synchronized about the transmission settings
(modulation format and so no) for a proper transmission. Thus, when
the transponder at the receiver side decides to change its state, the
remote transponder at the transmitter side has to do the same state
transition. To this purpose, the list of actions also includes this
coordination. In particular, the transponder at the receiver side
sends a message to the transmitter to synchronize about the
transmission parameters to be adopted. This message can be sent over
a control channel. This way both the transmitter and receiver
operates with the same transmission parameters: e.g. the format,
FEC, and so on.
Such transponder reconfiguration based on FSM has been successfully
demonstrated by integrating control and data planes in a lab and
field trials.
Finally, a last consideration concerns the impact on transmission bit
rate when changing some transmission parameters. When passing from a
more spectral efficient modulation format (but less robust with
respect to physical impairments) to a less spectral efficient
modulation format (more robust) such that could be polarization
multiplexing 16 quadrature phase shift keying (PM-16QAM) and PM
quadrature phase shift keying (PM-QPSK) the bit rate is reduced
(halved in the case of PM-16QAM and PM-QPSK). This means that part
of the traffic cannot be recovered through FSM, but needs of other
restoration mechanisms (e.g., dynamic restoration). As an example,
the gain of the proposed FSM mechanism promptly recovering part of
the bit rate can be applied to high-priority traffic so that its
recovery can be faster without involving central controller, while
other classical recovery mechanisms (involving the sending of alarms,
their processing, new computations and setup) can be adopted for best
effort traffic (as the traffic that cannot be recovered when passing
from PM-16QAM to PM-QPSK). The same happens changing the code rate:
at fixed baud rate and modulation format, if the code redundancy is
increased, the net bit rate is decreased. Again, part of the traffic
can be promptly recovered through FSM, while the other by relying on
classical recovery mechanisms. Another case of applicability is
related to the "functional split" in next generation radio access
networks (RANs). In this scenario, the evolved NodeB (eNB) functions
are split into two new, most likely virtualized, network entities:
the Central Unit (CU) deployed in centralized locations and the
Distributed Unit (DU) deployed near the antenna. Several functional
splits are being considered, e.g. by 3GPP in TR 38.801 and IEEE 1914
Working Group in Next Generation Fronthaul Interface (NGFI). They
demand different requirements in terms of latency and capacity to the
fronthaul network connecting DU and CU. For example, in 3GPP TR
38.801, according to "Option 7c" functional split, 10.1-22.2Gb/s and
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53.8-86.1Gb/s are required in the downstream and upstream links,
respectively, while, according to "Option 8" functional split,
157.3Gb/s is required both in downstream and upstream links. Thus,
the change of rate could reflect into a change of functional split.
6. Code of the YANG model for transponder reconfiguration
The related code is reported below.
<CODE BEGINS> file "ietf-treconf@2016-03-15.yang"
module ietf-treconf {
namespace "http://sssup.it/fsm";
prefix fsm;
organization
"Scuola Superiore Sant'Anna Network and Services Laboratory";
contact
" Editor: Matteo Dallaglio
<mailto:m.dallaglio@sssup.it>
";
description
"This module contains a YANG definitions of a generic finite state
machine.";
revision 2016-03-15 {
description "Initial Revision.";
reference
"RFC xxxx:";
}
identity TRANSITION {
description "Base for all types of event";
}
identity ON_CHANGE {
base TRANSITION;
description
"The event when the database changes.";
}
// typedef statements
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typedef transition-type {
description "it defines the transition type";
type identityref {
base TRANSITION;
}
}
typedef transition-id-type {
description "it defines the transition id type";
type uint32;
}
// grouping statements
grouping action-block {
description "it defines the grouping action";
leaf id {
description "it defines the id of the transition";
type transition-id-type;
}
leaf type {
description "it defines if the action has to be simply executed
or if a conditional statement has to be checked before execution";
type enumeration {
enum "CONDITIONAL_OP"{
description "it defines the type CONDITIONAL OPERATION to check a
statement before execution. In this draft, at the moment, only SIMPLE
will be assumed";
}
enum "SIMPLE_OP"{
description "it defines the type SIMPLE OPERATION: i.e., an operation
to be directly executed;
}
}
mandatory true;
}
grouping execution-top {
description "it defines the execution attribute";
anyxml execute {
description "Represent the action to perform";
}
leaf next-action {
type transition-id-type;
description "the id of the next action to execute";
}
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}
container simple {
when "../type = 'SIMPLE_OP'";
description
"Simple execution of an action without checking any condition";
uses execution-top;
}
}
grouping action-top {
description "it defines the grouping of action";
list action {
description "it defines the list of actions";
key "id";
ordered-by user;
uses action-block;
}
}
grouping on-change {
description
"Event occuring when a modification of one or more
objects occurs";
leaf threshold-parameter {
description "it defines the threshold of an event determined by
a threshold exceed";
type decimal64;
}
leaf threshold-operator {
description "it defines the operator to check the threshold
exceed: <, > <=, >=";
type string;
}
}
grouping transition-top {
description "it defines the grouping transition";
leaf name {
description "it defines the transition name";
type string;
mandatory true;
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}
leaf description {
description "it describes the transition with a string";
type string;
}
// list of all possible events
uses on-change {
when "type = 'ON_CHANGE'";
}
container transition-action {
description "it defines the container actions to take during the
transition";
uses action-top;
}
}
grouping transitions-top {
description "it defines the grouping transition";
container transitions {
description "it defines the container transitions";
list transition {
description "it defines the list of transitions";
key "name";
uses transition-top;
}
}
}
// data definition statements
uses transitions-top;
// extension statements
// feature statements
// augment statements
// rpc statements
// notification statements
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// identity statements
// typedef statements
typedef state-id-type {
description "it defines the id type of the states";
type uint32;
}
// grouping statements
grouping state-top {
description "it defines the grouping state";
leaf id {
description "it defines the id of the state";
type state-id-type;
}
leaf description {
description "it describes the state with a string";
type string;
}
grouping next-state-top {
description "it defines the grouping next state";
leaf next-state {
type leafref {
path "../../../../../../../../../states/state/id";
}
description "Id of the next state";
}
}
uses transitions-top {
augment "transitions/transition/transition-action/action/simple" {
//uses next-state-top;
leaf next-state {
type leafref {
path "../../../../../../../../states/state/id";
}
description "Id of the next state";
}
}
}
}
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grouping states-top {
description "it defines the attributes of state-top";
leaf current-state {
description "it defines the current state";
type leafref {
description "it refers to its id";
path "../states/state/id";
}
}
container states {
description "it defines the container states";
list state {
description "it defines the list of states";
key "id";
uses state-top;
}
}
}
// data definition statements
uses states-top;
// extension statements
// feature statements
// augment statements.
// rpc statements
// notification statements
}//module fsm
<CODE ENDS>
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7. Acknowledgements
This work has been partially supported by the European Commission
through the EU H2020 5G-TRANSFORMER Project (grant no. 761536) and
the H2020 ORCHESTRA (Optical peRformanCe monitoring enabling dynamic
networks using a Holistic cross-layEr, Self-configurable Truly
flexible approach, grant agreement no: H2020-645360) project. The
views expressed here are those of the authors only. The European
Commission is not liable for any use that may be made of the
information in this document.
8. Security Considerations
TBD
9. IANA Considerations
TBD
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC7491, March 2015,
<https://www.rfc-editor.org/info/rfc7491>.
10.2. Informative References
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[I-D.ietf-i2rs-yang-network-topo]
Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A Data Model for Network
Topologies", draft-ietf-i2rs-yang-network-topo-20 (work in
progress), December 2017.
[I-D.sambo-netmod-yang-fsm]
Sambo, N., Castoldi, P., Fioccola, G., Cugini, F., Song,
H., and T. Zhou, "YANG model for finite state machine",
draft-sambo-netmod-yang-fsm-03 (work in progress), July
2018.
[I-D.vergara-ccamp-flexigrid-yang]
Madrid, U., Perdices, D., Lopezalvarez, V., Dios, O.,
King, D., Lee, Y., and G. Galimberti, "YANG data model for
Flexi-Grid Optical Networks", draft-vergara-ccamp-
flexigrid-yang-06 (work in progress), January 2018.
[I-D.zhang-ccamp-l1-topo-yang]
zhenghaomian@huawei.com, z., Fan, Z., Sharma, A., and X.
Liu, "A YANG Data Model for Optical Transport Network
Topology", draft-zhang-ccamp-l1-topo-yang-07 (work in
progress), April 2017.
Authors' Addresses
Nicola Sambo
Scuola Superiore Sant'Anna
Via Moruzzi 1
Pisa 56124
Italy
Email: nicola.sambo@sssup.it
Piero Castoldi
Scuola Superiore Sant'Anna
Via Moruzzi 1
Pisa 56124
Italy
Email: piero.castoldi@sssup.it
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Andrea Sgambelluri
Scuola Superiore Sant'Anna
Via Moruzzi 1
Pisa 56124
Italy
Email: andrea.sgambelluri@sssup.it
Giuseppe Fioccola
Huawei Technologies
Riesstrasse, 25
Munich 80992
Germany
Email: giuseppe.fioccola@huawei.com
Filippo Cugini
CNIT
Via Moruzzi 1
Pisa 56124
Italy
Email: filippo.cugini@cnit.it
Daniele Ceccarelli
Ericsson
Torshamnsgatan,48
Stockholm 164 40
Sweden
Email: daniele.ceccarelli@ericsson.com
Haoyu Song
Huawei
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: haoyu.song@huawei.com
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Tianran Zhou
Huawei
156 Beiqing Road
Beijing 100095
China
Email: zhoutianran@huawei.com
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