A YANG Data Model for WDM management in Front-Haul NBI
draft-zhaosun-ccamp-front-haul-wdm-yang-00
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| Authors | Yang Zhao , Jiang Sun , Chaode Yu | ||
| Last updated | 2021-10-25 | ||
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draft-zhaosun-ccamp-front-haul-wdm-yang-00
CCAMP Working Group Y. Zhao
Internet-Draft J. Sun
Intended status: Standards Track China Mobile
Expires: April 28, 2022 C. Yu
Huawei Technologies
October 25, 2021
A YANG Data Model for WDM management in Front-Haul NBI
draft-zhaosun-ccamp-front-haul-wdm-yang-00
Abstract
This document introduces an architecture of semi-active fronthaul WDM
system and explains how the semi-active devices can be managed by a
transmission controller. This document also specifies a YANG data
model for the WDM devices in front-haul scenario, which is defined in
G.owdm. The model is expected to be used in the Northbound of
controller.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Architecture for Semi-active Front-haul WDM . . . . . . . . . 4
3. Model Relationship . . . . . . . . . . . . . . . . . . . . . 7
4. YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. YANG Code for Front-haul WDM . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
In the 5G era, great change of the basic wireless network
architecture from RRU-BBU to AAU-DU-CU brings the change of 5G
transport network from fronthaul-backhaul to fronthaul-middlehaul-
backhaul network. Moreover, to avoid excessive transmission
bandwidth requirement, the CPRI interface evolves to eCPRI interface.
Contemporaneously, the Centralized, Collaborative, Cloud and Clean
Radio Access Network architecture (C-RAN) have been actively deployed
instead of the previous D-RAN architecture by several operators. For
example, the medium-scale C-RAN centralized with 10 base stations
will become the main scenario for 5G network, according to the
statistics of different provinces in China. It is noted that the
transmission distance will be increased from a few hundred meters for
D-RAN to up to 10km for C-RAN (typically 5~10km). As the degree of
centralization increases and the distance from AAU to DU becomes
longer, the complexity of control and operation and maintenance will
greatly increased.
The traditional front-haul solutions will not meet the requirements
of C-RAN, such as the traditional fibre direct connection solution
which requires 12 fibres for six duplex modules of one base station
and occupies large fiber resources for medium and large scale C-RAN.
However, if using WDM technology, a basic fronthaul requirement of a
5G base station with 12-channels can be satisfied by one fiber. A
lot of fiber resource would be saved.
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For 5G C-RAN front-haul network, several front-haul transport schemes
based on WDM technology have been proposed to solve the lack of fiber
core, including passive WDM, active WDM, and semi-active WDM.
The passive WDM system is composed of WDM optical modules and a pair
of passive de/multiplexer at both AAU and DU sides, which has the
advantages of low cost, flexible deployment, etc. However, the
passive equipments cannot support on-line management. The potential
fault points should be manually processed one by one, including
optical modules, WDM de/multiplexer, branch fibers between optical
modules and WDM de/multiplexer, trunk fibers between a pair of WDM
de/multiplexer. This result in long fault detection and service
disruption time.
The active WDM scheme is composed of a pair of active WDM equipments
at both AAU and DU sides and can perform powerful OAM functions, but
the system cost is sharply increased and the deployment of the active
equipment at AAU side is limited by power supply.
The semi-active WDM solution with a passive AAU side and active DU
side not only greatly reduces the pressure of optical fiber
resources, but also has the advantages in cost (compared with the
active solution), management and protection of the front-haul network
(compared with the passive solution). It helps operators to build 5G
fronthaul networks with low cost, high bandwidth and fast deployment.
A centralized transmission controller could manage all the semi-
active WDM systems in a large zone.
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+--------------+
| Transmission |
| controller |
+--------------+
|
+-----+ |
| AAU | |
+-----+\ |
\ +----------+ +-----------+ +---------+
\ | |\ | | /| | | |
\ | | \ | | / | | | |
\| | \ | | / |-|----| |
| | \ | | / | | | |
+-----+ |\|MUX | | | |MUX | | | |
| AAU |-----|-| / |___|______________|____| / |-|----| DU |
+-----+ |/|DMUX| | | |DMUX| | | |
| | | | | | | | | |
/| | / | | \ | | | |
/ | | / | | \ |-|----| |
/ | | / | | \ | | | |
/ | |/ | | \| | | |
+-----+/ | Passive | | active | +---------+
| AAU | | BiDi WDM | | WDM |
+-----+ +----------+ +-----------+
Colored AAU Side DU Side
Optical Module
Figure 1:Semi-active WDM solution
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Architecture for Semi-active Front-haul WDM
The semi-active WDM system is composed by a passive AAU side with
colored optical modules and passive BiDi WDM like MUX/DEMUX, and an
active DU side with active WDM equipment and modules. The active WDM
equipment should be composed by passive BiDi WDM, microprocessor unit
and OAM modulation/demodulation unit. There are some mangement
challenges of semi-active WDM system that need to be resolved. Since
the the AAU and DU are both wireless devices and could not be managed
by transmission controller, the management of optical modules at AAU/
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DU side is difficult and special. Because of the passive AAU side,
the management of passive AAU side have to be done through the active
DU side.
One of workable solutions is introduced below. An OAM channel in the
semi-active WDM solution could be implemented by service signal
overhead or pilot tone with the low modulation depth of the optical
channel signal. The OAM channel is used to transmit management and
control information between the AAU side and the DU side. The active
WDM equipment could send management requests to the AAU and manage
the optical modules within the AAU, including query and
configuration. The optical modules within the AAU can receive
management requests from the active WDM equipment and then send the
OAM information of AAU and the optical modules to the active WDM
equipment automatically or at regular time intervals once the optical
modules are powered on, including the wavelength, driving voltage,
driving current, launch power of the transmitter, transceiver optical
receive power, etc. The WDM optical modules can add the OAM
information with the service signals and transport together in the
same optical channel. The detection unit in the active WDM equipment
can demodulate the OAM information, obtain the transmission
performance of AAU and modules, and then report it to the
transmission controller.
The centralized transmission controller for the semi-active WDM
systems could display of the network topology, equipment, and module
information, and support fault monitoring of the fronthaul network.
Fig.2 shows the link failure monitoring functions. These failures
could be monitored at branch fibers between optical modules and WDM
de/multiplexer in AAU side as 1 and 2, branch fibers between optical
modules and WDM de/multiplexer in DU side as 4 and 5, fiber link as
3, modules as 6 illustrated in Figure 2.
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+---------+ +----------+ +-----------+ +---------+
| | | |\ | | /| | | |
| | | | \ | | / | | | |
| | | | \ | | / | | | |
| AAU | | | \ | | / | | | DU |
| +-------|-+ 1 | |MUX | | 3 | |MUX | | 4 +-|-------+ |
| |Optical| |------>| | / |___|_______|____| / | |-------> | |Optical| |
| |Module |6|<------| |DMUX| | | |DMUX| |<------- |6|Module | |
| +-------|-+ 2 | | | | | | | | 5 +-|-------+ |
| | | | / | | \ | | | |
| | | | / | | \ | | | |
| | | | / | | \ | | | |
| | | |/ | | \| | | |
+---------+ | Passive | | active | +---------+
| BiDi WDM | | WDM |
+----------+ +-----------+
AAU Side DU Side
Figure 2: Illustration of potential failures analysis
There is also a requirement for protection in the semi-active WDM
solution. By introducing a splitter and a switch between the remote
and local part as figure 3, the semi-active WDM system is of OLP
protection like capability.
+--------+ +-----------------+ +---------------+ +--------+
| | ||\ +--------+| |+------+ /|| | |
| | || \ | || Working || | / || | |
| | || \ | || Link || | / || | |
| AAU | || \ | _|| _ _ _ _ _||_ | / || | DU |
|+-------|+ ||MUX | | / || || * | |MUX || +|-------+|
||Optical||->|| / |_|+---+/ || || \ _ |_| / ||->||Optical||
||Module ||<-||DMUX| |+---+\ || || * | |DMUX||<-||Module ||
|+-------|+ || | | \_|| _ _ _ _ _||_ | | || +|-------+|
| | || / | ||Protection|| * | \ || | |
| | || / | 3dB || Link || 1*2 | \ || | |
| | || / |splitter|| ||switch| \ || | |
| | ||/ +--------+| |+------+ \|| | |
+--------+ | Passive | | active | +--------+
| BiDi WDM | | WDM |
+-----------------+ +---------------+
AAU Side DU Side
Figure 3: Protection of semi-active WDM system
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3. Model Relationship
In the semi-active WDM solution, transmission controller is preferred
to manage WDM equipments and the optical models on AAU and DU.
Though there are some data models have been defined for the WDM
management, consider that the AAU and DU are both wireless devices,
some extensions are needed for the transmission controller to manage
them.
For a full-lifecycle management, the traditional NMS function and SDN
control plane are both required, includes tunnel, topology,
inventory, alarm and performance management.
For daily maintenance, e.g. fault location, there is a requirement of
viewing the whole signal flow. So the tunnel and topology model are
necessary in the semi-active WDM system management. The WDM related
models existing, like RFC9094, draft-ietf-ccamp-wson-tunnel-model and
draft-ietf-ccamp-flexgrid-yang etc. are all considered useable in
semi-active WDM system management.
It is suggested that the solution and data model in draft-yg3bp-
ccamp-optical-inventory-yang can be used for inventory management.
The inventory model is in the first I-D draft version state, let's
keep tracing on this model.
Solution and data model in RFC8632 should be used for alarm
management. We will do more research on whether is there special
requirements of semi-active system on alarm management.
For the performance management, e.g. OAM and loop-back operations,
is also required for the semi-active WDM system management. The
draft-ietf-teas-actn-pm-telemetry-autonomics defines a generic
performance management framework. And the draft-zheng-ccamp-client-
pm-yang defines an Ethernet over OTN service level performance
monitoring. We consider that both of these two models can be used in
the semi-active WDM management model in the future.
4. YANG Tree
We will provide some augmentations on the existing tunnel, topology,
inventory, alarm and performance models based on our further
investigation.
5. YANG Code for Front-haul WDM
We will provide some augmentations on the existing tunnel, topology,
inventory, alarm and performance models based on our further
investigation.
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6. Security Considerations
TBD
7. IANA Considerations
This document does not have any requirement on IANA allocation.
8. Contributors
Haomian Zheng
Huawei Technologies
Email: zhenghaomian@huawei.com
9. 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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses
Yang Zhao
China Mobile
Email: zhaoyangyjy@chinamobile.com
Jiang Sun
China Mobile
Email: sunjiang@chinamobile.com
Chaode Yu
Huawei Technologies
Email: yuchaode@huawei.com
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