nmrg X. Li
Internet Draft L. Zhang
Intended status: Informational J. Wei
Expires: May 2021 Y. Tang
S. Huang
BUPT
November 2, 2020
Centralized Control and Distributed Function Slicing for Fast
Connection Establishment and Fault Recovery in Optical Networks
draft-li-nmrg-control-slicing-00.txt
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Internet-Draft Centralized Control and Distributed Function Slicing for
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Abstract
Optical networks which support a large number of emerging
applications, such as 5G, Cloud Computing, Big Data, Internet of
things, autonomous driving, etc., play an increasingly important
role in the current world. All the time spectrum resources in
optical networks have been treated equally. All spectrum resources
form a resource pool which is allocated to applications bit by bit
until it is all used up. Although this pattern reduces the
complexity of resource maintenance, it has poor flexibility and high
operation complexity for different types of applications. This draft
proposes a framework of centralized control and distributed function
slicing for fast connection establishment and fault recovery in
optical networks. The proposed framework divides all spectrum
resources into four functional areas, i.e., optical channel area,
fault recovery area, resource pool area, and the reserved functional
area. A functional area is responsible for a specific network
function. This framework improves the flexibility of optical
networks and can achieve fast connection establishment and fault
recovery for the request with a highest service level.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................4
3. Motivation of Centralized Control and Distributed Function
Slicing...........................................................5
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4. Centralized Control and Distributed Function Slicing Framework.5
4.1. Framework.................................................6
4.2. Optical Channel Area......................................7
4.3. Fault Recovery Area.......................................8
4.4. Resource Pool Area........................................8
4.5. Reserved Functional Area..................................8
5. Security Considerations........................................8
6. IANA Considerations............................................8
7. References.....................................................9
7.1. Normative References......................................9
7.2. Informative References....................................9
1. Introduction
This document describes the framework of centralized control and
distributed function slicing for fast connection establishment and
fault recovery in optical networks. Recently, a large number of
emerging applications, such as 5G, Cloud Computing, Big Data,
Internet of things, autonomous driving, etc., are emerging. Optical
networks which take advantages of large-capacity, high-speed, and
low energy consumption play an increasingly important role while
accommodating these applications. Meanwhile, optical networks have
been developed gradually from the point-to-point transmission to
multi-layer and multi-domain networking. In the process of
development, some important architectures and protocols have been
proposed, such as automatically switched optical network (ASON),
generalized multiprotocol label switching (GMPLS), path computation
element (PCE), software defined optical network (SDON), etc. ASON is
to facilitate fast configuration of both switched and soft permanent
connections. The GMPLS protocol is proposed to realize the control
plane. The PCE is proposed to conduct the constraint-based light-
path computation in multi-domain and multi-layer optical networks
[Pao2013]. SDON adopts the centralized control mode and supports
multiple novel applications such as bandwidth on demand (BoD),
virtual optical network (VON), dynamic path protection, etc
[Thy2016]. These architectures and protocols help to reduce the
operation complexity of optical networks. However, all the time
spectrum resources for these architectures and protocols have been
treated equally. For example, when a user request arrives, spectrum
resources are equally allocated whether this request has a high
service level or not. No matter the request has a high service level
or a low high service level, the control plane equally conducts the
process of routing and spectrum allocation. In other words, all
spectrum resources form a resource pool which is equally allocated
to applications bit by bit until it is all used up. Although this
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pattern reduces the complexity of resource maintenance, it has poor
flexibility and high operation complexity for different types of
applications. For example, the establishment and removal of an end-
to-end light-path is implemented by the centralized controller in
SDONs. When a user request arrives at an optical network, the
controller needs to compute the path and distribute the cross
connection message by southbound protocol for optical networks. The
process will consume a lot of time and is difficult to achieve the
fast connection establishment. For some user requests with the
highest service level, this time consumption may be intolerable. If
some light-paths or light-trees are pre-established, then these
light-paths can be used directly. This new mechanism can save a lot
of path computation time for some services with the highest level.
This draft proposes a framework of centralized control and
distributed function slicing for fast connection establishment and
fault recovery in optical networks. The proposed framework divides
all spectrum resources into four functional areas. A functional area
is a range of spectrum in the resource pool. Some particular pre-
configured functions have been reserved in each functional area. A
functional area or multiple functional areas can be allocated to an
application. The first functional area is the optical channel area
in which a group of light-paths or light-trees have already been
established and can be used directly. The second functional area is
the fault recovery area in which all interrupted light-paths or
light-trees are recovered in this area. The third functional area is
the resource pool area where spectrum resources are allocated to
applications equally. The fourth functional area is the reserved
functional area where new function can be explored in this area.
This framework improves the flexibility of optical networks and can
achieve fast connection establishment and fault recovery.
2. Conventions used in this document
This document makes use of the following acronyms:
SDON: Software-Defined Optical Networks
GMPLS: Generalized Multi-Protocol Label Switching
PCE: Path Calculation Element
ASON: Automatically Switched Optical Network
VON: Virtual Optical Network
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BoD: Bandwidth on Demand
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
In this document, the characters ">>" preceding an indented line(s)
indicates a statement using the key words listed above. This
convention aids reviewers in quickly identifying or finding the
portions of this RFC covered by these keywords.
3. Motivation of Centralized Control and Distributed Function Slicing
All the time spectrum resources in optical networks have been
treated equally. All spectrum resources form a resource pool which
is used in the same way. Although this pattern reduces the
complexity of resource maintenance, it has poor flexibility and high
operation complexity for different types of applications. It is
difficult to achieve fast connection establishment and fault
recovery based on this organization form of spectrum resources. The
disadvantage of SDON is decoupling the control function from
physical optical devices. The next research will focus on how to
make better use of all spectrum resources. Therefore, in order to
resolve this problem, this draft proposes a framework of centralized
control and distributed function slicing for fast connection
establishment and fault recovery in optical networks. It divides all
spectrum resources into four functional areas, i.e., optical channel
area, fault recovery area, resource pool area, and the reserved
functional area. A functional area is responsible for a specific
network function, especially for fast connection establishment and
fault recovery. This framework improves the flexibility of optical
networks and can achieve fast connection establishment and fault
recovery for the request with a highest service level. From the
perspective of time consuming of connection establishment and fault
recovery, the centralized control and distributed function slicing
framework will get enormous benefits.
4. Centralized Control and Distributed Function Slicing Framework
This section first gives an overview of the framework of centralized
control and distributed function slicing.
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4.1. Framework
+------------------------------------------------------------+
| |
| Centralized Controller |
| |
+------------------------------------------------------------+
| | | |
| | | |
V V V V
+------------+ +------------+ +------------+ +------------+
| Lightweight| | Lightweight| | Normal | | Lightweight|
| Operating | | Operating | | Operating | | Operating |
+------------+ +------------+ +------------+ +------------+
| | | |
| | | |Control Plane
--------------------------------------------------------------------
| | | |Physical
Plane
V V V V
+------------+ +-------------+ +------------+ +-------------+
| Optical | | Fault | | Resource | | Reserved |
|Channel Area| |Recovery Area| | Pool Area | |Function Area|
+------------+ +-------------+ +------------+ +-------------+
------------------------------------------------------------------->
Distributed Function Slicing
Figure 1 Centralized Control and Distributed Function Slicing
Figure 1 shows the framework of centralized control and distributed
function slicing. It contains two parts, i.e., control plane and
physical plane. Control plane is realized by a centralized
controller. Being different from conventional controller, this
controller supports the lightweight operating on some functional
areas. Therefore, conventional complex operations can be simplified.
All spectrum resources in physical plane are divided into four
functional areas, i.e., optical channel area, fault recovery area,
resource pool area, and the reserved functional area. Figure 2
presents four functional areas. Since physical plane contains
different types of resources, this draft only focus on spectrum
resource slicing. A functional area is responsible for a specific
network function. For the optical channel area, some optical
channels have been already established. These optical channels can
be used directly without routing and spectrum allocation. Therefore,
only lightweight operating is required in the optical channel area.
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This area supports fast connection establishment. The fault recovery
area can continue to be divided into sub-area. When faults occur in
the optical networks, all interrupted services can be recovered in
these sub-areas in parallel. It avoids the traffic congestion caused
by resource competition. This area supports fast fault recovery. For
the resource pool area, all spectrum resources are treated equally
and can be allocated to applications bit by bit until it is all used
up. For the reserved functional area, this area is reserved for
developing other novel network functions.
|<-------------->|<----------------->|<----------->|<------------->|
| | | … | | | | | … | | | | | … | | | | | … | | |
| | | … | | | | | … | | | | | … | | | | | … | | |
+----------------+-------------------+-------------+--------- -----+
|Optical Channel |Fault Recovery Area|Resource Pool| Reserved |
| Area | | | Fuction Area |
Figure 2 Four Functional Areas
4.2. Optical Channel Area
In the optical channel area, some optical channels have been already
established. These optical channels can be used directly. The type
and the number of established optical channels are determined by the
real network environment. Each established optical channels contain
four parts, i.e., source, destination, bandwidth, and path.
Table 1 Already Established Optical Channels
+------------+--------------+------------+-------------+
| Source | Destinations | Bandwidth | Path |
+------------+--------------+------------+-------------+
| A | B | 40G | A->E->F->B |
+------------+--------------+------------+-------------+
| C | D | 100G |C->H->G->Q->D|
+------------+--------------+------------+-------------+
| … | … | … | … |
+------------+--------------+------------+-------------+
Source: the node at which the traffic uploads.
Destinations: a set of nodes at which the traffic downloads.
Bandwidth: the transmission rate of this optical channel.
Path: successive links which connect the source and destinations.
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4.3. Fault Recovery Area
The fault recovery area is divided into multiple sub-areas. When
faults occur in the optical networks, all interrupted services can
be recovered in these sub-areas in parallel. It avoids the traffic
congestion caused by resource competition. This area supports fast
fault recovery.
| Fault Recovery Area |
|<---------------------------------------------------------------->|
| | | … | | | | | … | | | | | … | | |
| | | … | | | | | … | | | | | … | | |
+----------------------+----------------------+--------------------+
| Sub-Area | Sub-Area | Sub-Area |
Figure 3 Multiple Sub-Areas in Fault Recovery Area
Once a fault occurs in an optical network, all interrupted services
are sorted and organized into several groups. Each group is
allocated to a sub-area. These groups can conduct service recovery
in parallel. Therefore, the fault recovery area supports fast fault
recovery.
4.4. Resource Pool Area
In the resource pool area, all spectrum resources are treated
equally and can be allocated to applications bit by bit until it is
all used up.
4.5. Reserved Functional Area
This area is reserved for developing other novel network functions.
5. Security Considerations
TBD
6. IANA Considerations
This document makes no request of IANA.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[Pao2013] F. Paolucci, F. Cugini, A. Giorgetti, N. Sambo, and P.
Castoldi, "A Survey on the Path Computation Element (PCE)
Architecture", IEEE COMMUNICATIONS SURVEYS & TUTORIALS,
vol. 15, no. 4, pp. 1819-1841, 2013.
[Thy2016] A. Thyagaturu, A. Mercian, M. McGarry, M. Reisslein, and
W. Kellerer, "Software Defined Optical Networks (SDONs):
A Comprehensive Survey", IEEE COMMUNICATIONS SURVEYS &
TUTORIALS, VOL. 18, NO. 4, pp. 2738-2786, 2016.
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Authors' Addresses
Xin Li
Beijing University of Posts and Telecommunications
10 Xitucheng Road, Haidian District, Beijing, China
Email: xinli@bupt.edu.cn
Lu Zhang
Beijing University of Posts and Telecommunications
10 Xitucheng Road, Haidian District, Beijing, China
Email: luzhang@bupt.edu.cn
Jianghua Wei
Beijing University of Posts and Telecommunications
10 Xitucheng Road, Haidian District, Beijing, China
Email: jhwei@bupt.edu.cn
Ying Tang
Beijing University of Posts and Telecommunications
10 Xitucheng Road, Haidian District, Beijing, China
Email: ytang@bupt.edu.cn
Shanguo Huang
Beijing University of Posts and Telecommunications
10 Xitucheng Road, Haidian District, Beijing, China
Email: shghuang@bupt.edu.cn
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