Internet DRAFT - draft-ietf-forces-consistent-control
draft-ietf-forces-consistent-control
Forwarding and Control Element Separation L. Zeng
Internet Draft <Tsinghua University>
Intended status: Informational May 7, 2014
Expires: November 2014
Consistent Control Mechanism in Software Defined Network
draft-ietf-forces-consistent-control-00.txt
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Consistent Control Mechanism in Software Defined Network May 2014
Abstract
This document introduces a consistent control mechanism in the
framework of Software Defined Network (SDN), which is one method to
achieve forwarding and control element separation. In detail, this
mechanism uses a centralized control element to control multiple
forwarding elements.
Table of Contents
1. Introduction ................................................ 2
2. Conventions used in this document............................ 2
3. Software Defined Network Framework........................... 3
4. Control Problem in SDN Framework............................. 4
5. Consistent Flow Control Mechanism............................ 5
6. Security Considerations...................................... 6
7. IANA Considerations ......................................... 6
8. Conclusions ................................................. 6
9. References .................................................. 6
9.1. Normative References.................................... 6
9.2. Informative References.................................. 6
10. Acknowledgments ............................................ 6
1. Introduction
Software Defined Network (SDN) is proposed in recent years, and is
considered as a promising way to separate forwarding plane and
control plane [FORCES-SDN]. In detail, SDN is an approach to
networking in which control is decoupled from hardware and given to a
software application.
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 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 RFC-2119 significance.
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Consistent Control Mechanism in Software Defined Network May 2014
3. Software Defined Network Framework
A logical view of the SDN architecture is shown in Figure 1, which
consists of three layers: infrastructure layer, control layer and
application layer.
+--------------------------------------------------------------+
| +--------------------------------------------------------+ |
| | +---------------------+ | |
| | | | | |
| | Application +--+------------------+--+ | |
| | | | | |
| | Layer +--+------------------+--+ | |
| | |Business Applications| | |
| | +---*------*------*---+ | |
| +------------------------|------|------|-----------------+ |
| |API |API |API |
| +------------------------|------|------|-----------------+ |
| | +----------*------*------*---------------+ | |
| | | +----------------+ | | |
| | | SDN | | | | |
| | | Control +--+-------------+--+ | | |
| | Control | Software | | | | |
| | Layer | +--+-------------+--+ | | |
| | | |Network Services| | | |
| | | +----------------+ | | |
| | +------------**--------------------------+ | |
| +--------------------------||-------------------------+ | |
| ||Control Data Plane Interface| |
| ||(e.g., OpenFlow [FORCES-OF])| |
| +--------------------------||----------------------------+ |
| | Infrastructure || | |
| | Layer || | |
| | +--------------+ +-----**-------+ +--------------+ | |
| | |Network Device| |Network Device| |Network Device| | |
| | +--------------+ +--------------+ +--------------+ | |
| | +--------------+ +--------------+ | |
| | |Network Device| |Network Device| | |
| | +--------------+ +--------------+ | |
| +--------------------------------------------------------+ |
+--------------------------------------------------------------+
Figure 1 Software-Defined Network Architecture
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Consistent Control Mechanism in Software Defined Network May 2014
In infrastructure layer, network devices are only in charge of
executing the forwarding functions. Network control intelligence is
logically centralized in control layer. In particular, a centralized
SDN based controller is in charge of controlling function. In the
controller, different network control functions can be developed as
customized. As to application layer, different kinds of business
applications are deployed. Between application layer and control
layer, a set of APIs (Application Programming Interfaces) are
designed, which allows business applications to use network control
services in control layer. Also, control data plane interface is
designed between control layer and infrastructure layer, which is
used to interchange control and forwarding information between the
controller and network devices.
In the SDN architecture, the controller uses flow entry to control
multiple network services, where the forwarding function is executed.
In each network service, there exists a flow table to store flow
entries sent by the controller. The controller can add/delete/modify
flow entries to each network service.
4. Control Problem in SDN Framework
In SDN framework, the controller uses flow entries to control
forwarding behavior of different network devices. In particular,
there are special security channel between the controller and network
devices to transform flow entry information.
Since multiple network devices make up a distributed system, control
problem exists in SDN framework. In detail, it is difficult for the
controller to update multiple flow entries simultaneously, due to
different latency of different special security channels. If these
flow entries are written into network devices at different time, data
packets may follow the wrong control instruction and be incorrectly
deal with, leading to system chaos, packets loss, service deteriorate,
and etc.
Due to this control problem, it is necessary to study consistent flow
control mechanism for SDN framework. The consistent flow control
problem is defined as follows: when the controller updates flow table
in multiple network devices, each data packet flowing through the
network must be processed according to a single network control
configuration, either the old control configuration or the new
control configuration, but not a mixture of both configurations, or
other uncertain rules.
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Consistent Control Mechanism in Software Defined Network May 2014
5. Consistent Flow Control Mechanism
A consistent flow control mechanism is proposed in this section. In
an update event, the controller updates flow entries from an old flow
configuration to a new flow configuration in a set of network devices.
First, the controller divides these network devices into two parts.
1) Entry Network Device (END): the first network device in the set of
network devices, in which data packet is handled with the now flow
configuration.
2) Other Network Device (OND): other network devices in the set of
network devices, except for the END.
Then, the controller divides flow entries in both configurations into
four parts:
1) New Flow Entry (NFE): new flow entry only in new configuration.
2) Shared Flow Entry (SFE): flow entry existing in both configuration.
3) Deleted Flow Entry (DFE): old flow entry only in old configuration.
4) Modified Flow Entry (MFE): different control behavior of the same
data packet in two configurations.
The important steps of proposed consistent flow control mechanism are
introduced as follows:
Step 1: the controller analyzes network devices and two sets of flow
configurations, which are respectively divided into several parts.
Step 2: In END, the controller uploads all data packets influenced by
this update event, except for the packets controlled by SFE.
Step 3: The controller writes NFE in OND, and then waits for an end-
to-end network latency.
Step 4: The controller finishes all updates in OND, including adding
MFE and deleting DFE.
Step 5: The controller finishes all updates in END, and stops
uploading data packets from EDN.
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6. Security Considerations
This requirements document does not raise in itself any specific
security issues.
7. IANA Considerations
IANA does not need to take any action for this draft.
8. Conclusions
This document provides a consistent control mechanism in the
framework of Software Defined Network (SDN). In detail, this
mechanism uses a centralized control element to control multiple
forwarding elements.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[FORCES-SDN] McKeown N. "Ooftware-defined networking", INFOCOM
keynote talk, 2009.
[FORCES-OF] McKeown N, Anderson T, Balakrishnan H, et
al. "OpenFlow: enabling innovation in campus networks",
ACM SIGCOMM Computer Communication Review, 2008, 38(2),
pp. 69-74.
10. Acknowledgments
This work is supported by Chinese National Major Scientific and
Technological Specialized Project (No.~2013ZX03002001), National
Basic Research Program of China (973 Program Grant No.~2013CB329105),
China's Next Generation Internet (No.~CNGI-12-03-007), and ZTE
Corporation.
This document was prepared using 2-Word-v2.0.template.dot.
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Authors' Addresses
Lieguang Zeng
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: zenglg@mail.tsinghua.edu.cn
Ye Zhou
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: yetiero@gmail.com
Mao Yang
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: yangmao210@163.com
Yong Li
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: liyong07@tsinghua.edu.cn
Depeng Jin
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: jindp@mail.tsinghua.edu.cn
Li Su
Department of Electronic Engineering, Tsinghua University
Department of Electronic Engineering, Tsinghua University, Beijing,
China
Email: lisu@tsinghua.edu.cn
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