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Versions: 00                                                            
    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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    Consistent Control Mechanism in Software Defined Network       May 2014
    
    
    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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    Consistent Control Mechanism in Software Defined Network       May 2014
    
    
    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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