SDNRG Q. Kong Internet Draft T. Gao Intended status: Informational BUPT Expires: October 2016 D. Wang Z. Wang J. Wang ZTE B. Guo S. Huang BUPT April 20, 2016 Routing Optimization with SDN in Data Center Networks draft-kong-sdnrg-routing-optimization-sdn-in-dc-00 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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." 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Abstract With the open and standard programmatic interface and the flexibility of controlling network, Software Defined Network (SDN) can obviously simplify and integrate operation and business support systems. As a consequence, to satisfy the rising switching demand in the data center network, it is a good option to adopt SDN technology. In addition, current architecture of data center network is far from ideality, which results in the low utilization rate in bandwidth resource. For example, mice flow cannot be well effectively served in the conventional Wavelength Division Multiplexing (WDM) optical network with at least 50GHz spectrum interval. From a data center network perspective, it is necessary to further improve the resource utilization efficiency and the flexibility of coping with different traffic. This document described an optical data center interconnect, which comprises both the fixed and flexible grid transceivers. A traffic monitor is implemented in the SDN-based data center network to evaluate the coming traffic demands and allocate appropriate spectrum for the request. For instance, mice flow can be served by fixed grid transceivers, well the elephant flows can be transmitted by the flexi-grid transceiver using multiple subcarriers to form a superchannel. Thus, spectrum efficiency is optimized and bandwidth utilization is improved dramatically. Table of Contents 1. Introduction ................................................ 3 2. Conventions used in this document ........................... 3 3. Required Technology ......................................... 4 4. Data center interconnect .................................... 5 5. Traffic-Monitor based routing in data center networks ....... 6 6. Dynamic traffic demand recognition scheme ................... 7 7. Security Considerations ..................................... 8 8. IANA Considerations ......................................... 8 9. Conclusions and Use Cases ................................... 8 10. References ................................................. 9 10.1. Normative References .................................. 9 10.2. Informative References ............................... 9 Kong, et al. Expires October 20, 2016 [Page 2] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 1. Introduction The bandwidth bottleneck and growing power requirements have become central challenges for high performance DCN interconnect. The current fat tree topology causes communication bottlenecks in the server interaction process, resulting in power-hungry O-E-O conversions that limit the minimum latency and the power efficiency of these systems. Various optical interconnect [KT12] have been proposed to take advantage of the high bandwidth capacity and low power consumption offered by optical switching. The optical data center interconnect also provides interface to control plane for the network control and operation. This opens the opportunity to implement enhanced network functions as all components running under the centralized software- defined networking (SDN) controller through SDN agents. With the advantage of the flexibility of controlling network and the privacy of network operations, the concept of SDN is rapidly adopted in data centers. SDN technology has been mature for the commercial deployment in data centers, and most notably, Google has realized the interconnection between its data centers through the two intercontinental backbone networks. From a data center network perspective, the research focused on further improving the resource utilizing efficiency and the flexibility of coping with different traffic demands is never out of date. This document describes a data center interconnect with SDN control which can support both finer and coarse granularity switching requirements. By implementing traffic monitoring into SDN-based data center network to allocate appropriate bandwidth to either fixed or flexible grid channel, spectrum efficiency is optimized and bandwidth utilization is greatly increased. To realize both fixed grid and flexible grid transmission, multiple Small Form-Factor Pluggable (SFPs) and Single-Carrier Frequency-Division-Multiplexed (SCFDM) transceivers are attached to the cascaded (Micro-Electro-Mechanical System) MEMS which is in charge of the communication between ToRs in different clusters. We also proposed a module named MUX/DEMUX&SSS module using optical components to provide the flexible switching functionality. 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]. This document makes use of the following acronyms: SDN: Software Defined Network Kong, et al. Expires October 20, 2016 [Page 3] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 WDM: Wavelength Division Multiplexing MEMS: Micro-Electro-Mechanical System ToRs: Top-of-Racks SFP: Small Form-Factor Pluggable SCFDM: Single-Carrier Frequency-Division-Multiplexed SSS: Spectrum Selective Switches AWG: Arrayed Waveguide Grating MIMO: Multi-Input Multi-Output 3. Required Technology With the wide deployment of cloud computing and other kinds of applications, traffic switching inter or intra data center networks is drawing more and more attention. Nevertheless, despite the commercial employment of SDN technology in the data centers, architecture of current data centers network is still far from being ideal. On one hand, in conventional WDM optical networks, a traffic demand is supported by a wavelength channel which occupies a 50GHz spectrum. In this case, when the traffic demand between the end nodes is no more than the capacity of the wavelength channel, the spectrum is waste because of the fixed and coarse granularity. To address this issue, scenario where flexible and fixed grid transceivers can be adopted in the data center networks. On the other hand, with the advantage of open interfaces and programming, the SDN-enabled network can be implemented to realize required control methods to optimize the bandwidth efficiency. To satisfy the requirement of fast speed switching as well as improving bandwidth efficiency in data center networks, traffic monitor is embedded in the ToR to monitor the bandwidth that might require to modulate the traffic to either fixed or flexible grid channel. Monitoring the traffic before it comes, mice or elephant flow can be severed by allocating appropriate flexible or fixed grid bandwidth rather than allocating uniform fixed 50GHz bandwidth. Thus, the spectrum is optimized and the bandwidth utilizing is improved. Kong, et al. Expires October 20, 2016 [Page 4] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 4. Data center interconnect As shown in Fig.1, we employ the cascaded MEMS-switches. The inter- cluster MEMS in the core is in charge of the communication between ToRs in different clusters. Multiple SFPs and SCFDM transceivers are implemented to realize the mixed transmission whose bandwidth demand is either fixed grid or flexible grid. To provide flexible switching functionality, we proposed the module named Mux/Demux & SSS which is illustrated in Fig.2. Optical components such as coupler, Spectrum Selective Switches (SSS), Arrayed Waveguide Grating (AWG), and circulator are attached to a backplane to further increase the flexibility of coping with different traffic demands. In Fig.2, the symbol "@" represents a circulator which is a passive non-reciprocal three-port device, and an optical signal entering any port is transmitted to the next port in rotation(only). The coupler is a passive device which is used to split and combine signals in the optical network and can have multiple inputs and outputs. The SSS is typical an 1xN optical component that can partition the spectrum of input signal to different ports. The AWG is a passive data-rate independent optical device that route each wavelength of an input to a different output. Using this module, traffic can be deliberately added and dropped through these components, and can be merged and switched to the same destination together through AWG or coupler, and also can be separated by SSS and switched to the different output ports for purpose of realizing Multi-Input Multi-Output(MIMO) switching. At the same time, each ToR has both SFP and SCFDM transceivers which can realize fixed or flexible grid traffic switching. Thus, each rack can communicate with multiple racks simultaneous and high interconnect efficiency can be achieved as arbitrary traffic inter or intra ToRs can be switched using fine bandwidth rather than fixed grid bandwidth. +----------------+ +----------------+ +----------------+ |Mux/Demux &SSS 1| |Mux/Demux &SSS 2| |Mux/Demux &SSS 3| ... +----------------+ +----------------+ +----------------+ | | | | | | | | | | | | | | | | | | +----------------------------------------------------------------+ | Optical OXC | +----------------------------------------------------------------+ | | | | | | | | | | | | +--------------+ +--------------+ +--------------+ | SFP|BV-TX/RX | | SFP|BV-TX/RX | | SFP|BV-TX/RX | | ToR 1 | | ToR 2 | | ToR 3 | +--------------+ +--------------+ +--------------+ Kong, et al. Expires October 20, 2016 [Page 5] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 Figure 1: Schematic of architecture in data center +------------------------------------------------------------------+ | | +------------------------------------------------------------------+ A A A A | | | | +---|---------------------|--------|------|--------|--|--|-----|--+ | | V | | | | | | | | | +--------------@ V | +---------+ | | | | | +----------A--------@ V | AWG | | | | | | | +-----|---------A------@ +---------+ | | | | | | | | | A | | | | | V V V | | | +--------+ | | | +---------+ +---------------------+ | | +-----| Coupler | | SSS | | | +---------+ +---------------------+ | +-----------------------------------------------------------------+ Figure 2: Mux/Demux &&& SSS 5. Traffic-Monitor based routing in data center networks The proposed architecture which is based on SDN technology is shown in Fig.3. Resource Computation Element (RCE) is responsible for allocating available port resource to configure the backplane to sever the new coming request based on the resource information provided by the Resource Management Element (RME).RME storages all of the port and spectrum information. Both RCE and RME are controlled by a SDN controller. In particular, RCE can be implemented with certain algorithm for routing and allocating spectrum optimally and RME can also be configured by the SDN controller. When a new traffic comes from ToRs, RCE inquiries the RME for the available port resource and other information to compute the most suitable route and allocate appropriate spectrum. If there is no available resource for the moment, the request will be stored in the buffer. The traffic monitor provides all the traffic request information both come and in the buffer in order to evaluate the type of the traffic, and then passes the information to RME to execute the processing scheme which we will discuss about later. Kong, et al. Expires October 20, 2016 [Page 6] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 After finishing computing the optimized route, the optical switching module is configured through an agent to allocate appropriate bandwidth for the request. With the implement of bandwidth variable component and the capacity of both fixed and flexible grid switching, the optical backplane can be ordered to allocate exactly appropriate bandwidth for coming demands. As a consequence, the requests from the ToRs are satisfied with the optimized route and high resource utilizing. +---------------------------------|-----------+ ---+---+---+ | SDN controller | +---> | | |----+-->+--------------+ +--------------+ | | ---+---+---+ | | Resource |----->| Resource | | | Buffer | | Computation | | Management | | | ---+---+---+ | | Element |<-----| Element | | | +-> | | |----+-->+--------------+ +--------------+ | | | ---+---+---+ +----------A----------------------------------+ | | | | | | | v | | +--------------------+------+ | | +---------+ +----+ +-----+ | Agent| | +--| Request |---->|ToRs|---->|Tx/Rx|-----> +------+------+------+ | +---------+ +----+ +-----+ | Optical | | +---------+ +----+ +-----+ | Switching | +----| Request |---->|ToRs|---->|Tx/Rx|-----> | Module | +---------+ +----+ +-----+ +--------------------+ +------------+ A | Traffic | | | Monitor |----+ +------------+ Figure 3: Traffic Monitor implemented architecture 6. Dynamic traffic demand recognition scheme With the implement of traffic monitor, the proposed architecture can support the new switching requirements by executing dynamic traffic demand recognition scheme through RME which is described above. We monitor the traffic before they come, and evaluate the type of traffic demand, and then allocate appropriate bandwidth according to the request. When traffic comes, it is arbitrated by RME whether it is a flexible grid signal to determine where it goes. A flexible grid signal is transferred to the SCFDM transceiver and then arbitrated whether it is intra-data center request. If it is, optical components such as SSS and coupler will be placed to set or reuse connection. Similarly, a fixed grid signal is transferred to SFP module and arbitrated whether it is intra-cluster request to determine where it Kong, et al. Expires October 20, 2016 [Page 7] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 will be transferred next step. Thus, bandwidth with fine granularity can be allocated to satisfy the dynamic traffic demand in data center network. For instance, mice flow can be served directly by being modulated to SCFDM transmitter. At the meantime, elephant flow can also be divided into fixed and flexible grid signal. Fixed grid signal can be switched to the WDM SFP transceivers which support 2.5 Gbps and 10 Gbps transmission. Flexible grid traffic demand can be served by the SCFDM transceivers. Such algorithm can allocate optimized bandwidth to potential request. Thus, both mice and elephant flow can be served by either using the already existing connection or setup new route to avoid frequent configuration of the optical backplane. 7. Security Considerations Security in the communication between ToRs through Optical Backplane in data center network is to be addressed. While the security of the architecture described in this document greatly depends on the security of communication mechanism itself such as communication protocols, processing procedure and so on. However, the architecture that implements the traffic monitor can improve the security of switching in data center network by evaluating the type of coming traffic. 8. IANA Considerations This document includes no request to IANA. 9. Conclusions and Use Cases Data centers have received more and more attention as a result of increasing demand for storing and switching large volumes of data. With the advantage of open programmatic interface and privacy of operations, SDN tends to be applied to data center so as to improve the spectrum efficiency and bandwidth utilizing. This document describes an architecture where a traffic monitor is implemented and bandwidth variable components are adopted. Due to the capacity of monitoring the traffic before they come, we can evaluate the type of the requests and inquires RME whose function is to store all ports information whether they are occupied or released. Based on obtained the available resource information from RME, RCE then allocate appropriate bandwidth for the request which may be fixed or flexible grid. Rather than allocating the bandwidth with rigid and coarse granularity, the new switching requirements are supported to satisfy the dynamic traffic demand in data center networks. As a Kong, et al. Expires October 20, 2016 [Page 8] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 consequence, the spectrum efficiency is optimized and bandwidth utilization is increased dramatically. With the feature of switching traffic using both fixed and flexible grid bandwidth, the proposed architecture can be well adopted in various network structure especially in data center network. For example, it can be accustomed to the scenario where data flow is big and duration time is long such as data migration in the midnight, as well as the scenario where data flow is slight and duration time is short such as a Web request. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 10.2. Informative References [KT12] C. Kachris, and I. Tomkos, "A Survey on Optical Interconnects for Data Centers," 2012. Kong, et al. Expires October 20, 2016 [Page 9] Internet-Draft Routing Optimization with SDN in DC Networks April 2016 Authors' Addresses Qian Kong Beijing University of Posts and Telecommunications Email: kongqian@bupt.edu.cn Tao Gao Beijing University of Posts and Telecommunications Email: taogao@bupt.edu.cn Dajiang Wang ZTE Corporation Email: wang.dajiang@zte.com.cn Zhenyu Wang ZTE Corporation Email: wang.zhenyu1@zte.com.cn Jiayu Wang ZTE Corporation Email: wang.jiayu1@zte.com.cn Bingli Guo Beijing University of Posts and Telecommunications Email: guobingli@bupt.edu.cn Shanguo Huang Beijing University of Posts and Telecommunications Email: shghuang@bupt.edu.cn Kong, et al. Expires October 20, 2016 [Page 10]