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1、Sdn和传统网络的区别SDN and traditional network the main difference lies in their different network architectures. In traditional network architecture diagram, the most important thing is to control layer and data layer separation. Each level has different tasks, layer with layer provides the data forwarding
2、, routing functions. Here, the control layer is responsible for the equipment configuration of the routing and data flow procedures. When you manage a switch, you are actually in the deal and switches control layer. Like a routing table, spanning tree protocol and all these things are calculated by
3、the control layer. These tables built from such as BPDU (bridge protocol data unit, used to run the STP switches to exchange information between true), the Hello message such as frame relay, according to these news frame, switches to determine the available forward path. Once the packet forwarding p
4、ath, the path information will be sent to the data layer down, usually stored on hardware. Data level usually choose the latest by the control level for message forwarding path information transmission to come over. This model is very efficient in traditionally, the decision-making process of hardwa
5、re is very fast, the overall delay controllable and control plane can handle heavy configuration requirements. There are no problems with this approach, we focus on scalability. In order to prove the scalability problem, with our quality of service (QoS) as an example. QoS allowed according to the c
6、haracteristics of the frame, according to the requirements of the scheduling, priority forward specific data frames. This to some extent reduced the specific traffic congestion in the network data transmission delay. Delay-sensitive, for example, voice and video traffic is classified as high priorit
7、y and forwarded to ensure that the user experience. Traffic priority is usually based on the level of service (CoS) of a data frame or distinguish service code point (DSCP) tag. The frame must be unified in the data frame into the network, then the corresponding rules must also be set in the network
8、, the demand in the traditional multiple exchange network becomes awkward, because each device needs to have the same configuration information. To illustrate the current network management challenges, we consider that each port on each device node in the network, the administrator needs to be confi
9、gured individually, such work is very time-consuming and error-prone and awkward. In addition, in the data classification and appropriate routing network challenges still exist. For example, now we have two kinds of completely different data traffic, is a kind of iSCSI traffic, is a kind of voice tr
10、affic. ISCSI as the storage flow, usually packets are full size, and sometimes there will be a huge data frames; While voice traffic is usually in a small packet transmission. In addition, there are different two kinds of traffic transport demand: voice traffic is sensitive to delay, this is to ensu
11、re the quality of voice communication, the iSCSI is sensitive to low latency, but need more bandwidth. Almost without any tools in the traditional networks can differentiate between the two kinds of flow path and choose different depending on the type of traffic data to meet the specific needs of tw
12、o kinds of traffic. Is SDN hope to solve all these problems. 1. SDN architecture According to the definition of ONF, SDN is divided into infrastructure layer, control layer and application layer, as shown in figure 1. Virtualization in infrastructure and control layer on two levels, the equipment le
13、vel of virtualization, such as a physical support multiple logical switch; Which realizes the network level virtualization, first is SDN controller will of the entire network as a logical super switches on management control, the second will be the physical resources further according to the port, t
14、he media access control (MAC) address, IP address and other information is divided into multiple virtual network in accordance with traditional practice in the field of communication, in the architecture diagram below for south, above for the north, so the interface between infrastructure and forwar
15、d layer called south interface. ONF standardized is OpenFlow protocol, the Internet engineering task force (IETF) routing system interface (rs) protocol is being worked out. Control layer and application layer called north to interfaces, the interfaces between the industry mainstream implementation
16、is based on the hypertext transfer protocol (HTTP) RESTful interface, the concrete programming interface differ according to the different application scenarios. Figure 1 SDN layered architecture enlarge images In a more generalized SDN architecture, control layer and business choreography layer, th
17、e main resources of SDN domain between the unity of the unified management, SDN network and other resources scheduling, such as 0 penstack + SDN data center solutions. Unified dispatching calculation, network and storage resources, it is equivalent to the business choreography layer of SDN. Standing
18、 in the point of view of SDN, how control layer is divided into the concrete behavior of vendor application solutions, implementation, as the transmission control protocol, network protocol (TCP/IP) dont care about the application layer further layered design, referred to as the application layer. S
19、tanding in the whole network architecture level SDN, industry exist different opinions: (1) SDN only regional network renovation, to SDN control domain as a super equipment. SDN transverse interface does not change the original network, border gateway protocol (BGP)/multi-protocol label switching (M
20、PLS) is still valid. (2) SDN control field definition specifically/enhanced SDN east-west between interfaces, SDN as the entire network control plane. The author believes that the first scheme is more realistic, conducive to the smooth evolution of the network. The second solution of east-west inter
21、face can either through the expansion of existing BGP, MPLS protocol implementation, or can be realized through the north to the interface in the aspect of business choreography, if you want to define more specialized SDN east-west interface, although it is possible to enhance the ability of the who
22、le network, but also increase the difficulty for deployment, the industry is under exploration. 2. The ZENIC architecture and key technology to realize control surfaces Implementation is based on the existing open source from academia SDN controller OpenFlow agreement, the forward model is also boun
23、d to a specific OpenFlow protocol version . For the commercial system, must consider the entire product life cycle agreement the compatibility of the interface, consider the difference of different application scenarios and more manufacturers, the difference of multi-protocol interface, therefore SD
24、N control surfaces must be set a compatible version OpenFlow, a variety of forward control protocol and the different ability of abstraction, we call forwarding abstraction layer (FAL), on top of this for the network operating system (NOS) core and the application layer provides the interface is ind
25、ependent of the specific agreement and the ability of hardware. In OpenDaylight, this level is called a business abstraction layer (SAL) . This paper implemented a SDN controller - ZENIC, its architecture is shown in figure 2. Figure 2 top-down mainly includes protocol stack, driving and forward abs
26、traction layer, NOS kernel and application layer. Figure 2 ZENIC architecture enlarge images 2.1 forward abstraction layer and drive layer Forward forward abstraction layer defines a unified control interface, including the abstract forwarding state below, turning ability, hardware resources, publis
27、hed, read/operation such as statistics, equivalent to drive the base class. Forward abstraction layer also forward management face driver instance, according to the forwarding plane when access to the basic ability to negotiate the different instances of drive, will forward the control connection is
28、 bound to the corresponding driver instance. Each specific device driver implementation forward abstraction layer interface, complete different interface protocols and hardware ability to forward the unification of the abstraction layer adaptation. From the point of view of control surface and the u
29、pper applications, FAL transmit manipulation interface provides a unified, but due to the forwarding the capacity difference is bigger, the application for forwarding the operation there is the possibility of failure, therefore FAL need to provide application forward interface surface ability get/ne
30、gotiation. ZENIC is implemented for OpenFlow1.1 adaptive negotiation / 1.2/1.3. 2.2 the network operating system kernel layer NOS kernel layer is the management of the network, the system resources, including topology management, host, interfaces, resource management, publication management, and man
31、age the physical topology, virtual topology, turn in a network of information database, etc. In general, the kernel layer, there is no default forward network logic to handle, but to preserve the accurate network topology, the resources status and storage, synthesis of the published, accept the appl
32、ication for subscription and applications of network, resource state for network resources, forward logical operation. Topology management, the implementation of the current can be implemented based on standardization of OpenFlow cycle distributed across the link detection is based on controller mes
33、sage, Ethernet is generally based on link layer discovery protocol (LLDP) implementation. Forward this implementation has the advantage of surface completely without perception, the disadvantage is that more link and shorter test timer, controller of high overhead. Another way is to have the forward
34、ing plane maintenance link test timer, to detect, report will state that the implementation has the advantage of control surface overhead is small, the disadvantage is that need to be forwarded surface have certain default logic. The kernel layer is not only to maintain the network nodes, topology s
35、tatus, but also need to collect the basic host location, status, which can be applied to provide a complete network view, further make forwarding, business decisions. Network virtualization should be built-in support for SDN controller. Should be built-in support for virtualization. Virtualization i
36、s the forwarding plane resources first division and isolation, such as according to the ports, logic, the host MAC address and IP address section for the division of the virtual network, the second is the virtual topology for customer/application permissions management. OpenFlow flow table model as
37、well as for switches, flattening management unified view has brought about many problems, including switching hardware complexity, not flexible, host, and to be tightly coupled. in the ZENIC system, inline network management as one of the kernel services, decoupling access networks and the Internet.
38、 The kernel management of Internet network encapsulation format, upper application need only decision SDN control domain two access port position and strategy. The kernel to calculate the complete end-to-end path, and then forwarding decision by access side is mapped to the interconnection network p
39、ath packaging labels. ZENIC supports a variety of Internet encapsulation format, including MPLS, virtual local area network (VLAN), etc., the next step is to support the virtual local area network (LAN) extension (VXLAN)/generic routing encapsulation protocol (GRE). This mode of access to the Intern
40、et, the application of completely without awareness, focusing on the host access side strategy. At the same time within the network management itself also can open interface, support custom routing algorithm and strategy. 2.3 north to application programming interface North to application programmin
41、g interface (API) in the different application requirements in the scene is different, also have to the requirement of packaging. If the network ability of atom exposed to the application, it is possible to form a unified API, but due to lack of encapsulation and ease of use, application programming
42、, implementation complexity is higher. Such as manufacturers realize the equipment level of open API up to more than 700, covering almost all protocols and equipment features, but for SDN, there will be at least two types of applications, different requirements: (1) professional network applications
43、 Customized specification is high, need more details of the API, to the operation of the underlying network control ability is strong, such as routing protocols, custom tailored development intensification of traffic scheduling. (2) the common application The network as a service, just request netwo
44、rk to provide service for application, dont care about the network details. In the latter case, north to interface to encapsulate A few best model and interactive service interface is simple, and easy to understand, such as to create A network request from switches A port to the switch port 2 B A l
45、lGb/s bandwidth guarantee access, rather than by the application turns published and distributed to the path switches individually corresponding queue configuration parameters. There is a north to the ideas of the interface is defined by the application itself to the demand of the network and operat
46、ion interface, network vendors plugin to realize the application of network interface. Typically it is Quantum components, it defines the network API, provided by the various manufacturers Quantum plug-in - to control In own SDN controller or network devices. This architecture is equivalent to the S
47、DN north interface standardization work up to the application, network adapter application requirements. Both advantages and disadvantages of each train of thought in north interface defined by SDN is idealized, trying to solve all problems, but its not possible for the network to understand the app
48、lication requirements, standardization of advancing the work is relatively difficult, but also it is difficult to guarantee ease of use; Application driven model facilitates the SDN landing, but exchange between applications and multivendor network to a greater cost. ZENIC provides basic fine granul
49、arity of the underlying API, while providing encapsulation of API, virtual network has provided it is Quantum plug-in - In access to it. 2.4 distributed processing algorithm The distributed architecture of control surfaces and SDN separation architecture brought forward control state synchronization overhead, accurate SDN global view can ensure the accuracy and real time of decision, for a applications such as load balancing can improve resource utilization, but need more frequent informat
