One. What is the SDN?
SDN literally software-defined network, which is trying to get rid of the hardware limitations of the network architecture so that you can upgrade like, install the software as the network changes to facilitate more APP (application) can be quickly deployed to the network.
If the existing network as a mobile phone, that SDN goal is to make a network industry's Android system, you can install the upgrade on the phone, while also installing more and more powerful mobile phone APP.
Over the past 30 years, IP network has been fully distributed, distinguished itself, solve a variety of customer needs, today SDN is to achieve better and faster customer needs in the future. We do not have any demand by traditional methods can not do, just SDN done faster, better, easier.
SDN is the essence of network software, improve network programmability, is a reconstruction of the network architecture, rather than a new feature, new features. SDN network architecture than the original better, faster, easier to implement various features.
two. SDN solve the problem?
The viability of a strong IP network, thanks to its distributed architecture. IP look at history, the year after the US military hopes suffered nuclear attack, the entire network can self-recovery, so that you can not allow the network centralized control, can not exist in the central node, the central node in this otherwise throw a nuclear bomb, the whole network will Bye. It is precisely this fully distributed architecture has led to a number of problems:
Now look at IP network management and more complex, give an example of operators to deploy VPN: To configure MPLS, BFD, IGP, BGP, VPNV4, to bind the interface ... and needs to be configured on each PE; when adding a new PE when, also you need to go back to modify each PE involved.
Now the manufacturers of network devices are too complicated. If you're ready to become a knowledgeable equipment vendor, you need to know the command line more than 10,000, and the number is increasing. If you are ready to become IP-guru, you need to read the relevant RFC 2500 network devices papers If one day's reading one, you know to see how long can read? More than six years! And this is only 1/3 of the entire RFC, their number is increasing.
In addition, these agreements are standard in addressing a wide range of control plane needs, and these needs is to go through demands put forward, the definition of standards, interoperability testing, upgrade existing network equipment to complete the deployment, generally three to five years to a deployment. At this rate, already OTT Hold live their operations on the network needs to adjust a variety of fast network, we must find ways to solve this problem. Luckily, we have now found a solution to the above problems. Yes, that SDN! It is the best way to solve the above problem is now systemic.
three. Traditional network concept and architecture
Traditional network control and data forwarding:
traditional network is a distributed control architecture, each device includes a separate control plane, data plane.
Traditional network is a distributed control architecture:
1. The distributed control herein refers to traditional IP networks, a control plane protocol for the calculation and the data packet forwarding plane of the same device.
2. route calculation and topology changes, each device must re-route calculation process, and the process known as distributed control.
3. In the traditional IP network, each device is a separate network to collect information, calculated independently, and only care about their own routing.
4. drawbacks of this model is that all the equipment the lack of uniformity in the calculation of the path.
Traditional network management plane, control plane data plane:
Management plane: the management device (SNMP)
control plane: a routing protocol (IGP, BGP)
Data plane: forwarding (the FIB)
the OSS: Operation Support the System, the operation support system.
NMS: Network Management Server, network management server.
Traditional network architectures:
== into traditional network management plane, control plane and data plane ==.
Management plane includes management system and business equipment management system, device management system is responsible for the network topology, an interface device, the management device features, while sent to the next device configuration scripts. Business management system used to manage the business, such as business performance monitoring, alarm management business.
The control plane is responsible for network control, the main function for protocol processing and computation. Calculation for generating routing protocol such as routing information, the routing table.
The data plane refers to the device to complete processing user traffic and forwarding according to an instruction generated by the control plane. E.g. router generates a routing table of the routing protocol of the received data packet forwarded from the outgoing interface.
Traditional network limitations:
lack of the ability to flexibly adjust the flow path.
Network protocol complexity, operation and maintenance more difficult.
The new network upgrade business is slow.
Conventional network management system is typically deployed as a management plane, control plane and data plane and distributed to run on each device.
Adjust the flow path needs to be configured on the network element traffic policies to achieve, but for large-scale network traffic to be adjusted, not only tedious and very easy to failure; of course, can also be achieved through the deployment of TE tunnel traffic adjustment, but the TE tunnel the complexity of skilled personnel for maintenance demanding.
Traditional network protocols more complex, there are IGP, BGP, MPLS, multicast protocols, and growing.
In addition to the standard equipment manufacturers protocol has some proprietary protocol extension, not only the operation command range, and interface devices from different manufacturers are quite different, complicated operation and maintenance.
As the traditional network control plane device is closed, and equipment from different vendors implement mechanisms may be different, so deploying new features may result in a longer period; and if the need for equipment to upgrade the software, you also need operate on each device, greatly reducing efficiency.
four. SDN Overview
SDN (Software Defined Netrork) software-defined network.
In 2006, Stanford University professor Nike Mckewn-led team put forward the concept OpenFlow, and based programmability OpenFlow technology network (OpenFlow is to achieve an agreement of SDN), is as flexible networks like software programming, SDN technology came into being students.
SDN defined in
the definition of SDN is its literal meaning, separate control and forwarding, management and control of the separation is only a means to meet the SDN, the OpenFlow only one protocol to meet the SDN
SDN free
classified SDN difference lies in its implementation is the control and forwarding separation or separation management and control
SDN Category:
Separate control and forwarding (ultradistributions)
management and control the separation (broad)
SDN three main features:
Separation turn control: a control plane network element controller is responsible for calculating protocol, generating a flow table; plane only forwarded on the network device.
Centralized control: control NE device and the centralized management table hair flow, thereby eliminating the need to operate the device one by one, only need to configure the controller.
Open interfaces: third-party applications only need to define a new network functionality programmatically through an open interface provided by the controller, and then run it on the controller.
== SDN controller is neither a network nor a planning tool: ==
NMS fails to achieve the separation transfer control: network management is only responsible for managing the network topology, alarm and performance monitoring equipment, to deliver the configuration scripts and other operations, but these still need to control the plane's equipment responsible for generating the forwarding entry.
And a controller planning tools for different purposes: the planning tool for planning the next send some entries, these entries are not used for forwarding router, a network element parameters to the control plane and services, such as IP addresses, VLAN like. Delivered by the control flow table entry is used to forward the packet repeater.
Fives. SDN network architecture
SDN is a reconstruction on the traditional network architecture, from distributed control network architecture is reconfigurable network architecture of centralized control.
SDN network architecture of three layers:
Application Layer: This layer is intended to reflect the user's upper various applications, such applications layer called collaborative applications, typical applications include OSS (Operation support system operations support systems), OpenStack like. Traditional IP networks also has forwarding plane, control plane and management plane, SDN network architecture also comprises three planes, but the conventional IP network is a distributed control, and the lower SDN network architecture is centralized control.
Layer Control: the control layer is the control center of the system, the internal network is responsible for switching and routing of traffic generation path boundary, and is responsible for handling network status change event.
Forwarding layer: forwarding layer mainly composed of basic forwarding network, this layer is responsible for executing the user data is forwarded by the repeater lines and connectors, forwarding entry is required in the process generated by the control layer.
NBI: open controlled by controlling the application layer and layer communications interface, the API application layer, the forwarding function control apparatus
Southbound interface: control interface and data communication layer, by the controller issues OpenFlow flow table or other protocols.
SDN network deployment
network Underlay of
all forwarding behavior by the controller through OpenFlow protocol or custom protocol BGP will be transferred next published issue transponders, transponder only perform an action, there is no separate control surfaces
Overlay network
such a network repeater transmission equipment generally does not support OpenFlow, custom or proprietary protocols can not be deployed when necessary to use the tunnel technology, network infrastructure network or traditional form, playing with each node by the routing protocol, but in the access point server, only by tunneling the data packet encapsulation or decapsulation. Traditional networks see is the normal data packets can be forwarded. Tunneling actually messages vest, confuse network equipment, so that when the device one of us, but in fact the message hearts are the virtualization heart. Now generally used only Vxlan, GRE, NVGRE and other tunneling technologies, and these new agreements, also need to upgrade the existing network equipment to support (network devices do not support the above protocols). Wearing a vest dull able to add new features without a large transformation, but will undoubtedly reduce network performance.
six. SDN value
Rapid innovation network service:
SDN programmability and openness, so that we can quickly develop new network services and accelerate business innovation. If you want to deploy new services on the network, can realize the network for fast programming by software modification SDN, rapid business on-line.
SDN key local networks to increase the network architecture of a SDN controller, the original distributed control plane concentrated on a SDN controller from the centralized controller to achieve centralized control of the network. SDN network architecture includes three basic characteristics: the separation switch control, centralized control, open interface.
SDN by adding a centralized network SDN controller, you can simplify network and rapid business innovation. But the essence of the technical principles through the process of SDN network controller software to improve network programmability. Still contains communication management plane plane, the control plane and data plane, the network architecture just SDN three functional planes were reallocated system, the traditional network control plane is distributed, distributed on each forwarding device, the network SDN architecture is the distributed control plane concentrated within a SDN controller, centralized control, and management plane and data plane and there is not much change.
SDN network with fast network innovation, if this valuable new service is retained, no value can be quickly off the assembly line. Unlike traditional networks as a new business line to go through the needs presented, discussed and developers to define a standard protocol, then upgrade all network devices on the network, after several years to complete a new business. SDN enables new business on the line speed from a few years or a few months to upgrade faster.
Simplify network:
SDN network architecture simplifies the network, eliminating many IETF protocols. Decline in protocols, which means learning costs, operation and maintenance cost reduction, service deployment rapidly. This value is mainly due to centralized network control and turn control under separate SDN network architecture.
Because the network under centralized control network architecture SDN, the SDN is controlled by the controller internal network basically not required many protocols, such as RSVP protocol, the LDP protocol, an MBGP protocol, the PIM multicast protocol and the like. The reason is that the path established within the network and all of the controller calculation is completed, the controller calculates the flow table sent directly to the repeater it does not need the protocol. Future large number of traditional things will disappear to the agreement, while the north-south agreement will control protocols such as Openflow constantly evolved to meet the needs of SDN network architecture
White card of network equipment:
based SDN architecture, if standardized interface between the controller and the transponder, such as OpenFlow protocol matures, so white card network equipment will be possible, such as a dedicated chip suppliers OpenFlow forwarding, control vendors, etc., which is the so-called vertical integration from development to system level integration.
Vertical integration is supplied from a manufacturer to the hardware to the software services. The level of integration is the division of labor system level, every component manufacturers have a complete product, and some integrators to integrate their sales. Horizontal division of labor in favor of independent evolution and updating various parts of the system, rapidly evolving, promote competition, to promote the purchase price decline of the individual components.
Business Automation:
at SDN network architecture, due to the ownership of the entire network controller, the network service automation is granted, no additional configuration of the system decomposition. In the SDN network architecture, SDN controller can complete their network service deployment, providing a variety of network services, such as L2VPN, L3VPN, etc., shielding the details of the internal network, providing network services automation capabilities.
Traffic network path optimization:
usually the path of the traditional network selection based on calculated by the routing protocol "optimal" path, but the results could lead to traffic on the "best" path congestion, other than "optimal" path idle. When SDN network architecture, network traffic SDN controller may adjust the status of the intelligent network traffic path according to improve network utilization.