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  • Controller to controller communication in distributed OpenFlow Network

    By -Soumya Ranjan Parida

  • Agenda Introduction Motivation Architecture C2C communication protocol Advantages / disadvantages Conclusion

  • Introduction SDN is a new and increasingly

    popular network architecture Main aim is to decoupling control

    plane and data plane OpenFlow is a preferred protocol

    SDN network

    Control Plane

    Data Plane Application layer for management

    and services(Ref:http://www.tcs.com/SiteCollectionDocuments/White%20Papers/Inter-SDN- Controller-Communication-Border-Gateway-Protocol-0314-1.pdf)

  • Motivation Scalability issue

    A single controller might not be enough to service all nodes in the network. It would become a bottleneck in terms of processing power, memory, or input/output bandwidth. Bandwidth single point failure

  • Architecture-1Vertical Approach : Proposed by Deepankar Gupta and

    Rafat Jahan -Working @TCS IDEA : Master controller over the individual

    network controllers master controller, interfaces with the underlying

    controllers using RESTFul APIs.

    Though this approach can work for data centers,problems may arise if this model is to be scaled up in

    an enterprise spread across different locations and

    geographies. (Vertical Approach to Inter-SDN Controller Communication) (Ref:http://www.tcs.com/SiteCollectionDocuments/White%20Papers/Inter-SDN-Controller-Communication-Border-Gateway-Protocol-0314-1.pdf)

  • Architecture-1 Continue...Horizontal Approach :SDN east-west interface:Each controller can request for information or connections from its peers, that is, SDN controllers from other domains in the network.

  • Architecture-1 Continue ... The SDN east-west interface should

    be able to coordinate the path setup requirement across multiple SDN domains Controllers need to exchange

    information such as: Reachability update Flow setup, tear-down, and

    update requests Capability Update

  • Protocols: A session needs to be established between the two controllers by using either BGP2 or Session

    Initiation Protocol (SIP) over Transmission Control Protocol (TCP) to exchange information. Recommended Approach :BGP

  • Architecture-2Disco Architecture : DISCO is a distributed multi-domain

    SDN control plane which enables the delivery of end-to-end network services. DISCO controller is in charge of a network

    domain and communicates with neighbor domains.

    composed of two parts Intra-domain Inter-domain

  • Architecture-2 Continue...Intra-domain : Monitor the network and manage the flow prioritization which help controller to compute the

    route of priority flows.

    dynamically react to network issues (broken link, high latency, bandwidth cap exceeded, . . . ) by redirecting and/or stopping traffic according to the criticality of the flow.

    Inter-Domain :A DISCO controller communicates with neighbor domain controllers to exchange aggregated network-wide information.

  • Protocols : SDN controllers provide OpenFlow driver to implement the OpenFlow protocol, a switch manager and host manager to keep track of the different network elements, and link discovery implementing LLDP (Link Layer Discovery Protocol).

    Messenger :

    implements a unique control channel between neighboring domains. Messenger provides an open communication bus on top of which any agents can be plugged

    dynamically. It can subscribe to topics published by other agents and start publishing on any

    topic. Advanced Message Queuing Protocol (AMQP) as a base for the implementation of Messenger.

  • AMQP Protocol open standard and a thin application layer protocol for message-oriented middleware.

    offers built-in features for message orientation, queuing with priority, routing (including point-to-point and publish-and-subscribe), reliable delivery and security.

    Advantage :Being lightweight, highly controllable and software-oriented ,can be used for cloud management.used in OpenStack for loosely coupled communication between the different components.

    Disadvantage :it makes the implementation of Messenger more complex.

  • Architecture-2 Continue...Agents :support QoS routing and reservation functionalities4 Main agentsConnectivity agent : charge of sharing with all the other domains the presence of peering links with neighboring

    domains. sends information only if a new domain is discovered or a peering link changes. Store information in extended database.

    Reachability agent :takes care, like RSVP, of inter-domain flow setup, teardown and update request including application capability requirement such as QoS, bandwidth, latency, etc.

  • Architecture-3DevoFlow: Motivation : SDN / OpenFlow can enable per-flow management However What are the costs and

    limitations? always collecting all flows stat.s? what about controllers scalability ?

    Proposal : DevoFlow to enable scalable flow mgmt by balancing

    Network control Statistics collection Overheads Switch functions and controller loads

    DevoFlow uses 1053 times fewer flow table entries at an average switch, and uses 1042 times fewer control messages

  • Architecture-3 Continue.. The controller maintains control over only targeted significant flows and has visibility over only

    these flows and packet samples. DevoFlow is designed for simple and cost-effective hardware implementation

    Our design principles are: Keep flows in the data-plane as much as possible. Involving the control-plane in all flow setups

    creates too many overheads in the controller, network, and switches. Maintain enough visibility over network flows for effective centralized flow management, but

    otherwise provide only aggregated flow statistics. Simplify the design and implementation of fast switches while retaining network


  • Architecture-3 Continue..Rule Cloning : Under the standard OpenFlow mechanism for wildcard rules, all packets matching a given rule

    are treated as one flow. action part of a wildcard rule with a boolean CLONE flag. If the flag is clear, the switch follows the standard wildcard behavior. Otherwise, the switch

    locally clones the wildcard rule to create a new rule in which all of the wildcarded fields are replaced by values matching this microflow, and all other aspects of the original rule are inherited.

    Subsequent packets for the microflow match the microflow-specific rule, and thus contribute to microflow-specific counters.

  • Architecture-3 Continue..Local actions: Certain flow-setup decisions might require decisions intermediate between the heavyweight

    invoke the controller and the lightweight forward via this specific port choices offered by standard OpenFlow.

    local routing actions that a switch can take without paying the costs of invoking the controller.

  • Advantages/DisadvantagesAdvantages : Bandwidth on Demand Content Delivery Networks :Source SDN controller will need to communicate with the other

    SDN controllers within the network to negotiate a path to the best possible CDN server that can meet the customer's QoS needs.

    Scalability. A single controller might not be enough to service all nodes in the network. It would become a bottleneck in terms of processing power, memory, or input/output bandwidth.

    Fault tolerance. minimize overhead

    Disadvantages: issues in security and trust mechanism

  • Reference[1] Distributed Multi-domain SDN Controllers (http://arxiv.org/pdf/1308.6138.pdf)[2] Inter-SDN Controller Communication: Using Border Gateway Protocol (http://www.tcs.com/SiteCollectionDocuments/White%20Papers/Inter-SDN-Controller-Communication-Border-Gateway-Protocol-0314-1.pdf)[3] DevoFlow: Scaling Flow Management for High-Performance Networks (http://conferences.sigcomm.org/sigcomm/2011/papers/sigcomm/p254.pdf)

  • Thanks You

    Queries ?

    Slide 1AgendaIntroductionMotivationArchitecture-1Architecture-1 Continue...Architecture-1 Continue ...Protocols:Architecture-2Architecture-2 Continue...Protocols :AMQP ProtocolArchitecture-2 Continue...Architecture-3Architecture-3 Continue..Slide 16Architecture-3 Continue..Advantages/DisadvantagesReferenceSlide 20