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-2

Disco 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-3

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

limitations?❖ always collecting all flows’ stat.s?❖ what about controller’s scalability ?

Proposal :❖ DevoFlow to enable scalable flow mgmt by balancing

➢ Network control ➢ Statistics collection ➢ Overheads ➢ Switch functions and controller loads

❖ DevoFlow uses 10–53 times fewer flow table entries at an average switch, and uses 10–42 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

programmability.

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)

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