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which do not occur frequently, such as link status changes. EWBridge proposed in
this paper can also work in the HyperFlow architecture and substitute the WheelFS to
better synchronize the network view of each domain.
Onix [7] is a distributed controller for large scale production network. It uses the
Distributed Hash Table (DHT) to store the network information. Each controller just
stores a part of the whole network view. While EWBridge focuses on SDN domains
such as sub-networks within intra-domain networks, data centers and enterprise net-
works. The target of EWBridge is to achieve high performance and high available
network view synchronization. We will show later on, that in the above scenarios the
performance of EWBridge is better than DHT. Onix is a distributed controller, while
EWBridge is a mechanism to support different controllers/ NOSes with different local
network view storage systems working together. In such way, EWBridge can en-
courage third-parties to engage in contributing to the NOS and promote competition
and coexistence in the NOS's environment.
Previously, Yin et al. had proposed a message exchange protocol for software de-
fined networks across multiple sub-network domains named SDNi [5]. That proposal
only defined several basic messages such as the reachability information and the flow
setup/ tear-down/ update processes. But it did not describe how the message should be
stored and exchanged in a performance effective manner. In this paper we explore and
verify the east-west message exchange protocol.
3
East-West Bridge for SDN Peers
Fig. 1.
East-west Bridge for heterogeneous NOSes cooperation in SDN
EWBridge is a high performance network view exchange mechanism for multi-domain
networks. It is compatible with different third-party controllers/ NOSes and network
view information storage systems. We illustrate the EWBridge in Figure 1. The EW-
Bridge mechanism mainly includes the controller/ NOS discovery process, definition of
network view information in different scenarios, network view information storage and
transfer format, and high performance network view exchange mechanism.
