Browsing by Author "Chakraborty, Suchandra"

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A Low-Latency Multipath Routing Without Elephant Flow Detection for Data Centers
(2016)
Chakraborty, Suchandra
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Chen, Chien
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資訊工程學系
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Department of Computer Science
Multipath routing in data center has been studied intensively in recent years in order to minimize the finish time of data transfer or the latency of message sending. Existing scheme of splitting traffic at the granularity of packets can cause reordered packets within a TCP flow. Another alternative scheme of splitting traffic at the granularity of a flow avoids packet reordering but may increase latency as it does not differentiate between elephant and mice flows. A newer efficient approach is to split elephants down into many mice flows, and distribute them uniformly at random over all paths. However, elephant detection is mandatory and the performance is largely depends on accuracy of the elephant detection. We propose, a simple yet effective multipath routing that leverage the same idea of splitting elephants down into many mice flows but without any farther requirement of elephant flow detection by using the hard time-out based flow removal feature of OpenFlow switches. Furthermore, we integrate a VLAN based routing scheme to addresses the challenges of cost-effective scalability. As per our simulation using mininet, we found a 44% reduction in overall flow completion time (FCT) compared to TinyFlow and 32% reduction in the consumption of flow table entry resources inside of aggregate switches in datacenter.
A Software Defined Network Architecture for GeoBroadcast in VANETs
(2015)
Liu, Yu-Chun
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Chen, Chien
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Chakraborty, Suchandra
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資訊工程學系
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資訊技術服務中心
This paper proposes a Software Defined Network (SDN) architecture for GeoBroadcast in VANETs. We have implemented a component to automatically manage the geographical location of Road Side Units (RSUs), which are used as a basis for our GeoBroadcast routing. GeoBroadcast in a vehicular network supports periodic broadcast messages from a source vehicle to the destination vehicles that are located in a specific geographical region. In existing Intelligent Transport Systems (ITS), the GeoBroadcast mechanism can be implemented using traditional IP networking. Typically, every periodic warning messages received at nearest RSU from the source must be routed to the control center in ITS, where it is redirected to every other RSUs, that are located in the destination geographical region for broadcasting. As a result, huge overhead in the control center is produced and higher network bandwidth is consumed. However, in our SDN based GeoBroadcast mechanism, the first warning message received by the source RSU is sent to the SDN controller as a packet-in message. The SDN controller will decode the packet-in message and use topological and geographical information to set up the routing paths to the destination RSUs, by installing appropriate flow entries on the corresponding RSUs and intermediate switches, for the following periodic warning messages that are to be broadcasted. As per our simulation with OpenNet a significant reduction by 84% in controller overhead, 60% in network bandwidth consumption, and 81% in latency are achieved.
A Zero Flow Entry Expiration Timeout P4 Switch
(2018-01-01)
He, Cheng-Hung
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Chang, Brian Y.
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Chakraborty, Suchandra
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Chen, Chien
;
Wang, Li Chun
Existing OpenFlow based flow expiry mechanisms rely on a fixed timeout after which the switch proactively removes the flow entries from its flow table. Assigning an appropriate value to this timeout presents a tradeoff between efficient flow table utilization and controller overhead.We propose a simple addition of a zero flow entry expiration timeout scheme to idle timeout mechanism on a P4 based switch that identifies the last packet of a TCP flow, and removes the corresponding flow entry from the flow table. It enables connections to be deleted from the flow table right after it finishes, instead of waiting to expire after it reaches the timeout threshold and causing unnecessary flow table occupation.