Page 74 - ITUJournal Future and evolving technologies Volume 2 (2021), Issue 1

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 1

Fig. 10 – Flow chart of proposed method for two controllers.

domain. For each set of placement, the average latency of the switch). By partitioning the data‑plane into two
is computed following the same procedure as described clusters, the traf ic induced by data‑plane monitoring
above. (code‑named polling) is reduced. Speci ically, after
clustering, the controller sends and receives monitoring
7.2.2 Control‑plane signalling overhead and data from just a fraction of data‑plane nodes. To balance
failover the switch‑to‑controller placement, we activate the ONOS
mastership management module. This results in a more
The centralized control scheme adopted by SDN puts balanced monitoring load which we expect to further
the control channel at risk of incurring very high decrease control‑plane overhead.
signalling overhead generated during data‑plane
monitoring (e.g. Stats‑Request and Stats‑Reply) and To quantify the impact of switch‑to‑controller placement,
reactive low instantiation (such as packet‑In, packet‑Out we generate variable traf ic between two virtual hosts
and Flow‑Removed). In order to manage this rapid (the client connected to Johannesburg and the server
in lux of traf ic on the control channel, the following connected to Cape Town), a distance of 1399 km from
procedure is used: First we con igure a cluster of each other. This is carried out using the Distributed
two ONOS instances each managing a segment of the Internet Traf ic Generator (D‑ITG) tool. The transport
network. The cluster is con igured using the REST API protocol is set to UDP and the number of packets
of each separate ONOS. Upon data‑plane instantiation, per second is varied from 50 000 to 200 000 in
the switch‑to‑controller placement (in terms of the increments of 50 000. The packet size is set to 512
number of switches per cluster) is imbalanced. This is bytes. The link bandwidth was kept at 10 Mb/s.
because switch‑to‑controller placement is based solely The duration for the generation process is set to 5
on best effort (meaning the controller that completes minutes. The key performance indicators are delay,
the handshake with the switch irst, gets mastership jitter and packet loss all monitored at the server end.

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