IPv4 addresses are nearly exhausted worldwide. For some time until IPv6 becomes pervasive as an ultimate solution, deployment of Carrier Grade NAT (CGN) devices becomes necessary, especially in the mobile carriers' networks which anticipate a large and growing number of new users. In this context, we tackle the evaluation of the impact of inserting a CGN device in the network, and in conjunction with the mobile network communication delays. We compare the Connection Establishment Rate (CER) with or without a CGN device, also with or without the emulated mobile network communication delays. Against our anticipation, the types of time-varying mobile network delays do not have a significant impact on CER. The effect of the changing delay fades away in the aggregation of many user traffic at the core part of the network, even though the time-varying mobile network communication delays are individually and separately emulated for each user. To the best of our knowledge, this is the first to study the relationship between the CGN performance and the mobile network's communication delays. The result suggests that modeling the aggregate traffic trend Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org.

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We propose a novel distributed denial of service (DDoS) attack suppression system that significantly reduces discarding of normal traffic (i.e., the traffic from Internet of Things (IoT) devices that are not infected with a malware) with a small number of equipment by controlling the priority of frames in a network accommodating IoT devices. Experimental results showed that our proposed system prevented the discarding of the normal traffic in a few seconds when attack traffic was generated by a traffic generator. Moreover, we constructed Mirai-based DDoS attack traffic and experimentally demonstrated that the discarding of the normal traffic was prevented in 30 milliseconds in our proposed system. We also confirmed that the attack traffic detected by a DDoS protector that was installed in front of an IoT server was autonomously blocked at the switches that the traffic came through from the IoT devices (i.e., the entrances to a backbone network) by integrating various vendors' products.