Abstract
This work presents a strategy to scale out the fault-tolerant dynamic host configuration protocol (DHCP) algorithm over multiple interconnected local networks. The proposed model is open and used as an alternative to commercial solutions for a multi-campus institution with facilities in different regions that are interconnected point-to-point using a dedicated link. When the DHCP scope has to be managed and structured over multiple geographic locations that are VPN connected, it requires physical redundancy, which can be provided by a failover server. The proposed solution overcomes the limitation placed on the number of failover servers as defined in the DHCP failover (DHCP-F) protocol, which specifies the use of one primary and one secondary server. Moreover, the presented work also contributes to improving the DHCP-F specification relative to a number of practical workarounds, such as the use of a virtualized DHCP server. Therefore, this research assumes a recovery strategy that is based on physical servers distributed among different locations and not centralized as clustered virtual machines. The proposed method was evaluated by simulations to investigate the impact of this solution in terms of network traffic generated over the VPN links in order to keep the failover service running using the proposed approach.
Highlights
In large network architectures, the dynamic host configuration protocol (DHCP) service plays a strategic role
This paper describes the architecture and algorithms that are needed to scale out the DHCP failover (DHCP-F) over a virtual private network (VPN) or other kinds of large-scale private communications over the internet, as most enterprises and university campuses have one or more links that connect a local network to the Internet
This number allows for the same time delay between the responsive server and the consecutive one, but the others will have a gap that is twofold in the maximum client lead time (MCLT); this is important for facilitating a conflict-free transition between servers, as the occurrence of just one MCLT between them could be dangerous since the knowledge of time between the last update is not fixed, as described in Algorithm 1, which shows that the bind update (BNDUPD) message can be delivered with a time that differs from that of client–server acknowledgment
Summary
The dynamic host configuration protocol (DHCP) service plays a strategic role. In this scenario, links with high redundancy are widely deployed to avoid a loss of internet connection. In order to create a large DHCP scope, structures such as virtual local area networks (VLANs) are distributed over VPNs, and the redundancy mechanism of the DHCP-F specification is limited to just two servers. The proposed solution is not generalized (as was the case for Fan and Droms [8]) for any number of failover servers; instead, it is restricted to a pre-ordered number of failover servers from a real case of multiple campus networks which are geographically separated but interconnected with the same IP assignment logic.
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