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Handling an FTP Session During a Failover

The art of building reliable network and computing infrastructures is deep and complex. Generally, networks are architected to contain multiple redundant paths between any data source and any data sink. Those redundant paths may exist at multiple layers of the OSI protocol stack, with each implementation choice protecting against a certain class of failures and introducing its own set of complexities.

In your question, you ask specifically about failure of a network link. There are many ways to protect against this type of failure. Between two different network devices (switches or routers, for instance), there may be Layer 1 alternatives such as link aggregation, Layer 2 alternatives such as spanning tree (with or without the various rapid reconvergence variants), or Layer 3 alternatives such as various routing protocols (OSPF, BGP, etc.). Between a host and the network, options typically include Layer 1 options such as link aggregation or Layer 3 options such as providing a host with dual network interfaces.

Each of these various alternatives is agnostic with respect to application-layer protocols such as FTP; they work equally well with HTTP, SMTP, etc.

Dave Roberts, Co-founder and Vice President of Marketing and Strategy, Inkra Networks