If you use an IP address in the connection, all connections connect to a single server which can be a bottleneck.

COP stands for Communications Processor. COP Discovery refers to the process of performing multiple DNS lookups to identify all the Teradata Database nodes that the client software could potentially connect to. Using cop address allows connections to round-robin over cop servers to connect each mapper to a different node. For example:

Laddered Concurrent Connect (LCC) occurs second, and uses the two-dimensional array as the list of possible IP addresses to choose from. The purpose of LCC is to make multiple TCP socket connect attempts in parallel. LCC provides 3-4x faster throughput with parallel connections.