Translation guide
A logical connection in a network that makes it appear as though a dedicated physical path exists between two endpoints.
A logical path through a packet-switched network that simulates a dedicated physical circuit.
Standard technical term. 仮想 means 'virtual' and 回線 means 'circuit/line'.
このネットワークでは仮想回線が使われている。
Virtual circuits are used in this network.
仮想回線を確立するにはシグナリングが必要だ。
Signaling is required to establish a virtual circuit.
Katakana loanword from English. Common in IT contexts, but 仮想回線 is more standard in formal documentation.
ATMはバーチャルサーキットを使う技術だ。
ATM is a technology that uses virtual circuits.
Sometimes used interchangeably, but コネクション is less precise than 回線 for 'circuit'. More common in certain vendor documentation.
このプロトコルは仮想コネクションをサポートしている。
This protocol supports virtual connections.
In everyday conversation, 'virtual circuit' is rarely used. The term is almost exclusively technical. If you are not in a networking context, you probably need a different expression.