By running multiple redundant copies of each service, one can use quick timeouts and retries to route around failed or unreachable services.

每个服务都运行多个冗余拷贝，短时间内超时，然后绕过失败或不可访问的服务进行重试。

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Or an destination unreachable message, when there is no route available such as when a line goes down.

或者，当没有可以使用的路径时，比如某条线路被关闭了，ICMP会发出无法送达目的地的信息。

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