AWS安全组出口上的协议1意味着什么?

我理解 egress AWS安全组上的属性控制出站流量,但有人知道-1协议的含义吗?

resource "aws_security_group" "elb" {
  name = "example-elb”
  ingress {
    from_port = 80
    to_port = 80
    protocol = "tcp”
    cidr_blocks = [" 0.0.0.0/ 0”]
  }
  egress {
    from_port = 0
    to_port = 0
    protocol = "-1"
    cidr_blocks = [" 0.0.0.0/ 0"] }
}