RFC 3588:Diameter Base Protocol
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destination port


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... destination IP address (possibly masked) Protocol Source and destination port (lists or ranges) TCP flags ...
... destination IP address (possibly masked) Protocol Source and destination port (lists or ranges) DSCP ...


... traffic is "Initiate IPsec, from me to any, destination port Diameter"; for inbound traffic ...
... traffic, the policy would be "Require IPsec, from any to me, destination port Diameter". ...



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