Shortly after submitting my reply I had a similar thought but after some googling I cannot find any source that this kind of "port sharing" NAT is actually used. Looking at RFC 3022 "Traditional IP Network Address Translator" it looks like usually unique port numbers are allocated per connection. Maybe there are protocol subtitles or security implications that keep implementors from going with "port sharing" NAT?
My argument still stands in case all peers behind a common NAT router try to access the same IPv4 server (which may just happen with centralized services like youtube/facebook/google). It also stands in case UDP based services are used (stuff depending on a Cone NAT and using STUN like VoIP or online gaming).
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Shortly after submitting my reply I had a similar thought but after some googling I cannot find any source that this kind of "port sharing" NAT is actually used. Looking at RFC 3022 "Traditional IP Network Address Translator" it looks like usually unique port numbers are allocated per connection. Maybe there are protocol subtitles or security implications that keep implementors from going with "port sharing" NAT?
My argument still stands in case all peers behind a common NAT router try to access the same IPv4 server (which may just happen with centralized services like youtube/facebook/google). It also stands in case UDP based services are used (stuff depending on a Cone NAT and using STUN like VoIP or online gaming).