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Ports operate a different layer in the OSI model - the transport layer, not the network layer (which IP operates on). Ports are TCP and UDP concepts (e.g., a di
by cnorthwood 8y ago
Ports operate a different layer in the OSI model - the transport layer, not the network layer (which IP operates on). Ports are TCP and UDP concepts (e.g., a different application can bind to TCP port 443 than UDP port 443, as they're essentially different ports). Some protocols don't have ports at all, e.g., ICMP, which instead has a "type".
- jstarks 8y agoOK sure but TCP/IP was not designed to follow the OSI model.
- magicalhippo 8y agoSure, but so what? Imagine you could only bind services to their standard ports. What's the difference between a service running on my computer having a unique ip address, or my machine having a unique ip address and only running that service?
- cryptonector 8y agoCompatibility. Code written for layer 4 should be compatible even if layer 3 is changed. In practice much code had to be changed anyways, but the amount of violence applied to existing code was limited by not getting rid of ports. It's not just that either, but much else, including cognitive load.