I see often those three terms (and even some others, but I do not remember them for now) used when it's about talking about a network interface or a network flow.
Are those three interchangeable, or there is a slight difference between them?
2 Answers
As so often with human language, differences are not absolute but may show up depending on context.
Let me give you an example: A server Op might call his networking counterpart and say something like 'I see a lot of incoming packets, but none of them are really inbound - might there be a problem with vLAN assignment?'. In this case, he would use the terms incoming and inbound to distinguish between packets seen on the NIC and packets really relevant to the server.
The same engineer might most likely use both words interchangeably when talking to his server software counterpart, to whom irrelevant packets just don't matter - on the socket layer they "just aren't there".
In short: While all three terms describe the fact, that network packets arrive on a network port, they might carry subtle differences, if used to distinguish between different classes of packets.
answered Apr 28, 2020 at 18:18
This is the cleanest explanation of it that I've seen:
"Inbound / outbound applies to servers and hosts, which is where the packets are bound to go. Ingress / egress applies to switches and routers where the packets are only passing through."
