Hey!
There is no big philosophy since you keep in mind that Ingress/Egress originally explaining OSI L2 features. So the are always port related. First we had "dumb" L2 switches with only physical ports. Then a frame - mind NOT a packet - from a PC1 to the switchport fa0 in ingress and the same frame from fa24 to PC2 is egress. These concepts were later needed to explain OSI L2 enhancements like VLAN and QoS where different Tags were applied to the frame header and a decision had to be made where exactly to add / stripe them down. So at this point also even the logical interfaces like VLAN1 etc used this concept when a frame was bridged between two different VLANs.
Later on some started using the words for L3 which brought some troubles since there we have packets with IP header that are being routed and not switched.
And at the very latest some started using the words for edge routers / gateways, like egress for all outgoing connection (from perspective of the "insider", the LAN) and ingress for the incoming packets (ie, from MAN or WAN). I think there is where you basically catched the wave
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by: Rick_O_ShayPosted on 2009-11-05 at 12:13:12ID: 25753432
Generally speaking ingress and egress are relative to the port in question.
However, I think this is referring to it as it relates to the shaper function on that switch.