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> when it is said "ICMP packet", "IPsec packet", "TCP packet" and so on, what is meant is "IP packet carrying the ICMP/IPsec/TCP protocol". But an "IP packet c

> when it is said "ICMP packet", "IPsec packet", "TCP packet" and so on, what is meant is "IP packet carrying the ICMP/IPsec/TCP protocol". But an "IP packet carrying TCP" is totally different from a "TCP segment", and so why the fuck is everyone trying to muddy the waters in this regard? Likewise, "an Ethernet frame with IP stuff in it" is not an IP packet. Because it's at a lower layer!!! Due to fragmentation, these higher protocol layers can be split up into two or more PDUs at lower levels. They are reassembled as steps to decoding the protocol. A TCP stream, made of multiple segments, will surely be split up across multiple IP packets. Even a single TCP segment is never guaranteed to map 1:1 with a single IP packet. That's why you can't equate them, and that's why it's idiotic to try and force the wrong PDU terminology in the wrong layer, because they simply don't match up, and you confuse newbies into believing these things are equivalent or interchangeable. They are not! A TCP segment is a thing in its own right. It is not equivalent to an IP packet with protocol 6. Why is that a crazy idea to y'all?

lxgr 2y ago
> A TCP segment is a thing in its own right. It is not equivalent to an IP packet with protocol 6. Why is that a crazy idea to y'all? Nobody is claiming they're the same in this thread, as far as I can tell. "TCP packet" is simply a pretty clear/unambiguous contraction of "an IP packet carrying TCP", or "an IP packet containing a TCP segment", to me.
adrian_b 2y ago
Yes you are right that an "IP packet carrying TCP" is totally different from a "TCP segment". Like I have explained, this is precisely the reason why we need two different terms, "TCP packet" and "TCP segment", to name the two different things. There exists no 1-to-1 mapping between TCP packets and TCP segments. It is frequent for a TCP segment to span multiple TCP packets. Muddying the waters would be if the same term would be used for the two different things. When two different things have two different names, the waters are clear. Likewise, there is a 1-to-1 mapping between the "Ethernet frame with IP stuff in it" and the IP packet contained inside the Ethernet frame (ignoring the distinction between complete IP packets and fragmented IP packets, which has been removed in IPv6). The IP packet is obtained by deleting or ignoring the Ethernet header & CRC, while the Ethernet frame is obtained by adding to the IP packet the Ethernet header and CRC. Because of the 1-to-1 mapping, there is no risk of confusion when using a term like "IP packet", regardless whether you speak about the IP packet alone, as existing in the memory before being sent or after reception, on about the IP packet as existing on the communication links or in some tool for network monitoring/sniffing, where it is encapsulated in the Ethernet frame. Similarly for an ARP packet or any other kind of packet that can be encapsulated in an Ethernet frame.

lxgr 2y ago

> A TCP segment is a thing in its own right. It is not equivalent to an IP packet with protocol 6. Why is that a crazy idea to y'all? Nobody is claiming they're the same in this thread, as far as I can tell. "TCP packet" is simply a pretty clear/unambiguous contraction of "an IP packet carrying TCP", or "an IP packet containing a TCP segment", to me.

adrian_b 2y ago

Yes you are right that an "IP packet carrying TCP" is totally different from a "TCP segment". Like I have explained, this is precisely the reason why we need two different terms, "TCP packet" and "TCP segment", to name the two different things. There exists no 1-to-1 mapping between TCP packets and TCP segments. It is frequent for a TCP segment to span multiple TCP packets. Muddying the waters would be if the same term would be used for the two different things. When two different things have two different names, the waters are clear. Likewise, there is a 1-to-1 mapping between the "Ethernet frame with IP stuff in it" and the IP packet contained inside the Ethernet frame (ignoring the distinction between complete IP packets and fragmented IP packets, which has been removed in IPv6). The IP packet is obtained by deleting or ignoring the Ethernet header & CRC, while the Ethernet frame is obtained by adding to the IP packet the Ethernet header and CRC. Because of the 1-to-1 mapping, there is no risk of confusion when using a term like "IP packet", regardless whether you speak about the IP packet alone, as existing in the memory before being sent or after reception, on about the IP packet as existing on the communication links or in some tool for network monitoring/sniffing, where it is encapsulated in the Ethernet frame. Similarly for an ARP packet or any other kind of packet that can be encapsulated in an Ethernet frame.