Re:Why TCP over TCP Is a Bad Idea (2000)
by adrian_b on Saturday October 26, 2024 @01:55PM
(#41956446)
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.
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.