Segment 是TCP協議端到端傳輸的基本單元，協議內部會把大塊數據分割成以報文段（segment）為單位的數據包進行管理，屬於傳輸層協議
IP Datagram為ip協議端到端傳輸的基本單元
Packet是譯為分組、數據包，是網絡接口層和數據鏈路層傳輸的基本單元，分組既可以是一個IP數據報，也可以是IP數據報的一個片（fragment）
Frame是鏈路層的基本單元，包含鏈路層的頭部信息（mac地址）和網絡層的packet
數據封裝的過程data=>segment=>packet=>frame,同樣也是層層包含的關系，可以從
Wireshark中查看詳細的封包情況
Terminology
-
Segment
A segment is the unit of end-to-end transmission in the
TCP protocol. A segment consists of a TCP header followed
by application data. A segment is transmitted by
encapsulation inside an IP datagram. -
IP Datagram
An IP datagram is the unit of end-to-end transmission in
the IP protocol. An IP datagram consists of an IP header
followed by transport layer data, i.e., of an IP header
followed by a message.
In the description of the internet layer (Section 3), the
unqualified term "datagram" should be understood to refer
to an IP datagram. -
Packet
A packet is the unit of data passed across the interface
between the internet layer and the link layer. It
includes an IP header and data. A packet may be a
complete IP datagram or a fragment of an IP datagram. -
Frame
A frame is the unit of transmission in a link layer
protocol, and consists of a link-layer header followed by
a packet.
以上摘自RFC1122-1.3.3 Terminology