Basically, his general rule of thumb for this is;
Layer 2 - Ethernet Frames
Layer 3 - IP Packets
Layer 4 - Segments
But "atr2006" refer to
- RFC 1812:
Datagram
The unit transmitted between a pair of internet modules. Data,
called datagrams, from sources to destinations. The Internet
Protocol does not provide a reliable communication facility.
There are no acknowledgments either end-to-end or hop-by-hop.
There is no error no retransmissions. There is no flow control.
Fragment
An IP datagram that represents a portion of a higher layer's
packet that was too large to be sent in its entirety over the
output network.
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.
IP Datagram
An IP Datagram is the unit of end-to-end transmission in the
Internet Protocol. An IP Datagram consists of an IP header
followed by all of higher-layer data (such as TCP, UDP, ICMP,
and the like). An IP Datagram is an IP header followed by a
message.
An IP Datagram is a complete IP end-to-end transmission unit.
An IP Datagram is composed of one or more IP Fragments.
IP Fragment
An IP Fragment is a component of an IP Datagram. An IP Fragment
consists of an IP header followed by all or part of the higher-
layer of the original IP Datagram.
One or more IP Fragments comprises a single IP Datagram.
IP Packet
An IP Datagram or an IP Fragment.
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