Ethernet - Enterasys VH-2402-L3 Management Manual

The flags and fragment offset are used to keep track of
packets that must be divided among several smaller packets
to cross networks for which they are too large.
The Time-to-Live (TTL) is the number of gateways the packet is
allowed to cross between the source and destination. This number
is decremented by one when the packet crosses a gateway and
when the TTL reaches zero, the packet is dropped. This helps
reduce network traffic if a loop develops.

Ethernet

Every active Ethernet device has its own Ethernet address
(commonly called the MAC address) assigned to it by the
manufacturer. Ethernet uses 48 bit addresses.
The Ethernet header is 14 octets that include the source and
destination MAC address and a type code.
There is no relationship between the MAC address of a
network node and its IP address. There must be a database
of Ethernet addresses and their corresponding IP addresses.
Different protocol families can be in use on the same
network. The type code field allows each protocol family to
have its own entry.
A checksum is calculated and when the packet is received,
the checksum is recalculated. If the two checksums are
different, the packet is dropped.
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