D-Link DES-3326S - Manual (Page 100)

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
100 Switch Management and Operating Concepts
Figure 5-11. IP Packet Header
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.