TCP/IP Tutorial and Technical Overview - IBM Redbooks

► Destination IP Address: The 32-bit IP address of the destination host for this
datagram.
► Options: An IP implementation is not required to be capable of generating
options in a datagram. However, all IP implementations are required to be
able to process datagrams containing options. The Options field is variable in
length (there can be zero or more options). There are two option formats. The
format for each is dependent on the value of the option number found in the
first octet:
– A type octet alone is illustrated in Figure 3-20.
type
1 byte
Figure 3-20 IP: A type byte
– A type octet, a length octet, and one or more option data octets, as
illustrated in Figure 3-21.
Figure 3-21 IP: A type byte, a length byte, and one or more option data bytes
The type byte has the same structure in both cases, as illustrated in
Figure 3-22.
Figure 3-22 IP: The type byte structure
102 TCP/IP Tutorial and Technical Overview
type length option data...
1 byte 1 byte
length - 2 bytes
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