A standard internet address uses a two-part,
32-bit address field. The first part of the address field contains
the network address; the second part contains the local address. The
four different types of address fields are classified as A, B, C,
or D, depending on the bit allocation.
Figure 1 represents a class A address. A class
A address has a 7-bit network number and a 24-bit local address. The
highest order bit is set to 0. Figure 1. Class A Address
Figure 2 represents a class B address. A class B address
has a 14-bit network number and a 16-bit local address with the highest
order bits set to 10. Figure 2. Class B Address
Figure 3
represents a class C address. A class C address has a 21-bit network number
and an 8-bit local address with the three highest order bits set to
110. Figure 3. Class
C Address
Figure 4 represents a class D address.
A class D network is a multicast address that is sent to selected hosts on the network.
The four highest order bits are set to 1110. Figure 4. Class D Address
Note: Class D addresses are not supported in TCP/IP for z/VM.
A commonly used notation for internet host addresses is the dotted-decimal,
which divides the 32-bit address into four 8-bit fields. The value
of each field is specified as a decimal number, and the fields are
separated by periods (for example, 010.002.000.052 or 10.2.0.52).
Address examples in this book use dotted-decimal notation in the
following forms:
