Foundation Summary 117
Table 3-19 outlines several Layer 3 address structures.
Figure 3-20 illustrates the construction of frames, packets, and segments and shows the
different layers' perspectives on what is considered to be the data.
Figure 3-20
Frames, Packets, and Segments
Figure 3-21 provides an example network by which to review the routing process.
Table 3-19
Layer 3 Address Structures
Protocol
Size of
Address
(Bits)
Name and Size of
Grouping Field
Name and Size of Local
Address Field
IP
32
Network or subnet (variable,
between 8 and 30 bits)
Host (variable, between 2 and 24
bits)
IPX
80
Network (32)
Node (48)
AppleTalk
24
Network (16) (Consecutively
numbered values in this field
can be combined into one
group, called a cable range.)
Node (8)
OSI
Variable
Many formats, many sizes
DSP (typically 56, including NSAP)
TCP
Data
IP
Data
LH
Data
LT
Frame
(L2 PDU)
Packet
(L3 PDU)
Segment
(L4 PDU)
ch03.fm Page 117 Monday, March 20, 2000 4:58 PM