Layer 4: OK, application I have your session setup.
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Layer 3 = 192.168.3.2
Layer 2 = 0800:0222:1111
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Layer 3 = 192.168.3.2
Layer 2 = 0800:0222:1111
Application: Here is the data.
SRC IP
192.168.3.1
SRC IP
192.168.3.1
SRC MAC
0800:0222:2222
SRC MAC
0800:0222:2222
DST MAC
0800:0222:1111
DST MAC
0800:0222:1111
DST IP
192.168.3.2
DST IP
192.168.3.2
TCP
SEQ = 3
TCP
SEQ = 3
APP
DATA
APP
DATA
SRC IP
192.168.3.1
DST IP
192.168.3.2
TCP
SEQ = 3
APP
DATA
TCP
SEQ = 3
APP
DATA
APP
DATA
98 Chapter 1: Building a Simple Network
Figure 1-83 Data Is Received
Figure 1-84 Data Is Acknowledged
The data exchange continues until the application stops sending data.
Function of the Default Gateway
In the host-to-host packet delivery example, the host was able to use ARP to map a
destination??™s MAC address to the destination??™s IP address. However, this option is available
only if the two hosts are on the same network. If the two hosts are on different networks,
the sending host must send the data to the default gateway, which forwards the data to the
destination. Figure 1-85 shows role of the default gateway in data transfers.
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