Name
Protocol Type (IP)
Synopsis
Identifies the higher-level protocol in use. For the purpose of this book, this field always contains the topology-specific identifier for the IPv4 protocol.
- Size
Sixteen bits.
- Notes
Since ARP talks to the physical medium’s data-link interface directly, it is not tied specifically to IP and can be used by any higher-level protocol seeking the hardware address associated with a higher-level protocol address (such as IPX, or DECnet, or whatever). For this reason, the Protocol Type field must define the higher-level protocol the request is referring to (which is always IP, as far as this book is concerned).
For Ethernet networks, the value for IP would be hexadecimal 0800 (which equates to the decimal value of 2048, the Protocol Type for IP).
- Capture Sample
In the capture shown in Figure 3.10, the Protocol Type is set to hexadecimal 0800, the code for IP.
Figure 3.10. The Protocol Type field- See Also
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