CODEWITHSUNDEEP
network-programmingarp
sherlock
sherlock

Reputation: 305

why there is a Protocol type filed in ARP header?

From wikipedia of ARP, there is a field called "Protocol Type" which specifies the internetwork protocol for which the ARP request is intended.

But in the Ethernet frame header, there is also a field called "EtherType" which indicate which protocol is encapsulated in the payload of an Ethernet Frame.

And I just want to know why couldn't the ARP protocol just use the EtherType filed? According to wikipedia,the PTYPE and EtherType yet share same numbering space.Is it a historical problem?

Upvotes: 0

Views: 168

Answers (1)

Ton Plooij
Ton Plooij

Reputation: 2641

Apart from Ethernet, ARP can be used by other data link layer protocols like for example token-ring or FDDI. In those cases you might not have an encapsulated protocol field.

Upvotes: 1

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