OSI Layer protocols

[anshsinh]

Hi,

I am quite confused on how to categorize different protocols on different layers of OSI model. For eg. which layer do ICMP or DHCP protocols belong to?

How to figure out on which layer do any protocol belongs to in OSI layer?

[Marvin Rhoads · Accepted solution]

For fundamentals like this, refer to a good book like Comer's TCP/IP.

Or consult articles on the protocols themselves - such as one can find in Wikipedia.

https://en.wikipedia.org/wiki/List_of_network_protocols_(OSI_model)

For ICMP:

"The ICMP packet is then encapsulated in an IPv4 packet."

Source: https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol

IP is network layer so that would make ICMP a transport layer protocol in its own right (like TCP and UDP are).

For DHCP:

"DHCP employs a connectionless service model, using the User Datagram Protocol (UDP)."

Source: https://en.wikipedia.org/wiki/OSI_model

DHCP is categorized as application layer since it does not use any session or presentation layer protocol.

Remember - the OSI model is just an academic model. Real world implementations do not always fall neatly into the model. This is very often the case once we go above the transport layer.