I'm reading about higher-level protocols such as HTTP and SOAP (concerning the application layer at the highest level) in addition to lower-level ones such as TCP. So far these protocols concern only one layer of the OSI model. For example SOAP talks about application layer specific elements such as type of files to transfer (XML only).

Do any protocols stretch over multiple layers? I could use HTTP with TCP or UDP (my application layer protocol is independent of my transport layer one), but are there any protocols that force another layer's communication to be changed?

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Commented Dec 25, 2018 at 10:00

2 Answers 2


Perhaps you'd count ICMP, which could be considered layer 4 from a technical point of view (its datagrams sit inside IP packets) but which is functionally a part of layer 3.

The Internet Control Message Protocol RFC 792 says:

ICMP uses the basic support of IP as if it were a higher level protocol, however, ICMP is actually an integral part of IP, and must be implemented by every IP module.

  • Much like ethernet and ARP.
    – Ron Maupin
    Commented Nov 15, 2018 at 2:44

I could use HTTP with TCP or UDP

Not really.

Protocols generally make assumptions about the protocols above and below them. For example http 1 and 2 rely on the reliable in-order delivery provided by TCP (http 3 is intended to run over udp but that is a substantially different protocol and standardisation is not complete yet).

From the other side, TCP and UDP were designed to run over IPv4. When IPv6 was introduced by rfc1883 it had a section "upper layer protocol issues" describing the adaptations needed to run TCP and UDP over IPv6. Many higher level protocols and systems also handle internet address in one form or another and so have require adaptation to support IPv6.

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