Talk: Internet protocol suite
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Why are there 7 layers in the stack? I thought that TCP/IP only had 5.
5. Application - DNS, HTTP, FTP, Telnet, etc.
4. Transport - TCP, UDP
3. Network - IP
2. LAN/Link - network address (physical or MAC)
1. Physical - low-level signal
Isn't UDP and TCP in the same layer ? --Wikipedians/arcade
- Yes, you are right... changing it now. -- SJK
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Confusing layers
When I think about it, I think ICMP is on the same layer as those too .. IGMP I know nothing about, though. --Wikipedians/arcade
- Yes, that's right: Even although ICMP is a required protocol for the TCP/IP stack, it is still implemented as a Transport layer protocol, not as a Network layer protocol. This can be easily seen by the fact that ICMP has a protocol number (it being protocol number 1). The same is true for IGMP (except that it has protocol number 2).
- In fact, there is only one network layer protocol in the TCP/IP stack: IP itself. -- Wouter Verhelst
Hmm, when I think a bit more about it. The Internet Protocol Suite doesn't follow the OSI layering all the way, so the stack is quite simply ... wrong, as it is portrayed.
The 3 bottom layers are pretty okay. However, IMCP is dependent on IP, so it needs to be pushed higher up on the stack. HTTP/STMP/SNMP and so forth are _NOT_ dependent on the layer that is presented as beneath it, and thus needs to be bumped down.
Roughly, something like:
7. Protocols that are tunnelled through those in layer 6. Say an XML protocol served through a HTTP server.
6. HTTP/SMTP/SNMP/FTP/and-so-forth
5. TCP/UDP/ICMP/Whatever
4. Transport (IP, for the internet protocol)
3. Network
2. Data Link
1. Physical
- No, you're applying the OSI network concept to the TCP/IP network stack. That isn't correct. -- Wouter Verhelst
Not sure about that... How about:
=> Application (telnet, ftp, http, dns, ...)
4. Transport (TCP, UDP...)
3. Network (IP)
2. Data Link (Ethernet, Token-ring, ISDN...)
1. Physical
Labelling formats like JPEG (or EBCDIC / ASCII) as a presentation layer is a bit of a hack to force the square peg of real world networking into the round hole of OSI protocol stackery (IMHO, of course).
Sometimes the Application Layer is still called layer 7 for "compatibility", but there is no real unified layer 5 or 6 -- sessions, presentation and data formats are considered the task of applications, and are absolutely not part of the TCP/IP protocol suite.
--Paul
- ICMP is definitely not part of the transport layer. Layers in the OSI model are defined by functionality, not by dependencies between protocols (think modules). Layer != Protocol! So everything which is related to getting packets from one host to another is logically part of the Network layer. That includes routing - which in at least one case has a protocol (BGP) runs on top of TCP (which is at the transport layer)! Look, I know this all seems totally crazed - it is totally crazed. The ISO model has only limited usefulness. It divides things up into functional layers, it is not a module dependency diagram.
- It's for these reasons that I removed ICMP from MediaWiki:IPstack. It was at the wrong layer, and since it is such a confusing case, it seemed better not to include any of these confusing cases in the diagram. Noel 13:02, 14 Sep 2004 (UTC)
- I think the German suite diagram clears up some of these confusing elements. Also, following some of the protocol links like de:HTTP shows the implementation dependencies via another diagram. Dols 13:04, 2004 Oct 6 (UTC)
OSI was practical
Can't agree with "The Internet model was produced as the solution to a practical engineering problem. The OSI model, on the other hand, was a more theoretical approach."
Internet architecture developed as a means of internetworking on a "non-sectarian" basis-- a practical engineering problem.
The OSI Reference Model likewise developed as a means for networking systems on a "non-sectarian" basis. More specifically, there was a clear understanding at the time that the goal was to interconnect computers and/or devices in a way that did not depend on IBM intellectual property. Witness the striking similarities between the OSI Reference Model and IBM's SNA. Anyone working for DEC or NEC or HP or Siemens or the like at the time will assure you it was a VERY practical engineering problem.
OSI protocols became ungainly and arcance in toto not because the work was theoretical but because the work was done in government-entangled standards bodies. Anyone familiar with the total output of the internet community knows it's output is likewise full of a lot of unused junk and nonsense besides the successful and critical parts, regardless of it's requirement for "working code".
Tanenbaum
I'm looking at a Dutch translation from Andrew S. Tanenbaum's "Computer Networks, Third edition" right now. On pages 29 to 36, it describes the ISO model; then, on pages 37 to 39, it gives an introduction in the TCP/IP reference model.
Tanenbaum names the following layers in TCP/IP:
- Application layer (functionally similar to OSI's application layer)
- Transport layer (similar to OSI's transport layer)
- Internet layer (similar to OSI's network layer)
- Host-to-network layer (implementing functionality from OSI's datalink- and physical layer).
The paragraph about the host-to-network layer transcribes approximately to the following: "Under the Internet layer is a big empty space. The TCP/IP reference model doesn't say a lot about what happens here, except that it specifies that the host has to connect to the network using a protocol that allows it to send IP packets. This protocol isn't defined; it varies from host to host and from network to network. In books and articles about the TCP/IP model, this protocol is rarely ever mentioned"
As examples, Tanenbaum mentions ARPANET, SATNET, Packet radio, and LAN.
-- Wouter Verhelst
- There are only FOUR layers in the TCP/IP suite! The Tantenbaum citing is correct. Please fix your main definition page. -- MJ Foy Sr. MCSE, MCT, Net+ A+, CCNA, CNA, Security+, BS
IPstack
Guys, can anyone tell me how the {{IPstack}} tag works, where it is defined and how to edit it? Thanks. Sridev 13:48, 25 Sep 2004 (UTC)
Readings typo
Surely we can recommend additional readings besides a MS Windows 2003 book?
In any event, the citation contained 2 typos: The corrected version appears below
Davies, Joseph and Lee, Thomas. (2003). Microsoft® Windows® Server 2003 TCP/IP Protocols and Services Technical Reference. Microsoft Press, Redmond Washington, USA.
Hopefully these corrections will also eventually filter down to derivitive sites such as: http://www.domainsarefree.com/glossary/Internet_protocol_suite.html (They also need to change their character set from utf-8 to iso-8859-1 so the ® marks render properly.)
- Wish granted. Replaced book list with more representative "classic" titles. - Dmeranda 05:10, 23 Nov 2004 (UTC)
