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 ? --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 Template: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)
- I don't understand this comment. I looked at the pages you mention, and their diagrams look pretty much identical to Template:IPstack, except that it has a few more protocols. Noel (talk) 05:33, 16 Dec 2004 (UTC)
- Back in October the diagram looked different. http://de.wikipedia.org/w/wiki.phtml?title=TCP/IP-Referenzmodell&oldid=2921843 I'll try to stop adding confusion into the confusing layers discussion. Dols 00:01, 2004 Dec 18 (UTC)
- Ooops! My fault for coming by and adding a comment so much later! Yes, now I understand your comment.
- Still, the old version (the one you linked to above) of the diagram has many of the problems I mentioned above - e.g. it lists BGP as being at the application layer (yes, I know it uses TCP, but...) and also DNS as an application (Email and HTTP will be astonished to hear that), shows ICMP as a tranport protocol (it's entirely part of the internet layer), etc. Noel (talk) 00:57, 18 Dec 2004 (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
- The TCP/IP suite does not have a fixed number of layers, nor are protocols formally assigned to any layer. It only talks about protocol dependencies (i.e. protocol A uses protocol B). In fact, with some of the ISO protocols which have been adopted to run over TCP, there are in fact more than 4 levels of protocol involved, since the ISO session/etc protocols are used as well as the application. Noel (talk) 05:19, 16 Dec 2004 (UTC)
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)
- It's at Template:IPstack. The way it works is that when the page-rendering code reads the {{IPstack}}, it replaces it with the contents of the Template:IPstack page. May I suggest you mention your proposed change(s) at Template_talk:IPstack first? Thanks... Noel (talk) 05:14, 16 Dec 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)
Some Clarification
The reference above stating there are only four layers in the TCP/IP model is accurate. The "Host-to-network" layer is often refered to as the Network Access layer. The TCP/IP model has no Physical layer because LAN and WAN protocols operate partly at the OSI Physical layer and partly at the IEEE 802.3 Media Access Control (MAC) sublayer of the OSI Data Link layer. The TCP/IP model was designed to be completely independent of the LAN/WAN protocol frames that encapsulate IP packets. Thus, an IP packet can be encapsulated in an Ethernet frame, a Token Ring frame, or any other type of frame, and the IP packet is not changed, nor is the function of the TCP protocol affected in any way. By extension, the TCP segment encapsulated inside the IP packet is not changed either.
The upper half of the OSI Data Link layer, the IEEE Logical Link Control (LLC) sublayer, can be said to loosely correspond to the TCP/IP Network Access layer. The lower half of the OSI Data Link layer, the IEEE MAC sublayer, and the OSI Physical layer, can only be said to correspond to the TCP/IP Network Access layer in a general sense. The Network Access layer is necessary to allow an IP packet to make a physical link to the network media. Generally, this is done by maping IP addresses to physical hardware addresses and encapsulating IP packets into frames. The physical media connection is defined based on the hardware type and network interface, as well as the LAN/WAN protocol in use.
Jim Elms, CCNA, CCAI
It would be great...
It would be great if this article had some practical info. I'm currently struggling with TCP/IP settings. Chamaeleon 18:04, 2 Mar 2005 (UTC)
MPLS
Not really sure where MPLS fits into this picture. From ISO Model Talk I Wrote:
MPLS is considerd to be a switching techonology, i.e. layer 2. However it runs on other layer 2 technologies such as Ethernet or ATM, then why is it not considerd layer 3. Then again is what defines a layer 2 Protocol one that specifies the next hop in the path while layer 3 specifies the final destination.
Possibily could MPLS be considerd a sub-layer of Layer 2, so if MPLS ran over Ethernet there would be 3 sub-layers LLC layer, MAC layer and MPLS layer.
Vec 19 April 2005