Talk:OSI model

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7 layer model[edit]

I hear many people calling this model the 7 layer model, could someone please redirect that term (seven layer model) to this page? — Preceding unsigned comment added by (talk) 10:03, 10 October 2011 (UTC)

These exist: Seven-layer model, Seven-layer OSI model. Dicklyon (talk) 19:43, 18 October 2011 (UTC)

"History" - what about a date?[edit]

The "history" section doesn't mention even a single date... — Preceding unsigned comment added by (talk) 16:58, 14 November 2011 (UTC)

I came here to say that, what use is a history (an ordering of events) that doesn't provide any dates to put it into context with other contemporaneous events. — Preceding unsigned comment added by (talk) 12:37, 7 August 2013 (UTC)

Egad, the current article is quite wacky. Generally unsourced, and seems mostly to be a vandalism magnet. Article mentions Charles Bachman, but he was a database person, not networking. The reality is the late 1970s and early 1980s work by Hubert Zimmermann and John Day (computer scientist) which needs to be clarified with citations. Update: it appears that Bachman did play a role for a time as chair of the ISO/TC97/SC16 between 1977 and 1982. See this source for example, W Nowicki (talk) 18:38, 3 September 2013 (UTC)

"History" - OSI vs. TCP/IP[edit]

Also, was OSI ever implemented, and what is the current state of that implementation (if any)? The intro para calls it a "conceptual model," and there's no mention in the History sxn of an actual implementation. My mid-understanding is that TCP/IP became the de facto standard instead. There's some discussion of this on pg 457 of "The dream machine: J.C.R. Licklider and the revolution that made computing personal" by M. Mitchell Waldrop. The discussion makes it sound like OSI (or perhaps support for OSI) was in part a European political response to the fact that TCP/IP was American (not European) and had been developed under ARPA (therefore US DOD) funding. That of course means this question of why TCP/IP is still around, and OSI isn't (if that's correct), is a contentious issue. I don't know how to evaluate that claim. Mcswell (talk) 14:02, 29 May 2013 (UTC)

Alas, much of this was personal anecdote and thus not really acceptable for Wikipedia. However, this article from July 2013 would be a good one to cite. And of course needs to clarify the model vs. a specific protocol stack. W Nowicki (talk) 18:07, 3 September 2013 (UTC)

The information in parentheses (ISO/IEC 7498-1) tells you unambiguously that "The Open Systems Interconnection (OSI) model (ISO/IEC 7498-1)" is an ISO/IEC International Standard. For precision in labeling, that label should include the date (ISO/IEC 7498-1:1994), but the absence of the date does not change its status. TCP/IP is one implementation of two of the layers of that standard. Please read for yourself about the labeling that the ISO uses to specify the status of a proposed standard as it works its way through the standardization process at: Wikifan2744 (talk) 02:25, 9 September 2013 (UTC)

I withdraw my sentence just above: "TCP/IP is one implementation of two of the layers of that standard." It's much more complicated than that, far more complicated than I can explain. The Internet protocol suite, which includes the TCP/IP networking model and related protocols (TCP, IP, and others), was developed by and is maintained by the Internet Engineering Task Force (IETF): Note that there are both the model and also the protocols. Models and protocols are separate concepts that are easily conflated or confused in writing and speaking.

The article on the IETF begins as follows: "The Internet Engineering Task Force (IETF) develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the Internet protocol suite (TCP/IP).[1][2] It is an open standards organization, with no formal membership or membership requirements."

The article on the Internet protocol suite (commonly known as TCP/IP) is long and comprehensive. Its opening paragraph begins: "The Internet protocol suite is the networking model and a set of communications protocols used for the Internet and similar networks. It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) were the first networking protocols defined in this standard...." Please read the article for further details, but pertinent to this discussion is the section just below.

"OSI and TCP/IP layering differences[edit source | editbeta]

"The three top layers in the OSI model—the application layer, the presentation layer and the session layer—are not distinguished separately in the TCP/IP model where it is just the application layer. While some pure OSI protocol applications, such as X.400, also combined them, there is no requirement that a TCP/IP protocol stack must impose monolithic architecture above the transport layer. For example, the NFS application protocol runs over the eXternal Data Representation (XDR) presentation protocol, which, in turn, runs over a protocol called Remote Procedure Call (RPC). RPC provides reliable record transmission, so it can safely use the best-effort UDP transport.

"Different authors have interpreted the RFCs differently, about whether the link layer (and the TCP/IP model) covers OSI model layer 1 (physical layer) issues, or whether a hardware layer is assumed below the link layer.

"Several authors have attempted to incorporate the OSI model's layers 1 and 2 into the TCP/IP model, since these are commonly referred to in modern standards (for example, by IEEE and ITU). This often results in a model with five layers, where the link layer or network access layer is split into the OSI model's layers 1 and 2.

"The session layer roughly corresponds to the Telnet virtual terminal functionality [citation needed], which is part of text based protocols such as the HTTP and SMTP TCP/IP model application layer protocols. It also corresponds to TCP and UDP port numbering, which is considered as part of the transport layer in the TCP/IP model. Some functions that would have been performed by an OSI presentation layer are realized at the Internet application layer using the MIME standard, which is used in application layer protocols such as HTTP and SMTP.

"The IETF protocol development effort is not concerned with strict layering. Some of its protocols may not fit cleanly into the OSI model, although RFCs sometimes refer to it and often use the old OSI layer numbers. The IETF has repeatedly stated [citation needed] that Internet protocol and architecture development is not intended to be OSI-compliant. RFC 3439, addressing Internet architecture, contains a section entitled: "Layering Considered Harmful".[28]

"Conflicts are apparent also in the original OSI model, ISO 7498, when not considering the annexes to this model (e.g., ISO 7498/4 Management Framework), or the ISO 8648 Internal Organization of the Network layer (IONL). When the IONL and Management Framework documents are considered, the ICMP and IGMP are neatly defined as layer management protocols for the network layer. In like manner, the IONL provides a structure for "subnetwork dependent convergence facilities" such as ARP and RARP.

"IETF protocols can be encapsulated recursively, as demonstrated by tunneling protocols such as Generic Routing Encapsulation (GRE). GRE uses the same mechanism that OSI uses for tunneling at the network layer."

Wikifan2744 (talk) 06:29, 9 September 2013 (UTC)

datagram service model?[edit]

In the section OSI model#Cross-layer functions, the description of Multiprotocol Label Switching (MPLS) states, "It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model." There are two ambiguities with this:

  1. Dangling participle error: What provides the datagram service model? Is the provider one or more of the clients, the data carrying service, or the MPLS function being described?
  2. What is a datagram service model? That phrase does not appear in any other articles and it is not defined in context.

Will an MPLS expert please revise this? Stephen Charles Thompson (talk) 21:19, 24 January 2012 (UTC)

Layer 0[edit]

There is now Layer 0 which is seen on ROADM (Reconfigurable Optical Add/Drop Multiplexor) Fujitsu flashwaves do layer 0, as does Cienna CPL. — Preceding unsigned comment added by (talk) 21:25, 21 April 2012 (UTC)

Incorrect Link on 3rd graphic[edit]

On 3rd graphic (Data Unit -- Layer -- Function), on 2nd Layer "Data Link", on Function column, there is a link to "Physical Layer" that points to a Wikipedia article about "Memory Physical directions", and not "Network Physical directions". I thinks it's more correct to point it to: — Preceding unsigned comment added by (talk) 15:04, 20 June 2012 (UTC)

Thanks, I fixed that. Johnuniq (talk) 02:16, 21 June 2012 (UTC)

errors in description of Layer 1[edit]

According to Tanenbaum ("Computer Networks") and as far as I remember, flow control is not part of the physical layer (1), but of the data link layer (2), and also occurs to some degree within the network layer (3). Also, the physical layer has nothing to do with the sharing of resources among multiple users. That's a task of layer 2 (MAC). Layer 1 covers mainly physical concerns (thus the name) like the media (cable, radio, ...) and how a bit is represented there. --GGShinobi (talk) 21:19, 9 July 2012 (UTC)

Layer 3: network layer - Address not hierarchical?[edit]

In the layer 3 section, there is the phrase "The addressing scheme is not hierarchical.". From my basic understanding of networking, layer 3 addressing IS hierarchical, in contrast to layer 2 one.

Regards Francesco — Preceding unsigned comment added by Francesco87 (talkcontribs) 20:16, 22 October 2012 (UTC)

IP/OSI confusion in layer box[edit]

The box of networking layers here makes the mistake of conflating TCP/IP network protocols with the OSI layers. This is wrong; the two are not connected, not even remotely.

I realize that many educational institutions like to use the OSI model because it's such a neat network model and it's so nice to explain things, but it's 'wrong' to assume that the IP network protocol is situated in layer 4 of the OSI model, or that the SIP protocol is situated in layer 7 of the OSI model. They are not. The IP protocol is found in the network layer of the TCP/IP "model", and the SIP protocol is found in the applicatoin layer of the TCP/IP "model".

If you're going to show the OSI model, the protocols on OSI protocols should be used instead. — Preceding unsigned comment added by (talk) 23:03, 19 April 2013 (UTC)

The OSI model does not only apply to the OSI protocols as the networking literature attests. --EnOreg (talk) 15:26, 21 April 2013 (UTC)

Semi-protected edit request on 31 July 2014[edit]

DHCP is a network layer protocol and not application layer. these are all for delivering IP addresses to the node including other information. (talk) 13:18, 31 July 2014 (UTC)

No, DHCP messages are ultimately sent with IP, so that can't be right. Anon126 (notify me of responses! / talk / contribs) 21:07, 9 August 2014 (UTC)