Talk:Presentation layer

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HTML?[edit]

What is HTML doing as an example of the presentation layer? HTML is an app layer protocol!Danielcohn 18:41, 30 March 2006 (UTC)

analogy in human communications compared to the presentation layer in network communications

Protocols[edit]

Err, umm, aren't NCP (Netware Core Protocol) and AFP (Apple Filing Protocol) application protocols? Guy Harris 22:50, 23 December 2005 (UTC)

Minor point[edit]

A very very minor point, but should we really say "C++ string"? I mean, that sounds like a classical C-string, in C++ there's also the std::string class (which is preferable for many tasks). This text could make someone who is only briefly acqainted with C and C++ to think that "thisisastring\0" is more of a C++ thing, than a C-thing, when actually, it is directly the opposite. Perhaps change the wording to "C/C++ string", or just plainly "C string"? Okay.. this is really a very minor point. :-) —Preceding unsigned comment added by 194.192.22.33 (talkcontribs)

Good point. Since that syntax is applicable to both languages, I think I'll change it to read "C/C++ string". — EagleOne\Talk 18:16, 10 February 2006 (UTC)

data compression[edit]

Someone should mention, that data compression is handled by the presentation layer too! Stdazi 20:32, 5 May 2007 (UTC)

examples[edit]

What is the example section about? What does it have to do with presentation layer in this context? I will remove it, if no one tries to stop me.

Kremso 21:30, 20 May 2007 (UTC)

Yes, apparently the example section is a bit incorrect. I've taken out PNG, GIF, JPEG and TIFF, since they are file formats, not presentation layer examples. I left the rest of the links untouched; they seemed ok to me. Facuq 01:48, 14 June 2007 (UTC)

JTM: presentation or application ?[edit]

The page the external link points to says:

JTM - "Job Transfer and Manipulation" was one of the initial set of OSI application-layer standards

. So does JTM really belong here ? --Jotel 18:09, 19 July 2007 (UTC)

Presentation layer in the 3-tier system architecture[edit]

Is this different from the presentation layer of the 3-tier system architecture ? If yes, then that should be mentioned somewhere above and linked in the related-topics. I am not sure of that, if someone can enlighten me. mizzo (talk) 08:42, 18 March 2008 (UTC)

nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnmnnm cmnn bmmmmmmmmmmmmmmmmmnnnnnnmb  — Preceding unsigned comment added by 27.0.102.231 (talk) 18:57, 23 December 2012 (UTC) 

Informal Text Style[edit]

The presentation layer is the first one where people start to care about what they are sending at a more advanced level than just a bunch of ones and zeros.

I think parts of the page need re-wording to be a bit more encyclopedic.

doubts..[edit]

Does the host to network and network to host data format conversion happen in the presentation layer? --Sylvestersteele (talk) 16:15, 30 April 2008 (UTC)

Cisco - JPEG, GIF, TIFF[edit]

Why do some books (such as Cisco publications) present these graphics formats as being part of Layer 6? This article should mention this, and clarify what seems to be contradictory information. It seems to me that there is no unique layer 6 "graphic format header", and that they have nothing to do with preparing to send the data over the network, so what is the explanation for why Cisco mentions them at this layer?Jimhoward72 (talk) 10:08, 4 December 2008 (UTC)

Take it from the top[edit]

This article should be restarted in my opinion. I came to view discussions because the article content isn't very good compared to other articles. Citations are used correctly, content is largely inaccurate. For example, file formats and markup languages are not related to networking layers so HTML doesn't belong anywhere in the discussion or the article. Same goes for file formats.

I prefer standards-compliant explanations over material from proprietary sources because the standards-compliant definitions (IETF) aren't negotiable. That is, if an implementation do it this way the implementation doesn't work for everyone, which is the purpose of standardizing. On the other hand, I recall Cisco cert materials, years ago, referred to the OSI model without bias. Kernel.package (talk) 18:40, 14 June 2011 (UTC)

I disagree. Protocols for data transformation occur at the presentation layer. These include: JPEG, GIF, MPEG, MIME, XML, and HTML. Because this layer handles data format conversions (text, binary, and graphics), and data compression and expansions. If you don't agree, then you are implicitly declaring there is a "layer 8" where these protocols apply. SunSw0rd (talk) 15:42, 22 June 2011 (UTC)
I agree with User:Kernel.package. I believe that the presentation layer does nil-nada with images and markup languages. The root of the problem is that the IP suite doesn't accept the OSI model and implement network APIs in discord with layers 5 to 7. That the hypothetical presentation layer handles JPEG, GIF, MPEG, MIME, XML, and HTML conversion this-way or that-way is just a vision of how it should be. Image conversions doesn't act in a subordinate user-invisible layer in real life, in the rare cases that they actually occur, they're in the application layer.
In real programmer life (socket API and similar) the following occurs in a de facto "communication layer" consisting of:
session opening:
  • open/close socket connections (or use any kind of middle-ware),
media conversion:
  1. lowest, there's the byte order conversion API calls htons and similar,
  2. any encryption/decryption by using relevant API:s,
  3. then compression/decompression by using f.ex. zlib,
  4. then the character encoding for text formats (ISO-8859-1, Unicode etc.), images are rarely or never converted this way since the conversion is lossy
interpretation:
  1. then scanning/parsing the data to a data structure, very approximately counterparting the application layer, images are converted to pixmaps here,
Most of the presentation layer descriptions I've read, are either incredibly confused, or practically misleading: real life isn't like that! If the OSI model is contrafactual, then the specs are defining for the model that is actually not used in practice. Rursus dixit. (mbork3!) 10:08, 9 August 2011 (UTC)
To add a little more to the confusion: image conversion to pixmaps, can also be in the "media conversion" layer. If the implementation is that way. Rursus dixit. (mbork3!) 10:13, 9 August 2011 (UTC)

A stated issue appears to be "it doesn't work that way in real life". That is true but remember the OSI model is theoretical. Therefore the statement that JPEG or XML are not handled in the presentation layer is incorrect. That is the layer they would be handled in, IF the presentation layer actually existed in fact as opposed to theory. There are multiple mappings between the OSI model and "real world" implementations, some of those mappings disagree. SunSw0rd (talk) 17:21, 16 August 2011 (UTC)

Move discussion in progress[edit]

There is a move discussion in progress which affects this page. Please participate at Talk:Physical Layer - Requested move and not in this talk page section. Thank you. —RM bot 03:45, 19 October 2011 (UTC)