[scrm-wg] New template and OSI mapping question
Franco Travostino
travos at nortel.com
Mon Aug 8 10:54:07 CDT 2005
My 2 cents on the question that went unanswered in today's SCRM call:
The mapping to the OSI stack is controversial (especially at layers
greater than 3!) because no one follows the OSI stack as a formal
design center. It's rather an after-the-fact orientation tool.
Not surprisingly, HTTP has Layer 5 traits (session: e.g., the reuse
of TCP flows) and Layer 6 traits (presentation: e.g., the MIME-like
encoding). Tim Berners Lee et al. called it an "application-level
protocol" in RFC 1945
http://www.ietf.org/rfc/rfc1945.txt?number=1945. The mapping was
equally troublesome 20 year ago. TCP itself spreads between Layer 5
and Layer 4 and is not a pure Layer 4 play like most diagrams show.
Likewise, the FTP application was recognized having elements of
session, presentation, and application layers.
>SOAP and all WS-* are above layer 8
The Layer 8, 9, and 10 have long been the target of dry humor (as in
being money, politics, religion respectively). It's difficult to be
taken seriously when it comes to those layer numbers. I would think
it's best to stay within the canonical 7 layers (and possibly
grouping protocol in 7a, 7b, 7c realms etc if further differentiation
is warranted).
>On the other hand, (2) maps
>HTTP to layer 5 (session) and SOAP to layer 6 (presentation).
This can practically work, while recognizing that a giant
sledgehammer has been dropped on HTTP (it can be argued that it's a
layer 6 protocol just as well).
-franco
Franco Travostino, Director
Advanced Technology, CTO Office
Nortel
600 Technology Park
Billerica, MA 01821 USA
Tel: 978 288 7708
Fax: 978 288 4690
At 06:01 AM 8/1/2005, Hiro Kishimoto wrote:
>Hi all,
>
>I've update master template from v3.6 to v3.6.1 by filling in
>URIs for FCAPS, ISO OSI, and CIM information. The latest template
>is attached.
>
>I have two URIs for ISO OSI information.
>
>(1)
><http://en.wikipedia.org/wiki/OSI_model>http://en.wikipedia.org/wiki/OSI_model
>(2) http://www.looselycoupled.com/opinion/2003/saruk-osi-infr0905.html
>
>(1) is conventional TCP/IP like mapping and (2) is Web services
>focused mapping. In the farmer mapping HTTP is layer 7 (application)
>and SOAP and all WS-* are above layer 8. On the other hand, (2) maps
>HTTP to layer 5 (session) and SOAP to layer 6 (presentation).
>
>I guess this is controversial issue, but we need single mapping rule
>for comparison. If we use (1) mapping, many summary sheets fall in to
>layer 7 and question #12 becomes meaningless. In order to have
>meaningful grouping, I think mapping (2) is better.
>
>Your thoughts?
>--
>Hiro Kishimoto
>
>
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