Services and SAPs

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doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
1

Services and SAPs

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Date:

2006
-
05
-
16

Authors:

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
2

Abstract

An analysis of the general hierarchy of 802 standards and
specifically Services vs. Service Access Points (SAPs).

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
3

Outline


Assertions stated in 802.0 wrt SAPs


The Broader View


802.11 Use of SAPs


802 Standards Hierarchy Table


802 Standards Hierarchy Diagram


Core Precepts


Synopsis


Conclusion


Summary


References

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
4

Assertions Stated in 802.0
-

Part 1


concern about the misuse of SAPs as APIs in 802
standards



Services are end
-
to
-
end


a SAP is used to invoke a Service


the implementation is to deliver frames to the peer entity


governing reference is ISO/IEC 7498
-
1 (X.200)



an API is a local interface specification [for
implementers]

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
5

Assertions Stated in 802.0
-

Part 2


an example of a *service interface* definition is two
802.37 devices connected via some medium


if a packet is sent, but fails to be received correctly


then NO primitives occurred


because NO SERVICE WAS PROVIDED


Therefore, most 802 standards define service APIs,
rather than SAPs


i.e. a SAP is an abstraction of the service that was
provided according to the OSI reference model.


In particular a SAP does NOT need to provide
"handshakes", i.e. __.confirm callbacks

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
6

The Broader View


based on the hierarchy of the 802 reference standards
and an analysis thereof.


Terms and meaning need to be clarified …


governing reference is ISO/IEC 10731 (X.210)


“Services” differ from Service Access Points (SAPs)


even though the names are similar


“Services” are enumerations of high level ISO Services


SAPs are abstract interfaces


defined using X.210 primitives


may or may not describe end
-
to
-
end OSI Services


may also define operational precepts of the underlying technology

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
7

802.11 Use of SAPs


802.11 commonly uses SAP definitions as an abstract
interface specification


this is a service interface built on X.210 primitives


this is NOT an API definition


makes use of the allowed X.210 primitive sequence combinations*


typically no one implements to this interface


used to provide complete operational definitions and descriptions


primitives
may

result in the invocation of OSI “Services”


this is a common SAP objective but is not true in all cases



Suspect the same is true for other 802 wireless WGs

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
8

802 Standards Hierarchy Table

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
9

802 Standards Hierarchy Diagram

ISO 7498
-
3

Naming &

Addressing

15802.1

Mac Service

ISO 7498
-
1

X.200

OSI Model

802.2

LLC

802

Overview &

Architecture

ISO 10731

X.210

SAP

802.11

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
10

Synopsis of content of the core references


ISO/IEC 7498
-
1 (X.200) OSI Basic Model


ISO/IEC 15802
-
1 MAC service definition


ISO/IEC 10731 (X.210) OSI Service Conventions

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
11

ISO/IEC 7498
-
1 (X.200) Precepts


Title = OSI Basic Model


Open Service Interconnection (OSI) environment


Layers/ layering
--
> peer entities


Communication between peer entities: protocols


Properties of service
-
access
-
points (SAPs)


Data units

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
12

ISO/IEC 15802
-
1 Precepts


Title = MAC service definition


Connectionless
-
mode service


peer
-
to
-
peer data delivery service

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
13

ISO/IEC 10731 (X.210) Precepts


Title = OSI Service Conventions


Entities: SAPs, Service Users and Service Providers


Actions via Service Primitives


.request requestor.submit


.indication acceptor.deliver


.response acceptor.submit


.confirm requestor.deliver


Use case scenarios


4 primitive (full exchange)


2 primitive (.request/ .indication)


1 primitive (.indication)


2 primitive (.request/ .confirm)
-

cl 5.2.2 local view abstract i/f

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
14

ISO/IEC 10731 (X.210) Some Examples

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
15

Analysis Synopsis


ISO services are not defined (in detail), they are just
enumerated


SAPs are defined in detail with a complete set of
primitives


SAPs are not just for data OSI services

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
16

Service vs. SAP vs. API

(an illustrative example)


Domain = Our Meeting Room



Service = Lighting


i.e. we commit to providing a lighting service


SAP = lighting control abstract interface


primitives = on, off, dim, status


API = an implementation specific interface


e.g. there is a switch/ dimmer on the wall by the door



Note that the Service, SAP and API can be defined independently of
each other, i.e. some or all of those can be defined. They are all
shown here only for illustration and comparison purposes.


doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
17

Conclusion


SAPs are used for data service


per ISO 7498
-
1 and 15802.1


SAPs are also commonly used for non
-
data service
abstract interface definitions


this use of SAPs is valid and valuable

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
18

Summary


Services != Service Access Points (SAPs)


Services are abstract service enumerations


SAPs are abstract interfaces defined by X.210 primitives


SAPs can be used for abstract interface definitions
other than (N)
-
layer data services


e.g. MAC management services


Potential next steps:


Present the enclosed material to 802.0 as the position of the
Wireless Co
-
ordination Advisory Group (WCAG) wrt services and
SAPs as used in the 802 wireless standards

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
19

References


ISO/IEC 7498
-
1, Information processing systems
-

Open Systems Interconnection
-

Basic Reference Model
-

Part 1: The Basic Model
.


ISO/IEC 7498
-
1:1994, Information technology
-

Open Systems Interconnection
-

Basic Reference Model: The Basic Model.


ISO/IEC 7498
-
2, Information processing systems
-

Open Systems Interconnection
-

Basic Reference Model
-

Part 2: Security archit
ecture.


IEEE Std 802.2, Information technology
-

Telecommunications and information exchange between systems
-

Local and metropolitan ar
ea networks
-

Specific requirements
-

Part 2: Logical link control.


ISO/IEC 8802
-
2:1998, Information technology
-

Telecommunications and information exchange between systems
-

Local and metropolit
an area
networks
-

Specific requirements
-

Part 2: Logical link control.


ISO/IEC 15802
-
1, Information technology
-

Telecommunications and information exchange between systems
-

Local and metropolitan a
rea
networks
-

Common specifications
-

Part 1: Medium Access Control (MAC) service definition.


ISO/IEC 15802
-
1:1995, Information technology
-

Telecommunications and information exchange between systems
-

Local and metropoli
tan area
networks
-

Common specifications
-

Part 1: Medium Access Control (MAC) service definition.


ISO/IEC 15802
-
3, Information Technology
-

Telecommunications and information exchange between systems
-

Local and metropolitan a
rea
networks
-

Common specifications
-

Part 3: Media Access Control (MAC) Bridges.


ISO/IEC TR 11802
-
2: 1997, Information technology
-

Telecommunications and information exchange between systems
-

Local and metro
politan
area networks
-

Technical reports and guidelines
-

Part 2: Standard Group MAC addresses.


IEEE Std 802
-
1990, IEEE Standards for Local and Metropolitan Area Networks: Overview and Architecture.


IEEE Std 802
-
2001,4 IEEE Standards for Local and Metropolitan Area Networks: Overview and Architecture.


ISO/IEC Technical Report 11802
-
5:1997(E), Information technology
-

Telecommunications and information exchange between systems
-

Local and
metropolitan area networks
-

Technical reports and guidelines
-

Part 5: Medium Access Control (MAC) Bridging of Ethernet V2.0 i
n Local Area
Networks (previously known as IEEE 802.1H
-
1997).


ITU
-
T Recommendation X.210 (11/93), Information technology
-

Open systems interconnection
-

Basic Reference Model: Conventions f
or the
definition of OSI services (common text with ISO/IEC 10731).


ITU
-
T Recommendation Z.120 (1999), Programming Languages
-

Formal Description Techniques (FDT)
-

Message Sequence Chart (MSC).


802.1ae (draft 5.1)


802.11
-
REVma D6.0


802.0 statements (www.ieee802.org/1/files/public/802_architecture_group/presentations/Pages%20from%20802
-
1aq
-
d0
-
1.pdf)

doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
20

Backup Slides


doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
21

none


doc.: IEEE 802.11
-
06/0743r1

Submission

May 2006

Darwin Engwer, Nortel

Slide
22

The End (really)