1. Services and SAPs Date: 2006-05-16 Authors: May 2006 May2006
doc.: IEEE /0743r1
May 2006
Services and SAPs
Date:
Authors:
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Darwin Engwer, Nortel
Darwin Engwer, Nortel

2. May2006
doc.: IEEE /0743r1
May 2006
Abstract
An analysis of the general hierarchy of 802 standards and specifically Services vs. Service Access Points (SAPs).
Darwin Engwer, Nortel
Darwin Engwer, Nortel

3. Outline Assertions stated in 802.0 wrt SAPs The Broader View
May 2006
Outline
Assertions stated in wrt SAPs
The Broader View
Use of SAPs
802 Standards Hierarchy Table
802 Standards Hierarchy Diagram
Core Precepts
Synopsis
Conclusion
Summary
References
Darwin Engwer, Nortel

4. Assertions Stated in 802.0 - Part 1
May 2006
Assertions Stated in 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 (X.200)
an API is a local interface specification [for implementers]
Darwin Engwer, Nortel

5. Assertions Stated in 802.0 - Part 2
May 2006
Assertions Stated in Part 2
an example of a *service interface* definition is two 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
Darwin Engwer, Nortel

6. May 2006
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 (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
Darwin Engwer, Nortel

7. May 2006
Use of SAPs
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
Darwin Engwer, Nortel

8. 802 Standards Hierarchy Table
May 2006
802 Standards Hierarchy Table
Darwin Engwer, Nortel

9. 802 Standards Hierarchy Diagram
May 2006
802 Standards Hierarchy Diagram
ISO
Naming &
Addressing
ISO
X.200
OSI Model
ISO 10731
X.210
SAP
802.2
LLC
Mac Service
802
Overview &
Architecture
802.11
Darwin Engwer, Nortel

10. Synopsis of content of the core references
May 2006
Synopsis of content of the core references
ISO/IEC (X.200) OSI Basic Model
ISO/IEC MAC service definition
ISO/IEC (X.210) OSI Service Conventions
Darwin Engwer, Nortel

11. ISO/IEC 7498-1 (X.200) Precepts Title = OSI Basic Model
May 2006
ISO/IEC (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
Darwin Engwer, Nortel

12. ISO/IEC 15802-1 Precepts Title = MAC service definition
May 2006
ISO/IEC Precepts
Title = MAC service definition
Connectionless-mode service
peer-to-peer data delivery service
Darwin Engwer, Nortel

13. ISO/IEC 10731 (X.210) Precepts Title = OSI Service Conventions
May 2006
ISO/IEC (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 local view abstract i/f
Darwin Engwer, Nortel

14. ISO/IEC 10731 (X.210) Some Examples
May 2006
ISO/IEC (X.210) Some Examples
Darwin Engwer, Nortel

15. May 2006
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
Darwin Engwer, Nortel

16. Service vs. SAP vs. API (an illustrative example)
May 2006
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.
Darwin Engwer, Nortel

17. Conclusion SAPs are used for data service
May 2006
Conclusion
SAPs are used for data service
per ISO and
SAPs are also commonly used for non-data service abstract interface definitions
this use of SAPs is valid and valuable
Darwin Engwer, Nortel

18. Summary Services != Service Access Points (SAPs)
May 2006
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 as the position of the Wireless Co-ordination Advisory Group (WCAG) wrt services and SAPs as used in the 802 wireless standards
Darwin Engwer, Nortel

19. References May 2006 Darwin Engwer, Nortel
ISO/IEC , Information processing systems - Open Systems Interconnection - Basic Reference Model - Part 1: The Basic Model.
ISO/IEC :1994, Information technology - Open Systems Interconnection - Basic Reference Model: The Basic Model.
ISO/IEC , Information processing systems - Open Systems Interconnection - Basic Reference Model - Part 2: Security architecture.
IEEE Std 802.2, Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 2: Logical link control.
ISO/IEC :1998, Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 2: Logical link control.
ISO/IEC , Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Common specifications - Part 1: Medium Access Control (MAC) service definition.
ISO/IEC :1995, Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Common specifications - Part 1: Medium Access Control (MAC) service definition.
ISO/IEC , Information Technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Common specifications - Part 3: Media Access Control (MAC) Bridges.
ISO/IEC TR : 1997, Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Technical reports and guidelines - Part 2: Standard Group MAC addresses.
IEEE Std , IEEE Standards for Local and Metropolitan Area Networks: Overview and Architecture.
IEEE Std ,4 IEEE Standards for Local and Metropolitan Area Networks: Overview and Architecture.
ISO/IEC Technical Report :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 in 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 for 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)
REVma D6.0
802.0 statements (
Darwin Engwer, Nortel

20. May 2006
Backup Slides
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21. May 2006
none
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22. May 2006
The End (really)
Darwin Engwer, Nortel