itself have a constructed encoding - this will make the tag A1, and
it will contain elements each tagged 04 (OCTET STRING). According to
CULR- 1, these elements are primitive (otherwise they would be 24 of
course).
6.5 Closedown - release request
When all is done, and you want to close down gracefully, send this on
T-DATA.
- FINISH SPDU
09 10 {1 - 9 identifies FINISH
* Ls ? - No Transport Disconnect item
- default is release Transport-connection
C1 0E {2 - User data (code 193)
- P-RELEASE req/ind PPDU (has no name)
61 80 {3 - [APPLICATION 1], user data, fully-encoded
30 80 {4 - [SEQUENCE] PDV-list
02 01 01 -- pcid for ACSE, remembered from setup
A0 80 {5 - [0] single asn.1-type
- A-RELEASE request APDU - RLRQ
62 80 {6 - [APPLICATION 2] identifies RLRQ
80 01 00 - [0] reason, value 0 means normal
* La ?
-- the user information field may or may not be required
- ( not required for Group I)
?BE 80 {7 - [30] IMPLICIT SEQUENCE
?28 80 {8 - [EXTERNAL]
-- the transfer-syntax oid is not present this time
?02 01 03 - [INTEGER] this is the pcid for the application
- data
?A0 La xxxxx -- [0] single-ASN.1-type application data
-- (see note at end of 6.1)
?00 00 }8 - end of EXTERNAL
-- conceivably there may be several EXTERNALS, probably in
-- different presentation contexts (different pcids)
?00 00 }7 - end of user information field
00 00 }6 - end of RLRQ
00 00 }5 - end of single asn.1-type
00 00 }4 - end of PDV-list
00 00 }3 - end of Presentation User-data
6.6 Closedown - release response
On receiving a FINISH, you send this to tell the other end it is all
over
- Session DISCONNECT SPDU
0A Ls {1 - SI=10, DISCONNECT
C1 Ls {2 - User data
- P-RELEASE rsp PPDU
61 80 {3 - [APPLICATION 1], user data, fully-encoded
30 80 {4 - [SEQUENCE] PDV-list
02 01 01 -- [INTEGER] pcid for ACSE, remembered from setup
A0 80 {5 - [0] single asn.1-type
- A-RELEASE response APDU - RLRE
63 80 {6 - [APPLICATION 3] identifies RLRE
80 01 00 - [0] reason, value 0 means normal
* La ?
-- the user information field may or may not be required
- (not required for Group I)
?BE 80 {7 - [30] IMPLICIT SEQUENCE
?28 80 {8 - [EXTERNAL]
-- the transfer-syntax oid is not present this time
?02 01 03 - [INTEGER] this is the pcid for the application
- data
?A0 La xxxxx -- [0] single-ASN.1-type application data
-- (see note at end of 6.1)
?00 00 }8 - end of EXTERNAL
-- conceivably there may be several EXTERNALS, probably in
-- different presentation contexts (different pcids)
?00 00 }7 - end of user information field
00 00 }6 - end of RLRE
00 00 }5 - end of single asn.1-type
00 00 }4 - end of PDV-list
00 00 }3 - end of Presentation userdata
6.7 Deliberate abort
It is not clear whether this is any use - just clearing the Transport
connection will be more effective. It goes on T-DATA, but asks for
the far-side to close the T-connection.
- Session ABORT SPDU
19 Ls {1 - SI of 25 is ABORT
11 01 03 - Transport Disconnect PV, code 17
-- value = '...00011'b means please
-- release T-conn, user abort
* Ls ?
C1 11 {2 - Session User Data
- P-U-ABORT PPDU - ARU
A0 80 {3 - [0] implicit sequence for normal mode
A0 80 {4 - [0] presentation-context-identifier-list
30 80 {5 - [SEQUENCE]
02 01 01 - [INTEGER]pcid for ACSE
06 02 5101 - [OID] for acse transfer syntax = BER
00 00 }5
-- there will be one {6} group for each application
-- presentation context that is used in this message
-- if there is no user data, the {6} group can be
-- omitted
30 80 {6
02 01 03 - [INTEGER] pcid for application data
06 La xxxxxx - [OID] transfer syntax for application data
00 00 }6
00 00 }4 - end of presentation-context-identifier-list
61 80 {7 - [APPLICATION 1], user data, fully-encoded
30 80 {8 - [SEQUENCE] PDV-list
02 01 01 - [INTEGER] pcid for ACSE as on CP PPDU
A0 05 {9 - [0] single asn.1-type
- A-ABORT APDU - ABRT
64 80 {10 - [APPLICATION 4] identifies ABRT
80 01 01 - [0] value 1 is acse-service-provider
-- the user information field may or may not be required
?BE 80 {11 - [30] IMPLICIT SEQUENCE
?28 80 {12 - [EXTERNAL]
-- the transfer-syntax oid is not present this time
-- (according to CULR-1)
?02 01 03 - [INTEGER] this is the pcid for the application
- data
?A0 La xxxxx -- [0] single-ASN.1-type application data
-- (see note at end of 6.1)
?00 00 }12 - end of EXTERNAL
-- conceivably there may be several EXTERNALS, probably in
-- different presentation contexts (different pcids)
?00 00 }11 - end of user information field
00 00 }10 - end of ABRT
00 00 }9 - end of single asn.1-type
00 00 }8 - end of PDV-list
00 00 }7 - end of Presentation user-data
00 00 }3 - end of ARU-PPDU
6.8 Provider abort
Generated when an internal error occurs (i.e., something has gone
mildly (?) wrong in the cookbook implementation). Rather than accuse
anyone of protocol errors, we just abort at session.
ABORT SPDU
19 03 {1 - SI=25 = ABORT SPDU
11 01 09 - Transport Disconnect PV, code 17
-- value = '...01001'b release T-conn
-- no reason
* Ls ?
6.9 Abort accept
If a Session abort (of any kind) is sent, it is possible that the
far-end will send back an abort accept. If this happens, disconnect
the transport. (The abort messages above do not propose that the
transport connection be reused, and in this case, an abort accept is
just the far-end passing the transport-disconnect initiative back.)
This session message need never be sent - just disconnect transport
on receiving an abort.
ABORT ACCEPT SPDU
1A 00 . - SI=26 = ABORT ACCEPT SPDU, no parameters
7. References
[CULR-1] ISO/IEC DISP 11188-1 - Information Technology -
International Standardised Profile - Common Upper Layer Requirements
- Part 1: Basic Connection oriented requirements (DISP ballot ends
June 1994).
[CULR-3] Draft of Common Upper-layer requirements - Part 3: Minimal
OSI upper layers facilities (A later draft will be proposed as ISP
11188/3).
[ISO8072] Information processing systems - Open Systems
Interconnection - Transport service definition; ISO, 1986.
[ISO8073] Information processing systems - Open Systems
Interconnection - Transport protocol specification; ISO, 1986.
[ISO8326] Information processing systems - Open Systems
Interconnection - Basic connection oriented session service
definition; ISO, 1987 (or review copy of revised text = ISO/IEC
JTC1/SC21 N4657, April 1990).
[ISO8327] Information processing systems - Open Systems
Interconnection - Basic connection oriented session protocol
specification; ISO, 1987 (or review copy of revised text = ISO/IEC
JTC1/SC21 N4656, April 1990).
[ISO8649] Information processing systems - Open Systems
Interconnection - Service definition for the Association Control
Service Element; ISO, 1989.
[ISO8650] Information processing systems - Open Systems
Interconnection - Protocol specification for the Association Control
Service Element; ISO, 1989.
[ISO8822] Information processing systems - Open Systems
Interconnection - Connection-oriented presentation service
definition; ISO, 1989.
[ISO8823] Information processing systems - Open Systems
Interconnection - Connection-oriented presentation protocol
specification; ISO, 1989.
[ISO8824] Information technology - Open Systems Interconnection -
Specification of Abstract Syntax Notation One (ASN.1), ISO/IEC 1990.
[ISO8825] Information technology - Open Systems Interconnection -
Specification of Basic Encoding Rules for Abstract Syntax Notation
One, ISO/IEC 1990.
[RFC1006] Rose, M., and D. Cass, "ISO Transport Services on Top of
the TCP", STD 35, RFC1006, Northrop Research and Technology Center,
May 1987.
[ISO9594] Information technology - Open Systems Interconnection - The
Directory; ISO/IEC, 1990.
[RFC1274] Barker, P., and S. Kille, "The COSINE and Internet X.500
Schema", RFC1274, University College London, November 1991.
8. Other Notes
The Session, Presentation and ACSE standards have been the subject of
considerable amendment since their first publication. The only one
that is significant to this cookbook is Session addendum 2, which
specifies session version 2 and unlimited user data. New editions of
these standards, incorporating all the amendments, will be published
during 1994.
The coding choices made in the cookbook are (nearly) those made by
the "Canonical Encoding Rules", which are a form of Basic Encoding
Rules with no optionality, specified in the new edition of ISO/IEC
8825. A defect report has been proposed against Presentation and
ACSE, suggesting that a note to the protocol specifications recommend
use of the canonical encoding options when sending, and then
optimising for this on receipt.
9. Security Considerations
Security issues are not discussed in this memo.
10. Author's Address
Peter Furniss
Peter Furniss Consultants
58 Alexandra Crescent
Bromley, Kent BR1 4EX
UK
Phone & Fax +44 81 313 1833