rfc1698.txt
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In the comments, the notation {n} refers to the constructed item bracketed by the {n, }n fields.6. Octet sequences6.1 Connection request message - CONNECT SPDU 0D Ls {1 - "SI" value for CONNECT = 13 * Ls ? - Connection Identifier 05 06 {2 - Connect/Accept Item 13 01 00 - protocol options (probably mandatory) * Ls ? 16 01 02 -- version number (bottom bit = v1, next bit =v2. -- may get offers of either or both * Ls ? 14 02 0002 - Session User Requirements (functional units) - Id (20), length (always 2), duplex fu only. -- On receipt, other bits may be set -- check that the 2 bit is set * Ls ? - we do not send any Calling Session SelectorFurniss [Page 17] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994 ?34 Ls xxxx -- Called Session Selector (i.e., the other end's) -- up to 16 octets - you must set what the other -- side demands. - May be anything characters, -- binary etc. - {3} disappeared in editing C1 Ls {4 -- User Data, Identifier=193. if length is > 512, -- then identifier is 194 (hex C2) instead - CP - P-CONNECT-RI PPDU. Everything below is in ASN.1 BER 31 80 {5 - [SET] --- Mode-selector (the {6} group) could possibly --- come after everything else {7} --- This will probably only be done by --- evil-minded conformance testers A0 80 {6 - Mode-selector [0] IMPLICIT SET 80 01 01 - [0] IMPLICIT INTEGER {normalmode(1)} 00 00 }6 A2 La {7 - [2] unnamed IMPLICIT SEQUENCE * La ? ?82 La xxxx - [2] Called-presentation-selector - CULR says maximum length is 4 -- must be what the other side wants A4 80 {8 - [4] Presentation-context-definition-list --- items (the outer SEQUENCEs) within the {8} list may --- be in any order. 30 80 {9 - [SEQUENCE] 02 01 01 -- Defines pcid for ACSE; received value will be -- a one or two octet odd integer 06 04 52010001 - [OID] for ACSE abstract syntax 30 80 { - [SEQUENCE] 06 02 5101 - [OID] Transfer syntax name is BER 00 00 } - end t-s list 00 00 }9 - end acse pctx defn 30 80 {10 - [SEQUENCE] 02 01 03 -- [INTEGER] Defines pcid for application data; -- received value will be a one or two octet odd -- integer 06 La xxxxxx - [OID] object identifier name of application - abstract syntax (if CULR-3 default is used, this - line is 06 06 28D734030101) 30 80 {11 06 La xxxxxx - [OID] t-s name for application data - (if CULR-3 default is used, this line is - 06 06 28D734030201) -- will be several of these if multiple t-s offered -- (application is Group III) -- all will have the same tag 06 00 00 }11 - end transfer syntax list for application p-ctx 00 00 }10 - end application pctx definitionFurniss [Page 18] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994 -- if multiple presentation contexts are offered, (Group -- IV), the {10} SEQUENCE will repeat appropriately -- if multiple contexts are to be accepted, all the -- pcid's must be remembered 00 00 }8 - end of p-ctx-def-list * La ? 61 80 {12 - [APPLICATION 1] User-data - Fully-encoded 30 80 {13 - [SEQUENCE] PDV-list 02 01 01 -- [INTEGER], value is acse pcid A0 80 {14 - [0] Single-ASN1 - ACSE A-ASSOCIATE request APDU - AARQ 60 80 {15 - [APPLICATION 0] - AARQ * La ? - protocol version defaults to 1 (only one defined) A1 80 { - [1] Application-context 06 La xxxxxx -- object identifier name of application context - (if CULR-3 default is used, this line is - 06 05 28D7340303) 00 00 } -- Called application process title {16} and application -- entity qualifier may or may not be needed (see 3.4) ?A2 80 {16 - [2] Called Application-Process title ?! La xxxxxx -- see 3.5 - either a Directory Name or an oid ?00 00 }16 - end Called APtitle ?A3 80 {17 - [3] Called Application-Entity Qualifier ?! La xxxxxx -- see 3.5 ?00 00 }17 * La ? Calling AP-title and AE-qualifier may or may not be needed. ?A6 80 {18 - [6] Calling Application-Process title ?! La xxxxxx -- see 3.5 ?00 00 }18 ?A7 80 {19 - [7] Calling Application-Entity Qualifier ?! La xxxxxx -- see 3.5 ?00 00 }19 * La ? -- the user information field may or may not be required -- (not required for Group I) ?BE 80 {20 - [30] IMPLICIT SEQUENCE ?28 80 {21 - [EXTERNAL] ?06 La xxxxxx -- [OID] This is the oid identifying the transfer -- syntax used for the user data. -- It is (almost certainly) required even if only -- one transfer syntax was proposed. ?02 01 03 - [INTEGER] this is the pcid for the application - data ?A0 La xxxxxx -- [0] single-ASN.1-type - the application data -- (see paragraph at end of this section below} ?00 00 }21 - end of EXTERNALFurniss [Page 19] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994 -- conceivably there may be several EXTERNALS, probably in -- different presentation contexts (different pcids) ?00 00 }20 - end of user information field 00 00 }15 - end of AARQ 00 00 }14 - end of single-ASN-type 00 00 }13 - end of PDV-list 00 00 }12 - end of Presentation User-data 00 00 }7 - end of third element of CP-type SET 00 00 }5 - end of CP-type The application data carried in the EXTERNAL is shown (as A0 La xxxx) assuming it is a single-ASN.1 type, which it often will be for group II (since these tend to be OSI applications). The xxxx will be the BER encoding of the application pdu (probably something like Z-BIND or Y- INITIALIZE). The length may be indefinite. If the application data is not a single ASN.1 type, but is an octet- aligned value, the A0 La xxxx is replaced by 81 La xxxx, where xxxx is the value. In this case the length must be definite (unless an "unnecessary" constructed encoding is used.) Identical considerations apply to the other EXTERNALs carried in the ACSE pdus.6.2 Successful reply to connection setup If the connection attempt is successful, the following is sent to the initiator on a T-DATA. 0E Ls {1 - ACCEPT SPDU * Ls ? 05 06 {2 - Connect/Accept Item 13 01 00 - Protocol Options * Ls ? 16 01 02 - version number (this shows version 2 only) -- if version 2 was not offered, omit all of {2} * Ls ? 14 02 0002 - Session User Requirements (functional units) - duplex fu only (kernel is automatic) * Ls ? C1 Ls {3 -- User Data. - CPA - P-CONNECT response 31 80 {4 - [SET] -- again, Mode-selector could come at the end A0 80 { - Mode-selector [0] 80 01 01 - normal mode - [0], length=1, value=1 00 00 } A2 80 {5 - [2] SEQUENCE (unnamed)Furniss [Page 20] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994 * La ? A5 80 {6 - [5] P-context-definition-result-list -- following result items are in the order -- corresponding to the pctx-definition-list in -- the connect -- this example assumes that was ACSE, user, rubbish -- with rubbish rejected 30 80 {7 - [SEQUENCE] result item for acse 80 01 00 -- [0] result, value 0 is acceptance 81 02 5101 - [1] accepted transfer syntax name = BER - note that this has an implicit tag, not 06 00 00 }7 - end result item for acse p-ctx 30 80 {8 - [SEQUENCE] result item for application-data pctx 80 01 00 - [0] value 0 is acceptance 81 La xxxxxx - [1] oid for transfer syntax, as on definition list -- if there were several (groupIII) , the one you -- liked most 00 00 }8 - end result item for app-data p-ctx 00 00 }6 - end p-ctx-def-result-list * La ? 61 80 {10 - [APPLICATION 1] User-data, Fully-encoded 30 80 {11 - [SEQUENCE] PDV-list 02 01 01 -- [INTEGER] value is pcid for ACSE, as stored from -- the pctx-definition-list on the P-CONNECT -- request A0 80 {12 - [0] single-ASN1-type - A-ASSOCIATE response APDU - AARE 61 80 {13 - [APPLICATION 1] identifies AARE * La ? A1 80 {14 - [1] Application-context 06 La xxxxxx - [OID] name of application context - usually the same as on AARQ, can differ 00 00 }14 A2 03 {15 - [2] result 02 01 00 - [INTEGER] value 0 means accepted 00 00 }15 A3 80 {16 - [3] result-source-diagnostic - (curiously, a non-optional field) A1 80 {17 - [1] acse-service-user 02 01 00 - [INTEGER] value 0 = null ! (why no implicit tag) 00 00 }17 - end acse-service-user 00 00 }16 - end result source diagnostic * La ? -- the user information field may or may not be required - (not used for Group I) ?BE 80 {20 - [30] IMPLICIT SEQUENCEFurniss [Page 21] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994 ?28 80 {21 - [EXTERNAL] -- the transfer-syntax oid is not present this time ?02 01 03 - [INTEGER] this is the pcid for the application - data ?A0 La xxxx -- [0] single-ASN1-type (see note at end of 6.1) ?00 00 }21 - end of EXTERNAL -- conceivably there may be several EXTERNALS, probably in -- different presentation contexts (different pcids) ?00 00 }20 - end of user information field 00 00 }13 - end AARE 00 00 }12 - end single-asn1-type 00 00 }11 - end PDV-list 00 00 }10 - end Presn user-data 00 00 }5 - end [2] implicit sequence in cpa 00 00 }4 - end CPA-type set The following sequence are the octets need to reject a presentation context that was offered in the presentation-context-definition-list. Since the result-list matches the definition list by position, it is placed at the corresponding point within {6} (e.g., it would come immediately after {8}, if the rejected context was the third one. -- next SEQUENCE is a rejection of a pctx 30 80 {9 - [SEQUENCE] result item for a rejected pctx 80 01 02 -- [0] result, value 2 is provider rejection 82 01 00 - [2] reason, value 0 is reason-not-specified -- there are other reasons, but let's keep it -- simple 00 00 }9 - end result item for rejected pctx6.3 Connection rejection Refusal is at session-level, but by session user, with no reason given. This is a compromise avoiding making unfounded accusations of (session) protocol misbehaviour. If the implementation finds it does not like the received message, it is not essential to attempt to communicate with the partner why, though this may be helpful if the reason is correctly identified. (In most cases, a wise implementor will make sure an error message goes somewhere or other). 0C 03 {1 - REFUSE SPDU * Ls ? 32 01 00 - rejected by SS-user, no reason The far-end may send interesting things explaining why you are not getting interworking. If this is a session reason, the reason code will one octet between 81 and 86. If the rejection is higher than session, this will be carried on S-REFUSE (so first octet is stillFurniss [Page 22] RFC 1698 ThinOSI Upper-Layers Cookbook October 1994⌨️ 快捷键说明
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