rfc2886.txt

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RFC 2886                     Megaco Errata                   August 2000


   AmmRequest ::= SEQUENCE
   {
           terminationID           TerminationIDList,
           descriptors             SEQUENCE OF AmmDescriptor,
           -- At most one descriptor of each type (see AmmDescriptor)
           -- allowed in the sequence
           ...
   }

   AmmDescriptor ::= CHOICE
   {
           mediaDescriptor         MediaDescriptor,
           modemDescriptor         ModemDescriptor,
           muxDescriptor           MuxDescriptor,
           eventsDescriptor        EventsDescriptor,
           eventBufferDescriptor   EventBufferDescriptor,
           signalsDescriptor       SignalsDescriptor,
           digitMapDescriptor      DigitMapDescriptor,
           auditDescriptor         AuditDescriptor,
           ...
   }

   Section: 7.2.3 "Subtract"
   ----------
   Issue: cannot use the CHOOSE wildcard for terminationId of a Subtract
   command.

   Resolution: add this qualification to the second sentence, which
   indicates that terminationId may be wildcarded.

   Section: 7.2.4 "Move"
   ----------
   Issue: cannot use the CHOOSE wildcard for terminationId of a Move
   command.

   Resolution: add this qualification to the second sentence, which
   indicates that terminationId may be wildcarded.

   Section: 7.2.5 "AuditValue"
   ----------
   Issue: Not clear whether AuditValue of ObservedEventsDescriptor
   reports events captured in current dial string of active digit map.

   Resolution: Add text to indicate that if a digit map is active and
   ObservedEventsDescriptor is specified the response to an AuditValue
   includes a digit map completion event which shows the current dial
   string but does not show a termination method.




Taylor                      Standards Track                     [Page 8]

RFC 2886                     Megaco Errata                   August 2000


   Issue: Fails to indicate what AuditValue for EventBufferDescriptor
   returns

   Resolution: Add the following text: "EventBuffer returns the set of
   events and associated parameter values currently enabled in the
   EventBufferDescriptor."

   Issue: not clear whether wildcarded context includes the null
   context.

   Resolution: add statement that ALL as a contextID does not include
   the null context.

   Issue: the text of 7.2.5 allows retrieval of multiple digit maps with
   one AuditValue command if the terminationId is ALL.  Moreover,
   earlier text in the Annex anticipates that multiple instances of a
   descriptor may be returned.  The comment in front of production
   auditReturnParameter in Annex B.2 contradicts this text.  Note that
   Annex A has no restriction on the number of instances of any
   descriptor in either a command or a response.

   Proposed Resolution: delete the"at-most-once" comment preceding ABNF
   production auditReturnParameter.

   Issue: Does not indicate how an audit of digit maps returns unnamed
   digit maps.

   Resolution: Change syntax of DigitMapDescriptor to allow return of
   unnamed digit maps as follows:

   digitMapDescriptor = DigitMapToken EQUAL
                        ( (LBRKT digitMapValue RBRKT)
                        / (digitMapname [ LBRKT digitMapValue RBRKT ])
                        ) and

   DigitMapDescriptor ::= SEQUENCE {
           digitMapName    DigitMapName OPTIONAL,
           digitMapValue   DigitMapValue OPTIONAL }

   Issue: the text in section 7.2.5 mentions that using an empty Audit
   descriptor with a wildcarded terminationId is a way to get a list of
   the terminations in the context.  Annex A provides the possibility
   that the auditReply may be a contextAuditResult of type
   terminationIdList, and Annex B allows for an auditReply containing a
   contextTerminationAudit which in turn presents a terminationIdList.
   The connection between the text in 7.2.5 and these special forms of
   audit result is not clear.  Moreover, a note at the beginning of
   Annex A section A.2 limits terminationIdList to one terminationId.



Taylor                      Standards Track                     [Page 9]

RFC 2886                     Megaco Errata                   August 2000


   Proposed Resolution: add the following text in section 7.2.5 after
   the sentence "This may be useful to get a list of TerminationIDs when
   used with wildcard.":  "Annexes A and B provide a special syntax for
   presenting such a list in condensed form, such that the AuditValue
   command tag does not have to be repeated for each terminationId."
   Also, in the Note at the beginning of section A.2 of Annex A, provide
   an exception on the length of type TerminationIdList when used in
   contextAuditResult.

   Section: 7.2.6 "AuditCapabilities"
   ----------
   Issue: Fails to indicate what AuditCapabilities for
   EventBufferDescriptor returns

   Resolution: Add the following text: "EventBuffer returns the same
   information as Events."

   Issue: Inconsistency regarding permissibility of DigitMap or Packages
   as capability audit items.

   Resolution: Add comment to B.2 "auditItem" production indicating that
   DigitMap and Packages are not allowed in the AuditCapabilities
   command.

   Section: 7.2.8 "ServiceChange"
   ----------
   Issue: In point 1) describing the Graceful ServiceChange method, the
   scope of the recommendation against new connections is unclear.

   Resolution: at the end of the first sentence, add the phrase "on the
   termination(s) affected by the ServiceChange command".

   Issue: the explanatory string associated with ServiceChangeReason is
   optional in the syntax, but not in the text.

   Resolution: add "optional" before "explanatory string" in the
   explanation of the ServiceChangeReason" parameter.

   Issue: Paragraph beginning "A ServiceChange Command specifying the
   Root..." immediately following the description of ServiceChange
   Descriptor parameters erroneously states that the response to the
   ServiceChange command terminates the registration process.  This is
   so only if the response does not specify an alternate MGC.

   Resolution: Add text to the offending sentence, so that it reads:
   "Acknowledgement of the ServiceChange Command completes the
   registration process, except when the MGC has returned an alternative
   ServiceChangeMgcId as described in the next paragraph."



Taylor                      Standards Track                    [Page 10]

RFC 2886                     Megaco Errata                   August 2000


   Section: 7.3 "Command Error Codes"
   ----------
   Issue: Text for error code 403 should be consistent with that for 404
   and 405.

   Resolution: Change text to "Syntax error in TransactionRequest"

   Issue: There should be no error responses to TransactionReply or
   TransactionPending, lest they create response loops.

   Resolution: Delete codes 404, 405, 461-467

   Section: 8 "Transactions", A.2
   ----------
   Issue: state is unclear if a command fails.

   Resolution: add the following text:  "If a command fails, the MG
   shall as far as possible restore the state which prevailed prior to
   the attempted execution of the command before continuing with
   transaction processing."

   Section: 8.1.1 "Transaction Identifiers"
   ----------
   Issue: need a transaction identifier to use when reporting a syntax
   error such that the identifier is unavailable.

   Resolution: add text reserving transionId = 0 for this purpose.

   Section: 8.1.2 "Context Identifiers"
   ----------
   Issue: ALL as a context identifier does not include the null context.

   Resolution: add text to indicate that exclusion in the final sentence
   of the section.

   Section: 8.2.2 "TransactionReply"
   ----------
   Issue: Final para has wrong text for error code 442.

   Resolution: Change to "Syntax Error in Command"

   Section: 10.2 "Interim AH Scheme", B.2
   ----------
   Issue: The interim AH header can actually be as short as 24 hex
   digits (per RFCs 2403, 2404 which are indirectly referenced).  It is
   also unclear whether it is the source or destination UDP port which
   is prepended in the calculation.




Taylor                      Standards Track                    [Page 11]

RFC 2886                     Megaco Errata                   August 2000


   Resolution: Change 10.2 second para, second-last sentence to specify
   the destination port, in consistency with IPSEC.  In Annex B.2,
   change lower count for production AuthData to 24 from 32.

   Section: 11.2 "Cold Start"
   ----------
   Issue: First paragraph last sentence inadvertently modified --
   duplicates material in 11.3.

   Resolution: Restore original sentence: "If the MG is unable to
   establish a control relationship with any MGC, it shall wait a random
   amount of time as described in Section 9.2 and then start contacting
   its primary, and if necessary, its secondary MGCs again."

   Section: 11.4 "Failure Of an MG"
   ----------
   Issue: Second para: wrong MG is specified as the one to be used after
   failover.

   Resolution: Change fourth sentence to refer to "secondary MG" rather
   than "primary MG".

   Section: 12.1.2 "Properties"
   ----------
   Issue: As indicated in 6.2.4, Properties occur in other descriptors
   besides LocalControl and TerminationState.

   Resolution: after the sentence mentioning TerminationState, add
   another sentence:  "Although these are the most common cases, it is
   also possible for a property to be defined for other descriptors."

   Section: 12.1.4 "Signals"
   ----------
   Issue: Note says that default duration should be specified for BR
   signals.  This also applies to TO signals.

   Resolution: Add TO signals to note.

   Section: 12.2 "Guidelines to defining  Properties, Statistics and
   Parameters to Events and Signals", B.2
   ----------
   Issue: Text indicates that statistics can have the sub-list data
   type, but ABNF does not support that.

   Resolution: qualify the sublist type by adding the note:  "(not
   supported for statistics)".





Taylor                      Standards Track                    [Page 12]

RFC 2886                     Megaco Errata                   August 2000


   Section: Annex A.1, ASN.1 Syntax
   ----------
   Issue: the ASN.1 uses the values 0x0, 0xFFFFFFFE, and 0xFFFFFFFF for
   the NULL context, a wildcard CHOOSE of context, and a wildcard ALL of
   context respectively.  Because of the possibility of a switch between
   binary and text encoding for messages relating to the same context,
   these values should be reserved in the text encoded syntax.

   Resolution: Add a comment preceding the ContextID production in Annex
   B.2 indicating that these values are reserved.

   Section: Annex A.2, ASN.1 Syntax
   ----------
   Issue: sloppy ASN.1 -- in production EventBufferControl the values
   "off" and "lockstep" should not be capitalized, and IA5STRING in
   production NonStandardIdentifier should be IA5String.  Both
   TransactionID and TransactionId are used.  A number of productions
   need ellipses to express extensibility.

   Resolution: fix them.

   Issue: syntax for PropertyParm does not support sub-lists (i.e.
   parameters supporting multiple values simultaneously)

   Resolution: add a third choice to extrainfo in PropertyParm as
   follows:

            extraInfo   CHOICE
        {
                relation        Relation,
                range           BOOLEAN,
                sublist         BOOLEAN
        } OPTIONAL

   and add an appropriate note to the preceding comments.

   Issue: LocalControlDescriptor still contains reserve rather than
   reserveValue and reserveGroup.

   Resolution: Replace reserve with separate reserveValue and
   reserveGroup Booleans.

   Issue: EventBufferDescriptor is incorrectly portrayed as a SEQUENCE
   OF ObservedEvent.

   Resolution: replace with the following productions:





Taylor                      Standards Track                    [Page 13]

RFC 2886                     Megaco Errata                   August 2000


   EventBufferDescriptor ::= SEQUENCE OF EventSpec

   EventSpec ::= SEQUENCE {
        pkgdName                PkgdName,
        streamID                StreamID OPTIONAL,
        evParList               SEQUENCE OF EventParameter }

   Issue: Assigned object identifier missing.  It is usually present as
   a matter of convention.

   Resolution: Add object identifier line in the message header with
   content:
       "itu-t recommendation h 248 media-gateway-control(0)" Delete the
   version field, which this makes redundant.

   Issue: the T.35 country code in the H221NonStandard production does
   not have the right structure.

   Resolution: fix it.

   Section: Annex B.2, ABNF Syntax
   ----------
   Issue: Syntax for parmValue and VALUE together make parsing of range
   ambiguous.  Furthermore, sub-lists and sets of alternative values
   have the same syntax, introducing possible ambiguity

   Resolution: Replace production alternativeValue by the following:
     "alternativeValue = ( VALUE
          / LSBRKT VALUE *(COMMA VALUE) RSBRKT     ; sub-list
          / LBRKT VALUE *(COMMA VALUE) RBRKT       ; alternatives
          / LSBRKT VALUE COLON VALUE RSBRKT )      ; range"

   Issue: EventBufferDescriptor content mistakenly shown as a sequence
   of observedEvent.

   Resolution: replace the production for eventBufferDescriptor with the
   following productions:

   eventBufferDescriptor = EventBufferToken LBRKT [ eventSpec
      *( COMMA eventSpec ) ] RBRKT

   eventSpec = pkgdName [ LBRKT  eventSpecParameter
                          *( COMMA eventSpecParameter ) RBRKT ]

   eventSpecParameter = ( eventStream / eventOther )

   Issue: Error in syntax for  digitMapDescriptor: value meant to be
   optional.



Taylor                      Standards Track                    [Page 14]

RFC 2886                     Megaco Errata                   August 2000