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RFC 3525

Gateway Control Protocol Version 1

Pages: 213
Obsoletes:  3015
Obsoleted by:  5125
Part 5 of 7 – Pages 128 to 156
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ANNEX C - Tags for media stream properties

Parameters for Local, Remote and LocalControl descriptors are specified as tag-value pairs if binary encoding is used for the protocol. This annex contains the property names (PropertyID), the tags (Property tag), type of the property (Type) and the values (Value). Values presented in the Value field when the field contains references shall be regarded as "information". The reference contains the normative values. If a value field does not contain a reference, then the values in that field can be considered as "normative". Tags are given as hexadecimal numbers in this annex. When setting the value of a property, a MGC may underspecify the value according to one of the mechanisms specified in 7.1.1. It is optional to support the properties in this Annex or any of its sub-sections. For example, only three properties from C.3 and only five properties from C.8 might be implemented. For type "enumeration" the value is represented by the value in brackets, e.g., Send(0), Receive(1). Annex C properties with the types "N bits" or "M Octets" should be treated as octet strings when encoding the protocol. Properties with "N bit integer" shall be treated as an integers. "String" shall be treated as an IA5String when encoding the protocol. When a type is smaller than one octet, the value shall be stored in the low-order bits of an octet string of size 1.

C.1 General media attributes

PropertyID Property Type Value tag Media 1001 Enumeration Audio(0), Video(1), Data(2) Transmission 1002 Enumeration Send(0), Receive(1), mode Send&Receive(2) Number of 1003 Unsigned 0-255 Channels integer Sampling 1004 Unsigned 0-2^32 rate integer Bitrate 1005 Integer (0..4294967295)NOTE - Units of 100 bit/s.
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   ACodec        1006     Octet string  Audio Codec Type:
                                        Ref.: ITU-T Q.765
                                        Non-ITU-T codecs are defined
                                        with the appropriate standards
                                        organization under a defined
                                        Organizational Identifier.

   Samplepp      1007     Unsigned      Maximum samples or frames per
                          integer       packet: 0..65535

   Silencesupp   1008     Boolean       Silence Suppression: True/False

   Encrypttype   1009     Octet string  Ref.: ITU-T H.245

   Encryptkey    100A     Octet string  Encryption key
                          size          Ref.: ITU-T H.235
                          (0..65535)

   Echocanc      100B                    Not Used.  See H.248.1 E.13 for
                                        an example of possible Echo
                                        Control properties.

   Gain          100C     Unsigned      Gain in dB: 0..65535
                          integer

   Jitterbuff    100D     Unsigned      Jitter buffer size in ms:
                          integer       0..65535

   PropDelay     100E     Unsigned      Propagation Delay: 0..65535
                          integer       Maximum propagation delay in
                                        milliseconds for the bearer
                                        connection between two media
                                        gateways.  The maximum delay
                                        will be dependent on the bearer
                                        technology.

   RTPpayload    100F     Integer       Payload type in RTP Profile for
                                        Audio and Video Conferences
                                        with Minimal Control
                                        Ref.: RFC 1890
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C.2 Mux properties

PropertyID Property tag Type Value H222 2001 Octet string H222LogicalChannelParameters Ref.: ITU-T H.245 H223 2002 Octet string H223LogicalChannelParameters Ref.: ITU-T H.245 V76 2003 Octet string V76LogicalChannelParameters Ref.: ITU-T H.245 H2250 2004 Octet string H2250LogicalChannelParameters Ref.: ITU-T H.245

C.3 General bearer properties

PropertyID Property Type Value tag Mediatx 3001 Enumeration Media Transport TypeTDM Circuit(0), ATM(1), FR(2), Ipv4(3), Ipv6(4), ... BIR 3002 4 octets Value depends on transport technology NSAP 3003 1-20 octets See NSAP. Ref.: Annex A/X.213

C.4 General ATM properties

PropertyID Property Type Value tag AESA 4001 20 octets ATM End System Address VPVC 4002 4 octets: VPCI VPCI/VCI in first two least Ref.: ITU-T Q.2931 significant octets, VCI in second two octets
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   SC         4003     Enumeration       Service Category: CBR(0),
                                          nrt-VBR1(1), nrt  VBR2(2),
                                          nrt-VBR3(3), rt-VBR1(4),
                                          rt  VBR2(5), rt-VBR3(6),
                                          UBR1(7), UBR2(8), ABR(9).
                                          Ref.: ATM Forum UNI 4.0

   BCOB       4004     5-bit integer     Broadband Bearer Class
                                          Ref.: ITU-T Q.2961.2

   BBTC       4005     7-bit integer     Broadband Transfer Capability
                                          Ref.: ITU-T Q.2961.1

   ATC        4006     Enumeration       I.371 ATM Traffic
                                          CapabilityDBR(0), SBR1(1),
                                          SBR2(2), SBR3(3), ABT/IT(4),
                                          ABT/DT(5), ABR(6)
                                          Ref.: ITU-T I.371

   STC        4007     2 bits            Susceptibility to clipping:
                                          Bits
                                          2 1
                                          ---
                                          0 0     not susceptible to
                                                  clipping
                                          0 1     susceptible to
                                                  clipping
                                          Ref.: ITU-T Q.2931

   UPCC       4008     2 bits            User Plane Connection
                                          configuration:
                                          Bits
                                          2 1
                                          ---
                                          0 0     point-to-point
                                          0 1     point-to-multipoint
                                          Ref.: ITU-T Q.2931

   PCR0       4009     24-bit integer    Peak Cell Rate (For CLP = 0)
                                          Ref.: ITU-T Q.2931

   SCR0       400A     24-bit integer    Sustainable Cell Rate (For
                                          CLP = 0)
                                          Ref.: ITU-T Q.2961.1

   MBS0       400B     24-bit integer    Maximum Burst Size (For CLP =
                                          0)
                                          Ref.: ITU-T Q.2961.1
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   PCR1       400C     24-bit integer    Peak Cell Rate (For CLP = 0 +
                                          1)
                                          Ref.: ITU-T Q.2931

   SCR1       400D     24-bit integer    Sustainable Cell Rate (For
                                          CLP = 0 + 1)
                                          Ref.: ITU-T Q.2961.1

   MBS1       400E     24-bit integer    Maximum Burst Size (For CLP =
                                          0 + 1)
                                          Ref.: ITU-T Q.2961.1

   BEI        400F     Boolean           Best Effort Indicator
                                          Value 1 indicates that BEI is
                                          to be included in the ATM
                                          signaling; value 0 indicates
                                          that BEI is not to be
                                          included in the ATM
                                          signaling.
                                          Ref.: ATM Forum UNI 4.0

   TI         4010     Boolean           Tagging Indicator
                                          Value 0 indicates that
                                          tagging is not allowed; value
                                          1 indicates that tagging is
                                          requested.
                                          Ref.: ITU-T Q.2961.1

   FD         4011     Boolean           Frame Discard
                                          Value 0 indicates that no
                                          frame discard is allowed;
                                          value 1 indicates that frame
                                          discard is allowed.
                                          Ref.: ATM Forum UNI 4.0

   A2PCDV     4012     24-bit integer    Acceptable 2-point CDV
                                          Ref.: ITU-T Q.2965.2

   C2PCDV     4013     24-bit integer    Cumulative 2-point CDV
                                          Ref.: ITU-T Q.2965.2

   APPCDV     4014     24-bit integer    Acceptable P-P CDV
                                          Ref.: ATM Forum UNI 4.0

   CPPCDV     4015     24-bit integer    Cumulative P-P CDV
                                          Ref.: ATM Forum UNI 4.0
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   ACLR       4016     8-bit integer     Acceptable Cell Loss Ratio
                                          Ref.: ITU-T Q.2965.2, ATM
                                          Forum UNI 4.0

   MEETD      4017     16-bit integer    Maximum End-to-end transit
                                          delay
                                          Ref.: ITU-T Q.2965.2, ATM
                                          Forum UNI 4.0

   CEETD      4018     16-bit integer    Cumulative End-to-end transit
                                          delay
                                          Ref.: ITU-T Q.2965.2, ATM
                                          Forum UNI 4.0

   QosClass   4019     Integer 0-5          QoS Class

                                            QoS Class     Meaning

                                            0             Default QoS
                                                           associated
                                                           with the ATC
                                                           as defined
                                                           in ITU-T
                                                           Q.2961.2

                                            1             Stringent

                                            2             Tolerant

                                            3             Bi-level

                                            4             Unbounded

                                            5             Stringent
                                                           Bi-level
                                          Ref.: ITU-T Q.2965.1

   AALtype    401A     1 octet           AAL Type
                                          Bits
                                          8 7 6 5 4 3 2 1
                                          ---------------
                                          0 0 0 0 0 0 0 0   AAL for
                                                            voice
                                          0 0 0 0 0 0 0 1   AAL type 1
                                          0 0 0 0 0 0 1 0   AAL type 2
                                          0 0 0 0 0 0 1 1   AAL type
                                                            3/4
                                          0 0 0 0 0 1 0 1   AAL type 5
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                                          0 0 0 1 0 0 0 0   user-
                                                            defined AAL
                                          Ref.: ITU-T Q.2931

C.5 Frame Relay

PropertyID Property Type Value tag DLCI 5001 Unsigned Data link connection integer id CID 5002 Unsigned sub-channel id integer SID/Noiselevel 5003 Unsigned silence insertion integer descriptor Primary Payload 5004 Unsigned Primary Payload Type type integer Covers FAX and codecs

C.6 IP

PropertyID Property tag Type Value IPv4 6001 32 bits Ipv4Address Ipv4Address Ref.: IETF RFC 791 IPv6 6002 128 bits IPv6 Address Ref.: IETF RFC 2460 Port 6003 Unsigned integer 0..65535 Porttype 6004 Enumerated TCP(0), UDP(1), SCTP(2)

C.7 ATM AAL2

PropertyID Property Type Value tag AESA 7001 20 octets AAL2 service endpoint address as defined in the referenced Recommendation. ESEANSEA Ref.: ITU-T Q.2630.1
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   BIR        See C.3  4 octets               Served user generated
                                                reference as defined in
                                                the referenced
                                                Recommendation.
                                                SUGR
                                                Ref.: ITU-T Q.2630.1

   ALC        7002     12 octets              AAL2 link
                                                characteristics as
                                                defined in the
                                                referenced
                                                Recommendation.
                                                Maximum/Average CPS-SDU
                                                bit rate;
                                                Maximum/Average CPS-SDU
                                                size
                                                Ref.: ITU-T Q.2630.1

   SSCS       7003     I.366.2: Audio (8      Service specific
                        octets); Multirate (3  convergence sublayer
                        octets), or I.366.1:   information as defined
                        SAR-assured (14        in:
                        octets);SAR-unassured  - ITU-T Q.2630.1,and
                        (7 octets).            used in:
                                                - ITU-T I.366.2:
                                                Audio/Multirate;
                                                - ITU-T I.366.1: SAR-
                                                assured/unassured.
                                                Ref.: ITU-T Q.2630.1,
                                                I.366.1 and I.366.2

   SUT        7004     1..254 octets          Served user transport
                                                parameter as defined in
                                                the referenced
                                                Recommendation.
                                                Ref.: ITU-T Q.2630.1

   TCI        7005     Boolean                Test connection
                                                indicator as defined in
                                                the referenced
                                                Recommendation.
                                                Ref.: ITU-T Q.2630.1

   Timer_CU   7006     32-bit integer         Timer-CU
                                                Milliseconds to hold
                                                partially filled cell
                                                before sending.
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   MaxCPSSDU  7007     8-bit integer          Maximum Common Part
                                                Sublayer Service Data
                                                Unit
                                                Ref.: ITU-T Q.2630.1

   CID        7008     8 bits                 subchannel id: 0-255
                                                Ref.: ITU-T I.363.2

C.8 ATM AAL1

PropertyID Property Type Value tag BIR See table 4-29 octets GIT (Generic Identifier in C.3 Transport) Ref.: ITU-T Q.2941.1 AAL1ST 8001 1 octet AAL1 Subtype Bits 8 7 6 5 4 3 2 1 --------------- 0 0 0 0 0 0 0 0 null 0 0 0 0 0 0 0 1 voiceband signal transport on 64 kbit/s 0 0 0 0 0 0 1 0 circuit transport 0 0 0 0 0 1 0 0 high-quality audio signal transport 0 0 0 0 0 1 0 1 video signal transport Ref.: ITU-T Q.2931 CBRR 8002 1 octet CBR Rate Bits 8 7 6 5 4 3 2 1 --------------- 0 0 0 0 0 0 0 1 64 kbit/s 0 0 0 0 0 1 0 0 1544 kbit/s 0 0 0 0 0 1 0 1 6312 kbit/s 0 0 0 0 0 1 1 0 32 064 kbit/s 0 0 0 0 0 1 1 1 44 736 kbit/s 0 0 0 0 1 0 0 0 97 728 kbit/s 0 0 0 1 0 0 0 0 2048 kbit/s 0 0 0 1 0 0 0 1 8448 kbit/s 0 0 0 1 0 0 1 0 34 368 kbit/s 0 0 0 1 0 0 1 1 139 264 kbit/s 0 1 0 0 0 0 0 0 n x 64 kbit/s 0 1 0 0 0 0 0 1 n x 8 kbit/s Ref.: ITU-T Q.2931
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   MULT       See table              Multiplier, or n x 64k/8k/300
              in C.9                 Ref.: ITU-T Q.2931

   SCRI       8003       1 octet     Source Clock Frequency Recovery
                                      Method
                                      Bits
                                      8 7 6 5 4 3 2 1
                                      ---------------
                                      0 0 0 0 0 0 0 0     null
                                      0 0 0 0 0 0 0 1     SRTS
                                      0 0 0 0 0 0 1 0     ACM
                                      Ref.: ITU-T Q.2931

   ECM        8004       1 octet     Error Correction Method
                                      Bits
                                      8 7 6 5 4 3 2 1
                                      ---------------
                                      0 0 0 0 0 0 0 0     null
                                      0 0 0 0 0 0 0 1     FEC - Loss
                                      0 0 0 0 0 0 1 0     FEC - Delay
                                      Ref.: ITU-T Q.2931

   SDTB       8005       16-bit      Structured Data Transfer
                         integer     Blocksize
                                      Block size of SDT CBR service
                                      Ref.: ITU-T I.363.1

   PFCI       8006       8-bit       Partially filled cells identifier
                         integer     1-47
                                      Ref.: ITU-T I.363.1

C.9 Bearer capabilities

The table entries referencing Recommendation Q.931 refer to the encoding in the bearer capability information element of Q.931, not to the low layer information element. PropertyID Tag Type Value TMR 9001 1 octet Transmission Medium Requirement (Q.763) Bits 87654321 -------- 00000000 speech 00000001 spare 00000010 64 kbit/s unrestricted
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                                  00000011  3.1 kHz audio
                                  00000100  reserved for
                                  alternate speech (service
                                  2)/64 kbit/s unrestricted
                                  (service 1)
                                  00000101  reserved for
                                  alternate 64 kbit/s
                                  unrestricted (service
                                  1)/speech (service 2)
                                  00000110  64 kbit/s preferred

                                  The assigned codepoints
                                  listed below are all for
                                  unrestricted service.
                                  00000111  2 x 64 kbit/s
                                  00001000  384 kbit/s
                                  00001001  1536 kbit/s
                                  00001010  1920 kbit/s
                                  00001011
                                   through
                                  00001111  spare
                                  00010000
                                   through
                                  00101010:
                                     3 x 64 kbit/s through
                                    29 x 64 kbit/s
                                  except
                                  00010011  spare
                                  00100101  spare

                                  00101011
                                   through
                                  11111111  spare
                                  Ref.: ITU-T Q.763

   TMRSR         9002   1 octet   Transmission Medium
                                  Requirement Subrate
                                  0     unspecified
                                  1      8 kbit/s
                                  2     16 kbit/s
                                  3     32 kbit/s

   Contcheck     9003   Boolean   Continuity Check
                                  0     continuity check not
                                  required on this circuit
                                  1     continuity check
                                  required on this circuit
                                  Ref.: ITU-T Q.763
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   ITC           9004   5 bits    Information Transfer
                                  Capability
                                  Bits
                                  5 4 3 2 1
                                  ---------
                                  0 0 0 0 0     Speech
                                  0 1 0 0 0     Unrestricted
                                  digital information
                                  0 1 0 0 1     Restricted
                                  digital information
                                  1 0 0 0 0     3.1 kHz audio
                                  1 0 0 0 1     Unrestricted
                                  digital information with
                                  tones/announcements
                                  1 1 0 0 0     Video
                                  All other values are
                                  reserved.
                                  Ref.: ITU-T Q.763

   TransMode     9005   2 bits    Transfer Mode
                                  Bits
                                  2 1
                                  ---
                                  0 0     Circuit mode
                                  1 0     Packet mode
                                  Ref.: ITU-T Q.931

   TransRate     9006   5 bits    Transfer Rate
                                  Bits
                                  5 4 3 2 1
                                  ---------
                                  0 0 0 0 0     This code shall
                                  be used for packet mode calls
                                  1 0 0 0 0      64 kbit/s
                                  1 0 0 0 1  2 x 64 kbit/s
                                  1 0 0 1 1     384 kbit/s
                                  1 0 1 0 1    1536 kbit/s
                                  1 0 1 1 1    1920 kbit/s
                                  1 1 0 0 0  Multirate (64
                                  kbit/s base rate)
                                  Ref.: ITU-T Q.931

   MULT          9007   7 bits    Rate Multiplier
                                  Any value from 2 to n
                                  (maximum number of B-
                                  channels)
                                  Ref.: ITU-T Q.931
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   layer1prot    9008   5 bits    User Information Layer 1
                                  Protocol
                                  Bits
                                  5 4 3 2 1
                                  ---------
                                  0 0 0 0 1     ITU-T
                                  standardized rate adaption
                                  V.110 and X.30.
                                  0 0 0 1 0     Recommendation
                                  G.711 m-law
                                  0 0 0 1 1     Recommendation
                                  G.711 A-law
                                  0 0 1 0 0     Recommendation
                                  G.721 32 kbit/s ADPCM and
                                  Recommendation I.460
                                  0 0 1 0 1     Recommendations
                                  H.221 and H.242
                                  0 0 1 1 0     Recommendations
                                  H.223 and H.245
                                  0 0 1 1 1     Non-ITU-T
                                  standardized rate adaption.
                                  0 1 0 0 0     ITU-T
                                  standardized rate adaption
                                  V.120.
                                  0 1 0 0 1     ITU-T
                                  standardized rate adaption
                                  X.31 HDLC flag stuffing
                                  All other values are
                                  reserved.
                                  Ref.: ITU Recommendation
                                  Q.931

   syncasync     9009   Boolean   Synchronous/Asynchronous
                                  0     Synchronous data
                                  1     Asynchronous data
                                  Ref.: ITU-T Q.931

   negotiation   900A   Boolean   Negotiation
                                  0     In-band negotiation
                                  possible
                                  1     In-band negotiation not
                                  possible
                                  Ref.: ITU-T Q.931

   Userrate      900B   5 bits    User Rate
                                  Bits
                                  5 4 3 2 1
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                                  ---------
                                  0 0 0 0 0     Rate is
                                  indicated by E-bits specified
                                  in Recommendation I.460 or
                                  may be negotiated in-band
                                  0 0 0 0 1     0.6 kbit/s
                                  Recommendations V.6 and X.1
                                  0 0 0 1 0     1.2 kbit/s
                                  Recommendation V.6
                                  0 0 0 1 1     2.4 kbit/s
                                  Recommendations V.6 and X.1
                                  0 0 1 0 0     3.6 kbit/s
                                  Recommendation V.6
                                  0 0 1 0 1     4.8 kbit/s
                                  Recommendations V.6 and X.1
                                  0 0 1 1 0     7.2 kbit/s
                                  Recommendation V.6
                                  0 0 1 1 1     8 kbit/s
                                  Recommendation I.460
                                  0 1 0 0 0     9.6 kbit/s
                                  Recommendations V.6 and X.1
                                  0 1 0 0 1     14.4 kbit/s
                                  Recommendation V.6
                                  0 1 0 1 0     16 kbit/s
                                  Recommendation I.460
                                  0 1 0 1 1     19.2 kbit/s
                                  Recommendation V.6
                                  0 1 1 0 0     32 kbit/s
                                  Recommendation I.460
                                  0 1 1 0 1     38.4 kbit/s
                                  Recommendation V.110
                                  0 1 1 1 0     48 kbit/s
                                  Recommendations V.6 and X.1
                                  0 1 1 1 1     56 kbit/s
                                  Recommendation V.6
                                  1 0 0 1 0     57.6 kbit/s
                                  Recommendation V.14 extended
                                  1 0 0 1 1     28.8 kbit/s
                                  Recommendation V.110
                                  1 0 1 0 0     24 kbit/s
                                  Recommendation V.110
                                  1 0 1 0 1     0.1345 kbit/s
                                  Recommendation X.1
                                  1 0 1 1 0     0.100 kbit/s
                                  Recommendation X.1
                                  1 0 1 1 1     0.075/1.2
                                  kbit/s Recommendations V.6
                                  and X.1
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                                  1 1 0 0 0     1.2/0.075
                                  kbit/s Recommendations V.6
                                  and X.1
                                  1 1 0 0 1     0.050 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 0 1 0     0.075 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 0 1 1     0.110 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 1 0 0     0.150 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 1 0 1     0.200 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 1 1 0     0.300 kbit/s
                                  Recommendations V.6 and X.1
                                  1 1 1 1 1     12 kbit/s
                                  Recommendation V.6
                                  All other values are
                                  reserved.
                                  Ref.: ITU-T Q.931
   INTRATE       900C   2 bits    Intermediate Rate
                                  Bits
                                  2 1
                                  ---
                                  0 0     Not used
                                  0 1     8 kbit/s
                                  1 0     16 kbit/s
                                  1 1     32 kbit/s
                                  Ref.: ITU-T Q.931

   nictx         900D   Boolean   Network Independent Clock
                                  (NIC) on transmission
                                  0     Not required to send
                                  data with network independent
                                  clock
                                  1     Required to send data
                                  with network independent
                                  clock
                                  Ref.: ITU-T Q.931

   nicrx         900E   Boolean   Network independent clock
                                  (NIC) on reception
                                  0     Cannot accept data with
                                  network independent clock
                                  (i.e., sender does not support
                                  this optional procedure)
                                  1     Can accept data with
                                  network independent clock
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                                  (i.e., sender does support
                                  this optional procedure)
                                  Ref.: ITU-T Q.931

   flowconttx    900F   Boolean   Flow Control on transmission
                                  (Tx)
                                  0     Not required to send
                                  data with flow control
                                  mechanism
                                  1     Required to send data
                                  with flow control mechanism
                                  Ref.: ITU-T Q.931

   flowcontrx    9010   Boolean   Flow control on reception
                                  (Rx)
                                  0     Cannot accept data with
                                  flow control mechanism (i.e.,
                                  sender does not support this
                                  optional procedure)
                                  1     Can accept data with
                                  flow control mechanism (i.e.,
                                  sender does support this
                                  optional procedure)
                                  Ref.: ITU-T Q.931

   rateadapthdr  9011   Boolean   Rate adaption header/no
                                  header
                                  0     Rate adaption header
                                  not included
                                  1     Rate adaption header
                                  included
                                  Ref.: ITU-T Q.931

   multiframe    9012   Boolean   Multiple frame establishment
                                  support in data link
                                  0     Multiple frame
                                  establishment not supported.
                                  Only UI frames allowed
                                  1     Multiple frame
                                  establishment supported
                                  Ref.: ITU-T Q.931

   OPMODE        9013   Boolean   Mode of operation
                                  0     Bit transparent mode of
                                  operation
                                  1     Protocol sensitive mode
                                  of operation
                                  Ref.: ITU-T Q.931
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   llidnegot     9014   Boolean   Logical link identifier
                                  negotiation
                                  0     Default, LLI = 256 only
                                  1     Full protocol
                                  negotiation
                                  Ref.: ITU-T Q.931

   assign        9015   Boolean   Assignor/assignee
                                  0     Message originator is
                                  "default assignee"
                                  1     Message originator is
                                  "assignor only"
                                  Ref.: ITU-T Q.931

   inbandneg     9016   Boolean   In-band/out-band negotiation
                                  0     Negotiation is done
                                  with USER INFORMATION
                                  messages on a temporary
                                  signalling connection
                                  1     Negotiation is done in-
                                  band using logical link zero
                                  Ref.: ITU-T Q.931

   stopbits      9017   2 bits    Number of stop bits
                                  Bits
                                  2 1
                                  ---
                                  0 0     Not used
                                  0 1     1 bit
                                  1 0     1.5 bits
                                  1 1     2 bits
                                  Ref.: ITU-T Q.931

   databits      9018   2 bits    Number of data bits excluding
                                  parity bit if present
                                  Bits
                                  2 1
                                  ---
                                  0 0     Not used
                                  0 1     5 bits
                                  1 0     7 bits
                                  1 1     8 bits
                                  Ref.: ITU-T Q.931

   parity        9019   3 bits    Parity information
                                  Bits
                                  3 2 1
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                                  ------
                                  0 0 0     Odd
                                  0 1 0     Even
                                  0 1 1     None
                                  1 0 0     Forced to 0
                                  1 0 1     Forced to 1
                                  All other values are
                                  reserved.
                                  Ref.: ITU-T Q.931

   duplexmode    901A   Boolean   Mode duplex
                                  0     Half duplex
                                  1     Full duplex
                                  Ref.: ITU-T Q.931

   modem         901B   6 bits    Modem Type
                                  Bits
                                  6 5 4 3 2 1
                                  -----------
                                  0 0 0 0 0 0 through
                                  0 0 0 1 0 1   National use
                                  0 1 0 0 0 1   Rec.  V.21
                                  0 1 0 0 1 0     Rec.  V.22
                                  0 1 0 0 1 1     Rec.  V.22 bis
                                  0 1 0 1 0 0     Rec.  V.23
                                  0 1 0 1 0 1     Rec.  V.26
                                  0 1 1 0 0 1     Rec.  V.26 bis
                                  0 1 0 1 1 1     Rec.  V.26 ter
                                  0 1 1 0 0 0     Rec.  V.27
                                  0 1 1 0 0 1     Rec.  V.27 bis
                                  0 1 1 0 1 0     Rec.  V.27 ter
                                  0 1 1 0 1 1     Rec.  V.29
                                  0 1 1 1 0 1     Rec.  V.32
                                  0 1 1 1 1 0     Rec.  V.34
                                  1 0 0 0 0 0  through
                                  1 0 1 1 1 1    National use
                                  1 1 0 0 0 0  through
                                  1 1 1 1 1 1    User specified
                                  Ref.: ITU-T Q.931

   layer2prot    901C   5 bits    User information layer 2
                                  protocol
                                  Bits
                                  5 4 3 2 1
                                  ---------
                                  0 0 0 1 0    Rec.  Q.921/I.441
                                  0 0 1 1 0    Rec.  X.25, link
                                  layer
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                                  0 1 1 0 0    LAN logical link
                                  control (ISO/IEC 8802  2)
                                  All other values are
                                  reserved.
                                  Ref.: ITU-T Q.931

   layer3prot    901D   5 bits    User information layer 3
                                  protocol
                                  Bits
                                  5 4 3 2 1
                                  ---------
                                  0 0 0 1 0     ITU-T Q.931
                                  0 0 1 1 0     ITU-T X.25,
                                  packet layer
                                  0 1 0 1 1     ISO/IEC TR 9577
                                  (Protocol identification in
                                  the network layer)
                                  All other values are
                                  reserved.
                                  Ref.: ITU-T Q.931

   addlayer3prot 901E   Octet     Additional User Information
                                  layer 3 protocol
                                  Bits        Bits
                                  4 3 2 1     4 3 2 1
                                  -------     -------
                                  1 1 0 0     1 1 0 0
                                  Internet Protocol (RFC 791)
                                  (ISO/IEC TR 9577)
                                  1 1 0 0     1 1 1 1
                                  Point-to-point Protocol (RFC
                                  1661)
                                  Ref.: ITU-T Q.931

   DialledN      901F   30        Dialled Number
                        octets

   DiallingN     9020   30        Dialling Number
                        octets

   ECHOCI        9021             Not Used.  See H.248.1 E.13
                                  for an example of possible
                                  Echo Control properties.

   NCI           9022   1 octet   Nature of Connection
                                  Indicators
                                  Bits
                                  2 1     Satellite Indicator
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                                  ---
                                  0 0     no satellite circuit
                                  in the connection
                                  0 1     one satellite circuit
                                  in the connection
                                  1 0     two satellite
                                  circuits in the connection
                                  1 1     spare

                                  Bits
                                  4 3     Continuity check
                                  ---     indicator
                                  0 0     continuity check not
                                  required
                                  0 1     continuity check
                                  required on this circuit
                                  1 0     continuity check
                                  performed on a previous
                                  circuit
                                  1 1     spare

                                  Bit
                                  5     Echo control device
                                  -     indicator
                                  0     outgoing echo control
                                  device not included
                                  1     outgoing echo control
                                  device included

                                  Bits
                                  8 7 6     Spare
                                  Ref.: ITU-T Q.763

   USI           9023   Octet     User Service Information
                        string    Ref.: ITU-T Q.763 Clause 3.57

C.10 AAL5 properties

PropertyID Property Type Value tag FMSDU A001 32-bit Forward Maximum CPCS-SDU Size: integer Maximum CPCS-SDU size sent in the direction from the calling user to the called user. Ref.: ITU-T Q.2931
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   BMSDU      A002        32-bit     Backwards Maximum CPCS-SDU Size:
                          integer    Maximum CPCS-SDU size sent in the
                                     direction from the called user to
                                     the calling user.
                                     Ref.: ITU-T Q.2931

   SSCS       See table   See table  See table in C.7
              in C.7      in C.7     Additional values:
                                     VPI/VCI

C.11 SDP equivalents

PropertyID Property Type Value tag SDP_V B001 String Protocol Version Ref.: RFC 2327 SDP_O B002 String Owner/creator and session ID Ref.: RFC 2327 SDP_S B003 String Session name Ref.: RFC 2327 SDP_I B004 String Session identifier Ref.: RFC 2327 SDP_U B005 String URI of descriptor Ref.: RFC 2327 SDC_E B006 String email address Ref.: RFC 2327 SDP_P B007 String phone number Ref.: RFC 2327 SDP_C B008 String Connection information Ref.: RFC 2327 SDP_B B009 String Bandwidth Information Ref.: RFC 2327 SDP_Z B00A String Time zone adjustment Ref.: RFC 2327 SDP_K B00B String Encryption Key Ref.: RFC 2327
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   SDP_A      B00C        String Zero or more session attributes
                                  Ref.: RFC 2327

   SDP_T      B00D        String Active Session Time
                                  Ref.: RFC 2327

   SDP_R      B00E        String Zero or more repeat times
                                  Reference: RFC 2327

   SDP_M      B00F        String Media type, port, transport and format
                                  Ref.: RFC 2327

C.12 H.245

PropertyID Property Type Value tag OLC C001 Octet The value of H.245 OpenLogicalChannel structure. string Ref.: ITU-T H.245 OLCack C002 Octet The value of H.245 string OpenLogicalChannelAck structure. Ref.: ITU-T H.245 OLCcnf C003 Octet The value of H.245 string OpenLogicalChannelConfirm structure. Ref.: ITU-T H.245 OLCrej C004 Octet The value of H.245 string OpenLogicalChannelReject structure. Ref.: ITU-T H.245 CLC C005 Octet The value of H.245 string CloseLogicalChannel structure. Ref.: ITU-T H.245 CLCack C006 Octet The value of H.245 string CloseLogicalChannelAck structure. Ref.: ITU-T H.245
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ANNEX D - Transport over IP

D.1 Transport over IP/UDP using Application Level Framing (ALF)

Protocol messages defined in this RFC may be transmitted over UDP. When no port is provided by the peer (see 7.2.8), commands should be sent to the default port number: 2944 for text-encoded operation, or 2945 for binary-encoded operation. Responses must be sent to the address and port from which the corresponding commands were sent. ALF is a set of techniques that allows an application, as opposed to a stack, to affect how messages are sent to the other side. A typical ALF technique is to allow an application to change the order of messages sent when there is a queue after it has queued them. There is no formal specification for ALF. The procedures in Annex D.1 contain a minimum suggested set of ALF behaviours Implementors using IP/UDP with ALF should be aware of the restrictions of the MTU on the maximum message size.

D.1.1 Providing At-Most-Once functionality

Messages, being carried over UDP, may be subject to losses. In the absence of a timely response, commands are repeated. Most commands are not idempotent. The state of the MG would become unpredictable if, for example, Add commands were executed several times. The transmission procedures shall thus provide an "At-Most-Once" functionality. Peer protocol entities are expected to keep in memory a list of the responses that they sent to recent transactions and a list of the transactions that are currently outstanding. The transaction identifier of each incoming message is compared to the transaction identifiers of the recent responses sent to the same MId. If a match is found, the entity does not execute the transaction, but simply repeats the response. If no match is found, the message will be compared to the list of currently outstanding transactions. If a match is found in that list, indicating a duplicate transaction, the entity does not execute the transaction (see D.1.4 for procedures on sending TransactionPending). The procedure uses a long timer value, noted LONG-TIMER in the following. The timer should be set larger than the maximum duration of a transaction, which should take into account the maximum number
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   of repetitions, the maximum value of the repetition timer and the
   maximum propagation delay of a packet in the network.  A suggested
   value is 30 seconds.

   The copy of the responses may be destroyed either LONG-TIMER seconds
   after the response is issued, or when the entity receives a
   confirmation that the response has been received, through the
   "Response Acknowledgement parameter".  For transactions that are
   acknowledged through this parameter, the entity shall keep a copy of
   the transaction-id for LONG-TIMER seconds after the response is
   issued, in order to detect and ignore duplicate copies of the
   transaction request that could be produced by the network.

D.1.2 Transaction identifiers and three-way handshake

D.1.2.1 Transaction identifiers
Transaction identifiers are 32-bit integer numbers. A Media Gateway Controller may decide to use a specific number space for each of the MGs that they manage, or to use the same number space for all MGs that belong to some arbitrary group. MGCs may decide to share the load of managing a large MG between several independent processes. These processes will share the same transaction number space. There are multiple possible implementations of this sharing, such as having a centralized allocation of transaction identifiers, or pre-allocating non-overlapping ranges of identifiers to different processes. The implementations shall guarantee that unique transaction identifiers are allocated to all transactions that originate from a logical MGC (identical mId). MGs can simply detect duplicate transactions by looking at the transaction identifier and mId only.
D.1.2.2 Three-way handshake
The TransactionResponse Acknowledgement parameter can be found in any message. It carries a set of "confirmed transaction-id ranges". Entities may choose to delete the copies of the responses to transactions whose id is included in "confirmed transaction-id ranges" received in the transaction response messages. They should silently discard further commands when the transaction-id falls within these ranges. The "confirmed transaction-id ranges" values shall not be used if more than LONG-TIMER seconds have elapsed since the MG issued its last response to that MGC, or when a MG resumes operation. In this situation, transactions should be accepted and processed, without any test on the transaction-id.
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   Messages that carry the "Transaction Response Acknowledgement"
   parameter may be transmitted in any order.  The entity shall retain
   the "confirmed transaction-id ranges" received for LONG-TIMER
   seconds.

   In the binary encoding, if only the firstAck is present in a response
   acknowledgement (see A.2), only one transaction is acknowledged.  If
   both firstAck and lastAck are present, then the range of transactions
   from firstAck to lastAck is acknowledged.  In the text encoding, a
   horizontal dash is used to indicate a range of transactions being
   acknowledged (see B.2).

D.1.3 Computing retransmission timers

It is the responsibility of the requesting entity to provide suitable timeouts for all outstanding transactions, and to retry transactions when timeouts have been exceeded. Furthermore, when repeated transactions fail to be acknowledged, it is the responsibility of the requesting entity to seek redundant services and/or clear existing or pending connections. The specification purposely avoids specifying any value for the retransmission timers. These values are typically network dependent. The retransmission timers should normally estimate the timer value by measuring the time spent between the sending of a command and the return of a response. Implementations SHALL ensure that the algorithm used to calculate retransmission timing performs an exponentially increasing backoff of the retransmission timeout for each retransmission or repetition after the first one. NOTE - One possibility is to use the algorithm implemented in TCP-IP, which uses two variables: - The average acknowledgement delay (AAD), estimated through an exponentially smoothed average of the observed delays. - The average deviation (ADEV), estimated through an exponentially smoothed average of the absolute value of the difference between the observed delay and the current average. The retransmission timer, in TCP, is set to the sum of the average delay plus N times the average deviation. The maximum value of the timer should however be bounded for the protocol defined in this RFC, in order to guarantee that no repeated packet would be received by the gateways after LONG-TIMER seconds. A suggested maximum value is 4 seconds.
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   After any retransmission, the entity SHOULD do the following:

   -  It should double the estimated value of the average delay, AAD.

   -  It should compute a random value, uniformly distributed between
      0.5 AAD and AAD.

   -  It should set the retransmission timer to the sum of that random
      value and N times the average deviation.

   This procedure has two effects.  Because it includes an exponentially
   increasing component, it will automatically slow down the stream of
   messages in case of congestion.  Because it includes a random
   component, it will break the potential synchronization between
   notifications triggered by the same external event.

D.1.4 Provisional responses

Executing some transactions may require a long time. Long execution times may interact with the timer-based retransmission procedure. This may result either in an inordinate number of retransmissions, or in timer values that become too long to be efficient. Entities that can predict that a transaction will require a long execution time may send a provisional response, "Transaction Pending". They SHOULD send this response if they receive a repetition of a transaction that is still being executed. Entities that receive a Transaction Pending shall switch to a different repetition timer for repeating requests. The root Termination has a property (ProvisionalResponseTimerValue), which can be set to the requested maximum number of milliseconds between receipt of a command and transmission of the TransactionPending response. Upon receipt of a final response following receipt of provisional responses, an immediate confirmation shall be sent, and normal repetition timers shall be used thereafter. An entity that sends a provisional response, SHALL include the immAckRequired field in the ensuing final response, indicating that an immediate confirmation is expected. Receipt of a Transaction Pending after receipt of a reply shall be ignored.

D.1.5 Repeating Requests, Responses and Acknowledgements

The protocol is organized as a set of transactions, each of which is composed of a request and a response, commonly referred to as an acknowledgement. The protocol messages, being carried over UDP, may be subject to losses. In the absence of a timely response, transactions are repeated. Entities are expected to keep in memory a
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   list of the responses that they sent to recent transactions, i.e., a
   list of all the responses they sent over the last LONG-TIMER seconds,
   and a list of the transactions that are currently being executed.

   The repetition mechanism is used to guard against three types of
   possible errors:

   -  transmission errors, when for example a packet is lost due to
      noise on a line or congestion in a queue;

   -  component failure, when for example an interface to a entity
      becomes unavailable;

   -  entity failure, when for example an entire entity becomes
      unavailable.

   The entities should be able to derive from the past history an
   estimate of the packet loss rate due to transmission errors.  In a
   properly configured system, this loss rate should be kept very low,
   typically less than 1%.  If a Media Gateway Controller or a Media
   Gateway has to repeat a message more than a few times, it is very
   legitimate to assume that something else than a transmission error is
   occurring.   For example, given a loss rate of 1%, the probability
   that five consecutive transmission attempts fail is 1 in 100 billion,
   an event that should occur less than once every 10 days for a Media
   Gateway Controller that processes 1000 transactions per second.
   (Indeed, the number of repetition that is considered excessive should
   be a function of the prevailing packet loss rate.)  We should note
   that the "suspicion threshold", which we will call "Max1", is
   normally lower than the "disconnection threshold", which should be
   set to a larger value.

   A classic retransmission algorithm would simply count the number of
   successive repetitions, and conclude that the association is broken
   after retransmitting the packet an excessive number of times
   (typically between 7 and 11 times.)  In order to account for the
   possibility of an undetected or in  progress "failover", we modify
   the classic algorithm so that if the Media Gateway receives a valid
   ServiceChange message announcing a failover, it will start
   transmitting outstanding commands to that new MGC.  Responses to
   commands are still transmitted to the source address of the command.

   In order to automatically adapt to network load, this RFC specifies
   exponentially increasing timers.  If the initial timer is set to 200
   milliseconds, the loss of a fifth retransmission will be detected
   after about 6 seconds.  This is probably an acceptable waiting delay
   to detect a failover.  The repetitions should continue after that
   delay not only in order to perhaps overcome a transient connectivity
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   problem, but also in order to allow some more time for the execution
   of a failover  (waiting a total delay of 30 seconds is probably
   acceptable).

   It is, however, important that the maximum delay of retransmissions
   be bounded.  Prior to any retransmission, it is checked that the time
   elapsed since the sending of the initial datagram is no greater than
   T-MAX.  If more than T-MAX time has elapsed, the MG concludes that
   the MGC has failed, and it begins its recovery process as described
   in section 11.5.  If the MG retries to connect to the current MGC it
   shall use a ServiceChange with ServiceChangeMethod set to
   Disconnected so that the new MGC will be aware that the MG lost one
   or more transactions.  The value T-MAX is related to the LONG-TIMER
   value: the LONG-TIMER value is obtained by adding to T  MAX the
   maximum propagation delay in the network.

D.2 Using TCP

Protocol messages as defined in this RFC may be transmitted over TCP. When no port is specified by the other side (see 7.2.8), the commands should be sent to the default port. The defined protocol has messages as the unit of transfer, while TCP is a stream-oriented protocol. TPKT, according to RFC 1006, SHALL be used to delineate messages within the TCP stream. In a transaction-oriented protocol, there are still ways for transaction requests or responses to be lost. As such, it is recommended that entities using TCP transport implement application level timers for each request and each response, similar to those specified for application level framing over UDP.

D.2.1 Providing the At-Most-Once functionality

Messages, being carried over TCP, are not subject to transport losses, but loss of a transaction request or its reply may nonetheless be noted in real implementations. In the absence of a timely response, commands are repeated. Most commands are not idempotent. The state of the MG would become unpredictable if, for example, Add commands were executed several times. To guard against such losses, it is recommended that entities follow the procedures in D.1.1.

D.2.2 Transaction identifiers and three-way handshake

For the same reasons, it is possible that transaction replies may be lost even with a reliable delivery protocol such as TCP. It is recommended that entities follow the procedures in D.1.2.2.
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D.2.3 Computing retransmission timers

With reliable delivery, the incidence of loss of a transaction request or reply is expected to be very low. Therefore, only simple timer mechanisms are required. Exponential back-off algorithms should not be necessary, although they could be employed where, as in an MGC, the code to do so is already required, since MGCs must implement ALF/UDP as well as TCP.

D.2.4 Provisional responses

As with UDP, executing some transactions may require a long time. Entities that can predict that a transaction will require a long execution time may send a provisional response, "Transaction Pending". They should send this response if they receive a repetition of a transaction that is still being executed. Entities that receive a Transaction Pending shall switch to a longer repetition timer for that transaction. Entities shall retain Transactions and replies until they are confirmed. The basic procedure of D.1.4 should be followed, but simple timer values should be sufficient. There is no need to send an immediate confirmation upon receipt of a final response.

D.2.5 Ordering of commands

TCP provides ordered delivery of transactions. No special procedures are required. It should be noted that ALF/UDP allows sending entity to modify its behaviour under congestion, and in particular, could reorder transactions when congestion is encountered. TCP could not achieve the same results.