ITU - Telecommunication Standardization Sector
Working Document 4
(Q.14/16)
STUDY GROUP 16
Geneva, 13-17 November 2000
Question: Q.fax/16
SOURCE* :
TITLE:
Q.fax/SG16 Ifax Ad-Hoc
DRAFT AMENDMENT TO RECOMMENDATION T.38 TO SUPPORT THE USE OF V.34
MODULATION
ABSTRACT
This contribution proposes a draft Amendment to Recommendation T.38 that will allow Group 3
facsimile terminals implemented with V.34 half-duplex modulation capability, as specified in Rec.
T.30, to transfer facsimile documents in real-time between two standard Group 3 facsimile
terminals over the Internet or over other networks using IP protocols.
28.07.17
-2-
1. Introduction
This contribution proposes a draft Amendment to Recommendation T.38 that will allow Group 3
facsimile terminals implemented with V.34 half-duplex modulation capability, as specified in Rec.
T.30, to transfer facsimile documents in real-time between two standard Group 3 facsimile
terminals over the Internet or over other networks using IP protocols. This may be accomplished by
amending Sections 2, 3, 4, 2.3.2, 2.3.3, Annex A and Annex B of Rec. T.38 using the following
text. A new T.38 Section 10 and Appendix II are also provided.
Support for V.34 fax using full-duplex modulation is for further study.
2
Amendments to Rec. T.38
2.1
Amendments to Section 2 Normative references
Add the following references to Section 2
–
ITU-T Recommendation V.8 (1998), Procedures for starting sessions of data transmission
over the general switched telephone network.
–
ITU-T Recommendation V.34 (1996), A modem operating at data signalling rates of
up to 33 600 bit/s for use on the general switched telephone network and on leased
point-to-point 2-wire telephone-type circuits
2.2
Amendments to Section 4 Abbreviatons
Amend Section 4 as follows:
This Recommendation uses the following abbreviations:
ANSam
V.8 amplitude-modulated ANSwer tone
CI
V.8 Call Indicator signal
CM
V.8 Call Menu signal
CJ
V.8 Call Menu terminator signal
ECM
Error Correction Mode
IAF
Internet Aware Fax device
IFP
Internet Facsimile Protocol
IFT
Internet Facsimile Transfer
INFOh
V.34 half duplex INFO sequence
IP
Internet Protocol
JM
V.8 Joint Menu signal
LSB
Least Significant Bit
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-3-
MPh
V.34 half duplex Modulation Parameter sequence
MSB
Most Significant Bit
TCP
Transmission Control Protocol
UDP
User Datagram Protocol
UDPTL
Facsimile UDP Transport Layer protocol
SUB
Subaddress
2.3
Amendments to Section 7.3.1 T30_ INDICATOR
Amend Table 3/T.38 as follows:
TABLE 3/T.38
Listing of T30_INDICATOR Values
Signal/Indication
No Signal
CNG (1100 Hz)
CED (2100 Hz)
V.21 Preamble
V.27 2400 modulation training
V.27 4800 modulation training
V.29 7200 modulation training
V.29 9600 modulation training
V.17 7200 modulation short training
V.17 7200 modulation long training
V.17 9600 modulation short training
V.17 9600 modulation long training
V.17 12 000 modulation short training
V.17 12 000 modulation long training
V.17 14 400 modulation short training
V.17 14 400 modulation long training
V.8 ANSam signal
V.8 signal
V.34 control channel
V.34 primary channel
V.34 control channel retrain
2.4
Amendments to Section 7.3.2 T30_DATA TYPE
Amend Section 7.3.2 as follows:
The T30_DATA TYPE is used to indicate that the packet contains data in the DATA element and
what modulation was used to carry the data. The T_30_DATA TYPE is used to indicate HDLC
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-4-
control data, Phase C data (T.4/T.6 or other) and, whenever V.34 modulation is used, the V.8
control signal data and V.34 control and primary channel data.
It has the following values:
TABLE 4/T.38
Listing of T30_DATAValues
Modulation
V.21 Channel 2
V.27ter 2400
V.27ter 4800
V.29 7200
V.29 9600
V.17 7200
V.17 9600
V.17 12 000
V.17 14 400
V.8
V.34 INFOh
V.34 MPh
V.34 Control Channel
V.34 Primary Channel
2.5
Amendments to Section 7.4 IFP Data Element
TABLE 5/T.38
Field-Type and Field-Data Description
Field Type
HDLC data
Field-Type Description
Data transmitted over the PSTN connection as HDLC. This includes the T.30
control messages as well as Phase C data sent using ECM.
The Field-Data that follows contains some, or all, of a single HDLC data frame
starting with the address frame of the HDLC frame, up to up to but not including
FCS. Bit stuffing is removed from all data. The end of a frame is indicated by the
FCS Indicator field. The gateway is responsible for bit stuffing, FCS generation,
and separating frames with one or more flag (0x7E) when sending the HDLC data
to a G3FE.
HDLC-Sig-End
Indicates that the HDLC power level has dropped below the turnoff threshold.
There is no Field-Data with this Field-Type. This field type can be used during
V.34 operation for terminating control channel at the end of a session.
HDLC-FCS-OK
Indicates the end of an HDLC frame and that the proper FCS was received. It also
indicates that this frame is not the final frame. There is no Field-Data with this
Field-Type.
HDLC-FCS-Bad
Indicates the end of an HDLC frame and that the proper FCS was not received. It
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-5-
Field Type
Field-Type Description
also indicates that this frame is not the final frame. There is no Field-Data with this
Field-Type.
HDLC-FCS-OK-Sig-End
Indicates the end of an HDLC frame and that the proper FCS was received and
transmission should terminate. There is no Field-Data with this Field-Type.
HDLC-FCS-BAD-Sig-End
Indicates the end of an HDLC frame and that the proper FCS was not received and
transmission should terminate. It also indicates that this frame is the final frame.
There is no Field-Data with this Field-Type.
T.4-Non-ECM
T.4 Phase C data that is not sent using ECM or TCF data in the case of Method 2
of Rate Adaptation. It also indicates that this is not the end of the Phase C data.
The Field-Data that follow are the demodulated Phase C data, including fill bits
and RTC.
T.4-Non-ECM-Sig-End
T.4 phase C data that is not sent using ECM or TCF data in the case of Method 2
of Rate Adaptation. It also indicates that this is the end of the Phase C data.
The Field-Data that follow are the demodulated Phase C data, including fill bits
and RTC.
V.8-Data
Data transmitted in the V.8 signals CI, CM, JM and CJ
The Field-Data that follows contains some or all of the information bearing octets
of the CI, CM, JM and CJ signals with start and stop bits removed. It does not
include the sequence of ten ONEs , which are indicated by the initial
T30_Indicator(v.8 signal) or subsequent V.8 data packets with field-type of v8ten-ones.
V.34-INFOh-Data
Optional data transmitted in the INFOh signal.
The Field-Data that follows are the bits of the INFOh signal up to, but not
including the CRC, with padding bits to the nearest octet boundary. Only data with
a valid CRC may be forwarded.
V.34-MPh-Data
Data transmitted in the MPh signal.
The Field-Data that follows are the bits of the MPh or INFOh signal up to, but not
including the CRC, with padding bits to the nearest octet boundary. Only data with
a valid CRC may be forwarded.
2.6
Rename Section 8
8
IFP Message Flow for Facsimile Rates Up To V.17
2.7
New Section 10
Message Flow for V.8 Signals and Annex F V.34 Facsimile
10.1
V.8 Negotiation
Certain modulations may be negotiated using Rec. V.8 signals, e.g. V.34. During this negotiation
procedure the ANSam, CI, CM, JM and CJ signals are interchanged between the calling and called
G3FEs. Gateway implementers may elect to modify the information octets as required to eliminate
the indication of capabilities that cannot be supported by that gateway.
ANSam shall be detected by the Receiving Gateway and generated by the Emitting Gateway. When
ANSam is detected by the Receiving Gateway, it shall be reported using the v8-ansam indicator if
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-6-
the Emitting Gateway is V.34 capable. If the Emitting Gateway is not V.34 capable, the Receiving
Gateway shall report ANSam using the ced indicator.
In the event that there is a timeout in response to an ANSam generated by the emitting gateway,
resulting in a V.21 response, either gateway may elect to prevent a possible return to V.8
negotiations by resetting the V.8 DIS bit.
A gateway that detects the initial sequence of ten ONES that precedes the first CM or JM sequence
shall be reported using a v8-signal indicator. Subsequent sequences of ten ONES shall be reported
within a t30-data packet using a v8-ten-ones field type. Refer to Figure 1 for an example.
All CI, CM, JM, and CJ information octets (not including the sequence of ten ONES) shall be
transferred with STOP and START bits removed in a t30-data packet using a v8-data field type.
Each v8-data packet may contain one or more information octets.
Gateways shall send a t30-data packet using a v8-sig-end field type when V.8 signalling has been
terminated by the G3FEs.
Upon completion of V.8 signalling, Emitting and Receiving gateways shall proceed with the
appropriate modulation specified by the JM information.
10.2 V.34 Data Rate Management
The two gateways should independently proceed with phase 2 and phase 3 of V.34 half-duplex
handshake as mentioned in [2]. The data rate shall be negotiated in the control channel startup or
control channel retrain of the V.34 half-duplex handshake. The intent of this process is to ensure
that the data rate between the gateways is determined before allowing the end points to complete
data rate negotiation. It is not necessary to constrain the equipment at both ends to the same symbol
rate. The control channel negotiation will select the fastest compatible data rate. The only possible
incompatibility can be avoided by disallowing a data rate of 2400 bit/sec.
10.2.1 V.34 Primary Channel Training
The INFOh signal shall be transmitted from the receiving gateway to emitting gateway. The
emitting gateway may be able to interpret INFOh signal and amend the TRN length parameter of
its INFOh, in order to balance the timings of phase 3 of V.34 half-duplex training.
10.2.2 MPh Based Data Rate Management
The data rate on the two PSTN links is controlled via the MPh signals that are exchanged between
the gateways. A Gateway shall:

Forward to the Remote Gateway a “combined MPh” when it receives an MPh from the local
G3FE

Refrain from sending an MPh to the local G3FE until it has received a “combined MPh“ from the
Remote Gateway
A “combined MPh” is MPh signal that indicates the maximum data rate that is less than or equal to
the data signalling rates specified by the local G3FE’s MPh sequence and the Gateway’s own data
signalling rate capability.
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-7-
MPh data shall be sent through the IP network by a gateway only if the MPh data has been received
in total AND the CRC has been confirmed. Once the MPh data with confirmed CRC has been
received, the gateway shall pass the MPh data up to but not including the CRC, as described in Table
5/T.38. The MPh packet is sent using v34-mph Data Value with a Field-Type of v34-mph-data.
The Remote Gateway shall extract from the “combined MPh” only the bit rate information for both
the primary channel and the control channel. It shall ignore the other bits in the “combined MPh”.
In the typical case (no polling), the Receiving Gateway shall delay generation of MPh until a valid
MPh signal is received from the Emitting Gateway. The Emitting Gateway shall forward a
“combined MPh“ to the Receiving Gateway that indicates the common bit rates supported by the
Calling G3FE and the Emitting Gateway. The Receiving Gateway then generates MPh for the
Receiving G3FE that indicates the common set of bit rates supported by the Calling G3FE, and both
gateways. The Receiving Gateway forwards the final MPh from the Receiving G3FE across the IP
network to force the primary channel data rate AND the control channel rate to be consistent in both
V.34 sessions.
A Gateway may need to use some method to occupy the local G3FE until the “combined MPh” is
received from the Remote Gateway. If a Gateway receives MPh sequence from local G3FE that is
different from the previously received MPh sequence from local G3FE, Gateway shall forward the
new “combined MPh” sequence to the Remote Gateway.
10.2.3 V.34 Control Channel Startup
Control Channel startup can occur after training of the Primary Channel or after sending data in the
Primary Channel (T.30 Phase C) if there is no request to change the Primary Channel data rate via a
Control Channel Resync.
Primary and control channel data rate management in the control channel negotiation shall be
handled according to section 10.2.2.
10.2.4 Control Channel Retrain
Control Channel retrain is signalled using the v34-CC-retrain indicator. A gateway shall initiate a
retrain sequence at an appropriate time in response to this indicator. The retrain sequence causes an
MPh exchange, resulting in a new bit rate.The typical use of Control Channel Retrain is to change
the Primary Channel data rate between pages or between partial pages. Either the sending G3FE or
the receiving G3FE can initiate a data rate change by sending PPh.
A Gateway that receives a PPh shall send a v34-CC-retrain indicator to the Remote Gateway. A
Gateway that receives a v34-CC-retrain indicator, generates AC to induce a Control Channel
Retrain. Primary and control channel data rate management during the control channel retrain shall
be handled according to section 10.2.2. Refer to Figures 5 through 8 for examples.
10.3
Facsimile Mode
10.3.1 Control Channel
Control Channel data exchange begins after the MPh exchange is complete and the parameters for
the Control Channel rate and the Primary Channel rate have been agreed. Since the MPh exchange
is known by both gateways, the proper Control Channel rate will be known by both gateways. This
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-8-
allows the use of a single Data value of v34-control-channel to be used for both 1200 bps and 2400
bps.
The Control Channel is a full duplex channel that, unlike the non-V.34 fax modes, sends FLAGS in
the absence of data (compared to silence for the non-V.34 modes). It is the responsibility of the
gateway or IAF to generate FLAGS as needed during control channel operations.
Control Channel packets are sent using v34-control-channel Data Value and Field-Types of hdlcxxx.
The hdlc-xxx-sig-end field types can be used to terminate control channel operation at the end of a
V.34 fax session.
10.3.2 Switch From Control Channel to Primary Channel
The source terminal indicates its intention to shut down the Control Channel and switch to the
Primary Channel by sending continuous ONEs of at least 40 in number and until it detects that the
recipient terminal has stopped sending flags.
This sequence will be supported locally between the G3FE and the Gateway or IAF. An Emitting
Gateway shall signal a Receiving Gateway that it is ready to transition to primary channel by
sending a v34-primary-channel Indicator.
10.3.3 Primary Channel
T.30 Annex F requires that all image data be sent using ECM. This means that Primary channel data
shall be sent in packets using v34-primary-channel Data Value and Field-Types of hdlc-xxx.
10.3.4 Switch From Primary Channel to Control Channel
The Emitting Gateway shall send the v34-control-channel indicator after the Primary Channel turnoff sequence is complete. Using the v34-control-channel indicator, the Receiving Gateway shall
initiate the turn-off of the Primary Channel between it and the Called G3FE.
If a change in the Primary Channel bit rate is not desired, the control channel starts up per 10.2.3. If
a change in Primary Channel bit rate is signalled, the v34-CC-retrain is used per 10.2.4.
10.3.5 Turn-around Polling Mode
Turn-around polling is accomplished by shutting down the Control Channel after a DTC command
and initiating a V.8 exchange with CM (ANSam is not used). The source terminal (Calling G3FE)
indicates its intention to do turn-around polling by sending DTC and sends FLAGs until continuous
ONEs are detected. After the ONEs are detected, it is quiet for 70 ms and then initiates CM. The
receiving terminal (Called G3FE) indicates its intention to shut down the Control Channel and
switch to V.8 signalling by sending continuous ONEs of at least 40 in number and until it detects
that the source terminal has stopped sending flags.
This turn-around polling sequence will be supported locally between the G3FEs and the Gateways.
A Receiving Gateway shall signal an Emitting Gateway that it wishes to transition to V.8
negotiations by sending a v8-signal indicator. It is up to the Receiving Gateway implementer to
determine at what point it sends the indicator.
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
-9-
When the Emitting Gateway detects the start of CM it shall send the v8-signal Indicator to the
Receiving Gateway. From that point, the procedures of section 10.1 shall be used.
10.3.6 Manual Entry into V.34 Annex F Operation
Manual entry into V.34 is accomplished by the Calling G3FE responding with CI to a DIS from the
Called G3FE with bit 6 set to 1. The Called G3FE responds to CI with ANSam, thus initiating the
normal V.8 sequence.
To support Manual Entry, the Emitting Gateway shall be capable of detecting CI after sending DIS
in non-V34 mode. The Emitting Gateway shall send a v8-signal followed by CI data as described
in section 10.1. The Receiving Gateway shall regenerate the CI signal for the Called G3FE.
10.3.7 Disconnect
At the end of a call, a Gateway shall indicate the end of the Control Channel with the hdlc-xxx-sigend or the no-sig indicator to the Remote Gateway.
10.4
Compatibility with Equipment Conforming to T.38 (1998)
A T.38 device conforming to earlier versions of the Recommendation (Versions 0,1) will not be
able to interpret some messages added to enable V.34 capability.
A non-V34(V.8) facsimile device will not recognize the amplitude modulation or phase reversals on
an ANSam signal and will treat the signal as if it were a CED. A T.38 device conforming to earlier
versions of this Recommendation will not be able to understand the T30_INDICATOR V.8
ANSam signal.
A T.38 device conforming to this version of Recommendation T.38 should only send signals
defined in previous versions of T.38 to another device conforming to previous versions of T.38. A
T.38 device detecting a T30_INDICATOR V.8 ANSam signal will map this signal into a
T30_INDICATOR CED signal before sending it to a T.38 device indicating version 0 or 1
capability. A T.38 gateway conforming to version 2 of the recommendation may not advertise V.8
capability or respond to V.8 handshake with an external facsimile device when interoperating with a
version 0 or 1 T.38device.
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 10 -
2.6
Amendments to Annex A
Amend Annex A as follows:
A.1
ASN.1 notation
T38 DEFINITIONS AUTOMATIC TAGS ::=
BEGIN
IFPPacket ::= SEQUENCE
{
type-of-msg
Type-of-msg,
data-field
Data-Field OPTIONAL
}
Type-of-msg ::= CHOICE
{
t30-indicator ENUMERATED
{
no-signal,
cng,
ced,
v21-preamble,
v27-2400-training,
v27-4800-training,
v29-7200-training,
v29-9600-training,
v17-7200-short-training,
v17-7200-long-training,
v17-9600-short-training,
v17-9600-long-training,
v17-12000-short-training,
v17-12000-long-training,
v17-14400-short-training,
v17-14400-long-training,
…,
v8-ansam,
v8-signal,
v34-control-channel,
v34-primary-channel,
v34-CC-retrain
},
data ENUMERATED
{
v21,
v27-2400,
v27-4800,
v29-7200,
v29-9600,
v17-7200,
v17-9600,
v17-12000,
v17-14400,
…,
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 11 -
v8,
v34-infoh,
v34-mph,
v34-control-channel,
v34-primary-channel
}
}
Data-Field ::= SEQUENCE OF SEQUENCE
{
field-type
ENUMERATED
{
hdlc-data,
hdlc-sig-end,
hdlc-fcs-OK,
hdlc-fcs-BAD,
hdlc-fcs-OK-sig-end,
hdlc-fcs-BAD-sig-end,
t4-non-ecm-data,
t4-non-ecm-sig-end,
…,
v8-ten-ones,
v8-data,
v8-sig-end,
v34-infoh-data,
v34-mph-data
},
field-data
OCTET STRING (SIZE(1..65535)) OPTIONAL
}
UDPTLPacket ::= SEQUENCE
{
seq-number
INTEGER (0..65535),
primary-ifp-packet
TYPE-IDENTIFIER.&Type(IFPPacket),
error-recovery CHOICE
{
secondary-ifp-packets SEQUENCE OF TYPE-IDENTIFIER.&Type(IFPPacket),
fec-info
SEQUENCE
{
fec-npackets INTEGER,
fec-data
SEQUENCE OF OCTET STRING
}
}
}
END
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 12 -
2.8 New Appendix II
APPENDIX II
V.34 Session Examples
II.1
V.34 Session Examples
This section contains several examples of signal flow in a V.34 half-duplex fax session
F1
G1
G2
F2
t30-indicator(v8-ansam)
A
N
S
am
A
N
S
am
t30-indicator(v8-signal)
t30-data(v8, octets)
t30-data(v8, v8-ten-ones)
t30-data(v8, octets)
CM
JM
CJ
t30-data(v8, v8-ten-ones)
t30-indicator(v8-signal)
t30-data(v8, octets)
t30-data(v8, octets)
t30-data(v8, v8-ten-ones)
t30-data(v8, v8-ten-ones)
t30-data(v8, octets)
t30-data(v8, octets)
t30-data(v8, v8-ten-ones)
t30-data(v8, v8-ten-ones)
t30-data(v8, octets)
t30-data(v8, octets)
t30-data(v8, octets(0))
t30-data(v8, v8-ten-ones)
t30-data(v8, v8-sig-end)
CM
JM
CJ
Figure 1 - V.8 signalling
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 13 -
F1
G1
G2
F2
FLAG
FLAG
FLAG
DIS
DCS
FLAG
FLAG
CFR
1's
FLAG
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
FLAG
DIS
FLAG
DCS
CFR
FLAG
FLAG
t30-indicator(v34-pri-channel)
1's
S
S
S*
S*
FLAG
FLAG
t30-data(PRI, octets)
DATA
t30-data(PRI, octets)
DATA
Figure 2 – Switching to primary channel
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 14 -
F1
G1
G2
F2
t30-data(PRI, octets)
DATA
DATA
t30-data(PRI, octets + EOF)
FLAG
t30-indicator(v8_ctl_channel)
Sh
Sh*
FLAG
Sh
Sh
Sh*
Sh*
ALT
Sh*
ALT
ALT
FLAG
PPS-NULL
ALT
FLAG
FLAG
FLAG
MCF
1's
Sh
FLAG
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
FLAG
PPSNULL
MCF
FLAG
FLAG
t30-indicator(v8-pri-channel)
1's
S
S
S*
S*
FLAG
FLAG
t30-data(PRI, octets)
DATA
DATA
t30-data(PRI, octets)
Figure 3 - Between partial pages
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 15 -
F1
G1
G2
F2
t30-data(PRI, octets)
DATA
DATA
t30-data(PRI, octets + EOF)
FLAG
t30-indicator(v8_ctl_channel)
Sh
Sh*
FLAG
Sh
Sh
Sh*
Sh*
ALT
Sh*
ALT
ALT
FLAG
PPS-EOP
FLAG
Sh
ALT
FLAG
FLAG
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
FLAG
PPS-EOP
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
MCF
MCF
FLAG
DCN
FLAG
t30-data(CTL, octets)
t30-data(CTL, octets + EOF)
FLAG
DCN
FLAG
1's
t30-data(CTL, sig-end)
FLAG
1's
Figure 4 - Last page
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 16 -
F2 Requests Data Rate Change
F1
G1
G2
F2
Primary
Channel
Data
t30-indicator(V 34-control-channel)
Primary
Channel
Data
Sh
/Sh
Sh
Sh
/Sh
/Sh
A LT
A LT
PPh
E
A LT
E
t30-indicator (V 34-CC-re tr ain)
Control
Channel
Data
Control
Channel
Data
PPh
A LT
Control
Channel
Data
t30-data(MPh, info)
t30-data(MPh, info)
Control
Channel
Data
Control
Channel
Data
MPh
Finish Control Channel Handshake
Finish Control Channel Handshake
MPh
PPh
Finish Control Channel Handshake
A LT
AC
Finish Control Channel Handshake
PPh
Control
Channel
Data
Figure 5 - Data rate change sequence when F2 initiates retraining
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 17 -
F1 Requests Data Rate Change
F1
G1
G2
Primary
Channel
Data
t30-indicator(V 34-control-channel)
F2
Primary
Channel
Data
t30-indicator (V 34-CC-re tr ain)
PPh
PPh
Sh
/Sh
A LT
A LT
Sh
E
/Sh
Control
Channel
Data
Finish Control Channel Handshake
AC
PPh
t30-data(MPh, info)
Control
Channel
Data
Finish Control Channel Handshake
Finish Control Channel Handshake
t30-data(MPh, info)
Control
Channel
Data
A LT
E
Control
Channel
Data
PPh
A LT
MPh
Finish Control
Channel
Handshake
Control
Channel
Data
MPh
Control
Channel
Data
Figure 6 - Data rate change sequence when F1 initiates retraining
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 18 -
G2 Requests Data Rate Change
F1
G1
G2
F2
Primary
Channel
Data
t30-indicator(V 34-control-channel)
Primary
Channel
Data
Sh
/Sh
t30-indicator (V 34-CC-re tr ain)
Sh
A LT
PPh
/Sh
PPh
A LT
E
E
Control
Channel
Data
A LT
PPh
Finish Control
Channel
Handshake
MPh
Control
Channel
Data
t30-data(MPh, info)
t30-data(MPh, info)
Control
Channel
Data
Control
Channel
Data
MPh
Finish Control Channel Handshake
AC
Finish Control Channel Handshake
PPh
A LT
Finish Control Channel Handshake
Control
Channel
Data
Control
Channel
Data
Figure 7 - Data rate change sequence when G2 initiates retraining
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17
- 19 -
G1 Requests Data Rate Change
F1
G1
G2
F2
Primary
Channel
Data
t30-indicator(V 34-control-channel)
Primary
Channel
Data
Sh
/Sh
t30-indicator (V 34-CC-re tr ain)
Sh
PPh
A LT
/Sh
A LT
Sh
E
PPh
/Sh
Control
Channel
Data
AC
PPh
t30-data(MPh, info)
t30-data(MPh, info)
Control
Channel
Data
Finish Control Channel Handshake
Finish Control Channel Handshake
MPh
Finish Control Channel Handshake
A LT
Control
Channel
Data
A LT
E
Control
Channel
Data
PPh
A LT
MPh
Finish Control
Channel
Handshake
Control
Channel
Data
Control
Channel
Data
Figure 8 - Data rate change sequence when G1 initiates retraining
ITU-T\SG_DOC\SG16\NOV00\PLEN\PL-049.DOC
28.07.17