User Controls
Posts by Enigma
-
2024-06-16 at 3:47 PM UTC in If it ain't one things it's a motherfuckin nother.He used to fuck his mother but now he fucks his brother.
I wrote this poem for my friend Instigaytor who is an incestuous man to his people. -
2024-06-16 at 3:43 PM UTC in Mole to meet youI can't think of more mole puns and I'm pretty sure you can't eiether.
-
2024-06-16 at 3:41 PM UTC in It’s my birthday!!!he also wanted the video of him when he was naked showing children his horseyhat in private videos to be removed from YouTube, the photos of it removed from everyone's computer and definitely not have 5 or 6 different people using it as their profile picture on the website.
He said "If you don't change your avatar I'm never talking to you again!!!"
ever again!!!
-
2024-06-16 at 3:34 PM UTC in Why are disabled people described as couragous?Folks someone tried to describe me as courageous the other day when I explained why I have to wear glasses and what happened to me like a year and a half ago.
COURAGEOUS NIGGA? All I did was not die and cling to life.
So I kinda dind't really take that to heart to be honest, but then this guy in a wheelchair and some guy with downsyndrome were giving Ted talks (I didn't watch) and they were described as 13 COURAGEOUS speakers. I don't understand? They're just defective people, what part of that involves courage? One guy had to be pushed onto stage because his power chair doesn't go up tall ramps unassisted? How is that brave?
So then I saw this fat person in a swimming suit trying to look sexy (They didn't (to me, I'm sure other people are into that) ) and people were like "Girl you're soooo brave."
:/
Like I don't get where this brave, courageous, etc is such an applied adjective to people being overweight, people being mentally and physically retarded and irking by on the pity of those around them, or not wanting to die when injured. How the fuck does that make anyone courageous?
discuss. Maybe I just don't understand it like I need to. -
2024-06-16 at 3:25 PM UTC in NEOM and The Line are going to be hilariousWHy did it have to be a line? Was there any benefit to making it a line instead of like a triangle or a circle?
-
2024-06-16 at 2:44 PM UTC in 🍬🍬Candy~Land🍬🍬tryna get booed up after u get booed down hmu
-
2024-06-16 at 2:44 PM UTC in 🍬🍬Candy~Land🍬🍬I'm trying to sleep with a black girl candy, what u on
-
2024-06-16 at 2:43 PM UTC in Breaking news: it’s 4/20did u and Lanny break up? I"m tryna stretch sumthin
-
2024-06-16 at 2:12 PM UTC in 🍬🍬Candy~Land🍬🍬
Originally posted by the man who put it in my hood V.34 Fax Relay over Packet Networks
December 2011
WHITE PAPER
Table of Contents
Scope 3
Standard Abbreviations 3
Overview 3
Phase E – Call release 7
V.34 Fax Relay Stimulus Signals 7
Calling Fax Tone (CNG) 7
V.8 Answer Tone (ANSam) 7
CNG and Answer Tone 7
V.8 CM 8
V.21 Preamble Flags 8
V.34 Fax Relay in Fallback Mode 8
V.34 Fax Relay per T.38 Version 3 9
T.38 Call Setup 10
Why Choose AudioCodes? 11
References 12
V.34 Fax Relay over Packet Networks
WHITE PAPER
2
Scope
This white paper provides a technical overview of V.34 fax technology and is intended for Fax over IP (FoIP)
application and test engineers, FoIP gateway vendors and customers, and FoIP customer support. A brief
introduction in V.34 fax relay technology is given with reviewing fax signals exchanged during different phases
of V.34 fax call, stimulus signals for transitioning gateways to V.34 fax relay, different methods of V.34 fax
communication over the Internet, and optimal methods of T.38 call establishment.
Standard Abbreviations
ANSam V.8 Answer tone, 2100 Hz, amplitude‐modulated
CI V.8 Call Indicator signal
CJ V.8 CM terminator
CM V.8 Call Menu signal
JM V.8 Joint Menu signal
CFR T.30 Confirmation to Receive
CNG T.30 Calling fax tone
CSI T.30 Called Subscriber Identification
DCN T.30 Disconnect
DCS T.30 Digital Command Signal
DIS T.30 Digital Identification Signal
EOP T.30 End of Page
ECM T.30 Error‐Correction Mode
HDLC High‐level Data Link Control
MCF T.30 Message Confirmation
PPS T.30 Partial Page Signal
SDP Session Description Protocol
SIP Session Initiation Protocol
TCF T.30 Training Check Frame
TSI T.30 Transmitting Subscriber Identification
Overview
The late 1990s and early 2000s were remarkable for the appearance and widespread proliferation of high‐
speed faxes based on the V.34 half‐duplex modulation system. Faxes featuring V.34 modulation capability are
also known as “super G3” faxes. Relative to regular G3 faxes, V.34 faxes significantly reduce the total time of
fax image transfer over PSTN. The time saving is achieved thanks to the following V.34 advantages:
• Fax image transfer at higher data rates of up to 33600 bps vs. the regular G3 maximum fax rate of
14400 bps
• Estimation of optimal symbol rate, data signaling rate and other modulation parameters while
avoiding using T.30 TCF
• Capability of fast renegotiation of the data signaling rate without restarting T.30 Phase B
• Fast T.30 control at 1200 bps full‐duplex vs. 300 bps half‐duplex V.21 of regular G3 faxes
The T.38 Recommendation initially published in 1998 defined the regular T.30 fax relay over IP (FoIP). Due to
high complexity of V.34 modulation, and due to the T.30 incompatibility of V.34 fax relative to regular fax
communication, for several years the T.38 had no support of V.34 fax relay; and the first three versions of T.38
– namely, version 0 (dated 1998), version 1 (dated 2000), and version 2 (dated 2002) – were based on regular
fax modulation schemes.
Two alternative methods of transferring V.34 fax calls over packet networks were used and continue to be
used today:
V.34 Fax Relay over Packet Networks
• Voice‐Band Data (VBD) fax transfer per V.151.1 and V.152
WHITE PAPER
• V.34 fax fallback to regular G3 fax relay at data rates of up to 14400 bps (V.17 modulation)
In VBD mode, all V.34 fax signals are transferred using a low distortion compression, for example, PCM A‐/‐μ
laws. The VBD method is attractive because it is least complex compared to FoIP and it allows a native V.34
operation at fax rates of up to 33600 bps. But VBD transfer may be problematic because:
3
• The VBD stream cannot be used by fax servers, internet‐aware faxes, and other fax relay oriented
applications
• Broad bandwidth consumption even without redundancy (≈64 kbps, full‐duplex)
• Low immunity to packet loss
• Low tolerance to network jitter and constant delay
• Low tolerance to sampling rate difference (or clock offset) between originate and answer side
gateways
• High sensitivity to imperfections of echo canceling
In order to allow FoIP communication between V.34 fax terminals by using T.38 of version 0, version 1 or
version 2, a FoIP gateway may need to force the V.34 fax terminals to operate in a fallback mode limited by
V.17 modulation at data signaling rates (fax rates) of up to 14,400 bps. Gateways may use different methods
to force a V.34‐to‐V.17 fallback which result in establishing a T.38 session based on regular (non‐V.34)
modulation at both sides of communication.
A growing usage of V.34 fax terminals required adequate signal processing by FoIP gateways and an adaptation
of the FoIP protocol. Accordingly, version 3 of the T.38 (dated 2007) defines an extended FoIP protocol of V.34
fax communication over IP at fax rates of up to 33,600 bps.
The following sections summarize important T.30 definitions for full V.34 fax relay and V.34 fax relay in fallback
mode.
V.34 Fax Call over the PSTN
A V.34 fax call may be divided into the following phases (according to ITU‐T recommendations T.30 from
09/2005 and V.34 from 02/98):
• Phase A – V.34 Call Establishment
• V.34 Phase 2 – Line probing
• V.34 Phase 3 – Primary channel equalizer training
• Phase B – Pre‐message procedures
• Phase C – In‐message procedure
• Phase D – Post‐message procedure
• Phase E – Call release
Figure 1 and Figure 2 show an example of a single fax call (Phase A through to D).
T.30 Phase A – V.34 Call Establishment
Figure 1 shows a typical signal flow corresponding to T.30 Phase A of V.34 call establishment.
Phase A starts with a tonal exchange between calling and answering fax terminals. It includes V.34 Phase 1
beginning with an ANSam tone. During V.34 Phase 1, the fax terminals exchange V.8 CM and JM messages to
define the fax call type. If the answering fax does not confirm having V.34 fax capability, then when the V.8
signal exchange is complete, the fax terminals enter regular T.30 Phase B. If the answering fax confirms V.34
capability, the terminals enter proper V.34 fax procedures, shown in Figure 2.
Generally, a more complex scenario is possible when an answering fax terminal uses regular T.30 Phase B for
transmission of T.30 capabilities (DIS) before it enters normal V.34 operation. In this case, the calling fax may
transmit the V.8 CI signal to initiate V.34 Phase 1.
V.34 Fax Relay over Packet Networks
WHITE PAPER
4
Figure 1: T.30 Phase A – V.34 Call Establishment
V.34 Phase 2 – Line Probing
Entering V.34 Phase 2, fax terminals send full‐duplex INFO0c and INFO0a signals at 600 bps to exchange the
supported symbol rates and other V.34 capabilities. After a successful exchange by INFO0 sequences, the
originating fax modem transmits line probing signals. The answering fax modem receiving the line probing
signals analyzes the channel characteristics and selects the optimal symbol rate, carrier frequency, pre‐
emphasis enhancement, and power reduction to be used during V.34 Phase 3 and later for every fax page of T.30 Phase
C. The selected parameters and requested V.34 TRN duration are forwarded to the originating fax by INFOh
sequence. After successfully transferring INFOh, the originating and answering modems enter V.34 Phase 3.
V.34 Phase 3 – Primary Channel Equalizer Training
In this phase, the originating fax modem sends a half‐duplex TRN signal. An answering fax modem receiving
the TRN trains the primary channel equalizer and precoder coefficients and adapts the other demodulation
parameters. When TRN duration expires, the fax modems launch a V.34 control channel (1200 bps, full‐duplex)
and exchange modulation parameter sequences: The MPh0 sequence of the originating modem and the MPh1
sequence of the answering modem. The MPh modulation parameters contain a maximum data signaling rate
and other options offered by the V.34 modem. The MPh1 sequence sent by the answering fax additionally
includes the precoder coefficients which should be used by the primary channel transmitter of the originating
fax.
After a successful exchange of modulation parameters, the fax terminals continue the full‐duplex operation of
the control channel and enter T.30 Phase B with transmission of HDLC flags.
V.34 Fax Relay over Packet Networks
WHITE PAPER
5
Figure 2: V.34 Fax Procedures
Phase B – Pre‐Message Procedures
After Phase B, all pre‐ and post‐message commands and responses of T.30 control are exchanged using the
V.34 control channel. The content of T.30 frames exchanged using the V.34 control channel is similar to that of
a regular G3 fax session. But the process is much faster relative to regular T.30 control exchange by V.21,
because
• The V.34 control channel bit rate is 4 times faster
• HDLC preamble of duration 1.0±0.15 sec is not required. According to T.30, at least two HDLC
flags (13.3 msec) are enough to send before the first HDLC frame.
The V.34 fax modulation system does not use TCF defined by T.30 for Phase B of regular G3 fax. In Phase B (see
Figure 2), an answering V.34 fax sends T.30 capabilities [CSI/] DIS to the originating fax and waits for a DCS
command. On receipt of the DIS from the answering fax, the originating V.34 fax sends a [TSI/] DCS command
and waits for CFR confirmation. On receipt of the DCS from the originating fax, the answering fax responds
with a CFR. The originating fax, on receipt of the CFR, starts a normal turn‐off procedure of the control channel
after which both faxes enter T.30 Phase C of fax image transfer.
By analyzing the telephone line for maximum use of line bandwidth and estimating modulation parameters
required for optimum image transfer, the V.34 faxes substantially reduce a total duration of phases preceding
Phase C relative to regular G3 fax. The highest gain in transmission time preceding T.30 Phase C is achieved
when line conditions do not allow transferring a G3 fax at the maximum data rate. Where a regular G3 fax may
perform some attempts in Phase B to choose an appropriate data rate and modulation system (V.17, V.29, or
V.27), a V.34 fax is capable of entering the image transfer directly after a single attempt of line probing and
TRN.
Phase C – In‐Message Procedure
The binary data of fax image and Return‐to‐Control for Partial page (RCP) frames are sent using the half‐duplex
primary channel. T.30 Error‐Correction Mode (ECM) is mandatory for V.34 faxes.
V.34 Fax Relay over Packet Networks
WHITE PAPER
The primary channel signal is transmitted using a symbol rate, carrier frequency, pre‐emphasis enhancement, and
power reduction specified by INFOh from the answering fax. The data signaling rate is the maximum rate
enabled that is less than or equal to the data signaling rates specified in both modems’ MPh sequences. The
other modulation parameters of primary channel (types of trellis and non‐linear encoders, constellation
6
shaping, and precoder enhancement coefficients) are applied according to the values specified by MPh1 of the
answering fax modem.
After transmission of the fax image and RCP, the originating fax turns off the half‐duplex primary channel and
enters T.30 Phase D.
Phase D – Post‐Message Procedure
In Phase D, the communicating modems resynchronize the V.34 control channel. Also, instead of
resynchronization of the control channel, a fax modem may initiate a control channel start‐up followed by
modulation parameters MPh exchange. This is useful when a change of MPh is required. For example, an
answering fax that received a fax image of Phase C as non‐satisfactory, may request a reduction of the data
signaling rate. In contrast to regular G3 fax procedures, renegotiation of the data rate is extremely fast and
does not require retraining the image type modulation system.
After resynchronization of V.34 control channel or control channel start‐up with MPh renegotiation, the
modems are ready to exchange a T.30 post‐message command of the originating fax, for example, PPS‐EOP,
and post‐message response of the answering fax. If a final partial page is positively confirmed by MCF of the
answering fax, the originating fax sends a DCN (see Figure 2).
On completion of Phase D, fax terminals execute a normal turn‐off procedure of the control channel. If the fax
image transfer is not completed, or a retransmission is required, then the fax terminals return to Phase C. In
case of DCN exchanged, the fax modems terminate the fax session via T.30 Phase E.
Phase E – Call release
Fax terminals physically disconnect. Under certain conditions, call release may be irregular, for example,
before completion of image transfer.
V.34 Fax Relay Stimulus Signals
Calling Fax Tone (CNG)
A calling fax tone (CNG) is common to regular G3 and V.34 fax calls. Generally, the CNG stimulus tone provides
transitioning to fax relay with highest reliability because gateways may switch a voice‐over‐IP (VoIP) operation
mode onto a fax relay during a silence period of CNG. Sometimes, however, fax relay initiated by a CNG tone
may be undesirable, for example, if:
• Call progress and/or speech signals exist during CNG
• Called terminal equipment is a regular telephone and not a fax
According to V.150.1, the CNG alone is not enough to indicate that a call is a facsimile and in some cases, the
originating fax may not transmit it.
V.8 Answer Tone (ANSam)
As stimulus signals, a called fax tone CED and a V.8 answer tone ANSam allow safe transitioning of gateways
from VoIP or VBD to fax relay state. To avoid answer tone irregularities caused by the gateway switching from
VoIP to a non‐VoIP state, ITU‐T V.150.1 recommends blocking the answer tone sent from the answering
equipment in the direction of the network, while the gateway determines answer tone type.
As the ANSam signal is common to V.34 fax and modem terminals, using only ANSam as a stimulus of V.34 fax
relay may be problematic for modem transport over packet networks, though in environments without
modems or in fax server gateways, the ANSam may be a recommended stimulus signal for transitions to V.34
fax relay.
V.34 Fax Relay over Packet Networks
WHITE PAPER
CNG and Answer Tone
AudioCodes gateways performing bi‐directional monitoring of fax signals use the following signal combinations
as stimuli for safest transitioning to fax relay:
7
• A CNG detected from the network and an answer tone received from TDM input
• A CNG received from TDM input and an answer tone detected from the network
Out‐of‐band signaling may be applied as an alternative to monitoring the signals decoded from the network
stream.
V.8 CM
A V.8 call menu (CM) sent by a calling fax terminal in response to an ANSam received from an answering fax
terminal is definitely a good signal for discriminating V.34 fax calls. But for fax relay call setup, the V.8 CM may
be less safe compared to CNG and/or ANSam because transition to fax relay state occurs in the middle of the
answer tone and may cause tone irregularities. AudioCodes gateways use the V.8 CM stimulus signal if they’re
not switched to fax relay at earlier stages.
V.21 Preamble Flags
The V.21 preamble of HDLC flags is common to regular G3 fax and manual V.34 fax calls. It is a good signal for
fax call discrimination and is considered a mandatory stimulus for transitioning to fax relay. Sometimes,
though, a switch to fax relay ‐ initiated by V.21 preamble flags ‐ may be problematic due to:
• Irregularities in the V.21 signal caused by the switch
• Prolonged gateway negotiation at stage of T.38 call setup, possibly resulting in loss or irregular
delay of T.30 data
AudioCodes gateways use the V.21 preamble as a final stimulus signal if they’re not switched to fax relay at
earlier stages.
V.34 Fax Relay in Fallback Mode
When a V.34 capable fax terminal (super G3) communicates with a regular G3 fax, the fax call is always regular
G3:
• A calling V.34 fax terminal cannot start in V.34 Phase 1 because the answering G3 fax terminal
cannot transmit an ANSam
• An answering V.34 fax enters regular Phase B after an ANSam because the calling G3 fax terminal
cannot transmit a V.8 CM.
For such calls, independently of T.38 version capabilities of communicating gateways, the corresponding fax
relay session will be regular G3 fax relay performed at fax data rates up to 14400 bps of V.17. The only non‐
regular T.38 packet v8‐ansam may appear at the beginning of fax relay session if both gateways support T.38
version 3.
A more complex scenario takes place when V.34 fax terminals connect through gateways not supporting V.34
fax procedures. For example, if ANSam and V.8 CM signals are transferred in VoIP or VBD mode, then gateways
waiting for the V.21 preamble may miss the possibility of entering fax relay because V.34 faxes do not use
HDLC protocol during automatic V.8 negotiation.
To resolve this problem, according to T.38 Recommendation, gateways not supporting T.38 version 3 must
prevent transferring the fax CM over VoIP or VBD to the answering fax terminals, and avoid V.8 capability to be
relayed in V.21 DIS frame to calling fax terminals.
Some gateways may support T.38 version 3 or higher but not be capable to V.34 modulation system, for
example, gateways may use high versions of T.38 to allow obsolete V.33 modulation (14400/12000 bps)
or/and new methods of T.38 call establishment. Such gateways, alternatively to blocking V.8 interaction, may
allow T.38 v8‐cm‐message/v8‐jm‐message packet exchange, but prevent the relaying V.34 modulation
capability.
V.34 Fax Relay over Packet Networks
WHITE PAPER
After avoiding or resolving the V.8 negotiation problem, the gateways may continue regular fax relay which
forces V.34 fax terminals to operate in non‐V.34 mode at fax data rates of up to 14400 bps of V.17.
8
V.34 Fax Relay per T.38 Version 3
The following Figure 3 is a schematic block‐diagram illustration of a FoIP communication system. System may
include, on one communication side, a calling or answering V.34 fax terminal connected to a switched
network, and may further include, on another communication side, an IP network connected to a remote
gateway or an IP fax device. A FoIP gateway may be connected between the switched network and the IP
network. The remote FoIP capable gateway, in turn, may be connected to a fax terminal, which may be an
answering or calling fax terminal.
Figure 3: Typical layout of V.34 FoIP communication
A FoIP gateway may receive analog signals from a facsimile terminal, for example the V.34 fax terminal,
through the switched network. The FoIP gateway may demodulate or convert the analog fax transmission to a
fax data set, may encode and packetize the fax data set according to the T.38 FoIP protocol, and may relay the
fax packets over the IP network to the remote gateway or to an Internet‐aware fax device, e.g., the IP fax.
Independently of whether a V.34 fax relay call is initiated during automatic or manual T.30 call establishment
procedures, the local and remote gateways must finally pass V.34 Phase 1 of V.8 ANSam/CM/JM interaction to
enter the main V.34 fax signal processing. A V.34 FoIP gateway receiving a V.34 CM signal from a connected
V.34 call fax may send a T.38 v8‐cm‐message packet carrying a T.38 Facsimile Application Profile (FAP). As a
response on the v8‐cm‐ -
2024-06-16 at 2:09 PM UTC in I went from being lonely a couple months ago to having 6 people I want to fuck wanting to fuck me too.
-
2024-06-16 at 2:04 PM UTC in 🍬🍬Candy~Land🍬🍬
-
2024-06-16 at 2:02 PM UTC in What are you listening to right now, space nigga?narc none of your videos show up for people in Americ ironically the land of the free
-
2024-06-16 at 2 PM UTC in O AMERICAThey don't teach us that gay one
-
2024-06-16 at 1:56 PM UTC in Earth is warming at a record rate, with 92% of last year's heat caused by humansIt's like 88 degrees out today!~!~!~!~
-
2024-06-16 at 1:48 PM UTC in Chess UsernameChessus Christ
-
2024-06-16 at 1:25 PM UTC in the average number of skeletons inside a human body is >1
ON paper they are 2 people witha bout 1.3 skeletons between them -
2024-06-16 at 1:15 PM UTC in When I was about 10 or 11 and setting up my first Hotmail accountMy primary email contains my first name, first initial and then 96
(Kinda a prelude to BradleyB93). I chose 87 because I made the email in 2005 so I wanted to appear to be 18 lol -
2024-06-16 at 1:15 PM UTC in When I was about 10 or 11 and setting up my first Hotmail accountMy friend growing up used the email ColdPlaya6969@hotmail.com from when his dumbass made the email at age 12 to senior year of highs school.
Bruh I remember being in the office with him and him having to give the school lady his email and he's telling her "ColdPlaya, yeah like player but with an a, 6 9 6 9 @hotmail. yeah that's my email." And just feeling embarrassed on his behalf. -
2024-06-16 at 5:48 AM UTC in Chess UsernameMolechesster
-
2024-06-16 at 5:46 AM UTC in It’s my birthday!!!Happy birthday crispy!!!
