Business-Class Router Solutions – All Telecommunication Services in One Access
4.7
VoIP Implementation in OneOs
www.oneaccess-net.com
contact@oneaccess-net.com
v0.11 2007
Copyright © OneAccess Networks – All rights reserved
VoIP – H.323

VoIP Typical Architecture
Media Gateway
PSTN
SS7/ISUP
H.323
Voice Gateway
ONE 400
ISDN S0/S2
IP
Softswitch
Gatekeeper
H.323
Voice Gateway
ONE 200
Copyright © OneAccess Networks – All rights reserved
ISDN S0 or FXS
2
VoIP - SIP

VoIP Typical Architecture
Media Gateway
PSTN
SIP
Voice Gateway
ONE 400
SS7/ISUP
IP
ISDN T0/T2
SIP
IP PHONE
Voice Gateway
ONE 100
Softswitch
Copyright © OneAccess Networks – All rights reserved
3
VoIP: Voice Processing

Voice processing: main features
 Echo cancellation
 Jitter compensation
 Voice coding
G.711 a-law or µ-law (64 kbps)
 G.729A (8 kbps, no silence suppression)
 G.726r32 ( 32 kbps )
 G.729AB (8 kbps, optional silence suppression)
 CES Clear Channel for unrestricted data (64 kbps transparent)




FAX/Modem processing
Data processing
Clock synchronization
Copyright © OneAccess Networks – All rights reserved
4
VoIP: Echo Cancellation

The echo must be cancelled on both sides to
preserve the Quality of the voice

Echo is due to a physical phenomenon:

The transmitted voice signal is reflected at the far-end of the
transmission line when a mismatch condition exits for :




Analog loop / hybrid 2-wires/4-wires (electrical signal reflection)
Acoustical feed-back (sound signal reflection)
On PSTN line, if the transmission delays are low (< 10ms), the
echo is not noticed by human ears
The echo becomes audible with VoIP because of various
processing steps introducing delay in voice transmission:

Packetization / compression / propagation / cells switching / queuing for
prioritization / buffering for jitter compensation / network transit delay
Copyright © OneAccess Networks – All rights reserved
5
VoIP: Echo Cancellation

Echo Cancellation
echo origin
from 2 to 3 ms
B
The echo coming from B
and heard by A must be
cancelled here
PBX
A
IP
T0 + 100
T0 + 100 + 6
T0
A
C
3 ms
T0 + 206 ms
Long echo result (com. from A to C) with 100ms transit delay
Copyright © OneAccess Networks – All rights reserved
6
VoIP: Echo Cancellation

The ONE CPE has three cancellation delays or (length)






low = 8 msec: used for phones directly connected to the PBX or the
ONE200/400
medium = 16 msec and high = 32 msec recommended if a PSTN is used for
the call
The Echo cancellation is automatically disabled when modem
transmission is detected
The Echo canceller includes a Non Linear Processor (NLP) to
suppress the residual echo. The NLP is disabled in case of
G3 FAX communication
The echo canceller automatically detects double-talk
situation to suspend the cancellation
The following standards apply:

ITU-T G.165 , G.168
Copyright © OneAccess Networks – All rights reserved
7
VoIP: Jitter Compensation

Important Jitter is generated if:


The long data packets are not fragmented when transmitted
over low speed lines
The priority for voice packets is not managed in the network
Data
Multiplexing jitter generation
Voice

The ONE200/400 compensates jitter by implementing a dejitter buffer
Buffer
Jitter compensation
Output clock
Copyright © OneAccess Networks – All rights reserved
8
VoIP: Voice Coding

Voice coding


Configurable coder list for capabilities negotiation
Configurable transmission periodicity


10, 20, 30, 40 ms for G.711, G.729A, G.729AB, CES
Support of asymmetric coding
Copyright © OneAccess Networks – All rights reserved
9
VoIP: Voice Coding

Voice Coding
 Used
bandwidth
Length
G.711/CES
G.726 32Kbps
G.729AB
Bandw ith requirem ent in bps
Period
Packet/s
Voice only
with IP
Ethernet
ATM
IP Only
10
100
80
120
126400
127200
96000
20
50
160
200
95200
106000
80000
30
33,33
240
280
84792
84792
74659
40
25
320
360
79600
84800
72000
10
100
40
80
94400
84800
64000
20
50
80
120
63200
63600
48000
30
33,33
120
160
52795
56528
42662
40
25
160
200
47600
53000
40000
10
100
10
50
70400
84800
40000
20
50
20
60
39200
42400
24000
30
33,33
30
70
28797
28264
18665
40
25
40
80
23600
21200
16000
Copyright © OneAccess Networks – All rights reserved
10
VoIP: FAX/Modem processing

Fax / Modem processing

Three types of devices are supported:





G3 FAX (up to V17 – 14400 bps)
Super G3 FAX (V34): processed as a Modem
Modem (up to V90)
The ONE200/400 detects the type of communication:
voice, G3 FAX, Modem/SG3 Fax , (analysis of the FAX
answer tone)
Requirements:


For Modem / SG3 FAX, the coder must be G.711 and the echo
canceller must be disabled , SG3toG3 facility is also available to
force the SG3 FAX in G3 mode
For G3 FAX: the Non Linear Processor is disabled. Transport in
G.711 coding mode or FAX Relay T38
Copyright © OneAccess Networks – All rights reserved
11
VoIP: FAX/Modem Processing

In-band processing




The coder used is G.711 Selected for all the calls or for
specific subscriber numbers only (routing table)
Echo canceller automatically disabled in case of Modem
NLP automatically disabled in case of G3 Fax
FAX / Modem passthrough




Direct switchover to G.711 coder upon fax and/or modem detection
(called side only). (oneway G729 to G711 fallback) or SIP re-invite
message or NSE RTP packets ( Cisco )
Echo canceller automatically disabled in case of Modem
NLP automatically disabled in case of G3 Fax
FAX Relay T38

V27 ter (4800 bps) and V29 (9600 bps)
T.30 messages analysis
Transparent transport for data (UDP) with optional redundancy

SG3toG3 fallback / allows to use same bandwidth for G3 and SG3 FAX


Copyright © OneAccess Networks – All rights reserved
12
Fax relay T38 debug

Fax T38 processing and traces: display of the T30
messages.
One_training>trace filter add vox up ifp 2 show
01:42:57.665 Info vox voip userplan 3 Fax T38 starting call-id: 29 .
01:43:04.825 VOX.up.ifp.2 ------ NSF / CSI / DIS ------>
01:43:07.717 VOX.up.ifp.2 <-------- TSI / DCS ---------01:43:07.837 VOX.up.ifp.2 <------- TCF (v29_9600) -------01:43:11.814 Info vox voip userplan 1 T38 Pre-message procedure OK, call-id: 29.
01:43:11.814 VOX.up.ifp.2 ------------ CFR ------------>
01:43:12.437 Info vox voip userplan 1 T38 Transmitting page 1, call-id: 29.
01:43:12.437 VOX.up.ifp.2 <------ PAGE (v29_9600) -------01:51:10.502 VOX.up.ifp.2 <--------- PPS-EOP ----------01:51:13.599 Info vox voip userplan 1 T38 page 1 OK, call-id: 29.
01:51:13.599 VOX.up.ifp.2 ------------ MCF ------------>
01:51:15.282 VOX.up.ifp.2 <----------- DCN ------------01:51:15.846 Info vox voip controlplan 3 Call Disconnection received on local port: 5/2,
cause: (16)[Normal call clearing], call-id: 29.
Copyright © OneAccess Networks – All rights reserved
13
Fax relay T38 debug

Fax T38 processing and traces: display of the T30
messages.
One_training>trace filter add vox up ifp 2 show
01:42:38.100 Info vox voip controlplan 3 Outgoing call on voip id: 0, calling: 110,
called: 111, call-id: 29.
01:42:40.397 Info vox voip controlplan 3 Alert in band received, call-id: 29.
01:42:40.917 Info vox voip userplan 3 VoIP RTP transmission started, coder: G729, call-id: 29.
01:42:40.997 Info vox voip userplan 3 VoIP RTP reception started, coder: G729, call-id: 29.
01:42:52.444 Info vox voip controlplan 3 Call connected, call-id: 29.
01:42:57.537 Info vox voip userplan 3 VoIP RTP transmission stopped, coder: G729, call-id: 29.
01:42:57.537 Info vox voip userplan 3 VoIP RTP reception stopped, coder: G729, call-id: 29.
01:42:57.665 Info vox voip userplan 3 Fax T38 starting call-id: 29 .
01:43:04.825 VOX.up.ifp.2 ------ NSF / CSI / DIS ------>
01:43:07.717 VOX.up.ifp.2 <-------- TSI / DCS ---------01:43:07.837 VOX.up.ifp.2 <------- TCF (v29_9600) -------01:43:11.814 Info vox voip userplan 1 T38 Pre-message procedure OK, call-id: 29.
01:43:11.814 VOX.up.ifp.2 ------------ CFR ------------>
01:43:12.437 Info vox voip userplan 1 T38 Transmitting page 1, call-id: 29.
01:43:12.437 VOX.up.ifp.2 <------ PAGE (v29_9600) -------01:51:10.502 VOX.up.ifp.2 <--------- PPS-EOP ----------01:51:13.599 Info vox voip userplan 1 T38 page 1 OK, call-id: 29.
01:51:13.599 VOX.up.ifp.2 ------------ MCF ------------>
01:51:15.282 VOX.up.ifp.2 <----------- DCN ------------01:51:15.846 Info vox voip controlplan 3 Call Disconnection received on local port: 5/2,
cause: (16)[Normal call clearing], call-id: 29.
Copyright © OneAccess Networks – All rights reserved
14
Modem / fax pass-through event

Example of event in case of modem/fax call.
One_training>event filter add vox all show
00:11:21.485 Info vox voip controlplan 3 Incoming call on voip id: 0, calling: 111,
called: 110, call-id: 3.
00:11:21.486 Info vox voip controlplan 3 Outgoing call on local port: 5/0, calling: 111,
called: 110, call-id:3.
00:11:21.550 Info vox voip controlplan 3 Alert received, call-id: 3.
00:11:21.631 Info vox voip controlplan 3 Call connected, call-id: 3.
00:11:25.142 Info vox voip userplan 1 Fax/Modem Passthrough starting call-id: 3.
00:11:25.142 Info vox voip userplan 3 RTP new transmission coder: G711 A Law, call-id: 3.
00:11:25.341 Info vox voip userplan 3 RTP new reception coder: G711 A Law, call-id: 3.
00:12:23.533 Info vox voip controlplan 3 Call Disconnection received on local port: 5/1,
cause: (16)[Normal call clearing], call-id: 3.
00:12:23.552 Info vox voip userplan 3 VoIP RTP transmission stopped, coder: G711 A Law, call-id: 3.
00:12:23.552 Info vox voip userplan 3 VoIP RTP reception stopped, coder: G711 A Law, call-id: 3.
Copyright © OneAccess Networks – All rights reserved
15
VoIP: Data Processing

Unrestricted data processing ( CES codec )





Application case : videoconference H.320, data applications
over ISDN
Detected by the analysis of the Bearer Capability IE
Voice coding profile automatically restricted to G.711, no echo
cancellation and DTMF processing disabled
Configurable RTP Payload Type ( 101 by default )
Requires clock synchronization
Copyright © OneAccess Networks – All rights reserved
16
VoIP: Clock Synchronization



For modem and data calls, the local interfaces clock
must be synchronized with the local PBX port
Fax calls are often interrupted after 2/3 pages in
case of wrong clock synchronization
Several possibilities



Use of the xDSL clock (provided by the DSLAM )
Use of the ONE200/400 internal clock
(high accuracy: +/-30ppm)
Use of a local ISDN interface connected to the PSTN or PBX
(BRI or PRI protocol emulation isdn-te mode)
Copyright © OneAccess Networks – All rights reserved
17
VoIP: DTMF Processing

DTMF processing

Transparent mode



In band transmission



If G.711 coder used
Voice is not compressed, DTMF signal is transported as a voice signal
RTP frames carrying the DTMF tone indication instead of voice
RFC2833 (dedicated RTP packets with specific packet type)
SIP info

Use of sip info message (out of band transmission)
Copyright © OneAccess Networks – All rights reserved
18
Business-Class Router Solutions – All Telecommunication Services in One Access
OneOs Voice Configuration
Dial-Peer Concept
www.oneaccess-net.com
contact@oneaccess-net.com
v0.11 2007
Copyright © OneAccess Networks – All rights reserved
VoIP Configuration Diagram (H.323 / SIP)
ONE
CLASSICAL
TELEPHONE NETWORK
ISDN PBX
2
Voice Routing
Interface
Interface
BRI/PRI
BRI/PRI
BRI
PRI
BRI
5
VoIP Coder
Profile
4
Digital
1
Physical
Digital
Voice-port
Physical
Voice-port
Dial-Peer
3 Voice
POTS
Dial-Peer Voice
POTS
POTS Group 1
ISDN Phone
POTS
IP NETWORK
6
Analogue
1
Physical
Analogue
Voice-port
Physical
Voice-port
Dial-Peer
3 Voice
POTS
Dial-Peer Voice
POTS
Dial-Peer Voice
VoIP
Dial-Peer Voice
VoIP
7
H.323 or SIP
Gateway
8
SIP Server
POTS Group 2
SIP
Phones
Copyright © OneAccess Networks – All rights reserved
20
VoIP Configuration Diagram (MGCP)
ONE
CLASSICAL
TELEPHONE NETWORK
IP NETWORK
5
VoIP Coder
Profile
4
Dial-Peer Voice
VoIP
Analogue
1
Physical
Analogue
Voice-port
Physical
Voice-port
7
MGCP
Gateway
Dial-Peer
3 Voice
POTS
Dial-Peer Voice
POTS
POTS Group 2
Copyright © OneAccess Networks – All rights reserved
21