Posted by: Mudassir Ali | May 31, 2012

FoIP Fax Over IP

Cisco Live Webcast Archive: T38 Fax Over IP (FoIP) Training Video
T.38 Fax over IP Design Best Practices – Questions and Answers from live Webcastoice servi
ASK THE EXPERT – T.38 FAX OVER IP DESIGN
I have put above three links right on top, going through the video and Q&A will get you started on FoIP.

Fax Pass-Through: Passthrough is the simplest method, and it works by sampling and digitizing the analog fax signal just like a voice codec does for human speech.
While there are a number of codecs available, passthrough on Cisco voice gateways always uses the G.711 codec for carrying fax information because it offers the least distortion of the analog fax signals.




1. Transport of modem/fax signals through a packet network using PCM encoded packets.
2. A Fax tone triggers passthrough operation. After that, upspeed to g711, jitter buffers are locked and echo cancellation disabled
3. Fax tones are exchanged inband.
4. Fax Passthrough is a special case of Modem Passthrough. VBD (Voice Band Data) is Modem Passthrough.
Fax Pass-Through Global Configuration:
!
voice service voip
fax protocol pass-through g711ulaw ** This will cause all voip dial-peers to have fax protocol unless ‘no fax protocol’ is configured on the dial-peer**
!
Fax Relay: Relay is the other main method for transporting fax over IP, and its implementation is a bit more complicated than passthrough. Relay strips off the analog carrier from the fax signal in a process known as demodulation to expose the fax HDLC data frames.




1. Cisco currently supports two different types of relay on its voice products, T.38 fax relay and Cisco fax relay.
2. Cisco fax relay was a pre-standard fax relay implementation and is still the default on most Cisco voice gateways.
3. T.38 fax relay is the de facto standard for FoIP transport today and allows for interoperability with third party products.
!
voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 ** This will cause all voip dial-peers to have fax protocol unless ‘no fax protocol t38 …’ is configured on the dial-peer**
!

Sample Configuration:

Fax Pass-Through

H.323 Fax Pass-Through: Sample configuration
!
voice service voip
h323
modem passthrough nse codec g711alaw redundancy sample-duration 20
!
dial-peer voice 500 voip

 incoming called-number 800
 destination-pattern 550
 session target ipv4:10.100.00.00
 fax rate disable
 codec g726r32
!

SIP Fax Pass-Through: Sample configuration

!
voice service voip
 fax protocol pass-through g711ulaw
 sip
!
dial-peer voice 2000 voip
 fax rate disable
 fax protocol pass-through g711alaw
!

MGCP Fax Pass-Through: Sample configuration
!
Voice call carrier capacity active

!
mta receive maximum-recipients 0
!
ccm-manager mgcp
no ccm-manager fax protocol cisco
!
mgcp
mgcp call-agent 10.3.222.1 service-type mgcp version 0.1
mgcp modem passthrough voip mode nse
mgcp package-capability rtp-package
mgcp fax t38 inhibit
!

Cisco Fax Relay Fax Setup Call Flow

!
voice service voip
fax protocol cisco
!
interface Ethernet0/0
 ip address 10.0.47.47 255.255.0.0
 h323-gateway voip interface
 h323-gateway voip id ipaddr 10.0.47.36 1719
 h323-gateway voip h323-id 36402
!
dial-peer voice 14152 voip 
 destination-pattern 14152..
 session target ras
 fax protocol cisco

!

H.323 T.38 Fax Relay Call Flow

!
voice service voip
 fax protocol t38
!
interface Ethernet0/0
 ip address 10.0.47.47 255.255.0.0
 h323-gateway voip interface
 h323-gateway voip id ipaddr 10.0.47.36 1719
 h323-gateway voip h323-id 36402
!
dial-peer voice 14152 voip 
 destination-pattern 14152..
 session target ras
 fax protocol cisco
!

SIP T.38 Fax Relay

Platform Protocol Support
Common call control protocols used today in enterprise solutions include H.323, SIP, MGCP, and SCCP. Not all Cisco voice platforms support all of these protocols or all of the fax and modem features.

Configuration Guide:
Cisco Fax Services over IP Application Guide
Cisco IOS Fax, Modem, and Text Support over IP Configuration Guide, Cisco IOS Release 15.1M&T
T.38 Fax Relay for Voice over IP H.323 Configuration Guide
Cisco IOS Gatekeepers in Intrazone H.323 Networks Configuration Example
Configuring Fax Relay T.38 with VoIP
Fax Configuration on a Cisco WS-X6624 with an H.323 Gateway
Fax Relay Troubleshooting Guide
Faxing over IP Using Catalyst 6608 and VG248
T.37 OffRamp Faxing
T.37 OnRamp Faxing
Unity IP Fax Inbound Gateway Configuration Example
Unity IP Fax Outbound Gateway Configuration Example
How to configure fax pass-through over IP using a Cisco VG224 Voice Gateway running MGCP
Fax through the fax relay gateway takes twice the normal time compared to the fax call routed through the PSTN
Important G3 Timers
G3 Modulations
T.37 Fax Gateway store and forward fax receives only the first page
User finds it difficult to configure fax relay between a Cisco 6624 skinny or MGCP gateway and an H.323 Cisco IOS gateway
How to solve low memory problems in a Cisco IOS® gateway when used for T.37 store-and-forwardfax
Fax transmissions are slow, incomplete, and corrupted when a fax is sent at either the high speed baud rate of 144000 bps or at a low speed, such as 9600 bps
NSE Passthrough
Pass-through
How to configure Fax T.38 QuesCom solution with CCM
Faxing with SIP
SIP to MGCP T.38 Fax Fallback to Pass-Through and Voice

VG224:
Fax — PSTN — Voice Gateway — LAN — VG224 — Fax
The FXS ports on the VG224 Voice Gateway do not go off-hook, which results in a fast busy tone

ATA:
Fax — PSTN — Voice Gateway — LAN — ATA — Fax
The ATA only supports Fax-Passtrough.
Configuring and Troubleshooting the Cisco ATA 186 with Fax
Cisco ATA Configuring and Debugging Fax Services
How to send a fax through CallManager Express and ATA
Fax machines connected to a Cisco ATA cannot send faxes, or fax calls fail intermittently
How to configure DID passthru as DTMF to Fax Server when an ATA is used
The fax through ATA stopped to work after the Cisco CallManager Region Configuration changed to use G729 codec for calls to ATAs

Troubleshooting and Debug:
Fax over IP Troubleshooting Basics PDF
Fax Relay Troubleshooting Guide
H.323 T.38 Fax Relay Issues
Troubleshooting Fax
Cisco AVVID Gateway Support for Fax Relay and Fax Pass-Through

This slideshow requires JavaScript.


Fax Configuration on a Cisco WS-X6624 with an H.323 Gateway
Faxing over IP Using Catalyst 6608 and VG248
Identify, Supersede, and Maintain Compatible DSP Firmware Version Levels on C5510 DSPs
NetPro Discussion Forums on Voice over IP
T.37 OffRamp Faxing
T.37 OnRamp Faxing
Toll-Fraud Prevention Feature in IOS Release 15.1(2)T
Unity IP Fax Outbound Troubleshooting
VoFR VTSP Debugging
Voice Telephony Service Provider Debugging
Working Examples of T.30 Debugs
1. show voice call summary—Displays fax relay voice port settings.
2. show voice dsp—Displays fax relay digital signal processor (DSP) channel status.
3. debug voip application stcapp all— Displays SCCP telephony control (STC) application fax relay information.
4. debug voip dsm all—Displays fax relay DSP stream manager (DSM) messages.
5. debug voip dsmp all—Displays fax relay distributed stream media processor (DSMP) messages.
6. debug voip hpi all—Displays gateway DSP fax relay information on RTP packet events.
7. debug voip vtsp all—Displays gateway voice telephony service provider (VTSP) debugging information for fax calls.

Reference:
Implementing Fax over IP Chalk Talk

Books:
Fax, Modem, and Text for IP TelephonyBy David Hanes, Gonzalo Salgueiro. Published by Cisco Pres

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