understanding integrating and troubleshooting fax communications in today's enterprise … ·...

Understanding, Integrating, and T bl h ti F C i ti iTroubleshooting Fax Communications in Today's Enterprise Networks

BRKUCC-2021

AgendaAgenda

Fundamental Conceptsp

Fax Transport Methods

QoS ConsiderationsQoS Considerations

Design Best Practices

Troubleshooting Troubleshooting

Fax Servers

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 2

Fundamental Concepts


Fax CommunicationsFax Communications

Fax invented by Alexander Bain in 1843 (patented 30 years before the telephone)

Fax is a ubiquitous form of Fax is a ubiquitous form of communication today and Fax over IP (FoIP) is often overlooked i IP T l hin IP Telephony

Group 3 (G3) is today’s fax standard (speeds up to 14 4 kbps)standard (speeds up to 14.4 kbps)

Super G3 is an optional extension of G3 that allows for speeds up to


Alexander Bain’s Facsimile Apparatus,British Patent 9745

p p33.6 kbps

G3 Fax ProtocolsG3 Fax Protocols

Modern fax communication is based on the Group 3 (G3) fax standard, which is composed of the ITU-T specifications of T.30, T.4, and T.6

T 30 details the signaling T 4 specifies the Modified T.30 details the signaling, T.4 specifies the Modified Huffman (MH) and Modified Read (MR) encoding methods, and T.6 covers Modified Modified Read (MMR)

T.4/T.6—Specifies the Fax Page Encoding Algorithm

PSTN


T.30—Signaling and Negotiation Between Fax Machines

Basic G3 Fax TransactionBasic G3 Fax Transaction

The optional Called Subscriber Identification

Sending Fax Receiving Fax

Offhook then dialRinging, Offhook, Ans erSubscriber Identification

(CSI) and Non-Standard Facilities (NSF) messages may be transmitted along with the DIS message

Offhook, then dialCalling Tone (CNG)

Answer

Called Tone (CED)with the DIS message The optional Transmitting

Subscriber Identification (TSI) message may be transmitted along with the

Digital Identification Signal (DIS)

T i i Ch k (TCF)

Digital Command Signal (DCS)

transmitted along with the DCS message

Blue messages indicate low speed T.30 signaling and gold messages

Training Check (TCF)

Confirmation (CFR)

Fax Page Transmissionand gold messagesrepresent higher speed modulations used in training and page transmission

End of Procedure (EOP)

Message Confirmation (MCF)

Fax Page Transmission


Disconnect (DCN)

Super G3 Fax G3 Fax Call InitiationSuper G3 Fax

Super G3 uses the V.34 d l ti t hi

G3 Fax Call Initiation

CNG

CED

OriginatingFax

TerminatingFax

modulation to achieve page transmission speeds up to 33.6 Kbps

CED

DIS

compared to the maximum G3 speed of 14.4 Kbps

Super G3 Fax Call Initiation

CNGOriginatingF

TerminatingF

p

The signals used by SG3 are different than G3 and

tl

Fax Fax

ANSam

Calling Menu (CM)are currently incompatible with T.38 and Cisco fax relay.

Joint Menu (JM)

CJ Terminator


DIS

Transporting Fax Over IPTransporting Fax Over IP

The default behavior for Cisco voice gateways is to g yinitially handle all calls as voice calls so all fax calls start as voice calls

C d i d t d i d t Compressed voice codecs are not designed to handle modulated data so alternative, real-time transport methods must be utilized

There are two principal methods of transporting fax communications

1. Passthrough2 Relay


2. Relay

Transporting G3 Fax Protocols Over IPTransporting G3 Fax Protocols Over IP


PSTN

How Do Standard Fax Communications Integrate With IP Networks?T.30—Signaling and Negotiation Between Fax Machines

How Do Standard Fax Communications Integrate With IP Networks?


Passthrough or RelayTransport

IP


T.30—Signaling and Negotiation Between Fax Machines

PassthroughPassthrough

Modulated fax data information is sampled and encoded as standard Pulse Code Modulation (PCM) (i.e., G.711) and encapsulated in Real Time Protocol (RTP) for transport over IP just like a voice codec does for human speech

From the gateway perspective, this is more or less a G.711 voice call

Commonly referred to as Voice Band Data (VBD)

A l A lEnd-to-End Modulated Data

Analog Modulated Data

RTP Packet with PCM Payload

RTP RTP RTP

Analog Modulated Data


IP

RelayRelay

The analog modulated fax data is demodulated by a Digital Signal Processor (DSP) on the gateway and the binarySignal Processor (DSP) on the gateway and the binary information is extracted

Binary information is passed over IP using one of several y p gavailable relay protocols

A DSP on the destination gateway takes the binary information from the relay packets and re modulates it into ainformation from the relay packets and re-modulates it into a fax data signal on the telephony side

Analog Analog Relay ProtocolgModulated Data

gModulated Data

RelayRelayRelay

Relay Protocol

01101010 11000111 10100101 00101011

Relay


IP

The SwitchoverThe Switchover

All modulated calls TGWOGW

begin as voice calls

The process that transitions a gatewaytransitions a gateway from a VoIP call to the final fax media stream is k th it h

VoIP Call

known as the switchover

There are a variety of different switchover

Switchover

different switchover mechanisms that we will discuss throughout this presentation

Fax Call


presentation

Fax/Modem Media

Fax Transport Methods


Fax Transport MethodsFax Transport Methods

FaxFaxover IP

Passthrough Relay

FaxPassthrough

(NSE)

FaxPass-through

(Protocol)

T.38Fax Relay(Protocol)

T.38Fax Relay

(NSE)Cisco

Fax Relay


( ) (Protocol) (Protocol) (NSE)

Fax Passthrough Switchover MethodsFax Passthrough Switchover Methods

VoiceVoiceMode

NSE-Based Protocol-BasedNSE Based Switchover

Protocol Based Switchover

Fax Passthrough

Fax Pass through

Passthrough Switchover:1. Codec upspeed

Passthrough Pass-through2. VAD disabled on DSP3. Jitter buffer transitions from

adaptive to a fixed optimum value


Fax Passthrough

Passthrough TerminologyPassthrough Terminology

“Fax Passthrough” generically refers to passing fax calls over the G 711 codecG.711 codec

“Fax Passthrough” can also refer to the more specific passthrough transport method using an NSE switchover to pass faxes over G.711

“Modem Passthrough” is a general term used to refer to an NSE-based switchover to passthrough for both fax and modem calls because it is the syntax used by the configuration command for this featurethis feature

The underlying operation of “modem passthrough” is different depending on whether it is a fax or a high speed modem call, so to avoid confusion we will refer to “modem passthrough” for a fax call as “fax passthrough” and “modem passthrough” for a modemcall as fax passthrough and modem passthrough for a modem call as “modem passthrough”

“Fax pass-through” details a switchover to passthrough using the call control protocol


Passthrough Switchover MechanismsPassthrough Switchover MechanismsTone Detection1RTP RTP RTPNSE NSE NSENSE-Based

Switchover 2IP

3Protocol-Based Switchover H.323 SIP

OGWTGW

Terminating Gateway (TGW) initiates the switchover to passthrough upon detection of fax signals played by the

1answering fax device

2 If NSE-based passthrough is configured, the TGW sends NSE switchover packets in the RTP media stream uponNSE switchover packets in the RTP media stream upon detection of CED (G3 fax) or ANSam (SG3 fax) tones

3 If fax pass-through is configured, the TGW initiates the it h i th H 323 SIP ll t l t l


switchover in the H.323 or SIP call control protocols upon detection of fax message flags

Payload Types Used for Modulated DataPayload Types Used for Modulated Data

The Payload Type field identifies the type of data being carried in the RTP k t

Payload Type Payload Encoding

RTP packet

0818

G.711 µ-law

G.711 a-law

G 729

Static

189096

G.729

RFC 2198 Passthrough Redundancy

Cisco Fax Relay Switchover

97100

y

Cisco Fax Relay Switchover ACK

Named Signaling Event (NSE)DynamicAndUnassigned


119122

Cisco Text Relay

Cisco Fax Relay

g

Named Signaling Events (NSE)Named Signaling Events (NSE)

Cisco proprietary message sent as part of the RTP p p y g pstream to signal an event, such as a switchover

This form of signaling is call control independent

RTP P l dRTP H d

The Event ID field uses Cisco-defined event numbers to signal a specific task in-band

NSE

RTP PayloadRTP Header

PT

Payload Type =100


R VolumeEEvent ID Duration

NSE Events Used for Modulated DataNSE Events Used for Modulated Data

The NSE Event ID field uses Cisco-defined values

NSE Description

to signal in-band a variety of tasks

192193

Triggered by 2100Hz tone. Signals switchover to passthrough

Triggered by ANSam tone detection. Signal to disable ECANs

194199200

Triggered by 4s silence or carrier loss. Signals return to voice mode

Triggered by ANSam tone. Signals support of Cisco Modem Relay

T i d b f V 21 P bl Si l it h t T 38200201202

Triggered by fax V.21 Preamble. Signals switchover to T.38

ACK to NSE-200 confirming peer gateway switchover to T.38

NACK to NSE-200 implying peer gateway cannot switchover to T 38


202203

NACK to NSE 200 implying peer gateway cannot switchover to T.38

Triggered by V.8 CM detection. Signals transition to Modem Relay

Fax Passthrough Switchover (G3)Fax Passthrough Switchover (G3)TGWOGW

Th i iti l V IP ll

VoIP CallOGW: Upspeed codec d i h

The initial VoIP call can be setup by any of the common call control protocols (H 323 SIP MGCPand switch to

Passthrough mode

NSE-192 CED

(H.323, SIP, MGCP, or SCCP)

NSE-192

TGW: Upspeed codec and switch to

The underlying call control protocol is

f th and switch to Passthrough modeFax Passthrough Call

unaware of the transition to fax passthrough due to the protocol independent

t f th NSE


nature of the NSE switchover

Fax Passthrough Switchover (SG3)Fax Passthrough Switchover (SG3)TGWOGW

The initial VoIP call

VoIP Call

The initial VoIP call can be setup by any of the common call control protocols (H 323 SIP MGCP or

ANSamNSE-192

(H.323, SIP, MGCP, or SCCP)

NSE-192 TGW: Detect 2100 Hz tone. Upspeed codec and switch to Passthrough mode

OGW: Upspeed codec and switch to Passthrough mode NSE-193

NSE-193

SG3 Fax Call

Passthrough mode

OGW: Disable echo cancellers


SG3 Fax CallTGW: Detect phase reversal of ANSam. Disable ECAN

Confirming Fax Passthrough SwitchoverSwitchover

Before Switchover: show call active voice briefBefore Switchover: show call active voice brief

11F1 : 10 2924510ms.1 +10530 pid:1 Originate 200 activedur 00:00:07 tx:99/1903 rx:253/4993IP 1 1 1 2:17932 SRTP: off rtt:0ms pl:4810/0ms lost:0/0/0 delay:60/60/70ms g729r8IP 1.1.1.2:17932 SRTP: off rtt:0ms pl:4810/0ms lost:0/0/0 delay:60/60/70ms g729r8

VoIP Call

After Switchover: show call active voice briefAfter Switchover: show call active voice brief11F1 : 10 2924510ms.1 +10530 pid:1 Originate 200 activedur 00:00:22 tx:877/125447 rx:1040/128809IP 1.1.1.2:17932 SRTP: off rtt:1ms pl:40/0ms lost:0/0/0 delay:60/60/60ms g711ulaw p y gTextRelay: off media inactive detected:n media contrl rcvd:n/a timestamp:n/a long duration call detected:n long duration call duration:n/a timestamp:n/a MODEMPASSnse buf:0/0 loss 0% 0/0 last 1359s dur:0/0s


Fax Passthrough Call

nse buf:0/0 loss 0% 0/0 last 1359s dur:0/0s


Fax Passthrough ConfigurationFax Passthrough ConfigurationSIP/H.323:

dial-peer voice 1 voipmodem passthrough nse codec g711ulaw

(Note: Can be configured globally under voice service voip or the dialpeer for SIP and H.323. The configuration under the dialpeer takes precedence.)

IPRTP RTP RTPNSE NSE NSEFeature: fax passthrough

MGCP:

mgcp modem passthrough voip mode nsemgcp modem passthrough voip codec g711ulaw

SCCP:

voice service voip

mgcp modem passthrough voip codec g711ulaw


pmodem passthrough nse codec g711ulaw

(Note: Can only be configured globally under voice service voip for SCCP.)

Fax Pass-through Switchover (G3)Fax Pass through Switchover (G3)TGWOGW

Th i iti l V IP ll i

VoIP Call - SIP SignalingP th h CED T

The initial VoIP call is setup using the SIP call control protocol

g gPass-through parameters for the upcoming session are established in th SIP INVITE d

INVITE for G.711 Pass-through

CED Tone

V.21 Preamble

100 Trying

200 OK

the SIP INVITE and 200 OK messages

The V.21 Preamble of the first T 30 messageACK

Fax Pass through Call

the first T.30 message following the CED Tone (i.e. DIS) is the trigger for the transition to pass-through

An H.245 Request Mode for G.711 is used to signal the switchover


Fax Pass-through Call throughgin H.323 to fax pass-through mode

Confirming Fax Pass-through SwitchoverSwitchover

Before Switchover: show call active voice brief

126C : 58 11411290ms.1 +10520 pid:1 Originate 200 activedur 00:00:08 tx:112/2154 rx:307/6092IP 1.1.1.2:17620 SRTP: off rtt:1ms pl:5930/0ms lost:0/0/0 delay:60/60/70ms g729r8

VoIP CallAfter Switchover: show call active voice brief126C : 58 11411290ms.1 +10520 pid:1 Originate 200 activedur 00:00:41 tx:1677/252554 rx:1953/258112IP 1 1 1 2 17620 SRTP off rtt 4ms pl 40/0ms lost 1/0/0 dela 60/60/60ms g711 laIP 1.1.1.2:17620 SRTP: off rtt:4ms pl:40/0ms lost:1/0/0 delay:60/60/60ms g711ulawTextRelay: off

media inactive detected:n media contrl rcvd:n/a timestamp:n/a long duration call detected:n long duration call duration:n/a timestamp:n/a



long duration call detected:n long duration call duration:n/a timestamp:n/a

Fax Pass-through Call

Fax Pass-through ConfigurationFax Pass through ConfigurationSIP/H.323:

dial-peer voice 1 voipfax protocol pass-through g711ulaw

Note: Can be configured globally under voice service voip or the dialpeer for SIP and H.323. The configuration under the dialpeer takes precedence.

IPFeature: fax pass-through

H.323 RM SIP INVITE

MGCP:

Fax pass-through is NOT supported for MGCP


SCCP:

Fax pass-through is NOT supported for SCCP

Fax Transport MethodsFax Transport Methods

FaxFaxover IP

Passthrough Relay

FaxPassthrough

(NSE)

FaxPass-through

(Protocol)

T.38Fax Relay(Protocol)

T.38Fax Relay

(NSE)Cisco

Fax Relay


( ) (Protocol) (Protocol) (NSE)

Fax Relay Switchover MethodsFax Relay Switchover Methods

VoiceVoiceMode

Protocol-Based Switchover(Standards-Based) RTP PTRTP PT

SwitchoverNSE-Based Switchover

T 38 Fax CT 38 FaxT.38 FaxRelay

Cisco FaxRelay

T.38 FaxRelay


Fax Relay

Cisco Fax Relay (CFR)Cisco Fax Relay (CFR)

Pre-standard and proprietary fax relay implementation for y yG3 fax transmissions (no SG3 support)

Default fax transport method on most Cisco voice gateways

Uses a unique Payload Type switchover that is not used by any other modulated communication transport method

RTP Payload Type is set to 122 for Cisco

Demodulated fax HDLC data carried in the Cisco Fax Relay packet

Fax Relay data

UDP Header

IP Header

RTP Header Cisco Fax Relay PacketCisco Fax Relay Packet

y p


Cisco Proprietary Formatting

Cisco Fax Relay Switchover (G3)Cisco Fax Relay Switchover (G3)TGWOGW

VoIP CallThe TGW notifies the OGW of the impending

V.21 PreamblePT-96 CFR Switchover

OGW of the impending switchover with a special RTP message using a PT value of 96

PT-96 CFR SwitchoverThe detection of fax

PT-97 CFR Switchover ACK

PT-97 CFR Switchover ACK

Cisco Fax Relay Call

flags (V.21 Preamble) at the TGW triggers the transition to CFR.

The CFR switchover packet is ACK’d with PT-97 message


Cisco Fax Relay Callg

Confirming Cisco Fax Relay SwitchoverConfirming Cisco Fax Relay Switchover


121C : 26 1027355900ms.1 +10510 pid:1 Originate 200 activedur 00:00:11 tx:117/2244 rx:424/8432IP 1.1.1.2:18274 SRTP: off rtt:2ms pl:7810/0ms lost:0/0/0 delay:60/60/70ms g729r8

VoIP CallAfter Switchover: show call active voice brief121C : 26 1027355900ms.1 +10510 pid:1 Originate 200 activedur 00:00:45 tx:1113/22164 rx:1001/19972IP 1 1 1 2 182 4 SRTP ff 2 l 0/0 l 0/0/0 d l 0/0/0 i T R l ffIP 1.1.1.2:18274 SRTP: off rtt:2ms pl:0/0ms lost:0/0/0 delay:0/0/0ms cisco TextRelay: off



Fax Passthrough CallCisco Fax Relay Call

Cisco Fax Relay ConfigurationCisco Fax Relay ConfigurationSIP/H.323:

dial-peer voice 1 voipfax protocol ciscofax protocol cisco

Note: CFR is the default fax configuration on most IOS gateways.

IPRTP RTPPT-97 PT-96Feature: Cisco Fax Relay

MGCP:ccm-manager fax protocol ciscomgcp fax t38 inhibit

SCCP:

voice service voipfax protocol cisco

Note: Like CFR, T.38 is also enabled by default for MGCP. However T.38 takes precedence over CFR and must be explicitly disabled with mgcp fax t38 inhibit.


Note: CFR can only be configured under voice service voip for SCCP starting in IOS Release 12.4(11)T.

T.38 Fax RelayT.38 Fax Relay T.38 is the de facto standard for handling fax transmissions today

Cisco has always supported the 1998 version (known as version 0) Cisco has always supported the 1998 version (known as version 0) of the ITU-T T.38 specification with UDP/UDPTL encapsulation

In IOS version 15.1(1)T Cisco started supporting SG3 fax over T.38 ( )(version 3)

Cisco products can use either NSEs (proprietary) or the call control protocol (standards-based) to switch a call to T.38 modep ( )

UDP Transport Layer(UDPTL) header is simply

T.38 Internet Fax Packets (IFP) and optional redundancy packets

UDP IP UDPTL UDPTL Payload (T 38UDPTL Payload (T 38 IFPsIFPs))

(UDPTL) header is simplya 2 byte sequence number

and optional redundancy packets are carried in the UDPTL payload


HeaderHeader Header UDPTL Payload (T.38 UDPTL Payload (T.38 IFPsIFPs))

UDP Encapsulated T.38

T.38 Switchover—NSE (G3)T.38 Switchover NSE (G3)TGWOGW

The initial VoIP call

VoIP CallOGW: Transition from voice mode to T.38

can be setup by any of the common call control protocols (H.323, SIP, MGCP, or

NSE-200V.21 Preamble

(SCCP)

NSE-201 The detection of fax flags (V.21 Preamble) at the TGW triggers the t iti t T 38

T.38 Fax Relay Calltransition to T.38


TGW: T.38 ACK received, start T.38 session

T.38 Switchover—H.323 (G3)T.38 Switchover H.323 (G3)TGWOGW


VoIP Call—H.323 SignalingT.38 parameters for the upcoming fax relay

The initial VoIP call is setup using the H.323 call control protocol

g g

V.21 PreambleH.245 Request Mode T.38

upcoming fax relay session are negotiated in the H.245 Request Mode messages

H.245 Request Mode T.38 ACK

Closing of Voice Logical ChannelsEach gateway closes its voice media

T 38 Fax Relay Call

The detection of fax flags (V.21 Preamble) at the TGW triggers the transition to T.38

Opening of T.38 Logical Channelschannel and opens a T.38 fax relay media channel while acknowledging the


T.38 Fax Relay Callsame events by the other side

T.38 Switchover—SIP (G3)T.38 Switchover SIP (G3)TGWOGW


VoIP Call - SIP Signaling

T.38 parameters for the upcoming fax relay session are negotiated

The initial VoIP call is setup using the SIP call control protocol

g g

INVITE for T.38 modeV.21 Preamble

session are negotiated in the SIP INVITE and 200 OK messages

100 Trying

200 OKThe detection of fax flags (V.21 Preamble) at the TGW triggers the

T 38 Fax Relay Call

ggtransition to T.38 ACK

T.38 fax relay


T.38 Fax Relay Call switchover process using the SIP protocol stack is complete

T.38 Switchover—MGCP (G3)T.38 Switchover MGCP (G3)TGWOGW

Call AgentTh i iti l V IP ll i

VoIP Call - MGCP Signaling

The initial VoIP call is setup using the MGCP call control protocol

MGCP NTFYV.21 Preamble

200 OK

200 OK

TGW notifies the CA that fax V.21 flags are detectedMDCX - T.38

CA instructs OGW to switchover to T.38 with an MDCX message 200 OK

200 OKCA instructs TGW to switchover to T 38

MDCX- T.38

message


T.38 Fax Relay Call

200 OK switchover to T.38 with an MDCX message

T.38 Switchover—SIP (SG3)T.38 Switchover SIP (SG3)TGWOGW

The initial VoIP call is setup using the SIP

VoIP Call - SIP Signaling

ANSam is sent across in the RTP media stream

ANSANS

setup using the SIP call control protocol

INVITE for T.38 mode T.38 fax relay switchover process

ANSam(ANSam tunneled in voice codec)

CM

ANSam

100 Trying

200 OKThe detection of

using the SIP protocol stack is complete

T 38 SG3 Fax Relay Call

Calling Menu (CM) at the OGW triggers the transition to T.38

ACKNote: CM is squelched by the OGW DSP and sent over T.38. The


T.38 SG3 Fax Relay Call CM/JM exchange is done entirely over T.38 prior to T.30 negotiation

Confirming T.38 Fax Relay SwitchoverConfirming T.38 Fax Relay Switchover


11E2 : 4 2956390ms.1 +10500 pid:1 Originate 200 activedur 00:00:11 tx:117/2244 rx:436/8643IP 1.1.1.2:18496 SRTP: off rtt:3ms pl:4800/0ms lost:0/0/0 delay:60/60/70ms g729r8

VoIP CallAft S it h h ll ti i b i fAfter Switchover: show call active voice brief11E2 : 4 2956390ms.1 +10500 pid:1 Originate 200 activedur 00:00:46 tx:707/13770 rx:914/12339IP 1 1 1 2:18496 SRTP: off rtt:3ms pl:4800/0ms lost:0/0/0 delay:60/60/70ms t38IP 1.1.1.2:18496 SRTP: off rtt:3ms pl:4800/0ms lost:0/0/0 delay:60/60/70ms t38TextRelay: off



Fax Passthrough Calllong duration call detected:n long duration call duration:n/a timestamp:n/a

T.38 Fax Relay Call

NSE-Based T.38 ConfigurationNSE Based T.38 ConfigurationSIP/H.323:

dial-peer voice 1 voipfax protocol t38 nse ls-redundancy 0 hs-redundancy 0 fallback ciscofax protocol t38 nse ls redundancy 0 hs redundancy 0 fallback cisco

Note: Configured globally under voice service voip or the dialpeer for SIP and H.323. The dialpeer configuration takes precedence.

IPFeature: NSE-Based T.38

RTP RTP RTPNSE NSE NSE

SCCP

MGCP:

Enabled by defaultSCCP:voice service voip

fax protocol t38 nse ls-redundancy 0 hs-redundancy 0 fallback cisco

N t C l b fi d d i i i f SCCP Ci IOS t

Note: no mgcp fax t38 inhibit is required but is default.


Note: Can only be configured under voice service voip for SCCP. Cisco IOS gateway support for NSE-based T.38 fax relay with the SCCP voice signaling protocol is introduced in Cisco IOS Release 12.4(11)T.

Protocol-Based T.38 ConfigurationProtocol Based T.38 ConfigurationSIP/H.323:

dial-peer voice 1 voipfax protocol t38 version [0|3] ls-redundancy 0 hs-redundancy 0 fallback cisco

Note: version 0 configures legacy T.38 G3 fax support, whereas version 3 enables the newly supported SG3 over T.38 feature [as of 15.1(1)T]

IPMGCP NTFYFeature: Protocol-Based T.38

H.323 RM SIP INVITE

MGCP:

mgcp package-capability fxr-packagemgcp default package fxr package

SCCP:

SCCP does not support

mgcp default-package fxr-package

Note: These two commands are needed to go from the default configuration of NSE-based T.38 to protocol-based T.38. The command no mgcp fax t38


ppprotocol-based (version 0 or version 3) T.38

ginhibit is required for both NSE and protocol-based T.38, but it is the default.MGCP does not offer any version 3 support.

QoS Considerations


Are VoIP QoS Policies Sufficient for Fax?Fax?

In many cases, fax

Headquarters

devices are located where VoIP is already installed

You can “piggyback” You can piggyback fax traffic onto the same QoS policy implemented f V IPfor VoIP

As a rule of thumb, if good voice quality exists

IP

good voice quality exists between locations, then fax communications should also work


should also work

Branch 1 Branch 2 Branch 3

QoS Network FactorsQoS Network Factors

TerminatingGateway

OriginatingGateway

Packet Loss Jitter

GatewayGateway

T.38T.38 T.38T.38T.38

Delay

Delay or latency: the amount of time it takes a packet to

Delay

travel from source to destination

Packet loss: the amount of packets that are f l i i i t th d ti tiunsuccessful in arriving at the destination

Jitter: the measure of the variability over time of the latency across a network


latency across a network

FoIP and Packet LossFoIP and Packet Loss

OriginatingGateway

TerminatingGateway

T.38 Fax PacketsGateway Gateway

IFP 2(Primary)

IFP 1(Secondary)

IFP 3(Primary)

IFP 2(Secondary)

IFP 1(Primary)

Fax over IP (FoIP) is generally more affected by packet

T.38 Fax Relay With Redundancy Level Set to 1

loss than VoIP

Ideally no packet loss should occur for a fax call

If packet loss is present then use T.38 with redundancy

Enabling T.38 redundancy requires more bandwidth


FoIP and DelayFoIP and Delay

Multiple IP and PSTN hops areprime sources of additional delay

PSTN

IP

p y

Satellite linkscause large

Delay is not as impacting to FoIP compared to VoIP

PSTN IPIP cause largeamounts of delay

Delay is not as impacting to FoIP compared to VoIP

FoIP calls have been known to handle network delays of 1 second or more

However, as a best practice it is still recommended to minimize network delays as much as reasonably possible because too much delay will cause FoIP calls to fail


Watch out for multiple IP and PSTN hops and satellite links

FoIP and JitterFoIP and JitterVariably spaced T.38 packets arrive at the playout buffer and

Packets are re-sequenced if necessary and placed in

Evenly spaced packets are played out to the DSP for p y

some may even be out of sequence

if necessary and placed in the required order for playout

transmission on the PSTN

DSP

IP11

Fax

8

Fax

10

Fax

9

Fax

7

Fax

6

Fax

5

Fax

4

Fax

3

Fax

2

Fax

1

Fax

DSPCodec(T.38)

T.38 and Cisco fax relay use 300 ms fixed jitter or playout buffers300 ms Fixed Playout Buffer

Fax passthrough uses the last voice mode setting before the switchover

With large playout buffers, FoIP can handle larger amounts of jitter


g p y g jthan VoIP but as a best practice it is still recommended to keep jitter to a minimum

QoS Design Parameters for FaxQoS Design Parameters for Fax

Delay Jitter Packet Loss

< 150 ms < 30 ms < 1%Voice (one-way,

(mouth to ear)(average, one-way)

< 1000 ms < 300 ms for None* unless

Fax

< 1000 ms < 300 ms for fax relay, < 30 ms for passthrough

None , unless using T.38 with redundancyp g y

*Fax passthrough is very sensitive to packet loss and may be able to handle 0 1%–0 2% loss


Fax passthrough is very sensitive to packet loss and may be able to handle 0.1% 0.2% loss depending on when in the fax transaction the loss occurs and if it is consecutive packets. Cisco fax relay can handle more loss than passthrough but T.38 with redundancy is still the best choice for fax calls when packet loss is occurring.

QoS Marking Configuration on GatewaysGateways

IPT.38 T.38

Fax Gateway

dial-peer voice 100 voipdestination-pattern 100session target ipv4:10.1.1.1fax protocol t38 ls redundancy 0 hs redundancy 0

cae-dh-3660#show dial-peer voice 100<snip>type = voip, session-target = `ipv4:10.1.1.1',

technology prefix:

F d d t t Q S ki i DSCP b i l

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback ciscoip qos dscp cs3 signaling

technology prefix: settle-call = disabledip media DSCP = ef, ip signaling DSCP = cs3,

<snip>

Fax, modem, and text QoS marking via DSCP can be simply added at the dial-peer level for H.323 and SIP or globally for MGCP with the command “mgcp ip qos dscp”

Dial peer QoS markings can be viewed with the command show Dial-peer QoS markings can be viewed with the command show dial-peer voice

Default dial-peer QoS markings are af31 for signaling and effor media


for media Cisco recommended best practice is to use cs3 for signaling

QoS Marking and Shaping ExampleQoS Marking and Shaping ExampleCLASSIFICATION & MARKING QUEUEING & DROPPING POST-QUEUING OPERATIONS

Fax FaxOGW TGW

IP

dial-peer voice 919 voipdestination-pattern 919.......

class-map match-all fax_voicematch ip dscp efclass-map match-any call_signaling

h i d 3

PCPhone PhonePC

psession target ipv4:10.0.0.19fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback ciscoip qos dscp cs3 signalingno vad

match ip dscp cs3 match ip dscp af31 !policy-map WANclass fax_voicepriority percent 33


no vad priority percent 33class call_signalingbandwidth percent 5

class class-defaultfair-queue

Voice and T.38 fax traffic can share the same QoS marking and shaping.

Design Best Practices


Design Best PracticesDesign Best Practices

Unified Communications Integration MethodsgCisco Unified Communications Manager, Gateway-ControlledCisco Unified Communications Manager CA-ControlledCisco Unified Communications Manager, CA-Controlled

Design considerationsBandwidth utilizationBandwidth utilizationSuper G3Protocol and product supportSIP Trunking and FoIP SupportT.38: de facto standard


Gateway to GatewayGateway to Gateway

Gateway Gateway

H.323/SIP Voice Signaling

H.323/SIP Fax Signaling

IPFax Gateway FaxGateway

Voice MediaVoice Media

NSE/PT Switchover

All signaling and media packets are exchanged between the voice

Fax Media

All signaling and media packets are exchanged between the voice gateways

NSE-based switchovers (fax passthrough and NSE-based T.38) and payload type switchovers (Cisco fax relay) happen within the voice media


p y yp ( y) ppstream while protocol-based switchovers (fax pass-through and protocol-based T.38) happen within the call control protocol

Cisco Unified Communications Manager, Gateway-ControlledManager, Gateway Controlled

H.323/SIP/MGCP/SCCPH.323/SIP/MGCP/SCCP

Unified CM


Voice MediaNSE/PT Switchover

Switchover for fax passthrough, NSE-based T.38, and Cisco fax relay occurs within

Voice media is established by Unified CM using the H.323, SIP, MGCP, or SCCP

Fax Media

fax relay occurs within the voice media stream

SIP, MGCP, or SCCP protocols

Cisco Unified Communications Manager (Unified CM) controls the setup of the initial voice call between the gateways using standard call control signaling such as H.323, SIP, MGCP, and SCCP


The switchover to a fax media stream is handled by the gateways themselves without the knowledge of Unified CM

Cisco Unified Communications Manager, Gateway ControlledManager, Gateway Controlled

Use Cisco Unified Communications Manager, Gateway-C t ll d h Ci U ifi d C i tiControlled, when a Cisco Unified Communications Manager version does not support a certain fax media negotiation in the call control protocol (like T.38) NSE-based T.38 allows for T.38 to occur even if a Cisco

Unified Communications Manager version does not offer T.38 support within the call control protocol This integration method must also be used with non-

standard switchover mechanisms such as fax passthrough and Cisco fax relay Remember that NSE and PT switchovers are Cisco

proprietary and this integration method only works with Cisco devices and not third-party equipment


p y q p

Cisco Unified Communications Manager, CA-ControlledManager, CA Controlled

Unified CM


Voice Media Switchover for protocol-based T.38 is handled by Unified CM within the

Voice media is established by Unified CM using the H.323,

Cisco Unified Communications Manager controls the setup of the initial i ll b t th i t d t l th it h t T 38

T.38 Media call control protocolSIP, or MGCP protocols

voice call between the voice gateways and controls the switchover to T.38 fax relay

Instead of the gateways independently handling the switchover, Cisco Unified Communications Manager coordinates the switchover using the


Unified Communications Manager coordinates the switchover using the call control protocol

Cisco Unified Communications Manager, CA-ControlledManager, CA Controlled

Recommended as a best practice! Only protocol-based T.38 (using H.323, SIP, or MGCP)

is capable of this integration method This integration method is standards based and allows This integration method is standards-based and allows

for interoperability with third-party devices such as gateways and fax serversIf Ci U ifi d C i ti M d i If Cisco Unified Communications Manager and voice gateways support this integration method then this is recommended compared to the Cisco Unified Communications Manager Gateway-Controlled methodCommunications Manager, Gateway-Controlled method which depends on proprietary switchover mechanisms T.38 support within Cisco Unified Communications

Manager varies depending on software version


Manager varies depending on software version

Cisco Unified Communications Manager and T.38 SupportManager and T.38 Support

Call Control Protocol Support for T.38

Cisco Unified Communications Manager S fSoftware Release

H.323 4.1(1), 4.2(3), 5.0(1), and 6.0(1)

H.323 and MGCP 4.2(3) and 6.0(1)H.323 and SIP 5.0(1) and 6.0(1)H 323 SIP and MGCP 6 0(1) and later

Only release 6.0(1) and later offers support for T 38 ithi th ll t l t l f H 323 SIP

H.323, SIP, and MGCP 6.0(1) and later

T.38 within the call control protocols of H.323, SIP, and MGCP

The SCCP protocol only handles T 38 using an


The SCCP protocol only handles T.38 using an NSE-based switchover

Design Best PracticesDesign Best Practices

Unified Communications Integration MethodsgCisco Unified Communications Manager, Gateway-ControlledCisco Unified Communications Manager CA-ControlledCisco Unified Communications Manager, CA-Controlled

Design considerationsBandwidth utilizationBandwidth utilizationSuper G3Protocol and product supportSIP Trunking and FoIP SupportT.38: de facto standard


FoIP Bandwidth UtilizationFoIP Bandwidth Utilization

Different FoIP transports use varying amounts of

Codec Bandwidth1

use varying amounts of bandwidth

On links where saving

G.711 (64 Kbps) 83 Kbps

G.729 (8 Kbps) 27 Kbps

bandwidth is a priority then relay is a better choice

T.38 redundancy handles

G.723 (6.3 Kbps) 19 Kbps

Fax passthrough/pass-through (G.711) 83 Kbpsy

packet loss much better than fax passthrough/ pass-through with redundancy

Fax passthrough (G.711) with redundancy 170 Kbps

T.38 (no redundancy) 25 Kbps2( y) p

T.38 (redundancy level 1) 41 Kbps2

T.38 (redundancy level 2) 57 Kbps2

1Values are approximate with Ethernet or Frame Relay headers

2Values are peak and only occur during the


( y ) p

Cisco fax relay 48 Kbps2

Values are peak and only occur during the sending of a page at 14.4 Kbps; gateways can force lower fax speeds for additional bandwidth savings

Methods for Handling SG3 Fax CallsMethods for Handling SG3 Fax Calls Sending Fax Receiving Fax

OGW TGW

CNGCNG

ANSam

CMSending faxi i i SG3 ll

Sg3-to-g3 spoofingf OGW

Absence of SG3 CM causesf GCM

DIS

initiates SG3 callby sending CM

feature on OGWblocks CM message

receiving fax to initiate G3fax procedures (DIS message)

The sg3-to-g3 spoofing feature forces Super G3 fax calls to negotiate down to G3 speeds for compatibility with T.38 or Cisco fax relay

Modem passthrough will handle SG3 calls at their native speedsModem passthrough will handle SG3 calls at their native speeds

Fax pass-through is not compatible with SG3 because of its dependency on the V.21 flags found in G3 negotiations for initiating the switchover

Starting in IOS 15 1(1)T SG3 over T 38 is supported and these other methods


Starting in IOS 15.1(1)T SG3 over T.38 is supported and these other methods for handling SG3 faxes are not necessary

Error Correction Mode (ECM)Error Correction Mode (ECM) Sending Fax Receiving Fax

OGW TGW

CNGCNG

DIS (ECM enabled)

CED

DIS (ECM disabled)

DCS (ECM disabled)

( )( )

ECM support indicatedin DIS message

TGW overwritesECM setting to disabled

Sending fax believes receivingfax does not support ECM

DCS (ECM disabled)

ECM ensures error-free transmission of fax pages

When ECM is disabled, fax pages can proceed with minor errors that mayWhen ECM is disabled, fax pages can proceed with minor errors that may or may not be noticeable

Cisco gateways can force ECM to be disabled when configured for T.38 or Cisco fax relay


Disabling ECM may be useful for scenarios where network impairments make it difficult for ECM to be efficient

T.38 FallbackT.38 Fallback Receiving Fax3845 TGW

dial-peer voice 100 voipfax protocol t38 ls-redundancy 0hs-redundancy 0 fallback cisco

Sending Fax OGW

IPT.38 supported by 3845and call is successful

6608 TGWReceiving FaxT.38 call fails to 6608

but fallback to Ciscofax relay is successful

For increased interoperability, T.38 fax relay can fall back to Cisco fax relay or fax pass-through if the initial T.38 negotiation fails

T.38 also has an automatic fallback mechanism that tries a protocol based T 38 fax relay switchover if the


tries a protocol-based T.38 fax relay switchover if the configured NSE-based switchover fails

FoIP Call Control Protocol SupportFoIP Call Control Protocol Support

Transport M th d

H.323 SIP MGCP SCCPMethodCisco fax relay

Yes* Yes* Yes* Yes*

NSE-basedT.38

Yes Yes Yes Yes

Protocol- Yes Yes Yes Nobased T.38Fax pass-through

Yes Yes No No

Modem passthrough

Yes Yes Yes Yes


*IOS platforms such as the 5350, 5400, and 5850 utilizing the Nextport DSP cards do not support Cisco fax relay

FoIP Product Support CaveatsFoIP Product Support Caveats

Cisco ATA only supports NSE-based passthrough ( d th h)(modem passthrough) SCCP voice gateways (IOS or VG248) do not support

any protocol-based switchovers(like fax pass-through y p ( p gand protocol-based T.38), so NSE-based T.38 and modem passthrough must be used MGCP gateways do not support fax pass-through, onlyMGCP gateways do not support fax pass through, only

modem passthrough can be utilized Legacy Nextport DSP platforms (AS5350, AS5400, and

AS5850) do not support Cisco fax relayAS5850) do not support Cisco fax relay Legacy 6608 and 6624 cards only support Cisco fax

relay and modem passthrough


SIP Trunks and FoIPSIP Trunks and FoIP SIP Trunks typically use three different methods to transport

standard G3 fax callsG.711 Voice - All calls (voice and fax) are always sent using the G.711 voice codecPass-through - A SIP RE-INVITE message is used to up-speed to G.711 when a fax tone is detectedT.38 Fax Relay – Call is switched to T.38 fax relay using a SIP RE-INVITE when a fax tone is detected

Fax Method T 38 Fax Relay G 711 Voice Pass throughFax Method T.38 Fax Relay G.711 Voice Pass-through

Pros Highest fax success rates can be achieved Cleanest solution from

signaling and media point f i

Most widely deployed Simplest solution

Provides bandwidth savings as G.729 voice call only upspeedsto G.711 if call is fax

of view Use less bandwidth

than G.711

Cons Interoperability between different vendors

Consumes a large amount of bandwidth for all calls

Interoperability between different vendors


Not offered by many Service Providers

Sensitive to impairments, no redundancy

Not supported by Cisco Unified Communications Manager Sensitive to impairments, no

redundancy

T.38: De Facto Standard for FoIPT.38: De Facto Standard for FoIPT.38 CFR Fax Pass-

throughFax

PassthroughStandards-Based, Third-Party Integration

Low Bandwidth

Redundancy

Fallback MechanismsSRTP and CRTP SupportLegacy Platform Support


T.38 Should Always Be Your First Choice When Handling FoIP Traffic!

Troubleshooting


Call Troubleshooting StagesCall Troubleshooting Stages

Any fax call can be Gateway Gateway

broken down into three troubleshooting stages1. Initial Voice Call

H.323/SIP/MGCP/SCCP Call Setup

1. Initial Voice Call2. Switchover3. Fax Media

Voice Media

Once the problem has been narrowed down to a specific stage then

NSE or Protocol-Based Switchover

a specific stage, then the appropriate troubleshooting strategy can be implemented

Fax Media


can be implemented

Packet Captures

Capture mediaand call control

Packet CapturesUnified CM

Capture mediaand calland call control

VoiceGateway

Capturecall control

FaxVoiceGateway

and call control

FaxGatewayIP

Gateway Fax

Packet captures are one of the best tools for troubleshooting fax problems Ideally captures should be made at both endpoints to Ideally captures should be made at both endpoints to

ensure that both signaling and media are seen Cisco Unified Communications Manager only


g yparticipates in the call control signaling

Packet CapturesPacket Captures

Packet capture software such as Wireshark is one of th b t t l f t bl h ti ith NSE


the best tools for troubleshooting either NSE or protocol-based switchovers as well as the fax media

Packet Captures: VoIP Call AnalysisPacket Captures: VoIP Call Analysis

For protocol-based switchovers like fax pass-switchovers like fax passthrough and T.38, the “VoIP Call Analysis” feature in Wireshark offers a graphical means for analyzing themeans for analyzing the switchover

“VoIP Call Analysis” also breaks down the T.38 media stream, showing the T.30 signaling and page transmission

S l “S i i ” f Select “Statistics” from top of Wireshark window, “VoIP Calls”, click on a call, and then click “Graph”


Troubleshooting NSE-Based SwitchoversSwitchovers

debug voip rtp session named-eventJan 10 22:01:58.471: s=DSP d=VoIP payload 0x64 ssrc 0x1EF2 sequence 0x1FBDtimestamp 0x20631C26Jan 10 22:01:58.471: Pt:100 Evt:192 Pkt:00 00 00 <Snd>>>

Jan 10 22:01:58.483: s=VoIP d=DSP payload 0x64 ssrc 0x9A20101 sequence 0x18C2timestamp 0xADA80F0AJan 10 22:01:58.483: <<<Rcv> Pt:100 Evt:192 Pkt:00 00 00

Use the command debug voip rtp session named-event to view NSE-related switchovers and events on IOS gateways, such as fax passthrough and NSE b d T 38NSE-based T.38 Most common cause of problems with NSE-based

switchovers are an incorrect configuration or a


switchovers are an incorrect configuration or a transcoder or proxy in the call path

Packet Captures: NSE SwitchoverPacket Captures: NSE Switchover

The default RTP payload typefor NSE messages is 100

The NSE Event ID is shown in the payload as a hex value. In this case 0xC8 is 200 in decimal (NSE-200), which is a T.38 fax relay switchover request


Troubleshooting PT-Based SwitchoversTroubleshooting PT Based Switchoversdebug voip rtp session named-eventJan 10 16:03:32 838: s=VoIP d=DSP payload 0x60 ssrc 0x0 sequence 0x0Jan 10 16:03:32.838: s=VoIP d=DSP payload 0x60 ssrc 0x0 sequence 0x0timestamp 0x0Jan 10 16:03:32.838: <<<Rcv> Pt:96 Evt:0 Pkt:03 00 02Jan 10 16:03:32.838: s=DSP d=VoIP payload 0x61 ssrc 0xFFEB sequence 0x0p y qtimestamp 0x0Jan 10 16:03:32.838: Pt:97 Evt:0 Pkt:07 00 02 <Snd>>>Jan 10 16:03:32.842: s=DSP d=VoIP payload 0x60 ssrc 0xFFE2 sequence 0x0timestamp 0x0Jan 10 16:03:32.842: Pt:96 Evt:0 Pkt:07 00 02 <Snd>>>Jan 10 16:03:32.842: s=VoIP d=DSP payload 0x61 ssrc 0x0 sequence 0x0 timestamp 0x0Jan 10 16:03:32 842: <<<Rcv> Pt:97 Evt:1 Pkt:B8 01 E0

Like NSE-based switchovers, confirm RTP payload type (PT) switchovers as utilized by Cisco fax relay

i th d d b i t i d

Jan 10 16:03:32.842: <<<Rcv> Pt:97 Evt:1 Pkt:B8 01 E0


using the command debug voip rtp session named-event

Troubleshooting Protocol-Based Switchovers—H.323 and T.38Switchovers H.323 and T.38

H.245 Request Mode message (from the terminating side) Voice

GatewayVoiceGateway( g )

initiates the T.38 switchoverGateway

*Feb 3 04:34:53.070: H245 MSC OUTGOING PDU ::=value MultimediaSystemControlMessage ::= request :

tM d

Gateway

Voice MediarequestMode : <SNIP>

type dataMode : {application t38fax : { as

n1

H 245 R t M d d ACKt38FaxProtocol udp : NULLt38FaxProfile {fillBitRemoval FALSEtranscodingJBIG FALSEtranscodingMMR FALSE bu

g h2

45 H.245 Request Mode and ACK

Closing of G.711 Logical Channels

Opening of T 38 Logical Channels

T.38

gversion 0t38FaxRateManagement transferredTCF : NULLt38FaxUdpOptions {t38FaxMaxBuffer 200t38FaxMaxDatagram 72

deb Opening of T.38 Logical Channels


t38FaxMaxDatagram 72t38FaxUdpEC t38UDPRedundancy : NULL

<SNIP>

Troubleshooting Protocol-Based Switchover—SIP and T.38Switchover SIP and T.38

SIP re-INVITE message (from the terminating side) initiates the Voice

G tVoiceG t

g )switchover to T.38

*Feb 3 22:32:18.514: //-1/xxxxxxxxxxxx/SIP/Msg/ccsipDisplayMsg:Sent:

i 1 2 18 110 86 060 S /2 0

Gateway Gateway

INVITE

INVITE sip:172.18.110.86:5060 SIP/2.0Via: SIP/2.0/UDP 14.1.97.15:5060;branch=z9hG4bK618FFFrom: <sip:[email protected]>;tag=4320068C-1F6B<SNIP>v=0o=CiscoSystemsSIP-GW-UserAgent 8190 1299 IN IP4 14.1.97.15 es

sage

s Voice Media

re-INVITE

ACK

200 OK

s=SIP Callc=IN IP4 14.1.97.15t=0 0m=image 16582 udptl t38c=IN IP4 14.1.97.15a=T38FaxVersion:0 ug

ccs

ipm

ACKa=T38MaxBitRate:14400a=T38FaxFillBitRemoval:0a=T38FaxTranscodingMMR:0a=T38FaxTranscodingJBIG:0a=T38FaxRateManagement:transferredTCFa=T38FaxMaxBuffer:200

debu

T.38


a T38FaxMaxBuffer:200a=T38FaxMaxDatagram:72a=T38FaxUdpEC:t38UDPRedundancy

Troubleshooting Protocol-Based Switchover—MGCP and T.38Switchover MGCP and T.38

A NTFY containingFXR/t38(start) initiates

*Feb 4 17:01:36.597: MGCP Packet sent to 172.18.110.85:2427--->NTFY 935850485 S2/SU0/DS1-0/23@CAE-DH-3845-2 MGCP 0.1FXR/t38(start) initiates

the MGCP T.38 switchover

Unified CM

NTFY 935850485 S2/SU0/DS1 0/23@CAE DH 3845 2 MGCP 0.1N: [email protected]:2427X: 17O: FXR/t38(start)<---

CAE-DH-3845-2#show ccm-manager MGCP Domain Name: CAE-DH-3845-2Priority Status Host==============================================Primary Registered CAE-DH-7845 (172 18 110 85)Primary Registered CAE-DH-7845 (172.18.110.85)First Backup None Second Backup None

Current active Call Manager: 172.18.110.85<SNIP>Voice Media

TIP: Omission of the configuration command mgcp package-capability fxr-package is the most common cause of

VoiceGateway(Sending)

VoiceGateway(Receiving)

T.38


package is the most common cause of MGCP T.38 failing

Troubleshooting Protocol-Based Switchovers With Cisco RTMTSwitchovers With Cisco RTMT

Ci R l Ti M it i T l (RTMT) l i


Cisco Real Time Monitoring Tool (RTMT) log viewer can show protocol-based switchover information

Troubleshooting the Fax/Modem Media: Gateway DSP StatisticsGateway DSP Statistics

CAE-DH-3845-2#terminal monitorCAE-DH-3845-2#show voice call 0/1/10/1/1

t l l 0 t t S CONNECT l l 1 t t FXSLS CONNECTvtsp level 0 state = S_CONNECTvpm level 1 state = FXSLS_CONNECTvpm level 0 state = S_UPcalling number , calling name unavailable, calling time 02/03 04:20CAE-DH-3845-2# ***DSP FAX RELAY STATISTICS***Max Jit Depth: 36, Max Nwk RxQ Depth 3, Jitter Overflow Pkt Drops: 0p , Q p , pNwk RxQ Overflow: 0, Tx Pkts: 247, Tx Pkts Drops(Nwk Busy): 0Rx Pkts: 677, Rx Pkts Loss: 0, Rx Invalid Pkts: 0, Rx Pkts Out Of Seq: 0Recent Hi-Speed Modulation: V.17/long/14400TX Pages: 2Max SendInQ Depth 2, Max RecvOutQ Depth 2Max Hi Speed Buf Usage 54 SendInQ Overflow 0 RecvOutQ Overflow 0

DSP packet statistics on Cisco voice gateways provide IP network information about the active, incoming media stream for fax/modem passthrough Cisco fax relay and T 38

Max Hi-Speed Buf Usage 54, SendInQ Overflow 0, RecvOutQ Overflow 0

fax/modem passthrough, Cisco fax relay, and T.38

Errors in these stats typically indicate packet loss and/or jitter problems


The command “show call active voice brief” also provides some DSP statistics and information about the media stream

Fax Relay Message DebuggingFax Relay Message Debugging

VoiceGateway

fr-msg-detMessage received by DSPFax yg y

fr-msg-tx

IP

The command debug fax relay t30 all-level-1 displays

fr-msg-txMessage transmitted by DSP

The command debug fax relay t30 all level 1 displaysT.30 messages for T.38 and Cisco fax relay from the DSP’s perspective on the POTS/PSTN side of the gatewayga e ay Inbound messages are flagged fr-msg-det and

messages sent by the DSP out the telephony interface are indicated by fr msg tx


are indicated by fr-msg-tx

Sample Output From “debug fax relay t30 all-level-1”debug fax relay t30 all level 1

Nov 2 17:19:22.928: 0/0/0 (42) 626612205 fr-entered=10(ms)

timestamp=626613325 fr-msg-det NSFtimestamp 626613325 fr msg det NSF

timestamp=626614305 fr-msg-det CSI

timestamp=626615005 fr-msg-det DIS

timestamp=626617385 fr msg tx TSI Output from the Ciscotimestamp=626617385 fr-msg-tx TSI

timestamp=626618185 fr-msg-tx DCS

timestamp=626623295 fr-msg-det CFR

Output from the Ciscovoice gateway command:debug fax relay t30 all-level-1

timestamp=626648365 fr-msg-tx EOP

timestamp=626649985 fr-msg-det MCF

timestamp=626652165 fr-msg-tx DCN

This debug is only valid for T.38 and Cisco fax relay as the gateway plays an active role in modulating and

Nov 2 17:20:03.208: 0/0/0 (42) 626652485 fr-end-dcn


the gateway plays an active role in modulating and demodulating the T.30 fax messages

Tips for Using “debug fax relay t30 all-level-1”debug fax relay t30 all level 1

Primary debug used for troubleshooting T.38 and Cisco f l bl Ci i tfax relay problems on a Cisco voice gateway Only low-speed T.30 messages are displayed so high

speed communications such as trainings and page p g p gtransmissions are not shown If there are multiple fax calls occurring at once you can

specify a called or calling number to only view the debugspecify a called or calling number to only view the debug messages for a specific call The “level-2” option for this debug is only readable by

the DSP vendor and it should not be enabledthe DSP vendor and it should not be enabled This debug (as well as packet captures) is useful for

viewing unique T.30 problem signatures


Unique T.30 Debug Signature: DelayUnique T.30 Debug Signature: DelayT.30 Negotiation Failure With a Likely Cause of Too Much

VoiceG t

VoiceG t

IPPSTN

Cause of Too Much Delay Between the Fax Endpoints

Gateway Gateway

NSF/CSI/DIS

fr-entered (10ms)fr-msg-det NSF

DCS (train)

debug faxrelay t30 all-level-1

T.30 messages are not being received before previous messages are retransmitted

Common ca ses of delagfr-msg-det CSIfr-msg-det DISfr-msg-tx DCSfr-msg-det CSI

NSF/CSI/DIS

DCS (train)

Common causes of delay are satellite links or multiple VoIP hops

Adjusting the playout buffer onfr msg det CSIfr-msg-det DISfr-msg-tx DCSfr-msg-det NSFfr-msg-det CSI

NSF/CSI/DIS

DCS (train)

Adjusting the playout buffer on Cisco voice gateways may help

For example, configure playout-delay fax 100 under the


fr-msg-det CSIfr-msg-det DISfr-msg-tx DCS

DCS (train) delay fax 100 under the appropriate dial-peer to lower the playout buffer to 100 ms

Unique T.30 Debug Signature: CorruptionCorruption

IPPSTN

T.30 Negotiation Failure With a Likely C f C t d

VoiceGateway

VoiceGateway

IPPSTN Cause of a Corrupted Training Signal

NSF/DISdebug fax

l t30 ll l l1

FTT

TSI/DCS (train) Fax machine is receiving a

corrupted training signal and sending an FTT message

fr-entered=10(ms)fr-msg-det NSFfr-msg-det DISf t TSI

relay t30 all-level1

FTT

TSI/DCS (train)

g g

Most common cause of a corrupted training is PSTN impairments, such as clock slips

fr-msg-tx TSIfr-msg-tx DCSfr-msg-det FTTfr-msg-tx TSIf t DCS

TSI/DCS (train) First step is to always confirm that any digital circuits are free of errors

fr-msg-tx DCSfr-msg-det FTTfr-msg-tx TSIfr-msg-tx DCSFTT


fr-msg-det FTT

Viewing Digital Circuit ErrorsViewing Digital Circuit Errors

T1 0/1/0 is up.Applique type is Channelized T1

Output from the Ciscovoice gateway command:Applique type is Channelized T1

Cablelength is long gain36 0dbNo alarms detected.alarm-trigger is not setS ki ti 3 Cl ti 10

voice gateway command:show controller t1

Soaking time: 3, Clearance time: 10AIS State:Clear LOS State:Clear LOF State:ClearVersion info Firmware: 20060711, FPGA: 13, spm_count = 0Framing is ESF, Line Code is B8ZS, Clock Source is Line.CRC Threshold is 320. Reported from firmware is 320.Data in current interval (729 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations24 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Minsp , , , g24 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Total Data (last 24 hours)0 Line Code Violations, 0 Path Code Violations,2989 Slip Secs 0 Fr Loss Secs 0 Line Err Secs 0 Degraded Mins


2989 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,2989 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Confirming the Training in T.38Confirming the Training in T.38

The TCF or training signal is a pattern of all 0s Other hex values shown in the TCF decode can cause

the training to fail This training pattern can be checked within Wireshark

to confirm its integrity


to confirm its integrity

Scan Line CorruptionScan Line CorruptionSnippet from a corrupted fax page

In addition to training problems, PSTN errors and impairments can also cause scan lines to become corrupted

Problem will not be viewable with Error Correction Mode (ECM)


Problem will not be viewable with Error Correction Mode (ECM) faxes but instead faxes will take a long time to complete or fail completely

Audio Trace of Scan Line and Training CorruptionTraining Corruption

DCS-train DCN

Page EOP

DIS CFR MCF


Preventing Corruption of the Training and Scan LinesTraining and Scan Lines

Ensure that all digital circuits in the fax path are error free Configure the clocking correctly on Cisco voice

gateways to avoid slips on digital PSTN interfacesgateways to avoid slips on digital PSTN interfaces, which are notorious for causing training and scan line corruptionM k th t th IP th i f f jitt d Make sure that the IP path is free from jitter and packet loss Major corruption problems prevent the faxMajor corruption problems prevent the fax

endpoints from training while less severe problems may allow training to occur but fax page data is affected


Fax Servers


What Is a Fax Server?What Is a Fax Server?

H.323/SIP Call Setup

G 711 Voice

Fax Cisco Voice

G.711 Voice

T.38 Fax

A software application running on a server that

Server Gateway

A software application running on a server that processes fax calls over a PSTN or IP connection

A “Cisco Unified Communications Manager” for ghandling fax traffic

Provides secure, automated, and efficient handling of i ti f t ffi


an organizations fax traffic

Fax Server ComponentsFax Server Components

Server FaxServerHardware

Application Software

FaxEngine

Server hardware requirements are defined by fax server vendors

Application software is produced by a variety of vendors and it handles administration configurationvendors and it handles administration, configuration, and integration functions

Fax engine is either hardware (typically a PCI fax board


Fax engine is either hardware (typically a PCI fax board installed into the server) or software-based

Why Migrate to a Fax Server?Why Migrate to a Fax Server?

Security Faxes can be directed to a specific user or storage system with limited accessg y

Workflow Integration

Fax servers can help automate process management procedures and specific workflow applicationsworkflow applications

ArchivingFaxes can efficiently stored and indexed to comply with industry mandates such as Sarbox or SOx and HIPAA

AccountabilityAll faxes sent or received along with confirmation of their success or failure can be handled with a fax server solution

MFP Integration MFPs integrate directly with fax servers for increased cost savings and flexibility


Email Integration Users have the ability to send/receive faxes directly via email

Fax Server Access MethodsFax Server Access MethodsFaxServer

IP

WebBrowser

API

IPMailServer

ClientSoftwareApplication

MFP

Application

Users can access a fax server through interfaces such as a web browser, email, an MFP, and client software

Other devices and automated processes can communicate


Other devices and automated processes can communicate directly with a fax server through different APIs

Fax Server Integration With Cisco Unified Communications ManagerUnified Communications Manager

Fax Server Unified CM

H.323/SIP

H.323/SIPH.323/SIP

Server

Cisco Voice G t

Fax servers communicate with Cisco Unified Communications Manager using H.323 or SIP

Gateways

Regardless of the call control protocol between the fax server and Cisco Unified Communications Manager, H.323, SIP, or MGCP can be used between Cisco Unified Communications Manager and the gateway


g y

T.38 media flows between the fax server and the voice gateways

Integrating a Fax Server with a SIP TrunkTrunk

T.38 fax relay is the best choice for sending faxes over SIP trunks

No special modifications or configurations are typically necessary on a fax server to utilize SIP trunks, especially when a border element is presentwhen a border element is present


Cisco Fax Server: Centralized SolutionCisco Fax Server: Centralized SolutionFax Server

Fax Client

Email ClientFax

VoiceGatewayy

Unified CM MFP

Cisco fax server is the Open Text Fax Server (RightFax) application on a Cisco MCS server

A full featured, scalable enterprise solution that is centralized and supports both hardware and software-based fax engines to handle various integration solutions


Deployed internally by Cisco in conjunction with Multifunction Peripherals (MFPs)

AXP-XMediusFAX: Branch SolutionAXP XMediusFAX: Branch Solution

Branches typically have little IT infrastructure and yp ystaff to maintain server and application hardware

Integrate fax server directly into the local ISR tgateway


Cisco AXP: XmediusFAX SolutionCisco AXP: XmediusFAX Solution

XMediusFAXAPPREModuleAXP XMediusFAX

Cisco ISR GatewayModule

XmediusFAX server on an ISR blade

AXP runs a hardened Linux OS and provides a virtualized hosting environment

XmediusFAX integrates directly with ISR architecture and is able g yto be configured and managed through the IOS CLI

Functionality of a standalone fax server with no footprint

Add th d f ffi i tl h dli f t ffi t th l l


Addresses the need for efficiently handling fax traffic at the local branch level

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