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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
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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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 4
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
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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
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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
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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
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2. Relay
Transporting G3 Fax Protocols Over IPTransporting G3 Fax Protocols Over IP
T.4/T.6—Specifies the Fax Page Encoding Algorithm
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?
T.4/T.6—Specifies the Fax Page Encoding Algorithm
Passthrough or RelayTransport
IP
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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
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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
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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
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presentation
Fax/Modem Media
Fax Transport Methods
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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
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( ) (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
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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
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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
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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
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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
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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
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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
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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
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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
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Fax Passthrough Call
nse buf:0/0 loss 0% 0/0 last 1359s dur:0/0s
Fax Passthrough Call
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
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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
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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
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Fax Passthrough Call
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
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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
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( ) (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
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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
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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
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Cisco Fax Relay Callg
Confirming Cisco Fax Relay SwitchoverConfirming Cisco Fax Relay Switchover
Before Switchover: show call active voice brief
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
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
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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.
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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
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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
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TGW: T.38 ACK received, start T.38 session
T.38 Switchover—H.323 (G3)T.38 Switchover H.323 (G3)TGWOGW
Th i iti l V IP ll i
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 36
T.38 Fax Relay Callsame events by the other side
T.38 Switchover—SIP (G3)T.38 Switchover SIP (G3)TGWOGW
Th i iti l V IP ll i
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
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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
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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
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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
Before Switchover: show call active voice brief
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
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 40
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.
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 41
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 42
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 43
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 44
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 45
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 46
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 47
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 48
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 49
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 50
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 51
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 52
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 53
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 54
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
IPFax Gateway FaxGateway
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 55
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 56
p y q p
Cisco Unified Communications Manager, CA-ControlledManager, CA Controlled
Unified CM
IPFax Gateway FaxGateway
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 57
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 58
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 59
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 60
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 61
( 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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 62
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 63
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 64
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 65
*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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 66
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 67
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 68
T.38 Should Always Be Your First Choice When Handling FoIP Traffic!
Troubleshooting
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 69
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 70
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 71
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 72
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”
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 73
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 74
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 75
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 76
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 77
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:100@14.1.97.15>;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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 78
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: ca@172.18.110.85:2427X: 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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 79
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 80
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 81
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 82
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 83
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 84
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 85
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 86
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 87
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 88
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)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 89
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 90
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 91
Fax Servers
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 92
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 93
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 94
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 95
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 96
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 97
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 98
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 99
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 100
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
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 101
Addresses the need for efficiently handling fax traffic at the local branch level
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