Commetrex Corporation

Mike CoffeeCEO, Commetrex

SIP Forum FoIP Task Groupmcoffee@commetrex.com

“What About Fax?”UC-SIP Trunking Summit

FoIP Session11:00 AM 02/03/11

Commetrex Corporation

Timing is everything.

In Fax…

http://www.commetrex.com 3

Fax Relay

PacketNetwork

ReceivingFaxTransmitting

Fax

Real-TimePacket-Based

Fax

EmittingGateway

ReceivingGateway

PSTNPSTN

T.38

T.30

IP-Carrier-Based Voice

• Voice is generally the default

• Agree on a codec

• Enable the media stream

• Take care of jitter-buffer management

• Get rid of echo

• You’re done!

Fax: What’s the Problem?

• Fax involves a computer-to-computer protocol (T.30) w/ timing requirements

• Fax involves synchronous modems(not just a different “codec”)

• For T.38, codec/media must be renegotiated with SIP

• Timing is everything!

http://www.commetrex.com 6

Dropped Sample (frequency domain)

The Challenge:

• Calls don’t begin as a fax call.

• Can we agree on how the transaction is to proceed:• G.711 pass-through fax

• T.38

• Can we switch in time?

• Can we meet the timing requirements in session setup?

T.38 Deployment Phases:

• Phase I: 1998-2008

• Phase II: 2008-2018

• Phase III: 2011-2021

Intra-Enterprise

PSTNEnterprise LAN

EnterpriseGateway

FoIP FaxServer

Fax Terminal

ATA

T.38 Phase I

And Now…The Carriers!

ILEC

ITSP

XO

GlobalCrossing

Level(3)

Enterprise LAN

FoIP FaxServer

Fax Terminal

ATA

T.38 Phase II

Router

Fax Terminal

Service Provider Questions

• VoIP? CLEC? ILEC?

• SIP trunking or direct peer?

• T.38 availability? Routing?

• G.711 pass-through support required?

• NAT/firewall solution?

Qualifying a Service Provider

• Is your service provider experienced?

• What carriers will be involved?

• Do they support T.38?

• What is their footprint?

• What about NAT?

• What about support?

Problems:

• Slow SIP leads to T.38 re-Invite failures

• G.711 pass-thru PCM clock sync failures

• V.34-SIP integration is complex

In a Recent Broadcast Test

200 out of 2000 callshad late-arriving T.38 re-Invites.

The Problem

CED

OK T.38Invite

CNGDCS

DIS

RTP Flows here

Sessionresetshere

The Problem

http://www.commetrex.com

CallingTerminal

On-RampGateway

Off-RampGateway

CalledTerminal

PSTNCall

SIP InviteG.711

PSTN Call

CED

SIP183 Ringing

SIPT.38

Re-Invite

G.711-T.38 Re-Invitewith Current Technology

SIP100 Trying

G.711 RTP

SIP200 OK

ACK

G.711

CNG

DIS

V21 Flags

G711 (DIS)

V21 flags

DIS

V21 Fl;ags

DCS

V21 Fl;ags

DCS

V21 Fl;ags

DCS

SIP T.38ACK

TCFTCF

TCF

T.38 Re-Invitedelayed, for example,

by multipletandem

networks.

Acceptance of T.38 Re-Invite

causes TCF to fail &the calling T.30

to initialize.

The off-ramp gateway should send the T.38 Re-invite somewhere

in here.

Operational Modes

• Called GW, V34 fax supported

• Called GW, V34 fax not supported

• Calling GW, V34 fax supported

• Calling GW, V34 fax not supported

Phase II Problems:

What’s being done to fixthe Phase II problems?

G.711 Clock Sync

• One second of silence begins here.

• EVT_IP_RESET

Calling GW w/ V.34

IDLE

Pass_CED

PASS_ANSam

IPCED

STARTED

CMD_START

IPANSam

CMD_STO P

SUPPRESS DIS

IPFlags

CMD_STO P

IPCNG

PSTNCNG W T_DIS2

V.21 End

CMD_STO P

PASS_G711

IP_FLAGS

CMD_STO P

CMD_STO P

CMD_STO P

IPFlags

PSTNFax CM

SEND_CM

CM_LIMIT

CMD_STO P

IPFlags

PSTNnon-FAX CM

PSTNCNG

PSTNVOICE

CEDTim eout

IPFlags

SIP Forum

Copyright © 2010 SIP Forum

FoIP Task Group

Copyright © 2010 SIP Forum

SIP Forum Background

• Founded in 2000 in Sweden

• Leading non-profit IP communications industry association

• Individual, corporate, and academic members

FoIP Task Group Charter

SIP networks cannot fully replace analog PSTN unless essential services, such as fax, are provided.

Investigate and resolve problems with the deployment of fax services, specifically ITU-T T.38, in SIP networks.

SIP Forum & FoIP Task Group Leadership

• SIP Forum Leadership:• Eric Burger, CTO, NeuStar• Marc Robins, Managing Director and President,

SIP Forum LLC• Richard Shockey, Chairman of the Board

• Task Group Leadership:• Mike Coffee, CEO, Commetrex, Co-Chair• Gonzalo Salguiero, Cisco, Co-Chair• Max Schroeder, VP, Faxcore, Task Group

Whip Copyright © 2010 SIP Forum

Task Group Goal

Copyright © 2010 SIP Forum

Develop and publish the guidelines (recommended practices) that will reduce the implementation problems that are today hindering IP-based fax deployments in carrier-based applications.

FoIP Task Group Problem Statement

Copyright © 2010 SIP Forum

Due to increasing carrier support of T.38, barriers to its effective use are moving from the simple case of interop between two T.38 peers within the enterprise to effective SIP-based call setup among multiple network elements in addition to the two T.38 SIP peers, demanding strong cooperation between equipment vendors and carriers.

Results to Date:

• SIP Forum – Official Fax Over IP Task Group Problem Statement:• http://www.sipforum.org/component/option,com_docman/

task,doc_download/gid,372/Itemid,261/

• ITU-T SG16-V.153 Recommendations for Consent:• http://www.sipforum.org/component/option,com_docman/

task,doc_download/gid,366/Itemid,261/

• T.38 SIP-SDP Negotiation Subgroup Problem Statement:• http://www.sipforum.org/component/option,com_docman/

task,doc_download/gid,412/Itemid,261/ Copyright © 2010 SIP Forum

Next for the Task Group:

FoIP must become a robust transport in a global, multinational

IP infrastructure.

Fix it

Copyright © 2010 SIP Forum

But to begin, we must measure it.

SIP Forum FoIP Task Group & The i3 Forum

Copyright © 2010 SIP Forum

Reliable IP-based real-time fax can only be achieved with effective cooperation between vendors (SIP Forum) and carriers (i3 Forum).

Objectives:

• Quantify the problem

• Catalog unsuccessful FoIP calls

• Statistical analysis of failures

• Discover relation between successful call rate and delay before re-INVITE to T.38 and the record the route

• Determine T.38 re-Invite best practices (re: SIP Forum SDP document)

• Validate proposals with retest

Participants to date:

• Deutsche Telekom

• iBasis

• SFT

• OTEGLOBE

• TATA

• Telkom SA

• Telekom Italia Sparkle

• Telecom Poland

• Telefonica

• Reach

• ATT

• Telenor

Schedule:

1. Installation: Sept-Dec

2.Testing: 1Q11

3.Collection/analysis: Q2

4.Recommendations: Q3

5.Follow-up testing: Q4

6.Final report: Q4/1Q12

Thank you