Fax over IP (FoIP)

SIP along w/ SDP being the signalling to control Fax sessions is a TCP/IP layer?

Application

What's Pass-through protocol in VoIP?

G.711 (like VoIP calls), uses RTP encapsulate fax & transport. If fax needs to go across the PSTN the fax will be converted to T.30

Fax boards on fax server allow a fax server to connect to?

PSTN.

What does UDPTL stand for?

UDP Transport Layer

T.38 (T.30) utilizes another protocol at TCP/IP application layer is?

UDPTL

What are points on T.37?

1. AKA 'Store & Forward' 2. Uses SMTP protocol 3. Needs Fax/Email servers 4. Fax's can't negotiate ( no capabilities) 5. Fax's can't deliver a receipt 6. Not Real Time ( fax may be delay in Fax/Email server).

What are points on T.38?

1. Defacto Standard for Real Time fax. 2. Methods to replace lost packets. 3. Delivery receipt 4. Can 'failover' to another connection. 5. Less bandwidth hungry - defined by ITU. 6. RFC 3362 - describes T.38 over UDPTL 7. RFC 4612 - describes T.38 over RTP.

What are points on G.711 for faxing?

1. Real Time 2. Uses RTP & RTCP 3. Faster than T.38 when G3 V.34 is utilized 4. Fax transmission can be affected by Delay, Jitter & Packet loss. 5. Bandwidth hungry 6. Can't use 'compression' codecs 7. Can use SRTP

Fax servers are used to?

1. Replace a bunch of fax machine. 2. People can fax from their PC.

T.38 is the defacto to transmit fax. What can be seen in the UDPTL packet?

1. Sequence number 2. T.30 fax information (i.e V.29 emulated protocol) 3. Digital version of fax 4. Secondary packet of previous packet for error correction - If packet is lost, data is provided here for recovery.

What are the 3 IP protocols for FoIP?

1. T.37 2. Pass-through 3. T.38

If a fax is converted multiple times i.e T.30 to T.38 to T.30 to T.38 to T.30. This can cause?

Delay of transmission of T.30 signaling & Fax data.

If you have an existing TDM line for fax in a VoIP infrastructure w/ SIP trunks. What can be used to convert the TDM line to T.38 to send the fax document over IP?

Gateway.

What's T.38 fax relay mode?

Gateways break down the T.30 tones into frames & send them across the IP network using T.38. Effect is Fax machines are unaware that the signals have be converted.

What does IFP stand for?

Internet Fax Protocol - i.e T.38

What is On-ramp gateway in T.37?

Receiving fax

What's T.37?

Specifies how fax documents can be encapsulated (T.30 to TIFF) & sent as an email. Gateway will convert from T.30 to TIFF then sends as an email. T.38 & PSTN (T.30) trunks can be converted too.

Fax Server is using FoIP w/ SIP trunks. The fax document is transmitted using what protocol?

T.38

Fax servers that can implement FoIP & sends all faxes to the IP PBX. Fax documents can then be?

Transmitted over the TDM link - Need to ensure existing lines & IP PBX can cope w/ added traffic.