L.2 FoIP support in MTSI clients
26.1143GPPIP Multimedia Subsystem (IMS)Media handling and interactionMultimedia telephonyRelease 18TS
L.2.1 FoIP support in MTSI client in terminal
An MTSI client in terminal supporting FoIP is typically either a facsimile gateway or a facsimile end-point and does not need to support both cases.
An MTSI client in terminal may support FoIP where the MTSI client in terminal is used as a facsimile gateway between an external Group 3 facsimile equipment and the IMS network. In this case, the MTSI client in terminal acts as an Internet Facsimile Protocol (IFP) peer, either as an emitting gateway or as a receiving gateway depending on whether the MTSI client in terminal initiates the Internet Facsimile Transfer (IFT) or whether it accepts the IFT, [93].
An MTSI client in terminal may support FoIP where the MTSI client in terminal is the end-point for the facsimile transmission. In this case, the facsimile transmission originates or terminates in the MTSI client in terminal.
An MTSI client in terminal supporting FoIP and used as a facsimile gateway shall support:
– input/output to Group 3 facsimile devices, [91]
NOTE: The interface used to connect the external facsimile device to the MTSI client in terminal is outside the scope of this specification.
An MTSI client in terminal supporting FoIP and used either as a facsimile gateway or as a facsimile end-point should support the recommended configuration defined in Clause L2.3, Table L.1.
– encapsulating and decapsulating T.30 to/from Internet Facsimile Protocol (IFP) packets, [93];
L.2.2 FoIP support in MTSI MGW
An MTSI MGW may support FoIP where the MGW is used as a facsimile gateway between the IMS network and a Circuit Switched (CS) network, e.g. PSTN or CS GERAN, in order to connect to another Group 3 facsimile device.
An MTSI MGW supporting FoIP should support the recommended configuration defined in Clause L2.3, Table L.1.
L.2.3 Recommended configuration
The recommended configuration for T.38 UDPTL-based FoIP is defined in Table L.1.
Table L.1: Recommended configuration for T.38 UDPTL-based FoIP
|
SDP attributes |
Value |
|
|
T38FaxVersion |
2 (or higher) (NOTE 1) |
|
|
T38MaxBitRate |
14400 bps |
|
|
T38FillBitRemoval |
N/A (NOTE 2) |
|
|
T38FaxTranscodingMMR |
N/A (NOTE 2) |
|
|
T38FaxTranscodingJBIG |
N/A (NOTE 2) |
|
|
T38FaxRateManagement |
‘transferredTCF’ |
|
|
T38FaxMaxBuffer |
1800 bytes |
|
|
T38FaxMaxDatagram |
At least150 bytes |
|
|
T38FaxMaxIFP |
40 bytes (NOTE 3) |
|
|
T38FaxUdpEC |
‘t38UDPRedundancy’ |
|
|
T38FaxUdpECDepth |
‘minred:1’, ‘maxred:2’ (NOTE 3) |
|
|
T38FaxUdpFECMaxSpan |
3 (NOTE 3) |
|
|
T38ModemType |
‘t38G3FaxOnly’ (NOTE 3) |
|
|
NOTE 1: Some SDP attributes listed here apply only to newer versions NOTE 2: Support not required NOTE 3: Only applicable when fax version 4 is supported NOTE 4: See ITU-T T.38, Annex D, Table D.1 for a complete description |
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It is recommended that the MTSI client supports sending and receiving facsimile with 200% redundancy when UDP redundancy is used, even if the SDP attributes and parameters (‘T38FaxUdpECDepth’ with ‘minred’ and ‘’maxred’) are not supported. This allows for transmitting each IFP message three times, once as a primary message and twice as redundancy messages.