H.323 and SIP call transport segments can be deployed for a single call path. Each time the call traverses from one technology to the other, a pair of transcoding is generated. H.323 and SIP in a fax call path can work if one of the end devices is a fax server that integrates using IP. Keep the number of transcoding nodes to three or fewer to keep the delay to an acceptable level.

The T.38 FAX sending and receiving endpoints can be on port networks or gateways registered to the same server. In such cases, the gateways or port networks revert to Avaya FAX relay mode.

The sending and receiving systems must announce the support of T.38 FAX data applications. Support for T.38 FAX data applications must be announced during the H.245 capabilities exchange for H.323 trunks or the SDP media description for SIP trunks. Avaya systems announce support of T.38 FAX if the capability is administered on the Codec Set screen for the region. Also, a T.38-capable media processor must be chosen for the voice channel. In addition, for a successful FAX transmission, both systems must support the H.245 null capability exchange to avoid multiple IP hops in the connection.

If you experience a packet network loss, assign packet redundancy to T.38 standard faxes to improve packet delivery and robustness of FAX transport over the network.

T.38 FAX Standard supports Error Correction Mode (ECM). With ECM, a FAX page is transmitted in a series of blocks that contain frames with packets of data.

After receiving the data for a complete page, a receiving fax machine notifies the transmitting fax machine of any frames with errors. The transmitting fax machine then retransmits the specified frames. This process is repeated until all frames are received without errors. If the receiving fax machine is unable to receive an error-free page, the fax transmission can fail and one of the fax machines can disconnect. too much content for a table. Create a separate concept topic and link.