Checking If Configuring Fax to Use ECM Mode

User Manual - Configuration Guide (Volume 3)	Chapter 2
Versatile Routing Platform	IP Fax Configuration

IP telephone works after VoIP is configured. Generally speaking, faxes can now be sent and received by using the default configuration of IP Fax only after a facsimile machine is connected. The procedures of configuring IP Fax are mainly used to set up the specific parameters of IP Fax or used for some specified conditions. For example, fax operation can not be completed when the default gateway carrier transmit energy level.

The task of IP Fax configuration is as follows:

zCheck if configuring fax to use ECM mode

zConfigure fax rate

zConfigure fax train mode

zConfigure Fax Local-train Threshold Value

zConfigure gateway carrier transmit energy level

zConfigure redundancy packet number of T38 fax protocol

zConfigure the fax protocol intercommunicating with Cisco equipment

zConfigure the intercommunication method with other equipment

All of the above configuration tasks should be carried out under the condition of dial peer entity configuration mode.

2.2.2 Checking If Configuring Fax to Use ECM Mode

According to ITU-T Recommendation, Error Correction Mode (ECM) is necessary to the transmission of facsimile message with the half-duplex and half-modulation system of ITU-T V.34 protocol, at the same time the category G3# facsimile terminal operating in full duplex mode is required to support half-duplex mode, that is to support ECM mode.

If the facsimile adopts ECM mode, it has error correction function, and provides automatic request for retransmission (ARQ) technology, at the same time facsimile packet will be transmitted in the form of HDLC frame. On the contrary, if the facsimile machine adopts non-ECM mode (the mode that facsimile must support), it has no error correction function, and the facsimile uses binary string to transmit.

In actual configuration, if the facsimile machines on both sides support ECM mode, but the configuration on the side of gateway is non-ECM mode, then non-ECM mode should be adopted. If the facsimile machine on either or neither of sides does not support ECM mode, then non-ECM mode should also be used. Only when the facsimile machines on both sides support ECM mode and the gateway uses ECM mode, ECM mode can be adopted.

Please perform the following configuration in dial peer configuration mode.

Table VC-2-1Check if configuring fax to use ECM mode

Operation	Command

Configuring fax does not use ECM mode	fax-relay ecm disable
Configuring fax uses ECM mode	no fax-relay ecm disable

The gateway does not use ECM mode by default.

2.2.3 Configuring Fax Rate

Subscribers can configure fax rate according to the different protocols.

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