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The following parameters control V.150.1 in VX 4.7.0 and higher.

Note: To accept default values for the following VXbuilder V.150.1 parameters, click Set to Default. To enter non-default values enter -1 for a parameter and click OK to display the legal range for that parameter.

Category

Parameter

Description

General

Modem Relay - Preferred

Used for configuring VX to work with Modem Relay Preferred (MRP) devices.

  • No means no MRP devices are allowed.
  • Only means only MRP devices are allowed. Clear call would not be allowed in this setting.
  • Allowed means MRP devices are allowed

 

TDM: retrain/renegotiation enable

This setting is used for rate matching.

  • Yes means retrain/renegotiation will be initiated if rate matching is needed.
  • No will not initiate retrain/renegotiation for rate matching. Note: Line quality will initiate retrain/renegotiation regardless of the setting.

 

TDM: V.8 enable

Enables V.8 procedure. Specify Yes if V.34 is enabled.

 

TDM: V.8 IP device on cellular connection

Yes makes IP side of devices look like they are on a cellular connection.

 

TDM: V.34 enable

Set to Yes for V.34.
Note V.8 has to be enabled for V.34.

 

TDM: V.34 maximum rate(bps)

Specifies the maximum rate that V.34 Modem may use.

 

TDM: V.32bis enable

Set to Yes for V.32bis.

 

TDM: V.32bis maximum rate(bps)

Specifies the maximum rate that V.32bis Modem may use.

 

TDM: V.32 enable

Set to Yes for V.32.

 

TDM: V.32 maximum rate(bps)

The maximum rate that V.32 Modem may use.

Note: When VX initiates a Modem session, it will try a Modem from V.34 to V.32bis and V.32 if they are all enabled. The highest configured rate will be attempted. The resulting rate is determined by time negotiation between the VX Modem and peer Modem.

 

SSE: reliable method

Preferred SSE reliability method. The run time result is determined by the local configuration and negotiation with the peer in SDP. The following four parameters are used for the Simple Repetition method.

 

SSE: repetition interval(ms)

Packet interval of repeated SSE packets sent out Ns times.

 

SSE: repetition count

Number of SSE repeated packets sent including the first one.

 

SSE: transient interval T2 (ms)

Timer for inconsistency condition. The timeout will trigger setup of T1 and Nr.

 

SSE: recovery transient interval T1 (ms)

Duration of one recovery cycle.

 

SSE: recovery repetition count Nr

Number of recovery cycles.

Note: T2 should be the IP side round trip delay (RTD) plus a margin. Use 1.5*RTD under normal conditions. Increase the margin for networks with more RTD fluctuation. Estimate RTD by the result of pings and LQM.
One second is recommended for T1. The total period of retries should cover RTD, i.e. T1*Nr > RTD.
Maximum recovery period is T2 + T1*Nr.

 

SPRT: Double-Double Trans-Compression announcement

Specify Yes to let IP devices disable error correction and data compression

 

SPRT: payload/window size negotiation

Yes allows VX to initiate the negotiation of maximum payload size and window size with configured values of maximum payload size and window size.

No means VX will not initiate the negotiation. However, if the peer IP device initiates negotiation, VX will respond with a consideration of the configured values of maximum payload size and window size regardless the configuration.

 

SPRT: channel preference

Indicating which transport channel will be used. Default is Unreliable, i.e. TC3. Reliable means TC1.

 

SPRT: data type I*OCTET-CS support

Indicates whether I*OCTET-CS is enabled. Default is No, meaning only I*OCTET is enabled.

 

SPRT: TC1 - ACK timer TA01(ms)

ACK timer.

 

SPRT: TC1 - ACK update timer TA02(ms)

ACK update timer. Used for BSN update.

 

SPRT: TC1 - retransmission timer TR03(ms)

Retransmit timer if no ACK received.

 

SPRT: TC1 - number of retransmission

Number of retransmission on TR03 timeout.

Note: In the case of consecutive packets lost caused by the network, use a larger value.

 

SPRT: TC1 - maximum payload size(bytes)

Maximum number of bytes in one packet.

 

SPRT: TC1 - maximum window size(packets)

Maximum number of packets in one window

 

SPRT: TC1 - Tx flush timer(ms)

Maximum time data from the TDM side stays in the Modem.

Note: When a modem receives data, if the maximum payload size is reached, the data is packed in one packet. If the maximum payload size is not reached when flush timer is fired, the data is packed into one packet. So one data byte is guaranteed to have a maximum delay in the Modem for this timer amount of time. The smaller the timer value, the shorter a packet stays in the Modem. However, the smaller the value also means possible a smaller packet size.

Packet size is also determined by the data rate. For example, data rate 9600bps (960byte/s) with a flush timer of 40ms will make the packet size 0.96*40 = 38.4 bytes. 28800bps with 40ms flush timer will make the packet size 2.88*40 = 115 bytes. The smaller the flush timer, the smaller the packet size, and the bandwidth efficiency decreases.

Users may choose a larger flush timer to achieve maximum payload size and bandwidth efficiency. For example, in order to achieve a maximum payload size of 140 bytes in rate 28800bps, the flush timer has to be at least 50ms. For a rate of 9600bps, the flush timer should be at least 150ms. For the lowest rate of 4800bps, the flush timer needs to be 300ms.
Also, the maximum window size is related to the flush timer. The smaller the flush timer, the quicker the maximum window size will be reached. If the peer does not consume data quickly enough, the flush timer should be increased.

A larger TA01 and TA02 will increase bandwidth efficiency because ACKs have more chances to piggy-back on data packets. However, larger values will increase the number of packets being buffered on the sending side, resulting in a longer delay.

TR03 should be bigger than RTD + TC1 + the margin for processing. This is important for network with a large RTD.
In general, all of the above parameters in SPRT and IP network RTD are related. Careful planning is important.

 

SPRT: TC2 - ACK timer TA01(ms)

ACK timer.

 

SPRT: TC2 - ACK update timer TA02(ms)

ACK update timer. It is for BSN update.

 

SPRT: TC2 - retransmission timer TR03(ms)

Retransmit timer if no ACK received.

 

SPRT: TC2 - number of retransmission

Number of retransmission on TR03 timeout.

 

SPRT: TC2 - maximum payload size(bytes)

Maximum number of bytes in one packet.

 

SPRT: TC2 - maximum window size(packets)

Maximum number of packets in one window

 

SPRT: TC3 - maximum payload size(bytes)

Maximum number of bytes in one packet.

 

SPRT: TC3 - Tx flush timer(ms

Maximum time data from the TDM side stays in the Modem.

Note: considerations are similar to those for TC1 except TC3 does not have a maximum window size.

STIX feature card

PayloadFeature UMR

Must be enabled. VX node must have sufficient licensees for UMR.

Media Class


Must refer to a V.150.1 profile.

Trunk Group/Call Route


Must refer to correct Media Class.