P_TXMODE

code: 320

# set
<module-index>/<port-index> P_TXMODE <mode>

# get
<module-index>/<port-index> P_TXMODE ?

Description

The scheduling mode for outgoing traffic from the port, specifying how multiple logical streams are merged onto one physical port.

There are four port transmission modes:

  • Normal Interleaved (default): The streams are treated independently, and are merged into a combined traffic pattern for the port, which honors each stream’s ideal packet placements as well as possible.

  • Strict Uniform: This is a slight variation of normal interleaved scheduling, which emphasizes strict uniformity of the inter-packet-gaps as more important than hitting the stream rates absolutely precisely.

  • Sequential: Each stream in turn contribute one or more packets, before continuing to the next stream, in a cyclical pattern. The count of packets for each stream is obtained from the P_TXPACKETLIMIT command value for the stream. The individual rates for each stream are ignored, and instead the overall rate is determined at the port-level. This in turn determines the rates for each stream, taking into account their packet lengths and counts. The maximum number of packets in a cycle (i.e. the sum of PS_PACKETLIMIT for all enabled streams) is 500. If the packet number is larger than 500, will be returned when attempting to start the traffic (P_TRAFFIC).

  • Burst: When this mode is selected, frames from the streams on a port are sent as bursts as depicted below:

    The Burst Period is defined in the P_TXBURSTPERIOD command. For the individual streams the number of packets in a burst is defined by the PS_BURST command, while the Inter Packet Gap and the Inter Burst Gap are defined by the PS_BURSTGAP command.

../../../../_images/burst_mode.png

Fig. 3.3 Port TX Burst Mode

Actions

set, get

Parameters

  1. mode: byte, the scheduling mode for outgoing traffic from the port, containing the loopback mode for the port:

  • NORMAL = 0, interleaved packet scheduling (default).

  • STRICTUNIFORM = 1, strict uniform mode.

  • SEQUENTIAL = 2, sequential packet scheduling.

  • BURST = 3, burst mode.

Example

# set
input:  0/1 P_TXMODE NORMAL
output: <OK>

# get
input:  0/1 P_TXMODE ?
output: 0/1 P_TXMODE NORMAL