EchoToken, Timestamp and POS

<OTA_ReadRQ xmlns="http://www.opentravel.org/OTA/2003/05" Version="1.0" TimeStamp="2005-08-01T09:30:47+08:00" EchoToken="echo-abc123">
  <POS>
    <Source>
      <RequestorID Type="22" ID="PMS1"/>
    </Source>
  </POS>
  <ReadRequests>
    <HotelReadRequest HotelCode="ABC">
      <SelectionCriteria SelectionType="Undelivered" ResStatus="Book"/>
    </HotelReadRequest>
  </ReadRequests>
</OTA_ReadRQ>
<OTA_ResRetrieveRS xmlns="http://www.opentravel.org/OTA/2003/05" Version="1.0" TimeStamp="2005-08-01T09:31:00+08:00" EchoToken="echo-abc123">
  <Success/>
</OTA_ResRetreiveRS>

POS

All incoming messages except the OTA_NotifReportRQ are expected to contain a POS element with a RequestorID identifying the sending PMS.

EchoToken

All incoming messages are expected to contain a unique identifier, an EchoToken. This token will be returned in the response. It's recommended that you implement UUIDs - https://en.wikipedia.org/wiki/Universally_unique_identifier

Timestamps

As of PmsXchange v2, all timestamps will be qualified with a Timezone. All timestamps will be in GMT+0 time.

The GMT timezone does not apply to the dates provided for checkin/checkout, and daily rates. These are reported as provided by the original channel