How to set gzip in soap xml message

I need to set gzip compression on my xml request so the request will be compressed and response will be compressed as well. My XML request is given bellow

<?xml version="1.0" encoding="UTF-8"?>
    <soapenv:Envelope xmlns:soapenv="http://ift.tt/sVJIaE" xmlns:tbx="http://ift.tt/1DWusgJ" xmlns:ota="http://api.bb.net/ota">
       <soapenv:Header/>
       <soapenv:Body>
          <aa:OTA_AuthTokenRQ>
             <aa:AuthTokenType>Request</aa:AuthTokenType>
              <aa:AuthTokenCredentials UserName="TEST" Password="TEST123"/> 
          </aa:OTA_AuthTokenRQ>
       </soapenv:Body>
    </soapenv:Envelope>

Someone please tell me where and how to enable gzip from this request?