title: Is initialization vector part of Output ESP packet in IPsec?
body: <p><a href="https://i.stack.imgur.com/EGVkD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EGVkD.png" alt="ESP Packet showing initialization vector as part of output packet" /></a></p>
  <p>Encryption Algorithm: AES-CBC
  Authentication Algorithm: HMAC-SHA1-96</p>
  <p>Is it necessary that in ESP, initialization vector be always the part of output packet.
  If no, what are those algorithms ?
  If yes, Why in some of the images on google/books show esp packet with no iv field ?
  <a href="https://i.stack.imgur.com/HdMI7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HdMI7.png" alt="ESP PACKET FORMAT" /></a></p>