title: Confused about the header size for a Ethernet frame
body: <p>I was researching a few things about <code>VLANs</code> and came across the <code>VLAN tag</code> and also the headers.</p>
  
  <p>If we have a MTU for a standard <code>802.3 Ethernet frame</code> (1518 bytes) what is included in the header <code>802.3</code>? </p>
  
  <p>Also how do we calculate the header length for that?</p>
  
  <p>What is the difference between <code>802.3 and 802.1q</code>? I know that the VLAN tag requires extra bytes but how to calculate how many bytes needed to the <code>802.1q VLAN tag</code>?</p>
  
  <p>Thanks in advance</p>