| Field | Size in bits | 
|---|---|
| Ver—Internet Protocol version number, with a value of 6 | 4 | 
| DS byte—Traffic class field, similar to Type of Service in IPv4 | 8 | 
| Flow label—identifies traffic flow for additional Quality of Service (QoS) | 20 | 
| Payload Length—Unsigned integer, the length of the IPv6 payload | 16 | 
| Next header selector—identifies the next header | 8 | 
| Hop limit unsigned integer—decrements by 1 each time a node forwards the packet (nodes discard packets with hop limit values of 0) | 8 | 
| Source address | 128 | 
| Destination address | 128 | 
The following figure illustrates the basic IPv6 header, without extension headers.

