As shown in figure 1 and figure 2, the head length (IHL), identification, flag, fragment offset, header checksum, and padding have been removed from the IPv6 header.
 

As shown in Figure 1, the IPv4 header has a checksum, which must be computed by each router. It can be seen from Figure 2 that IPv6 has no header checksum because checksums are, for example, above the TCP/IP protocol suite, and above the Token Ring, Ethernet, etc. Removing the checksums allowed the systems to speed up forwarding the datagrams [6]. This reduces the end-to-end delay.
 

A flow is the set of packets sent from one source to one or more receivers. The two new fields in the IPv6 header are: the flow label and the priority. The flow label (20 bits in length) is a new feature added to IPv6 to identify packets that need special treatment by IPv6 routers. For example, it informs the router about the amount of latency needed for video or audio streaming. In IPv6, flow labels distinguish the traffic flow in order to optimize routing. The priority field is used to distinguish the datagram from other datagrams. The priority field performs priorities for two types of traffic: congestion, and non-congestion control traffic. Non-congestion control traffic includes delay applications [6].
 

As shown in Figure 2, the IPv6 header contains a 8-bit field called the Traffic Class Field. This field allows the traffic source to identify the desired delivery priority of its packets. The 4 bits in the priority field are divided into two ranges. Values 0 through 7 specify the priority of traffic for which the source is providing congestion control, values 8 through 15 specify the priority of traffic that does not respond to congestion situations, such as real-time traffic being sent at a constant rate.
 

As shown in Figure1, IPv4 contains an 8-bit field called “Service Type”. The Service Type field is composed of a ToS (Type of Service) field and a procedure field. The ToS field specifies the type of service and contains cost, reliability, throughput, delay or security. The procedure field specifies the level of priority using eight levels from 0 to 7.
 

 

 

2.2 Autoconfiguration

 

The IPv6 node has the ability of attaining dynamically its node and network address. This ability is called Autocongifuration. There are two types of autoconfiguration: stateful and stateless autoconfiguration [6].
 

Stateful autocofiguration: Both IPv6 and IPv4 use the stateful autoconfiguration. This method uses external devices to help the node in start-up to determine its network address, node address, and router address. IPv6 and IPv4 use, for example, the DHCP (Dynamic Host Control Protocol) server.