Analyzing Challenging Aspects Of IPv6 over IPv4: The Internet Protocol is routable protocol over the Network. There is no surety to deliver a packet by IP.
In fact, the IP Address tries its best to deliver a packet over the network in best possible way through different routes.
Some application protocols such as FTP, SMTP, and HTTP have required a guarantee of packet delivery. To provide a guarantee of packet delivery services, the IP protocol is associated with TCP protocol on the transport layer.
The packets are moved on the network in an arbitrary path if multiple paths exist. On the network layer, a segment is encapsulated by an IP header before sending.
Source and destination IP addresses are enclosed in an IP header. The IANA has declared some blocks of IP address from different classes for private networking.
The 169.254.0.0/16 address reserved for link-local addressing. All the reserved and private addresses are not routable over the Internet. The NAT was introduced to provide Internet access for private networks.
The majority of Network traffic is based on IPv4. In IPv4 packet, header and data unit is part of that packet.
Before transmitting the packet over the network, the header of minimum 20 bytes is encapsulated with the Data Unit part of IPv4.
The IPv4 header consists of 14 fields. Its maximum size is 60-bytes. One field is optional. The first4-bits of the header are version. It indicates the IP version used.
A TTL8-bits field helps stop the packet from moving in the loop on the Internet. Every time when a packet arrives and crosses one node on the network, then its TTL field is decremented by one.
When the TTL field becomes zero, the node discards the packet. The header checksum 16- bits field is used for error checking of the header.
When a packet reaches the router, the checksum of the header is calculated by the router.
The router compares both values. If the value does not match, the router discards the packet. The32-bits source and destination IP addresses fields are used to store the sender and receiver IP addresses respectively.
These addresses may be changed in transition by NAT devices.
About IPv6 Header
The most recent version for IP addressing is IPv6 which is supposed to be used for coming generation. It is called 128 bit addressing architecture. Its total IP addresses can be calculated in 2128 , almost 3.4 x 1038 total IP addresses.
Most repeated zeros can be reduced to double colon. Because of large addressing volume, there is not necessary for Network Addressing Translation. But some Addresses range can be reserved by its standard IANA.
In IPv6, a new multicast implementation technique has introduced. A new feature Stateless Address Auto Configuration (SLAAC) is introduced in IPv6 to eliminate additional configuration servers.
It allows a host to generate own address using a combination of link-local address and information advertised by routers. IPsec is used as a built-in security feature in IPv6 with the help of the extension header.
It is a mandatory part of all IPv6 protocol implementation. The extension header carries optional information along with the IPv6 header. The extension header provides support for fragmentation.
There are several types of extension headers.
The IPv6 header is simplified. Some fields are removed. It consists of only 8 fields. Its size is fixed and that is 40-bytes. The first4-bits of the header is also version same as in IPv4. The TTL field is replaced with the 8-bits Hop Limit field.
The Next Header 8-bits field in the fixed header indicates the type of the extension header.
The size of the source and destination IP addresses fields are increased to 128-bits. The Flow Label20-bits field provides traffic engineering and QoS services. read full pdf here