IPv6 Extension Headers

CDE.

IPv6 Extension Headers are used to add extra functionality to the basic IPv6 header. These headers follow the IPv6 header and are identified by the Next Header field in the IPv6 header. There are several IPv6 extension headers defined, and three of them are:

1. Routing Header (Type 0x2B): This header is used by routers to specify the path that packets should take through the network. The Routing header contains a list of IPv6 addresses that represent the path that packets should follow. Each address in the list represents a router that should be visited along the path.

2. Fragmentation Header (Type 0x2C): This header is used to fragment large packets into smaller packets that can be transmitted over a network with a smaller maximum transmission unit (MTU). This header contains information about how the original packet was fragmented, including the identification number of the original packet and the offset of the current fragment in the original packet.

3. Encapsulating Security Payload (Type 0x32): This header is used to provide authentication and confidentiality services to IPv6 packets. The Encapsulating Security Payload (ESP) header contains cryptographic information that is used to encrypt and authenticate the data in the packet. It can be used in combination with the Authentication Header (AH) header to provide both authentication and confidentiality services.

Note that Traffic Class (Type 0x04) and Flow Label (Type 0x06) are not extension headers, but fields in the IPv6 header. The Traffic Class field is used to prioritize packets, while the Flow Label field is used to identify packets belonging to the same flow.