Operation Manual – IPv6H3C S5500-EI Series Ethernet Switches Chapter 1 IPv6 Basics Configuration1-21.1.1 IPv6 FeaturesI. Header format simplificationIPv6 cuts down some IPv4 header fields or move them to the IPv6 extension headers toreduce the length of the basic IPv6 header. IPv6 uses the basic header with a fixedlength, thus making IPv6 packet handling simple and improving the forwardingefficiency. Although the IPv6 address size is four times that of IPv4 addresses, the sizeof basic IPv6 headers is 40 bytes and is only twice that of IPv4 headers (excluding theOptions field).Ver0 113Trafficclass Flow labelPayload length Nextheader Hop limitSource address (128 bits)Destination address (128 bits)3115 23Ver HL ToS Total length0 73 3115 23Identification Fragment offsetFTTL Protocol Header checksumSource address (32 bits)Destination address (32 bits)Options PaddingIPv4 headerBasic IPv6 headerFigure 1-1 Comparison between IPv4 packet header format and basic IPv6 packetheader formatII. Adequate address spaceThe source and destination IPv6 addresses are both 128 bits (16 bytes) long. IPv6 canprovide 3.4 x 10 38 addresses to completely meet the requirements of hierarchicaladdress division as well as allocation of public and private addresses.III. Hierarchical address structureIPv6 adopts the hierarchical address structure to quicken route search and reduce thesystem source occupied by the IPv6 routing table by means of route aggregation.IV. Automatic address configurationTo simplify the host configuration, IPv6 supports stateful and stateless addressconfiguration.z Stateful address configuration means that a host acquires an IPv6 address andrelated information from a server (for example, DHCP server).
