PLANET XGS3-24040 - Manual (Page 173)

Chapter 21 Layer 3 Forward Configuration
21-3
existing IPv4 infrastructure, including Network Address Translation(NAT for short), and Classless
Inter-Domain Routing(CIDR for short), etc.
Although the combination of CIDR, NAT and private addressing has temporarily mitigated the problem of IPv4
address space shortage, NAT technology has disrupted the end-to-end model which is the original intention of
IP design by making it necessary for router devices that serve as network intermediate nodes to maintain
every connection status which increases network delay greatly and decreases network performance.
Moreover, the translation of network data packet addresses baffles the end-to-end network security check,
IPSec authentication header is such an example.
Therefore, in order to solve all kinds of problems existing in IPv4 comprehensively, the next generation
Internet Protocol IPv6 designed by IETF has become the only feasible solution at present.
First of all, the 128 bits addressing scheme of IPv6 Protocol can guarantee to provide enough globally unique
IP addresses for global IP network nodes in the range of time and space. Moreover, besides increasing
address space, IPv6 also enhanced many other essential designs of IPv4.
Hierarchical addressing scheme facilitates Route Aggregation, effectively reduces route table entries and
enhances the efficiency and expansibility of routing and data packet processing.
The header design of IPv6 is more efficient compared with IPv4. It has less data fields and takes out header
checksum, thus expedites the processing speed of basic IPv6 header. In IPv6 header, fragment field can be
shown as an optional extended field, so that data packets fragmentation process won’t be done in router
forwarding process, and Path MTU Discovery Mechanism collaborates with data packet source which
enhances the processing efficiency of router.
Address automatic configuration and plug-and-play is supported. Large amounts of hosts can find network
routers easily by address automatic configuration function of IPv6 while obtaining a globally unique IPv6
address automatically as well which makes the devices using IPv6 Internet plug-and-play. Automatic address
configuration function also makes the readdressing of existing network easier and more convenient, and it is
more convenient for network operators to manage the transformation from one provider to another.
Support IPSec. IPSec is optional in IPv4, but required in IPv6 Protocol. IPv6 provides security extended
header, which provides end-to-end security services such as access control, confidentiality and data integrity,
consequently making the implement of encryption, validation and Virtual Private Network easier.
Enhance the support for Mobile IP and mobile calculating devices. The Mobile IP Protocol defined in IETF
standard makes mobile devices movable without cutting the existing connection, which is a network function
getting more and more important. Unlike IPv4, the mobility of IPv6 is from embedded automatic configuration
to get transmission address (Care-Of-Address); therefore it doesn’t need Foreign Agent. Furthermore, this
kind of binding process enables Correspondent Node communicate with Mobile Node directly, thereby avoids
the extra system cost caused by triangle routing choice required in IPv4.
Avoid the use of Network Address Translation. The purpose of the introduction of NAT mechanism is to share
and reuse same address space among different network segments. This mechanism mitigates the problem of
the shortage of IPv4 address temporally; meanwhile it adds the burden of address translation process for
network device and application. Since the address space of IPv6 has increased greatly, address translation
becomes unnecessary, thus the problems and system cost caused by NAT deployment are solved naturally.
Support extensively deployed Routing Protocol. IPv6 has kept and extended the supports for existing Internal
Gateway Protocols (IGP for short), and Exterior Gateway Protocols (EGP for short). For example, IPv6
Routing Protocol such as RIPng, OSPFv3, IS-ISv6 and MBGP4+, etc.