Datasheet

“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 424 — #450

Mobility IPv6 makes it possible to assign several addresses to one net-

work interface at the same time. This allows users to access several

networks easily, something that could be compared with the interna-

tional roaming services offered by mobile phone companies: when

you take your mobile phone abroad, the phone automatically logs in

to a foreign service as soon as it enters the corresponding area, so you

can be reached under the same number everywhere and are able to

place an outgoing call just like in your home area.

Secure Communication With IPv4, network security is an add-on func-

tion. IPv6 includes IPSec as one of its core features, allowing systems

to communicate over a secure tunnel to avoid eavesdropping by out-

siders on the Internet.

Backward Compatibility Realistically, it would be impossible to switch

the entire Internet from IPv4 to IPv6 at one time. Therefore, it is cru-

cial that both protocols are able to coexist not only on the Internet,

but also on one system. This is ensured by compatible addresses on

the one hand (IPv4 addresses can easily be translated into IPv6 ad-

dresses) and through the use of a number of tunnels on the other (see

Section 21.2.3 on page 429). Also, systems can rely on a dual stack IP

technique to support both protocols at the same time, meaning that

they have two network stacks that are completely separate, such that

there is no interference between the two protocol versions.

Custom Tailored Services through Multicasting

With IPv4, some services, such as SMB, need to broadcast their pack-

ets to all hosts in the local network. IPv6 allows a much more

ﬁne-grained approach by enabling servers to address hosts through

multicasting — by addressing a number of hosts as parts of a group

(which is different from addressing all hosts through broadcasting or

each host individually through unicasting). Which hosts are addressed

as a group may depend on the concrete application. There are some

predeﬁned groups to address all name servers (the all name servers

multicast group), for instance, or all routers (the all routers multicast

group).

424 21.2. IPv6 — The Next Generation Internet