ZyXEL Communications P8802T, Руководство пользователя

Страница: 77 / 278

Chapter 4 WAN
Basic Home Station VDSL2 P8802T User’s Guide
77
Service) can be guaranteed. ATM uses a connection-oriented model and establishes a virtual circuit
(VC) between Finding Out More
PTM
Packet Transfer Mode (PTM) is packet-oriented and supported by the VDSL2 standard. In PTM,
packets are encapsulated directly in the High-level Data Link Control (HDLC) frames. It is designed
to provide a low-overhead, transparent way of transporting packets over DSL links, as an
alternative to ATM.
3G
3G (Third Generation) is a digital, packet-switched wireless technology. Bandwidth usage is
optimized as multiple users share the same channel and bandwidth is only allocated to users when
they send data. It allows fast transfer of voice and non-voice data and provides broadband Internet
access to mobile devices.
IPv6 Introduction
IPv6 (Internet Protocol version 6), is designed to enhance IP address size and features. The
increase in IPv6 address size to 128 bits (from the 32-bit IPv4 address) allows up to 3.4 x 10
38
IP
addresses. The VDSL Router can use IPv4/IPv6 dual stack to connect to IPv4 and IPv6 networks,
and supports IPv6 rapid deployment (6RD).
IPv6 Addressing
The 128-bit IPv6 address is written as eight 16-bit hexadecimal blocks separated by colons (:). This
is an example IPv6 address
2001:0db8:1a2b:0015:0000:0000:1a2f:0000
.
IPv6 addresses can be abbreviated in two ways:
• Leading zeros in a block can be omitted. So
2001:0db8:1a2b:0015:0000:0000:1a2f:0000
can
be written as
2001:db8:1a2b:15:0:0:1a2f:0
.
• Any number of consecutive blocks of zeros can be replaced by a double colon. A double colon can
only appear once in an IPv6 address. So
2001:0db8:0000:0000:1a2f:0000:0000:0015
can be
written as
2001:0db8::1a2f:0000:0000:0015
,
2001:0db8:0000:0000:1a2f::0015
,
2001:db8::1a2f:0:0:15
or
2001:db8:0:0:1a2f::15
.
IPv6 Prefix and Prefix Length
Similar to an IPv4 subnet mask, IPv6 uses an address prefix to represent the network address. An
IPv6 prefix length specifies how many most significant bits (start from the left) in the address
compose the network address. The prefix length is written as “/x” where x is a number. For
example,
2001:db8:1a2b:15::1a2f:0/32
means that the first 32 bits (
2001:db8
) is the subnet prefix.