網路原理(一) Section 7.2

Address Resolution
位址解析協定(ARP) 是通過解析網路層位址來找尋資料鏈路層位址的一個在網路協定包中極其重要的網路傳輸協定。

Assigned multicast
Assigned multicast addresses are reserved multicast addresses for predefined groups of devices.

Destination or Service Unreachable
When a host or gateway receives a packet that it cannot deliver, it can use an ICMP Destination Unreachable message to notify the source that the destination or service is unreachable.

Dual-stack
As shown in Figure 1, dual stack allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously.

Duplicate Address Detection
To ensure the uniqueness of any IPv6 unicast address, the client may use a process known as Duplicate Address Detection (DAD). 

EUI-64 Process
EEE defined the Extended Unique Identifier (EUI) or modified EUI-64 process. 

FF02::1 All-nodes multicast group
This is a multicast group that all IPv6-enabled devices join.

FF02::2 All-routers multicast group
This is a multicast group that all IPv6 routers join. 

Global Unicast Address
A global unicast address is similar to a public IPv4 address. These are globally unique, Internet routable addresses. Global unicast addresses can be configured statically or assigned dynamically. 

Hextet
In IPv6, a hextet is the unofficial term used to refer to a segment of 16 bits or four hexadecimal values. Each “x” is a single hextet, 16 bits or four hexadecimal digits.

Host confirmation
An ICMP Echo Message can be used to determine if a host is operational. The local host sends an ICMP Echo Request to a host.

ICMPv6
One example is Internet Control Message Protocol version 6 (ICMPv6), which includes address resolution and address auto-configuration not found in ICMP for IPv4 (ICMPv4). 

IPv4 Time-to-Live (TTL)
An ICMPv4 Time Exceeded message is used by a router to indicate that a packet cannot be forwarded because the Time to Live (TTL) field of the packet was decremented to 0.

IPv6
網際網路協定第六版

IPv6 Anycast
An IPv6 anycast address is any IPv6 unicast address that can be assigned to multiple devices. 

IPv6 Hop Limit
IPv6 does not have a TTL field; it uses the hop limit field to determine if the packet has expired.

IPv6 link-local address
Link-local addresses are used to communicate with other devices on the same local link.

IPv6 Loopback Address
To perform this test, we ping the local loopback address of 127.0.0.1 for IPv4 (::1 for IPv6). Testing the IPv4 loopback is shown in the figure.

IPv6 multicast
An IPv6 multicast address is used to send a single IPv6 packet to multiple destinations. 

IPv6 Unicast
An IPv6 unicast address uniquely identifies an interface on an IPv6-enabled device. 

Leading Zeros
The first rule to help reduce the notation of IPv6 addresses is to omit any leading 0s (zeros) in any 16-bit section or hextet. 

Link-local Address
Link-local addresses are used to communicate with other devices on the same local link.

Network Address Translation (NAT64)
Translation – As shown in Figure 3, Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4.

Round Trip Time (RTT)
After all the requests are sent, the ping utility provides a summary that includes the success rate and average round-trip time to the destination.

Route redirection
ICMP messages common to both ICMPv4 and ICMPv6 include

Router Advertisement
Using SLAAC, devices rely on the local router’s ICMPv6 Router Advertisement (RA) messages to obtain the necessary information.

Router Solicitation
An RA message will also be sent in response to a host sending an ICMPv6 Router Solicitation (RS) message.

show ipv6 interface brief ; show ipv6 route
cisco設備的指令

Solicited node multicast
A solicited-node multicast address is similar to the all-nodes multicast address.

Stateless Address Autoconfiguration  (SLAAC)
Stateless Address Autoconfiguration (SLAAC) is a method that allows a device to obtain its prefix, prefix length, default gateway address, and other information from an IPv6 router without the use of a DHCPv6 server. 

Time exceeded
An ICMPv4 Time Exceeded message is used by a router to indicate that a packet cannot be forwarded because the Time to Live (TTL) field of the packet was decremented to 0. 

Tunneling
tunneling is a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data. 

Unique Local Address
Another type of unicast address is the unique local unicast address. IPv6 unique local addresses have some similarity to RFC 1918 private addresses for IPv4, but there are significant differences. Unique local addresses are used for local addressing within a site or between a limited number of sites. 

Unspecified Address
未指定的地址