網路原理(一) Section 6.1

encapsulation
封裝

routing
路由

de-encapsulation
解封裝

data
資料

packet
封包

frame
窗框

Internet Protocol Version 4 (IPv4)
網際網路協定第四版

Internet Protocol Version 6 (IPv6)
網際網路協定第六版

Network Layer PDU
IP Packet

Transport Layer PDU
Segment

Segment Header
segment標頭

IP Header
IP標頭

Auxiliary port (AUX)
Some devices, such as routers, may also support a legacy auxiliary port that was used to establish a CLI session remotely using a modem. Similar to a console connection, the AUX port is out-of-band and does not require networking services to be configured or available.

connectionless
IP is connectionless, meaning that no dedicated end-to-end connection is created before data is sent.

best effort delivery
The IP protocol does not guarantee that all packets that are delivered are, in fact, received. 

media independent
IP operates independently of the media that carry the data at lower layers of the protocol stack. 

unreliable
As an unreliable network layer protocol, IP does not guarantee that all sent packets will be received. 

maximum transmission unit (MTU)
The maximum size of the PDU that each medium can transport. This characteristic is referred to as the maximum transmission unit (MTU).

version
版本

differentiated Services (DS)
Formerly called the Type of Service (ToS) field, the DS field is an 8-bit field used to determine the priority of each packet. 

Time-to-Live (TTL)
Contains an 8-bit binary value that is used to limit the lifetime of a packet. The packet sender sets the initial TTL value, and it is decreased by one each time the packet is processed by a router.

Internet Control Message Protocol (ICMP)
網際網路控制訊息協定（英語：Internet Control Message Protocol，縮寫：ICMP）是網際網路協定套組的核心協定之一。

data payload
資料有效載荷

Identification, Flags, Fragment Offset fields
Other fields are used to reorder a fragmented packet. Specifically, the IPv4 packet uses Identification, Flags, and Fragment Offset fields to keep track of the fragments.

keyword
關鍵字

Network Address Translation (NAT)
Network Address Translation (NAT) is a technology commonly implemented within IPv4 networks. NAT provides a way for multiple devices to share a single public IPv4 address. 

Traffic Class
This 8-bit field is equivalent to the IPv4 Differentiated Services (DS) field.

Flow Label
This 20-bit field suggests that all packets with the same flow label receive the same type of handling by routers.

Payload length
This 16-bit field indicates the length of the data portion or payload of the IPv6 packet. 

next header
This 8-bit field is equivalent to the IPv4 Protocol field.

hop limit
This 8-bit field replaces the IPv4 TTL field. 

local host
本機

remote host
遠端

default gateway
The default gateway is the network device that can route traffic to other networks. It is the router that can route traffic out of the local network.