1, the network layer provides two services:
(A) connection-oriented
(2) No connection
2, Internet Protocol (IP)
(1) Internet Protocol (IP) is one of the TCP / IP system in two major agreements.
(2) There are three supporting protocols used with IP protocol:
A: Address Resolution Protocol ARP ------ converts IP addresses to the MAC address
B: Internet Control Message Protocol ICMP
C: IGMP Internet Group Management Protocol
3, the network interconnecting them to use some intermediate device.
Apparatus known as intermediate systems or intermediate systems relay.
By the following five different intermediate apparatus:
(1) The physical layer repeater system: transponder
(2) data link layer relay system: a bridge or bridge
(3) network layer relay system: Routers
The mixture (4) bridges and routers: bridger
(5) The above network layer relay system: Gateway
4, are interconnected network refers to network interconnection and routing with routers.
5, an IP address is unique within the scope of the entire Internet.
6, some of the important features of IP addresses
(1) IP address is an address structure of the sub-grade. Benefits are divided into two classes:
A: Units assigned IP address management agency network number when assigning IP addresses only, and the rest of the network host number obtained by the number of discretionary. This facilitates the management of IP addresses.
B: The network router to forward only the number of the destination host is connected packet (regardless of the destination host number), so that the router can be the number of items in the table greatly reduced, thereby reducing the storage space occupied by the routing table.
(2) is actually the IP address of a host flag (or router) and a link interface.
(3) connected by a plurality of repeaters or bridges a network Intranets, local area networks so these networks have the same number of net-id.
(4) all assigned to the network number net-id of the network, whether it is a small range of local area network, or may cover a large geographical range of WAN, they are equal.
7, IP address and hardware address
(1) IP addresses and hardware addresses are different address.
(2) from level point of view,
A: hardware address (or physical address) is the address of the data link layer and the physical layer used.
B: IP address is a network layer addresses and one or more layers, is a logical address (called an IP address is a logical address because the IP addresses are implemented in software).