What are network devices with functions such as network interconnection, network isolation, and flow control?

A network device with functions such as network interconnection, network isolation, and traffic control is a "router".

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The main functions of "router" are network interconnection, network isolation and traffic control.

A router is a hardware device that connects two or more networks. It acts as a gateway between networks. It is a dedicated intelligence that reads the address in each data packet and then decides how to transmit it. network equipment. It can understand different protocols, such as the Ethernet protocol used by a local area network and the TCP/IP protocol used by the Internet. In this way, the router can analyze the destination addresses of data packets from various types of networks, convert the addresses of non-TCP/IP networks into TCP/IP addresses, or vice versa; and then classify each data packet according to the selected routing algorithm. Deliver the best route to the specified location. So the router can connect non-TCP/IP networks to the Internet.

Function of router

Simply speaking, the router mainly has the following functions:

• First, network interconnection Connection, the router supports various LAN and WAN interfaces, which are mainly used to interconnect LANs and WANs to enable different networks to communicate with each other;

• Second, data processing, including packet filtering, grouping Forwarding, priority, multiplexing, encryption, compression and firewall functions;

• Third, network management, the router provides functions including configuration management, performance management, fault tolerance management and flow control. .

The specific functions are as follows:

(1) Realize the interconnection of IP, TCP, UDP, ICMP and other networks.

(2) Process the data. It can send and receive data packets and has various functions such as packet filtering, multiplexing, encryption, compression and protection wall of data.

(3) Select the next transmission destination of the data packet based on the information in the routing table.

(4) Exchange topology information between the external gateway protocol and other autonomous domains.

(5) Implement network management and system support functions.

How the router works

1. The router receives data from a website it is connected to.

2. The router passes the data upward and (if necessary) reassembles the IP datagram.

3. The router checks the destination address in the IP header. If the destination address is on the network where the data is sent, then the router drops the data that is considered to have reached the destination because the data is on the network where the destination computer is. transmission.

4. If the data is to be sent to another network, the router queries the routing table to determine the destination to which the data is to be forwarded.

5. After the router determines which adapter is responsible for receiving the data, it passes the data through the corresponding software so that the data can be transmitted through the network.

Differences from switches

In general, the main differences between routers and switches are reflected in the following aspects:

(1) Work Different levels

The original switch worked at the data link layer of the OSI/RM open architecture, which is the second layer, while the router was designed to work at the network layer of the OSI model from the beginning. Since the switch works on the second layer of OSI (data link layer), its working principle is relatively simple, while the router works on the third layer of OSI (network layer), and can get more protocol information, and the router can make Smarter forwarding decisions.

(2) The objects based on data forwarding are different

The switch uses the physical address or MAC address to determine the destination address of the forwarded data. The router uses the ID numbers (i.e. IP addresses) of different networks to determine the address for data forwarding. IP addresses are implemented in software and describe the network where the device is located. Sometimes these third-layer addresses are also called protocol addresses or network addresses. The MAC address usually comes with the hardware and is assigned by the network card manufacturer. It has been solidified into the network card and generally cannot be changed. IP addresses are usually assigned automatically by the network administrator or the system.

(3) Traditional switches can only divide conflict domains, not broadcast domains; routers can divide broadcast domains

The network segments connected by the switch still belong to the same broadcast domain, and broadcast data Packets are propagated on all network segments to which the switch is connected, causing traffic congestion and security breaches in some cases. Network segments connected to the router will be assigned to different broadcast domains, and broadcast data will not pass through the router. Although switches above the third layer have VLAN functions and can also divide broadcast domains, sub-broadcast domains cannot communicate with each other, and communication between them still requires routers.

Now some switches that work at the third layer (network layer) can also function as routers. Switches have been commonly used in local area networks to replace previous routers. Routers are used to interconnect local area networks and wide area networks.

(4) The router provides firewall services

The router only forwards data packets with specific addresses, and does not transmit data packets that do not support routing protocols and unknown destination network data packets, thus Can prevent broadcast storms.

Switches are generally used for LAN-WAN connections. Switches are classified as bridges and are devices at the data link layer. Some switches can also implement third-layer switching. Routers are used for WAN-WAN connections. They can forward packets between heterogeneous networks and act on the network layer. They simply accept input packets from one line and forward them to another line. The two lines may belong to different networks and use different protocols. In comparison, routers are more powerful than switches, but are relatively slow and expensive. Layer 3 switches have both the line-speed packet forwarding capability of switches and the good control functions of routers, so they are widely used.

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