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The difference between a switch and a router

Time : 2021-10-29 Hits : 109

Computer networks are often made up of many different types of interconnections. If several computer networks are only physically connected and cannot communicate with each other, then this “ Interconnection” has little practical meaning. Therefore, when talking about the “ Interconnection”, it is implied that there interconnected computers can communicate with each other. That is to say, functionally and logically, there computer networks have formed a large computer network, or internet, or internet for short.

Connecting networks to each other uses intermediary devices ( or intermediate systems), known is ISO terminology as replay systems. Based on the Layer of the trunk system, the following five trunk systems are available.

1) Physical Layer ( Commonly known as layer, layer L1) relay system, namely repeater.

2) Date Link Layer ( layer1, layer L2 ), namely network bridge or bridge.

3) Network Layer ( Layer 3, Layer 3) Trunk system, namely router.

4) Brouter combines the functions of bridge and router.

5) The trunk system above the network layer is called the gateway.

When the intermediate system is a repeater, it is generally not called network interconnection because it merely extends a network, which is still a network. Because of its complexity, the high-level gateway is seldom used. Therefore, when we talk about network interconnection, we usually refer to the network connected by switches and routers. This article mainly describes the switch and router and their difference.

Switches and Routers.

“ Switching” is one of the most frequently used words on the internet today. used in everything from bridges to routers to ATMS to telephone systems, and it’s not clear what an exchange really is. In fact,

The word exchange first appeared in the telephone system, specifically refers to the realization of the exchange of voice signals between two different telephone sets, the work of the equipment is the telephone exchange. So, in its original sense, switching is just a technical concept that completes the forwarding of signals from the entrance to the exit of the device. Therefore, all devices that are and conform to this definition can be called switching devices.

Thus, “switch” is a word with broad meaning. When it is used to describe a device at layer 2 of the data network.It actually refers to a bridging device. When it is used to describe the device at the third layer of the data network. It refers to a routing device.The Ethernet switch we often talk about is actually a multi-port layer2 network device based on the bridge technology. It provides a low delay and low cost path for data frame forwarding from one port to another arbitrary port.

Thus, the internet core of the switch should have a switching matrix that provides a path for communication between any two ports, of a fast switching bus that allows frames received at any port to be sent from other ports. In real equipment, the function of switching matrix is usually performed by special Chipset ( ASIC). In addition, Ethernet switches on the design though has an important 

assumption , namely core exchange speed is very fast, so that usually big traffic congestion data will not make it, In other words, the exchange capacity relative to report the amount of information and infinity ( by contrast, the ATM switches, the thinking in design, think exchange capacity.) Although Layer 2 Ethernet switches are based on multi-port bridges, switching has richer features that make it not only the best way to get more bandwidth, but also easier to manage the network.

A router is a packet switching device (or network layer replay device) at the network layer of the OSI protocol model. The basic function of a router is to transmit data (IP packets) to the correct network, inclduing:

1) IP datagram forwarding, including datagram pathfinding and transmission.

2) Isolate subnets to suppress broadcast storms.

3) Maintain the routing table and exchange routing information with other routers, which is the basis for IP packet forwarding.

4) IP datagram error handing and simple congestion control.

5 Filter and account for IP datagrams.

For networks of different scales, the emphasis of router is different.

The main function of a router on a backbone network is routing. The router on the trunk network must know the path to all the lower networks. This requires maintaining large routing tables and reacting as quickly as possible to changes in connection state. A router failure can cause serious transmission problems.

In the area network, the main function of a router is network connection and router selection, that is, it connects all the basic network units at the lower layer-- the campus network, and is responsible for data forwarding between the lower layer networks.


On the campus networks, routers are used to separated sub-nets. The early basic unit of the internet was the local area network ( LAN), in which all hosts lived on the same logical network. With the expansion of network scale, local area networks ( LANS) have evolved into a campus network consisting of several sub-nets connected by high-speed backbone and routers. Among them, the sub-nets are logically independent, and the router is the only device that can separate them. It is responsible for packet forwarding and broadcast isolation between sub-nets, and the router on the border is responsible for the connection with the upper network.


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