Soft exam: Network interconnection equipment

The interconnected hardware is divided into hardware devices and the media used to transmit the data, and the transmitted devices vary depending on the protocol layer in which they are located. The device is divided into physical layer, data link layer and network layer.

Physical Layer

Repeater device

Objective: To extend the network

Features: Low cost, but can not guarantee the security between the network

Repeater device

1. The first step is to ensure that the packets and logical link protocols in each branch are the same. For example, a repeater cannot communicate between 802.3 Ethernet LANs and 802.5.

2. Repeaters can be used to connect different physical media and transmit packets across a variety of physical media. It can connect different types of media.

3. The number of connected network branches using repeaters is limited by the specific network architecture.

4. The repeater has no isolation and filtering capabilities, and it cannot block packets that contain exceptions from one branch to another. This means that a branch failure may affect each of the other network branches.

Equivalent to: Multi-port repeater. Just imagine that if each device has only one external interface, it means only a couple of points of communication can be established. To be able to make the communication "One-to-many", the signal needs to be replicated to broadcast, so a hub is generated: Repeat the information on one port to the other 7 ports (assuming 8 hub). So the hub can also be called Multiportrepeater. Broadcast will produce conflict, hub have collision detection function, there is a collision is basically to avoid, a person said, another person say, so inefficient.

Hubs

Objective: The role of digital signal amplification and relay

Category: Passive hubs, active hubs, smart hubs

The main function of the hub is to enlarge the received signal to enlarge the transmission distance of the network, and to concentrate all the nodes on the node which is the center. It works on the first level of the OSI (Open Systems Interconnection Reference Model) reference model, the "physical layer". The hub, like the network card, network cable and other transmission media, belongs to the basic equipment of the local area network, using CSMA/CD (a kind of Detection protocol) media access control mechanism.

The hubs are divided into these three categories.

Passive HUB: Responsible for multi-segment media connections, not handling

Active hubs: Relatively passive hubs increase regeneration and amplification

Smart hubs: Relatively active hubs such as network management, select network transmission lines.

In general, a hub is like a more intelligent and port-rich repeater. There are more protocols for this, and some of these features make hubs more functional than repeaters. For example, a hub can connect networks and segments of different protocols, and repeaters are not allowed, only for the same protocol.

Link Layer

The main equipment of the link layer is the Network bridge.

Characteristics:

Realize LAN interconnection on data link layer;

Interconnected networks use the same protocol above the data link layer

Reliability, security

Network Bridge: The function of the repeater, but more intelligent.

Principle: Network 1 and Network 2 through the bridge Connection, the Network Bridge received network 1 sent packets, check the packet address, if the address belongs to Network 1, it will give up, on the contrary, if it is the Network 2 address, It continues to be sent to the network 2. This can use the Network Bridge isolation information, the same network number divided into multiple network segments (belonging to the same network number), isolated from the security network segment, to prevent users in other network segments illegal access. Due to the segment of the network, each network segment is relatively independent (belonging to the same network number), the fault of one network segment will not affect the operation of another network segment.

Network layer

The main devices on the network layer are switches and routers.

A network device for signal forwarding. It can provide the exclusive electrical signal path for any two network nodes that access the switch. The computer room is generally the Ethernet switch. More is the role of forwarding packets, and relative to the router is a more intelligent repeater can be used to better choose a network for the transmission of data the best path.