Network Equipment Brief Introduction (network basic knowledge)

1 Repeater

A repeater (repeater) is a network device located on the first layer (physical layer).

As the cables pass through more and more longer, the signal becomes weaker. The purpose of the repeater is to regenerate and re-timer the network signal at the bit level . which allows them to transmit longer distances over the network.

Repeaters only work on a higher-than-premium, without looking at other information

2 hubs (hub)

The purpose of the hub is to regenerate and re-timer the network signals. Its characteristics are similar to repeaters.

The hub is a universal connection point for each device in the network, which is typically used to connect the segments of the LAN.

The hub has multiple ports, each of which arrives at a port and is copied with all other ports, all of which can be seen in all LAN segments.

Because hubs and repeaters have similar characteristics, hubs are also known as multi-port relays

belongs to the first layer of equipment

Features of the Hub:

Amplified signal

Spread the signal across the network

No filtering required

No path determination or exchange required

As a network aggregation point 3 network interface card

A network interface card (NIC) is a second-tier device with every NIC in the world with a unique encoding called Media access Control (MAC). 4 Network Bridge

A network bridge is a second-tier device that involves creating two or more LAN segments. Each of these segments is a separate conflict domain. In other words, the bridge involves the use of more bandwidth to generate. Its purpose is to filter the traffic flow of the LAN so that local traffic is kept locally, and the traffic that is directed to other parts of the LAN (fragmentation) is sent there.

The bridge records the MAC address on each side of it, and then gives the Mac table a forwarding decision

Features of the Network Bridge:

Bridges are smarter than hubs to analyze incoming frames

A network bridge collects and forwards groupings between two or more LAN segments

Bridges create more conflict domains, allowing multiple devices to send without conflicting messages at the same time

Bridge Maintenance MAC Address Table

the work steps of the bridge:

1. When the data frame arrives along the network medium, the bridge compares the destination MAC address that is carried in that frame with the MAC address table contained in it

2. If the bridge determines that the destination MAC address of the data frame is in the same segment as the source's MAC address, it will not forward the changed data frame to other network segments, that is, filtering.

3. If the bridge determines that the destination MAC address of the data frame is not in the same segment as the source's MAC address, then forwards it to the network segment when

4, if the destination MAC address is not known to the bridge, then broadcast the data frame to the network in addition to the device that sent the frame on all previous devices. This process is known as flooding.

Conflict domain: In Ethernet, this CSMA/CD network is a conflict domain if two computers on a CSMA/CD network conflict when they communicate simultaneously. Increasing conflict domains can reduce the occurrence of conflict 5 second layer switch

A switch, also known as a LAN switch or workgroup switch, typically replaces a shared hub and works with an existing cable infrastructure to minimize disruption to existing networks after the switch is installed.

Switches and bridges are similar in many places. The switch also connects the segments of the LAN. It uses a MAC address table to determine which segment the frame needs to forward to, and thus less traffic. However, the switch is processing faster.

The switch also forwards and floods the communication frames based on the MAC address. Because the exchange is performed in hardware, the switching speed of the switch is much faster than the exchange of the software performed in the bridge.

Each switch port acts as a mini-bridge, each switching port acting as a separate bridge, providing each host with the full bandwidth of the media. This method is called the differential segment

Differential Segments: Micro-segmentation allows the creation of private or private segments (one host for one segment). This allows each host to gain full bandwidth without competing with other hosts for available bandwidth. In a full-duplex switch, there is no conflict because only one device is connected to the port of the switch.

Because switches and bridges are the same, they are all fragments that forward broadcast messages to the switch. Therefore, all segments in the switch environment are considered to be in the same broadcast domain

6 Routers

What is a route.

Routers are a class of network interconnection devices that pass data groupings between networks based on a third-tier address. It can select the best delivery path for data grouping on the network

Features of work on the third floor:

Make a decision without a MAC address.

Ability to connect different second-tier technologies

Can connect asynchronous transmissions and serial lines.

Because of the ability to route packets based on third-tier information, routers have become a major part of the Internet, which runs the IP protocol.

Work steps:

The router examines each incoming packet (the third layer of data), selects the best path through the network for them, and then swaps them to the appropriate exits.

7 APs

In general, an access point (AP) is installed as a hub hub for the WLAN infrastructure pattern. The AP connects to a wired device through a fixed line. This area becomes a beehive (cell).

The APS are functionally divided into fat APs and thin APs.

Fat AP: Has the route forwarding function

Thin AP: Just as a wireless and wired conversion hub

Depending on the structure at which the access point is installed, and the size and gain of the antenna, the size of the honeycomb can be from a few feet to 25 miles. The more common distance range is 91.4~152.4m. In order to serve a larger area, you can install a pair of APS with a certain degree of overlap to support roaming between the cells.

This roaming is similar to a roaming service provided by a mobile phone company. Overlapping of multiple AP networks is critical to support the device's movement in the WLAN. Although not specified in the IEEE standard, the overlap rate of 20~30% is expected. This overlap rate enables roaming between cells, enabling seamless disconnection/re-interconnection without disruption to the service.

When a client in a WLAN is activated, it begins to listen for which compatible device can be associated. This process is called scanning

Proactively scan your wireless node for a probe request to find a network to join. The probe request contains the service Set identifier (IDENTITY,SSID) that you want to join the network. If the ap,ap of the same SSID is encountered, a probe response is issued, and the authentication and correlation steps are complete.

The passive scan node listens for signal management frames (beacons) emitted by the AP (infrastructure mode) or peer node (temporary) and attempts to join the network when a node receives a signal management frame containing the SSID it wants to join the network. A continuous process during a passive scan, where the node can establish or eliminate the association with the AP as the signal strength changes