A virtual local area network (VLAN) is a group of logical devices and users that are not limited by their physical location， but can be organized according to functional， departments and applications, and communicate with each other as if they were in the same network segment.VLAN is a relatively new technology that works in layer 2 and layer 3 of the OSI reference model. A VLAN is a broadcast domain, and communication between VLAN is accomplished through layer 3 routers.Compared with the traditional LAN technology, VLAN technology is more flexible, it has the following advantages: network equipment to move, add and modify the management overhead reduced, can control broadcast activities, can improve network security.
PPPOE is a point-to-point protocol (PPP) encapsulated in Ethernet in the framework of a tunnel network protocol due to integrate the PPP protocol, so the traditional Ethernet is unable to provide authentication encryption and compression, and other functions, can also be used for cable modem and digital subscriber line to Ethernet protocol to provide user access system.
Multicast technology is designed in the IP network, in the form of a “best” to send information to a particular target group, the target group is called a multicast group. When active host send information demand to the target host, the source host just send a copy of the data, the data of the destination address is a multicast group address.In this way, all belong to the group members can receive a copy of the original host data, the multicast mode members who really need information will receive information,while others can’t receive it.Therefore, multicast method solves the duplication of data and bandwidth in unicast, and also solves the waste of bandwidth in multicast method.
SNMP means simple network management protocol, which is a standard protocol specially designed for IP network management network nodes, such as servers, workstations, routers, switches, etc. It is an application layer protocol.SNMP protocol enables network administrators to manage network performance, discover and solve network problems, and plan network growth. SNMP consists of three key components: network management system, managed device, and agent.
DHCP(Dynamic host configuration protocol), is a LAN network protocol that works using the UDP protocol.DHCP can help us assign IP addresses and related IP information to computers in the network.DHCP can also configure the correct subnet mask, default gateway, and DNS server information on the device.
The main difference between GPON and EPON is the use of completely different standards.GPON was defined by ITU-TG.984 and EPON was defined by IEEE802.3ah.In application,GPON has a bigger bandwidth than EPON, its business carrying more efficient, spectral ability stronger, can transmit more bandwidth business, achieve more users access, pay more attention to business and QoS guarantee, but more complex, so cost is higher than its relative EPON , but with the large-scale deployment of GPON technology, EPON and GPON is diminishing cost differences.
For epon it's normal optical receiving power between -3dbm to -27dbm
For gpon it's normal optical receiving power between -8dbm to -28dbm
SFU (Single Family Unit) single-family unit ONU
It is mainly used for single home users in FTTH scenarios and ordinary terminals that only support broadband access. Generally, it has 1 to 4 Ethernet interfaces and provides Ethernet / IP services. The built-in optical equipment or IAD equipment can support CATV services or VoIP business. Now often used in conjunction with home routers to provide greater business capabilities.
HGU (Home Gateway Unit) Home gateway unit type ONU
It is mainly used for single home users in FTTH occasions. Compared with SFU, which has the function of home gateway, it is equivalent to a home gateway with PON uplink interface. It generally has 2 ~ 4 Ethernet interfaces, 1 WLAN interface and 1 USB interface. Provide Ethernet / IP services, through the built-in optical or IAD devices can support CATV business or VoIP services, support TR-069 remote management.
MDU (Multi.Dwelling Unit) multi-family unit ONU
Mainly used in FTTB / FTTC / FTTCab mode for multiple residential users occasions, with broadband access terminal functions, usually with at least 4 user-side interfaces in the telecom operators equipment selection, often including Ethernet interfaces, ADSL2 + Interface or VDSL2 interface to provide Ethernet / IP services. In the radio and television operators of the network applications, due to differences in business content, generally only contains the Ethernet interface for PON + LAN access.
MTU (Multi-tenant Unit) Multi-tenant unit type ONU
It is mainly used for multiple enterprise users in the FTTB scenario or multiple individual users in the same enterprise. It has the function of broadband access terminal and has multiple Ethernet interfaces (usually at least eight), E1 interfaces and POTS interfaces, and provides Ethernet Network / IP services, TDM services and VoIP services (built-in IAD).
SBU (Single Business Unit) single-business unit ONU
Mainly used in the case of FTTO, separate business users and businesses in a single office access. Support broadband access terminal functions, in the telecom operation network, generally with Ethernet interface, E1 interface, VOIP interface, etc., to provide Ethernet / IP services and TDM services.
Yes, C-Data Wireless Ap Ceiling type CW8837AP and outdoor type CW9833AP both meet 802.11ac standard.
A wireless AP (AP, Access Point, Wireless Access Point, Conversation Point, or Access Bridge) is a well-known name that includes not only simple wireless access points (wireless APs), but also wireless routers Gateway, wireless bridge) and other types of equipment collectively. It mainly provides wireless workstations for wired LAN and wired LAN access to wireless workstations, wireless access point within the coverage of wireless workstations can communicate with each other.
Simple wireless AP is a wireless switch that provides wireless signal transmission and reception functions. Simple wireless AP’s working principle is the network signal transmitted over twisted pair, after AP product compilation, the electrical signal is converted into a wireless signal sent out to form a wireless network coverage. According to different power, it can achieve different degrees and different ranges of network coverage, the maximum wireless AP coverage of up to 500 meters. Most simple wireless AP itself does not have the routing function, including DNS, DHCP, Firewall, server functions must have independent routing or computer to complete.
Ethernet Over Coax also called EOC for short. It is an equipment which used for triple play service in a new generation broadcasting network. Widely used by consumers and telecommunications operators in existing 75 ohm coaxial cable installations (from cable television or CATV), to carry broadband data into and through the home, and into multiple dwelling unit (MDU) installations.
Data EOC network is built with EOC Master and EOC Slave.
Hybrid fiber-coaxial (HFC) is a telecommunications industry term for a broadband network that combines optical fiber and coaxial cable.
In a hybrid fiber-coaxial cable system, the television channels are sent from the cable system’s distribution facility, the headend, to local communities through optical fiber trunk lines. At the local community, a box called an optical node translates the signal from a light beam to electrical signal, and sends it over coaxial cable lines for distribution to subscriber residences. The fiberoptic trunk lines provide adequate bandwidth to allow future expansion and new bandwidth-intensive services.
ONU consists of active Optical Network Unit and passive Optical Network Unit.It has two functions: selective reception of the broadcast sent by OLT, and receiving response to OLT if the data is needed;The Ethernet data that the user needs to send is collected and cached, and the cached data is sent to the OLT side according to the assigned send window.
Switches, routers are almost all network devices used in modern local area networks. Among them, switches are responsible for connecting network devices (such as switches, routers, firewalls, wireless APs, etc.) and terminal devices (such as computers, servers, cameras, network printers, etc.) ); The router realizes the interconnection between the local area network and the local area network, and the interconnection between the local area network and the Internet; In general, the switch is responsible for connecting devices, the router is responsible for connecting to the network.
The function of the switch is to connect terminal devices such as computers, servers, network printers, network cameras, IP phones, and realize the interconnection with other network devices such as switches, wireless access points, routers, network firewalls, etc., so as to build a local area network and realize all devices Communication between.
The switch is located in the second layer (data link layer) of the OSI reference model. The work of the switch relies on the identification of the MAC address (all network devices have a unique MAC address, which is usually directly burned into the network card by the manufacturer) ).
Routers are also called gateways, which connect local area networks to form a larger wide area network. When connecting heterogeneous networks (heterogeneous networks refer to different network types, such as ATM networks, FDDI networks, Ethernet networks, etc.). Heterogeneous networks use different data encapsulation methods and cannot communicate directly, and routers can “translate” these different encapsulated data to achieve communication in heterogeneous networks. In addition, for the local area network, the wide area network is undoubtedly a heterogeneous network.
In general, the main differences between routers and switches are reflected in the following aspects:
(1) Different levels of work
The original switch worked at the data link layer of the OSI/RM open architecture, which is the second layer, and 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), it can get more protocol information, and the router can make Smarter forwarding decisions.
(2) The data forwarding is based on different objects
The switch uses the physical address or MAC address to determine the destination address of the forwarded data. The router uses the ID numbers (ie IP addresses) of different networks to determine the address for data forwarding.
(3) Traditional switches can only divide conflict domains, not broadcast domains; routers can divide broadcast domains
The network segment connected by the switch still belongs to the same broadcast domain. Broadcast data packets will spread to all network segments connected to the switch, and in some cases will cause communication congestion and security vulnerabilities. Although the switches above the third layer have the VLAN function, they can also be divided into broadcast domains, but the sub-broadcast domains cannot communicate, and the communication between them still requires a router.
(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 network data packets whose purpose is unknown, which can prevent broadcast storms. Switches are usually used for LAN-WAN connections. Switches are classified as bridges, which are devices at the data link layer. Some switches can also achieve Layer 3 switching. In contrast, routers are more powerful than switches, but they are relatively slow and expensive. The three-layer switch combines the wire-speed packet forwarding capability of the switch and the good control function of the router, so it is widely used.
Whether it is a switch, a router , the realization of the functions of these network devices requires the network engineer to configure the device in advance (such as VLAN virtual network port division, firewall security policy configuration, router default gateway setting, etc.). At a different level, these network devices are computers with cpu and memory, and all implement hardware functions through the “translation” of the cpu to the machine language.
Switches are the common equipment for data forwarding in local area networks(LAN), and their performance and functions determine the manageability and data forwarding performance of the LAN. The following aspects should be considered when choosing a switch:
Number of ports
The number of physical ports supported by the switch determines the number of terminals or secondary devices connected to the switch, which need to be selected according to actual needs. Of course, subsequent network expansion needs to be considered. The access port of the switch is used to connect the internal network terminal, and the uplink port is used to connect to the upper-level equipment.
2.Port Speeds and Types
Switches come in Fast Ethernet and Gigabit Ethernet. Fast Ethernet allows up to 100 Mb/s of traffic per switch port while Gigabit Ethernet allows up to 1000 Mb/s of traffic per switch port. These ports may be a combination of SFP/SFP+ slots for fiber connectivity, but more commonly they are copper ports with RJ-45 connectors on the front, allowing for distances up to 100 meters. With Fiber SFP modules, you can go distances up to 40 kilometers. Currently, Gigabit Ethernet is the most popular interface speed though Fast Ethernet is still widely used, especially in price-sensitive environments.
3.Switch access capacity
The amount of equipment attached to the switch is mainly reflected in the depth of the MAC address table of the switch. At the same time, it is also necessary to pay attention to the number of host routing entries for the three-layer switch. For example, when selecting a Layer 3 switch, the number of all access terminals of the Layer 3 switch is required to be less than the number of host routing entries of the Layer 3 switch.
4.Network scale and switch network structure
Considering the scale and level of switch application networks, which are mainly divided into small and medium-sized networks and large and medium-sized networks, the recommendations are as below:
Divide VLANs to realize that ports belonging to different VLANs can’t communicate with each other; Set static routes to realize that VLANs of different network segments can communicate with each other; DHCP snooping prevents the access of other DHCP servers from affecting the LAN. The above functions are commonly used in large and medium LANs.
Specifically, such as: Access Control List, 802.1X authentication(Radius,Tacacs+), loopback detection, IGMP Snooping, etc.
At any layer, a modern switch may implement power over Ethernet (PoE), which avoids the need for attached devices, such as a VoIP phone or wireless access point, to have a separate power supply. Since switches can have redundant power circuits connected to uninterruptible power supplies, the connected device can continue operating even when regular office power fails. Another characteristic you consider when choosing a switch is PoE. This is the ability of the switch to deliver power to a device over the existing Ethernet cabling. To find the switch that is right for you, all you need to do is choose a switch according to your power needs. When connecting to desktops which do not require PoE switches, the non-PoE switches are a more cost-effective option.