Switching technology allows shared and dedicated LAN segments to adjust bandwidth to mitigate bottlenecks in information flow between LANs. There are now switching products for Ethernet, Fast Ethernet, FDDI, and ATM technologies.
1. Bottlenecks in the switch network
The processing speed of the switch itself can be very high, and users often superstitiously advertise the Gbps-class high-speed backplane. In fact, this is a misunderstanding. The network used by workstations or servers connected to the network is a large network, which follows the CSMA/CD media access rules. In the current client/server mode network, multiple workstations access the server at the same time, so it is very easy to form a server bottleneck. Some vendors have already considered this point. One or more high-speed ports are designed in the switch (such as 3COM Linkswitch1000 can be configured with one or two 100Mbps ports), which is convenient for users to connect to servers or high-speed backbones. Users can also eliminate bottlenecks by designing multiple servers (for service partitioning) or by adding multiple network cards. The switch also supports spanning tree algorithms, making it easy for users to architect fault-tolerant redundant connections.
2. Broadcast frames in the network
Currently, the ports of each switch support a certain number of MAC addresses, so that the switch can “memorize” a group of connected sites on the port. The number of MAC addresses supported by different vendors is different. Pay attention to the number of connection endpoints on the switch port. If the MAC address is exceeded by the manufacturer when the switch receives a network frame, only the MAC address of the destination station does not exist in the MAC address table of the switch port, then the frame is broadcast to each port of the switch.
3. Division of virtual networks
A virtual network is an important function of a switch. Generally, there are three implementation forms of a virtual network:
(1) Static port assignment
The division of a static virtual network is usually performed by the network administrator using the network management software or directly setting the port of the switch to directly belong to a virtual network. These ports always maintain these dependencies unless the network administrator resets them. Although this method is cumbersome, it is safer and easier to configure and maintain.
(2) Dynamic virtual network
Support for dynamic virtual network ports, which can be automatically determined by intelligent management software. The port determines the slave of the virtual network by means of the MAC address, logical address or protocol type of the network packet. When a network node is just connected to the network, the switch port has not been allocated, so the switch dynamically maps the port to a virtual network by reading the MAC address of the network node. In this way, once the network administrator is configured, the user’s computer can flexibly change the switch port without changing the secondary network attribute of the user, and if an undefined MAC address appears in the network, the network administrator can be alerted.
(3) Multiple virtual network port configuration
This configuration allows one user or one port to access multiple virtual networks simultaneously. In this way, a network server can be configured into multiple business departments (each service is set to a virtual network), which can be accessed at the same time, or can simultaneously access resources of multiple virtual networks, and can also connect multiple virtual networks only. A routing port is required to complete. But this will bring security risks. The industry specifications for virtual networks are being developed, so the products of various companies are still not interoperable. Cisco has developed the Inter-Switch Link (ISL) virtual network protocol, which supports virtual networks across backbone networks (ATM, FDDI, Fast Ethernet). But the agreement is accused of lack of security considerations. A large number of shared Hubs are used in traditional computer networks, and good results can be obtained by flexible access to computer ports.
4. Application of high-speed LAN technology
Although Fast Ethernet technology maintains good compatibility with traditional networks in some respects, 100BASE-TX, 100BASAE-T4 and 100BASE-FX have relatively large limitations on transmission distance and cascading. These limitations can be broken by a 100Mbps switch. At the same time, only the switch port can support duplex high-speed transmission.
At present, there is also a CDDI/FDDI exchange technology. In addition, the CDDI/FDDI port price is also declining, and it also has a large advantage in terms of transmission distance and security. Therefore, it is a good backbone for large networks. select.
3COM’s main switching products are Linkswitch series and LANplex series; BAY’s main switching products are LattisSwitch2800, BAY stack workgroup, System3O00/5000 (providing some optional switching modules); Cisco’s main switching products are Catalyst 1000/2000/3000/ 5000 series.
The product forms of the three companies all seem to have similarities, and the prices of the products are relatively close. In addition to the specific needs of the network environment in the design (emphasizing the reasonable matching of ports), it is also necessary to consider the whole, such as network management and network. Application, etc. With the development and maturity of ATM technology and the intensification of market competition, the price of frame switches will fall further, and it will become an important solution for work networking.