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With the explosive growth of data traffic, the standards of data center construction are constantly improving. Obviously, ordinary switches can no longer meet the needs of data centers. The data center switch has the technical characteristics of high capacity, large cache, virtualization and two-layer TRILL, which can meet the demand. What key parameters should a data center switch have?
Port line speed forwarding: At present, port line speed forwarding is the most basic requirement of data center switches, and the new backplane technology can also meet it. Data center switch is an important part of data center, and it is an indispensable equipment to realize information interaction between data center and the outside world. From its appearance to the present, the data center has developed to the fourth generation, and the switches in the data center are constantly improving. Although there are many new functions in the field of data center, such as FCoE, TRILL, EVI, XVLAN, SPB, etc. The basic parameters still determine the performance and quality of the switch. The basic function of a switch is switching, so switching performance is still the most critical parameter of the switch. In addition to switching performance requirements, data center switches have many other technical parameters. Let's talk about the key parameters of the data center switch for reference when purchasing, using and expanding the data center network.
Data centers are also divided into box switches and rack switches. A box switch is a switch with a fixed number of ports, sometimes with a few expansion slots. Rack switch is a slot switch, which has good scalability and can support different network types and networks with higher port density. Generally, box switches are used in the access layer of data centers. Some box switches only have two-layer functions, while others support three-layer functions, with the second layer as the main one. Rack switches will be used for data center convergence and core exits. Compared with box switches, rack switches have three layers of functions, and need to pay attention to more key parameters.
This network device is called a switch because it has a powerful switching function. Then the main parameters to measure the switching performance of the switch are backplane bandwidth, port density and switching capacity.
Backplane bandwidth is the maximum data throughput between switch interface processor and data bus. The higher the bandwidth of the backplane, the stronger the ability to process data. Backplane bandwidth is a technical parameter of rack switch, and there is generally no concept of backplane bandwidth for box switch. Generally, the bandwidth of backplane varies from several Gbps to several hundred Gbps. The higher the bandwidth of backplane, the better, as long as it meets the port line speed forwarding. Too high design will cause cost waste. The early backplane technology was not high enough to meet all the equipment that could not reach the full line speed. The calculation of backplane bandwidth is related to the internal implementation, such as how many slots can provide as much bandwidth as possible for each slot, so the backplane bandwidth is obtained. For switches that can forward at line speed, the bandwidth calculation method of backplane is simple: number of ports * corresponding port rate *2 (full duplex mode). Of course, the backplane can also be designed in redundant mode, which can provide more backplane bandwidth, so that there are multiple backplane channels between slots for forwarding, and once some problems occur, services will be automatically switched to achieve the purpose of redundant backup. Now the bandwidth of the high-end switch backplane in the data center is T-class.
Port density is a key parameter of data center switch, which represents the forwarding ability of the switch. For example, a box switch can provide 48 10Gigabit ports, a rack switch can provide 24 40G cards, and a rack switch can provide 18 slots. The greater the port density, the stronger the forwarding ability of this device, and the higher the port rate, which means the stronger the processing performance of this device. With the popularization of 40G/ 100G ports, data center switches can provide 8-port 100G cards and 24-port 40G card rack switches, and a single slot can approach1t. In the future, with the improvement of optical module technology, optical modules will become smaller and smaller, and the density of 100G ports provided by a single slot will be higher. Nowadays, rack switches with 480 Gigabit ports provided by a single slot have become popular. Due to the limitation of data center cabinet size, the width of rack switch can no longer be widened, so the current provision of 480 Gigabit ports has reached the limit. In addition, the more types of modules that can be supported, the more practical the equipment will be, and it can be applied to different network environments, such as LAN interface, WAN interface, ATM interface, etc. The richer the port bandwidth types, the better, that is, supporting 40G, 100G high-speed ports and 100m, gigabit low-speed ports, that is, supporting XFP and SFP, SFP+, CFP and other optical interface types. These are important considerations for switches.
The switches in the data center are basically based on Layer 2 and Layer 3 forwarding, so the capacity of forwarding items in Layer 2 and Layer 3 basically represents the number of users that this device can carry. At present, the switch can basically reach: Layer 2 MAC address table entry is 32K, which means that the switch can bring up to 30,000 Layer 2 user addresses, and Layer 3 routing table entry is 16K, which means that the switch can learn up to 10000 routes. Nowadays, the specifications of switches are getting bigger and bigger, and the MAC address and IP routing can basically exceed 128K, or even reach 1M, so that data centers can be expanded and used at will without worrying about the capabilities of network equipment. Another specification is also very important for switches, which is ACL, that is, access control list. Through ACL, service deployment can be flexibly realized, network attacks can be limited, and the switch can work more flexibly. Generally, the ACL specifications of switches using commercial chips are not high (below 10K), and there are many restrictions on their use. For example, Cisco uses its own chip. It can be said that the ACL specification is very large, and it can provide the ACL specification of 100 K.
The management function of data center switches refers to how switches control users' access to switches and how many switches users can control. The management ability of the switch is reflected in the parameters of CPU and memory. Considering the cost, general switches will not use CPU with too fast processing speed. The CPU of the switch mainly completes equipment management, monitoring and three-layer list learning. The real data forwarding is not done by CPU, so there is no need for a CPU that runs too fast. With the lower and lower cost of CPU, the CPU of the switch is also developing in a higher and higher direction. At present, the CPU frequency of general high-end switches is above 1000MHz. Memory is the same, from 64M to 256M, 1G and so on. There are even switches with 5G super memory. These performance parameters are also an important embodiment of switch performance.
Since it is a data center switch, it must have some characteristics of the data center itself. In recent years, new technologies in data centers have emerged one after another. Virtualization, XVLAN, TRILL, SDN, EVI, SPB, FCOE and other technologies are unique to the data center. For example, the virtualization technology of one virtual machine and multiple virtual machines, some box switches can even provide 10 devices to be virtualized into one device, while some rack switches can provide more than 10 independent devices to be virtualized into one device. Data center switches should be able to deploy these new technologies in order to play a better role in future data centers.
Switches in data centers have many equipment parameters, and these parameters introduced in this paper are the most important and key parameters. These parameters can often represent the comprehensive ability of this equipment, which we should seriously study and pay attention to when purchasing equipment, expanding data center and using it. Each parameter will affect the performance, function and different integration characteristics of the switch. ;