1, in recent years, the switch products on the new technology
In recent years, the switch has a lot of new technologies, some of which are very useful.
(1), Trunking, Trunking technology can be used without changing the existing network equipment and the original cabling conditions, the switch's multiple low-bandwidth switching ports bundled into a high-bandwidth link, through several ports for link load balancing, to avoid link congestion. A part of the equipment in the backbone part of the company's network can use this technology: network traffic is relatively large, but the actual situation does not allow the use of fiber optic cables, the use of Trunking can be to solve the bottleneck problem in data transmission.
(2), Layer 4 switches developed on the basis of Layer 3 switches. This is a relatively new feature and is described in detail here.
Packets in a network constitute a data stream that can be identified at layers 2, 3, or 4, respectively. Each layer provides more detailed information about that data stream. At layer 2, each packet in the data stream is identified by the MAC address of the source and destination sites. Within the broadcast domain, Layer 2 switching has limited functionality due to the fact that the source and destination MAC addresses are only a rough interpretation of the information in the packet. Layer 2 switches provide inexpensive, high-bandwidth network connectivity, but they cannot provide the necessary control over the backbone data flow. At Layer 3, data flows are identified by source and destination network IP addresses, and the ability to control the flow of data is limited to source and destination address pairs. If a client is using multiple applications on the same server at the same time, the Layer 3 information does not provide a detailed description of each application flow, so that the different data flows cannot be recognized, much less different control rules implemented for each data flow individually.Layer 4 of the OSI model is the transport layer. It is responsible for coordinating communication between the source and destination systems of the network.TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are both located at layer 4. At layer 4, each packet contains information that can be used to uniquely identify the application that sent the packet. This is possible because both TCP and UDP headers contain "port numbers" that identify the application protocol contained in each packet. Combining the port number information in the Layer 4 header with the source-destination information in the Layer 3 header allows for truly precise control. The flow of application-specific conversations can be controlled between the client and the server, and if the switching router is full-featured, all of this can be done at wire speed.
A client/server pair can have several different application sessions open at the same time. Because an enterprise backbone may contain thousands of client/server pairs, a backbone-level switched router must have extremely large table capacity to store up to millions of Layer 4 flows. Layer 3 switches generally do not store information about Layer 4 streams because of the overburdening of the transmit cache and because of the degradation of backbone performance due to table errors from time to time in these routers.
Application layer control has the following advantages:
Application layer quality of service. A true quality-of-service policy caters to all communication traffic in the network by providing wire-speed bandwidth and low latency to all applications. However, when one of the switch's output ports becomes overloaded and its internal buffers are written to full capacity, the quality of service should be required to establish priority rules or "policies" to prioritize network traffic. Switched routers allow quality of service policies to be set for application layer traffic, giving network administrators complete control over bandwidth usage in the network backbone. In Layer 2 and 3 switching, quality of service policies can be applied only to network traffic based on source or destination addresses. Using quality of service policies for Layer 4 application traffic means that priorities can also be set for individual host-to-host application conversations. Network security at the application layer. Traditional routers use security filters and access control lists to achieve secure access to corporate networks and databases. A natural consequence of software-based processing is that once security filters are enabled, this results in a significant drop in router performance, due to the fact that the central processing unit (CPU) has significantly more instructions to execute on each packet. Switched routers eliminate the performance loss associated with security features. A true switching router should provide wire-speed performance when all advanced features, including security, are enabled. In a switched router, packets are processed in a specific ASIC, and because source and destination port information is captured, application layer security and wire-speed performance can be achieved simultaneously. For example, access to company information can be controlled based on a user's application, rather than prohibiting all users from accessing a particular application. This gives network administrators more flexibility and better control over the corporate network, and gives desktops the option to use more applications. Application layer bookkeeping. Management requires measurement. We can't manage a network effectively without measuring network traffic, and by tracking application flows, switched routers dramatically improve measurement, accounting, and performance monitoring capabilities. The accounting information is converted directly into standard per-port RMON/RMON2, eliminating the need for separate external RMON/RMON2 probes. In this way, the switching router always provides wire-speed RMON/RMON2 on all ports (including all feature sets), and managers are able to access RMON/RMON2 statistics directly from the switching router.
This feature should be considered when a company adopts a backbone switch, as it can dramatically improve network performance and allow the company to monitor the flow of information over the network at a granular level and perform application layer accounting of users.
(3), support for multiple routing protocols.
Switched routers have dramatically improved their performance and functionality through hardware measures, but routing processing is still software-based. The original switching routers only supported the Router Information Protocol (RIP), which is generally sufficient for a simple network. However, more complex networks require more sophisticated routing protocols. Switched routers designed for larger networks require the use of the Open Shortest Path First (OSPF) routing protocol. With the growing popularity of applications requiring Multicast support, switched routers should be able to implement a full suite of standards-based Multicast protocols such as Distance Vector Multicast Routing Protocol (DVMRP) and the more scalable Protocol-Independent Multicast Protocol (PIM). For example, Cabletron's SmartSwitchRouter (SSR) provides Layer 2, 3, and 4 switching at gigabits per second on all ports. The high-speed, dedicated ASIC chip forwards packets by looking up packet Layer 2, 3, and 4 headers. In addition, smart-switched routers can realize the functions of bandwidth allocation, troubleshooting, and access control for TCP/IP application data streams by switching packets at Layer 4, and provide detailed traffic statistics and accounting information, application layer QoS policies, and access control capabilities. Many company networks use static routing, which is determined by the fact that the current network topology is star-based. As the network structure becomes more complex, corporate networks will have to consider using dynamic routing protocols to provide redundancy in the network.
(4) Port-based switches have been eliminated and replaced by frame-based switches.
(5) The IEEE802.1X protocol, which is used for user authentication, improves network security. On the switch that supports this protocol, only the users who have passed the system authentication can send and receive information, and the authentication information is kept on the special server, which can be easily queried. The company should try to use switches that support 802.1X and switches that support authentication information transmission near the user end, which can significantly improve the security and manageability of the network.
2, switch selection considerations
Consolidation of the above points, and then take into account the traditional performance parameters of the switch, you can come up with the actual application of the parameters should focus on consideration.
(1), backplane bandwidth, Layer 2/3 switching throughput. This determines the actual performance of the network, no matter how many features of the switch, management is more convenient, if the actual throughput does not go up, the network will only become congested. So these three parameters are the most important. Backplane bandwidth includes the switching bandwidth between switch ports, the data exchange bandwidth between ports and inside the switch and the data exchange bandwidth inside the system. The Layer 2/3 switching throughput rate shows the actual throughput of Layer 2/3 switching, which should be greater than or equal to the switch ∑ (port x port bandwidth).
(2), VLAN type and number, a switch to support more VLAN type and number will be more convenient for network topology design and implementation.
(3), TRUNKING, the current switches support this feature, in the actual application is not too widespread, so I personally believe that as long as the support of this function can be, and does not require the provision of the maximum number of lines of binding.
(4), the number and type of switch ports, different applications have different needs, should be determined on a case-by-case basis.
(5), support for network management protocols and methods. Need to switch to provide more convenient and centralized management.
(6), Qos, 802.1q priority control, 802.1X, 802.3X support, these are the direction of the development of the switch, these features can provide better network traffic control and user management, should consider purchasing a switch that supports these features.
(7), stacking support, when the amount of users to improve, stacking is very important. General company to expand the switch port method for a main switch under each port connected to the sub-switch, so that the maximum data transfer rate of the sub-switch and the main switch is only 100M, greatly affecting the exchange performance, if you can use the stacking mode, its bandwidth in units of G will play a huge role. The main parameters are the number of stacking, stacking mode, stacking bandwidth and so on.
(8) The switch's switch cache and port cache, main memory, and forwarding delay are also important parameters.
(9), For Layer 3 switches, 802.1d production tree is also an important parameter, this feature allows the switch to learn the network structure, which also helps the performance of the network.
(10), Layer 3 switches also have some important parameters, such as whether two/three keep wire-speed forwarding when starting other functions, the size of the routing table, the size of the access control list, the support of routing protocols, the support of multicast protocols, packet filtering methods, and the ability of the machine to expand, etc., are all parameters that are worth considering, and they should be examined according to the actual situation.
Through the above introduction, I believe it can help you to buy a switch. The purchase of switches, in fact, is not so complicated.