The important factors which Layer fourth switches have
Layer fourth switches are widely used in daily life, what are the differences between the fourth layer switch and the second, the three layer switch, and the fourth layer switch than the previous switch advantage in where? The followingdetails.
As mentioned above, the second layer switching equipment is dependent on the MAC addresses and the 802.1Q protocol of VLAN tag information to complete the link layer exchange process, the third layer switching / routing device is the IP address information to the network path selection to complete the transfer process, the fourth layer switching equipment is used in the transport layer data packet information in Baotou to help the information exchange and transmission processing.
That is to say, the specific content description of the fourth layer switch for the exchange of information, is essentially a contained in each IP package of allagreements or process, such as used in the Web transport HTTP for file transfer, FTP, used for terminal communication Telnet, the SSL protocol for secure communications.
So, in a IP network, fourth layers of the widespread use of the exchange agreement, actually is TCP (for connection based on dialogue, such as FTP)and UDP (with no connection to the communication, such as SNMP or SMTPbased on the two protocol). As the Baotou TCP and UDP packet includes not only “the domain port”, it also points out the packets being transmitted is what type of network data.
The use of this related to application specific information (port), can be completed with a large amount of network data and information transmission and exchange related to quality service, the most worthy of note is the following five important application technology, because they are the maintechnology widely used fourth layer switch(such as S5700, S7700).
The packet filter / safety control: in most routers, with fourth layers of information to define filter rule has become the default standard, so there are many routers are used as the packet filter firewall, the firewall can be configured in not only allow or prohibit connecting IP subnets.
Can also control the specified TCP/UDP port communication. And based on the traditional software router is not the same, the main difference in the third layer fourth layer exchange exchange difference, is to filter this ability is realized in the high-speed dedicated chip ASIC, thereby enabling the securitycontrol mechanism can all quickly, greatly improves the packet filtering rate.
Service quality: in the hierarchy of network system, the fourth layers of the TCP/UDP information, often used to build the application level communicationpriority. If there is no fourth layer switching concept, service quality and service level will inevitably subject to the second layer and the third layer provides information, such as MAC address, port, IP subnet or VLAN.
Obviously, in the information communication, hampered due to lack of fourth layers of information, priority emergency applications will be impossible, rapidtransmission which can prevent emergency applications on the network. The fourth layer switch allows the destination address, destination port number(application service) based on the combination of priority, high level of serviceand emergency applications can access network.
The server load balancing: balancing traffic load support provided in multiple servers similar service content between fourth layers of information is crucial.Therefore, the fourth layer switch in the core network system, responsible forthe server load balancing is a very important application.
Load balancing modes supported by the fourth layer switch server, is attached to a load balancing service IP address, consisting of a set by different physical servers, to provide the same service, and define it as a separate virtual server.
This virtual server is a single IP address logical server, user data streamsimply point to the virtual IP address of the server, instead of the real physical server IP address for communication. Only through the exchange performsnetwork address translation (NAT), are not registered IP address of the serverto obtain the ability to access. Another benefit of this virtual server is theserver, hide the actual IP address, can effectively prevent unauthorized access.
The virtual server is based on Application Service (fourth TCP/UDP port number) defined, thus, independent server can be members of virtual server.While the use of fourth layer dialogue marks information, layer fourth switchescan use many load balancing method, converting the communication traffic in the virtual server group, including OSPF, RIP and VRRP protocols and line speed switching and load balancing is consistent.
The fourth layer switch can also be used to be called TRL (Transaction RateLimiting) function provided by the complex mechanism, according to the flow characteristic to curb or reject different types of application services. You can use CRL (Connections Rate Limiting) function, the network administrator to specify the connections are allowed in a given time period, guarantee QoS. or with the aid of SYN-Guard function, to ensure that legitimate connectionsatisfies the TCP protocol can query the network service.
The host: standby link provides redundant connection host standbyconnection port equipment, thus effectively protect the system in the switch failure, this service allows to define the main switch, the virtual server definition, they have the same configuration parameters.
Because the fourth layer switch to share the same MAC address, backupswitch receives and the main unit are the same data. Communication contentwhich makes backup switches to monitor the main switch service. The main switch continued to inform the backup switch fourth
