Switch basics: distributed link aggregation technology

Computer Store News Although the IRF system is presented as a whole, it does not restrict users from operating on a particular unit. As an example, you can configure and manage all the aggregated links in any unit of the system to check the status of all aggregation groups and aggregation ports. By connecting to any unit of the system through CONSOLE, SNMP, TELNET or WEB, users can create or delete aggregation groups, display aggregate information, and enter specific port mode to modify or display their aggregation parameters. In this process, the DLA automatically passes the user command to the unit where the port is located. The unit receiving the command obtains the execution result and provides it to the user. The distributed aggregation technology further eliminates the problem of single point of failure of the device and improves the availability of the link. Since the aggregated members can come from different devices, even if some units in the system fail, other normal working units will continue to control and maintain the state of the remaining ports, and the aggregated links will not be completely interrupted. This is significant for core switching systems and networks of high quality services. Take Figure 4 below as an example. There is an aggregate link between the IRF system X1 and X2. This link consists of physical connections Link1~Link4 and is responsible for communication between LAN1 and LAN2. If switch X11 fails in X1, Link1 and Link2 are unavailable, Link3 and Link4 are not affected, and can still be aggregated to send and receive data. Thereafter, if X22 in X2 also fails, X1 and X2 can still be connected at least through Link3. IRF devices can be viewed as "scalable" (scalable) switches. Users can use a single IRF switch network or add one by one to enhance the performance of network devices as needed. At the same time, this high-performance stacking switch can also be split. After splitting, each unit is restored to become an independent working switching device. The above processes are called merge and split, respectively. If the two systems in the previous merge have created the same aggregation link, the IRF requires that the aggregation members must join the same group, that is, the aggregation group is also merged. After the combination, the units work together to match the configuration parameters globally, assign the aggregation group number, add the port to the corresponding group, and recalculate and set the port status. Similarly, if the same aggregation group members are distributed on different units before the split, they will remain in the same type of aggregation group of the same name created after the split. The DLA ensures that each unit retains the current aggregate configuration, removes the left port from the group, and then calculates the state of the remaining ports. This feature maximizes the user's aggregation configuration. Moreover, when the stack link fault causes the system to be split, this feature allows the IRF system to maintain the existing aggregated link as much as possible, reducing the data transmission loss caused by the fault. Switch Basics: Multiple Aggregation Types DLA implements three types of aggregation methods: manual, static, and dynamic. Manual and static aggregation groups are created or deleted by user commands, and members in the group are also specified by the user. After the creation, the system cannot automatically delete the aggregation group or change the aggregation member, but it needs to calculate and select the working status of the members in the group. Whether an aggregated member becomes a working link depends on its configuration parameters, and not all members can participate in data forwarding. Manual and static aggregation are mainly different in the way of aggregation control. The LACP protocol is not enabled on the manual aggregation link. The configuration information is not exchanged with the peer system. Therefore, the aggregation control determines the working link only according to the configuration of the system. This type of aggregation control is more common on older switching devices. The static aggregation group is different. Although the aggregation member is specified by the user, the DLA automatically starts the LACP protocol on the static link. If the peer system also enables LACP, both devices can exchange aggregated information for use by the aggregation control module. Dynamic aggregation control fully complies with the LACP protocol and achieves the goal of automatic configuration of aggregated links in the IEEE802.3ad standard. The user only needs to select the dynamic mode for the port, and the system can automatically aggregate the parameters matching ports and set their working status. In the dynamic aggregation mode, the system sends LACP packets to each other and exchanges state information to maintain aggregation. If the parameter or status changes, the link will automatically join the original aggregation group and join another suitable group. The above three polymerization modes provide good polymerization compatibility for the IRF system. The system can not only be interconnected with devices that do not support link aggregation, but also with devices that are implemented in a variety of different aggregations. Users can flexibly select the aggregation type according to the actual network environment to obtain high-performance and highly reliable links.

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