Why not use Link Aggregation to extend your Network?
Link Aggregation Architecture Diagram:
Extending your network using Link Aggregation:
Link Aggregation and its advantages:
Link Aggregation is a very useful method to combine multiple links to form a single (bigger) link. It can be either two links from two ports of each switch connecting to another switch as shown in the above diagram, or multiple links from multiple ports. Similarly, two (or more) links from two (or more) ports from a server can also connect to two (or more) switch ports to form a bigger link.
The main advantage of doing this is the higher capacity obtained from each group of aggregated links. For example, if two 1 GE ports from two switches connect to each other using Link Aggregation, we get a single virtual 2 GE port. In case you want to upgrade the network backbone, this method of connecting the switches using Link Aggregation not only uses the existing switches, but also gives a 2x,3x… higher backbone throughput. Compare this with replacing all the switches with newer ones and getting a 10x increase in throughput which may not be fully utilized.
More importantly, as multiple links connect from one switch to another using Link Aggregation, if one link fails, the traffic would continue to flow through the other link(s). So, this gives cable level redundancy for all the interconnections made using Link Aggregation protocol. You can Link Aggregate two copper links (or) two single more fiber links (or) two multi mode fiber links (a combination of copper/ fiber is not allowed though). All the aggregated links need to operate at the same speed (100 Mbps or 1GE or 10GE).
Link Aggregation can also do load balancing among the various links in the Link Aggregation Group. So, the traffic is split evenly between the various links which ensures its effective utilization.
With Link Aggregation, each individual link can be configured to carry a separate class of traffic (like voice) if desired, using QoS parameters. Each individual link can also be configured to carry traffic from particular node(s)/server(s). This enables a separate un-congested route for important / latency sensitive applications/ nodes.
Even Switches from different vendors can be used to form a Link Aggregation Group as long as they support IEEE Standards – 802.3ad/ 802.1AX.
Link Aggregation can also be applied in virtual server environments, where it is possible to connect ports in a single virtual switch to multiple physical Ethernet adapters thereby giving a higher throughput (than connecting just a single adapter). Even load balancing is supported in such configurations by certain server virtualization solutions.
LACP (Link Aggregation Control Protocol):
Dynamic Link Aggregation uses LACP (Link Aggregation Control Protocol) which enables the switches to know which switches connected to them are configured for interoperability using Link Aggregation. LACP can exchange configuration information among cooperating systems and automatically detect the presence and capabilities of other Link Aggregation capable devices.
LACP makes it easy to identify any cabling or configuration mistakes while configuring Link Aggregation between two devices. It is also possible to specify which links in a system can be aggregated, using the Link Aggregation Control Protocol (LACP).
Limitations of Link Aggregation:
Link Aggregation occupies additional switch ports which can otherwise be used to connect the nodes/systems.
Link Aggregation accounts for only cabling failures but does not give redundancy in the case of switch failures (although some proprietary vendor implementations can achieve this).
Link Aggregation cannot itself prevent any loops from occurring in the network.
There is a maximum limit to the number of links in each Link Aggregation Group (LAG) and it is generally specified by the vendor (generally eight).
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