Trunking vs. Stacking

[Think]

Some switches are stackable, others have (so-called) uplink ports, and some have both. I have googled around quite a bit, and my understanding is that the main benefit of stacking is the ease of administration (multiple switches administered as a single one, with possibilities for failover, etc.). In addition, some higher priced switches, e.g. Cisco's StackWise protocol, offer more bandwidth for their stacking protocol than via trunking. However, for most switches (including Cisco's smaller SG switches) speed/bandwidth/latency is unaffected by stacking.

Did I get that right? Or is there any further benefit in stacking switches? Obviously, stackable switches come with a premium, which might be difficult to justify in a home setup.

 

[Thecal714]

Sounds right. AFAIK, the point of stacking is to increase the number of ports in a single "switch". Ideally, you'd want a higher-bandwidth stacking connection, as you want it to be as close to backplane speed as possible. The stacking in SG-series and similar is just for easy of configuration/management.

 

[blood]

It's not just high end kit that sometimes offers faster speeds on stacking ports - things like Netgear GSM7328s and family offer CX4 interfaces that can do 12gbps when stacked, but only 10gbps when used regularly. Of course both sides of the stacking link need to use the same (proprietary) protocol in order to take advantage of the additional speed, whereas changing their mode from stacking to ethernet allows them to interoperate with other gear.

One difference between uplinks and other interfaces in addition to often having a higher datarate is that generally uplink ports are not oversubscribed and are thus able to operate at line rate bidirectionally where other interfaces might not be able to do so. This is a function of the internal forwarding bandwidth of the switch chips, as sometimes a set of interfaces will utilize the same switch chip which doesn't have enough oomph to run them all at full speed at the same time. This is less and less an issue as switches that offer line rate on every interface are not rare these days, but it wasn't always the case.

There might be an additional benefit for stacking in that you can form a ring topology and take advantage of all of the links' bandwidth as well as redundant paths but this probably depends on a given vendor's implementation. You could certainly achieve a ring using standard ethernet by employing a flavor of spanning tree, as well as being able to hash flows across different links using link aggregation, but it might be simpler to achieve these benefits with stacking. STP and LACP aren't that hard though.

One additional advantage of stacking is that some vendors allow for splitting link aggregation groups across units which while a more complicated topology in theory can be more resilient. The other end of that bundle will just see a single logical switch that it's talking to, but if one of them dies the LAG can continue to function in a degraded manner.