How does message switching fit in this comparison table here?
Are these 4 switching work at different layers in the OSI model?
How does message switching compare with other switching techniques
switching-modes
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You don't mention brand of the switch, any management software, or any configuration (in particular how that interface was previously configured), so I can only answer generically.
Most default switch MAC address tables have a relatively low timeout to age out entries. Just because you are only seeing 19 devices from the same VLAN on a port currently doesn't mean that there aren't other devices that will need to utilize a different VLAN on the trunk.
You say you "guessed that there was a switch connected to that interface." Guessing is a bad way to decide on making changes in a network. This indicates you do not understand the network in enough detail to be making the change and you should spend more time investigating before doing so.
Is that wrong?
Connecting two switches utilizing access ports? Wrong, no. It is considered a best practice to connect two switches with trunk/tagged ports. However, there are circumstances where using access ports is perfectly fine, if not necessary.
There may also be other considerations. For instance, there may be default configuration (or other configuration on the port) that could apply differently to access ports or trunk/tagged ports. For example, if your switches use VTP (or a similar mechanism), VTP only runs over trunk/tagged ports. Another example would be spanning-tree portfast (or similar), which can be applied by default to access ports along with features such as BPDU guard.
Wrong to make a change based on a guess? Yes, absolutely. Unless you have some pressing reason forcing your hand, you shouldn't make decisions in networking based on guesses. You are likely to create issues.
Does that worsen the switching perfomance?
No. There should be no noticeable difference in performance between an access port and trunk port. However, look a couple paragraphs up as there may be configuration that is applied differently to access ports and trunk/tagged ports. This configuration may have some impact on the port operation.
Should I go to talk to the person who manages the other switch to know how he configured the interface connected to the switch that I manage?
Yes and you really should have done so before making the change. When other parties are involved, it is almost always best to reach out to them before making any changes.
Reverse the situation, what if the other person were to make such a change without informing you? Go a bit further and say this disrupted operation on your network in some fashion. Wouldn't you prefer that you had been informed before hand so you wouldn't have to spend time and effort troubleshooting an issue created by someone else?
This seems to assume that queues can have limited number of packets (true enough), but unlimited packet size (not true). The idea that a large message packet size uses fewer places in the queue is true, but it ignores reality that an interface can only serialize the packet bits at a certain speed (bandwidth), so that larger packets take proportionally longer to transmit, stalling the queue for a longer period of time.
The bottleneck is the bandwidth of the interface. If an interface can transmit at a limited speed (true), the number of bits in the queue will be the same, regardless of the packet size. What is true is that the larger message packets will be fewer in the queue, but will still take about the same amount of time as smaller packets to transmit the same amount of data because the interface can only serialize the bits at its fixed speed.
Transmitting 1 Gb through a 100 Mbps interface takes the same amount of time regardless of the packet size. The only thing larger packets gain is eliminating some packet header overhead, but that can be ignored unless the packets are so small that something like the IPv4 20-byte packet header is a substantial percentage of the packet size.
In any case, the real world uses packet switching. Circuit switching, such as the traditional telephone circuit-switching network, is going away in favor of packet switching because packet switching is more flexible, allowing the circuit to be shared more easily and allowing different services, e.g. voice, data, video, etc., to use the same circuit at (relatively) the same time.
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A message could be circuit switched or packet switched. You would probably classify message switching as an application layer construct.
Packet switching can break a large message into smaller packets to be sent, but a message may be small enough to fit into a single packet, too.
A circuit could carry a message over a circuit switched network.
It's kind of like comparing peer-to-peer routing with IP routing. They are not equivalent since one is application layer routing, and the other is layer-3 routing on which the application layer routing may happen.