Bandwidth
The bandwidth of a switch is the maximum amount of traffic that it can handle. Specified in gigabits per second.
This parameter directly depends on the number of network ports in the device (excluding Uplink). Actually, even if the bandwidth is not given in the specifications, it can still be calculated using the following formula: the number of ports multiplied by the bandwidth of an individual port and multiplied by two (since both incoming and outgoing traffic are taken into account). For example, a model with 8 Gigabit Ethernet connectors and 2 SFP ports will have a bandwidth of (8*1 + 2*1)*2 = 20 Gbps.
The choice for this indicator is quite obvious: you need to evaluate the expected traffic volumes in the serviced network segment and make sure that the switch's bandwidth will cover it with a margin of at least 10-15% (this will give an additional guarantee in case of emergency situations). At the same time, if you plan to often work at high, close to maximum, loads, it will not hurt to clarify such a characteristic as the internal bandwidth of the switch. It is usually given in a detailed technical description, and if this value is less than the total throughput, serious problems may arise under significant loads.
Gigabit Ethernet
The number of standard Gigabit Ethernet RJ-45 network connectors provided in the design of the switch.
As the name suggests, these connectors provide data transfer rates up to 1 Gbps. Initially, Gigabit Ethernet was considered a professional standard, and even now the real needs for such speeds arise mainly when performing special tasks. Nevertheless, even relatively inexpensive computers are now equipped with gigabit network adapters, not to mention more advanced technology.
As for the number of connectors, it corresponds to the number of network devices that can be connected to the "switch" directly, without the use of additional equipment. In the case of Gigabit Ethernet, the number of connectors up to 10 inclusive is considered relatively small, from 10 to 25 — average, and the presence of more than 25 ports of this type is typical for professional-level models. At the same time, it is worth noting that in some "switches" individual connectors of this type are combined with optical SFP or SFP + (see below). Such connectors are marked "combo" and are taken into account both in the RJ-45 count and in the SFP/SFP+ count.
PoE (output)
The switch supports
the Power over Ethernet function.
This feature allows the switch to supply power to network devices over the same Ethernet cable that transmits data. This reduces the number of wires and simplifies power supply, which is especially convenient if the device is installed in a hard-to-reach place where there is no outlet nearby, and it is difficult to pull an additional cable. An example is an IP surveillance camera installed under the ceiling.
The number of PoE outputs may vary. It should also be borne in mind that when several consumers are connected at the same time, specific power restrictions apply; see "Total PoE Power" for details.
Accordingly, such devices are much more expensive than
switches without PoE.
PoE output power
The PoE power (see above) provided by the switch to each individual PoE output. This indicator allows you to evaluate whether a particular device can be connected to such an output — the power consumption of the load in peak mode should not exceed the output power of the port. There are three standards EEE 802.3af (
PoE, ~15W), IEEE 802.3at (
PoE+, ~30W) and IEEE 802.3bt (
PoE++, ≥40W)
Note that when connecting several PoE devices at the same time, the total PoE power must also be taken into account — see below for more details.
Total PoE power
The total output power provided by the switch when powering devices using the PoE standard (see above).
This indicator usually corresponds to the sum of the powers of all outputs — that is, the power of one PoE port, multiplied by their total number. However, the power limits for one output and for the entire switch are somewhat different: if a load with a power equal to the output power of the power supply on this connector can be connected to a single connector, then the total power consumption of all devices connected via PoE should ideally not exceed 75% of the total power supply — this gives an additional guarantee in case of malfunctions. In fact, this means that all PoE outputs cannot be used “to the fullest” at the same time. For example, if there are two such outputs, and one is loaded at 100%, then the second can be loaded with a maximum of 50% — the total power consumption in this case will be the same 75% of the total output. Therefore,
a large total power is needed when using the device to the maximum.
Supply voltage
The amount of voltage required by the switch for uninterrupted operation. The power supply voltage of network equipment can vary from 5 V to 230 V, which allows you to power compatible devices from either a low-voltage USB socket on your computer or a standard household outlet. Values in the middle assume that the switch is powered by the appropriate power supply.
Power consumption
Power consumed by network equipment during operation. Knowing the indicator of energy consumption, you can, for example, calculate the battery life of equipment from an uninterruptible power supply or choose a suitable “uninterruptible power supply”.
