GS305EP

[WiseOldElf]

Hello,

First timer here, so please be gentle !

This switch (GS305EP) - i have read a lot of the technical documents, but wanted to be absolutely sure before i bought it...

If I am understanding everthing properly - it's POE+, so 802.3at, hence it's going to be able to supply 13w per port (up to the device limit) and also 44v per port ?

thanks

WiseOldElf 

[schumaku · Accepted solution]

Best information source is always the data sheet - Data Sheet | GS305EP, GS305EPP, GS308EP, GS308EPP, GS316EP, GS316EPP 

---

@WiseOldElf wrote:

it's POE+, so 802.3at, hence it's going to be able to supply 13w per port (up to the device limit)

---

PoE+ is 802.3at, while PoE is 802.3af. 

802.3af says guaranteed power available at powered device (PD) 12.95 W, power available on the power source equipment (PSE, the switch) 15.4 W.

802.3at says guaranteed power available at powered device (PD) 25,5 W, power available on the power source equipment (PSE, the switch) 30 W.

Virtually all 802.3at PSE are backward compatible to 802.3af.

Strict PSE are reserving the power requested, commonly the PD does request a certain power class, which does define the power reserved and guaranteed. Class levels (1-3) for 802.3af, class levels (1-4) for 802.3af. Typically this is strict, the power is reserved, lower priority PoE ports might not provide power if the budget is exceeded.

Newer PD and PSE make use of LLDP, link layer discovery protocol, where the PD can request the power in 0.1 W increments.

---

@WiseOldElf wrote:

and also 44v per port ?

---

On standard compliant active PoE, you don't have to care about the voltage provided. The standard does define what is provided and acceptable. In active PoE, the PD does request power, if this is within the specs, power is made available on the PSE. If not, there is no voltage. PoE devices stating a certain voltage in the specs and odd power numbers like 15 W are suspicious to me, this might be so called passive PoE. 

FMI https://en.wikipedia.org/wiki/Power_over_Ethernet

[schumaku · Accepted solution]

Best information source is always the data sheet - Data Sheet | GS305EP, GS305EPP, GS308EP, GS308EPP, GS316EP, GS316EPP 

---

@WiseOldElf wrote:

it's POE+, so 802.3at, hence it's going to be able to supply 13w per port (up to the device limit)

---

PoE+ is 802.3at, while PoE is 802.3af. 

802.3af says guaranteed power available at powered device (PD) 12.95 W, power available on the power source equipment (PSE, the switch) 15.4 W.

802.3at says guaranteed power available at powered device (PD) 25,5 W, power available on the power source equipment (PSE, the switch) 30 W.

Virtually all 802.3at PSE are backward compatible to 802.3af.

Strict PSE are reserving the power requested, commonly the PD does request a certain power class, which does define the power reserved and guaranteed. Class levels (1-3) for 802.3af, class levels (1-4) for 802.3af. Typically this is strict, the power is reserved, lower priority PoE ports might not provide power if the budget is exceeded.

Newer PD and PSE make use of LLDP, link layer discovery protocol, where the PD can request the power in 0.1 W increments.

---

@WiseOldElf wrote:

and also 44v per port ?

---

On standard compliant active PoE, you don't have to care about the voltage provided. The standard does define what is provided and acceptable. In active PoE, the PD does request power, if this is within the specs, power is made available on the PSE. If not, there is no voltage. PoE devices stating a certain voltage in the specs and odd power numbers like 15 W are suspicious to me, this might be so called passive PoE. 

FMI https://en.wikipedia.org/wiki/Power_over_Ethernet

[WiseOldElf]

many thanks for your prompt and thorough reply; i do appreciate it.

i had read the data sheet before i posted, but felt it was worth double-double-checking before i spent any money 🙂