Wireless Access

Hi community,

 

Just a little doubt about the new Aruba APs that support Smart Rate technology, such as the 330 series. These APs have a Smart Rate uplink port that scales up to 5Gbps. Supossing the connected switch port and the cabling also support a Smart Rate of 5Gbps, will the AP produce such a high volume of traffic? Or this AP should have a lot of users connected with high bandwitdh consuming applications in order to reach 2.5-5Gbps?

Furthermore, the datasheet says:

 

With a maximum concurrent data rate of 1,733 Mbps in the
5 GHz band and 600 Mbps in the 2.4 GHz band (for an
aggregate peak data rate of 2.3Gbps)

 

So, if the ideal peak data rate is 2.3Gbps, why do they support a 5Gbps Smart Rate port ? Where does it make sense to place these kind of APs?

 

Regards,

Julián   

They support a 5gig port because there is no such thing as a 2.3 gig port.

Julian,

 

You are right that 5Gbps Ethernet is hard to justify on the AP-335 given the maximum combined wireless datarate.

But 2.5Gbps (also supported by that port) does, assuming the AP is configured for max performance.

The 5Gbps speed is disabled by default.

Note also that Ethernet speeds are full-duplex, while Wi-Fi is half-duplex, so in a typical use-case there will be plenty of buffer capacity on the wired side. 

Hi Onno,

Yes, that's exactly what I mean. 5G doesn't make sense, but 2.5 does (and also supported). So it would have been better just to place a only 2.5G capable port such as in the 340/510 series (and I guess is cheaper). So I suppose the 5G port in the 330 series is just marketing.

Regards,
Julian

I believe there are no 2.5 Gbps only Ethernet ports. It is like if you only need 300 Mbps, the first step above 100 Mbps is 1 Gbps. The ethernet port is a smart rate port. You can check this video, which explains it from the switch side, to see how that works and switch and device can work on a lower speed if cables are long or bad.

Hi Herman,

 

That's a good video, thanks for the link. But anyway I think for 330 and 510 AP series just the capability of the Smart Rate port doesn't support 5 Gbps, just 2.5 Gbps. From the AP-330 series datasheet:

 

One HPE SmartRate port (RJ-45, maximum negotiated
speed 2.5 Gbps)
--Auto-sensing link speed (100/1000/2500BASE-T)
and MDI/MDX

 

Regards,

Julián

It does 2.5 Gbps on auto-negotiated, if your cables are good enough you can set it fixed to 5 Gbps, just not negotiated. As you said, there is no real use case other than that it looks nice if you check the port speeds.

 

You can even debate if you will ever hit the 2 Gbps capacity (1G in, 1G out full-duplex) on a standard Gigabit port in practice. And even if you hit that limit, if users will notice. With Smart Rate on the AP, you can even in that theoretical situation where you hit the 1G limit in one direction, still handle all the traffic.

Hi,

 

1. Well, maybe I don't understand very well. But I have this point of view: you can set the switch to 5 Gbps not negotiated, but if the AP support up to 2.5 Gbps, it will advertise just 1G and 2.5G, not 5G, so they will end up in 2.5G.

 

2. That's another point. Even if the AP reach its full capacity of 2.3 Gbps, how much of this will reach the wired part? A lot of this traffic is wireless overhead and will remain in the air, and a lot of the Smart Rate port bandwitdh will be "empty". And we are talking about the ideal case of maximum performance, in a practical case, I don't know how useful is to have Smart Rate ports in APs. However, it makes a lot of sense in switches.

 

Regards,

Julián

I now see, the AP 330 series support up to 5Gbps, the 340 up to 2.5Gbps.

Onno may be able to bring clarity.

 

For the 330, you can select 5Gbps in the AP Ethernet Link profile:

That's correct, the 330 Series supports up to 5Gbps, while the 340 and 510 series are limited to 2.5Gbps. Those are hard limites of the Ethernet PHYs we use.

Note that on the 330, 5Gbps is disabled by default, and in order to enable it, you cannot add it to the range of rates that is negotiated under "auto", but you have to set it to 5000 "hard". Not needed, not recommended, and generally not a good idea.

Be aware that when using CAT5E cabling, the max length (100) drops when operating at 5Gbps. There are no such issues/restrictions when on 2.5Gbps.

As mentioned, this was added purely for marketing reasons, and to avoid getting locked out from competitor-driven RFPs.