On many of the powerline ethernet adapters, they claim high speeds of 500 Mbps, however, I've noticed that the actual jack on the device is only 10/100 Mbps speed. For reference - look at the specs: http://www.tp-link.us/products/details/?categoryid=1658&model=TL-PA4010KIT#spec
The actual interface is 10/100 Mbps. How is it possible to achieve 500 Mbps speeds when the actual jack is a much slower speed?
There are different factors to take into account.
The adapter comes with two interfaces. One side is powerline, the other is LAN. Both are independant of each other. Powerline is capable of a PHY rate of 500 Mbps. LAN is able to send 100 Mbps.
When comparing the data rates, take care. Let's assume you want to send UDP traffic with a given packet size. You will not be able to send 100 Mbps payload, but 93 Mbps, the rest is overhead. When sending the same amount of traffic over powerline you will need about the double PHY rate, so 180-190 Mbps.
In your case it looks like >300 Mbps of the powerline connection will not be used. This is true. You can only send over powerline what you received over LAN. So the slowest connection dictates the overall speed. Yet you will only see the 300 Mbps waste in an optimal scenario. In a real world scenario you will never see 500 Mbps on your powerline connection. It is much more likely that you will end up with 100-200 Mbps PHY rate. Taking this real world PHY rate you see that LAN might deliver more data than the adapter will be able to forward over powerline.
If your suggestion is building an adapter with 1 Gbps LAN, you could also argue the other way round: I have a 1 Gbps LAN, but powerline only allows 500 Mbps, why don't they build-in a faster powerline? Most times you will end up with one end being faster then the other. In the case of the powerline adapters you see a choice that favours price and practical use over marketing bigger-better-faster-values.
Shhhhh...don't tell the masses. My understanding is that this is simply a lie & I wish they couldn't do this. Per some enlightening amazon reviews maybe this is the speed between the two power-line adapter devices (the house/AC wiring), but indeed its crippled coming out of the actual physical interface port. Most people don't care too much since they were more crippled in the first place & they generally get their maximum internet speed (which is well below 100Mbps in USA usually) which is usually their desire
It's not uncommon for networking devices to list the signaling speeds of their ports individually without regard for whether the bandwidth offered by the other ports (or the embedded CPU controlling it all) can successfully sustain data flows at the speeds afforded by the fastest port.
It's more an indication that it can interoperate with other devices using those technologies, and can send single packets at the signaling rate specified, rather than a promise of sustained throughput.
Gigabit Ethernet ports started showing up on motherboards as early as 1999 (probably earlier) even though it would still be years before CPUs could really transfer 1Gbps of data in either direction through that port. I'm sure there are plenty of cheap networking devices on the market today that have Gigabit Ethernet ports yet can't sustain a 1Gbps data flow in either direction.
This situation is not unique to networking equipment either. It's common in all I/O technologies. For example, when SATA-III came out, there were plenty of SATA-III hard drives that couldn't do sustained reads or writes at full SATA-III speeds. They could, however, speak the SATA-III protocol with individual messages sent at SATA-III signaling rates. With USB 3.1 "SuperSpeed+" 10Gbps coming out now, I'm sure you'll be able to find plenty of devices that claim to to be USB 3.1 SuperSpeed+ compliant, but can't sustain 10Gbps data flows.
I'm not trying to excuse or rationalize the confusion this causes, I'm just pointing out that this is business as usual for the high-tech industry. Vendors of powerline Ethernet adaptors are not unique in doing this.
