Rim Semiconductor Company (fka RSMI)

[spokeshave]

louis: Re: Didn't NVEI talk about the TCP packet awhile back (probably over a year ago)...

Maybe, but it is irrelevant. TCP is a layer 3 protocol. The OQAM technology that NVEI claims to have, along with all other xDSL technologies, is a layer 1 (physical layer) technology.

Groovemaster cannot seem to understand this, but it is simple physics. Think of it like this. xDSL technology is analogous to a highway. It has a maximum capacity. The bigger the highway, and the fewer intersections it has, the faster data can be transmitted over it. The highway, then, is like the physical layer in data transmission.

TCP is analogous to a bus. It rides on the highway, but it is not the highway. They are two totally different entities. The TCP bus carries packets of data down the highway. However, the TCP bus has a quirky habit of stopping every mile or so to call its destination, and wait for an answer. It won't start down the highway again until it gets and answer, and if it never gets an answer, it goes back to the start of the highway to begin its journey again.

Making the highway bigger and faster will not change the bus's behavior. It *will* make the bus faster when it is driving, but no matter how fast the highway is, the TCP bus will stop and make the call every mile. No highway technology will change that.

It is a rough analogy, but it illustrates the difference between physical layer technology and a layer 3 protocol like TCP. Latency (or lag) is a layer 3 TCP construct. It will occur no matter what kind of "highway" is used.

I think our guy doing the thesis paper at Cambridge came up with a solution?

Two things. He is not "our guy", and his thesis was on reducing guard interval loss, which is completely different from TCP latency. TCP latency is a result of the the "waiting period" while the recieving party is receiving, interpreting and acknowledging receipt of the data packet.

The guard interval is a short pause sent with each symbol by the physical layer to allow echoes (reflected signals) to settle before another symbol is sent.

Two completely different concepts.