Guest letter: Layer 4 does work!


David Gabo,

director of technology,

Cabletron Systems

Frenchs Forest, NSW

In reference to the guest column entitled Layer 4 switching is not worth the hype, Network World Today, February 10. (See link to the column at the end of this letter).

I was very amused to read this article by Tony Rybczynski from Nortel. There is either a lack of understanding or a lack of desire to recognise the basic facts. Perhaps it is one of those "bag it if you don't have it" syndromes.

The author talks about Layer 4 and layer 3 in isolation - this really is an oxymoron: a packet transmitted to the network comprises Layers 4, 3, 2 as well as all other bits and pieces like data, checksum, etc.

Layer 4 can not exist on its own. If, for example, we say that a building is an application (Layer-4), it is also true to say that each person going through this building has a name (Layer 3).

Therefore, a reference to Michael from 12 Bridge Street (which is how the packets are made up) will uniquely identify both the application (12 Bridge Street) and the user of this application (Michael), which allows it to switch and prioritise traffic based on a combination of Layer-4 and Layer-3 information embedded in each packet. Layer 4 works!

It is unfortunate that the author does not have Layer 4 products with which he can test the concept, but I would be more then happy to demonstrate the products to anyone who is interested and show how they work.

The other bemusing point made by the author is regarding 802.1p protocols.

On one hand he claims that ". . . most current applications can't do this . . ." That is, use 802.1p protocol to prioritise applications. However, on the other hand he states that ". . . application awareness is built into intelligent Layer 2 switches . . .".

The message this sends out is: "Here is a piece of equipment, which is not useful today and can not solve you business problems just at the moment", and the response it solicits is: "OK, I understand that you don't have a solution, but at least don't ask me to pay any more."

Click here to read the original article:

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