Subject: Use Ethernet preamble to perform a frame's classification and a switching optimization

From: "Daniele Giordano" <[email-masked]>
Date: Fri, 18 May 2007 22:33:04 +0200

802.3 Ethernet preamble is composed of 8 byte (7 byte for synchronization
and 1 byte for SFD).
These 64 bit doesn't carry any type of information. Why don't use 3 bit to
obtain frame's classification with values similar to IP Precedence?

Now, only 802.11q standard has a "QoS" mechanism implemented with 802.1p
(Cos) but this type of frame is not supported from a large number of
devices.
e.g. A switch, which receive a Ethernet frame from a PC, convert it in a
802.1q frame and perform an IP packet inspection to read ToS or DSCP value
and write this value in the CoS field; so the frame is sent in an output
queue.

Using preamble's bit a switch can know the frame's priority before of the
switching process and it doesn't use resources to perform IP packet
inspection.
In this way the switch can change its switching modality with the priority
value.
e.g.  preamble with normal priority ---> switch engine: store & forward
       preamble with high priority ----> switch engine: cut through

 What's your opinion about this idea.
Thanks.

_______________________________________________
Ietf mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/ietf