Re: [HSSG] Reach Objectives
At 08:08 AM 9/3/2006 , Trowbridge, Stephen J (Steve) wrote:
is all well and good to say (quoting Geoff)
"Preambles are not payload
Interpacket gaps are not payload."
but it is clear that some
customers don't like it if you have to fiddle with their preambles or
interframe gaps to go between LAN and WAN.
Going between WAN and LAN is not any different than going between WAN and
WAN or going between LAN and LAN. It is done with a bridge, a device of
two or more MACs whose connection is standardized by 802.1
(Unless you want us to spec a repeater for this project. We have done
repeaters before in 802.3. They have always been regenerative and have
always generated a fresh preamble.)
The interframe gap exists precisely "to fiddle with". They are
a core reason why Ethernet is different from and cheaper than SDH. At the
system level (without regard to whether or not it is true at the physical
layer level) each Ethernet packet is a different and asynchronous event.
This lack of history and saved state between packets at layer 2 is a
major source of both the robustness and economy of Ethernet
It is the job of 802.3 to spec building blocks for the layered
architecture of IEEE 802. In that context, it is and always has been the
job of the 802.3 MAC to strip off the preamble upon reception and to
generate a new preamble upon transmission. 802 compliant bridges have no
provision for forwarding packet information other than:
To do what you suggest would be a significant change to the 802.3 MAC and
the 802 architecture.
I strongly believe (and will argue) that any such change is outside the
scope of the "Higher Speed Study Group". It has nothing to do
Customers who want end-to-end unpacketized bit-for-bit transmission (as
opposed to packet integrity) don't want Ethernet. (which is perfectly OK
Having said that, you are welcome to test the interest of 802.3 and 802
for such a change by putting together a call for interest specifically
addressing this topic.