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Roy,
From the point of view of a valid, standards-based objection, I'd have to agree. I don't think there has been a valid, standards-based objection to or reason for a non-modulo 10 MAC data rate. From a pure standards-based reasoning, there is no way to select between 9.58464 or 10 Gb/s for the MAC/PLS data rate. That's why other things like history, market trends, manufacturer's desires, etc. come into play.
What I find interesting it that there seems to be a belief that setting the MAC/PLS rate objective to be 10 Gb/s prevents using OC-192 equipment. This is simply not true. The GbE standards development had an objective of 1 Gb/s at MAC/PLS interface, but that includes packets and IPGs. The MAC is capable transmitting and receiving data at an instantaneous data rate of 1 Gb/s, but the true packet data rate (or throughput) is less due to the IPG. An objective of 10 Gb/s is to say that the interface is capable of transmitting and receiving at an instantaneous data rate of 10 Gb/s, but the throughput is up to the HSSG to decide.
As for the use of OC-192 equipment, nothing is written in stone until it's in the standard, but we have a distance objective of 40 km. If OC-192 equipment satisfies the objectives of the PAR and 5 criteria, then the standard will be written to ensure correct operation with that equipment.
Thanks,
Brad
Brad Booth
bbooth@xxxxxxxxxx
Level One Communications, Austin Design Center
(512) 407-2135 office
(512) 589-4438 cellular
-----Original Message-----
From: Roy Bynum [SMTP:RBYNUM/0004245935@xxxxxxxxxxx]
Sent: Monday, August 02, 1999 10:06 AM
To: IEEE HSSG
Subject: Data rate standards vs internal switching standards
I have been to reading objections to using something other
than the traditional modulo 10 MAC data rate. I have begun to realize
that a lot of the objections are based on some unknown "standard" of
switching data between ports. As far as I know, there are no standards
within 802 that define how a vendor switches data from one port to
another. As far as I know there are no standards of how vendors clock
data, or even maintain data integrity within a switch. As far as I
know there are no standards on how a vendor will clock data from a
framing buffer into the MAC interface only the rate that it is done
at.
Some one should be able to verify that other than specified MAC and
signaling clock rate of the 802.3 interfaces, there are no clocking
or data rate standards of how data is handled within a switch.
If I am correct, there are no standards for how the data is clocked
within a switch. All objections based on linking older interface data
rate standards would only apply to a switch that is fully loaded, actually
overloaded. Relative to that reality, overloading an output MAC at
one data rate is no different from overloading one at another rate.
As such, all objections to something other than the traditional modulo
10 are based on an assumed standard that does not exist or they are
based on an operational implementation inadequacy. The other side of
that issue is the leveraging of technology that already exists and has
several years of operational experience using a data rate at something
other than the traditional modulo 10.
The real problem is in realizing that 802.3 is no longer limited to a
shared segment environment. Many will say that they know that 802.3
has not been limited to a shared segment for years. For some reason,
they are still writing as if 10GbE will using shared hubs and segments.
802.3 has been progressing more an more away from the original concept
of a LAN for many years. The very concept of a LAN has changed from 20
years ago. The boundary have been blurring more and more over time.
With full duplex, optical, GbE, the 802.3 WG sanctioned, by default,
the entry of 802.3 into the long distance data environment. Long
distance data has traditionally been considered WAN services. The 802.3
WG ignored the operational support distinctions between traditional
LAN and WAN environments. With 10GbE that operational support
distinction can no longer be ignored. The existing transport and
support infrastructure for long distance data as well as that
technology should also not be ignored.
I have yet to see a valid, standards based, objection to a non-modulo
10 MAC data rate. I have seen several valid advocations of a
MAC rate other than modulo 10 that are based on long distance data
technology standards.
Thank you,
Roy Bynum
MCI WorldCom